import { spawnSync } from 'child_process';
import fs from 'fs';
import path from 'path';
import { fileURLToPath } from 'url';
import { GITEA_SERVER_URL, GITEA_REPOSITORY, GITEA_TOKEN, PR_HEAD_BRANCH, FINDINGS_PATH, getLLMConfig } from './config.js';
import { line, ok, warn, error } from './log.js';

const ACTION_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
const GENERATED_SYNC_PATHS = [FINDINGS_PATH, '.gitea/ai-review/exclusions.json'];
const remoteUrl = `${GITEA_SERVER_URL.replace(/\/$/, '')}/${GITEA_REPOSITORY}.git`;
export const BOT_COMMIT_MARKER = '[ai-review-bot]';
export const SYNC_PATHS = [
  '.amazonq/rules/triage-findings.md',
  '.agents/skills/triage-findings/SKILL.md',
  '.antigravity/skills/triage-findings/SKILL.md',
  '.codex/skills/triage-findings/SKILL.md',
  '.codex/skills/triage-findings/agents/openai.yaml',
  '.claude/skills/triage-findings/SKILL.md',
  '.gemini/skills/triage-findings/SKILL.md',
  '.github/copilot-instructions.md',
  '.github/skills/triage-findings/SKILL.md',
  'AGENTS.md',
  'ANTIGRAVITY.md',
  'CLAUDE.md',
  'GEMINI.md',
];
const FORCE_SYNC_FILE_PATHS = [
  '.github/copilot-instructions.md',
  'AGENTS.md',
  'ANTIGRAVITY.md',
  'CLAUDE.md',
  'GEMINI.md',
];
const MERGE_SYNC_FILE_PATHS = new Set([
  'AGENTS.md',
  'ANTIGRAVITY.md',
  'CLAUDE.md',
  'GEMINI.md',
]);
let instructionMergeAssistantPromise = null;
const SYNC_TREE_PATHS = [
  '.agents/skills/triage-findings',
  '.antigravity/skills/triage-findings',
  '.codex/skills/triage-findings',
  '.claude/skills/triage-findings',
  '.gemini/skills/triage-findings',
  '.github/skills/triage-findings',
];

function makeRunner(spawn) {
  return function run(args, cwd, env) {
    const opts = { cwd, encoding: 'utf8' };
    if (env) opts.env = env;
    const result = spawn('git', args, opts);
    if (result.error) throw result.error;
    if (result.status !== 0) throw new Error((result.stderr || result.stdout || '').trim());
    return (result.stdout || '').trim();
  };
}

function withAskpass(workspace, fn) {
  const askpassScript = path.join(workspace, '.git-askpass.sh');
  fs.writeFileSync(askpassScript, '#!/bin/sh\necho "$GIT_TOKEN"\n', { mode: 0o700 });
  const credEnv = { ...process.env, GIT_ASKPASS: askpassScript, GIT_USERNAME: 'x-token', GIT_TOKEN: GITEA_TOKEN };
  try {
    return fn(credEnv);
  } finally {
    try { fs.unlinkSync(askpassScript); } catch {}
  }
}

function readGitOutput(run, args, cwd, env) {
  try {
    return run(args, cwd, env);
  } catch {
    return '';
  }
}

function normalizeText(text) {
  return text.replace(/\r\n/g, '\n');
}

function splitTextBlocks(text) {
  const normalized = normalizeText(text).replace(/\n+$/, '');
  if (!normalized) return [];
  return normalized.split(/\n{2,}/).map(block => block.trimEnd()).filter(Boolean);
}

function mergeText(existingText, sourceText) {
  const existing = normalizeText(existingText);
  const source = normalizeText(sourceText);
  if (existing === source) return existing;

  const mergedBlocks = splitTextBlocks(existing);
  const seenBlocks = new Set(mergedBlocks.map(block => block.trim()));
  let changed = false;

  for (const block of splitTextBlocks(source)) {
    const key = block.trim();
    if (seenBlocks.has(key)) continue;
    seenBlocks.add(key);
    mergedBlocks.push(block);
    changed = true;
  }

  if (!changed) return existing;
  return `${mergedBlocks.join('\n\n')}\n`;
}

function uniqueBlocksFromTexts(...texts) {
  const seen = new Set();
  const blocks = [];
  for (const text of texts) {
    for (const block of splitTextBlocks(text)) {
      const key = block.trim();
      if (!key || seen.has(key)) continue;
      seen.add(key);
      blocks.push(block);
    }
  }
  return blocks;
}

function validateMergedInstructionText(mergedText, requiredBlocks) {
  const candidate = normalizeText(mergedText);
  return requiredBlocks.every(block => candidate.includes(normalizeText(block).trim()));
}

