import crypto from "node:crypto";
import { mkdir, writeFile } from "node:fs/promises";
import { existsSync } from "node:fs";
import path from "node:path";
import { eq } from "drizzle-orm";
import { getSkillRegistryDb, type SkillRegistryDb } from "./skill-registry-db.js";
import { skills, skillVersions, skillFiles, communityRatings } from "./skill-registry-schema.js";
import {
  fetchText,
  fetchJson,
  resolveGitHubCommitSha,
  resolveRawGitHubUrl,
} from "./github-skill-helpers.js";
import { resolveSkillCacheDir } from "../home-paths.js";

// ---------------------------------------------------------------------------
// Source config
// ---------------------------------------------------------------------------

export type SkillSourceConfig = {
  id: string;
  type: "anthropic-marketplace" | "github-tree";
  owner: string;
  repo: string;
  ref: string;
  label: string;
};

export const BUILT_IN_SOURCES: SkillSourceConfig[] = [
  {
    id: "anthropic-official",
    type: "anthropic-marketplace",
    owner: "anthropics",
    repo: "skills",
    ref: "main",
    label: "Anthropic Official",
  },
  {
    id: "schwepps-skills",
    type: "github-tree",
    owner: "schwepps",
    repo: "skills",
    ref: "main",
    label: "Schwepps Community",
  },
  {
    id: "daymade-skills",
    type: "github-tree",
    owner: "daymade",
    repo: "claude-code-skills",
    ref: "main",
    label: "Daymade Community",
  },
];

// ---------------------------------------------------------------------------
// Frontmatter parsing
// ---------------------------------------------------------------------------

/**
 * Parse YAML frontmatter from a SKILL.md string.
 * Only extracts `name` and `description` fields.
 */
export function parseSkillFrontmatter(markdown: string): {
  name?: string;
  description?: string;
} {
  const match = /^---\r?\n([\s\S]*?)\r?\n---/m.exec(markdown);
  if (!match) return {};

  const block = match[1] ?? "";
  const nameMatch = /^name:\s*(.+)$/m.exec(block);
  const descMatch = /^description:\s*(.+)$/m.exec(block);

  const name = nameMatch?.[1]?.trim();
  const description = descMatch?.[1]?.trim();

  return {
    name: name && name.length > 0 ? name : undefined,
    description: description && description.length > 0 ? description : undefined,
  };
}

/**
 * Convert a path segment to a URL-safe skill slug.
 * e.g. "My Skill Name" → "my-skill-name"
 */
export function slugFromPath(sourcePath: string): string {
  // Take the last non-empty path segment (the directory name of the skill)
  const parts = sourcePath.split("/").filter(Boolean);
  const segment = parts[parts.length - 1] ?? sourcePath;
  return segment
    .toLowerCase()
    .replace(/[^a-z0-9-]+/g, "-")
    .replace(/^-+|-+$/g, "");
}

// ---------------------------------------------------------------------------
// Core fetch helpers
// ---------------------------------------------------------------------------

type GitHubTreeEntry = {
  path: string;
  type: string;
  size?: number;
};

type GitHubTreeResponse = {
  tree: GitHubTreeEntry[];
};

type MarketplaceJson = {
  skills: Array<{ path: string }>;
};

/**
 * Upsert a skill row and return its id.
 */
async function upsertSkill(
  db: SkillRegistryDb,
  opts: {
    skillId: string;
    sourceId: string;
    name: string;
    description: string | undefined;
    sourceUrl: string;
  },
): Promise<void> {
  const now = Date.now();
  await db
    .insert(skills)
    .values({
      id: opts.skillId,
      sourceId: opts.sourceId,
      name: opts.name,
      description: opts.description ?? null,
      sourceUrl: opts.sourceUrl,
      activeVersionId: null,
      removedAt: null,
      createdAt: now,
      updatedAt: now,
    })
    .onConflictDoUpdate({
      target: skills.id,
      set: {
        name: opts.name,
        description: opts.description ?? null,
        updatedAt: now,
      },
    });
}

/**
 * Upsert a stub community_ratings row for a skill.
 * This ensures list() and getById() JOINs always find a row.
 * Real rating values are populated in v1.3 when community APIs are available.
 */
async function upsertCommunityRatingsStub(
  db: SkillRegistryDb,
  skillId: string,
  sourceId: string,
): Promise<void> {
  await db
    .insert(communityRatings)
    .values({
      id: `${skillId}@${sourceId}`,
      skillId,
      fetchedAt: Date.now(),
      averageRating: null,
      ratingCount: null,
      source: sourceId,
    })
    .onConflictDoUpdate({
      target: communityRatings.id,
      set: {
        fetchedAt: Date.now(),
        averageRating: null,
        ratingCount: null,
      },
    });
}

/**
 * Check whether a version with this SHA already exists in the DB.
 * Returns true if already present (skip download).
 */
async function versionExists(db: SkillRegistryDb, versionId: string): Promise<boolean> {
  const existing = await db
    .select({ id: skillVersions.id })
    .from(skillVersions)
    .where(eq(skillVersions.id, versionId));
  return existing.length > 0;
}

/**
 * Cache SKILL.md to disk and insert skill_versions + skill_files rows.
 */
async function cacheSkillVersion(
  db: SkillRegistryDb,
  opts: {
    skillId: string;
    sha: string;
    skillMdContent: string;
    skillMdUrl: string;
  },
): Promise<void> {
  const versionId = `${opts.skillId}@${opts.sha}`;

