// (C) Copyright 2015 Moodle Pty Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import { Injectable } from '@angular/core';
import { CoreSites, CoreSitesCommonWSOptions } from '@services/sites';
import { CoreSite, CoreSiteWSPreSets } from '@classes/site';
import { CoreCourseBlock } from '@features/course/services/course';
import { CoreStatusWithWarningsWSResponse } from '@services/ws';
import { makeSingleton } from '@singletons';
import { CoreError } from '@classes/errors/error';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';
import { asyncObservable, firstValueFrom } from '@/core/utils/observables';

const ROOT_CACHE_KEY = 'CoreCoursesDashboard:';

/**
 * Service that provides some features regarding course overview.
 */
@Injectable({ providedIn: 'root' })
export class CoreCoursesDashboardProvider {

    static readonly MY_PAGE_DEFAULT = '__default';
    static readonly MY_PAGE_COURSES = '__courses';

    /**
     * Get cache key for dashboard blocks WS calls.
     *
     * @param myPage What my page to return blocks of. Default MY_PAGE_DEFAULT.
     * @param userId User ID. Default, 0 means current user.
     * @return Cache key.
     */
    protected getDashboardBlocksCacheKey(myPage = CoreCoursesDashboardProvider.MY_PAGE_DEFAULT, userId: number = 0): string {
        return ROOT_CACHE_KEY + 'blocks:' + myPage + ':' + userId;
    }

    /**
     * Get dashboard blocks from WS.
     *
     * @param myPage What my page to return blocks of. Default MY_PAGE_DEFAULT.
     * @param userId User ID. Default, current user.
     * @param siteId Site ID. If not defined, current site.
     * @return Promise resolved with the list of blocks.
     * @since 3.6
     */
    getDashboardBlocksFromWS(
        myPage = CoreCoursesDashboardProvider.MY_PAGE_DEFAULT,
        userId?: number,
        siteId?: string,
    ): Promise<CoreCourseBlock[]> {
        return firstValueFrom(this.getDashboardBlocksFromWSObservable({
            myPage,
            userId,
            siteId,
        }));
    }

    /**
     * Get dashboard blocks from WS.
     *
     * @param options Options.
     * @return Observable that returns the list of blocks.
     * @since 3.6
     */
    getDashboardBlocksFromWSObservable(options: GetDashboardBlocksOptions = {}): Observable<CoreCourseBlock[]> {
        return asyncObservable(async () => {
            const site = await CoreSites.getSite(options.siteId);

            const myPage = options.myPage ?? CoreCoursesDashboardProvider.MY_PAGE_DEFAULT;
            const params: CoreBlockGetDashboardBlocksWSParams = {
                returncontents: true,
            };
            if (CoreSites.getRequiredCurrentSite().isVersionGreaterEqualThan('4.0')) {
                params.mypage = myPage;
            } else if (myPage != CoreCoursesDashboardProvider.MY_PAGE_DEFAULT) {
                throw new CoreError('mypage param is no accessible on core_block_get_dashboard_blocks');
            }

            const preSets: CoreSiteWSPreSets = {
                cacheKey: this.getDashboardBlocksCacheKey(myPage, options.userId),
                updateFrequency: CoreSite.FREQUENCY_RARELY,
                ...CoreSites.getReadingStrategyPreSets(options.readingStrategy),
            };
            if (options.userId) {
                params.userid = options.userId;
            }

            const observable = site.readObservable<CoreBlockGetDashboardBlocksWSResponse>(
                'core_block_get_dashboard_blocks',
                params,
                preSets,
            );

            return observable.pipe(map(result => {
                if (site.isVersionGreaterEqualThan('4.0')) {
                    // Temporary hack to have course overview on 3.9.5 but not on 4.0 onwards.
                    // To be removed in a near future.
                    // Remove myoverview when is forced. See MDL-72092.
                    result.blocks = result.blocks.filter((block) =>
                        block.instanceid != 0 || block.name != 'myoverview' || block.region != 'forced');
                }

                return result.blocks || [];
            }));
        });
    }

    /**
     * Get dashboard blocks.
     *
     * @param userId User ID. Default, current user.
     * @param siteId Site ID. If not defined, current site.
     * @param myPage What my page to return blocks of. Default MY_PAGE_DEFAULT.
     * @return Promise resolved with the list of blocks.
     */
    getDashboardBlocks(
        userId?: number,
        siteId?: string,
        myPage = CoreCoursesDashboardProvider.MY_PAGE_DEFAULT,
    ): Promise<CoreCoursesDashboardBlocks> {
        return firstValueFrom(this.getDashboardBlocksObservable({
            myPage,
            userId,
            siteId,
        }));
    }

