feat: add stature potions and tiny-player launchers

.gitea/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 25
+          cache: gradle
+
+      - name: Validate conventional commits
+        if: github.event_name == 'pull_request'
+        run: |
+          npx -y \
+            -p @commitlint/cli \
+            -p @commitlint/config-conventional \
+            commitlint --from "${{ github.event.pull_request.base.sha }}" --to "${{ github.sha }}" \
+            --extends @commitlint/config-conventional
+
+      - name: Build and test
+        run: ./gradlew clean check jar
+
+      - name: Upload development artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: spigot-heights-${{ github.sha }}
+          path: build/libs/*.jar
+          if-no-files-found: error

.gitea/workflows/release.yml

@@ -0,0 +1,141 @@
+name: Release
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.RELEASE_TOKEN }}
+
+      - name: Set up Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 25
+          cache: gradle
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Build and test before release
+        run: ./gradlew clean check
+
+      - name: Capture previous tag
+        id: previous_tag
+        run: |
+          if git describe --tags --abbrev=0 >/dev/null 2>&1; then
+            echo "value=$(git describe --tags --abbrev=0)" >> "$GITHUB_OUTPUT"
+          else
+            echo "value=" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Run semantic-release
+        env:
+          GITHUB_TOKEN: ${{ secrets.RELEASE_TOKEN }}
+        run: |
+          npx -y \
+            -p semantic-release@24.2.9 \
+            -p @semantic-release/commit-analyzer@13.0.1 \
+            -p @semantic-release/release-notes-generator@14.1.0 \
+            semantic-release \
+            --branches main \
+            --plugins @semantic-release/commit-analyzer,@semantic-release/release-notes-generator
+
+      - name: Capture current tag
+        id: current_tag
+        run: |
+          if git describe --tags --exact-match HEAD >/dev/null 2>&1; then
+            echo "value=$(git describe --tags --exact-match HEAD)" >> "$GITHUB_OUTPUT"
+          else
+            echo "value=" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Resolve release
+        id: release
+        env:
+          PREVIOUS_TAG: ${{ steps.previous_tag.outputs.value }}
+          CURRENT_TAG: ${{ steps.current_tag.outputs.value }}
+        run: |
+          if [ -n "$CURRENT_TAG" ] && [ "$CURRENT_TAG" != "$PREVIOUS_TAG" ]; then
+            echo "created=true" >> "$GITHUB_OUTPUT"
+            echo "tag=$CURRENT_TAG" >> "$GITHUB_OUTPUT"
+            echo "version=${CURRENT_TAG#v}" >> "$GITHUB_OUTPUT"
+          else
+            echo "created=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Build versioned plugin
+        if: steps.release.outputs.created == 'true'
+        env:
+          VERSION: ${{ steps.release.outputs.version }}
+        run: ./gradlew clean jar -PreleaseVersion="$VERSION"
+
+      - name: Upload release workflow artifact
+        if: steps.release.outputs.created == 'true'
+        uses: actions/upload-artifact@v3
+        with:
+          name: spigot-heights-${{ steps.release.outputs.version }}
+          path: build/libs/spigot-heights-${{ steps.release.outputs.version }}.jar
+          if-no-files-found: error
+
+      - name: Create Gitea release and upload plugin
+        if: steps.release.outputs.created == 'true'
+        env:
+          GITEA_TOKEN: ${{ secrets.RELEASE_TOKEN }}
+          GITEA_SERVER_URL: ${{ github.server_url }}
+          REPOSITORY: ${{ github.repository }}
+          TAG: ${{ steps.release.outputs.tag }}
+          VERSION: ${{ steps.release.outputs.version }}
+          PREVIOUS_TAG: ${{ steps.previous_tag.outputs.value }}
+        run: |
+          api_url="${GITEA_SERVER_URL}/api/v1"
+          jar="build/libs/spigot-heights-${VERSION}.jar"
+          export RELEASE_BODY
+          if [ -n "$PREVIOUS_TAG" ]; then
+            RELEASE_BODY=$(git log --pretty='format:- %s (%h)' "${PREVIOUS_TAG}..HEAD")
+          else
+            RELEASE_BODY=$(git log --pretty='format:- %s (%h)' HEAD)
+          fi
+          payload=$(node -e '
+            const payload = {
+              tag_name: process.env.TAG,
+              name: process.env.TAG,
+              body: process.env.RELEASE_BODY,
+              draft: false,
+              prerelease: false
+            };
+            process.stdout.write(JSON.stringify(payload));
+          ')
+          response=$(curl --fail-with-body --silent --show-error \
+            -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            "${api_url}/repos/${REPOSITORY}/releases" \
+            --data "$payload")
+          release_id=$(printf '%s' "$response" | node -e '
+            let input = "";
+            process.stdin.on("data", chunk => input += chunk);
+            process.stdin.on("end", () => {
+              const response = JSON.parse(input);
+              if (!response.id) process.exit(1);
+              process.stdout.write(String(response.id));
+            });
+          ')
+          curl --fail-with-body --silent --show-error \
+            -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/octet-stream" \
+            --data-binary "@${jar}" \
+            "${api_url}/repos/${REPOSITORY}/releases/${release_id}/assets?name=spigot-heights-${VERSION}.jar"

.gitignore

@@ -0,0 +1,7 @@
+.gradle/
+build/
+out/
+.idea/
+*.iml
+*.log
+.DS_Store

AGENTS.md

@@ -0,0 +1,18 @@
+# Spigot Heights Agent Guide
+
+## Canonical design
+
+- `design/` is the canonical OKF v0.1 knowledge bundle.
+- Read relevant user stories before implementation and keep acceptance criteria and `design/log.md` synchronized with verified behavior.
+
+## Engineering
+
+- Target Java 25 and Purpur `26.2.build.2618-stable`.
+- Use Gradle Kotlin DSL and JUnit 5.
+- Prefer small, server-independent domain classes with Bukkit adapters at the boundary.
+- Develop test-first where practical and verify with `./gradlew clean check jar`.
+- Treat custom item identity as persistent metadata; never trust display names.
+- Validate all configuration before enabling gameplay behavior.
+- Persist player data by UUID and use atomic replacement where supported.
+- Keep event handlers on the server thread and avoid unnecessary work on player movement.
+- Use conventional commits in the form `type(scope): description`.

