import fs from 'node:fs';
import fsp from 'node:fs/promises';
import path from 'node:path';

function storageError(message, code, details = {}) {
  return Object.assign(new Error(message), { code, ...details });
}

export function normalizeMindSpaceStorageKey(key) {
  const raw = String(key ?? '').trim();
  if (!raw) {
    throw storageError('storage key is required', 'invalid_storage_key');
  }
  if (raw.includes('\0')) {
    throw storageError('storage key must not contain null bytes', 'invalid_storage_key');
  }
  if (raw.includes('\\')) {
    throw storageError('storage key must use forward slashes', 'invalid_storage_key');
  }
  if (path.isAbsolute(raw) || /^[A-Za-z]:\//.test(raw)) {
    throw storageError('storage key must be relative', 'invalid_storage_key');
  }
  if (raw.split('/').includes('..')) {
    throw storageError('storage key must not traverse parent directories', 'invalid_storage_key');
  }

  const normalized = path.posix.normalize(raw.replace(/^\/+/, ''));
  if (normalized === '.' || normalized.startsWith('../') || normalized.includes('/../')) {
    throw storageError('storage key must not traverse parent directories', 'invalid_storage_key');
  }
  return normalized;
}

export function resolveStoragePath(storageRoot, key) {
  const root = path.resolve(String(storageRoot ?? ''));
  if (!root) {
    throw storageError('storage root is required', 'invalid_storage_root');
  }
  const normalizedKey = normalizeMindSpaceStorageKey(key);
  const target = path.resolve(root, ...normalizedKey.split('/'));
  if (target !== root && !target.startsWith(`${root}${path.sep}`)) {
    throw storageError('storage key resolves outside storage root', 'invalid_storage_key', {
      key: normalizedKey,
    });
  }
  return target;
}

async function walkFiles(root, dir, prefix, results) {
  const entries = await fsp.readdir(dir, { withFileTypes: true });
  for (const entry of entries) {
    const absolutePath = path.join(dir, entry.name);
    const relativePath = path.relative(root, absolutePath).split(path.sep).join('/');
    if (entry.isDirectory()) {
      await walkFiles(root, absolutePath, prefix, results);
    } else if (!prefix || relativePath === prefix || relativePath.startsWith(`${prefix}/`)) {
      const stat = await fsp.stat(absolutePath);
      results.push({
        key: relativePath,
        sizeBytes: stat.size,
        updatedAt: stat.mtimeMs,
      });
    }
  }
}

export function createLocalMindSpaceStorageAdapter(storageRoot) {
  const root = path.resolve(storageRoot);

  return {
    kind: 'local-fs',
    root,

    async putObject(key, body) {
      const target = resolveStoragePath(root, key);
      await fsp.mkdir(path.dirname(target), { recursive: true });
      await fsp.writeFile(target, body);
      const stat = await fsp.stat(target);
      return {
        key: normalizeMindSpaceStorageKey(key),
        sizeBytes: stat.size,
        updatedAt: stat.mtimeMs,
      };
    },

    async getObject(key) {
      return fsp.readFile(resolveStoragePath(root, key));
    },

    async statObject(key) {
      try {
        const stat = await fsp.stat(resolveStoragePath(root, key));
        return {
          key: normalizeMindSpaceStorageKey(key),
          exists: true,
          sizeBytes: stat.size,
          updatedAt: stat.mtimeMs,
          isDirectory: stat.isDirectory(),
        };
      } catch (error) {
        if (error?.code !== 'ENOENT') throw error;
        return {
          key: normalizeMindSpaceStorageKey(key),
          exists: false,
          sizeBytes: 0,
          updatedAt: null,
          isDirectory: false,
        };
      }
    },

    async deleteObject(key) {
      await fsp.rm(resolveStoragePath(root, key), { force: true });
      return { key: normalizeMindSpaceStorageKey(key), deleted: true };
    },

    async listObjects(prefix = '') {
      const normalizedPrefix = prefix ? normalizeMindSpaceStorageKey(prefix).replace(/\/$/, '') : '';
      const results = [];
      try {
        await walkFiles(root, root, normalizedPrefix, results);
      } catch (error) {
        if (error?.code !== 'ENOENT') throw error;
      }
      return results.sort((a, b) => a.key.localeCompare(b.key));
    },

    async copyObject(sourceKey, targetKey) {
      const source = resolveStoragePath(root, sourceKey);
      const target = resolveStoragePath(root, targetKey);
      await fsp.mkdir(path.dirname(target), { recursive: true });
      await fsp.copyFile(source, target);
      const stat = await fsp.stat(target);
      return {
        key: normalizeMindSpaceStorageKey(targetKey),
        sourceKey: normalizeMindSpaceStorageKey(sourceKey),
        sizeBytes: stat.size,
        updatedAt: stat.mtimeMs,
      };
    },

    createReadStream(key) {
      return fs.createReadStream(resolveStoragePath(root, key));
    },

    createWriteStream(key) {
      const target = resolveStoragePath(root, key);
      fs.mkdirSync(path.dirname(target), { recursive: true });
      return fs.createWriteStream(target);
    },

    async getSignedUrl() {
      throw storageError('local fs adapter does not support signed URLs', 'signed_url_not_supported');
    },
  };
}

export const mindspaceStorageAdapterInternals = {
  storageError,
};