#!/usr/bin/env node
'use strict';

/**
 * Deterministic verifier for the /gsd-reapply-patches Step 5 "Hunk Verification
 * Gate". For each backed-up patch file, asserts that the user's added lines
 * (computed from a real diff against the pristine baseline, not from the
 * LLM's prose summary) survive into the merged output.
 *
 * Usage:
 *   node scripts/verify-reapply-patches.cjs \
 *     --patches-dir <path>        \  # gsd-local-patches/
 *     --config-dir <path>         \  # ~/.claude (or runtime equivalent)
 *     [--pristine-dir <path>]        # gsd-pristine/; if absent, falls back to
 *                                    # treating every significant backup line as
 *                                    # required (over-broad but safe for #2969:
 *                                    # false-positive halts beat silent successes
 *                                    # on lost content)
 *     [--json]                       # emit JSON report instead of human text
 *
 * Exit codes:
 *   0 — every user-added line is present in the merged file (gate passes)
 *   1 — at least one missing line in at least one file (gate fails)
 *   2 — usage / structural error (e.g. patches dir missing)
 *
 * Bug #2969: the Step 5 gate previously trusted Claude's free-text "verified:
 * yes/no" reporting per hunk. The LLM was filling in `yes` even when content
 * had been silently dropped. Moving the check to a deterministic script is the
 * durability fix.
 */

const fs = require('node:fs');
const path = require('node:path');
const crypto = require('node:crypto');
const { ExitError, runMain } = require('./lib/cli-exit.cjs');

const SIGNIFICANT_MIN_CHARS = 12;
const GSD_HOOK_VERSION_LINE_RE = /^(?:\/\/|#)\s*gsd-hook-version:\s*\S+\s*$/i;

function parseArgs(argv) {
  const opts = { patchesDir: null, configDir: null, pristineDir: null, json: false };
  for (let i = 0; i < argv.length; i++) {
    const arg = argv[i];
    if (arg === '--patches-dir') opts.patchesDir = argv[++i];
    else if (arg === '--config-dir') opts.configDir = argv[++i];
    else if (arg === '--pristine-dir') opts.pristineDir = argv[++i];
    else if (arg === '--json') opts.json = true;
    else if (arg === '--help' || arg === '-h') {
      process.stdout.write(
        'usage: verify-reapply-patches.cjs --patches-dir <path> --config-dir <path> [--pristine-dir <path>] [--json]\n',
      );
      throw new ExitError(0);
    } else {
      throw new ExitError(2, `unknown argument: ${arg}`);
    }
  }
  return opts;
}

function isSignificantLine(line) {
  const trimmed = line.trim();
  if (trimmed.length < SIGNIFICANT_MIN_CHARS) return false;
  // Pure punctuation / closing brackets carry too little structural info to
  // reliably distinguish a survived hunk from incidental similarity.
  if (/^[\s})\];,]+$/.test(trimmed)) return false;
  // Generic decorative comments like `// ----` similarly fail the test.
  if (/^[\s\-=#*/]+$/.test(trimmed)) return false;
  return true;
}

function normalizeUpstreamOwnedLine(line) {
  const trimmed = line.trim();
  if (!trimmed) return line;
  if (GSD_HOOK_VERSION_LINE_RE.test(trimmed)) {
    const prefix = trimmed.startsWith('#') ? '#' : '//';
    return `${prefix} gsd-hook-version: __GSD_VERSION_TOKEN__`;
  }
  return line;
}

/**
 * Compute the SHA-256 hex digest of a string (UTF-8 encoded).
 */
function sha256(content) {
  return crypto.createHash('sha256').update(content, 'utf8').digest('hex');
}

/**
 * Read the `pristine_hashes` map from backup-meta.json in the patches dir.
 * Returns an empty object if backup-meta.json is absent, unreadable, or has no
 * `pristine_hashes` field — callers must treat an empty map as "no recorded
 * hash for any file" (no hash-validation possible, not an error).
 */
function readPristineHashes(patchesDir) {
  const metaPath = path.join(patchesDir, 'backup-meta.json');
  try {
    const raw = fs.readFileSync(metaPath, 'utf8');
    const parsed = JSON.parse(raw);
    if (parsed && typeof parsed.pristine_hashes === 'object' && parsed.pristine_hashes !== null) {
      return parsed.pristine_hashes;
    }
  } catch {
    // absent or unreadable — not an error, just no recorded hashes
  }
  return {};
}

