2025SELab2-project-Dwengo/backend/src/services/learning-paths/learning-path-service.ts

import dwengoApiLearningPathProvider from './dwengo-api-learning-path-provider.js';
import databaseLearningPathProvider from './database-learning-path-provider.js';
import { envVars, getEnvVar } from '../../util/envVars.js';
import {LearningObjectNode, LearningPath, LearningPathResponse} from '@dwengo-1/common/interfaces/learning-content';
import { Language } from '@dwengo-1/common/util/language';
import {Group} from "../../entities/assignments/group.entity";
import {LearningPath as LearningPathEntity} from "../../entities/content/learning-path.entity";
import {getLearningPathRepository} from "../../data/repositories";
import {LearningPathNode} from "../../entities/content/learning-path-node.entity";
import {LearningPathTransition} from "../../entities/content/learning-path-transition.entity";
import {base64ToArrayBuffer} from "../../util/base64-buffer-conversion";
import {TeacherDTO} from "@dwengo-1/common/interfaces/teacher";
import {mapToTeacher} from "../../interfaces/teacher";
import {Collection} from "@mikro-orm/core";

const userContentPrefix = getEnvVar(envVars.UserContentPrefix);
const allProviders = [dwengoApiLearningPathProvider, databaseLearningPathProvider];

export function mapToLearningPath(
    dto: LearningPath, adminsDto: TeacherDTO[]
): LearningPathEntity {
    const admins = adminsDto.map(admin => mapToTeacher(admin));
    const repo = getLearningPathRepository();
    const path = repo.create({
        hruid: dto.hruid,
        language: dto.language as Language,
        description: dto.description,
        title: dto.title,
        admins,
        image: dto.image ? Buffer.from(base64ToArrayBuffer(dto.image)) : null
    });
    const nodes = dto.nodes.map((nodeDto: LearningObjectNode, i: number) =>
        repo.createNode({
            learningPath: path,
            learningObjectHruid: nodeDto.learningobject_hruid,
            nodeNumber: i,
            language: nodeDto.language,
            version: nodeDto.version,
            startNode: nodeDto.start_node ?? false,
            createdAt: new Date(),
            updatedAt: new Date()
        })
    );
    dto.nodes.forEach(nodeDto => {
        const fromNode = nodes.find(it =>
            it.learningObjectHruid === nodeDto.learningobject_hruid
            && it.language === nodeDto.language
            && it.version === nodeDto.version
        )!;
        const transitions = nodeDto.transitions.map((transDto, i) => {
            const toNode = nodes.find(it =>
                it.learningObjectHruid === transDto.next.hruid
                && it.language === transDto.next.language
                && it.version === transDto.next.version
            );

            if (toNode) {
                return repo.createTransition({
                    transitionNumber: i,
                    node: fromNode,
                    next: toNode,
                    condition: transDto.condition ?? "true"
                });
            } else {
                return undefined;
            }
        }).filter(it => it).map(it => it!);

        fromNode.transitions = new Collection<LearningPathTransition>(fromNode, transitions);
    });

    path.nodes = new Collection<LearningPathNode>(path, nodes);

    return path;
}

/**
 * Service providing access to data about learning paths from the appropriate data source (database or Dwengo-api)
 */
const learningPathService = {
    /**
     * Fetch the learning paths with the given hruids from the data source.
     * @param hruids For each of the hruids, the learning path will be fetched.
     * @param language This is the language each of the learning paths will use.
     * @param source
     * @param personalizedFor If this is set, a learning path personalized for the given group or student will be returned.
     */
    async fetchLearningPaths(
        hruids: string[],
        language: Language,
        source: string,
        personalizedFor?: Group
    ): Promise<LearningPathResponse> {
        const userContentHruids = hruids.filter((hruid) => hruid.startsWith(userContentPrefix));
        const nonUserContentHruids = hruids.filter((hruid) => !hruid.startsWith(userContentPrefix));

        const userContentLearningPaths = await databaseLearningPathProvider.fetchLearningPaths(userContentHruids, language, source, personalizedFor);
        const nonUserContentLearningPaths = await dwengoApiLearningPathProvider.fetchLearningPaths(
            nonUserContentHruids,
            language,
            source,
            personalizedFor
        );

        const result = (userContentLearningPaths.data || []).concat(nonUserContentLearningPaths.data || []);

        return {
            data: result,
            source: source,
            success: userContentLearningPaths.success || nonUserContentLearningPaths.success,
        };
    },

    /**
     * Search learning paths in the data source using the given search string.
     */
    async searchLearningPaths(query: string, language: Language, personalizedFor?: Group): Promise<LearningPath[]> {
        const providerResponses = await Promise.all(
            allProviders.map(async (provider) => provider.searchLearningPaths(query, language, personalizedFor))
        );
        return providerResponses.flat();
    },

    /**
     * Add a new learning path to the database.
     * @param dto Learning path DTO from which the learning path will be created.
     * @param admins Teachers who should become an admin of the learning path.
     */
    async createNewLearningPath(dto: LearningPath, admins: TeacherDTO[]): Promise<void> {
        const repo = getLearningPathRepository();
        const path = mapToLearningPath(dto, admins);
        await repo.save(path, {preventOverwrite: true})
    }
};

export default learningPathService;