import * as yaml from "js-yaml";
import * as path from "path";
import { isValidSkillName } from "./activation";
import { MAX_ROUTABLE, type Skill, type SkillFs, type SkillIndex } from "./types";

const FRONTMATTER = /^---\r?\n([\s\S]*?)\r?\n---\r?\n?/;

/** Splits `---` YAML frontmatter from the Markdown body. A leading UTF-8 BOM is ignored. Never throws. */
export function splitFrontmatter(text: string): { data: Record<string, unknown> | null; body: string; error?: string } {
  if (text.startsWith("\uFEFF")) text = text.slice(1);
  const m = FRONTMATTER.exec(text);
  if (!m) return { data: null, body: text };
  const body = text.slice(m[0].length).replace(/^\s*\n/, "");
  try {
    const parsed = yaml.load(m[1]);
    if (parsed === null || parsed === undefined) return { data: {}, body };
    if (typeof parsed !== "object" || Array.isArray(parsed)) return { data: null, body, error: "frontmatter is not a mapping" };
    return { data: parsed as Record<string, unknown>, body };
  } catch (e) {
    return { data: null, body, error: (e as Error).message };
  }
}

export interface Catalog {
  load(root: string): Promise<SkillIndex>;
}

interface CacheEntry {
  index: SkillIndex;
  rootMtime: number;
  skillMdMtimes: Map<string, number>;
}

export function createCatalog(fs: SkillFs, log: (msg: string) => void = () => {}): Catalog {
  const cache = new Map<string, CacheEntry>();

  async function statMtime(p: string): Promise<number | null> {
    try {
      return (await fs.stat(p)).mtimeMs;
    } catch {
      return null;
    }
  }

  async function isFresh(entry: CacheEntry, root: string): Promise<boolean> {
    if ((await statMtime(root)) !== entry.rootMtime) return false;
    for (const [p, mtime] of entry.skillMdMtimes) {
      if ((await statMtime(p)) !== mtime) return false;
    }
    return true;
  }

  async function scan(root: string): Promise<CacheEntry> {
    const empty: SkillIndex = { root, skills: [], byName: new Map(), routable: [] };
    const rootMtime = await statMtime(root);
    if (rootMtime === null) return { index: empty, rootMtime: -1, skillMdMtimes: new Map() };

    let entries;
    try {
      entries = await fs.readdir(root);
    } catch {
      return { index: empty, rootMtime, skillMdMtimes: new Map() };
    }

    const skills: Skill[] = [];
    const skillMdMtimes = new Map<string, number>();
    const mtimeOf = new Map<string, number>();

    // Every entry is considered (not just `isDirectory`): a symlink to a directory reports
    // isDirectory=false, yet stat follows it, so `dir/SKILL.md` decides skill-or-not.
    for (const entry of [...entries].sort((a, b) => a.name.localeCompare(b.name))) {
      const dir = path.join(root, entry.name);
      const skillMdPath = path.join(dir, "SKILL.md");
      const mtime = await statMtime(skillMdPath);
      if (mtime === null) continue;
      skillMdMtimes.set(skillMdPath, mtime);
      mtimeOf.set(dir, mtime);

      let text: string;
      try {
        text = (await fs.readFile(skillMdPath)).toString("utf8");
      } catch (e) {
        log(`skills: ${skillMdPath}: SKILL.md unreadable (${(e as Error).message})`);
        skills.push({
          name: entry.name,
          description: "",
          dir,
          skillMdPath,
          disableModelInvocation: false,
          routable: false,
          note: "SKILL.md unreadable",
        });
        continue;
      }
      const fm = splitFrontmatter(text);
      const data = fm.data ?? {};
      const description = typeof data.description === "string" ? data.description.trim() : "";
      const disableModelInvocation = data["disable-model-invocation"] === true;