README.md

@@ -0,0 +1,67 @@
+# Spigot Heights
+
+A Purpur 26.2 plugin adding craftable player-scaling potions and dispenser launch tubes for tiny players.
+
+Approved behavior is specified in the [OKF design bundle](design/index.md).
+
+## Requirements
+
+- Purpur 26.2 build 2618
+- Java 25 or newer
+
+## Potions
+
+### Potion of Shifting Stature
+
+```text
+Amethyst Shard | Chorus Fruit   | Amethyst Shard
+Amethyst Shard | Awkward Potion | Amethyst Shard
+Amethyst Shard | Chorus Fruit   | Amethyst Shard
+```
+
+Drinking it chooses a random configured scale in `0.1` increments.
+
+### Potion of Growth
+
+```text
+Gold Ingot | Amethyst Shard             | Gold Ingot
+Amethyst   | Potion of Shifting Stature | Amethyst
+Gold Ingot | Rabbit's Foot              | Gold Ingot
+```
+
+### Potion of Diminution
+
+Use the Growth recipe with a Fermented Spider Eye instead of the Rabbit's Foot. Growth and Diminution adjust scale by one configured step and clamp at the limits.
+
+## Tiny-player launchers
+
+A player below the configured scale threshold can walk onto a hopper whose output points into a dispenser. If the block in front of that dispenser is passable, the player is moved there and launched in the direction the dispenser faces. The launcher does not require redstone.
+
+## Configuration
+
+Defaults are in `src/main/resources/config.yml`:
+
+```yaml
+height:
+  minimum: 0.4
+  maximum: 2.0
+  adjustment-step: 0.1
+launcher:
+  maximum-player-scale-exclusive: 0.5
+  speed: 1.5
+  cooldown-ticks: 20
+```
+
+Player scales are stored by UUID in `plugins/SpigotHeights/state.yml`.
+
+## Build
+
+```bash
+./gradlew clean check jar
+```
+
+The plugin JAR is written to `build/libs/`.
+
+## Releases
+
+Gitea Actions checks pushes and pull requests and stores a development JAR. Pull requests validate conventional commits. Main-branch conventional commits drive semantic releases when the repository defines a `RELEASE_TOKEN` with contents-write permission.

build.gradle.kts

@@ -0,0 +1,41 @@
+plugins {
+    java
+}
+
+group = "games.dmg"
+version = providers.gradleProperty("releaseVersion").orElse("0.1.0-SNAPSHOT").get()
+
+repositories {
+    mavenCentral()
+    maven("https://repo.purpurmc.org/snapshots/")
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(25)
+    }
+}
+
+tasks.withType<JavaCompile>().configureEach {
+    options.compilerArgs.addAll(listOf("-Xlint:all,-deprecation,-removal", "-Werror"))
+}
+
+dependencies {
+    compileOnly("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
+    testImplementation("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
+    testImplementation(platform("org.junit:junit-bom:5.13.4"))
+    testImplementation("org.junit.jupiter:junit-jupiter")
+    testImplementation("org.yaml:snakeyaml:2.4")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+val pluginVersion = version
+tasks.processResources {
+    filesMatching("plugin.yml") {
+        expand("version" to pluginVersion)
+    }
+}

design/index.md

@@ -0,0 +1,15 @@
+---
+type: Index
+title: Spigot Heights Design
+description: Entry point for the Spigot Heights OKF knowledge bundle.
+okf_version: "0.1"
+---
+
+# Spigot Heights Design
+
+This bundle documents craftable player-scaling potions, configurable stature limits, tiny-player dispenser launchers, persistence, and delivery requirements.
+
+## Explore
+
+- [User stories](user-stories/index.md)
+- [Design log](log.md)

design/log.md

@@ -0,0 +1,20 @@
+---
+type: Log
+title: Spigot Heights Design Log
+description: Chronological record of material decisions affecting Spigot Heights.
+---
+
+# Spigot Heights Design Log
+
+## 2026-09-04 — Initial design approved
+
+- Player scale defaults to a configurable range of `0.4` through `2.0`.
+- A moderate recipe creates a random stature potion; more expensive upgrades create targeted growth and diminution potions.
+- Random stature is selected uniformly in configurable `0.1` increments.
+- Players strictly below scale `0.5` can be launched through a dispenser fed by the hopper beneath them.
+- Launcher speed defaults to 1.5 blocks per tick with a 20-tick cooldown and safe-exit checks.
+- The project follows the neighboring Spigot Base Java 25, Purpur, Gradle, OKF, CI, and release conventions.
+
+## 2026-09-04 — Implementation started
+
+- Approved implementation began with user stories, tests, and the Gradle/Purpur foundation.

