import { Base64 } from 'js-base64';
import semaphore, { Semaphore } from 'semaphore';
import { flow, get, initial, last, partial, result, differenceBy, trimStart, trim } from 'lodash';
import { map, filter } from 'lodash/fp';
import {
  getAllResponses,
  APIError,
  EditorialWorkflowError,
  flowAsync,
  localForage,
  onlySuccessfulPromises,
  basename,
  AssetProxy,
  Entry as LibEntry,
  PersistOptions,
  readFile,
  CMS_BRANCH_PREFIX,
  generateContentKey,
  DEFAULT_PR_BODY,
  MERGE_COMMIT_MESSAGE,
  PreviewState,
  FetchError,
} from 'netlify-cms-lib-util';
import { Octokit } from '@octokit/rest';

type GitHubUser = Octokit.UsersGetAuthenticatedResponse;
type GitHubRepo = Octokit.ReposGetResponse;
type GitHubBranch = Octokit.ReposGetBranchResponse;
type GitHubBlob = Octokit.GitGetBlobResponse;
type GitHubTree = Octokit.GitCreateTreeResponse;
type GitCreateTreeParamsTree = Octokit.GitCreateTreeParamsTree;
type GitHubCommit = Octokit.GitCreateCommitResponse;
type GitHubCompareCommit = Octokit.ReposCompareCommitsResponseCommitsItem;
type ReposCompareCommitsResponseFilesItem = Octokit.ReposCompareCommitsResponseFilesItem;
type GitHubCompareResponse = Octokit.ReposCompareCommitsResponse;
type GitHubCompareBaseCommit = Octokit.ReposCompareCommitsResponseBaseCommit;
type GitHubAuthor = Octokit.GitCreateCommitResponseAuthor;
type GitHubCommitter = Octokit.GitCreateCommitResponseCommitter;
type ReposListStatusesForRefResponseItem = Octokit.ReposListStatusesForRefResponseItem;

const CURRENT_METADATA_VERSION = '1';

export const API_NAME = 'GitHub';

export interface Config {
  apiRoot?: string;
  token?: string;
  branch?: string;
  useOpenAuthoring?: boolean;
  repo?: string;
  originRepo?: string;
  squashMerges: boolean;
  initialWorkflowStatus: string;
}

interface TreeFile {
  type: 'blob' | 'tree';
  sha: string;
  path: string;
  raw?: string;
}

export interface Entry extends LibEntry {
  sha?: string;
}

type Override<T, U> = Pick<T, Exclude<keyof T, keyof U>> & U;

type TreeEntry = Override<GitCreateTreeParamsTree, { sha: string | null }>;

type GitHubCompareCommits = GitHubCompareCommit[];

type GitHubCompareFile = ReposCompareCommitsResponseFilesItem & { previous_filename?: string };

type GitHubCompareFiles = GitHubCompareFile[];

enum GitHubCommitStatusState {
  Error = 'error',
  Failure = 'failure',
  Pending = 'pending',
  Success = 'success',
}

type GitHubCommitStatus = ReposListStatusesForRefResponseItem & {
  state: GitHubCommitStatusState;
};

export interface PR {
  number: number;
  head: string | { sha: string };
}

interface MetaDataObjects {
  entry: { path: string; sha: string };
  files: MediaFile[];
}

export interface Metadata {
  type: string;
  objects: MetaDataObjects;
  branch: string;
  status: string;
  pr?: PR;
  collection: string;
  commitMessage: string;
  version?: string;
  user: string;
  title?: string;
  description?: string;
  timeStamp: string;
}

export interface Branch {
  ref: string;
}

export interface BlobArgs {
  sha: string;
  repoURL: string;
  parseText: boolean;
}

type Param = string | number | undefined;

type Options = RequestInit & { params?: Record<string, Param | Record<string, Param>> };

const replace404WithEmptyArray = (err: FetchError) => {
  if (err && err.status === 404) {
    console.log('This 404 was expected and handled appropriately.');
    return [];
  } else {
    return Promise.reject(err);
  }
};

type MediaFile = {
  sha: string;
  path: string;
};

export default class API {
  apiRoot: string;
  token: string;
  branch: string;
  useOpenAuthoring?: boolean;
  repo: string;
  originRepo: string;
  repoURL: string;
  originRepoURL: string;
  mergeMethod: string;
  initialWorkflowStatus: string;

