dataflow/api/routes/stacks.js

/**
 * Stacks Routes
 * Named unions of multiple sources with field mappings and running balance
 */

const express = require('express');
const { lit } = require('../lib/sql');

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

    // List all stacks
    router.get('/', async (req, res, next) => {
        try {
            const result = await pool.query('SELECT * FROM list_stacks()');
            res.json(result.rows);
        } catch (err) { next(err); }
    });

    // Get single stack with sources
    router.get('/:name', async (req, res, next) => {
        try {
            const result = await pool.query(`SELECT * FROM get_stack(${lit(req.params.name)})`);
            if (!result.rows.length) return res.status(404).json({ error: 'Stack not found' });
            res.json(result.rows[0]);
        } catch (err) { next(err); }
    });

    // Create stack
    router.post('/', async (req, res, next) => {
        try {
            const { name, label, fields, amount_field, date_field, balance_offset } = req.body;
            if (!name) return res.status(400).json({ error: 'name is required' });
            const result = await pool.query(
                `SELECT * FROM create_stack(${lit(name)}, ${lit(label || null)}, ${lit(JSON.stringify(fields || []))}, ${lit(amount_field || null)}, ${lit(date_field || null)}, ${lit(balance_offset ?? 0)})`
            );
            res.status(201).json(result.rows[0]);
        } catch (err) {
            if (err.code === '23505') return res.status(409).json({ error: 'Stack already exists' });
            next(err);
        }
    });

    // Update stack
    router.put('/:name', async (req, res, next) => {
        try {
            const { label, fields, amount_field, date_field, balance_offset } = req.body;
            const n = v => v !== undefined ? lit(v) : 'NULL';
            const f = v => v !== undefined ? lit(JSON.stringify(v)) : 'NULL';
            const result = await pool.query(
                `SELECT * FROM update_stack(${lit(req.params.name)}, ${n(label)}, ${f(fields)}, ${n(amount_field)}, ${n(date_field)}, ${n(balance_offset)})`
            );
            if (!result.rows.length) return res.status(404).json({ error: 'Stack not found' });
            res.json(result.rows[0]);
        } catch (err) { next(err); }
    });

    // Delete stack
    router.delete('/:name', async (req, res, next) => {
        try {
            const result = await pool.query(`SELECT * FROM delete_stack(${lit(req.params.name)})`);
            if (!result.rows.length) return res.status(404).json({ error: 'Stack not found' });
            res.json({ success: true, deleted: req.params.name });
        } catch (err) { next(err); }
    });

    // Add or update a source in a stack
    router.put('/:name/sources/:source', async (req, res, next) => {
        try {
            const { field_map, amount_sign, balance_offset, amount_field, date_field } = req.body;
            const n = v => v != null ? lit(v) : 'NULL';
            const result = await pool.query(
                `SELECT * FROM upsert_stack_source(${lit(req.params.name)}, ${lit(req.params.source)}, ${lit(JSON.stringify(field_map || {}))}, ${lit(amount_sign ?? 1)}, ${lit(balance_offset ?? 0)}, ${n(amount_field)}, ${n(date_field)})`
            );
            res.json(result.rows[0]);
        } catch (err) {
            if (err.code === '23503') return res.status(404).json({ error: 'Stack or source not found' });
            next(err);
        }
    });

    // Remove a source from a stack
    router.delete('/:name/sources/:source', async (req, res, next) => {
        try {
            const result = await pool.query(
                `SELECT * FROM remove_stack_source(${lit(req.params.name)}, ${lit(req.params.source)})`
            );
            if (!result.rows.length) return res.status(404).json({ error: 'Source not in stack' });
            res.json({ success: true, removed: req.params.source });
        } catch (err) { next(err); }
    });

    // Get current running balance from the generated view
    router.get('/:name/balance', async (req, res, next) => {
        try {
            const result = await pool.query(`SELECT get_stack_balance(${lit(req.params.name)}) AS result`);
            res.json(result.rows[0].result);
        } catch (err) { next(err); }
    });

    // Preview the SQL that would be generated (dry run — does not create the view)
    router.get('/:name/view-sql', async (req, res, next) => {
        try {
            const result = await pool.query(`SELECT generate_stack_view(${lit(req.params.name)}, true) AS result`);
            res.json(result.rows[0].result);
        } catch (err) { next(err); }
    });

    // Generate / refresh the dfv view
    router.post('/:name/view', async (req, res, next) => {
        try {
            const result = await pool.query(`SELECT generate_stack_view(${lit(req.params.name)}) AS result`);
            const data = result.rows[0].result;
            if (data && data.success) {
                await pool.query(`UPDATE dataflow.stacks SET view_generated_at = NOW() WHERE name = ${lit(req.params.name)}`);
            }
            res.json(data);
        } catch (err) { next(err); }
    });

    // Execute custom SQL for the view (user-edited SQL)
    router.post('/:name/exec-sql', async (req, res, next) => {
        try {
            const { sql } = req.body;
            if (!sql) return res.status(400).json({ success: false, error: 'sql is required' });
            await pool.query(`DROP VIEW IF EXISTS dfv.${req.params.name} CASCADE`);
            await pool.query(sql);
            await pool.query(`UPDATE dataflow.stacks SET view_generated_at = NOW() WHERE name = ${lit(req.params.name)}`);
            // Detect stacks whose views were dropped by CASCADE
            const staleResult = await pool.query(`
                SELECT array_agg(name) AS names FROM dataflow.stacks
                WHERE name != ${lit(req.params.name)}
                  AND view_generated_at IS NOT NULL
                  AND NOT EXISTS (
                      SELECT 1 FROM pg_views WHERE schemaname = 'dfv' AND viewname = name
                  )
            `);
            const cascadeStale = staleResult.rows[0].names || [];
            if (cascadeStale.length) {
                await pool.query(`UPDATE dataflow.stacks SET view_generated_at = NULL WHERE name = ANY($1)`, [cascadeStale]);
            }
            res.json({ success: true, cascade_stale: cascadeStale });
        } catch (err) {
            res.json({ success: false, error: err.message });
        }
    });

    // Calibrate balance offset given a known good balance at a specific date
    router.post('/:name/calibrate', async (req, res, next) => {
        try {
            const { as_of_date, known_balance, source_name } = req.body;
            if (!as_of_date || known_balance === undefined) {
                return res.status(400).json({ error: 'as_of_date and known_balance are required' });
            }
            const result = await pool.query(
                `SELECT calibrate_balance(${lit(req.params.name)}, ${source_name ? lit(source_name) : 'NULL'}, ${lit(as_of_date)}::date, ${lit(known_balance)}::numeric) AS result`
            );
            res.json(result.rows[0].result);
        } catch (err) { next(err); }
    });

    return router;
};