design/user-stories/index.md

@@ -0,0 +1,13 @@
+---
+type: Index
+title: Spigot Heights User Stories
+description: Catalog of user stories for the Spigot Heights plugin.
+---
+
+# Spigot Heights User Stories
+
+1. [US-001: Drink a Potion of Shifting Stature](us-001-drink-shifting-stature-potion.md)
+2. [US-002: Make precise stature adjustments](us-002-adjust-stature.md)
+3. [US-003: Launch tiny players through dispensers](us-003-launch-tiny-players.md)
+4. [US-004: Configure and persist stature behavior](us-004-configure-and-persist.md)
+5. [US-005: Build and release the plugin](us-005-build-and-release.md)

design/user-stories/us-001-drink-shifting-stature-potion.md

@@ -0,0 +1,25 @@
+---
+type: User Story
+title: "US-001: Drink a Potion of Shifting Stature"
+description: Let players craft and drink a potion that gives them a random configured scale.
+status: done
+---
+
+# US-001: Drink a Potion of Shifting Stature
+
+As a **player**, I want to drink a craftable potion that changes my stature unpredictably so that player size becomes a fun survival mechanic.
+
+## Acceptance criteria
+
+- [x] The distinct potion is authenticated with persistent item metadata rather than its display name alone.
+- [x] Its shaped recipe is `ACA/AWA/ACA`, where `A` is Amethyst Shard, `C` is Chorus Fruit, and `W` is an Awkward Potion.
+- [x] Drinking it consumes one potion, leaves normal bottle handling intact, and selects a scale from the configured inclusive range.
+- [x] Outcomes are uniformly selected in configured adjustment-step increments, including both endpoints when aligned.
+- [x] The resulting Minecraft scale attribute is applied and reported to the player.
+- [x] The resulting scale persists across logout, restart, world change, and death.
+- [x] Automated tests cover bounds, endpoint reachability, and recipe identity.
+
+## Related
+
+- [US-002: Make precise stature adjustments](us-002-adjust-stature.md)
+- [US-004: Configure and persist stature behavior](us-004-configure-and-persist.md)

design/user-stories/us-002-adjust-stature.md

@@ -0,0 +1,24 @@
+---
+type: User Story
+title: "US-002: Make precise stature adjustments"
+description: Let players craft upgraded potions that increase or decrease scale by one configured step.
+status: done
+---
+
+# US-002: Make precise stature adjustments
+
+As a **player**, I want more expensive growth and diminution potions so that I can adjust my stature predictably.
+
+## Acceptance criteria
+
+- [x] The Potion of Growth uses `GAG/ASA/GRG`, where `G` is Gold Ingot, `A` is Amethyst Shard, `S` is an authenticated Potion of Shifting Stature, and `R` is Rabbit's Foot.
+- [x] The Potion of Diminution uses `GAG/ASA/GFG`, where `F` is Fermented Spider Eye.
+- [x] Each resulting potion has distinct persistent metadata.
+- [x] Growth adds one configured adjustment step and clamps at the maximum.
+- [x] Diminution subtracts one configured adjustment step and clamps at the minimum.
+- [x] Adjusted scales are reported and persisted under the same rules as random stature.
+- [x] Automated tests cover adjustment, clamping, and potion identity.
+
+## Related
+
+- [US-001: Drink a Potion of Shifting Stature](us-001-drink-shifting-stature-potion.md)

design/user-stories/us-003-launch-tiny-players.md

@@ -0,0 +1,25 @@
+---
+type: User Story
+title: "US-003: Launch tiny players through dispensers"
+description: Launch sufficiently small players from a dispenser connected to the hopper beneath them.
+status: done
+---
+
+# US-003: Launch tiny players through dispensers
+
+As a **tiny player**, I want connected hoppers and dispensers to act as launch tubes so that my stature enables playful transport systems.
+
+## Acceptance criteria
+
+- [x] A player strictly below the configured threshold triggers when walking onto a hopper whose output points into a dispenser.
+- [x] No redstone signal is required.
+- [x] The player moves to a safe centered position immediately in front of the dispenser and receives velocity in its facing direction.
+- [x] Velocity magnitude and cooldown are configurable and default to 1.5 blocks per tick and 20 ticks.
+- [x] Obstructed or unsafe exits abort without moving the player.
+- [x] Players at or above the threshold are not launched.
+- [x] Cooldown prevents immediate repeated or cyclic launching.
+- [x] Automated tests cover threshold boundaries, orientations, cooldown, and obstruction policy.
+
+## Related
+
+- [US-004: Configure and persist stature behavior](us-004-configure-and-persist.md)

design/user-stories/us-004-configure-and-persist.md

@@ -0,0 +1,25 @@
+---
+type: User Story
+title: "US-004: Configure and persist stature behavior"
+description: Give operators validated settings and durable UUID-keyed player scales.
+status: done
+---
+
+# US-004: Configure and persist stature behavior
+
+As a **server operator**, I want validated stature and launcher settings with durable state so that behavior remains safe and predictable.
+
+## Acceptance criteria
+
+- [x] Defaults are minimum `0.4`, maximum `2.0`, adjustment step `0.1`, launcher threshold `0.5`, speed `1.5`, and cooldown `20` ticks.
+- [x] Configuration requires finite positive values, minimum no greater than maximum, and a launcher threshold within the supported scale range.
+- [x] Invalid startup configuration disables the plugin with a clear error.
+- [x] Player scales are stored by UUID using atomic file replacement where supported.
+- [x] Updating known state preserves unknown forward-compatible YAML fields.
+- [x] Missing state defaults safely to scale `1.0` clamped to the configured range.
+- [x] Saved out-of-range state is clamped before it is applied.
+- [x] Configuration and state behavior have automated tests.
+
+## Related
+
+- [User-story catalog](index.md)

design/user-stories/us-005-build-and-release.md

@@ -0,0 +1,24 @@
+---
+type: User Story
+title: "US-005: Build and release the plugin"
+description: Give maintainers repeatable Purpur builds, automated verification, and versioned Gitea releases.
+status: in-progress
+---
+
+# US-005: Build and release the plugin
+
+As a **plugin maintainer**, I want automated builds and releases modeled on Spigot Base so that tested artifacts can be distributed consistently.
+
+## Acceptance criteria
+
+- [ ] Gradle compiles against Purpur API `26.2.build.2618-stable` using Java 25.
+- [ ] Compiler lint warnings fail the build and JUnit 5 tests run during `check`.
+- [ ] Gitea Actions verifies pushes and pull requests and stores a development JAR.
+- [ ] Pull requests validate conventional commits.
+- [ ] Main-branch conventional commits drive semantic releases and attach versioned JARs to Gitea releases.
+- [ ] The README documents requirements, recipes, configuration, building, and releases.
+- [ ] `./gradlew clean check jar` succeeds.
+
+## Related
+
+- [User-story catalog](index.md)

