const crypto = require('crypto');
const path = require('path');

const fse = require('fs-extra');
const toArrayBuffer = require('to-arraybuffer');
const { isArrayBuffer, isString } = require('lodash');

const PATH = 'attachments.noindex';

//      getPath :: AbsolutePath -> AbsolutePath
exports.getPath = userDataPath => {
  if (!isString(userDataPath)) {
    throw new TypeError("'userDataPath' must be a string");
  }
  return path.join(userDataPath, PATH);
};

//      ensureDirectory :: AbsolutePath -> IO Unit
exports.ensureDirectory = async userDataPath => {
  if (!isString(userDataPath)) {
    throw new TypeError("'userDataPath' must be a string");
  }
  await fse.ensureDir(exports.getPath(userDataPath));
};

//      createReader :: AttachmentsPath ->
//                      RelativePath ->
//                      IO (Promise ArrayBuffer)
exports.createReader = root => {
  if (!isString(root)) {
    throw new TypeError("'root' must be a path");
  }

  return async relativePath => {
    if (!isString(relativePath)) {
      throw new TypeError("'relativePath' must be a string");
    }

    const absolutePath = path.join(root, relativePath);
    const buffer = await fse.readFile(absolutePath);
    return toArrayBuffer(buffer);
  };
};

//      createWriterForNew :: AttachmentsPath ->
//                            ArrayBuffer ->
//                            IO (Promise RelativePath)
exports.createWriterForNew = root => {
  if (!isString(root)) {
    throw new TypeError("'root' must be a path");
  }

  return async arrayBuffer => {
    if (!isArrayBuffer(arrayBuffer)) {
      throw new TypeError("'arrayBuffer' must be an array buffer");
    }

    const name = exports.createName();
    const relativePath = exports.getRelativePath(name);
    return exports.createWriterForExisting(root)({
      data: arrayBuffer,
      path: relativePath,
    });
  };
};

//      createWriter :: AttachmentsPath ->
//                      { data: ArrayBuffer, path: RelativePath } ->
//                      IO (Promise RelativePath)
exports.createWriterForExisting = root => {
  if (!isString(root)) {
    throw new TypeError("'root' must be a path");
  }

  return async ({ data: arrayBuffer, path: relativePath } = {}) => {
    if (!isString(relativePath)) {
      throw new TypeError("'relativePath' must be a path");
    }

    if (!isArrayBuffer(arrayBuffer)) {
      throw new TypeError("'arrayBuffer' must be an array buffer");
    }

    const buffer = Buffer.from(arrayBuffer);
    const absolutePath = path.join(root, relativePath);
    await fse.ensureFile(absolutePath);
    await fse.writeFile(absolutePath, buffer);
    return relativePath;
  };
};

//      createDeleter :: AttachmentsPath ->
//                       RelativePath ->
//                       IO Unit
exports.createDeleter = root => {
  if (!isString(root)) {
    throw new TypeError("'root' must be a path");
  }

  return async relativePath => {
    if (!isString(relativePath)) {
      throw new TypeError("'relativePath' must be a string");
    }

    const absolutePath = path.join(root, relativePath);
    await fse.remove(absolutePath);
  };
};

//      createName :: Unit -> IO String
exports.createName = () => {
  const buffer = crypto.randomBytes(32);
  return buffer.toString('hex');
};

//      getRelativePath :: String -> Path
exports.getRelativePath = name => {
  if (!isString(name)) {
    throw new TypeError("'name' must be a string");
  }

  const prefix = name.slice(0, 2);
  return path.join(prefix, name);
};

//      createAbsolutePathGetter :: RoothPath -> RelativePath -> AbsolutePath
exports.createAbsolutePathGetter = rootPath => relativePath =>
  path.join(rootPath, relativePath);