#!/usr/bin/env bun
// gstack-next-version — host-aware VERSION allocator for /ship.
//
// Queries the PR queue (GitHub or GitLab), fetches each open PR's VERSION,
// scans configurable Conductor sibling worktrees, picks the next free version
// slot at the requested bump level, and emits the whole picture as JSON.
//
// Contract: util NEVER writes files or mutates state. Pure reader + reporter.
// /ship consumes the JSON and decides what to do.
//
// Usage:
//   gstack-next-version --base <branch> --bump <major|minor|patch|micro> \
//     --current-version <X.Y.Z.W> [--workspace-root <path>|null] [--json]
//
// Exit codes:
//   0 — emitted JSON successfully (may include "offline":true or "host":"unknown")
//   2 — invalid arguments
//   3 — util bug (unexpected exception)

import { execFileSync, spawnSync } from "node:child_process";
import { existsSync, readFileSync, readdirSync, statSync } from "node:fs";
import { homedir } from "node:os";
import { join, resolve } from "node:path";

type Bump = "major" | "minor" | "patch" | "micro";
type Version = [number, number, number, number];

type ClaimedPR = {
  pr: number;
  branch: string;
  version: string;
  url?: string;
};

type Sibling = {
  path: string;
  branch: string;
  version: string;
  last_commit_ts: number;
  has_open_pr: boolean;
  is_active: boolean;
};

type Output = {
  version: string;
  current_version: string;
  base_version: string;
  bump: Bump;
  host: "github" | "gitlab" | "unknown";
  offline: boolean;
  claimed: ClaimedPR[];
  siblings: Sibling[];
  active_siblings: Sibling[];
  reason: string;
  warnings: string[];
};

const ACTIVE_SIBLING_MAX_AGE_S = 24 * 60 * 60;
const GH_API_CONCURRENCY = 10;

function parseVersion(s: string): Version | null {
  const m = s.trim().match(/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/);
  if (!m) return null;
  return [Number(m[1]), Number(m[2]), Number(m[3]), Number(m[4])];
}

function fmtVersion(v: Version): string {
  return v.join(".");
}

function bumpVersion(v: Version, level: Bump): Version {
  switch (level) {
    case "major":
      return [v[0] + 1, 0, 0, 0];
    case "minor":
      return [v[0], v[1] + 1, 0, 0];
    case "patch":
      return [v[0], v[1], v[2] + 1, 0];
    case "micro":
      return [v[0], v[1], v[2], v[3] + 1];
  }
}

function cmpVersion(a: Version, b: Version): number {
  for (let i = 0; i < 4; i++) {
    if (a[i] !== b[i]) return a[i] - b[i];
  }
  return 0;
}

// Collision resolution: bump past the highest claimed within the same level.
// Semantics: if my bump is MINOR and the queue claims 1.7.0.0, I advance to
// 1.8.0.0 (still a MINOR relative to main). Preserves ship-time intent.
function pickNextSlot(base: Version, claimed: Version[], level: Bump): { version: Version; reason: string } {
  let candidate = bumpVersion(base, level);
  const sortedClaimed = [...claimed].sort(cmpVersion);
  const highest = sortedClaimed[sortedClaimed.length - 1];
  if (highest && cmpVersion(highest, base) > 0) {
    // Queue already advanced past base; bump past the highest claim.
    const bumpedPastHighest = bumpVersion(highest, level);
    if (cmpVersion(bumpedPastHighest, candidate) > 0) {
      return { version: bumpedPastHighest, reason: `bumped past claimed ${fmtVersion(highest)}` };
    }
  }
  return { version: candidate, reason: "no collision; clean bump from base" };
}

function runCommand(cmd: string, args: string[], timeoutMs = 15000): { ok: boolean; stdout: string; stderr: string } {
  const r = spawnSync(cmd, args, { encoding: "utf8", timeout: timeoutMs });
  return {
    ok: r.status === 0 && !r.error,
    stdout: r.stdout ?? "",
    stderr: r.stderr ?? (r.error ? String(r.error) : ""),
  };
}

function detectHost(): "github" | "gitlab" | "unknown" {
  const remote = runCommand("git", ["remote", "get-url", "origin"]);
  if (remote.ok) {
    const url = remote.stdout.trim();
    if (url.includes("github.com")) return "github";
    if (url.includes("gitlab")) return "gitlab";
  }
  const gh = runCommand("gh", ["auth", "status"]);
  if (gh.ok) return "github";
  const glab = runCommand("glab", ["auth", "status"]);
  if (glab.ok) return "gitlab";
  return "unknown";
}

