/**
 * @fileoverview Server-side logic for the in-app self-updater.
 *
 * Powers App Settings → Updates. Codeman is installed as a git clone and run
 * under systemd (Linux) or launchd (macOS); updating means `git checkout <release
 * tag> && npm install && npm run build && restart-the-service`. The hard part is
 * that the update restarts the very process performing it, so the actual work
 * runs in a DETACHED `scripts/self-update.sh` that outlives the restart, writing
 * progress to `dataPath('update-status.json')` which the browser polls across the
 * connection drop.
 *
 * Channel: latest tagged RELEASE (tags look like `codeman@0.9.3`). Dirty trees
 * are auto-stashed (stash left for the user). Detection is manual (a button).
 *
 * Split into PURE helpers (semver/tag parsing, reconcile decision) that are unit
 * tested, and IO wrappers (`getInstallInfo`, `checkForUpdate`, `startUpdate`,
 * `reconcileUpdateOnBoot`) that touch git/network/fs.
 *
 * Related: `src/types/update.ts`, `scripts/self-update.sh`, routes in
 * `src/web/routes/system-routes.ts`.
 *
 * @module web/self-update
 */

import { spawn, execFileSync } from 'node:child_process';
import { existsSync, readFileSync, writeFileSync, renameSync, copyFileSync, chmodSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { homedir, tmpdir } from 'node:os';
import { randomUUID } from 'node:crypto';
import { createRequire } from 'node:module';
import { dataPath } from '../config/instance.js';
import { EXEC_TIMEOUT_MS } from '../config/exec-timeout.js';
import type {
  InstallInfo,
  InstallKind,
  SupervisorKind,
  UpdateCheckResult,
  UpdatePhase,
  UpdateStatus,
} from '../types/update.js';

const require = createRequire(import.meta.url);
const { version: APP_VERSION } = require('../../package.json') as { version: string };

/** systemd unit name (matches install.sh + scripts/codeman-web.service). */
const SYSTEMD_UNIT = 'codeman-web.service';
/** launchd agent label (matches install.sh setup_launchd_service). */
const LAUNCHD_LABEL = 'com.codeman.web';
/** Path to the persisted update status file. */
const STATUS_FILE = dataPath('update-status.json');
/** Network/git timeout for the "check" path (longer than EXEC_TIMEOUT_MS — ls-remote hits the network). */
const CHECK_TIMEOUT_MS = 12_000;
/** How long after `startedAt` a non-terminal status is treated as abandoned on boot. */
const RECONCILE_STALE_MS = 15 * 60 * 1000;

/** Phases that mean "an update is currently running". */
const IN_FLIGHT_PHASES: ReadonlySet<UpdatePhase> = new Set<UpdatePhase>([
  'queued',
  'preparing',
  'stashing',
  'fetching',
  'checkout',
  'installing',
  'building',
  'restarting',
]);

export function isInFlight(status: UpdateStatus | null | undefined): boolean {
  return !!status && IN_FLIGHT_PHASES.has(status.phase);
}

// ─────────────────────────────────────────────────────────────────────────────
// PURE helpers (unit tested — no IO)
// ─────────────────────────────────────────────────────────────────────────────

export interface ParsedVersion {
  major: number;
  minor: number;
  patch: number;
  /** Non-empty for prereleases like `0.9.3-rc1`. */
  prerelease: string;
}

/**
 * Parse a semver out of a release tag. Accepts `codeman@0.9.3`, `aicodeman@0.9.3`,
 * `v0.9.3`, and bare `0.9.3` (with optional `-prerelease`). Returns null if no
 * `X.Y.Z` is present.
 */
export function parseVersionFromTag(tag: string): ParsedVersion | null {
  const m = tag.trim().match(/(\d+)\.(\d+)\.(\d+)(?:-([0-9A-Za-z.-]+))?\s*$/);
  if (!m) return null;
  return {
    major: parseInt(m[1], 10),
    minor: parseInt(m[2], 10),
    patch: parseInt(m[3], 10),
    prerelease: m[4] ?? '',
  };
}

