#!/usr/bin/env bun
// gstack-version-bump — deterministic version-state classifier + writer for /ship.
//
// Extracted from ship Step 12 prose (v2 plan T9, hybrid CLI extraction). The
// idempotency classification and the dual-write to VERSION + package.json are
// pure deterministic logic; running them as tested code removes the single
// worst /ship footgun — re-bumping an already-shipped branch — from prose the
// agent could skip or misread when the step lives in a lazy-loaded section.
//
// What STAYS agent judgment (NOT here): the bump-LEVEL decision (micro/patch vs
// minor/major, which may AskUserQuestion on feature signals) and the queue
// collision prompt. The slot pick itself is bin/gstack-next-version. This CLI
// only answers "what state am I in?" and "write this exact version".
//
// Subcommands:
//   classify --base <branch> [--version-path <p>]
//       Compares VERSION vs origin/<base>:VERSION vs package.json.version.
//       Emits JSON: { state, baseVersion, currentVersion, pkgVersion, pkgExists }
//       state ∈ FRESH | ALREADY_BUMPED | DRIFT_STALE_PKG | DRIFT_UNEXPECTED
//       Exit 0 on a decidable state (incl. DRIFT_UNEXPECTED — it's a real state
//       the caller must handle), exit 2 on bad args / unresolvable base.
//
//   write --version <X.Y.Z.W> [--version-path <p>]
//       Validates the 4-digit pattern, writes VERSION + package.json.version.
//       Use for the FRESH bump (or an approved queue rebump). Exit 3 on a
//       half-write (VERSION written, package.json failed) so the caller knows
//       drift exists; the next classify() will report DRIFT_STALE_PKG.
//
//   repair [--version-path <p>]
//       DRIFT_STALE_PKG path: sync package.json.version to the current VERSION
//       file. No bump. Validates the VERSION pattern first.
//
// Contract: classify NEVER writes. write/repair mutate VERSION + package.json
// only. No git mutation, no network. Mirrors gstack-next-version's reader/writer
// split so /ship composes them.

import { existsSync, readFileSync, writeFileSync } from "node:fs";
import { execFileSync } from "node:child_process";
import { join } from "node:path";

const VERSION_RE = /^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$/;
const DEFAULT = "0.0.0.0";

type State = "FRESH" | "ALREADY_BUMPED" | "DRIFT_STALE_PKG" | "DRIFT_UNEXPECTED";

function fail(msg: string, code = 2): never {
  process.stderr.write(`gstack-version-bump: ${msg}\n`);
  process.exit(code);
}

function argVal(args: string[], flag: string): string | undefined {
  const i = args.indexOf(flag);
  return i >= 0 && i + 1 < args.length ? args[i + 1] : undefined;
}

/** Resolve the VERSION file path: --version-path, else .gstack/version-path, else "VERSION". */
function resolveVersionPath(cwd: string, explicit?: string): string {
  if (explicit) return join(cwd, explicit);
  const pin = join(cwd, ".gstack", "version-path");
  if (existsSync(pin)) {
    const p = readFileSync(pin, "utf-8").trim();
    if (p) return join(cwd, p);
  }
  return join(cwd, "VERSION");
}

function readVersionFile(p: string): string {
  try {
    const v = readFileSync(p, "utf-8").replace(/[\r\n\s]/g, "");
    return v || DEFAULT;
  } catch {
    return DEFAULT;
  }
}

/** package.json version + existence, parsed without spawning node. */
function readPkgVersion(cwd: string): { exists: boolean; version: string } {
  const pkgPath = join(cwd, "package.json");
  if (!existsSync(pkgPath)) return { exists: false, version: "" };
  let raw: string;
  try {
    raw = readFileSync(pkgPath, "utf-8");
  } catch {
    return { exists: true, version: "" };
  }
  let parsed: unknown;
  try {
    parsed = JSON.parse(raw);
  } catch {
    fail("package.json is not valid JSON. Fix the file before re-running /ship.", 2);
  }
  const version = (parsed as { version?: unknown })?.version;
  return { exists: true, version: typeof version === "string" ? version : "" };
}

function writePkgVersion(cwd: string, version: string): void {
  const pkgPath = join(cwd, "package.json");
  const raw = readFileSync(pkgPath, "utf-8");
  const parsed = JSON.parse(raw) as Record<string, unknown>;
  parsed.version = version;
  writeFileSync(pkgPath, JSON.stringify(parsed, null, 2) + "\n");
}