  _userPromise?: Promise<GitHubUser>;
  _metadataSemaphore?: Semaphore;

  commitAuthor?: {};

  constructor(config: Config) {
    this.apiRoot = config.apiRoot || 'https://api.github.com';
    this.token = config.token || '';
    this.branch = config.branch || 'master';
    this.useOpenAuthoring = config.useOpenAuthoring;
    this.repo = config.repo || '';
    this.originRepo = config.originRepo || this.repo;
    this.repoURL = `/repos/${this.repo}`;
    // when not in 'useOpenAuthoring' mode originRepoURL === repoURL
    this.originRepoURL = `/repos/${this.originRepo}`;
    this.mergeMethod = config.squashMerges ? 'squash' : 'merge';
    this.initialWorkflowStatus = config.initialWorkflowStatus;
  }

  static DEFAULT_COMMIT_MESSAGE = 'Automatically generated by Netlify CMS';

  user(): Promise<{ name: string; login: string }> {
    if (!this._userPromise) {
      this._userPromise = this.request('/user') as Promise<GitHubUser>;
    }
    return this._userPromise;
  }

  hasWriteAccess() {
    return this.request(this.repoURL)
      .then((repo: GitHubRepo) => repo.permissions.push)
      .catch((error: Error) => {
        console.error('Problem fetching repo data from GitHub');
        throw error;
      });
  }

  reset() {
    // no op
  }

  requestHeaders(headers = {}) {
    const baseHeader: Record<string, string> = {
      'Content-Type': 'application/json; charset=utf-8',
      ...headers,
    };

    if (this.token) {
      baseHeader.Authorization = `token ${this.token}`;
      return Promise.resolve(baseHeader);
    }

    return Promise.resolve(baseHeader);
  }

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

      return json;
    });
  }

  urlFor(path: string, options: Options) {
    const cacheBuster = new Date().getTime();
    const params = [`ts=${cacheBuster}`];
    if (options.params) {
      for (const key in options.params) {
        params.push(`${key}=${encodeURIComponent(options.params[key] as string)}`);
      }
    }
    if (params.length) {
      path += `?${params.join('&')}`;
    }
    return this.apiRoot + path;
  }

  parseResponse(response: Response) {
    const contentType = response.headers.get('Content-Type');
    if (contentType && contentType.match(/json/)) {
      return this.parseJsonResponse(response);
    }
    const textPromise = response.text().then(text => {
      if (!response.ok) {
        return Promise.reject(text);
      }
      return text;
    });
    return textPromise;
  }

  handleRequestError(error: FetchError, responseStatus: number) {
    throw new APIError(error.message, responseStatus, API_NAME);
  }

  async request(
    path: string,
    options: Options = {},
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    parser = (response: Response) => this.parseResponse(response),
  ) {
    const headers = await this.requestHeaders(options.headers || {});
    const url = this.urlFor(path, options);
    let responseStatus: number;
    return fetch(url, { ...options, headers })
      .then(response => {
        responseStatus = response.status;
        return parser(response);
      })
      .catch(error => this.handleRequestError(error, responseStatus));
  }

  nextUrlProcessor() {
    return (url: string) => url;
  }

  async requestAllPages<T>(url: string, options: Options = {}) {
    const headers = await this.requestHeaders(options.headers || {});
    const processedURL = this.urlFor(url, options);
    const allResponses = await getAllResponses(
      processedURL,
      { ...options, headers },
      'next',
      this.nextUrlProcessor(),
    );
    const pages: T[][] = await Promise.all(
      allResponses.map((res: Response) => this.parseResponse(res)),
    );
    return ([] as T[]).concat(...pages);
  }

  generateContentKey(collectionName: string, slug: string) {
    if (!this.useOpenAuthoring) {
      return generateContentKey(collectionName, slug);
    }

    return `${this.repo}/${collectionName}/${slug}`;
  }

  slugFromContentKey(contentKey: string, collectionName: string) {
    if (!this.useOpenAuthoring) {
      return contentKey.substring(collectionName.length + 1);
    }

    return contentKey.substring(this.repo.length + collectionName.length + 2);
  }

  generateBranchName(contentKey: string) {
    return `${CMS_BRANCH_PREFIX}/${contentKey}`;
  }

  branchNameFromRef(ref: string) {
    return ref.substring('refs/heads/'.length);
  }

  contentKeyFromRef(ref: string) {
    return ref.substring(`refs/heads/${CMS_BRANCH_PREFIX}/`.length);
  }

  checkMetadataRef() {
    return this.request(`${this.repoURL}/git/refs/meta/_netlify_cms`, {
      cache: 'no-store',
    })
      .then(response => response.object)
      .catch(() => {
        // 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);
      });
  }

  async storeMetadata(key: string, data: Metadata) {
    // semaphore ensures metadata updates are always ordered, even if
    // calls to storeMetadata are not. concurrent metadata updates
    // will result in the metadata branch being unable to update.
    if (!this._metadataSemaphore) {
      this._metadataSemaphore = semaphore(1);
    }
    return new Promise((resolve, reject) =>
      this._metadataSemaphore?.take(async () => {
        try {
          const branchData = await this.checkMetadataRef();
          const file = { path: `${key}.json`, raw: JSON.stringify(data) };