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,248 @@
+#!/bin/sh
+
+#
+# Copyright © 2015 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   gradlew start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh gradlew
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/3d91ce3b8caaf77ad09f381f43615b715b53f72c/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='-Dfile.encoding=UTF-8 "-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,82 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  gradlew startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables, and ensure extensions are enabled
+setlocal EnableExtensions
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=-Dfile.encoding=UTF-8 "-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+"%COMSPEC%" /c exit 1
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+"%COMSPEC%" /c exit 1
+
+:execute
+@rem Setup the command line
+
+
+
+@rem Execute gradlew
+@rem endlocal doesn't take effect until after the line is parsed and variables are expanded
+@rem which allows us to clear the local environment before executing the java command
+endlocal & "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %* & call :exitWithErrorLevel
+
+:exitWithErrorLevel
+@rem Use "%COMSPEC%" /c exit to allow operators to work properly in scripts
+"%COMSPEC%" /c exit %ERRORLEVEL%

settings.gradle.kts

@@ -0,0 +1,5 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
+}
+
+rootProject.name = "spigot-heights"

src/main/java/games/dmg/spigotheights/HeightMath.java

@@ -0,0 +1,40 @@
+package games.dmg.spigotheights;
+
+import java.util.function.IntUnaryOperator;
+
+public final class HeightMath {
+    private HeightMath() {
+    }
+
+    public static double randomScale(HeightSettings settings, IntUnaryOperator randomIndex) {
+        int outcomes = settings.randomStepCount() + 1;
+        int index = randomIndex.applyAsInt(outcomes);
+        if (index < 0 || index >= outcomes) {
+            throw new IllegalArgumentException("random index is outside the requested bound");
+        }
+        return normalize(settings.minimum() + index * settings.adjustmentStep());
+    }
+
+    public static double grow(double current, HeightSettings settings) {
+        return clamp(current + settings.adjustmentStep(), settings);
+    }
+
+    public static double shrink(double current, HeightSettings settings) {
+        return clamp(current - settings.adjustmentStep(), settings);
+    }
+
+    public static double safeStoredScale(Double stored, HeightSettings settings) {
+        if (stored == null || !Double.isFinite(stored)) {
+            return clamp(1.0, settings);
+        }
+        return clamp(stored, settings);
+    }
+
+    public static double clamp(double value, HeightSettings settings) {
+        return normalize(Math.max(settings.minimum(), Math.min(settings.maximum(), value)));
+    }
+
+    private static double normalize(double value) {
+        return Math.rint(value * 1_000_000.0) / 1_000_000.0;
+    }
+}

src/main/java/games/dmg/spigotheights/HeightSettings.java

@@ -0,0 +1,40 @@
+package games.dmg.spigotheights;
+
+public record HeightSettings(
+        double minimum,
+        double maximum,
+        double adjustmentStep,
+        double launcherThreshold,
+        double launcherSpeed,
+        int launcherCooldownTicks) {
+
+    public HeightSettings {
+        requirePositiveFinite("height.minimum", minimum);
+        requirePositiveFinite("height.maximum", maximum);
+        requirePositiveFinite("height.adjustment-step", adjustmentStep);
+        requirePositiveFinite("launcher.maximum-player-scale-exclusive", launcherThreshold);
+        requirePositiveFinite("launcher.speed", launcherSpeed);
+        if (minimum > maximum) {
+            throw new IllegalArgumentException("height.minimum must not exceed height.maximum");
+        }
+        if (minimum < 0.0625 || maximum > 16.0) {
+            throw new IllegalArgumentException("height range must stay within Minecraft's 0.0625 to 16.0 scale range");
+        }
+        if (launcherThreshold < minimum || launcherThreshold > maximum) {
+            throw new IllegalArgumentException("launcher threshold must be within the height range");
+        }
+        if (launcherCooldownTicks < 0) {
+            throw new IllegalArgumentException("launcher.cooldown-ticks must not be negative");
+        }
+    }
+
+    public int randomStepCount() {
+        return (int) Math.floor((maximum - minimum) / adjustmentStep + 1.0e-9);
+    }
+
+    private static void requirePositiveFinite(String key, double value) {
+        if (!Double.isFinite(value) || value <= 0.0) {
+            throw new IllegalArgumentException(key + " must be a finite positive number");
+        }
+    }
+}