      const skill: Skill = {
        name: entry.name,
        description,
        dir,
        skillMdPath,
        disableModelInvocation,
        routable: !disableModelInvocation && description !== "",
      };
      const fmName = typeof data.name === "string" ? data.name.trim() : "";
      if (fmName !== "") {
        if (isValidSkillName(fmName)) {
          skill.name = fmName;
        } else {
          skill.note = "invalid name in frontmatter";
          log(`skills: ${skillMdPath}: invalid name in frontmatter (${JSON.stringify(fmName)}); using folder name`);
        }
      }
      if (!isValidSkillName(skill.name)) {
        skill.note = "name not activatable";
        skill.routable = false;
        log(`skills: ${skillMdPath}: folder name ${JSON.stringify(skill.name)} is not activatable`);
      }
      if (fm.error !== undefined) {
        skill.note = "frontmatter unreadable";
        skill.routable = false;
        log(`skills: ${skillMdPath}: frontmatter unreadable${fm.error ? ` (${fm.error})` : ""}`);
      }
      skills.push(skill);
    }

    const byName = new Map<string, Skill>();
    for (const skill of skills) {
      const existing = byName.get(skill.name);
      if (existing) {
        skill.routable = false;
        skill.note = `duplicate name, folder: ${skill.dir}`;
      } else {
        byName.set(skill.name, skill);
      }
    }

    let routable = skills.filter(s => s.routable).sort((a, b) => (mtimeOf.get(b.dir) ?? 0) - (mtimeOf.get(a.dir) ?? 0));
    if (routable.length > MAX_ROUTABLE) {
      log(`skills: ${routable.length} routable skills; only the ${MAX_ROUTABLE} most recently modified will be routed`);
      routable = routable.slice(0, MAX_ROUTABLE);
    }

    return { index: { root, skills, byName, routable }, rootMtime, skillMdMtimes };
  }

  return {
    async load(root) {
      const cached = cache.get(root);
      if (cached && (await isFresh(cached, root))) return cached.index;
      const entry = await scan(root);
      cache.set(root, entry);
      return entry.index;
    },
  };
}

import * as yaml from "js-yaml";
import * as path from "path";
import { isValidSkillName } from "./activation";
import { MAX_ROUTABLE, type Skill, type SkillFs, type SkillIndex } from "./types";

const FRONTMATTER = /^---\r?\n([\s\S]*?)\r?\n---\r?\n?/;

/** Splits `---` YAML frontmatter from the Markdown body. A leading UTF-8 BOM is ignored. Never throws. */
export function splitFrontmatter(text: string): { data: Record<string, unknown> | null; body: string; error?: string } {
  if (text.startsWith("\uFEFF")) text = text.slice(1);
  const m = FRONTMATTER.exec(text);
  if (!m) return { data: null, body: text };
  const body = text.slice(m[0].length).replace(/^\s*\n/, "");
  try {
    const parsed = yaml.load(m[1]);
    if (parsed === null || parsed === undefined) return { data: {}, body };
    if (typeof parsed !== "object" || Array.isArray(parsed)) return { data: null, body, error: "frontmatter is not a mapping" };
    return { data: parsed as Record<string, unknown>, body };
  } catch (e) {
    return { data: null, body, error: (e as Error).message };
  }
}

export interface Catalog {
  load(root: string): Promise<SkillIndex>;
}

interface CacheEntry {
  index: SkillIndex;
  rootMtime: number;
  skillMdMtimes: Map<string, number>;
}

export function createCatalog(fs: SkillFs, log: (msg: string) => void = () => {}): Catalog {
  const cache = new Map<string, CacheEntry>();

  async function statMtime(p: string): Promise<number | null> {
    try {
      return (await fs.stat(p)).mtimeMs;
    } catch {
      return null;
    }
  }

  async function isFresh(entry: CacheEntry, root: string): Promise<boolean> {
    if ((await statMtime(root)) !== entry.rootMtime) return false;
    for (const [p, mtime] of entry.skillMdMtimes) {
      if ((await statMtime(p)) !== mtime) return false;
    }
    return true;
  }