          await this.uploadBlob(file);
          const changeTree = await this.updateTree(branchData.sha, [file as TreeFile]);
          const { sha } = await this.commit(`Updating “${key}” metadata`, changeTree);
          await this.patchRef('meta', '_netlify_cms', sha);
          localForage.setItem(`gh.meta.${key}`, {
            expires: Date.now() + 300000, // In 5 minutes
            data,
          });
          this._metadataSemaphore?.leave();
          resolve();
        } catch (err) {
          reject(err);
        }
      }),
    );
  }

  deleteMetadata(key: string) {
    if (!this._metadataSemaphore) {
      this._metadataSemaphore = semaphore(1);
    }
    return new Promise(resolve =>
      this._metadataSemaphore?.take(async () => {
        try {
          const branchData = await this.checkMetadataRef();
          const file = { path: `${key}.json`, sha: null };

          const changeTree = await this.updateTree(branchData.sha, [file]);
          const { sha } = await this.commit(`Deleting “${key}” metadata`, changeTree);
          await this.patchRef('meta', '_netlify_cms', sha);
          this._metadataSemaphore?.leave();
          resolve();
        } catch (err) {
          this._metadataSemaphore?.leave();
          resolve();
        }
      }),
    );
  }

  retrieveMetadata(key: string): Promise<Metadata> {
    const cache = localForage.getItem<{ data: Metadata; expires: number }>(`gh.meta.${key}`);
    return cache.then(cached => {
      if (cached && cached.expires > Date.now()) {
        return cached.data as Metadata;
      }
      console.log(
        '%c Checking for MetaData files',
        'line-height: 30px;text-align: center;font-weight: bold',
      );

      const metadataRequestOptions = {
        params: { ref: 'refs/meta/_netlify_cms' },
        headers: { Accept: 'application/vnd.github.v3.raw' },
        cache: 'no-store' as RequestCache,
      };

      const errorHandler = (err: Error) => {
        if (err.message === 'Not Found') {
          console.log(
            '%c %s does not have metadata',
            'line-height: 30px;text-align: center;font-weight: bold',
            key,
          );
        }
        throw err;
      };

      if (!this.useOpenAuthoring) {
        return this.request(`${this.repoURL}/contents/${key}.json`, metadataRequestOptions)
          .then((response: string) => JSON.parse(response))
          .catch(errorHandler);
      }

      const [user, repo] = key.split('/');
      return this.request(`/repos/${user}/${repo}/contents/${key}.json`, metadataRequestOptions)
        .then((response: string) => JSON.parse(response))
        .catch(errorHandler);
    });
  }

  async readFile(
    path: string,
    sha?: string | null,
    {
      branch = this.branch,
      repoURL = this.repoURL,
      parseText = true,
    }: {
      branch?: string;
      repoURL?: string;
      parseText?: boolean;
    } = {},
  ) {
    if (!sha) {
      sha = await this.getFileSha(path, { repoURL, branch });
    }
    const fetchContent = () => this.fetchBlobContent({ sha: sha as string, repoURL, parseText });
    const content = await readFile(sha, fetchContent, localForage, parseText);
    return content;
  }

  async fetchBlobContent({ sha, repoURL, parseText }: BlobArgs) {
    const result: GitHubBlob = await this.request(`${repoURL}/git/blobs/${sha}`);

    if (parseText) {
      // treat content as a utf-8 string
      const content = Base64.decode(result.content);
      return content;
    } else {
      // treat content as binary and convert to blob
      const content = Base64.atob(result.content);
      const byteArray = new Uint8Array(content.length);
      for (let i = 0; i < content.length; i++) {
        byteArray[i] = content.charCodeAt(i);
      }
      const blob = new Blob([byteArray]);
      return blob;
    }
  }

  async listFiles(
    path: string,
    { repoURL = this.repoURL, branch = this.branch, depth = 1 } = {},
  ): Promise<{ type: string; id: string; name: string; path: string; size: number }[]> {
    const folder = trim(path, '/');
    return this.request(`${repoURL}/git/trees/${branch}:${folder}`, {
      // GitHub API supports recursive=1 for getting the entire recursive tree
      // or omitting it to get the non-recursive tree
      params: depth > 1 ? { recursive: 1 } : {},
    })
      .then((res: GitHubTree) =>
        res.tree
          // filter only files and up to the required depth
          .filter(file => file.type === 'blob' && file.path.split('/').length <= depth)
          .map(file => ({
            type: file.type,
            id: file.sha,
            name: basename(file.path),
            path: `${folder}/${file.path}`,
            size: file.size,
          })),
      )
      .catch(replace404WithEmptyArray);
  }

