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

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

export default 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');
  }

  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;
    });
  }

  urlFor(path, options) {
    const params = [];
    if (options.params) {
      for (const key in options.params) {
        params.push(`${key}=${encodeURIComponent(options.params[key])}`);
      }
    }
    if (params.length) {
      path += `?${params.join('&')}`;
    }
    return API_ROOT + path;
  }

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

      return response.text();
    });
  }

  checkMetadataRef() {
    return this.request(`${this.repoURL}/git/refs/meta/_netlify_cms?${Date.now()}`, {
      cache: 'no-store',
    })
    .then(response => response.object)
    .catch(error => {
      // Meta ref doesn't exist
      const readme = {
        raw: '# Netlify CMS\n\nThis tree is used by the Netlify CMS to store metadata information for specific files and branches.'
      };

      return this.uploadBlob(readme)
      .then(item => this.request(`${this.repoURL}/git/trees`, {
        method: 'POST',
        body: JSON.stringify({ tree: [{ path: 'README.md', mode: '100644', type: 'blob', sha: item.sha }] })
      }))
      .then(tree => this.commit('First Commit', tree))
      .then(response => this.createRef('meta', '_netlify_cms', response.sha))
      .then(response => response.object);
    });
  }

  storeMetadata(key, data) {
    return this.checkMetadataRef()
    .then((branchData) => {
      const fileTree = {
        [`${key}.json`]: {
          path: `${key}.json`,
          raw: JSON.stringify(data),
          file: true
        }
      };

      return this.uploadBlob(fileTree[`${key}.json`])
      .then(item => this.updateTree(branchData.sha, '/', fileTree))
      .then(changeTree => this.commit(`Updating “${key}” metadata`, changeTree))
      .then(response => this.patchRef('meta', '_netlify_cms', response.sha));
    });
  }

  retrieveMetadata(key, data) {
    const cache = LocalForage.getItem(`gh.meta.${key}`);
    return cache.then((cached) => {
      if (cached && cached.expires > Date.now()) { return cached.data; }

      return this.request(`${this.repoURL}/contents/${key}.json?ref=refs/meta/_netlify_cms`, {
        headers: { Accept: 'application/vnd.github.VERSION.raw' },
        cache: 'no-store',
      }).then((result) => {
        LocalForage.setItem(`gh.meta.${key}`, {
          expires: Date.now() + 300000, // In 5 minutes
          data: result,
        });
        return result;
      });
    }).catch(error => null);
  }

  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' },
        params: { 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}`, {
      params: { ref: this.branch }
    });
  }

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

    const files = mediaFiles.concat(entry);

    files.forEach((file) => {
      if (file.uploaded) { return; }
      uploadPromises.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(uploadPromises)
      .then(() => this.getBranch())
      .then(branchData => this.updateTree(branchData.commit.sha, '/', fileTree))
      .then(changeTree => this.commit(options.commitMessage, changeTree))
      .then((response) => {
        if (options.mode && options.mode === BRANCH) {
          const contentKey = options.collectionName ? `${options.collectionName}-${entry.slug}` : entry.slug;
          const branchName = `cms/${contentKey}`;
          return this.createBranch(branchName, response.sha)
          .then(this.storeMetadata(contentKey, {
            type: 'PR',
            status: 'draft',
            branch: branchName,
            title: options.parsedData.title,
            description: options.parsedData.description,
            objects: files.map(file => file.path)
          }))
          .then(this.createPR(options.commitMessage, `cms/${contentKey}`));
        } else {
          return this.patchBranch(this.branch, response.sha);
        }
      });
  }

  createRef(type, name, sha) {
    return this.request(`${this.repoURL}/git/refs`, {
      method: 'POST',
      body: JSON.stringify({ ref: `refs/${type}/${name}`, sha }),
    });
  }

  createBranch(branchName, sha) {
    return this.createRef('heads', branchName, sha);
  }

  patchRef(type, name, sha) {
    return this.request(`${this.repoURL}/git/refs/${type}/${name}`, {
      method: 'PATCH',
      body: JSON.stringify({ sha })
    });
  }

  patchBranch(branchName, sha) {
    return this.patchRef('heads', branchName, sha);
  }

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

  createPR(title, head, base = 'master') {
    const body = 'Automatically generated by Netlify CMS';
    return this.request(`${this.repoURL}/pulls`, {
      method: 'POST',
      body: JSON.stringify({ title, body, head, base }),
    });
  }

  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 };
          });
      });
  }

  commit(message, changeTree) {
    const tree = changeTree.sha;
    const parents = changeTree.parentSha ? [changeTree.parentSha] : [];
    return this.request(`${this.repoURL}/git/commits`, {
      method: 'POST',
      body: JSON.stringify({ message, tree, parents })
    });
  }

}