/** Compare two parsed versions. Returns >0 if a>b, <0 if a<b, 0 if equal. A release outranks a prerelease of the same X.Y.Z. */
export function compareVersions(a: ParsedVersion, b: ParsedVersion): number {
  if (a.major !== b.major) return a.major - b.major;
  if (a.minor !== b.minor) return a.minor - b.minor;
  if (a.patch !== b.patch) return a.patch - b.patch;
  // Equal core: a release (no prerelease) is greater than a prerelease.
  if (a.prerelease === b.prerelease) return 0;
  if (!a.prerelease) return 1;
  if (!b.prerelease) return -1;
  return a.prerelease < b.prerelease ? -1 : 1;
}

/** True when `latest` is a strictly newer STABLE version than `current`. */
export function isNewerStableVersion(current: string, latest: string): boolean {
  const c = parseVersionFromTag(current);
  const l = parseVersionFromTag(latest);
  if (!c || !l) return false;
  if (l.prerelease) return false; // never offer a prerelease as an update
  return compareVersions(l, c) > 0;
}

/**
 * From a list of `refs/tags/...` (or bare tag names), pick the highest STABLE
 * release tag we recognize. Skips prereleases and unrecognized tags.
 */
export function pickLatestStableTag(tagRefs: string[]): { tag: string; version: string } | null {
  let best: { tag: string; parsed: ParsedVersion } | null = null;
  for (const raw of tagRefs) {
    // Accept `refs/tags/codeman@0.9.3`, dereferenced `...^{}`, or bare tag names.
    const tag = raw
      .replace(/^.*refs\/tags\//, '')
      .replace(/\^\{\}$/, '')
      .trim();
    if (!tag) continue;
    if (!/^(codeman|aicodeman)@\d+\.\d+\.\d+$/.test(tag) && !/^v?\d+\.\d+\.\d+$/.test(tag)) continue;
    const parsed = parseVersionFromTag(tag);
    if (!parsed || parsed.prerelease) continue;
    if (!best || compareVersions(parsed, best.parsed) > 0) {
      best = { tag, parsed };
    }
  }
  if (!best) return null;
  return { tag: best.tag, version: `${best.parsed.major}.${best.parsed.minor}.${best.parsed.patch}` };
}

/** Tags must match this before they're ever passed to the shell. */
export function isValidReleaseTag(tag: string): boolean {
  return /^(codeman|aicodeman)@\d+\.\d+\.\d+$/.test(tag);
}

/** Derive `{owner, repo}` from a GitHub SSH or HTTPS remote URL. */
export function parseGitHubRepo(remoteUrl: string): { owner: string; repo: string } | null {
  const m = remoteUrl.trim().match(/github\.com[:/]+([^/]+)\/(.+?)(?:\.git)?\/?$/);
  if (!m) return null;
  return { owner: m[1], repo: m[2] };
}

/**
 * PURE boot-time reconcile decision. Given the persisted status, the version the
 * freshly-booted process is actually running, and `now`, return the status to
 * persist — or null to leave it untouched.
 *
 * Rules (see plan "Hardening"):
 * - Terminal phases → untouched, EXCEPT `completed-needs-manual-restart`: once we
 *   boot into the staged target version the manual restart evidently happened, so
 *   it flips to `completed` (otherwise the stale instruction lingers in the UI).
 * - Only the `restarting` marker (written right before the updater triggers our
 *   restart) flips to completed/failed by comparing running version vs. target.
 * - Other in-flight phases are owned by the still-running updater scope — leave
 *   them alone so a normal/crash restart mid-update isn't misreported.
 * - A backstop staleness guard fails any in-flight status older than the window.
 */
export function reconcileStatusDecision(
  status: UpdateStatus | null,
  runningVersion: string,
  now: number
): UpdateStatus | null {
  if (!status) return null;