  async readUnpublishedBranchFile(contentKey: string) {
    try {
      const metaData = await this.retrieveMetadata(contentKey).then(data =>
        data.objects.entry.path ? data : Promise.reject(null),
      );
      const repoURL = this.useOpenAuthoring
        ? `/repos/${contentKey
            .split('/')
            .slice(0, 2)
            .join('/')}`
        : this.repoURL;

      const [fileData, isModification] = await Promise.all([
        this.readFile(metaData.objects.entry.path, null, {
          branch: metaData.branch,
          repoURL,
        }) as Promise<string>,
        this.isUnpublishedEntryModification(metaData.objects.entry.path),
      ]);

      return {
        metaData,
        fileData,
        isModification,
        slug: this.slugFromContentKey(contentKey, metaData.collection),
      };
    } catch (e) {
      throw new EditorialWorkflowError('content is not under editorial workflow', true);
    }
  }

  isUnpublishedEntryModification(path: string) {
    return this.readFile(path, null, {
      branch: this.branch,
      repoURL: this.originRepoURL,
    })
      .then(() => true)
      .catch((err: Error) => {
        if (err.message && err.message === 'Not Found') {
          return false;
        }
        throw err;
      });
  }

  getPRsForBranchName = (branchName: string) => {
    // Get PRs with a `head` of `branchName`. Note that this is a
    // substring match, so we need to check that the `head.ref` of
    // at least one of the returned objects matches `branchName`.
    return this.requestAllPages<{ head: { ref: string } }>(`${this.repoURL}/pulls`, {
      params: {
        head: branchName,
        state: 'open',
        base: this.branch,
      },
    });
  };

  getUpdatedOpenAuthoringMetadata = async (
    contentKey: string,
    { metadata: metadataArg }: { metadata?: Metadata } = {},
  ) => {
    const metadata = metadataArg || (await this.retrieveMetadata(contentKey)) || {};
    const { pr: prMetadata, status } = metadata;

    // Set the status to draft if no corresponding PR is recorded
    if (!prMetadata && status !== 'draft') {
      const newMetadata = { ...metadata, status: 'draft' };
      this.storeMetadata(contentKey, newMetadata);
      return newMetadata;
    }

    // If no status is recorded, but there is a PR, check if the PR is
    // closed or not and update the status accordingly.
    if (prMetadata) {
      const { number: prNumber } = prMetadata;
      const originPRInfo = await this.getPullRequest(prNumber);
      const { state: currentState, merged_at: mergedAt } = originPRInfo;
      if (currentState === 'closed' && mergedAt) {
        // The PR has been merged; delete the unpublished entry
        const { collection } = metadata;
        const slug = this.slugFromContentKey(contentKey, collection);
        this.deleteUnpublishedEntry(collection, slug);
        return;
      } else if (currentState === 'closed' && !mergedAt) {
        if (status !== 'draft') {
          const newMetadata = { ...metadata, status: 'draft' };
          await this.storeMetadata(contentKey, newMetadata);
          return newMetadata;
        }
      } else {
        if (status !== 'pending_review') {
          // PR is open and has not been merged
          const newMetadata = { ...metadata, status: 'pending_review' };
          await this.storeMetadata(contentKey, newMetadata);
          return newMetadata;
        }
      }
    }

    return metadata;
  };

  async migrateToVersion1(branch: Branch, metaData: Metadata) {
    // hard code key/branch generation logic to ignore future changes
    const oldContentKey = branch.ref.substring(`refs/heads/cms/`.length);
    const newContentKey = `${metaData.collection}/${oldContentKey}`;
    const newBranchName = `cms/${newContentKey}`;

    // create new branch and pull request in new format
    const newBranch = await this.createBranch(newBranchName, (metaData.pr as PR).head as string);
    const pr = await this.createPR(metaData.commitMessage, newBranchName);

    // store new metadata
    await this.storeMetadata(newContentKey, {
      ...metaData,
      pr: {
        number: pr.number,
        head: pr.head.sha,
      },
      branch: newBranchName,
      version: '1',
    });

    // remove old data
    await this.closePR(metaData.pr as PR);
    await this.deleteBranch(metaData.branch);
    await this.deleteMetadata(oldContentKey);

    return newBranch;
  }

  async migrateBranch(branch: Branch) {
    const metadata = await this.retrieveMetadata(this.contentKeyFromRef(branch.ref));
    if (!metadata.version) {
      // migrate branch from cms/slug to cms/collection/slug
      branch = await this.migrateToVersion1(branch, metadata);
    }

    return branch;
  }

  async listUnpublishedBranches(): Promise<Branch[]> {
    console.log(
      '%c Checking for Unpublished entries',
      'line-height: 30px;text-align: center;font-weight: bold',
    );

