import { access, readFile, readdir } from "node:fs/promises";

const designDirectory = new URL("../design/", import.meta.url);
const reservedFiles = new Set(["index.md", "log.md"]);
const allowedStatuses = new Set(["proposed", "in-progress", "implemented", "verified"]);
const failures = [];
const storyIds = new Map();

async function markdownFiles(directory, relativeDirectory = "") {
  const files = [];
  for (const entry of await readdir(directory, { withFileTypes: true })) {
    const relativePath = relativeDirectory ? `${relativeDirectory}/${entry.name}` : entry.name;
    if (entry.isDirectory()) {
      files.push(...await markdownFiles(new URL(`${entry.name}/`, directory), relativePath));
    } else if (entry.isFile() && entry.name.endsWith(".md")) {
      files.push({ name: entry.name, relativePath, url: new URL(entry.name, directory) });
    }
  }
  return files;
}

for (const file of await markdownFiles(designDirectory)) {
  const contents = await readFile(file.url, "utf8");
  for (const link of contents.matchAll(/\[[^\]]+\]\(([^)\s]+)\)/g)) {
    const target = link[1].split("#", 1)[0];
    if (!target || target.startsWith("#") || /^[a-z][a-z0-9+.-]*:/i.test(target)) continue;
    const targetUrl = target.startsWith("/")
      ? new URL(target.slice(1), designDirectory)
      : new URL(target, file.url);
    try {
      await access(targetUrl);
    } catch {
      failures.push(`${file.relativePath}: broken link ${target}`);
    }
  }

  if (reservedFiles.has(file.name)) continue;

  const frontmatter = contents.match(/^---\n([\s\S]*?)\n---\n/);
  if (!frontmatter) {
    failures.push(`${file.relativePath}: missing YAML frontmatter`);
    continue;
  }

  const metadata = Object.fromEntries(
    frontmatter[1]
      .split("\n")
      .map((line) => line.match(/^([a-zA-Z_][\w-]*):\s*(.*)$/))
      .filter(Boolean)
      .map((match) => [match[1], match[2].replace(/^['"]|['"]$/g, "")]),
  );

  if (!metadata.type) failures.push(`${file.relativePath}: missing required type`);
  if (metadata.type === "User Story") {
    for (const field of ["story_id", "title", "description", "status", "timestamp"]) {
      if (!metadata[field]) failures.push(`${file.relativePath}: missing ${field}`);
    }
    if (metadata.status && !allowedStatuses.has(metadata.status)) {
      failures.push(`${file.relativePath}: invalid status ${metadata.status}`);
    }
    if (metadata.timestamp && Number.isNaN(Date.parse(metadata.timestamp))) {
      failures.push(`${file.relativePath}: timestamp is not ISO 8601`);
    }
    if (metadata.story_id) {
      const duplicate = storyIds.get(metadata.story_id);
      if (duplicate) failures.push(`${file.relativePath}: duplicate ${metadata.story_id} also used by ${duplicate}`);
      storyIds.set(metadata.story_id, file.relativePath);
    }
  }
}

const index = await readFile(new URL("index.md", designDirectory), "utf8");
for (const [storyId, filename] of storyIds) {
  if (!index.includes(`(${filename})`)) failures.push(`index.md: missing ${storyId} link to ${filename}`);
}

const log = await readFile(new URL("log.md", designDirectory), "utf8");
for (const heading of log.matchAll(/^##\s+(.+)$/gm)) {
  if (!/^\d{4}-\d{2}-\d{2}$/.test(heading[1])) {
    failures.push(`log.md: invalid date heading ${heading[1]}`);
  }
}

if (failures.length) {
  console.error("OKF validation failed:\n" + failures.map((failure) => `- ${failure}`).join("\n"));
  process.exit(1);
}

console.log(`OKF validation passed: ${storyIds.size} user stories.`);