/**
 * Copyright (c) 2017-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

const CWD = process.cwd();

const path = require('path');
const fs = require('fs');
const glob = require('glob');
const chalk = require('chalk');

const env = require('./env.js');
const siteConfig = require(CWD + '/siteConfig.js');
const versionFallback = require('./versionFallback.js');
const escapeStringRegexp = require('escape-string-regexp');

const SupportedHeaderFields = new Set([
  'id',
  'title',
  'author',
  'authorURL',
  'authorFBID',
  'sidebar_label',
  'original_id',
  'hide_title',
  'layout',
  'custom_edit_url',
]);

// Can have a custom docs path. Top level folder still needs to be in directory
// at the same level as `website`, not inside `website`.
//   e.g., docs/whereDocsReallyExist
//         website-docs/
// All .md docs still (currently) must be in one flat directory hierarchy.
//   e.g., docs/whereDocsReallyExist/*.md (all .md files in this dir)
function getDocsPath() {
  return siteConfig.customDocsPath ? siteConfig.customDocsPath : 'docs';
}
// returns map from id to object containing sidebar ordering info
function readSidebar() {
  let allSidebars;
  if (fs.existsSync(CWD + '/sidebars.json')) {
    allSidebars = require(CWD + '/sidebars.json');
  } else {
    allSidebars = {};
  }
  Object.assign(allSidebars, versionFallback.sidebarData());

  const order = {};

  Object.keys(allSidebars).forEach(sidebar => {
    const categories = allSidebars[sidebar];

    let ids = [];
    let categoryOrder = [];
    Object.keys(categories).forEach(category => {
      ids = ids.concat(categories[category]);
      for (let i = 0; i < categories[category].length; i++) {
        categoryOrder.push(category);
      }
    });

    for (let i = 0; i < ids.length; i++) {
      const id = ids[i];
      let previous, next;
      if (i > 0) previous = ids[i - 1];
      if (i < ids.length - 1) next = ids[i + 1];
      order[id] = {
        previous: previous,
        next: next,
        sidebar: sidebar,
        category: categoryOrder[i],
      };
    }
  });
  return order;
}

// split markdown header
function splitHeader(content) {
  // New line characters need to handle all operating systems.
  const lines = content.split(/\r?\n/);
  if (lines[0] !== '---') {
    return {};
  }
  let i = 1;
  for (; i < lines.length - 1; ++i) {
    if (lines[i] === '---') {
      break;
    }
  }
  return {
    header: lines.slice(1, i + 1).join('\n'),
    content: lines.slice(i + 1).join('\n'),
  };
}

// Extract markdown metadata header
function extractMetadata(content) {
  const metadata = {};
  const both = splitHeader(content);
  if (Object.keys(both).length === 0) {
    return {metadata, rawContent: content};
  }
  const lines = both.header.split('\n');
  for (let i = 0; i < lines.length - 1; ++i) {
    const keyvalue = lines[i].split(':');
    const key = keyvalue[0].trim();
    let value = keyvalue
      .slice(1)
      .join(':')
      .trim();
    try {
      value = JSON.parse(value);
    } catch (e) {}
    metadata[key] = value;
  }
  return {metadata, rawContent: both.content};
}

// process the metadata for a document found in the docs folder
function processMetadata(file) {
  const result = extractMetadata(fs.readFileSync(file, 'utf8'));

  let regexSubFolder = new RegExp(
    '/' + escapeStringRegexp(getDocsPath()) + '/(.*)/.*/'
  );

  const match = regexSubFolder.exec(file);
  let language = match ? match[1] : 'en';

  const metadata = {};
  for (const fieldName of Object.keys(result.metadata)) {
    if (SupportedHeaderFields.has(fieldName)) {
      metadata[fieldName] = result.metadata[fieldName];
    } else {
      console.warn(`Header field "${fieldName}" in ${file} is not supported.`);
    }
  }

  const rawContent = result.rawContent;
  metadata.source = path.basename(file);

