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

const fs = require('node:fs');
const path = require('node:path');
const { execFileSync } = require('node:child_process');

const SHA_REGEX = /^[0-9a-fA-F]{40}$/;
const ZERO_SHA_REGEX = /^0{40}$/;

function normalizePath(filePath) {
  if (typeof filePath !== 'string') return '';
  return filePath.replace(/\\/g, '/').replace(/^\.\//, '').trim();
}

function isValidSha(sha) {
  if (typeof sha !== 'string') return false;
  return SHA_REGEX.test(sha.trim());
}

function isZeroSha(sha) {
  if (typeof sha !== 'string') return false;
  return ZERO_SHA_REGEX.test(sha.trim());
}

function isAppPath(filePath) {
  const p = normalizePath(filePath);
  if (!p) return false;
  return (
    p.startsWith('lib/') ||
    p.startsWith('test/') ||
    p.startsWith('integration_test/') ||
    p.startsWith('android/') ||
    p.startsWith('assets/') ||
    p === 'pubspec.yaml' ||
    p === 'pubspec.lock' ||
    p === 'analysis_options.yaml' ||
    p === 'build.yaml'
  );
}

function isNativeBuildPath(filePath) {
  const p = normalizePath(filePath);
  if (!p) return false;
  // Native build requires: Android code, CI-critical files, or build config.
  // Only CI files that affect build behavior trigger release builds; doc/comment changes do not.
  return (
    p.startsWith('android/') ||
    p === '.github/workflows/android-build.yml' ||
    p.startsWith('.github/scripts/') ||
    p === 'pubspec.yaml' ||
    p === 'pubspec.lock' ||
    p === 'analysis_options.yaml' ||
    p === 'build.yaml'
  );
}

function isCiPath(filePath) {
  const p = normalizePath(filePath);
  if (!p) return false;
  return (
    p === '.github/workflows/android-build.yml' ||
    p.startsWith('.github/scripts/')
  );
}

function classifyFiles(fileList) {
  if (!Array.isArray(fileList)) {
    return {
      android_changed: false,
      app_changed: false,
      native_build_changed: false,
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  const appFiles = [];
  const ciFiles = [];
  const unrelatedFiles = [];
  const nativeBuildFiles = [];

  for (const rawFile of fileList) {
    const file = normalizePath(rawFile);
    if (!file) continue;

    if (isAppPath(file)) {
      appFiles.push(file);
    } else if (isCiPath(file)) {
      ciFiles.push(file);
    } else {
      unrelatedFiles.push(file);
    }

    // Track files that trigger native builds (Android code, CI, config)
    if (isNativeBuildPath(file)) {
      nativeBuildFiles.push(file);
    }
  }

  const app_changed = appFiles.length > 0;
  const android_changed = appFiles.length > 0 || ciFiles.length > 0;
  const native_build_changed = nativeBuildFiles.length > 0;

  return {
    android_changed,
    app_changed,
    native_build_changed,
    appFiles,
    ciFiles,
    unrelatedFiles
  };
}

function getChangedFiles(baseSha, headSha, repoDir = process.cwd()) {
  if (!isValidSha(baseSha) || !isValidSha(headSha)) {
    throw new Error(`Invalid git SHA: base=${baseSha}, head=${headSha}`);
  }

  // Attempt 3-dot diff (merge-base between base and head)
  try {
    const stdout = execFileSync('git', ['diff', '--name-only', `${baseSha}...${headSha}`], {
      cwd: repoDir,
      encoding: 'utf8',
      stdio: ['ignore', 'pipe', 'pipe']
    });
    return stdout.split(/\r?\n/).map(s => s.trim()).filter(Boolean);
  } catch (threeDotError) {
    // Fall back to direct 2-commit diff
    try {
      const stdout = execFileSync('git', ['diff', '--name-only', baseSha, headSha], {
        cwd: repoDir,
        encoding: 'utf8',
        stdio: ['ignore', 'pipe', 'pipe']
      });
      return stdout.split(/\r?\n/).map(s => s.trim()).filter(Boolean);
    } catch (fallbackError) {
      throw new Error(`git diff failed: ${threeDotError.message}; fallback failed: ${fallbackError.message}`);
    }
  }
}

function detectAndroidChanges({ eventName, baseSha, headSha, repoDir }, deps = {}) {
  const getFiles = deps.getChangedFilesFn || getChangedFiles;

