import crypto from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { TextDecoder } from 'node:util';

export const SKILL_PACK_SCHEMA_VERSION = 'agc-skill-pack.v1';
export const EXPECTED_SKILL_NAMES = Object.freeze([
  'agc-browser-playtest',
  'agc-client-projection',
  'agc-game-production-workflow',
  'agc-project-structure',
  'agc-web-game-development',
  'taonier-art-assets',
]);

const utf8Decoder = new TextDecoder('utf-8', { fatal: true });
const defaultRoot = path.resolve(
  path.dirname(fileURLToPath(import.meta.url)),
  '../src-tauri/resources/agc-skills',
);

function canonicalTextBytes(filePath) {
  const decoded = utf8Decoder.decode(fs.readFileSync(filePath));
  return Buffer.from(decoded.replaceAll('\r\n', '\n'), 'utf8');
}

export function isSafeSkillRelativePath(value) {
  if (
    typeof value !== 'string' ||
    value.length === 0 ||
    value.includes('\\') ||
    value.includes(':') ||
    value.startsWith('/')
  ) {
    return false;
  }
  return value
    .split('/')
    .every(
      (segment) => segment.length > 0 && segment !== '.' && segment !== '..',
    );
}

function skillFilePath(rootDir, skillName, relativePath) {
  if (!isSafeSkillRelativePath(relativePath)) {
    throw new Error(`Skill ${skillName} 包含不安全相对路径: ${relativePath}`);
  }
  const target = path.resolve(rootDir, skillName, ...relativePath.split('/'));
  const skillRoot = path.resolve(rootDir, skillName);
  const prefix = `${skillRoot}${path.sep}`;
  if (!target.startsWith(prefix)) {
    throw new Error(`Skill ${skillName} 路径越过审核根目录: ${relativePath}`);
  }
  return target;
}

export function computeSkillContentFingerprint(rootDir, entry) {
  const digest = crypto.createHash('sha256');
  for (const relativePath of [...entry.files].sort()) {
    const filePath = skillFilePath(rootDir, entry.name, relativePath);
    const bytes = canonicalTextBytes(filePath);
    digest.update(relativePath, 'utf8');
    digest.update(Buffer.from([0]));
    digest.update(bytes);
    digest.update(Buffer.from([0]));
  }
  return digest.digest('hex');
}

function collectBundledFiles(rootDir) {
  const files = [];
  const walk = (directory, prefix) => {
    for (const entry of fs.readdirSync(directory, { withFileTypes: true })) {
      const relativePath = prefix ? `${prefix}/${entry.name}` : entry.name;
      const absolutePath = path.join(directory, entry.name);
      if (entry.isSymbolicLink()) {
        throw new Error(`内置 AGC Skill 不允许符号链接: ${relativePath}`);
      }
      if (entry.isDirectory()) {
        walk(absolutePath, relativePath);
      } else if (entry.isFile()) {
        files.push(relativePath.replaceAll('\\', '/'));
      } else {
        throw new Error(`内置 AGC Skill 文件类型不受支持: ${relativePath}`);
      }
    }
  };
  walk(rootDir, '');
  return files.filter((file) => file !== 'manifest.json').sort();
}

function readManifest(rootDir) {
  const manifestPath = path.join(rootDir, 'manifest.json');
  return {
    manifestPath,
    manifest: JSON.parse(fs.readFileSync(manifestPath, 'utf8')),
  };
}

function validateManifestShape(rootDir, manifest) {
  if (manifest?.schemaVersion !== SKILL_PACK_SCHEMA_VERSION) {
    throw new Error('内置 AGC Skill 清单 schemaVersion 不受支持');
  }
  if (typeof manifest.version !== 'string' || manifest.version.trim() === '') {
    throw new Error('内置 AGC Skill 清单缺少版本');
  }
  if (!Array.isArray(manifest.skills)) {
    throw new Error('内置 AGC Skill 清单缺少 skills 数组');
  }
  const names = manifest.skills.map((entry) => entry?.name);
  if (
    names.length !== EXPECTED_SKILL_NAMES.length ||
    [...names].sort().join('\n') !== [...EXPECTED_SKILL_NAMES].sort().join('\n')
  ) {
    throw new Error('内置 AGC Skill 清单不等于审核白名单');
  }

  const declaredFiles = new Set();
  const mismatches = [];
  for (const entry of manifest.skills) {
    if (
      typeof entry.name !== 'string' ||
      !Array.isArray(entry.files) ||
      entry.files.length === 0 ||
      !entry.files.includes('SKILL.md') ||
      new Set(entry.files).size !== entry.files.length
    ) {
      throw new Error(
        `内置 AGC Skill ${entry.name ?? '<unknown>'} 元数据不完整`,
      );
    }
    for (const relativePath of entry.files) {
      if (!isSafeSkillRelativePath(relativePath)) {
        throw new Error(
          `内置 AGC Skill ${entry.name} 包含不安全相对路径: ${relativePath}`,
        );
      }
      declaredFiles.add(`${entry.name}/${relativePath}`);
    }
    const actual = computeSkillContentFingerprint(rootDir, entry);
    if (actual !== entry.sha256) {
      mismatches.push({
        name: entry.name,
        expected: entry.sha256,
        actual,
      });
    }
  }

  const bundledFiles = collectBundledFiles(rootDir);
  if (
    declaredFiles.size !== bundledFiles.length ||
    [...declaredFiles].sort().join('\n') !== bundledFiles.join('\n')
  ) {
    throw new Error('内置 AGC Skill 文件集合与审核清单不一致');
  }
  return { mismatches };
}

export function inspectSkillPack(rootDir = defaultRoot) {
  const resolvedRoot = path.resolve(rootDir);
  const { manifestPath, manifest } = readManifest(resolvedRoot);
  const { mismatches } = validateManifestShape(resolvedRoot, manifest);
  return { manifestPath, manifest, mismatches };
}

function incrementPackVersion(version) {
  const match = /^(\d{4}-\d{2}-\d{2})\.(\d+)$/u.exec(version);
  if (!match) {
    throw new Error(
      `无法自动递增 Skill pack 版本 ${version}，请使用 YYYY-MM-DD.N 格式`,
    );
  }
  return `${match[1]}.${Number(match[2]) + 1}`;
}

export function syncSkillPackManifest(rootDir = defaultRoot) {
  const inspection = inspectSkillPack(rootDir);
  if (inspection.mismatches.length === 0) {
    return {
      changed: false,
      version: inspection.manifest.version,
      mismatches: [],
    };
  }

  const mismatchByName = new Map(
    inspection.mismatches.map((mismatch) => [mismatch.name, mismatch.actual]),
  );
  const nextManifest = {
    ...inspection.manifest,
    version: incrementPackVersion(inspection.manifest.version),
    skills: inspection.manifest.skills.map((entry) =>
      mismatchByName.has(entry.name)
        ? { ...entry, sha256: mismatchByName.get(entry.name) }
        : entry,
    ),
  };
  fs.writeFileSync(
    inspection.manifestPath,
    `${JSON.stringify(nextManifest, null, 2)}\n`,
    'utf8',
  );
  const verified = inspectSkillPack(rootDir);
  if (verified.mismatches.length > 0) {
    throw new Error('Skill pack manifest 同步后仍存在内容指纹不匹配');
  }
  return {
    changed: true,
    version: nextManifest.version,
    mismatches: inspection.mismatches,
  };
}