import {
  localForage,
  parseLinkHeader,
  unsentRequest,
  then,
  APIError,
  Cursor,
} from 'netlify-cms-lib-util';
import { Base64 } from 'js-base64';
import { fromJS, Map } from 'immutable';
import { flow, partial, result } from 'lodash';

export default class API {
  constructor(config) {
    this.api_root = config.api_root || 'https://gitlab.com/api/v4';
    this.token = config.token || false;
    this.branch = config.branch || 'master';
    this.repo = config.repo || '';
    this.repoURL = `/projects/${encodeURIComponent(this.repo)}`;
  }

  withAuthorizationHeaders = req =>
    unsentRequest.withHeaders(this.token ? { Authorization: `Bearer ${this.token}` } : {}, req);

  buildRequest = req =>
    flow([
      unsentRequest.withRoot(this.api_root),
      this.withAuthorizationHeaders,
      unsentRequest.withTimestamp,
    ])(req);

  request = async req =>
    flow([
      this.buildRequest,
      unsentRequest.performRequest,
      p => p.catch(err => Promise.reject(new APIError(err.message, null, 'GitLab'))),
    ])(req);

  catchFormatErrors = (format, formatter) => res => {
    try {
      return formatter(res);
    } catch (err) {
      throw new Error(
        `Response cannot be parsed into the expected format (${format}): ${err.message}`,
      );
    }
  };

  responseFormats = fromJS({
    json: async res => {
      const contentType = res.headers.get('Content-Type');
      if (contentType !== 'application/json' && contentType !== 'text/json') {
        throw new Error(`${contentType} is not a valid JSON Content-Type`);
      }
      return res.json();
    },
    text: async res => res.text(),
    blob: async res => res.blob(),
  }).mapEntries(([format, formatter]) => [format, this.catchFormatErrors(format, formatter)]);

  parseResponse = async (res, { expectingOk = true, expectingFormat = 'text' }) => {
    let body;
    try {
      const formatter = this.responseFormats.get(expectingFormat, false);
      if (!formatter) {
        throw new Error(`${expectingFormat} is not a supported response format.`);
      }
      body = await formatter(res);
    } catch (err) {
      throw new APIError(err.message, res.status, 'GitLab');
    }
    if (expectingOk && !res.ok) {
      const isJSON = expectingFormat === 'json';
      throw new APIError(isJSON && body.message ? body.message : body, res.status, 'GitLab');
    }
    return body;
  };

  responseToJSON = res => this.parseResponse(res, { expectingFormat: 'json' });
  responseToBlob = res => this.parseResponse(res, { expectingFormat: 'blob' });
  responseToText = res => this.parseResponse(res, { expectingFormat: 'text' });
  requestJSON = req => this.request(req).then(this.responseToJSON);
  requestText = req => this.request(req).then(this.responseToText);

  user = () => this.requestJSON('/user');

  WRITE_ACCESS = 30;
  hasWriteAccess = () =>
    this.requestJSON(this.repoURL).then(({ permissions }) => {
      const { project_access, group_access } = permissions;
      if (project_access && project_access.access_level >= this.WRITE_ACCESS) {
        return true;
      }
      if (group_access && group_access.access_level >= this.WRITE_ACCESS) {
        return true;
      }
      return false;
    });

  readFile = async (path, sha, { ref = this.branch, parseText = true } = {}) => {
    const cacheKey = parseText ? `gl.${sha}` : `gl.${sha}.blob`;
    const cachedFile = sha ? await localForage.getItem(cacheKey) : null;
    if (cachedFile) {
      return cachedFile;
    }
    const result = await this.request({
      url: `${this.repoURL}/repository/files/${encodeURIComponent(path)}/raw`,
      params: { ref },
      cache: 'no-store',
    }).then(parseText ? this.responseToText : this.responseToBlob);
    if (sha) {
      localForage.setItem(cacheKey, result);
    }
    return result;
  };

  getCursorFromHeaders = headers => {
    // indices and page counts are assumed to be zero-based, but the
    // indices and page counts returned from GitLab are one-based
    const index = parseInt(headers.get('X-Page'), 10) - 1;
    const pageCount = parseInt(headers.get('X-Total-Pages'), 10) - 1;
    const pageSize = parseInt(headers.get('X-Per-Page'), 10);
    const count = parseInt(headers.get('X-Total'), 10);
    const links = parseLinkHeader(headers.get('Link'));
    const actions = Map(links)
      .keySeq()
      .flatMap(key =>
        (key === 'prev' && index > 0) ||
        (key === 'next' && index < pageCount) ||
        (key === 'first' && index > 0) ||
        (key === 'last' && index < pageCount)
          ? [key]
          : [],
      );
    return Cursor.create({
      actions,
      meta: { index, count, pageSize, pageCount },
      data: { links },
    });
  };

  getCursor = ({ headers }) => this.getCursorFromHeaders(headers);