  // A staged update that asked for a manual restart: if we're now running the
  // target version, the user (or supervisor) did restart — mark it completed so
  // the UI stops showing the stale "restart Codeman to apply" instruction.
  if (status.phase === 'completed-needs-manual-restart') {
    if (status.toVersion && runningVersion === status.toVersion) {
      return { ...status, phase: 'completed', message: `Updated to v${runningVersion}`, updatedAt: now };
    }
    return null;
  }

  if (!IN_FLIGHT_PHASES.has(status.phase)) return null;

  if (status.phase === 'restarting') {
    if (status.toVersion && runningVersion === status.toVersion) {
      return { ...status, phase: 'completed', message: `Updated to v${runningVersion}`, updatedAt: now };
    }
    return {
      ...status,
      phase: 'failed',
      message: 'Restarted but version did not change',
      error: `expected ${status.toVersion ?? '?'}, running ${runningVersion}`,
      updatedAt: now,
    };
  }

  // Not the restart marker: only intervene if clearly abandoned.
  if (now - status.startedAt > RECONCILE_STALE_MS) {
    return {
      ...status,
      phase: 'failed',
      message: 'Update did not complete',
      error: `abandoned during "${status.phase}"`,
      updatedAt: now,
    };
  }
  return null;
}

// ─────────────────────────────────────────────────────────────────────────────
// Status file IO
// ─────────────────────────────────────────────────────────────────────────────

/** Read the persisted status; tolerant of a missing/torn file (returns null). */
export function readUpdateStatus(): UpdateStatus | null {
  try {
    if (!existsSync(STATUS_FILE)) return null;
    return JSON.parse(readFileSync(STATUS_FILE, 'utf-8')) as UpdateStatus;
  } catch {
    return null;
  }
}

/** Write the status atomically (temp + rename — readers never see a torn file). */
export function writeUpdateStatusAtomic(status: UpdateStatus): void {
  const tmp = `${STATUS_FILE}.tmp-${process.pid}`;
  writeFileSync(tmp, JSON.stringify(status, null, 2));
  renameSync(tmp, STATUS_FILE);
}

/** Reconcile the status file on server boot (call once, early in start()). */
export function reconcileUpdateOnBoot(now = Date.now()): void {
  const status = readUpdateStatus();
  const next = reconcileStatusDecision(status, APP_VERSION, now);
  if (next) writeUpdateStatusAtomic(next);
}

// ─────────────────────────────────────────────────────────────────────────────
// Environment probing (git / supervisor / install kind)
// ─────────────────────────────────────────────────────────────────────────────

/** Run a command, returning trimmed stdout, or null on any error. */
function tryExec(cmd: string, args: string[], cwd?: string, timeout = EXEC_TIMEOUT_MS): string | null {
  try {
    return execFileSync(cmd, args, { cwd, encoding: 'utf-8', timeout, stdio: ['ignore', 'pipe', 'ignore'] }).trim();
  } catch {
    return null;
  }
}

function commandExists(cmd: string): boolean {
  return tryExec('sh', ['-c', `command -v ${cmd}`]) !== null;
}

/**
 * Resolve the repo root from this module's location. Compiled to
 * `dist/web/self-update.js` (or `src/web/self-update.ts` under tsx) → two levels
 * up is the package root that holds `package.json` and `.git`. Matches the
 * `require('../../package.json')` resolution in `server.ts`.
 */
export function resolveInstallDir(): string {
  const moduleDir = dirname(fileURLToPath(import.meta.url));
  const root = join(moduleDir, '..', '..');
  if (existsSync(join(root, 'package.json'))) return root;
  return process.cwd();
}

function detectInstallKind(dir: string): InstallKind {
  if (existsSync(join(dir, '.git'))) return 'git';
  // Global npm install ships only dist/ (no src/, no .git).
  if (!existsSync(join(dir, 'src'))) return 'npm';
  return 'unknown';
}