    try {
      const branches: Branch[] = await this.request(`${this.repoURL}/git/refs/heads/cms`).catch(
        replace404WithEmptyArray,
      );

      let filterFunction;
      if (this.useOpenAuthoring) {
        const getUpdatedOpenAuthoringBranches = flow([
          map(async (branch: Branch) => {
            const contentKey = this.contentKeyFromRef(branch.ref);
            const metadata = await this.getUpdatedOpenAuthoringMetadata(contentKey);
            // filter out removed entries
            if (!metadata) {
              return Promise.reject('Unpublished entry was removed');
            }
            return branch;
          }),
          onlySuccessfulPromises,
        ]);
        filterFunction = getUpdatedOpenAuthoringBranches;
      } else {
        const prs = await this.getPRsForBranchName(CMS_BRANCH_PREFIX);
        const onlyBranchesWithOpenPRs = flowAsync([
          filter(({ ref }: Branch) => prs.some(pr => pr.head.ref === this.branchNameFromRef(ref))),
          map((branch: Branch) => this.migrateBranch(branch)),
          onlySuccessfulPromises,
        ]);

        filterFunction = onlyBranchesWithOpenPRs;
      }

      return await filterFunction(branches);
    } catch (err) {
      console.log(
        '%c No Unpublished entries',
        'line-height: 30px;text-align: center;font-weight: bold',
      );
      throw err;
    }
  }

  /**
   * Retrieve statuses for a given SHA. Unrelated to the editorial workflow
   * concept of entry "status". Useful for things like deploy preview links.
   */
  async getStatuses(sha: string) {
    try {
      const resp: { statuses: GitHubCommitStatus[] } = await this.request(
        `${this.originRepoURL}/commits/${sha}/status`,
      );
      return resp.statuses.map(s => ({
        context: s.context,
        // eslint-disable-next-line @typescript-eslint/camelcase
        target_url: s.target_url,
        state:
          s.state === GitHubCommitStatusState.Success ? PreviewState.Success : PreviewState.Other,
      }));
    } catch (err) {
      if (err && err.message && err.message === 'Ref not found') {
        return [];
      }
      throw err;
    }
  }

  async persistFiles(entry: Entry | null, mediaFiles: AssetProxy[], options: PersistOptions) {
    const files = entry ? mediaFiles.concat(entry) : mediaFiles;
    const uploadPromises = files.map(file => this.uploadBlob(file));
    await Promise.all(uploadPromises);

    if (!options.useWorkflow) {
      return this.getDefaultBranch()
        .then(branchData =>
          this.updateTree(branchData.commit.sha, files as { sha: string; path: string }[]),
        )
        .then(changeTree => this.commit(options.commitMessage, changeTree))
        .then(response => this.patchBranch(this.branch, response.sha));
    } else {
      const mediaFilesList = (mediaFiles as { sha: string; path: string }[]).map(
        ({ sha, path }) => ({
          path: trimStart(path, '/'),
          sha,
        }),
      );
      return this.editorialWorkflowGit(
        files as TreeFile[],
        entry as Entry,
        mediaFilesList,
        options,
      );
    }
  }

  getFileSha(path: string, { repoURL = this.repoURL, branch = this.branch } = {}) {
    /**
     * We need to request the tree first to get the SHA. We use extended SHA-1
     * syntax (<rev>:<path>) to get a blob from a tree without having to recurse
     * through the tree.
     */

    const pathArray = path.split('/');
    const filename = last(pathArray);
    const directory = initial(pathArray).join('/');
    const fileDataPath = encodeURIComponent(directory);
    const fileDataURL = `${repoURL}/git/trees/${branch}:${fileDataPath}`;

    return this.request(fileDataURL, { cache: 'no-store' }).then((resp: GitHubTree) => {
      const file = resp.tree.find(file => file.path === filename);
      if (file) {
        return file.sha;
      }
      throw new APIError('Not Found', 404, API_NAME);
    });
  }

  deleteFile(path: string, message: string) {
    if (this.useOpenAuthoring) {
      return Promise.reject('Cannot delete published entries as an Open Authoring user!');
    }

    const branch = this.branch;

    return this.getFileSha(path, { branch }).then(sha => {
      const params: { sha: string; message: string; branch: string; author?: { date: string } } = {
        sha,
        message,
        branch,
      };
      const opts = { method: 'DELETE', params };
      if (this.commitAuthor) {
        opts.params.author = {
          ...this.commitAuthor,
          date: new Date().toISOString(),
        };
      }
      const fileURL = `${this.repoURL}/contents/${path}`;
      return this.request(fileURL, opts);
    });
  }

  async createBranchAndPullRequest(branchName: string, sha: string, commitMessage: string) {
    await this.createBranch(branchName, sha);
    return this.createPR(commitMessage, branchName);
  }

