pf_app/routes/log.js

const express = require('express');
const { fcTable } = require('../lib/utils');

module.exports = function(pool) {
    const router = express.Router();

    // list all log entries for a version, newest first
    router.get('/versions/:id/log', async (req, res) => {
        try {
            const result = await pool.query(
                `SELECT * FROM pf.log WHERE version_id = $1 ORDER BY stamp DESC`,
                [req.params.id]
            );
            res.json(result.rows);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // undo an operation — deletes all forecast rows with this logid, then the log entry
    // two separate queries in a transaction to avoid FK ordering issues
    router.delete('/log/:logid', async (req, res) => {
        const logid = parseInt(req.params.logid);
        const client = await pool.connect();
        try {
            // look up the log entry to find the version and fc_table name
            const logResult = await client.query(`
                SELECT l.*, v.id AS version_id, s.tname
                FROM pf.log l
                JOIN pf.version v ON v.id = l.version_id
                JOIN pf.source  s ON s.id = v.source_id
                WHERE l.id = $1
            `, [logid]);

            if (logResult.rows.length === 0) {
                return res.status(404).json({ error: 'Log entry not found' });
            }

            const { tname, version_id } = logResult.rows[0];
            const table = fcTable(tname, version_id);

            await client.query('BEGIN');
            // delete forecast rows first (logid has no FK constraint — managed by app)
            const del = await client.query(
                `DELETE FROM ${table} WHERE logid = $1 RETURNING id`,
                [logid]
            );
            await client.query(`DELETE FROM pf.log WHERE id = $1`, [logid]);
            await client.query('COMMIT');

            res.json({ message: 'Operation undone', rows_deleted: del.rowCount });
        } catch (err) {
            await client.query('ROLLBACK');
            console.error(err);
            res.status(500).json({ error: err.message });
        } finally {
            client.release();
        }
    });

    return router;
};