/**
 * Detect which init system supervises us. Detection happens HERE (in the running
 * server, which has a rich env) and the result is passed to the updater script —
 * the detached child must not re-probe with a stripped-down environment.
 */
export function detectSupervisor(): SupervisorKind {
  if (process.platform === 'darwin') {
    if (existsSync(join(homedir(), 'Library', 'LaunchAgents', `${LAUNCHD_LABEL}.plist`))) return 'launchd';
    // Headless Macs (no GUI login → no gui domain) run Codeman as a system-level
    // LaunchDaemon instead. Restarting one needs no root IF it has KeepAlive: the
    // updater just kills the server and launchd respawns it on the new build. Only
    // claim this supervisor when the daemon is actually bootstrapped and KeepAlive.
    const daemonPlist = join('/Library/LaunchDaemons', `${LAUNCHD_LABEL}.plist`);
    if (existsSync(daemonPlist)) {
      const loaded = tryExec('launchctl', ['print', `system/${LAUNCHD_LABEL}`]) !== null;
      const keepAlive = tryExec('plutil', ['-extract', 'KeepAlive', 'raw', '-o', '-', daemonPlist]);
      if (loaded && keepAlive === 'true') return 'launchd-daemon';
    }
    return 'none';
  }
  if (process.platform === 'linux') {
    // INVOCATION_ID is set by systemd for service processes; confirm with is-active.
    if (process.env.INVOCATION_ID && tryExec('systemctl', ['--user', 'is-active', SYSTEMD_UNIT]) === 'active') {
      return 'systemd';
    }
    if (tryExec('systemctl', ['--user', 'is-active', SYSTEMD_UNIT]) === 'active') return 'systemd';
  }
  return 'none';
}

function isSelfUpdateEnabled(): boolean {
  return process.env.CODEMAN_DISABLE_SELF_UPDATE !== '1';
}

/** Inspect the running install: kind, dir, branch, dirtiness, supervisor, version. */
export function getInstallInfo(): InstallInfo {
  const installDir = resolveInstallDir();
  const installKind = detectInstallKind(installDir);
  let branch: string | undefined;
  let dirty = false;
  if (installKind === 'git') {
    branch = tryExec('git', ['rev-parse', '--abbrev-ref', 'HEAD'], installDir) ?? undefined;
    const porcelain = tryExec('git', ['status', '--porcelain'], installDir);
    dirty = !!porcelain && porcelain.length > 0;
  }
  return {
    installKind,
    installDir,
    branch,
    dirty,
    supervisor: detectSupervisor(),
    currentVersion: APP_VERSION,
    selfUpdateEnabled: isSelfUpdateEnabled(),
  };
}

// ─────────────────────────────────────────────────────────────────────────────
// Update check (network)
// ─────────────────────────────────────────────────────────────────────────────

async function fetchLatestReleaseFromGitHub(
  owner: string,
  repo: string
): Promise<{ tag: string; version: string; notes: string | null; htmlUrl: string | null } | null> {
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), CHECK_TIMEOUT_MS);
  try {
    const res = await fetch(`https://api.github.com/repos/${owner}/${repo}/releases/latest`, {
      headers: { 'User-Agent': 'codeman-self-update', Accept: 'application/vnd.github+json' },
      signal: controller.signal,
    });
    if (!res.ok) return null;
    const data = (await res.json()) as { tag_name?: string; body?: string; html_url?: string };
    if (!data.tag_name) return null;
    const parsed = parseVersionFromTag(data.tag_name);
    if (!parsed || parsed.prerelease) return null;
    return {
      tag: data.tag_name,
      version: `${parsed.major}.${parsed.minor}.${parsed.patch}`,
      notes: data.body ?? null,
      htmlUrl: data.html_url ?? null,
    };
  } catch {
    return null;
  } finally {
    clearTimeout(timer);
  }
}

function fetchLatestTagViaGit(installDir: string): { tag: string; version: string } | null {
  const out = tryExec('git', ['ls-remote', '--tags', 'origin'], installDir, CHECK_TIMEOUT_MS);
  if (!out) return null;
  return pickLatestStableTag(out.split('\n').filter(Boolean));
}

