import fs from "node:fs/promises";
import path from "node:path";

import { runCommandWithTimeout } from "../process/exec.js";
import { parseSemver } from "./runtime-guard.js";

export type PackageManager = "pnpm" | "bun" | "npm" | "unknown";

export type GitUpdateStatus = {
  root: string;
  branch: string | null;
  upstream: string | null;
  dirty: boolean | null;
  ahead: number | null;
  behind: number | null;
  fetchOk: boolean | null;
  error?: string;
};

export type DepsStatus = {
  manager: PackageManager;
  status: "ok" | "missing" | "stale" | "unknown";
  lockfilePath: string | null;
  markerPath: string | null;
  reason?: string;
};

export type RegistryStatus = {
  latestVersion: string | null;
  error?: string;
};

export type UpdateCheckResult = {
  root: string | null;
  installKind: "git" | "package" | "unknown";
  packageManager: PackageManager;
  git?: GitUpdateStatus;
  deps?: DepsStatus;
  registry?: RegistryStatus;
};

async function exists(p: string): Promise<boolean> {
  try {
    await fs.access(p);
    return true;
  } catch {
    return false;
  }
}

async function detectPackageManager(root: string): Promise<PackageManager> {
  try {
    const raw = await fs.readFile(path.join(root, "package.json"), "utf-8");
    const parsed = JSON.parse(raw) as { packageManager?: string };
    const pm = parsed?.packageManager?.split("@")[0]?.trim();
    if (pm === "pnpm" || pm === "bun" || pm === "npm") return pm;
  } catch {
    // ignore
  }

  const files = await fs.readdir(root).catch((): string[] => []);
  if (files.includes("pnpm-lock.yaml")) return "pnpm";
  if (files.includes("bun.lockb")) return "bun";
  if (files.includes("package-lock.json")) return "npm";
  return "unknown";
}

async function detectGitRoot(root: string): Promise<string | null> {
  const res = await runCommandWithTimeout(
    ["git", "-C", root, "rev-parse", "--show-toplevel"],
    { timeoutMs: 4000 },
  ).catch(() => null);
  if (!res || res.code !== 0) return null;
  const top = res.stdout.trim();
  return top ? path.resolve(top) : null;
}

export async function checkGitUpdateStatus(params: {
  root: string;
  timeoutMs?: number;
  fetch?: boolean;
}): Promise<GitUpdateStatus> {
  const timeoutMs = params.timeoutMs ?? 6000;
  const root = path.resolve(params.root);

  const base: GitUpdateStatus = {
    root,
    branch: null,
    upstream: null,
    dirty: null,
    ahead: null,
    behind: null,
    fetchOk: null,
  };

  const branchRes = await runCommandWithTimeout(
    ["git", "-C", root, "rev-parse", "--abbrev-ref", "HEAD"],
    { timeoutMs },
  ).catch(() => null);
  if (!branchRes || branchRes.code !== 0) {
    return { ...base, error: branchRes?.stderr?.trim() || "git unavailable" };
  }
  const branch = branchRes.stdout.trim() || null;

  const upstreamRes = await runCommandWithTimeout(
    ["git", "-C", root, "rev-parse", "--abbrev-ref", "@{upstream}"],
    { timeoutMs },
  ).catch(() => null);
  const upstream =
    upstreamRes && upstreamRes.code === 0 ? upstreamRes.stdout.trim() : null;

  const dirtyRes = await runCommandWithTimeout(
    ["git", "-C", root, "status", "--porcelain"],
    { timeoutMs },
  ).catch(() => null);
  const dirty =
    dirtyRes && dirtyRes.code === 0 ? dirtyRes.stdout.trim().length > 0 : null;

  const fetchOk = params.fetch
    ? await runCommandWithTimeout(
        ["git", "-C", root, "fetch", "--quiet", "--prune"],
        { timeoutMs },
      )
        .then((r) => r.code === 0)
        .catch(() => false)
    : null;

  const counts =
    upstream && upstream.length > 0
      ? await runCommandWithTimeout(
          [
            "git",
            "-C",
            root,
            "rev-list",
            "--left-right",
            "--count",
            `HEAD...${upstream}`,
          ],
          { timeoutMs },
        ).catch(() => null)
      : null;

  const parseCounts = (
    raw: string,
  ): { ahead: number; behind: number } | null => {
    const parts = raw.trim().split(/\s+/);
    if (parts.length < 2) return null;
    const ahead = Number.parseInt(parts[0] ?? "", 10);
    const behind = Number.parseInt(parts[1] ?? "", 10);
    if (!Number.isFinite(ahead) || !Number.isFinite(behind)) return null;
    return { ahead, behind };
  };
  const parsed =
    counts && counts.code === 0 ? parseCounts(counts.stdout) : null;

  return {
    root,
    branch,
    upstream,
    dirty,
    ahead: parsed?.ahead ?? null,
    behind: parsed?.behind ?? null,
    fetchOk,
  };
}