  async editorialWorkflowGit(
    files: TreeFile[],
    entry: Entry,
    mediaFilesList: MediaFile[],
    options: PersistOptions,
  ) {
    const contentKey = this.generateContentKey(options.collectionName as string, entry.slug);
    const branchName = this.generateBranchName(contentKey);
    const unpublished = options.unpublished || false;
    if (!unpublished) {
      // Open new editorial review workflow for this entry - Create new metadata and commit to new branch
      const userPromise = this.user();
      const branchData = await this.getDefaultBranch();
      const changeTree = await this.updateTree(branchData.commit.sha, files);
      const commitResponse = await this.commit(options.commitMessage, changeTree);

      let pr;
      if (this.useOpenAuthoring) {
        await this.createBranch(branchName, commitResponse.sha);
      } else {
        pr = await this.createBranchAndPullRequest(
          branchName,
          commitResponse.sha,
          options.commitMessage,
        );
      }

      const user = await userPromise;
      return this.storeMetadata(contentKey, {
        type: 'PR',
        pr: pr
          ? {
              number: pr.number,
              head: pr.head && pr.head.sha,
            }
          : undefined,
        user: user.name || user.login,
        status: options.status || this.initialWorkflowStatus,
        branch: branchName,
        collection: options.collectionName as string,
        commitMessage: options.commitMessage,
        title: options.parsedData && options.parsedData.title,
        description: options.parsedData && options.parsedData.description,
        objects: {
          entry: {
            path: entry.path,
            sha: entry.sha as string,
          },
          files: mediaFilesList,
        },
        timeStamp: new Date().toISOString(),
        version: CURRENT_METADATA_VERSION,
      });
    } else {
      // Entry is already on editorial review workflow - just update metadata and commit to existing branch
      const metadata = await this.retrieveMetadata(contentKey);
      // mark media files to remove
      const metadataMediaFiles: MediaFile[] = get(metadata, 'objects.files', []);
      const mediaFilesToRemove: { path: string; sha: string | null }[] = differenceBy(
        metadataMediaFiles,
        mediaFilesList,
        'path',
      ).map(file => ({ ...file, type: 'blob', sha: null }));

      // rebase the branch before applying new changes
      const rebasedHead = await this.rebaseBranch(branchName);
      const treeFiles = mediaFilesToRemove.concat(files);
      const changeTree = await this.updateTree(rebasedHead.sha, treeFiles);
      const commit = await this.commit(options.commitMessage, changeTree);
      const { title, description } = options.parsedData || {};

      const pr = metadata.pr ? { ...metadata.pr, head: commit.sha } : undefined;
      const objects = {
        entry: { path: entry.path, sha: entry.sha as string },
        files: mediaFilesList,
      };

      const updatedMetadata = { ...metadata, pr, title, description, objects };

      await this.storeMetadata(contentKey, updatedMetadata);
      return this.patchBranch(branchName, commit.sha, { force: true });
    }
  }

  async compareBranchToDefault(
    branchName: string,
  ): Promise<{ baseCommit: GitHubCompareBaseCommit; commits: GitHubCompareCommits }> {
    const headReference = await this.getHeadReference(branchName);
    const { base_commit: baseCommit, commits }: GitHubCompareResponse = await this.request(
      `${this.originRepoURL}/compare/${this.branch}...${headReference}`,
    );
    return { baseCommit, commits };
  }

  async getCommitsDiff(baseSha: string, headSha: string): Promise<GitHubCompareFiles> {
    const { files }: GitHubCompareResponse = await this.request(
      `${this.repoURL}/compare/${baseSha}...${headSha}`,
    );
    return files;
  }

  async rebaseSingleCommit(baseCommit: GitHubCompareCommit, commit: GitHubCompareCommit) {
    // first get the diff between the commits
    const files = await this.getCommitsDiff(commit.parents[0].sha, commit.sha);
    const treeFiles = files.reduce((arr, file) => {
      if (file.status === 'removed') {
        // delete the file
        arr.push({ sha: null, path: file.filename });
      } else if (file.status === 'renamed') {
        // delete the previous file
        arr.push({ sha: null, path: file.previous_filename as string });
        // add the renamed file
        arr.push({ sha: file.sha, path: file.filename });
      } else {
        // add the  file
        arr.push({ sha: file.sha, path: file.filename });
      }
      return arr;
    }, [] as { sha: string | null; path: string }[]);

    // create a tree with baseCommit as the base with the diff applied
    const tree = await this.updateTree(baseCommit.sha, treeFiles);
    const { message, author, committer } = commit.commit;

    // create a new commit from the updated tree
    return (this.createCommit(
      message,
      tree.sha,
      [baseCommit.sha],
      author,
      committer,
    ) as unknown) as GitHubCompareCommit;
  }