  // Idempotency check — skip if version already cached
  if (await versionExists(db, versionId)) {
    return;
  }

  const cacheDir = resolveSkillCacheDir(opts.skillId, opts.sha);
  await mkdir(cacheDir, { recursive: true });

  const skillMdPath = path.join(cacheDir, "SKILL.md");
  await writeFile(skillMdPath, opts.skillMdContent, "utf-8");

  const now = Date.now();

  // Insert skill_versions row
  await db.insert(skillVersions).values({
    id: versionId,
    skillId: opts.skillId,
    version: opts.sha,
    fetchedAt: now,
    cacheDir,
  });

  // Insert skill_files row for SKILL.md
  const sizeBytes = Buffer.byteLength(opts.skillMdContent, "utf-8");
  await db.insert(skillFiles).values({
    id: crypto.randomUUID(),
    versionId,
    path: "SKILL.md",
    kind: "skill",
    sizeBytes,
  });
}

// ---------------------------------------------------------------------------
// Source-type handlers
// ---------------------------------------------------------------------------

async function fetchAnthropicMarketplace(
  source: SkillSourceConfig,
  db: SkillRegistryDb,
): Promise<number> {
  const marketplaceUrl = resolveRawGitHubUrl(
    source.owner,
    source.repo,
    source.ref,
    ".claude-plugin/marketplace.json",
  );

  const marketplaceText = await fetchText(marketplaceUrl);
  const marketplace: MarketplaceJson = JSON.parse(marketplaceText);
  const sha = await resolveGitHubCommitSha(source.owner, source.repo, source.ref);

  let fetched = 0;

  for (const entry of marketplace.skills ?? []) {
    const skillPath = entry.path;
    const slug = slugFromPath(skillPath);
    const skillId = `${source.id}/${slug}`;

    // Idempotency check before downloading — skip if version already cached
    const versionId = `${skillId}@${sha}`;
    if (await versionExists(db, versionId)) {
      fetched++;
      continue;
    }

    const skillMdUrl = resolveRawGitHubUrl(source.owner, source.repo, source.ref, `${skillPath}/SKILL.md`);
    let skillMdContent: string;
    try {
      skillMdContent = await fetchText(skillMdUrl);
    } catch {
      // Skip skills that don't have a SKILL.md
      continue;
    }

    const { name, description } = parseSkillFrontmatter(skillMdContent);
    const sourceUrl = `https://github.com/${source.owner}/${source.repo}/tree/${source.ref}/${skillPath}`;

    await upsertSkill(db, {
      skillId,
      sourceId: source.id,
      name: name ?? slug,
      description,
      sourceUrl,
    });

    await cacheSkillVersion(db, {
      skillId,
      sha,
      skillMdContent,
      skillMdUrl,
    });

    await upsertCommunityRatingsStub(db, skillId, source.id);

    fetched++;
  }

  return fetched;
}

async function fetchGitHubTree(
  source: SkillSourceConfig,
  db: SkillRegistryDb,
): Promise<number> {
  const treeUrl = `https://api.github.com/repos/${source.owner}/${source.repo}/git/trees/${encodeURIComponent(source.ref)}?recursive=1`;
  const treeResponse = await fetchJson<GitHubTreeResponse>(treeUrl);

  const sha = await resolveGitHubCommitSha(source.owner, source.repo, source.ref);

  // Find all SKILL.md files
  const skillMdEntries = (treeResponse.tree ?? []).filter(
    (entry) => entry.type === "blob" && entry.path.endsWith("SKILL.md"),
  );

  let fetched = 0;

  for (const entry of skillMdEntries) {
    // entry.path is like "code-review/SKILL.md" — dirname is the skill dir
    const skillDir = path.posix.dirname(entry.path);
    if (!skillDir || skillDir === ".") continue;

    const slug = slugFromPath(skillDir);
    const skillId = `${source.id}/${slug}`;

    // Idempotency check before downloading — skip if version already cached
    const versionId = `${skillId}@${sha}`;
    if (await versionExists(db, versionId)) {
      fetched++;
      continue;
    }

    const skillMdUrl = resolveRawGitHubUrl(source.owner, source.repo, source.ref, entry.path);
    let skillMdContent: string;
    try {
      skillMdContent = await fetchText(skillMdUrl);
    } catch {
      continue;
    }

    const { name, description } = parseSkillFrontmatter(skillMdContent);
    const sourceUrl = `https://github.com/${source.owner}/${source.repo}/tree/${source.ref}/${skillDir}`;

    await upsertSkill(db, {
      skillId,
      sourceId: source.id,
      name: name ?? slug,
      description,
      sourceUrl,
    });

    await cacheSkillVersion(db, {
      skillId,
      sha,
      skillMdContent,
      skillMdUrl,
    });

    await upsertCommunityRatingsStub(db, skillId, source.id);

    fetched++;
  }

  return fetched;
}

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

export type FetchAllSourcesResult = {
  fetched: number;
  errors: string[];
};

/**
 * Fetch skills from all configured sources and populate the registry DB.
 * Uses BUILT_IN_SOURCES if no sources are provided.
 */
export async function fetchAllSources(
  sources: SkillSourceConfig[] = BUILT_IN_SOURCES,
): Promise<FetchAllSourcesResult> {
  const db = await getSkillRegistryDb();
  let fetched = 0;
  const errors: string[] = [];

  for (const source of sources) {
    try {
      if (source.type === "anthropic-marketplace") {
        fetched += await fetchAnthropicMarketplace(source, db);
      } else if (source.type === "github-tree") {
        fetched += await fetchGitHubTree(source, db);
      } else {
        errors.push(`Unknown source type for ${source.id}`);
      }
    } catch (err) {
      const message = err instanceof Error ? err.message : String(err);
      errors.push(`Source ${source.id}: ${message}`);
    }
  }

  return { fetched, errors };
}