  // Manual dispatch: always run full job
  if (eventName === 'workflow_dispatch') {
    return {
      android_changed: true,
      app_changed: true,
      native_build_changed: true,
      reason: 'Manual workflow_dispatch; full pipeline authorized',
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  // Push with zero or missing base SHA (e.g. new branch or missing before SHA): fail safe
  if (!baseSha || isZeroSha(baseSha) || !isValidSha(baseSha)) {
    return {
      android_changed: true,
      native_build_changed: true,
      app_changed: true,
      reason: `Zero, missing, or invalid base SHA (${baseSha}); failing safe to full build`,
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  // Missing or invalid head SHA: fail safe
  if (!headSha || isZeroSha(headSha) || !isValidSha(headSha)) {
    return {
      android_changed: true,
      native_build_changed: true,
      app_changed: true,
      reason: `Zero, missing, or invalid head SHA (${headSha}); failing safe to full build`,
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  // Identical base and head: no changes
  if (baseSha.trim() === headSha.trim()) {
    return {
      android_changed: false,
      native_build_changed: false,
      app_changed: false,
      reason: 'Base SHA and Head SHA are identical; no changes detected',
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  // Compare diff
  let files;
  try {
    files = getFiles(baseSha.trim(), headSha.trim(), repoDir);
  } catch (err) {
    return {
      android_changed: true,
      native_build_changed: true,
      app_changed: true,
      reason: `Failed to retrieve git diff: ${err.message}; failing safe to full build`,
      appFiles: [],
      ciFiles: [],
      unrelatedFiles: []
    };
  }

  const classification = classifyFiles(files);
  return {
    ...classification,
    totalFiles: files.length,
    reason: `Analyzed ${files.length} changed file(s): ` +
      `${classification.appFiles.length} app, ` +
      `${classification.ciFiles.length} CI, ` +
      `${classification.unrelatedFiles.length} unrelated`
  };
}

function runCli() {
  const eventName = process.argv[2] || process.env.GITHUB_EVENT_NAME || 'pull_request';
  const baseSha = process.argv[3] || process.env.BASE_SHA || '';
  const headSha = process.argv[4] || process.env.HEAD_SHA || '';

  console.log(`[detect-android-changes] Starting detection...`);
  console.log(`[detect-android-changes] Event: ${eventName}`);
  console.log(`[detect-android-changes] Base SHA: ${baseSha}`);
  console.log(`[detect-android-changes] Head SHA: ${headSha}`);

  const result = detectAndroidChanges({
    eventName,
    baseSha,
    headSha
  });

  console.log(`[detect-android-changes] android_changed=${result.android_changed}`);
  console.log(`[detect-android-changes] app_changed=${result.app_changed}`);
  console.log(`[detect-android-changes] native_build_changed=${result.native_build_changed}`);
  console.log(`[detect-android-changes] Reason: ${result.reason}`);

  if (result.appFiles && result.appFiles.length > 0) {
    console.log(`[detect-android-changes] App files (${result.appFiles.length}):`);
    for (const f of result.appFiles) {
      console.log(`  + ${f}`);
    }
  }

  if (result.ciFiles && result.ciFiles.length > 0) {
    console.log(`[detect-android-changes] CI files (${result.ciFiles.length}):`);
    for (const f of result.ciFiles) {
      console.log(`  * ${f}`);
    }
  }

  if (result.unrelatedFiles && result.unrelatedFiles.length > 0) {
    console.log(`[detect-android-changes] Unrelated files (${result.unrelatedFiles.length}):`);
    for (const f of result.unrelatedFiles) {
      console.log(`  - ${f}`);
    }
  }

  const githubOutput = process.env.GITHUB_OUTPUT;
  if (githubOutput) {
    fs.appendFileSync(
      githubOutput,
      `android_changed=${result.android_changed}\napp_changed=${result.app_changed}\nnative_build_changed=${result.native_build_changed}\n`
    );
    console.log(`[detect-android-changes] Wrote outputs to GITHUB_OUTPUT.`);
  }

  process.exit(0);
}

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

module.exports = {
  normalizePath,
  isValidSha,
  isZeroSha,
  isAppPath,
  isCiPath,
  classifyFiles,
  getChangedFiles,
  detectAndroidChanges
};