/**
 * Walk a directory, returning every file's path relative to the root.
 */
function walk(rootDir, relPrefix = '') {
  const out = [];
  if (!fs.existsSync(rootDir)) return out;
  for (const entry of fs.readdirSync(rootDir, { withFileTypes: true })) {
    const rel = relPrefix ? path.join(relPrefix, entry.name) : entry.name;
    const abs = path.join(rootDir, entry.name);
    if (entry.isDirectory()) {
      out.push(...walk(abs, rel));
    } else if (entry.isFile()) {
      out.push(rel);
    }
  }
  return out;
}

/**
 * Compute the set of "user-added" lines: lines present in the backup but
 * absent from the pristine baseline. If no pristine is provided, falls back
 * to using every significant line in the backup (over-broad but safe — favours
 * false-positive failures over silent successes, which is the right side to
 * err on for #2969).
 */
function computeUserAddedLines(backupContent, pristineContent) {
  const backupLines = backupContent.split(/\r?\n/);
  if (!pristineContent) {
    return backupLines.filter(isSignificantLine);
  }
  const pristineSet = new Set(
    pristineContent.split(/\r?\n/).map(normalizeUpstreamOwnedLine),
  );
  return backupLines.filter((line) => {
    if (!isSignificantLine(line)) return false;
    return !pristineSet.has(normalizeUpstreamOwnedLine(line));
  });
}

/**
 * Stable reason codes for the per-file result. Tests assert via
 * `assert.equal(result.reason, REASON.X)` rather than regex-matching prose,
 * so the diagnostic surface is a typed enum, not free text.
 *
 * Adding a new reason requires updating the REASON map AND the tests'
 * shape assertion that locks the documented set of codes.
 */
const REASON = Object.freeze({
  OK_NO_USER_LINES_VS_PRISTINE: 'ok_no_user_lines_vs_pristine',
  OK_NO_SIGNIFICANT_BACKUP_LINES: 'ok_no_significant_backup_lines',
  // Bug #3657: the on-disk gsd-pristine/ file's SHA-256 does not match the
  // hash recorded in backup-meta.json.pristine_hashes.  This means the
  // pristine snapshot was refreshed to a newer GSD version after the backup
  // was captured.  Using the wrong-version pristine as the diff baseline would
  // invert the delta (upstream removals appear as "missing user lines").
  // The verifier skips this file rather than false-failing it.  A separate
  // re-anchor step (or the git-aware fallback in the workflow) is needed to
  // resolve this file; the guard here ensures the gate does not report spurious
  // failures in the meantime.
  OK_PRISTINE_DRIFT_DETECTED: 'ok_pristine_drift_detected',
  // Bug #934: backup-meta.json records a pristine_hash for this file but the
  // gsd-pristine/ file is absent from disk.  This happens on post-#604-rename
  // installs where saveLocalPatches discarded the only pristine candidate
  // because its hash did not match the old-release hash (the file changed
  // upstream between releases).  Without a baseline the verifier cannot
  // distinguish user-added lines from upstream-changed lines, so falling to
  // over-broad mode would produce FAIL_USER_LINES_MISSING false positives for
  // every upstream-removed line.  The correct posture is advisory/non-blocking:
  // report OK_NO_BASELINE so the caller can log a warning without halting the
  // gate on a spurious failure.  This is a bounded "cannot reason → do not
  // block" rather than "ignore everything" — it only applies when the hash was
  // recorded (modern installer) but the file is absent (specific gap).
  OK_NO_BASELINE: 'ok_no_baseline',
  FAIL_INSTALLED_MISSING: 'fail_installed_missing',
  FAIL_INSTALLED_NOT_REGULAR_FILE: 'fail_installed_not_regular_file',
  FAIL_READ_ERROR: 'fail_read_error',
  FAIL_USER_LINES_MISSING: 'fail_user_lines_missing',
});

function verifyFile({ relPath, patchesDir, configDir, pristineDir, pristineHashes }) {
  const backupPath = path.join(patchesDir, relPath);
  const installedPath = path.join(configDir, relPath);
  const result = { file: relPath, status: 'ok', missing: [], reason: null };

  if (!fs.existsSync(backupPath) || !fs.statSync(backupPath).isFile()) {
    return result; // walked entry no longer exists — non-fatal
  }