src/main/java/games/dmg/spigotheights/HeightStore.java

@@ -0,0 +1,43 @@
+package games.dmg.spigotheights;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.UUID;
+import org.bukkit.configuration.file.YamlConfiguration;
+
+public final class HeightStore {
+    private final Path statePath;
+    private final YamlConfiguration state;
+
+    public HeightStore(File dataFolder) {
+        statePath = dataFolder.toPath().resolve("state.yml");
+        state = YamlConfiguration.loadConfiguration(statePath.toFile());
+    }
+
+    public synchronized Double find(UUID playerId) {
+        String path = path(playerId);
+        return state.contains(path) ? state.getDouble(path) : null;
+    }
+
+    public synchronized void save(UUID playerId, double scale) throws IOException {
+        state.set(path(playerId), scale);
+        Files.createDirectories(statePath.getParent());
+        Path temporary = statePath.resolveSibling("state.yml.tmp");
+        Files.writeString(temporary, state.saveToString(), StandardCharsets.UTF_8);
+        try {
+            Files.move(temporary, statePath, StandardCopyOption.ATOMIC_MOVE,
+                    StandardCopyOption.REPLACE_EXISTING);
+        } catch (AtomicMoveNotSupportedException exception) {
+            Files.move(temporary, statePath, StandardCopyOption.REPLACE_EXISTING);
+        }
+    }
+
+    private static String path(UUID playerId) {
+        return "players." + playerId + ".scale";
+    }
+}

src/main/java/games/dmg/spigotheights/LaunchVector.java

@@ -0,0 +1,11 @@
+package games.dmg.spigotheights;
+
+public record LaunchVector(double x, double y, double z) {
+    public static LaunchVector fromDirection(int x, int y, int z, double speed) {
+        double length = Math.sqrt((double) x * x + (double) y * y + (double) z * z);
+        if (length == 0.0) {
+            throw new IllegalArgumentException("launch direction must not be stationary");
+        }
+        return new LaunchVector(x / length * speed, y / length * speed, z / length * speed);
+    }
+}

src/main/java/games/dmg/spigotheights/LauncherPolicy.java

@@ -0,0 +1,18 @@
+package games.dmg.spigotheights;
+
+public final class LauncherPolicy {
+    private LauncherPolicy() {
+    }
+
+    public static boolean isSmallEnough(double scale, double exclusiveThreshold) {
+        return scale < exclusiveThreshold;
+    }
+
+    public static boolean cooldownExpired(Long previousTick, long currentTick, int cooldownTicks) {
+        return previousTick == null || currentTick - previousTick >= cooldownTicks;
+    }
+
+    public static boolean isSafeExit(boolean empty) {
+        return empty;
+    }
+}

src/main/java/games/dmg/spigotheights/PotionRecipes.java

@@ -0,0 +1,106 @@
+package games.dmg.spigotheights;
+
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import org.bukkit.Color;
+import org.bukkit.Material;
+import org.bukkit.NamespacedKey;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.RecipeChoice;
+import org.bukkit.inventory.ShapedRecipe;
+import org.bukkit.inventory.meta.PotionMeta;
+import org.bukkit.persistence.PersistentDataType;
+import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.potion.PotionType;
+
+public final class PotionRecipes {
+    static final String[] SHIFTING_SHAPE = {"ACA", "AWA", "ACA"};
+    static final String[] GROWTH_SHAPE = {"GAG", "ASA", "GRG"};
+    static final String[] DIMINUTION_SHAPE = {"GAG", "ASA", "GFG"};
+
+    private final JavaPlugin plugin;
+    private final NamespacedKey potionKindKey;
+
+    public PotionRecipes(JavaPlugin plugin) {
+        this.plugin = plugin;
+        potionKindKey = new NamespacedKey(plugin, "stature_potion");
+    }
+
+    public void register() {
+        registerShifting();
+        registerGrowth();
+        registerDiminution();
+    }
+
+    public ItemStack create(StaturePotion kind) {
+        ItemStack item = new ItemStack(Material.POTION);
+        PotionMeta meta = (PotionMeta) item.getItemMeta();
+        meta.displayName(Component.text(kind.displayName(), NamedTextColor.LIGHT_PURPLE));
+        meta.getPersistentDataContainer().set(potionKindKey, PersistentDataType.STRING, kind.name());
+        meta.setColor(color(kind));
+        item.setItemMeta(meta);
+        return item;
+    }
+
+    public StaturePotion identify(ItemStack item) {
+        if (item == null || item.getType() != Material.POTION || !(item.getItemMeta() instanceof PotionMeta meta)) {
+            return null;
+        }
+        String value = meta.getPersistentDataContainer().get(potionKindKey, PersistentDataType.STRING);
+        if (value == null) {
+            return null;
+        }
+        try {
+            return StaturePotion.valueOf(value);
+        } catch (IllegalArgumentException exception) {
+            return null;
+        }
+    }
+
+    public boolean isAwkwardPotion(ItemStack item) {
+        return item != null && item.getItemMeta() instanceof PotionMeta meta
+                && meta.getBasePotionType() == PotionType.AWKWARD;
+    }
+
+    public NamespacedKey shiftingKey() {
+        return new NamespacedKey(plugin, "shifting_stature");
+    }
+
+    private void registerShifting() {
+        ShapedRecipe recipe = new ShapedRecipe(shiftingKey(), create(StaturePotion.SHIFTING));
+        recipe.shape(SHIFTING_SHAPE);
+        recipe.setIngredient('A', Material.AMETHYST_SHARD);
+        recipe.setIngredient('C', Material.CHORUS_FRUIT);
+        recipe.setIngredient('W', Material.POTION);
+        plugin.getServer().addRecipe(recipe);
+    }
+
+    private void registerGrowth() {
+        ShapedRecipe recipe = new ShapedRecipe(new NamespacedKey(plugin, "growth"), create(StaturePotion.GROWTH));
+        recipe.shape(GROWTH_SHAPE);
+        recipe.setIngredient('G', Material.GOLD_INGOT);
+        recipe.setIngredient('A', Material.AMETHYST_SHARD);
+        recipe.setIngredient('S', new RecipeChoice.ExactChoice(create(StaturePotion.SHIFTING)));
+        recipe.setIngredient('R', Material.RABBIT_FOOT);
+        plugin.getServer().addRecipe(recipe);
+    }
+
+    private void registerDiminution() {
+        ShapedRecipe recipe = new ShapedRecipe(new NamespacedKey(plugin, "diminution"),
+                create(StaturePotion.DIMINUTION));
+        recipe.shape(DIMINUTION_SHAPE);
+        recipe.setIngredient('G', Material.GOLD_INGOT);
+        recipe.setIngredient('A', Material.AMETHYST_SHARD);
+        recipe.setIngredient('S', new RecipeChoice.ExactChoice(create(StaturePotion.SHIFTING)));
+        recipe.setIngredient('F', Material.FERMENTED_SPIDER_EYE);
+        plugin.getServer().addRecipe(recipe);
+    }
+
+    private static Color color(StaturePotion kind) {
+        return switch (kind) {
+            case SHIFTING -> Color.PURPLE;
+            case GROWTH -> Color.LIME;
+            case DIMINUTION -> Color.FUCHSIA;
+        };
+    }
+}