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

function resolveDepsMarker(params: { root: string; manager: PackageManager }): {
  lockfilePath: string | null;
  markerPath: string | null;
} {
  const root = params.root;
  if (params.manager === "pnpm") {
    return {
      lockfilePath: path.join(root, "pnpm-lock.yaml"),
      markerPath: path.join(root, "node_modules", ".modules.yaml"),
    };
  }
  if (params.manager === "bun") {
    return {
      lockfilePath: path.join(root, "bun.lockb"),
      markerPath: path.join(root, "node_modules"),
    };
  }
  if (params.manager === "npm") {
    return {
      lockfilePath: path.join(root, "package-lock.json"),
      markerPath: path.join(root, "node_modules"),
    };
  }
  return { lockfilePath: null, markerPath: null };
}

export async function checkDepsStatus(params: {
  root: string;
  manager: PackageManager;
}): Promise<DepsStatus> {
  const root = path.resolve(params.root);
  const { lockfilePath, markerPath } = resolveDepsMarker({
    root,
    manager: params.manager,
  });

  if (!lockfilePath || !markerPath) {
    return {
      manager: params.manager,
      status: "unknown",
      lockfilePath,
      markerPath,
      reason: "unknown package manager",
    };
  }

  const lockExists = await exists(lockfilePath);
  const markerExists = await exists(markerPath);
  if (!lockExists) {
    return {
      manager: params.manager,
      status: "unknown",
      lockfilePath,
      markerPath,
      reason: "lockfile missing",
    };
  }
  if (!markerExists) {
    return {
      manager: params.manager,
      status: "missing",
      lockfilePath,
      markerPath,
      reason: "node_modules marker missing",
    };
  }

  const lockMtime = await statMtimeMs(lockfilePath);
  const markerMtime = await statMtimeMs(markerPath);
  if (!lockMtime || !markerMtime) {
    return {
      manager: params.manager,
      status: "unknown",
      lockfilePath,
      markerPath,
    };
  }
  if (lockMtime > markerMtime + 1000) {
    return {
      manager: params.manager,
      status: "stale",
      lockfilePath,
      markerPath,
      reason: "lockfile newer than install marker",
    };
  }
  return {
    manager: params.manager,
    status: "ok",
    lockfilePath,
    markerPath,
  };
}

async function fetchWithTimeout(
  url: string,
  timeoutMs: number,
): Promise<Response> {
  const ctrl = new AbortController();
  const t = setTimeout(() => ctrl.abort(), Math.max(250, timeoutMs));
  try {
    return await fetch(url, { signal: ctrl.signal });
  } finally {
    clearTimeout(t);
  }
}

export async function fetchNpmLatestVersion(params?: {
  timeoutMs?: number;
}): Promise<RegistryStatus> {
  const timeoutMs = params?.timeoutMs ?? 3500;
  try {
    const res = await fetchWithTimeout(
      "https://registry.npmjs.org/clawdbot/latest",
      timeoutMs,
    );
    if (!res.ok) {
      return { latestVersion: null, error: `HTTP ${res.status}` };
    }
    const json = (await res.json()) as { version?: unknown };
    const latestVersion =
      typeof json?.version === "string" ? json.version : null;
    return { latestVersion };
  } catch (err) {
    return { latestVersion: null, error: String(err) };
  }
}

export function compareSemverStrings(
  a: string | null,
  b: string | null,
): number | null {
  const pa = parseSemver(a);
  const pb = parseSemver(b);
  if (!pa || !pb) return null;
  if (pa.major !== pb.major) return pa.major < pb.major ? -1 : 1;
  if (pa.minor !== pb.minor) return pa.minor < pb.minor ? -1 : 1;
  if (pa.patch !== pb.patch) return pa.patch < pb.patch ? -1 : 1;
  return 0;
}

export async function checkUpdateStatus(params: {
  root: string | null;
  timeoutMs?: number;
  fetchGit?: boolean;
  includeRegistry?: boolean;
}): Promise<UpdateCheckResult> {
  const timeoutMs = params.timeoutMs ?? 6000;
  const root = params.root ? path.resolve(params.root) : null;
  if (!root) {
    return {
      root: null,
      installKind: "unknown",
      packageManager: "unknown",
      registry: params.includeRegistry
        ? await fetchNpmLatestVersion({ timeoutMs })
        : undefined,
    };
  }

  const pm = await detectPackageManager(root);
  const gitRoot = await detectGitRoot(root);
  const isGit = gitRoot && path.resolve(gitRoot) === root;

  const installKind: UpdateCheckResult["installKind"] = isGit
    ? "git"
    : "package";
  const git = isGit
    ? await checkGitUpdateStatus({
        root,
        timeoutMs,
        fetch: Boolean(params.fetchGit),
      })
    : undefined;
  const deps = await checkDepsStatus({ root, manager: pm });
  const registry = params.includeRegistry
    ? await fetchNpmLatestVersion({ timeoutMs })
    : undefined;

  return {
    root,
    installKind,
    packageManager: pm,
    git,
    deps,
    registry,
  };
}