  /**
   * Rebase an array of commits one-by-one, starting from a given base SHA
   */
  async rebaseCommits(baseCommit: GitHubCompareCommit, commits: GitHubCompareCommits) {
    /**
     * If the parent of the first commit already matches the target base,
     * return commits as is.
     */
    if (commits.length === 0 || commits[0].parents[0].sha === baseCommit.sha) {
      const head = last(commits) as GitHubCompareCommit;
      return head;
    } else {
      /**
       * Re-create each commit over the new base, applying each to the previous,
       * changing only the parent SHA and tree for each, but retaining all other
       * info, such as the author/committer data.
       */
      const newHeadPromise = commits.reduce((lastCommitPromise, commit) => {
        return lastCommitPromise.then(newParent => {
          const parent = newParent;
          const commitToRebase = commit;
          return this.rebaseSingleCommit(parent, commitToRebase);
        });
      }, Promise.resolve(baseCommit));
      return newHeadPromise;
    }
  }

  async rebaseBranch(branchName: string) {
    try {
      // Get the diff between the default branch the published branch
      const { baseCommit, commits } = await this.compareBranchToDefault(branchName);
      // Rebase the branch based on the diff
      const rebasedHead = await this.rebaseCommits(baseCommit, commits);
      return rebasedHead;
    } catch (error) {
      console.error(error);
      throw error;
    }
  }

  /**
   * Get a pull request by PR number.
   */
  getPullRequest(prNumber: number) {
    return this.request(`${this.originRepoURL}/pulls/${prNumber} }`);
  }

  async updateUnpublishedEntryStatus(collectionName: string, slug: string, status: string) {
    const contentKey = this.generateContentKey(collectionName, slug);
    const metadata = await this.retrieveMetadata(contentKey);

    if (!this.useOpenAuthoring) {
      return this.storeMetadata(contentKey, {
        ...metadata,
        status,
      });
    }

    if (status === 'pending_publish') {
      throw new Error('Open Authoring entries may not be set to the status "pending_publish".');
    }

    const { pr: prMetadata } = metadata;
    if (prMetadata) {
      const { number: prNumber } = prMetadata;
      const originPRInfo = await this.getPullRequest(prNumber);
      const { state } = originPRInfo;
      if (state === 'open' && status === 'draft') {
        await this.closePR(prMetadata);
        return this.storeMetadata(contentKey, {
          ...metadata,
          status,
        });
      }

      if (state === 'closed' && status === 'pending_review') {
        await this.openPR(prMetadata);
        return this.storeMetadata(contentKey, {
          ...metadata,
          status,
        });
      }
    }

    if (!prMetadata && status === 'pending_review') {
      const branchName = this.generateBranchName(contentKey);
      const commitMessage = metadata.commitMessage || API.DEFAULT_COMMIT_MESSAGE;
      const { number, head } = await this.createPR(commitMessage, branchName);
      return this.storeMetadata(contentKey, {
        ...metadata,
        pr: { number, head },
        status,
      });
    }
  }

  async deleteUnpublishedEntry(collectionName: string, slug: string) {
    const contentKey = this.generateContentKey(collectionName, slug);
    const branchName = this.generateBranchName(contentKey);
    return this.retrieveMetadata(contentKey)
      .then(metadata => (metadata && metadata.pr ? this.closePR(metadata.pr) : Promise.resolve()))
      .then(() => this.deleteBranch(branchName))
      .then(() => this.deleteMetadata(contentKey));
  }

  async publishUnpublishedEntry(collectionName: string, slug: string) {
    const contentKey = this.generateContentKey(collectionName, slug);
    const branchName = this.generateBranchName(contentKey);
    const metadata = await this.retrieveMetadata(contentKey);
    await this.mergePR(metadata.pr as PR, metadata.objects);
    await this.deleteBranch(branchName);
    await this.deleteMetadata(contentKey);

    return metadata;
  }

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

  patchRef(type: string, name: string, sha: string, opts: { force?: boolean } = {}) {
    const force = opts.force || false;
    return this.request(`${this.repoURL}/git/refs/${type}/${encodeURIComponent(name)}`, {
      method: 'PATCH',
      body: JSON.stringify({ sha, force }),
    });
  }

  deleteRef(type: string, name: string) {
    return this.request(`${this.repoURL}/git/refs/${type}/${encodeURIComponent(name)}`, {
      method: 'DELETE',
    });
  }

  getDefaultBranch(): Promise<GitHubBranch> {
    return this.request(`${this.originRepoURL}/branches/${encodeURIComponent(this.branch)}`);
  }