  // Installed path checks: must exist, must be a regular file, must be
  // readable. Anything else is a fail-with-diagnostic, not a crash that
  // aborts the whole gate run and drops structured output.
  let installedStat;
  try {
    installedStat = fs.statSync(installedPath);
  } catch {
    result.status = 'fail';
    result.reason = REASON.FAIL_INSTALLED_MISSING;
    return result;
  }
  if (!installedStat.isFile()) {
    result.status = 'fail';
    result.reason = REASON.FAIL_INSTALLED_NOT_REGULAR_FILE;
    return result;
  }

  let backupContent;
  let installedContent;
  try {
    backupContent = fs.readFileSync(backupPath, 'utf8');
    installedContent = fs.readFileSync(installedPath, 'utf8');
  } catch {
    result.status = 'fail';
    result.reason = REASON.FAIL_READ_ERROR;
    return result;
  }

  // Normalize to forward slashes so the key lookup matches on Windows
  // where path.join produces backslash-separated relPath values but
  // backup-meta.json stores keys written with forward slashes.
  const hashKey = relPath.replace(/\\/g, '/');
  const recordedHash = pristineHashes && pristineHashes[hashKey];

  let pristineContent = null;
  if (pristineDir) {
    const pristinePath = path.join(pristineDir, relPath);
    // Bug #934: track whether the pristine path EXISTS on disk (stat did not
    // throw ENOENT).  A regular file that fails to read, or a non-file path
    // (e.g. a directory accidentally placed at the pristine path), is treated
    // as "present but unusable" — we fall to over-broad mode (safe side).
    // OK_NO_BASELINE is reserved for the strictly absent case: stat throws,
    // meaning the file was never written (the gap the bug describes).
    let pristinePathExists = false;
    try {
      const stat = fs.statSync(pristinePath);
      pristinePathExists = true; // path exists (any type)
      if (stat.isFile()) {
        const candidate = fs.readFileSync(pristinePath, 'utf8');
        // Bug #3657: if backup-meta.json recorded a pristine_hash for this
        // file, validate that the on-disk pristine matches it.  A mismatch
        // means the installer refreshed gsd-pristine/ to a newer GSD version
        // after the backup was captured.  Using the wrong-version pristine as
        // the diff baseline inverts the delta: upstream removals appear as
        // "user-added lines that must survive", causing FAIL_USER_LINES_MISSING
        // false positives.  When the hash is stale, skip the pristine and fall
        // through to over-broad mode (every significant backup line is checked).
        // Over-broad mode never false-fails for a different reason because all
        // backup lines that are genuinely user-added will still be present in a
        // correctly merged install.
        if (recordedHash) {
          if (sha256(candidate) === recordedHash) {
            // Hash matches: the on-disk pristine is the correct baseline.
            pristineContent = candidate;
          } else {
            // Hash mismatch: the on-disk gsd-pristine/ was refreshed to a newer
            // GSD version after the backup was captured.  Using it as the diff
            // baseline would invert the delta and produce false FAIL_USER_LINES_MISSING
            // reports (Bug #3657).  Report the file as ok with a diagnostic code
            // so the gate does not false-fail; a re-anchor or git-aware baseline
            // step is required to verify this file correctly.
            result.reason = REASON.OK_PRISTINE_DRIFT_DETECTED;
            return result;
          }
        } else {
          // No recorded hash for this file (older installer or absent
          // backup-meta) — use the on-disk pristine as-is (pre-fix behaviour).
          pristineContent = candidate;
        }
      }
      // Non-file at pristinePath (e.g. a directory): stat succeeded so
      // pristinePathExists is true; we fall through to over-broad mode below,
      // which is safe and conservative.
    } catch {
      // Pristine stat threw — path is absent (ENOENT) or inaccessible.
      // pristinePathExists stays false.
    }

    // Bug #934: recordedHash is present (modern installer) but the pristine
    // path does not exist on disk at all (stat threw above).  This means
    // saveLocalPatches recorded a hash but could not write the corresponding
    // gsd-pristine/ file (the only candidate was discarded because it was from
    // a newer release).  Falling to over-broad mode here would treat every
    // upstream-changed line as a "user-added line that must survive", producing
    // false FAIL_USER_LINES_MISSING for each upstream removal.  Since we
    // cannot reason correctly without a baseline, the safe answer is advisory/
    // non-blocking: return OK_NO_BASELINE and let the caller decide.
    // NOTE: this guard fires ONLY when stat threw (path absent), not when the
    // path is present but non-file — in that case over-broad mode is safer.
    if (!pristinePathExists && recordedHash) {
      result.reason = REASON.OK_NO_BASELINE;
      return result;
    }
  }

