import * as fs from 'fs';

import config from '../config';
import { DangerJS } from './types';
import { DangerDSLType } from 'danger';

const CHANGELOG_FILE = 'packages/fluentui/CHANGELOG.md';

/**
 * This function asserts that added entries into the changelog file are placed in the right section.
 */
const hasAddedLinesAfterVersionInChangelog = async (danger: DangerDSLType): Promise<boolean> => {
  const changelogContent = fs.readFileSync(config.paths.base(CHANGELOG_FILE)).toString();
  const versionLineNumber = changelogContent
    .split('\n')
    .findIndex(line => line.startsWith('<!--') && line.endsWith('-->'));

  const addedLines = await getAddedLinesFromChangelog(danger);

  return addedLines.some(line => line.ln > versionLineNumber);
};

const getMalformedChangelogEntries = async (danger: DangerDSLType): Promise<string[]> => {
  // +- description @githubname ([#DDDD](https://github.com/microsoft/fluentui/pull/DDDD))
  const validEntry = /^\+- .*@\S+ \(\[#(\d+)]\(https:\/\/github\.com\/microsoft\/fluentui\/pull\/\1\)\)$/;

  const addedLines = await getAddedLinesFromChangelog(danger);

  return addedLines.map(line => line.content).filter(content => content.startsWith('+-') && !validEntry.test(content));
};

const getAddedLinesFromChangelog = async (danger: DangerDSLType): Promise<{ content: string; ln: number }[]> => {
  return danger.git.structuredDiffForFile(CHANGELOG_FILE).then(changelogDiff => {
    if (changelogDiff) {
      return changelogDiff.chunks.reduce((acc, chunk) => {
        const filteredLines = chunk.changes.filter((change: any) => change.type === 'add');
        return acc.concat(filteredLines);
      }, []);
    }

    return [];
  });
};

export default async ({ danger, fail, warn }: DangerJS) => {
  // Check for a CHANGELOG entry for changes inside /packages/fluentui
  const changes = [...danger.git.created_files, ...danger.git.deleted_files, ...danger.git.modified_files].filter(
    f => f !== CHANGELOG_FILE,
  );

  if (changes.some(f => f.startsWith('packages/fluentui'))) {
    const hasChangelog = danger.git.modified_files.some(f => f === CHANGELOG_FILE);

    if (!hasChangelog) {
      warn(
        'There are no updates provided to CHANGELOG. Ensure there are no publicly visible changes introduced by this PR.',
      );
    } else {
      const malformedChangelogEntries = await getMalformedChangelogEntries(danger);
      malformedChangelogEntries.forEach(entry => {
        fail(`Invalid entry format in ${CHANGELOG_FILE}: >${entry}<

The correct format is: \`- description @githubname ([#DDDD](https://github.com/microsoft/fluentui/pull/DDDD)\``);
      });

      const hasLine = await hasAddedLinesAfterVersionInChangelog(danger);
      if (hasLine) {
        fail(`All of your entries in ${CHANGELOG_FILE} should be in the **Unreleased** section!`);
      }
    }
  }
};