/** Check the configured remote for a newer release than the running version. */
export async function checkForUpdate(): Promise<UpdateCheckResult> {
  const info = getInstallInfo();
  const checkedAt = Date.now();
  const base: UpdateCheckResult = {
    currentVersion: info.currentVersion,
    latestVersion: null,
    latestTag: null,
    updateAvailable: false,
    notes: null,
    htmlUrl: null,
    checkedAt,
    source: 'none',
  };
  if (info.installKind !== 'git') {
    return { ...base, error: 'Not a git install — self-update is unavailable.' };
  }

  const remote = tryExec('git', ['remote', 'get-url', 'origin'], info.installDir);
  const gh = remote ? parseGitHubRepo(remote) : null;

  if (gh) {
    const rel = await fetchLatestReleaseFromGitHub(gh.owner, gh.repo);
    if (rel) {
      return {
        ...base,
        latestVersion: rel.version,
        latestTag: rel.tag,
        notes: rel.notes,
        htmlUrl: rel.htmlUrl,
        updateAvailable: isNewerStableVersion(info.currentVersion, rel.version),
        source: 'github-api',
      };
    }
  }

  // Fallback: enumerate remote tags directly (works for non-GitHub remotes too).
  const viaGit = fetchLatestTagViaGit(info.installDir);
  if (viaGit) {
    return {
      ...base,
      latestVersion: viaGit.version,
      latestTag: viaGit.tag,
      updateAvailable: isNewerStableVersion(info.currentVersion, viaGit.version),
      source: 'git-ls-remote',
    };
  }

  return { ...base, error: 'Could not reach the update server (GitHub API + git ls-remote both failed).' };
}

// ─────────────────────────────────────────────────────────────────────────────
// Start an update
// ─────────────────────────────────────────────────────────────────────────────

export type StartUpdateResult =
  | { ok: true; updateId: string; toTag: string; toVersion: string | null }
  | { ok: false; code: 'disabled' | 'not-git' | 'in-flight' | 'up-to-date' | 'bad-tag' | 'error'; message: string };

/**
 * Copy the updater script OUT of the repo before running it. The script lives in
 * the very repo it's about to `git checkout`, and bash reads scripts lazily — so
 * running the in-repo copy risks executing torn/old-tag bytes after checkout.
 * Run a snapshot under ~/.codeman instead (git never touches it).
 */
function stageRunner(installDir: string): string | null {
  const src = join(installDir, 'scripts', 'self-update.sh');
  if (!existsSync(src)) return null;
  const runner = dataPath('self-update-runner.sh');
  copyFileSync(src, runner);
  chmodSync(runner, 0o755);
  return runner;
}

/**
 * Launch the updater so it OUTLIVES the service restart it triggers.
 * - Linux + systemd: a transient `--scope` cgroup, independent of the
 *   codeman-web service lifecycle (survives `systemctl restart` regardless of
 *   the unit's KillMode). Inherits our env so node/npm/git stay on PATH.
 * - Everything else: `setsid` into a new session (escapes launchd's process-group
 *   kill); plain detached spawn as the last resort.
 */
function launchDetached(runner: string, args: string[]): void {
  const useScope = process.platform === 'linux' && !!process.env.XDG_RUNTIME_DIR && commandExists('systemd-run');
  let cmd: string;
  let cmdArgs: string[];
  if (useScope) {
    cmd = 'systemd-run';
    cmdArgs = ['--user', '--scope', '--collect', '--quiet', 'bash', runner, ...args];
  } else if (commandExists('setsid')) {
    cmd = 'setsid';
    cmdArgs = ['bash', runner, ...args];
  } else {
    cmd = 'bash';
    cmdArgs = [runner, ...args];
  }
  const child = spawn(cmd, cmdArgs, { detached: true, stdio: 'ignore', env: process.env });
  child.on('error', () => {
    // Surface the failure in the status file so the UI doesn't hang on "queued".
    const status = readUpdateStatus();
    if (status && isInFlight(status)) {
      writeUpdateStatusAtomic({
        ...status,
        phase: 'failed',
        message: 'Could not launch the updater process',
        error: `spawn ${cmd} failed`,
        updatedAt: Date.now(),
      });
    }
  });
  child.unref();
}