src/main/java/games/dmg/spigotheights/SpigotHeightsPlugin.java

@@ -0,0 +1,37 @@
+package games.dmg.spigotheights;
+
+import org.bukkit.configuration.file.FileConfiguration;
+import org.bukkit.plugin.java.JavaPlugin;
+
+public final class SpigotHeightsPlugin extends JavaPlugin {
+    @Override
+    public void onEnable() {
+        saveDefaultConfig();
+        HeightSettings settings;
+        try {
+            settings = loadSettings(getConfig());
+        } catch (IllegalArgumentException exception) {
+            getLogger().severe("Invalid configuration: " + exception.getMessage());
+            getServer().getPluginManager().disablePlugin(this);
+            return;
+        }
+
+        HeightStore store = new HeightStore(getDataFolder());
+        PotionRecipes potions = new PotionRecipes(this);
+        potions.register();
+        getServer().getPluginManager().registerEvents(
+                new StatureListener(this, settings, store, potions), this);
+        getServer().getPluginManager().registerEvents(new TinyPlayerLauncher(settings), this);
+        getLogger().info("Spigot Heights enabled.");
+    }
+
+    static HeightSettings loadSettings(FileConfiguration config) {
+        return new HeightSettings(
+                config.getDouble("height.minimum"),
+                config.getDouble("height.maximum"),
+                config.getDouble("height.adjustment-step"),
+                config.getDouble("launcher.maximum-player-scale-exclusive"),
+                config.getDouble("launcher.speed"),
+                config.getInt("launcher.cooldown-ticks"));
+    }
+}

src/main/java/games/dmg/spigotheights/StatureListener.java

@@ -0,0 +1,97 @@
+package games.dmg.spigotheights;
+
+import java.io.IOException;
+import java.util.concurrent.ThreadLocalRandom;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeInstance;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.inventory.PrepareItemCraftEvent;
+import org.bukkit.event.player.PlayerItemConsumeEvent;
+import org.bukkit.event.player.PlayerJoinEvent;
+import org.bukkit.event.player.PlayerRespawnEvent;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.Recipe;
+import org.bukkit.Keyed;
+import org.bukkit.plugin.java.JavaPlugin;
+
+public final class StatureListener implements Listener {
+    private final JavaPlugin plugin;
+    private final HeightSettings settings;
+    private final HeightStore store;
+    private final PotionRecipes potions;
+
+    public StatureListener(JavaPlugin plugin, HeightSettings settings, HeightStore store, PotionRecipes potions) {
+        this.plugin = plugin;
+        this.settings = settings;
+        this.store = store;
+        this.potions = potions;
+    }
+
+    @EventHandler
+    public void onCraftPrepare(PrepareItemCraftEvent event) {
+        Recipe recipe = event.getRecipe();
+        if (!(recipe instanceof Keyed keyed) || !keyed.getKey().equals(potions.shiftingKey())) {
+            return;
+        }
+        ItemStack[] matrix = event.getInventory().getMatrix();
+        if (matrix.length < 5 || !potions.isAwkwardPotion(matrix[4])) {
+            event.getInventory().setResult(null);
+        }
+    }
+
+    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
+    public void onConsume(PlayerItemConsumeEvent event) {
+        StaturePotion kind = potions.identify(event.getItem());
+        if (kind == null) {
+            return;
+        }
+        Player player = event.getPlayer();
+        double current = currentScale(player);
+        double scale = switch (kind) {
+            case SHIFTING -> HeightMath.randomScale(settings,
+                    bound -> ThreadLocalRandom.current().nextInt(bound));
+            case GROWTH -> HeightMath.grow(current, settings);
+            case DIMINUTION -> HeightMath.shrink(current, settings);
+        };
+        applyAndSave(player, scale);
+        player.sendMessage("Your scale is now " + scale + ".");
+    }
+
+    @EventHandler
+    public void onJoin(PlayerJoinEvent event) {
+        apply(event.getPlayer(), HeightMath.safeStoredScale(store.find(event.getPlayer().getUniqueId()), settings));
+    }
+
+    @EventHandler
+    public void onRespawn(PlayerRespawnEvent event) {
+        plugin.getServer().getScheduler().runTask(plugin, () -> {
+            Player player = event.getPlayer();
+            apply(player, HeightMath.safeStoredScale(store.find(player.getUniqueId()), settings));
+        });
+    }
+
+    private void applyAndSave(Player player, double scale) {
+        apply(player, scale);
+        try {
+            store.save(player.getUniqueId(), scale);
+        } catch (IOException exception) {
+            plugin.getLogger().severe("Could not save scale for " + player.getUniqueId() + ": "
+                    + exception.getMessage());
+        }
+    }
+
+    private static void apply(Player player, double scale) {
+        AttributeInstance attribute = player.getAttribute(Attribute.SCALE);
+        if (attribute != null) {
+            attribute.setBaseValue(scale);
+        }
+    }
+
+    private static double currentScale(Player player) {
+        AttributeInstance attribute = player.getAttribute(Attribute.SCALE);
+        return attribute == null ? 1.0 : attribute.getBaseValue();
+    }
+}