function readBaseVersion(base: string, warnings: string[]): string {
  // git fetch is best-effort; we tolerate failure and fall back to whatever
  // origin/<base> currently points at.
  runCommand("git", ["fetch", "origin", base, "--quiet"], 10000);
  const r = runCommand("git", ["show", `origin/${base}:VERSION`]);
  if (!r.ok) {
    warnings.push(`could not read VERSION at origin/${base}; assuming 0.0.0.0`);
    return "0.0.0.0";
  }
  return r.stdout.trim();
}

async function fetchGithubClaimed(base: string, excludePR: number | null, warnings: string[]): Promise<{ claimed: ClaimedPR[]; offline: boolean }> {
  const list = runCommand("gh", [
    "pr",
    "list",
    "--state",
    "open",
    "--base",
    base,
    "--limit",
    "200",
    "--json",
    "number,headRefName,headRepositoryOwner,url,isDraft",
  ]);
  if (!list.ok) {
    warnings.push(`gh pr list failed: ${list.stderr.trim().slice(0, 200)}`);
    return { claimed: [], offline: true };
  }
  let prs: {
    number: number;
    headRefName: string;
    headRepositoryOwner?: { login: string };
    url: string;
    isDraft: boolean;
  }[];
  try {
    prs = JSON.parse(list.stdout);
  } catch (e) {
    warnings.push(`gh pr list returned invalid JSON`);
    return { claimed: [], offline: true };
  }
  // Determine our repo owner to filter out fork PRs. `gh api contents?ref=<branch>`
  // resolves to OUR repo regardless of where the PR originated, so fork PRs would
  // otherwise return our main's VERSION as a phantom claim.
  const viewer = runCommand("gh", ["repo", "view", "--json", "owner", "-q", ".owner.login"]);
  const myOwner = viewer.ok ? viewer.stdout.trim() : "";
  const sameRepoPRs = (myOwner
    ? prs.filter((p) => (p.headRepositoryOwner?.login ?? "") === myOwner)
    : prs
  ).filter((p) => excludePR === null || p.number !== excludePR);
  // Fetch each PR's VERSION at its head in parallel (bounded concurrency).
  const results: ClaimedPR[] = [];
  const queue = [...sameRepoPRs];
  const workers = Array.from({ length: Math.min(GH_API_CONCURRENCY, sameRepoPRs.length) }, async () => {
    while (queue.length) {
      const pr = queue.shift();
      if (!pr) return;
      // gh passes branch name via argv, not shell — safe.
      const content = runCommand("gh", [
        "api",
        `repos/{owner}/{repo}/contents/VERSION?ref=${encodeURIComponent(pr.headRefName)}`,
        "-q",
        ".content",
      ]);
      if (!content.ok) {
        warnings.push(`PR #${pr.number}: could not fetch VERSION (fork or private)`);
        continue;
      }
      let versionStr: string;
      try {
        versionStr = Buffer.from(content.stdout.trim(), "base64").toString("utf8").trim();
      } catch {
        warnings.push(`PR #${pr.number}: VERSION is not valid base64`);
        continue;
      }
      if (!parseVersion(versionStr)) {
        warnings.push(`PR #${pr.number}: VERSION is malformed (${versionStr})`);
        continue;
      }
      results.push({ pr: pr.number, branch: pr.headRefName, version: versionStr, url: pr.url });
    }
  });
  await Promise.all(workers);
  return { claimed: results, offline: false };
}

async function fetchGitlabClaimed(base: string, excludePR: number | null, warnings: string[]): Promise<{ claimed: ClaimedPR[]; offline: boolean }> {
  const list = runCommand("glab", [
    "mr",
    "list",
    "--opened",
    "--target-branch",
    base,
    "--output",
    "json",
    "--per-page",
    "200",
  ]);
  if (!list.ok) {
    warnings.push(`glab mr list failed: ${list.stderr.trim().slice(0, 200)}`);
    return { claimed: [], offline: true };
  }
  let mrs: { iid: number; source_branch: string; web_url: string }[];
  try {
    mrs = JSON.parse(list.stdout);
  } catch {
    warnings.push(`glab mr list returned invalid JSON`);
    return { claimed: [], offline: true };
  }
  if (excludePR !== null) {
    mrs = mrs.filter((mr) => mr.iid !== excludePR);
  }
  const results: ClaimedPR[] = [];
  for (const mr of mrs) {
    const content = runCommand("glab", [
      "api",
      `projects/:id/repository/files/VERSION?ref=${encodeURIComponent(mr.source_branch)}`,
    ]);
    if (!content.ok) {
      warnings.push(`MR !${mr.iid}: could not fetch VERSION`);
      continue;
    }
    try {
      const j = JSON.parse(content.stdout);
      const versionStr = Buffer.from(j.content, "base64").toString("utf8").trim();
      if (!parseVersion(versionStr)) {
        warnings.push(`MR !${mr.iid}: VERSION malformed (${versionStr})`);
        continue;
      }
      results.push({ pr: mr.iid, branch: mr.source_branch, version: versionStr, url: mr.web_url });
    } catch {
      warnings.push(`MR !${mr.iid}: unexpected glab api response`);
    }
  }
  return { claimed: results, offline: false };
}

