import LocalForage from 'localforage';
import MediaProxy from '../../valueObjects/MediaProxy';
import AuthenticationPage from './AuthenticationPage';
import { Base64 } from 'js-base64';

const API_ROOT = 'https://api.github.com';

class API {
  constructor(token, repo, branch) {
    this.token = token;
    this.repo = repo;
    this.branch = branch;
    this.repoURL = `/repos/${this.repo}`;
  }

  user() {
    return this.request('/user');
  }

  readFile(path, sha) {
    const cache = sha ? LocalForage.getItem(`gh.${sha}`) : Promise.resolve(null);
    return cache.then((cached) => {
      if (cached) { return cached; }

      return this.request(`${this.repoURL}/contents/${path}`, {
        headers: { Accept: 'application/vnd.github.VERSION.raw' },
        body: { ref: this.branch },
        cache: false
      }).then((result) => {
        if (sha) {
          LocalForage.setItem(`gh.${sha}`, result);
        }

        return result;
      });
    });
  }

  listFiles(path) {
    return this.request(`${this.repoURL}/contents/${path}`, {
      body: { ref: this.branch }
    });
  }

  persistFiles(collection, entry, mediaFiles, options) {
    let filename, part, parts, subtree;
    const fileTree = {};
    const files = [];

    mediaFiles.concat(entry).forEach((file) => {
      if (file.uploaded) { return; }
      files.push(this.uploadBlob(file));
      parts = file.path.split('/').filter((part) => part);
      filename = parts.pop();
      subtree = fileTree;
      while (part = parts.shift()) {
        subtree[part] = subtree[part] || {};
        subtree = subtree[part];
      }
      subtree[filename] = file;
      file.file = true;
    });

    return Promise.all(files)
      .then(() => this.getBranch())
      .then((branchData) => {
        return this.updateTree(branchData.commit.sha, '/', fileTree);
      })
      .then((changeTree) => {
        return this.request(`${this.repoURL}/git/commits`, {
          method: 'POST',
          body: JSON.stringify({ message: options.commitMessage, tree: changeTree.sha, parents: [changeTree.parentSha] })
        });
      }).then((response) => {
        return this.request(`${this.repoURL}/git/refs/heads/${this.branch}`, {
          method: 'PATCH',
          body: JSON.stringify({ sha: response.sha })
        });
      });
  }

  requestHeaders(headers = {}) {
    return {
      Authorization: `token ${this.token}`,
      'Content-Type': 'application/json',
      ...headers
    };
  }

  parseJsonResponse(response) {
    return response.json().then((json) => {
      if (!response.ok) {
        return Promise.reject(json);
      }

      return json;
    });
  }

  request(path, options = {}) {
    const headers = this.requestHeaders(options.headers || {});
    return fetch(API_ROOT + path, { ...options, headers: headers }).then((response) => {
      if (response.headers.get('Content-Type').match(/json/)) {
        return this.parseJsonResponse(response);
      }

      return response.text();
    });
  }

  getBranch() {
    return this.request(`${this.repoURL}/branches/${this.branch}`);
  }

  getTree(sha) {
    return sha ? this.request(`${this.repoURL}/git/trees/${sha}`) : Promise.resolve({ tree: [] });
  }

  toBase64(str) {
    return Promise.resolve(
      Base64.encode(str)
    );
  }

  uploadBlob(item) {
    const content = item instanceof MediaProxy ? item.toBase64() : this.toBase64(item.raw);

    return content.then((contentBase64) => {
      return this.request(`${this.repoURL}/git/blobs`, {
        method: 'POST',
        body: JSON.stringify({
          content: contentBase64,
          encoding: 'base64'
        })
      }).then((response) => {
        item.sha = response.sha;
        item.uploaded = true;
        return item;
      });
    });
  }

  updateTree(sha, path, fileTree) {
    return this.getTree(sha)
      .then((tree) => {
        var obj, filename, fileOrDir;
        var updates = [];
        var added = {};

        for (var i = 0, len = tree.tree.length; i < len; i++) {
          obj = tree.tree[i];
          if (fileOrDir = fileTree[obj.path]) {
            added[obj.path] = true;
            if (fileOrDir.file) {
              updates.push({ path: obj.path, mode: obj.mode, type: obj.type, sha: fileOrDir.sha });
            } else {
              updates.push(this.updateTree(obj.sha, obj.path, fileOrDir));
            }
          }
        }
        for (filename in fileTree) {
          fileOrDir = fileTree[filename];
          if (added[filename]) { continue; }
          updates.push(
            fileOrDir.file ?
              { path: filename, mode: '100644', type: 'blob', sha: fileOrDir.sha } :
              this.updateTree(null, filename, fileOrDir)
          );
        }
        return Promise.all(updates)
          .then((updates) => {
            return this.request(`${this.repoURL}/git/trees`, {
              method: 'POST',
              body: JSON.stringify({ base_tree: sha, tree: updates })
            });
          }).then((response) => {
            return { path: path, mode: '040000', type: 'tree', sha: response.sha, parentSha: sha };
          });
      });
  }

}

export default class GitHub {
  constructor(config) {
    this.config = config;
    if (config.getIn(['backend', 'repo']) == null) {
      throw 'The GitHub backend needs a "repo" in the backend configuration.';
    }
    this.repo = config.getIn(['backend', 'repo']);
  }

  authComponent() {
    return AuthenticationPage;
  }

  setUser(user) {
    this.api = new API(user.token, this.repo, this.branch || 'master');
  }

  authenticate(state) {
    this.api = new API(state.token, this.repo, this.branch || 'master');
    return this.api.user().then((user) => {
      user.token = state.token;
      return user;
    });
  }

  entries(collection) {
    return this.api.listFiles(collection.get('folder')).then((files) => (
      Promise.all(files.map((file) => (
        this.api.readFile(file.path, file.sha).then((data) => {
          file.slug = file.path.split('/').pop().replace(/\.[^\.]+$/, '');
          file.raw = data;
          return file;
        })
      )))
    )).then((entries) => ({
      pagination: {},
      entries
    }));
  }

  entry(collection, slug) {
    return this.entries(collection).then((response) => (
      response.entries.filter((entry) => entry.slug === slug)[0]
    ));
  }

  persistEntry(collection, entry, mediaFiles = [], options = {}) {
    return this.api.persistFiles(collection, entry, mediaFiles, options);
  }
}