    /**
     * Get dashboard blocks.
     *
     * @param options Options.
     * @return observable that returns the list of blocks.
     */
    getDashboardBlocksObservable(options: GetDashboardBlocksOptions = {}): Observable<CoreCoursesDashboardBlocks> {
        return this.getDashboardBlocksFromWSObservable(options).pipe(map(blocks => {
            let mainBlocks: CoreCourseBlock[] = [];
            let sideBlocks: CoreCourseBlock[] = [];

            blocks.forEach((block) => {
                if (block.region == 'content' || block.region == 'main') {
                    mainBlocks.push(block);
                } else {
                    sideBlocks.push(block);
                }
            });

            if (mainBlocks.length == 0) {
                mainBlocks = [];
                sideBlocks = [];

                blocks.forEach((block) => {
                    if (block.region.match('side')) {
                        sideBlocks.push(block);
                    } else {
                        mainBlocks.push(block);
                    }
                });
            }

            return { mainBlocks, sideBlocks };
        }));
    }

    /**
     * Invalidates dashboard blocks WS call.
     *
     * @param myPage What my page to return blocks of. Default MY_PAGE_DEFAULT.
     * @param userId User ID. Default, current user.
     * @param siteId Site ID. If not defined, current site.
     * @return Promise resolved when the data is invalidated.
     */
    async invalidateDashboardBlocks(
        myPage = CoreCoursesDashboardProvider.MY_PAGE_DEFAULT,
        userId?: number,
        siteId?: string,
    ): Promise<void> {
        const site = await CoreSites.getSite(siteId);

        return site.invalidateWsCacheForKey(this.getDashboardBlocksCacheKey(myPage, userId));
    }

    /**
     * Returns whether or not block based Dashboard is available for a certain site.
     *
     * @param siteId Site ID. If not defined, current site.
     * @return Promise resolved with true if available, resolved with false or rejected otherwise.
     * @since 3.6
     */
    async isAvailable(siteId?: string): Promise<boolean> {
        const site = await CoreSites.getSite(siteId);

        return site.wsAvailable('core_block_get_dashboard_blocks');
    }

    /**
     * Check if Site Home is disabled in a certain site.
     *
     * @param siteId Site Id. If not defined, use current site.
     * @return Promise resolved with true if disabled, rejected or resolved with false otherwise.
     */
    async isDisabled(siteId?: string): Promise<boolean> {
        const site = await CoreSites.getSite(siteId);

        return this.isDisabledInSite(site);
    }

    /**
     * Check if Dashboard is disabled in a certain site.
     *
     * @param site Site. If not defined, use current site.
     * @return Whether it's disabled.
     */
    isDisabledInSite(site?: CoreSite): boolean {
        site = site || CoreSites.getCurrentSite();

        return !!site?.isFeatureDisabled('CoreMainMenuDelegate_CoreCoursesDashboard');
    }

}

export const CoreCoursesDashboard = makeSingleton(CoreCoursesDashboardProvider);

export type CoreCoursesDashboardBlocks = {
    mainBlocks: CoreCourseBlock[];
    sideBlocks: CoreCourseBlock[];
};

/**
 * Options for some get dashboard blocks calls.
 */
export type GetDashboardBlocksOptions = CoreSitesCommonWSOptions & {
    userId?: number; // User ID. If not defined, current user.
    myPage?: string; // Page to get. If not defined, CoreCoursesDashboardProvider.MY_PAGE_DEFAULT.
};

/**
 * Params of core_block_get_dashboard_blocks WS.
 */
type CoreBlockGetDashboardBlocksWSParams = {
    userid?: number; // User id (optional), default is current user.
    returncontents?: boolean; // Whether to return the block contents.
    mypage?: string; // @since 4.0. What my page to return blocks of. Default MY_PAGE_DEFAULT.
};

/**
 * Data returned by core_block_get_dashboard_blocks WS.
 */
type CoreBlockGetDashboardBlocksWSResponse = {
    blocks: CoreCourseBlock[]; // List of blocks in the course.
    warnings?: CoreStatusWithWarningsWSResponse[];
};