class InstructionMergeError extends Error {
  constructor(message, options) {
    super(message, options);
    this.name = 'InstructionMergeError';
  }
}

function abortInstructionMerge(message) {
  error(message);
  process.exit(1);
  throw new InstructionMergeError(message);
}

function syncFileOverwrite(sourceRoot, repoDir, relPath) {
  const src = path.join(sourceRoot, relPath);
  if (!fs.existsSync(src)) return null;

  const dest = path.join(repoDir, relPath);
  fs.mkdirSync(path.dirname(dest), { recursive: true });
  fs.copyFileSync(src, dest);
  return relPath;
}

async function getInstructionMergeAssistant() {
  const { provider } = getLLMConfig();
  if (!provider) return null;
  if (instructionMergeAssistantPromise) return instructionMergeAssistantPromise;

  instructionMergeAssistantPromise = (async () => {
    try {
      const { chatJSON } = await import('./llm.js');
      return async ({ relPath, existingText, sourceText, deterministicText }) => {
        const systemPrompt = [
          'You merge repository instruction files without losing any skill, command, or rule.',
          'Never delete unique content from either input.',
          'You may only remove exact duplicates or improve ordering/formatting.',
          'Return JSON with a single field: merged_text.',
        ].join(' ');
        const userContent = JSON.stringify({
          path: relPath,
          existing_text: existingText,
          source_text: sourceText,
          deterministic_candidate: deterministicText,
        });
        const result = await chatJSON(systemPrompt, userContent);
        if (typeof result === 'string') return result;
        if (result && typeof result.merged_text === 'string') return result.merged_text;
        return null;
      };
    } catch (e) {
      warn(`[merge] AI instruction merge unavailable: ${e.message}`);
      return null;
    }
  })();

  return instructionMergeAssistantPromise;
}

export async function mergeInstructionText(existingText, sourceText, relPath, aiMergeAssistant = null) {
  const deterministic = mergeText(existingText, sourceText);
  const requiredBlocks = uniqueBlocksFromTexts(existingText, sourceText);
  if (!aiMergeAssistant || requiredBlocks.length === 0) return deterministic;

  try {
    const aiMerged = await aiMergeAssistant({ relPath, existingText, sourceText, deterministicText: deterministic, requiredBlocks });
    if (typeof aiMerged === 'string' && validateMergedInstructionText(aiMerged, requiredBlocks)) {
      return normalizeText(aiMerged) === normalizeText(existingText) ? existingText : aiMerged;
    }
    abortInstructionMerge(`[merge] ${relPath} AI result rejected; refusing fallback`);
  } catch (e) {
    if (e instanceof InstructionMergeError) throw e;
    abortInstructionMerge(`[merge] ${relPath} AI merge failed: ${e.message}`);
  }
}

async function syncInstructionFile(sourceRoot, repoDir, relPath, aiMergeAssistant = null) {
  const src = path.join(sourceRoot, relPath);
  if (!fs.existsSync(src)) return null;

  const dest = path.join(repoDir, relPath);
  fs.mkdirSync(path.dirname(dest), { recursive: true });

  if (!fs.existsSync(dest)) {
    fs.copyFileSync(src, dest);
    return relPath;
  }

  const existingText = fs.readFileSync(dest, 'utf8');
  const sourceText = fs.readFileSync(src, 'utf8');
  const merged = await mergeInstructionText(existingText, sourceText, relPath, aiMergeAssistant);
  if (merged !== existingText) {
    fs.writeFileSync(dest, merged, 'utf8');
  }
  return relPath;
}

function syncTree(sourceRoot, repoDir, relDir) {
  const srcDir = path.join(sourceRoot, relDir);
  if (!fs.existsSync(srcDir)) return [];

  const copied = [];
  for (const entry of fs.readdirSync(srcDir, { withFileTypes: true })) {
    const relPath = path.join(relDir, entry.name);
    if (entry.isDirectory()) {
      copied.push(...syncTree(sourceRoot, repoDir, relPath));
      continue;
    }
    const synced = syncFileOverwrite(sourceRoot, repoDir, relPath);
    if (synced) copied.push(synced);
  }
  return copied;
}

export function getRepoState(repoDir, _spawnSync = spawnSync) {
  const run = makeRunner(_spawnSync);
  const headSha = readGitOutput(run, ['rev-parse', 'HEAD'], repoDir);
  const shortSha = readGitOutput(run, ['rev-parse', '--short', 'HEAD'], repoDir);
  const branch = readGitOutput(run, ['branch', '--show-current'], repoDir);
  const commitTime = readGitOutput(run, ['show', '-s', '--format=%cI', 'HEAD'], repoDir);
  return { repoDir, branch, headSha, shortSha, commitTime };
}

export function getHeadCommitMessage(repoDir, _spawnSync = spawnSync) {
  const run = makeRunner(_spawnSync);
  return readGitOutput(run, ['show', '-s', '--format=%B', 'HEAD'], repoDir);
}

export function isBotAutoCommit(repoDir, _spawnSync = spawnSync) {
  return getHeadCommitMessage(repoDir, _spawnSync).includes(BOT_COMMIT_MARKER);
}

