import { option as O } from "fp-ts";
import * as A from "fp-ts/Array";
import { eqString } from "fp-ts/lib/Eq";
import { pipe } from "fp-ts/lib/function";
import { ordString } from "fp-ts/lib/Ord";

import {
  MusicService,
  Credentials,
  AuthSuccess,
  AuthFailure,
  Artist,
  MusicLibrary,
  ArtistQuery,
  AlbumQuery,
  slice2,
  asResult,
  artistToArtistSummary,
  albumToAlbumSummary,
  Album,
} from "../src/music_service";

type P<T> = (t: T) => boolean;
const all: P<any> = (_: any) => true;

const albumByArtist = (id: string): P<[Artist, Album]> => ([artist, _]) =>
  artist.id === id;

const albumWithGenre = (genre: string): P<[Artist, Album]> => ([_, album]) =>
  album.genre === genre;

export class InMemoryMusicService implements MusicService {
  users: Record<string, string> = {};
  artists: Artist[] = [];

  generateToken({
    username,
    password,
  }: Credentials): Promise<AuthSuccess | AuthFailure> {
    if (
      username != undefined &&
      password != undefined &&
      this.users[username] == password
    ) {
      return Promise.resolve({
        authToken: JSON.stringify({ username, password }),
        userId: username,
        nickname: username,
      });
    } else {
      return Promise.resolve({ message: `Invalid user:${username}` });
    }
  }

  login(token: string): Promise<MusicLibrary> {
    const credentials = JSON.parse(token) as Credentials;
    if (this.users[credentials.username] != credentials.password)
      return Promise.reject("Invalid auth token");

    return Promise.resolve({
      artists: (q: ArtistQuery) =>
        Promise.resolve(this.artists.map(artistToArtistSummary))
          .then(slice2(q))
          .then(asResult),
      artist: (id: string) =>
        pipe(
          this.artists.find((it) => it.id === id),
          O.fromNullable,
          O.map((it) => Promise.resolve(it)),
          O.getOrElse(() => Promise.reject(`No artist with id '${id}'`))
        ),
      albums: (q: AlbumQuery) =>
        Promise.resolve(
          this.artists
            .flatMap((artist) => artist.albums.map((album) => [artist, album]))
            .filter(
              pipe(
                pipe(O.fromNullable(q.artistId), O.map(albumByArtist)),
                O.alt(() =>
                  pipe(O.fromNullable(q.genre), O.map(albumWithGenre))
                ),
                O.getOrElse(() => all)
              )
            )
        )
          .then((matches) => matches.map(([_, album]) => album as Album))
          .then((it) => it.map(albumToAlbumSummary))
          .then(slice2(q))
          .then(asResult),
      album: (id: string) =>
        pipe(
          this.artists.flatMap((it) => it.albums).find((it) => it.id === id),
          O.fromNullable,
          O.map((it) => Promise.resolve(it)),
          O.getOrElse(() => Promise.reject(`No album with id '${id}'`))
        ),
      genres: () =>
        Promise.resolve(
          pipe(
            this.artists,
            A.map((it) => it.albums),
            A.flatten,
            A.map((it) => O.fromNullable(it.genre)),
            A.compact,
            A.uniq(eqString),
            A.sort(ordString)
          )
        ),
    });
  }

  hasUser(credentials: Credentials) {
    this.users[credentials.username] = credentials.password;
    return this;
  }

  hasNoUsers() {
    this.users = {};
    return this;
  }

  hasArtists(...newArtists: Artist[]) {
    this.artists = [...this.artists, ...newArtists];
    return this;
  }

  clear() {
    this.users = {};
    this.artists = [];
    return this;
  }
}