  if (!metadata.id) {
    metadata.id = path.basename(file, path.extname(file));
  }
  if (metadata.id.includes('/')) {
    throw new Error('Document id cannot include "/".');
  }
  if (!metadata.title) {
    metadata.title = metadata.id;
  }

  const langPart =
    env.translation.enabled || siteConfig.useEnglishUrl ? language + '/' : '';
  let versionPart = '';
  if (env.versioning.enabled) {
    metadata.version = 'next';
    versionPart = 'next/';
  }

  metadata.permalink = 'docs/' + langPart + versionPart + metadata.id + '.html';

  // change ids previous, next
  metadata.localized_id = metadata.id;
  metadata.id = (env.translation.enabled ? language + '-' : '') + metadata.id;
  metadata.language = env.translation.enabled ? language : 'en';

  const order = readSidebar();
  const id = metadata.localized_id;

  if (order[id]) {
    metadata.sidebar = order[id].sidebar;
    metadata.category = order[id].category;

    if (order[id].next) {
      metadata.next_id = order[id].next;
      metadata.next =
        (env.translation.enabled ? language + '-' : '') + order[id].next;
    }
    if (order[id].previous) {
      metadata.previous_id = order[id].previous;
      metadata.previous =
        (env.translation.enabled ? language + '-' : '') + order[id].previous;
    }
  }

  return {metadata, rawContent: rawContent};
}

// process metadata for all docs and save into core/metadata.js
function generateMetadataDocs() {
  let order;
  try {
    order = readSidebar();
  } catch (e) {
    console.error(e);
    process.exit(1);
  }

  const enabledLanguages = env.translation
    .enabledLanguages()
    .map(language => language.tag);

  const metadatas = {};
  const defaultMetadatas = {};

  // metadata for english files
  let files = glob.sync(CWD + '/../' + getDocsPath() + '/**');
  files.forEach(file => {
    let language = 'en';

    const extension = path.extname(file);

    if (extension === '.md' || extension === '.markdown') {
      const res = processMetadata(file);

      if (!res) {
        return;
      }
      let metadata = res.metadata;
      metadatas[metadata.id] = metadata;

      // create a default list of documents for each enabled language based on docs in English
      // these will get replaced if/when the localized file is downloaded from crowdin
      enabledLanguages
        .filter(currentLanguage => {
          return currentLanguage != 'en';
        })
        .map(currentLanguage => {
          let baseMetadata = Object.assign({}, metadata);
          baseMetadata['id'] = baseMetadata['id']
            .toString()
            .replace(/^en-/, currentLanguage + '-');
          if (baseMetadata['permalink'])
            baseMetadata['permalink'] = baseMetadata['permalink']
              .toString()
              .replace(/^docs\/en\//, 'docs/' + currentLanguage + '/');
          if (baseMetadata['next'])
            baseMetadata['next'] = baseMetadata['next']
              .toString()
              .replace(/^en-/, currentLanguage + '-');
          if (baseMetadata['previous'])
            baseMetadata['previous'] = baseMetadata['previous']
              .toString()
              .replace(/^en-/, currentLanguage + '-');
          baseMetadata['language'] = currentLanguage;
          defaultMetadatas[baseMetadata['id']] = baseMetadata;
        });
      Object.assign(metadatas, defaultMetadatas);
    }
  });

  // metadata for non-english docs
  const regexSubFolder = /translated_docs\/(.*?)\/.*/;
  files = glob.sync(CWD + '/translated_docs/**');
  files.forEach(file => {
    let language = 'en';
    const match = regexSubFolder.exec(file);
    if (match) {
      language = match[1];
    }

    if (enabledLanguages.indexOf(language) === -1) {
      return;
    }

    const extension = path.extname(file);

    if (extension === '.md' || extension === '.markdown') {
      const res = processMetadata(file);
      if (!res) {
        return;
      }
      let metadata = res.metadata;
      metadatas[metadata.id] = metadata;
    }
  });