  const userAdded = computeUserAddedLines(backupContent, pristineContent);
  if (userAdded.length === 0) {
    // Backup and pristine match exactly (or no significant content) — nothing
    // to verify but also nothing to lose. Report as ok with diagnostic code.
    result.reason = pristineContent
      ? REASON.OK_NO_USER_LINES_VS_PRISTINE
      : REASON.OK_NO_SIGNIFICANT_BACKUP_LINES;
    return result;
  }

  for (const line of userAdded) {
    if (!installedContent.includes(line)) {
      result.missing.push(line.trim());
    }
  }
  if (result.missing.length > 0) {
    result.status = 'fail';
    result.reason = REASON.FAIL_USER_LINES_MISSING;
  }
  return result;
}

function main() {
  const opts = parseArgs(process.argv.slice(2));
  if (!opts.patchesDir || !opts.configDir) {
    throw new ExitError(2, '--patches-dir and --config-dir are required');
  }
  if (!fs.existsSync(opts.patchesDir)) {
    throw new ExitError(2, `patches dir not found: ${opts.patchesDir}`);
  }
  if (!fs.existsSync(opts.configDir)) {
    throw new ExitError(2, `config dir not found: ${opts.configDir}`);
  }

  const files = walk(opts.patchesDir).filter((f) => !f.endsWith('backup-meta.json'));
  // Bug #3657: read pristine_hashes from backup-meta.json once and share
  // across all per-file verifications so each can detect drift independently.
  const pristineHashes = readPristineHashes(opts.patchesDir);
  const results = files.map((relPath) =>
    verifyFile({
      relPath,
      patchesDir: opts.patchesDir,
      configDir: opts.configDir,
      pristineDir: opts.pristineDir,
      pristineHashes,
    }),
  );

  const failures = results.filter((r) => r.status === 'fail');

  // Bug #3657 (Finding 1): aggregate drifted files into top-level report fields
  // so workflow Step 5a can gate on drift distinctly from failures.  Drift is
  // NOT a failure (exit code stays 0) but the workflow now has structured data
  // to decide whether to proceed.  Per-file shape is unchanged: each drifted
  // result still has status:'ok' + reason:OK_PRISTINE_DRIFT_DETECTED for
  // backward compat.  The new top-level fields are purely additive.
  const driftedResults = results.filter((r) => r.reason === REASON.OK_PRISTINE_DRIFT_DETECTED);
  const drifted = driftedResults.length;
  const drifted_files = driftedResults.map((r) => r.file);

  // Bug #934: aggregate no-baseline files into top-level report fields so the
  // workflow can log a warning about files that could not be verified.  Like
  // drift, this is NOT a failure (exit code stays 0) but gives the caller
  // structured data to surface the advisory condition.
  const noBaselineResults = results.filter((r) => r.reason === REASON.OK_NO_BASELINE);
  const no_baseline = noBaselineResults.length;
  const no_baseline_files = noBaselineResults.map((r) => r.file);

  if (opts.json) {
    process.stdout.write(
      JSON.stringify({ checked: results.length, failures: failures.length, drifted, drifted_files, no_baseline, no_baseline_files, results }, null, 2) + '\n',
    );
  } else {
    process.stdout.write(`# Hunk Verification Gate (#2969)\n\n`);
    process.stdout.write(`Checked: ${results.length} file(s)\n`);
    process.stdout.write(`Failures: ${failures.length}\n\n`);
    if (failures.length > 0) {
      process.stdout.write(`## Files with missing user-added content\n\n`);
      for (const r of failures) {
        process.stdout.write(`- ${r.file}\n`);
        if (r.reason) process.stdout.write(`  reason: ${r.reason}\n`);
        for (const line of r.missing.slice(0, 5)) {
          process.stdout.write(`  missing: ${line}\n`);
        }
        if (r.missing.length > 5) {
          process.stdout.write(`  …and ${r.missing.length - 5} more line(s)\n`);
        }
      }
    }
  }

  return failures.length > 0 ? 1 : 0;
}

if (require.main === module) {
  runMain(main);
}

module.exports = { computeUserAddedLines, isSignificantLine, verifyFile, walk, REASON, readPristineHashes, sha256 };