const dotenv = require("dotenv");
const path = require("path");
const mariadb = require("mariadb");

dotenv.config({ path: path.resolve(process.cwd(), ".env") });

const {
    DB_HOST,
    DB_PORT,
    DB_USERNAME,
    DB_PASSWORD,
    DB_DATABASE,
} = process.env;

function parseArgs(argv) {
    const args = {
        dryRun: false,
        actorId: null,
        courseId: null,
        memberId: null,
    };

    for (let i = 2; i < argv.length; i++) {
        const token = argv[i];
        if (token === "--dry-run") {
            args.dryRun = true;
            continue;
        }

        if (token.startsWith("--actor=")) {
            args.actorId = Number(token.split("=")[1]);
            continue;
        }

        if (token.startsWith("--course=")) {
            args.courseId = Number(token.split("=")[1]);
            continue;
        }

        if (token.startsWith("--member=")) {
            args.memberId = Number(token.split("=")[1]);
            continue;
        }
    }

    if (args.actorId !== null && Number.isNaN(args.actorId)) {
        throw new Error("--actor must be a number");
    }
    if (args.courseId !== null && Number.isNaN(args.courseId)) {
        throw new Error("--course must be a number");
    }
    if (args.memberId !== null && Number.isNaN(args.memberId)) {
        throw new Error("--member must be a number");
    }

    return args;
}

function buildScopeClause(args, tableAlias = "") {
    const prefix = tableAlias ? `${tableAlias}.` : "";
    const clauses = [];
    const params = [];

    if (args.courseId !== null) {
        clauses.push(`${prefix}course_id = ?`);
        params.push(args.courseId);
    }

    if (args.memberId !== null) {
        clauses.push(`${prefix}member_id = ?`);
        params.push(args.memberId);
    }

    if (!clauses.length) {
        return { sql: "", params };
    }

    return {
        sql: ` AND ${clauses.join(" AND ")}`,
        params,
    };
}

function key(memberId, courseId) {
    return `${memberId}:${courseId}`;
}

(async () => {
    const args = parseArgs(process.argv);

    const conn = await mariadb.createConnection({
        host: DB_HOST,
        port: Number(DB_PORT),
        user: DB_USERNAME,
        password: DB_PASSWORD,
        database: DB_DATABASE,
        multipleStatements: false,
    });

    try {
        const schemaCheck = await conn.query("SHOW COLUMNS FROM members_qualifications LIKE 'course_id';");
        if (!schemaCheck.length) {
            throw new Error("members_qualifications.course_id does not exist. Run qualification migration first.");
        }

        const scoped = buildScopeClause(args);

        const passRows = await conn.query(
            `SELECT
                ca.attendee_id AS member_id,
                e.course_id,
                e.id AS course_event_id,
                e.event_date
             FROM course_events e
             INNER JOIN course_attendees ca ON ca.course_event_id = e.id
             WHERE ca.attendee_role_id = 2
               AND (e.deleted IS NULL OR e.deleted = 0)
               AND (
                    (e.hasBookwork = 1 AND e.hasQual = 1 AND ca.passed_bookwork = 1 AND ca.passed_qual = 1)
                    OR (e.hasBookwork = 1 AND IFNULL(e.hasQual, 0) = 0 AND ca.passed_bookwork = 1)
                    OR (IFNULL(e.hasBookwork, 0) = 0 AND e.hasQual = 1 AND ca.passed_qual = 1)
               )
               ${scoped.sql}
             ORDER BY ca.attendee_id ASC, e.course_id ASC, e.event_date DESC, e.id DESC;`,
            scoped.params
        );

        const latestByPair = new Map();
        for (const row of passRows) {
            const mapKey = key(Number(row.member_id), Number(row.course_id));
            if (!latestByPair.has(mapKey)) {
                latestByPair.set(mapKey, {
                    memberId: Number(row.member_id),
                    courseId: Number(row.course_id),
                    courseEventId: Number(row.course_event_id),
                    eventDate: row.event_date,
                });
            }
        }

        const currentRows = await conn.query(
            `SELECT member_id, course_id
             FROM members_qualifications
             WHERE active = 1
               AND (deleted IS NULL OR deleted = 0)
               ${scoped.sql};`,
            scoped.params
        );

        const currentKeys = new Set(currentRows.map((r) => key(Number(r.member_id), Number(r.course_id))));
        const nextKeys = new Set(Array.from(latestByPair.keys()));

        let wouldDeactivate = 0;
        currentKeys.forEach((k) => {
            if (!nextKeys.has(k)) {
                wouldDeactivate++;
            }
        });

        const summary = {
            dryRun: args.dryRun,
            scope: {
                memberId: args.memberId,
                courseId: args.courseId,
            },
            actorId: args.actorId,
            historicalPassingRows: passRows.length,
            activePairsComputed: latestByPair.size,
            currentlyActivePairs: currentRows.length,
            wouldDeactivate,
        };

        if (args.dryRun) {
            console.log("Qualification backfill dry run summary:");
            console.log(JSON.stringify(summary, null, 2));
            return;
        }

        await conn.beginTransaction();

        const deactivateReason = "Backfill recompute from historical training reports";

        const deactivateResult = await conn.query(
            `UPDATE members_qualifications mq
             SET mq.active = 0,
                 mq.revoked_by_id = ?,
                 mq.revoked_reason = ?,
                 mq.revoked_at = UTC_TIMESTAMP(),
                 mq.updated_at = current_timestamp()
             WHERE mq.active = 1
               AND (mq.deleted IS NULL OR mq.deleted = 0)
               ${buildScopeClause(args, "mq").sql};`,
            [args.actorId, deactivateReason].concat(buildScopeClause(args, "mq").params)
        );

        let upserts = 0;
        for (const item of latestByPair.values()) {
            await conn.query(
                `INSERT INTO members_qualifications
                    (member_id, course_id, event_date, active, awarded_by_id, revoked_by_id, revoked_reason, revoked_at, source_course_event_id, deleted)
                 VALUES (?, ?, ?, 1, ?, NULL, NULL, NULL, ?, 0)
                 ON DUPLICATE KEY UPDATE
                    event_date = VALUES(event_date),
                    active = 1,
                    awarded_by_id = VALUES(awarded_by_id),
                    revoked_by_id = NULL,
                    revoked_reason = NULL,
                    revoked_at = NULL,
                    source_course_event_id = VALUES(source_course_event_id),
                    deleted = 0,
                    updated_at = current_timestamp();`,
                [item.memberId, item.courseId, item.eventDate, args.actorId, item.courseEventId]
            );
            upserts++;
        }

        await conn.commit();

        console.log("Qualification backfill complete:");
        console.log(JSON.stringify({
            ...summary,
            deactivatedRows: deactivateResult.affectedRows,
            upserts,
        }, null, 2));
    } catch (error) {
        try {
            await conn.rollback();
        } catch (_ignored) {
            // No-op rollback failure.
        }
        console.error("Qualification backfill failed:");
        console.error(error);
        process.exitCode = 1;
    } finally {
        await conn.end();
    }
})();