/**
 * Validate, snapshot the current commit, write the initial status, and spawn the
 * detached updater. Returns immediately — progress is reported via the status file.
 */
export async function startUpdate(): Promise<StartUpdateResult> {
  const info = getInstallInfo();
  if (!info.selfUpdateEnabled) {
    return { ok: false, code: 'disabled', message: 'Self-update is disabled (CODEMAN_DISABLE_SELF_UPDATE=1).' };
  }
  if (info.installKind !== 'git') {
    return {
      ok: false,
      code: 'not-git',
      message: 'This is not a git install. Update with: npm i -g aicodeman@latest',
    };
  }
  const existing = readUpdateStatus();
  if (isInFlight(existing)) {
    return { ok: false, code: 'in-flight', message: 'An update is already in progress.' };
  }

  const check = await checkForUpdate();
  if (!check.latestTag || !check.updateAvailable) {
    return { ok: false, code: 'up-to-date', message: 'Already up to date.' };
  }
  if (!isValidReleaseTag(check.latestTag)) {
    return { ok: false, code: 'bad-tag', message: `Refusing to update to an unrecognized tag: ${check.latestTag}` };
  }

  const prevSha = tryExec('git', ['rev-parse', 'HEAD'], info.installDir);
  const runner = stageRunner(info.installDir);
  if (!runner) {
    return { ok: false, code: 'error', message: 'scripts/self-update.sh not found in the install.' };
  }

  const updateId = randomUUID();
  const now = Date.now();
  const status: UpdateStatus = {
    updateId,
    phase: 'queued',
    message: `Preparing update to v${check.latestVersion}…`,
    fromVersion: info.currentVersion,
    toVersion: check.latestVersion ?? undefined,
    toTag: check.latestTag,
    prevSha: prevSha ?? undefined,
    stashRef: null,
    supervisor: info.supervisor,
    startedAt: now,
    updatedAt: now,
  };
  writeUpdateStatusAtomic(status);

  const logFile = join(tmpdir(), `codeman-update-${updateId}.log`);
  const args = [
    '--repo',
    info.installDir,
    '--tag',
    check.latestTag,
    '--supervisor',
    info.supervisor,
    '--status-file',
    STATUS_FILE,
    '--update-id',
    updateId,
    '--from-version',
    info.currentVersion,
    '--node',
    process.execPath,
    '--log',
    logFile,
    // For the launchd-daemon restart path: the updater kills this PID and the
    // KeepAlive daemon respawns the server on the freshly built dist/.
    '--server-pid',
    String(process.pid),
  ];
  if (prevSha) args.push('--prev-sha', prevSha);
  if (info.dirty) args.push('--stash');

  launchDetached(runner, args);
  return { ok: true, updateId, toTag: check.latestTag, toVersion: check.latestVersion };
}

/** Current status for the polling endpoint; null collapses to an explicit idle. */
export function getUpdateStatusForApi(): UpdateStatus {
  const status = readUpdateStatus();
  if (status) return status;
  return {
    updateId: '',
    phase: 'idle',
    message: '',
    fromVersion: APP_VERSION,
    startedAt: 0,
    updatedAt: 0,
  };
}