function resolveWorkspaceRoot(override?: string): string | null {
  if (override === "null") return null;
  if (override) return override;
  const r = runCommand(join(__dirname, "gstack-config"), ["get", "workspace_root"]);
  const configured = r.ok ? r.stdout.trim() : "";
  if (configured === "null") return null;
  if (configured) return configured;
  // Default: $HOME/conductor/workspaces/
  return join(homedir(), "conductor", "workspaces");
}

function currentRepoSlug(): string {
  const r = runCommand("git", ["remote", "get-url", "origin"]);
  if (!r.ok) return "";
  // Extract "owner/repo" from URL like git@github.com:owner/repo.git
  const m = r.stdout.trim().match(/[:/]([^/]+\/[^/]+?)(?:\.git)?$/);
  return m ? m[1] : "";
}

function scanSiblings(root: string | null, claimed: ClaimedPR[], warnings: string[]): Sibling[] {
  if (!root || !existsSync(root)) return [];
  const mySlug = currentRepoSlug();
  if (!mySlug) {
    warnings.push("could not determine current repo slug; skipping sibling scan");
    return [];
  }
  const repoName = mySlug.split("/").pop() ?? "";
  // Conductor layout: <root>/<repo>/<workspace>/
  const repoDir = join(root, repoName);
  if (!existsSync(repoDir)) return [];
  const myAbsPath = resolve(process.cwd());
  const results: Sibling[] = [];
  for (const name of readdirSync(repoDir)) {
    const p = join(repoDir, name);
    if (resolve(p) === myAbsPath) continue;
    try {
      const s = statSync(p);
      if (!s.isDirectory()) continue;
    } catch {
      continue;
    }
    if (!existsSync(join(p, ".git")) && !existsSync(join(p, ".git/HEAD"))) continue;
    const versionFile = join(p, "VERSION");
    if (!existsSync(versionFile)) continue;
    let version: string;
    try {
      version = readFileSync(versionFile, "utf8").trim();
      if (!parseVersion(version)) continue;
    } catch {
      continue;
    }
    const branchR = runCommand("git", ["-C", p, "rev-parse", "--abbrev-ref", "HEAD"]);
    if (!branchR.ok) continue;
    const branch = branchR.stdout.trim();
    const commitTsR = runCommand("git", ["-C", p, "log", "-1", "--format=%ct"]);
    const last_commit_ts = commitTsR.ok ? Number(commitTsR.stdout.trim()) : 0;
    const has_open_pr = claimed.some((c) => c.branch === branch);
    results.push({
      path: p,
      branch,
      version,
      last_commit_ts,
      has_open_pr,
      is_active: false,
    });
  }
  return results;
}

function markActiveSiblings(siblings: Sibling[], baseVersion: Version): Sibling[] {
  const now = Math.floor(Date.now() / 1000);
  return siblings.map((s) => {
    const v = parseVersion(s.version);
    const isAhead = v ? cmpVersion(v, baseVersion) > 0 : false;
    const isFresh = s.last_commit_ts > 0 && now - s.last_commit_ts < ACTIVE_SIBLING_MAX_AGE_S;
    const is_active = isAhead && isFresh && !s.has_open_pr;
    return { ...s, is_active };
  });
}