src/main/java/games/dmg/spigotheights/StaturePotion.java

@@ -0,0 +1,17 @@
+package games.dmg.spigotheights;
+
+public enum StaturePotion {
+    SHIFTING("Potion of Shifting Stature"),
+    GROWTH("Potion of Growth"),
+    DIMINUTION("Potion of Diminution");
+
+    private final String displayName;
+
+    StaturePotion(String displayName) {
+        this.displayName = displayName;
+    }
+
+    public String displayName() {
+        return displayName;
+    }
+}

src/main/java/games/dmg/spigotheights/TinyPlayerLauncher.java

@@ -0,0 +1,82 @@
+package games.dmg.spigotheights;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeInstance;
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockFace;
+import org.bukkit.block.data.Directional;
+import org.bukkit.block.data.type.Hopper;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerMoveEvent;
+import org.bukkit.util.Vector;
+
+public final class TinyPlayerLauncher implements Listener {
+    private final HeightSettings settings;
+    private final Map<UUID, Long> lastLaunchTicks = new HashMap<>();
+
+    public TinyPlayerLauncher(HeightSettings settings) {
+        this.settings = settings;
+    }
+
+    @EventHandler(ignoreCancelled = true)
+    public void onMove(PlayerMoveEvent event) {
+        Location destination = event.getTo();
+        if (destination == null || sameBlock(event.getFrom(), destination)) {
+            return;
+        }
+        Player player = event.getPlayer();
+        if (!LauncherPolicy.isSmallEnough(scale(player), settings.launcherThreshold())) {
+            return;
+        }
+        long tick = Bukkit.getCurrentTick();
+        Long lastTick = lastLaunchTicks.get(player.getUniqueId());
+        if (!LauncherPolicy.cooldownExpired(lastTick, tick, settings.launcherCooldownTicks())) {
+            return;
+        }
+        Block hopperBlock = destination.clone().subtract(0.0, 0.1, 0.0).getBlock();
+        if (!(hopperBlock.getBlockData() instanceof Hopper hopper)) {
+            return;
+        }
+        Block dispenser = hopperBlock.getRelative(hopper.getFacing());
+        if (dispenser.getType() != Material.DISPENSER
+                || !(dispenser.getBlockData() instanceof Directional directional)) {
+            return;
+        }
+        BlockFace facing = directional.getFacing();
+        Block exit = dispenser.getRelative(facing);
+        if (!LauncherPolicy.isSafeExit(exit.isEmpty())) {
+            return;
+        }
+        Location exitLocation = exit.getLocation().add(0.5, 0.1, 0.5);
+        exitLocation.setYaw(player.getLocation().getYaw());
+        exitLocation.setPitch(player.getLocation().getPitch());
+        if (!player.teleport(exitLocation)) {
+            return;
+        }
+        Vector direction = facing.getDirection();
+        LaunchVector launch = LaunchVector.fromDirection(
+                direction.getBlockX(), direction.getBlockY(), direction.getBlockZ(), settings.launcherSpeed());
+        player.setVelocity(new Vector(launch.x(), launch.y(), launch.z()));
+        lastLaunchTicks.put(player.getUniqueId(), tick);
+    }
+
+    private static boolean sameBlock(Location first, Location second) {
+        return first.getWorld().equals(second.getWorld())
+                && first.getBlockX() == second.getBlockX()
+                && first.getBlockY() == second.getBlockY()
+                && first.getBlockZ() == second.getBlockZ();
+    }
+
+    private static double scale(Player player) {
+        AttributeInstance attribute = player.getAttribute(Attribute.SCALE);
+        return attribute == null ? 1.0 : attribute.getValue();
+    }
+}

src/main/resources/config.yml

@@ -0,0 +1,9 @@
+height:
+  minimum: 0.4
+  maximum: 2.0
+  adjustment-step: 0.1
+
+launcher:
+  maximum-player-scale-exclusive: 0.5
+  speed: 1.5
+  cooldown-ticks: 20

src/main/resources/plugin.yml

@@ -0,0 +1,6 @@
+name: SpigotHeights
+version: ${version}
+main: games.dmg.spigotheights.SpigotHeightsPlugin
+api-version: "1.21"
+description: Craftable player stature potions and tiny-player dispenser launchers.
+author: dmg.games

src/test/java/games/dmg/spigotheights/HeightMathTest.java

@@ -0,0 +1,29 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class HeightMathTest {
+    private static final HeightSettings SETTINGS = new HeightSettings(0.4, 2.0, 0.1, 0.5, 1.5, 20);
+
+    @Test
+    void randomSelectionCanReachBothInclusiveEndpoints() {
+        assertEquals(0.4, HeightMath.randomScale(SETTINGS, bound -> 0), 0.000001);
+        assertEquals(2.0, HeightMath.randomScale(SETTINGS, bound -> bound - 1), 0.000001);
+    }
+
+    @Test
+    void adjustmentsClampAtLimitsWithoutFloatingPointDrift() {
+        assertEquals(2.0, HeightMath.grow(1.95, SETTINGS), 0.000001);
+        assertEquals(0.4, HeightMath.shrink(0.42, SETTINGS), 0.000001);
+        assertEquals(1.1, HeightMath.grow(1.0, SETTINGS), 0.000001);
+    }
+
+    @Test
+    void missingAndStoredValuesAreSafelyClamped() {
+        assertEquals(1.0, HeightMath.safeStoredScale(null, SETTINGS), 0.000001);
+        assertEquals(0.4, HeightMath.safeStoredScale(-2.0, SETTINGS), 0.000001);
+        assertEquals(2.0, HeightMath.safeStoredScale(4.0, SETTINGS), 0.000001);
+    }
+}

