/***********************************************************************************************************************************************************************
 * File Name: task_reading_progress_sync.service.js
 * Type of Program: Service
 * Description: Backfills task_progress for read_* task requirements from course_reading_progress.
 *
 *   This covers the case where a user already completed reading a course/unit/lesson
 *   before a task requiring that item was created or assigned.
 ***********************************************************************************************************************************************************************/
'use strict';

const { Op }                = require('sequelize');
const CourseReadingProgress = require('../models/courses/course_reading_progress.mdl');
const { TaskProgress }      = require('../models/task/task_progress.mdl');

const READ_TYPE_TO_PROGRESS_TYPE = {
    read_course: 'course',
    read_unit:   'unit',
    read_lesson: 'lesson',
};

const READ_REQUIREMENT_TYPES = Object.keys(READ_TYPE_TO_PROGRESS_TYPE);

function readAttr(row, attr) {
    if (!row) return undefined;
    if (typeof row.get === 'function') return row.get(attr);
    return row[attr];
}

function normalizeRequirement(row) {
    const type = readAttr(row, 'type');
    if (!READ_REQUIREMENT_TYPES.includes(type)) return null;

    const referenceId = readAttr(row, 'reference_id');
    if (!referenceId) return null;

    return {
        task_id:        readAttr(row, 'task_id'),
        requirement_id: readAttr(row, 'requirement_id'),
        reference_id:   referenceId,
        type,
    };
}

async function hydrateReadTaskProgress(userId, requirements = [], options = {}) {
    const readRequirements = requirements
        .map(normalizeRequirement)
        .filter((req) => req && req.task_id && req.requirement_id);

    if (!readRequirements.length) return [];

    const referencesByProgressType = readRequirements.reduce((acc, req) => {
        const progressType = READ_TYPE_TO_PROGRESS_TYPE[req.type];
        if (!acc[progressType]) acc[progressType] = new Set();
        acc[progressType].add(req.reference_id);
        return acc;
    }, {});

    const where = {
        user_id: userId,
        status:  'completed',
        [Op.or]: Object.entries(referencesByProgressType).map(([type, references]) => ({
            type,
            reference_id: { [Op.in]: [...references] },
        })),
    };

    const completedReadingRows = await CourseReadingProgress.findAll({
        where,
        attributes: ['type', 'reference_id', 'completed_at'],
        transaction: options.transaction,
    });

    if (!completedReadingRows.length) return [];

    const completedReading = new Map(
        completedReadingRows.map((row) => [
            `${readAttr(row, 'type')}:${readAttr(row, 'reference_id')}`,
            readAttr(row, 'completed_at'),
        ])
    );

    const now = new Date();
    const rowsToUpsert = readRequirements.filter((req) =>
        completedReading.has(`${READ_TYPE_TO_PROGRESS_TYPE[req.type]}:${req.reference_id}`)
    );

    if (!rowsToUpsert.length) return [];

    const existingProgressRows = await TaskProgress.findAll({
        where: {
            user_id:      userId,
            completed:    true,
            requirement_id: { [Op.in]: rowsToUpsert.map((req) => req.requirement_id) },
            reference_id:   { [Op.in]: rowsToUpsert.map((req) => req.reference_id) },
        },
        attributes: ['requirement_id', 'reference_id'],
        transaction: options.transaction,
    });

    const existingProgress = new Set(
        existingProgressRows.map((row) =>
            `${readAttr(row, 'requirement_id')}:${readAttr(row, 'reference_id')}`
        )
    );

    const missingRows = rowsToUpsert.filter((req) =>
        !existingProgress.has(`${req.requirement_id}:${req.reference_id}`)
    );

    if (!missingRows.length) return [];

    await Promise.all(missingRows.map((req) =>
        TaskProgress.upsert(
            {
                task_id:        req.task_id,
                requirement_id: req.requirement_id,
                user_id:        userId,
                reference_id:   req.reference_id,
                type:           req.type,
                completed:      true,
                completed_at:   completedReading.get(`${READ_TYPE_TO_PROGRESS_TYPE[req.type]}:${req.reference_id}`) ?? now,
                createdBy:      userId,
                updatedBy:      userId,
            },
            {
                conflictFields: ['requirement_id', 'user_id', 'reference_id'],
                transaction: options.transaction,
            }
        )
    ));

    return missingRows;
}

module.exports = {
    hydrateReadTaskProgress,
    READ_REQUIREMENT_TYPES,
};