  async function scan(root: string): Promise<CacheEntry> {
    const empty: SkillIndex = { root, skills: [], byName: new Map(), routable: [] };
    const rootMtime = await statMtime(root);
    if (rootMtime === null) return { index: empty, rootMtime: -1, skillMdMtimes: new Map() };

    let entries;
    try {
      entries = await fs.readdir(root);
    } catch {
      return { index: empty, rootMtime, skillMdMtimes: new Map() };
    }

    const skills: Skill[] = [];
    const skillMdMtimes = new Map<string, number>();
    const mtimeOf = new Map<string, number>();

    // Every entry is considered (not just `isDirectory`): a symlink to a directory reports
    // isDirectory=false, yet stat follows it, so `dir/SKILL.md` decides skill-or-not.
    for (const entry of [...entries].sort((a, b) => a.name.localeCompare(b.name))) {
      const dir = path.join(root, entry.name);
      const skillMdPath = path.join(dir, "SKILL.md");
      const mtime = await statMtime(skillMdPath);
      if (mtime === null) continue;
      skillMdMtimes.set(skillMdPath, mtime);
      mtimeOf.set(dir, mtime);

      let text: string;
      try {
        text = (await fs.readFile(skillMdPath)).toString("utf8");
      } catch (e) {
        log(`skills: ${skillMdPath}: SKILL.md unreadable (${(e as Error).message})`);
        skills.push({
          name: entry.name,
          description: "",
          dir,
          skillMdPath,
          disableModelInvocation: false,
          routable: false,
          note: "SKILL.md unreadable",
        });
        continue;
      }
      const fm = splitFrontmatter(text);
      const data = fm.data ?? {};
      const description = typeof data.description === "string" ? data.description.trim() : "";
      const disableModelInvocation = data["disable-model-invocation"] === true;

      const skill: Skill = {
        name: entry.name,
        description,
        dir,
        skillMdPath,
        disableModelInvocation,
        routable: !disableModelInvocation && description !== "",
      };
      const fmName = typeof data.name === "string" ? data.name.trim() : "";
      if (fmName !== "") {
        if (isValidSkillName(fmName)) {
          skill.name = fmName;
        } else {
          skill.note = "invalid name in frontmatter";
          log(`skills: ${skillMdPath}: invalid name in frontmatter (${JSON.stringify(fmName)}); using folder name`);
        }
      }
      if (!isValidSkillName(skill.name)) {
        skill.note = "name not activatable";
        skill.routable = false;
        log(`skills: ${skillMdPath}: folder name ${JSON.stringify(skill.name)} is not activatable`);
      }
      if (fm.error !== undefined) {
        skill.note = "frontmatter unreadable";
        skill.routable = false;
        log(`skills: ${skillMdPath}: frontmatter unreadable${fm.error ? ` (${fm.error})` : ""}`);
      }
      skills.push(skill);
    }

    const byName = new Map<string, Skill>();
    for (const skill of skills) {
      const existing = byName.get(skill.name);
      if (existing) {
        skill.routable = false;
        skill.note = `duplicate name, folder: ${skill.dir}`;
      } else {
        byName.set(skill.name, skill);
      }
    }

    let routable = skills.filter(s => s.routable).sort((a, b) => (mtimeOf.get(b.dir) ?? 0) - (mtimeOf.get(a.dir) ?? 0));
    if (routable.length > MAX_ROUTABLE) {
      log(`skills: ${routable.length} routable skills; only the ${MAX_ROUTABLE} most recently modified will be routed`);
      routable = routable.slice(0, MAX_ROUTABLE);
    }

    return { index: { root, skills, byName, routable }, rootMtime, skillMdMtimes };
  }

  return {
    async load(root) {
      const cached = cache.get(root);
      if (cached && (await isFresh(cached, root))) return cached.index;
      const entry = await scan(root);
      cache.set(root, entry);
      return entry.index;
    },
  };
}