import { readFile } from 'fs-extra';
import path from 'path';
import frontmatter from 'front-matter';
import marked from 'marked';
import hljs from 'highlight.js';
import { quadrantsMap } from '../src/config';
import { radarPath, getAllMarkdownFiles } from './file';
import { Item, Revision, ItemAttributes, Radar, FlagType, Ring } from '../src/model';

type FMAttributes = ItemAttributes

marked.setOptions({
  highlight: code => hljs.highlightAuto(code).value,
});

export const createRadar = async (): Promise<Radar> => {
  const fileNames = await getAllMarkdownFiles(radarPath());
  const revisions = await createRevisionsFromFiles(fileNames);
  const allReleases = getAllReleases(revisions);
  const items = createItems(revisions);
  const flaggedItems = flagItem(items, allReleases);

  return {
    items: flaggedItems,
    releases: allReleases,
  };
};

const checkAttributes = (fileName: string, attributes: FMAttributes) => {
  const validQuadrants = Object.keys(quadrantsMap);

  if (attributes.ring && !Ring[attributes.ring]) {
    throw new Error(`Error: ${fileName} has an illegal value for 'ring' - must be one of ${Object.values(Ring)}`);
  }

  if (attributes.quadrant && !validQuadrants.includes(attributes.quadrant)) {
    throw new Error(`Error: ${fileName} has an illegal value for 'quadrant' - must be one of ${validQuadrants}`);
  }

  if (!attributes.quadrant || attributes.quadrant === '') {
    // throw new Error(`Error: ${fileName} has no 'quadrant' set`);
  }

  if (!attributes.title || attributes.title === '') {
    attributes.title = path.basename(fileName);
  }

  return attributes
};

const createRevisionsFromFiles = (fileNames: string[]) =>
  Promise.all(
    fileNames.map(fileName => {
      return new Promise<Revision>((resolve, reject) => {
        readFile(fileName, 'utf8', (err, data) => {
          if (err) {
            reject(err);
          } else {
            const fm = frontmatter<FMAttributes>(data);
            // add target attribute to external links
            // todo: check path
            let html = marked(fm.body.replace(/\]\(\//g, '](/techradar/'));
            html = html.replace(
              /a href="http/g,
              'a target="_blank" rel="noopener noreferrer" href="http',
            );

            resolve({
              ...itemInfoFromFilename(fileName),
              ...checkAttributes(fileName, fm.attributes),
              fileName,
              body: html,
            } as Revision);
          }
        });
      });
    }),
  );

const itemInfoFromFilename = (fileName: string) => {
  const [release, nameWithSuffix] = fileName.split(path.sep).slice(-2);
  return {
    name: nameWithSuffix.substr(0, nameWithSuffix.length - 3),
    release,
  };
};

const getAllReleases = (revisions: Revision[]) =>
  revisions
    .reduce<string[]>((allReleases, { release }) => {
      if (!allReleases.includes(release)) {
        return [...allReleases, release];
      }
      return allReleases;
    }, [])
    .sort();

const createItems = (revisions: Revision[]) => {
  const itemMap = revisions.reduce<{[name: string]: Item}>((items, revision) => {
    return {
      ...items,
      [revision.name]: addRevisionToItem(items[revision.name], revision),
    };
  }, {});

  return Object.values(itemMap).sort((x, y) => (x.name > y.name ? 1 : -1));
};

const ignoreEmptyRevisionBody = (revision: Revision, item: Item) => {
  if (!revision.body || revision.body.trim() === '') {
    return item.body;
  }
  return revision.body;
};

const addRevisionToItem = (
  item: Item = {
    flag: FlagType.default,
    featured: true,
    revisions: [],
    name: '',
    title: '',
    ring: Ring.trial,
    quadrant: '',
    body: '',
    info: '',
  },
  revision: Revision,
): Item => {
  let newItem: Item = {
    ...item,
    ...revision,
    body: ignoreEmptyRevisionBody(revision, item),
  };

  if (revisionCreatesNewHistoryEntry(revision)) {
    newItem = {
      ...newItem,
      revisions: [revision, ...newItem.revisions],
    };
  }

  return newItem;
};

const revisionCreatesNewHistoryEntry = (revision: Revision) => {
  return revision.body.trim() !== '' || typeof revision.ring !== 'undefined';
};

const flagItem = (items: Item[], allReleases: string[]) =>
  items.map(
    item => ({
      ...item,
      flag: getItemFlag(item, allReleases),
    } as Item),
    [],
  );

const isInLastRelease = (item: Item, allReleases: string[]) =>
  item.revisions[0].release === allReleases[allReleases.length - 1];

const isNewItem = (item: Item, allReleases: string[]) =>
  item.revisions.length === 1 && isInLastRelease(item, allReleases);

const hasItemChanged = (item: Item, allReleases: string[]) =>
  item.revisions.length > 1 && isInLastRelease(item, allReleases);

const getItemFlag = (item: Item, allReleases: string[]): string => {
  if (isNewItem(item, allReleases)) {
    return FlagType.new;
  }
  if (hasItemChanged(item, allReleases)) {
    return FlagType.changed;
  }
  return FlagType.default;
};