src/test/java/games/dmg/spigotheights/HeightSettingsTest.java

@@ -0,0 +1,27 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class HeightSettingsTest {
+    @Test
+    void acceptsDocumentedDefaults() {
+        HeightSettings settings = new HeightSettings(0.4, 2.0, 0.1, 0.5, 1.5, 20);
+        assertEquals(0.4, settings.minimum());
+        assertEquals(16, settings.randomStepCount());
+    }
+
+    @Test
+    void rejectsInvalidRangesAndNumbers() {
+        assertThrows(IllegalArgumentException.class,
+                () -> new HeightSettings(2.0, 0.4, 0.1, 0.5, 1.5, 20));
+        assertThrows(IllegalArgumentException.class,
+                () -> new HeightSettings(0.4, 2.0, 0.0, 0.5, 1.5, 20));
+        assertThrows(IllegalArgumentException.class,
+                () -> new HeightSettings(0.4, 2.0, 0.1, 2.1, 1.5, 20));
+        assertThrows(IllegalArgumentException.class,
+                () -> new HeightSettings(0.4, Double.NaN, 0.1, 0.5, 1.5, 20));
+    }
+}

src/test/java/games/dmg/spigotheights/HeightStoreTest.java

@@ -0,0 +1,28 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+class HeightStoreTest {
+    @TempDir
+    Path temporaryDirectory;
+
+    @Test
+    void storesByUuidAndPreservesUnknownYamlFields() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Path stateFile = temporaryDirectory.resolve("state.yml");
+        Files.writeString(stateFile, "future-setting: retained\n");
+        HeightStore store = new HeightStore(temporaryDirectory.toFile());
+
+        store.save(playerId, 0.7);
+
+        HeightStore reloaded = new HeightStore(temporaryDirectory.toFile());
+        assertEquals(0.7, reloaded.find(playerId));
+        assertEquals(true, Files.readString(stateFile).contains("future-setting: retained"));
+    }
+}

src/test/java/games/dmg/spigotheights/LaunchVectorTest.java

@@ -0,0 +1,23 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class LaunchVectorTest {
+    @Test
+    void supportsEveryDispenserAxisAtConfiguredSpeed() {
+        assertVector(1.5, 0.0, 0.0, LaunchVector.fromDirection(1, 0, 0, 1.5));
+        assertVector(-1.5, 0.0, 0.0, LaunchVector.fromDirection(-1, 0, 0, 1.5));
+        assertVector(0.0, 1.5, 0.0, LaunchVector.fromDirection(0, 1, 0, 1.5));
+        assertVector(0.0, -1.5, 0.0, LaunchVector.fromDirection(0, -1, 0, 1.5));
+        assertVector(0.0, 0.0, 1.5, LaunchVector.fromDirection(0, 0, 1, 1.5));
+        assertVector(0.0, 0.0, -1.5, LaunchVector.fromDirection(0, 0, -1, 1.5));
+    }
+
+    private static void assertVector(double x, double y, double z, LaunchVector actual) {
+        assertEquals(x, actual.x(), 0.000001);
+        assertEquals(y, actual.y(), 0.000001);
+        assertEquals(z, actual.z(), 0.000001);
+    }
+}

src/test/java/games/dmg/spigotheights/LauncherPolicyTest.java

@@ -0,0 +1,28 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class LauncherPolicyTest {
+    @Test
+    void thresholdIsStrictlyExclusive() {
+        assertTrue(LauncherPolicy.isSmallEnough(0.4999, 0.5));
+        assertFalse(LauncherPolicy.isSmallEnough(0.5, 0.5));
+        assertFalse(LauncherPolicy.isSmallEnough(1.0, 0.5));
+    }
+
+    @Test
+    void cooldownExpiresAtConfiguredTick() {
+        assertFalse(LauncherPolicy.cooldownExpired(100L, 119, 20));
+        assertTrue(LauncherPolicy.cooldownExpired(100L, 120, 20));
+        assertTrue(LauncherPolicy.cooldownExpired(null, 1, 20));
+    }
+
+    @Test
+    void onlyEmptyDispenserExitsAreSafe() {
+        assertTrue(LauncherPolicy.isSafeExit(true));
+        assertFalse(LauncherPolicy.isSafeExit(false));
+    }
+}

src/test/java/games/dmg/spigotheights/PotionRecipesTest.java

@@ -0,0 +1,22 @@
+package games.dmg.spigotheights;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+import org.junit.jupiter.api.Test;
+
+class PotionRecipesTest {
+    @Test
+    void recipesUseApprovedShapes() {
+        assertArrayEquals(new String[] {"ACA", "AWA", "ACA"}, PotionRecipes.SHIFTING_SHAPE);
+        assertArrayEquals(new String[] {"GAG", "ASA", "GRG"}, PotionRecipes.GROWTH_SHAPE);
+        assertArrayEquals(new String[] {"GAG", "ASA", "GFG"}, PotionRecipes.DIMINUTION_SHAPE);
+    }
+
+    @Test
+    void everyPotionHasASeparatePersistentIdentity() {
+        assertNotEquals(StaturePotion.SHIFTING.name(), StaturePotion.GROWTH.name());
+        assertNotEquals(StaturePotion.GROWTH.name(), StaturePotion.DIMINUTION.name());
+        assertNotEquals(StaturePotion.DIMINUTION.name(), StaturePotion.SHIFTING.name());
+    }
+}