function baseVersion(cwd: string, base: string, versionRel: string): string {
  // Verify the base ref resolves, mirroring the Step 12 guard.
  try {
    execFileSync("git", ["rev-parse", "--verify", `origin/${base}`], { cwd, stdio: "ignore" });
  } catch {
    fail(`Unable to resolve origin/${base}. Run 'git fetch origin' or verify the base branch exists.`, 2);
  }
  try {
    const out = execFileSync("git", ["show", `origin/${base}:${versionRel}`], { cwd }).toString();
    const v = out.replace(/[\r\n\s]/g, "");
    return v || DEFAULT;
  } catch {
    // VERSION absent on base (new repo / new file) → treat as 0.0.0.0.
    return DEFAULT;
  }
}

function classifyState(current: string, base: string, pkgExists: boolean, pkgVersion: string): State {
  if (current === base) {
    // VERSION unchanged vs base. A diverging package.json means someone hand-edited
    // package.json bypassing /ship — unsafe to guess which is authoritative.
    if (pkgExists && pkgVersion && pkgVersion !== current) return "DRIFT_UNEXPECTED";
    return "FRESH";
  }
  // VERSION already moved past base.
  if (pkgExists && pkgVersion && pkgVersion !== current) return "DRIFT_STALE_PKG";
  return "ALREADY_BUMPED";
}

function cmdClassify(args: string[], cwd: string): void {
  const base = argVal(args, "--base");
  if (!base) fail("classify requires --base <branch>", 2);
  const versionPath = resolveVersionPath(cwd, argVal(args, "--version-path"));
  const versionRel = argVal(args, "--version-path") ?? "VERSION";
  const current = readVersionFile(versionPath);
  const baseV = baseVersion(cwd, base!, versionRel);
  const pkg = readPkgVersion(cwd);
  const state = classifyState(current, baseV, pkg.exists, pkg.version);
  process.stdout.write(
    JSON.stringify({
      state,
      baseVersion: baseV,
      currentVersion: current,
      pkgVersion: pkg.version || null,
      pkgExists: pkg.exists,
    }) + "\n",
  );
  // DRIFT_UNEXPECTED is a real, decidable state — the caller stops on it, but the
  // classification itself succeeded, so exit 0. (Bad args / unresolvable base are
  // the only exit-2 cases.)
}

function cmdWrite(args: string[], cwd: string): void {
  const version = argVal(args, "--version");
  if (!version) fail("write requires --version <X.Y.Z.W>", 2);
  if (!VERSION_RE.test(version!)) {
    fail(`NEW_VERSION (${version}) does not match MAJOR.MINOR.PATCH.MICRO. Aborting.`, 2);
  }
  const versionPath = resolveVersionPath(cwd, argVal(args, "--version-path"));
  writeFileSync(versionPath, version + "\n");
  if (existsSync(join(cwd, "package.json"))) {
    try {
      writePkgVersion(cwd, version!);
    } catch {
      fail(
        "failed to update package.json. VERSION was written but package.json is now stale. " +
          "Re-run — classify will report DRIFT_STALE_PKG and repair will sync it.",
        3,
      );
    }
  }
  process.stdout.write(JSON.stringify({ wrote: version, packageJson: existsSync(join(cwd, "package.json")) }) + "\n");
}

function cmdRepair(args: string[], cwd: string): void {
  const versionPath = resolveVersionPath(cwd, argVal(args, "--version-path"));
  const current = readVersionFile(versionPath);
  if (!VERSION_RE.test(current)) {
    fail(
      `VERSION file contents (${current}) do not match MAJOR.MINOR.PATCH.MICRO. ` +
        "Refusing to propagate invalid semver into package.json. Fix VERSION, then re-run /ship.",
      2,
    );
  }
  if (!existsSync(join(cwd, "package.json"))) {
    fail("repair: no package.json to sync.", 2);
  }
  try {
    writePkgVersion(cwd, current);
  } catch {
    fail("drift repair failed — could not update package.json.", 3);
  }
  process.stdout.write(JSON.stringify({ repaired: current }) + "\n");
}

// Exported for unit tests (pure logic, no I/O).
export { classifyState, VERSION_RE, type State };

if (import.meta.main) {
  const [sub, ...rest] = process.argv.slice(2);
  const cwd = process.cwd();
  switch (sub) {
    case "classify": cmdClassify(rest, cwd); break;
    case "write": cmdWrite(rest, cwd); break;
    case "repair": cmdRepair(rest, cwd); break;
    default:
      fail("usage: gstack-version-bump <classify|write|repair> [flags]", 2);
  }
}