  // Gets a cursor without retrieving the entries by using a HEAD
  // request
  fetchCursor = req =>
    flow([unsentRequest.withMethod('HEAD'), this.request, then(this.getCursor)])(req);
  fetchCursorAndEntries = req =>
    flow([
      unsentRequest.withMethod('GET'),
      this.request,
      p => Promise.all([p.then(this.getCursor), p.then(this.responseToJSON)]),
      then(([cursor, entries]) => ({ cursor, entries })),
    ])(req);
  fetchRelativeCursor = async (cursor, action) => this.fetchCursor(cursor.data.links[action]);

  reversableActions = Map({
    first: 'last',
    last: 'first',
    next: 'prev',
    prev: 'next',
  });

  reverseCursor = cursor => {
    const pageCount = cursor.meta.get('pageCount', 0);
    const currentIndex = cursor.meta.get('index', 0);
    const newIndex = pageCount - currentIndex;

    const links = cursor.data.get('links', Map());
    const reversedLinks = links.mapEntries(([k, v]) => [this.reversableActions.get(k) || k, v]);

    const reversedActions = cursor.actions.map(
      action => this.reversableActions.get(action) || action,
    );

    return cursor.updateStore(store =>
      store
        .setIn(['meta', 'index'], newIndex)
        .setIn(['data', 'links'], reversedLinks)
        .set('actions', reversedActions),
    );
  };

  // The exported listFiles and traverseCursor reverse the direction
  // of the cursors, since GitLab's pagination sorts the opposite way
  // we want to sort by default (it sorts by filename _descending_,
  // while the CMS defaults to sorting by filename _ascending_, at
  // least in the current GitHub backend). This should eventually be
  // refactored.
  listFiles = async (path, recursive = false) => {
    const firstPageCursor = await this.fetchCursor({
      url: `${this.repoURL}/repository/tree`,
      params: { path, ref: this.branch, recursive },
    });
    const lastPageLink = firstPageCursor.data.getIn(['links', 'last']);
    const { entries, cursor } = await this.fetchCursorAndEntries(lastPageLink);
    return {
      files: entries.filter(({ type }) => type === 'blob').reverse(),
      cursor: this.reverseCursor(cursor),
    };
  };

  traverseCursor = async (cursor, action) => {
    const link = cursor.data.getIn(['links', action]);
    const { entries, cursor: newCursor } = await this.fetchCursorAndEntries(link);
    return {
      entries: entries.filter(({ type }) => type === 'blob').reverse(),
      cursor: this.reverseCursor(newCursor),
    };
  };

  listAllFiles = async (path, recursive = false) => {
    const entries = [];
    let { cursor, entries: initialEntries } = await this.fetchCursorAndEntries({
      url: `${this.repoURL}/repository/tree`,
      // Get the maximum number of entries per page
      params: { path, ref: this.branch, per_page: 100, recursive },
    });
    entries.push(...initialEntries);
    while (cursor && cursor.actions.has('next')) {
      const link = cursor.data.getIn(['links', 'next']);
      const { cursor: newCursor, entries: newEntries } = await this.fetchCursorAndEntries(link);
      entries.push(...newEntries);
      cursor = newCursor;
    }
    return entries.filter(({ type }) => type === 'blob');
  };

  toBase64 = str => Promise.resolve(Base64.encode(str));
  fromBase64 = str => Base64.decode(str);
  uploadAndCommit = async (
    item,
    { commitMessage, updateFile = false, branch = this.branch, author = this.commitAuthor },
  ) => {
    const content = await result(item, 'toBase64', partial(this.toBase64, item.raw));
    const file_path = item.path.replace(/^\//, '');
    const action = updateFile ? 'update' : 'create';
    const encoding = 'base64';

    const commitParams = {
      branch,
      commit_message: commitMessage,
      actions: [{ action, file_path, content, encoding }],
    };
    if (author) {
      const { name, email } = author;
      commitParams.author_name = name;
      commitParams.author_email = email;
    }

    const response = await this.requestJSON({
      url: `${this.repoURL}/repository/commits`,
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(commitParams),
    });

    return { ...item, sha: response.id };
  };

  persistFiles = (files, { commitMessage, newEntry }) =>
    Promise.all(
      files.map(file =>
        this.uploadAndCommit(file, { commitMessage, updateFile: newEntry === false }),
      ),
    );

  deleteFile = (path, commit_message, options = {}) => {
    const branch = options.branch || this.branch;
    const commitParams = { commit_message, branch };
    if (this.commitAuthor) {
      const { name, email } = this.commitAuthor;
      commitParams.author_name = name;
      commitParams.author_email = email;
    }
    return flow([
      unsentRequest.withMethod('DELETE'),
      // TODO: only send author params if they are defined.
      unsentRequest.withParams(commitParams),
      this.request,
    ])(`${this.repoURL}/repository/files/${encodeURIComponent(path)}`);
  };
}