  // metadata for versioned docs
  const versionData = versionFallback.docData();
  versionData.forEach(metadata => {
    const id = metadata.localized_id;
    if (order[id]) {
      metadata.sidebar = order[id].sidebar;
      metadata.category = order[id].category;
      if (order[id].next) {
        metadata.next_id = order[id].next.replace(
          'version-' + metadata.version + '-',
          ''
        );
        metadata.next =
          (env.translation.enabled ? metadata.language + '-' : '') +
          order[id].next;
      }
      if (order[id].previous) {
        metadata.previous_id = order[id].previous.replace(
          'version-' + metadata.version + '-',
          ''
        );
        metadata.previous =
          (env.translation.enabled ? metadata.language + '-' : '') +
          order[id].previous;
      }
    }
    metadatas[metadata.id] = metadata;
  });

  // Get the titles of the previous and next ids so that we can use them in
  // navigation buttons in DocsLayout.js
  Object.keys(metadatas).forEach(function(metadata) {
    if (metadatas[metadata].previous) {
      if (metadatas[metadatas[metadata].previous]) {
        metadatas[metadata].previous_title =
          metadatas[metadatas[metadata].previous].title;
      } else {
        metadatas[metadata].previous_title = 'Previous';
      }
    }
    if (metadatas[metadata].next) {
      if (metadatas[metadatas[metadata].next]) {
        metadatas[metadata].next_title =
          metadatas[metadatas[metadata].next].title;
      } else {
        metadatas[metadata].next_title = 'Next';
      }
    }
  });

  fs.writeFileSync(
    __dirname + '/../core/metadata.js',
    '/**\n' +
    ' * @' +
    'generated\n' + // separate this out for Nuclide treating @generated as readonly
      ' */\n' +
      'module.exports = ' +
      JSON.stringify(metadatas, null, 2) +
      ';\n'
  );
}

// process metadata for blog posts and save into core/MetadataBlog.js
function generateMetadataBlog() {
  const metadatas = [];

  let files = glob.sync(CWD + '/blog/**/*.*');
  files
    .sort()
    .reverse()
    .forEach(file => {
      const extension = path.extname(file);
      if (extension !== '.md' && extension !== '.markdown') {
        return;
      }
      // Transform
      //   2015-08-13-blog-post-name-0.5.md
      // into
      //   2015/08/13/blog-post-name-0-5.html
      const filePath = path
        .basename(file)
        .replace('-', '/')
        .replace('-', '/')
        .replace('-', '/')
        .replace(/\.md$/, '.html');
      const result = extractMetadata(fs.readFileSync(file, {encoding: 'utf8'}));
      const rawContent = result.rawContent;
      const metadata = Object.assign(
        {path: filePath, content: rawContent},
        result.metadata
      );

      metadata.id = metadata.title;

      // Extract, YYYY, MM, DD from the file name
      let filePathDateArr = path
        .basename(file)
        .toString()
        .split('-');
      metadata.date = new Date(
        filePathDateArr[0] +
          '-' +
          filePathDateArr[1] +
          '-' +
          filePathDateArr[2] +
          'T06:00:00.000Z'
      );
      // allow easier sorting of blog by providing seconds since epoch
      metadata.seconds = Math.round(metadata.date.getTime() / 1000);

      metadatas.push(metadata);
    });

  const sortedMetadatas = metadatas.sort(
    (a, b) => parseInt(b.seconds) - parseInt(a.seconds)
  );

  fs.writeFileSync(
    __dirname + '/../core/MetadataBlog.js',
    '/**\n' +
    ' * @' +
    'generated\n' + // separate this out for Nuclide treating @generated as readonly
      ' */\n' +
      'module.exports = ' +
      JSON.stringify(sortedMetadatas, null, 2) +
      ';\n'
  );
}

module.exports = {
  getDocsPath,
  readSidebar,
  extractMetadata,
  processMetadata,
  generateMetadataDocs,
  generateMetadataBlog,
};