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

  assertCmsBranch(branchName: string) {
    return branchName.startsWith(`${CMS_BRANCH_PREFIX}/`);
  }

  patchBranch(branchName: string, sha: string, opts: { force?: boolean } = {}) {
    const force = opts.force || false;
    if (force && !this.assertCmsBranch(branchName)) {
      throw Error(`Only CMS branches can be force updated, cannot force update ${branchName}`);
    }
    return this.patchRef('heads', branchName, sha, { force });
  }

  deleteBranch(branchName: string) {
    return this.deleteRef('heads', branchName).catch((err: Error) => {
      // If the branch doesn't exist, then it has already been deleted -
      // deletion should be idempotent, so we can consider this a
      // success.
      if (err.message === 'Reference does not exist') {
        return Promise.resolve();
      }
      console.error(err);
      return Promise.reject(err);
    });
  }

  async getHeadReference(head: string) {
    const headReference = this.useOpenAuthoring ? `${(await this.user()).login}:${head}` : head;
    return headReference;
  }

  async createPR(title: string, head: string) {
    const headReference = await this.getHeadReference(head);
    return this.request(`${this.originRepoURL}/pulls`, {
      method: 'POST',
      body: JSON.stringify({
        title,
        body: DEFAULT_PR_BODY,
        head: headReference,
        base: this.branch,
      }),
    });
  }

  async openPR(pullRequest: PR) {
    const { number } = pullRequest;
    console.log('%c Re-opening PR', 'line-height: 30px;text-align: center;font-weight: bold');
    return this.request(`${this.originRepoURL}/pulls/${number}`, {
      method: 'PATCH',
      body: JSON.stringify({
        state: 'open',
      }),
    });
  }

  closePR(pullRequest: PR) {
    const { number } = pullRequest;
    console.log('%c Deleting PR', 'line-height: 30px;text-align: center;font-weight: bold');
    return this.request(`${this.originRepoURL}/pulls/${number}`, {
      method: 'PATCH',
      body: JSON.stringify({
        state: 'closed',
      }),
    });
  }

  mergePR(pullrequest: PR, objects: MetaDataObjects) {
    const { head: headSha, number } = pullrequest;
    console.log('%c Merging PR', 'line-height: 30px;text-align: center;font-weight: bold');
    return this.request(`${this.originRepoURL}/pulls/${number}/merge`, {
      method: 'PUT',
      body: JSON.stringify({
        // eslint-disable-next-line @typescript-eslint/camelcase
        commit_message: MERGE_COMMIT_MESSAGE,
        sha: headSha,
        // eslint-disable-next-line @typescript-eslint/camelcase
        merge_method: this.mergeMethod,
      }),
    }).catch(error => {
      if (error instanceof APIError && error.status === 405) {
        return this.forceMergePR(objects);
      } else {
        throw error;
      }
    });
  }

  forceMergePR(objects: MetaDataObjects) {
    const files = objects.files.concat(objects.entry);
    let commitMessage = 'Automatically generated. Merged on Netlify CMS\n\nForce merge of:';
    files.forEach(file => {
      commitMessage += `\n* "${file.path}"`;
    });
    console.log(
      '%c Automatic merge not possible - Forcing merge.',
      'line-height: 30px;text-align: center;font-weight: bold',
    );
    return this.getDefaultBranch()
      .then(branchData => this.updateTree(branchData.commit.sha, files))
      .then(changeTree => this.commit(commitMessage, changeTree))
      .then(response => this.patchBranch(this.branch, response.sha));
  }

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

  uploadBlob(item: { raw?: string; sha?: string; toBase64?: () => Promise<string> }) {
    const content = result(item, 'toBase64', partial(this.toBase64, item.raw as string));

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

  async updateTree(baseSha: string, files: { path: string; sha: string | null }[]) {
    const tree: TreeEntry[] = files.map(file => ({
      path: trimStart(file.path, '/'),
      mode: '100644',
      type: 'blob',
      sha: file.sha,
    }));

    const newTree = await this.createTree(baseSha, tree);
    return { ...newTree, parentSha: baseSha };
  }

  createTree(baseSha: string, tree: TreeEntry[]): Promise<GitHubTree> {
    return this.request(`${this.repoURL}/git/trees`, {
      method: 'POST',
      // eslint-disable-next-line @typescript-eslint/camelcase
      body: JSON.stringify({ base_tree: baseSha, tree }),
    });
  }

  commit(message: string, changeTree: { parentSha?: string; sha: string }) {
    const parents = changeTree.parentSha ? [changeTree.parentSha] : [];
    return this.createCommit(message, changeTree.sha, parents);
  }

  createCommit(
    message: string,
    treeSha: string,
    parents: string[],
    author?: GitHubAuthor,
    committer?: GitHubCommitter,
  ): Promise<GitHubCommit> {
    return this.request(`${this.repoURL}/git/commits`, {
      method: 'POST',
      body: JSON.stringify({ message, tree: treeSha, parents, author, committer }),
    });
  }
}