spigot-quest-board/src/main/java/games/dmg/spigotquestboard/QuestCommand.java

package games.dmg.spigotquestboard;

import java.io.IOException;
import java.time.Clock;
import java.time.Instant;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.command.TabCompleter;
import org.bukkit.entity.Player;

final class QuestCommand implements CommandExecutor, TabCompleter {
    private static final List<String> QUANTITIES = List.of("1", "16", "32", "64");
    private final QuestCreationGateway creator;
    private final QuestBrowser browser;
    private final QuestCompletionGateway completer;
    private final QuestCancellationGateway canceller;
    private final Clock clock;

    QuestCommand(QuestCreationGateway creator, QuestBrowser browser, Clock clock) {
        this(creator, browser, null, null, clock);
    }

    QuestCommand(
        QuestCreationGateway creator,
        QuestBrowser browser,
        QuestCompletionGateway completer,
        Clock clock
    ) {
        this(creator, browser, completer, null, clock);
    }

    QuestCommand(
        QuestCreationGateway creator,
        QuestBrowser browser,
        QuestCompletionGateway completer,
        QuestCancellationGateway canceller,
        Clock clock
    ) {
        this.creator = Objects.requireNonNull(creator, "creator");
        this.browser = Objects.requireNonNull(browser, "browser");
        this.completer = completer;
        this.canceller = canceller;
        this.clock = Objects.requireNonNull(clock, "clock");
    }

    @Override
    public boolean onCommand(
        CommandSender sender, Command command, String label, String[] arguments
    ) {
        if (arguments.length == 0
            || (arguments.length == 1 && "list".equalsIgnoreCase(arguments[0]))) {
            Instant now = clock.instant();
            sender.sendMessage(QuestListingFormatter.formatAll(browser.activeQuests(now), now));
            return true;
        }
        if (arguments.length == 2 && "complete".equalsIgnoreCase(arguments[0])) {
            if (!(sender instanceof Player player)) {
                sender.sendMessage("Only players can complete quests with inventory items.");
                return true;
            }
            if (completer == null) {
                sender.sendMessage("Quest completion is unavailable.");
                return true;
            }
            try {
                completer.complete(player, arguments[1], clock.instant());
            } catch (IllegalArgumentException | IllegalStateException exception) {
                sender.sendMessage(exception.getMessage());
            } catch (IOException exception) {
                sender.sendMessage(
                    "The quest could not be saved. Your delivered blocks were restored."
                );
            }
            return true;
        }
        if (arguments.length == 2 && "cancel".equalsIgnoreCase(arguments[0])) {
            if (!(sender instanceof Player player)) {
                sender.sendMessage("Only players can cancel quests.");
                return true;
            }
            if (canceller == null) {
                sender.sendMessage("Quest cancellation is unavailable.");
                return true;
            }
            try {
                canceller.cancel(player, arguments[1], clock.instant());
            } catch (IllegalArgumentException | IllegalStateException exception) {
                sender.sendMessage(exception.getMessage());
            } catch (IOException exception) {
                sender.sendMessage(
                    "The quest could not be saved. It remains active and its reward remains escrowed."
                );
            }
            return true;
        }
        if (arguments.length != 3 || !"create".equalsIgnoreCase(arguments[0])) {
            usage(sender);
            return true;
        }
        if (!(sender instanceof Player player)) {
            sender.sendMessage("Only players can create quests with inventory rewards.");
            return true;
        }
        final int quantity;
        try {
            quantity = Integer.parseInt(arguments[2]);
        } catch (NumberFormatException exception) {
            sender.sendMessage("Quest quantity must be a positive whole number.");
            return true;
        }
        try {
            Quest quest = creator.create(player, arguments[1], quantity, clock.instant());
            sender.sendMessage("Quest " + quest.id() + " created. Your exact held stack is now escrowed.");
        } catch (IllegalArgumentException exception) {
            sender.sendMessage(exception.getMessage());
        } catch (IOException exception) {
            sender.sendMessage("The quest could not be saved. Your held reward was restored.");
        }
        return true;
    }

    @Override
    public List<String> onTabComplete(
        CommandSender sender, Command command, String alias, String[] arguments
    ) {
        if (!(sender instanceof Player)) {
            return List.of();
        }
        if (arguments.length == 1) {
            return startsWith(List.of("create", "list", "complete", "cancel"), arguments[0]);
        }
        if (arguments.length == 2 && "create".equalsIgnoreCase(arguments[0])) {
            return creator.suggestBlockMaterials(arguments[1]);
        }
        if (arguments.length == 3 && "create".equalsIgnoreCase(arguments[0])) {
            return startsWith(QUANTITIES, arguments[2]);
        }
        if (arguments.length == 2 && "complete".equalsIgnoreCase(arguments[0])) {
            return startsWith(browser.completableQuestIds(clock.instant()), arguments[1]);
        }
        if (arguments.length == 2 && "cancel".equalsIgnoreCase(arguments[0])) {
            Player player = (Player) sender;
            return startsWith(
                browser.cancellableQuestIds(player.getUniqueId(), clock.instant()), arguments[1]
            );
        }
        return List.of();
    }

    private static List<String> startsWith(List<String> candidates, String prefix) {
        String normalized = prefix.toLowerCase(Locale.ROOT);
        return candidates.stream()
            .filter(candidate -> candidate.toLowerCase(Locale.ROOT).startsWith(normalized))
            .toList();
    }

    private static void usage(CommandSender sender) {
        sender.sendMessage(
            "Usage: /quests [list] | /quests create <block> <quantity> | "
                + "/quests complete <quest> | /quests cancel <quest>"
        );
        sender.sendMessage("Hold the entire reward stack in your main hand; its exact metadata will be escrowed.");
    }
}