function parseArgs(argv: string[]): { base: string; bump: Bump; current: string; workspaceRoot?: string; excludePR: number | null; help: boolean } {
  let base = "";
  let bump: Bump | "" = "";
  let current = "";
  let workspaceRoot: string | undefined;
  let excludePR: number | null = null;
  let help = false;
  for (let i = 0; i < argv.length; i++) {
    const a = argv[i];
    if (a === "--base") base = argv[++i] ?? "";
    else if (a === "--bump") bump = (argv[++i] ?? "") as Bump;
    else if (a === "--current-version") current = argv[++i] ?? "";
    else if (a === "--workspace-root") workspaceRoot = argv[++i];
    else if (a === "--exclude-pr") {
      const n = Number(argv[++i]);
      excludePR = Number.isFinite(n) && n > 0 ? n : null;
    }
    else if (a === "-h" || a === "--help") help = true;
  }
  if (help) return { base: "", bump: "micro", current: "", excludePR: null, help: true };
  if (!base) base = "main";
  if (!bump) {
    console.error("Error: --bump is required (major|minor|patch|micro)");
    process.exit(2);
  }
  if (!["major", "minor", "patch", "micro"].includes(bump)) {
    console.error(`Error: --bump must be major|minor|patch|micro (got ${bump})`);
    process.exit(2);
  }
  return { base, bump: bump as Bump, current, workspaceRoot, excludePR, help: false };
}

// Auto-detect: if --exclude-pr wasn't passed, check whether the current branch
// already has an open PR and exclude it by default. This prevents the self-
// reference bug where /ship's own PR inflates the queue on rerun.
function autoDetectExcludePR(): number | null {
  const r = runCommand("gh", ["pr", "view", "--json", "number", "-q", ".number"]);
  if (!r.ok) return null;
  const n = Number(r.stdout.trim());
  return Number.isFinite(n) && n > 0 ? n : null;
}

async function main() {
  const args = parseArgs(process.argv.slice(2));
  if (args.help) {
    console.log(
      "Usage: gstack-next-version --base <branch> --bump <level> --current-version <X.Y.Z.W> [--workspace-root <path|null>]",
    );
    process.exit(0);
  }
  const warnings: string[] = [];
  const host = detectHost();
  const baseVersion = args.current || readBaseVersion(args.base, warnings);
  const baseParsed = parseVersion(baseVersion);
  if (!baseParsed) {
    console.error(`Error: could not parse base version '${baseVersion}'`);
    process.exit(2);
  }

  const excludePR = args.excludePR ?? autoDetectExcludePR();
  if (excludePR !== null && args.excludePR === null) {
    warnings.push(`auto-excluded PR #${excludePR} (current branch's own PR)`);
  }

  let claimed: ClaimedPR[] = [];
  let offline = false;
  if (host === "github") {
    ({ claimed, offline } = await fetchGithubClaimed(args.base, excludePR, warnings));
  } else if (host === "gitlab") {
    ({ claimed, offline } = await fetchGitlabClaimed(args.base, excludePR, warnings));
  } else {
    warnings.push("host unknown; queue-awareness unavailable");
  }

  // Only count PRs that actually bumped VERSION past base as real "claims".
  // A PR whose VERSION equals base's VERSION hasn't claimed anything.
  const realClaims = claimed.filter((c) => {
    const v = parseVersion(c.version);
    return v !== null && cmpVersion(v, baseParsed) > 0;
  });
  const claimedVersions = realClaims
    .map((c) => parseVersion(c.version))
    .filter((v): v is Version => v !== null);

  const { version: picked, reason } = pickNextSlot(baseParsed, claimedVersions, args.bump);

  const workspaceRoot = resolveWorkspaceRoot(args.workspaceRoot);
  const siblings = markActiveSiblings(scanSiblings(workspaceRoot, claimed, warnings), baseParsed);
  const activeSiblings = siblings.filter((s) => s.is_active);

  // If an active sibling outranks our pick, bump past it (same bump level).
  let finalVersion = picked;
  let finalReason = reason;
  const activeAhead = activeSiblings
    .map((s) => parseVersion(s.version))
    .filter((v): v is Version => v !== null)
    .filter((v) => cmpVersion(v, finalVersion) >= 0);
  if (activeAhead.length) {
    const highest = activeAhead.sort(cmpVersion)[activeAhead.length - 1];
    finalVersion = bumpVersion(highest, args.bump);
    finalReason = `bumped past active sibling ${fmtVersion(highest)}`;
  }

  const out: Output = {
    version: fmtVersion(finalVersion),
    current_version: args.current || baseVersion,
    base_version: baseVersion,
    bump: args.bump,
    host,
    offline,
    claimed: realClaims,
    siblings,
    active_siblings: activeSiblings,
    reason: finalReason,
    warnings,
  };
  process.stdout.write(JSON.stringify(out, null, 2) + "\n");
}

// Pure-function exports for testing
export { parseVersion, fmtVersion, bumpVersion, cmpVersion, pickNextSlot, markActiveSiblings };

// Only run main() when invoked as a script, not when imported by tests.
if (import.meta.main) {
  main().catch((e) => {
    console.error("Unexpected error:", e?.stack ?? e);
    process.exit(3);
  });
}
