import { AlbumWithRefsWithId, ArtistWithRefsWithId, TagWithRefsWithId, TrackWithRefs } from "../../../client/src/api/api";
import { userEndpoints } from "../../endpoints/User";
import { createTrack, deleteTrack, ReferenceDatabase } from "./DBReferenceModel";
import * as helpers from '../integration/helpers';
import { DBErrorKind, isDBError } from "../../endpoints/types";

export enum DBActionType {
    CreateTrack = 0,
    DeleteTrack, 
}

export interface DBAction {
    type: DBActionType,
    userId: number,
    payload: any,
}

export type Distribution<T> = Map<T, number>;

export interface RandomDBActionDistribution {
    type: Distribution<DBActionType>,
    userId: Distribution<number>,
    createTrackParams: RandomCreateTrackDistribution,
    deleteTrackParams: RandomDeleteTrackDistribution,
}

export interface RandomCreateTrackDistribution {
    linkArtists: {
        numValid: Distribution<number>,
        numInvalid: Distribution<number>,
    }
    linkTags: {
        numValid: Distribution<number>,
        numInvalid: Distribution<number>,
    }
    linkAlbum: Distribution<boolean | 'nonexistent'>,
}

export interface RandomDeleteTrackDistribution {
    validTrack: Distribution<boolean>,
}

export function applyDistribution<T>(
    dist: Map<T, number>,
    randomNumGen: any,
): T {
    let n = randomNumGen();
    let r: T | undefined = undefined;
    dist.forEach((value: number, key: T) => {
        if (r) { return; }
        if (n <= value) { r = key; }
        else { n -= value; }
    })
    if (r === undefined) {
        throw new Error(`Invalid distribution: n=${n}, dist ${JSON.stringify(dist.entries())}`);
    }
    return r;
}

export function randomString(randomNumGen: any, length: number) {
    let chars = 'abcdefghijklmnopqrstuvwxyz';
    let retval = '';
    for (let i = 0; i < length; i++) {
        retval += chars[Math.floor(randomNumGen() * 26)];
    }
    return retval;
}

export function pickNFromArray<T>(
    array: T[],
    randomNumGen: any,
    N: number)
    : T[] {
    let r: T[] = [];
    for (let i = 0; i < N; i++) {
        let idx = Math.floor(randomNumGen() * array.length);
        r.push(array[idx]);
        array.splice(idx);
    }
    return r;
}

export function applyReferenceDBAction(
    action: DBAction,
    db: ReferenceDatabase
): {
    response: any,
    status: number,
} {
    let response: any = undefined;
    let status: number = 0;

    try {
        switch (action.type) {
            case DBActionType.CreateTrack: {
                response = createTrack(action.userId, action.payload, db);
                status = 200;
                break;
            }
            case DBActionType.DeleteTrack: {
                deleteTrack(action.userId, action.payload, db);
                response = {};
                status = 200;
                break;
            }
        }
    } catch(e) {
        if(isDBError(e)) {
            if(e.kind === DBErrorKind.ResourceNotFound) {
                status = 404;
                response = {};
            }
        }
    }

    return { response: response, status: status };
}

export async function applyRealDBAction(
    action: DBAction,
    req: any,
): Promise<{
    response: any,
    status: number,
}> {
    let response: any = undefined;
    let status: number = 0;

    switch (action.type) {
        case DBActionType.CreateTrack: {
            let res = await helpers.createTrack(req, action.payload);
            status = res.status;
            response = res.body;
            break;
        }
        case DBActionType.DeleteTrack: {
            let res = await helpers.deleteTrack(req, action.payload);
            status = res.status;
            response = res.body;
            break;
        }
    }

    return { response: response, status: status };
}

export function randomDBAction(
    db: ReferenceDatabase,
    randomNumGen: any,
    distribution: RandomDBActionDistribution,
): DBAction {
    let type = applyDistribution(
        distribution.type,
        randomNumGen
    );
    let userId = applyDistribution(
        distribution.userId,
        randomNumGen
    );

    switch (type) {
        case DBActionType.CreateTrack: {
            return {
                type: type,
                payload: createRandomTrack(
                    db,
                    userId,
                    distribution.createTrackParams,
                    randomNumGen
                ),
                userId: userId,
            };
        }
        case DBActionType.DeleteTrack: {
            return {
                type: type,
                payload: applyDistribution(distribution.deleteTrackParams.validTrack, randomNumGen) ?
                    Math.floor(Math.random() * db[userId].tracks.length) + 1 :
                    Math.floor(Math.random() * db[userId].tracks.length) + 1 + db[userId].tracks.length,
                userId: userId,
            }
        }
    }
}

export function createRandomTrack(
    db: ReferenceDatabase,
    userId: number,
    trackDist: RandomCreateTrackDistribution,
    randomNumGen: any,
): TrackWithRefs {
    let allValidArtistIds: number[] = db[userId] && db[userId].artists ?
        db[userId].artists.map((a: ArtistWithRefsWithId) => a.id) : [];
    let allValidTagIds: number[] = db[userId] && db[userId].tags ?
        db[userId].tags.map((a: TagWithRefsWithId) => a.id) : [];
    let allValidAlbumIds: number[] = db[userId] && db[userId].albums ?
        db[userId].albums.map((a: AlbumWithRefsWithId) => a.id) : [];

    let artists: number[] = (() => {
        let validArtists: number[] = pickNFromArray(allValidArtistIds, randomNumGen, applyDistribution(trackDist.linkArtists.numValid, randomNumGen));
        let invalidArtists: number[] = [];
        for (let i = 0; i < applyDistribution(trackDist.linkArtists.numInvalid, randomNumGen); i++) {
            invalidArtists.push(Math.round(Math.random() * 100) + allValidArtistIds.length);
        }
        return [...validArtists, ...invalidArtists];
    })();

    let tags: number[] = (() => {
        let validTags: number[] = pickNFromArray(allValidTagIds, randomNumGen, applyDistribution(trackDist.linkTags.numValid, randomNumGen));
        let invalidTags: number[] = [];
        for (let i = 0; i < applyDistribution(trackDist.linkTags.numInvalid, randomNumGen); i++) {
            invalidTags.push(Math.round(Math.random() * 100) + allValidTagIds.length);
        }
        return [...validTags, ...invalidTags];
    })();

    let maybeAlbum: number | null = (() => {
        let r: boolean | null | 'nonexistent' = applyDistribution(trackDist.linkAlbum, randomNumGen);
        let maybeValidAlbum: number | null =
            r === true &&
                allValidAlbumIds.length ?
                pickNFromArray(allValidAlbumIds, randomNumGen, 1)[0] :
                null;
        let maybeInvalidAlbum: number | null =
            r === 'nonexistent' ?
                allValidAlbumIds.length + 1 : null;
        return maybeValidAlbum || maybeInvalidAlbum;
    })();

    return {
        mbApi_typename: 'track',
        albumId: maybeAlbum,
        artistIds: artists,
        tagIds: tags,
        name: randomString(randomNumGen, 20),
        storeLinks: [], // TODO
    }
}