/**
 * Clone PR head branch to workspace/repo (idempotent)
 */
export function cloneRepo(workspace, _spawnSync = spawnSync) {
  const run = makeRunner(_spawnSync);
  const repoDir = path.join(workspace, 'repo');

  return withAskpass(workspace, credEnv => {
    if (!fs.existsSync(repoDir)) {
      run(['clone', '--depth=1', '--branch', PR_HEAD_BRANCH, remoteUrl, repoDir], workspace, credEnv);
      ok(`repo cloned to ${repoDir}`);
    } else {
      run(['fetch', 'origin', PR_HEAD_BRANCH], repoDir, credEnv);
      run(['checkout', PR_HEAD_BRANCH], repoDir);
      ok('repo already exists, fetched latest');
    }
    return repoDir;
  });
}

export async function commitAndPush(workspace, repoDir, _spawnSync = spawnSync, sourceRoot = ACTION_ROOT, reviewOutcome = 'success') {
  const run = makeRunner(_spawnSync);

  try {
    await withAskpass(workspace, async credEnv => {
      run(['config', 'user.email', 'ai-review[bot]@gitea'], repoDir);
      run(['config', 'user.name', 'AI Review Bot'], repoDir);
      if (PR_HEAD_BRANCH) {
        run(['fetch', 'origin', PR_HEAD_BRANCH], repoDir, credEnv);
        run(['reset', '--hard', `origin/${PR_HEAD_BRANCH}`], repoDir);
      }

      const existingSyncPaths = new Set();
      const aiMergeAssistant = await getInstructionMergeAssistant();

      // Copy action skill trees into the target repo. Existing files are merged with
      // the action source; missing source files are ignored so we do not delete
      // target repo content.
      for (const relDir of SYNC_TREE_PATHS) {
        for (const relPath of syncTree(sourceRoot, repoDir, relDir)) {
          existingSyncPaths.add(relPath);
        }
      }

      // Merge only the direct instruction files that must preserve repository-specific
      // skills, commands, and rules. Everything else keeps the source copy.
      for (const relPath of FORCE_SYNC_FILE_PATHS) {
        const copied = MERGE_SYNC_FILE_PATHS.has(relPath)
          ? await syncInstructionFile(sourceRoot, repoDir, relPath, aiMergeAssistant)
          : syncFileOverwrite(sourceRoot, repoDir, relPath);
        if (copied) existingSyncPaths.add(copied);
      }

      // Merge standalone action files into the target repo.
      for (const relPath of SYNC_PATHS) {
        if (FORCE_SYNC_FILE_PATHS.includes(relPath)) continue;
        const copied = syncFileOverwrite(sourceRoot, repoDir, relPath);
        if (copied) existingSyncPaths.add(copied);
      }

      if (existingSyncPaths.size > 0) {
        run(['add', ...existingSyncPaths], repoDir);
      }
      const generatedSyncPaths = GENERATED_SYNC_PATHS.filter(relPath => fs.existsSync(path.join(workspace, relPath)));
      if (generatedSyncPaths.length > 0) {
        for (const relPath of generatedSyncPaths) {
          const src = path.join(workspace, relPath);
          const dest = path.join(repoDir, relPath);
          fs.mkdirSync(path.dirname(dest), { recursive: true });
          fs.copyFileSync(src, dest);
        }
        run(['add', ...generatedSyncPaths], repoDir);
      }

      const status = run(['status', '--porcelain'], repoDir);
      if (!status) {
        line('sync files 無變更，跳過 commit');
        return;
      }

      const outcomeTag = reviewOutcome === 'failure' ? '[failure]' : '[success]';
      const out = run(['commit', '-m', `chore: update ai-review findings ${BOT_COMMIT_MARKER}${outcomeTag}`], repoDir);
      const commitHash = out.match(/\[.+ ([a-f0-9]+)\]/)?.[1] || 'unknown';
      try {
        run(['push', remoteUrl, PR_HEAD_BRANCH], repoDir, credEnv);
        ok(`persisted findings commit=${commitHash} push=${PR_HEAD_BRANCH} review_outcome=${reviewOutcome}`);
      } catch (pushErr) {
        warn(`Step7 commit 成功但 push 失敗: commit=${commitHash} push=${PR_HEAD_BRANCH} review_outcome=${reviewOutcome} error=${pushErr.message}`);
      }
    });
  } catch (e) {
    warn(`Runner failed: commit/push 失敗: ${e.message}`);
  }
}