const express = require('express');
const { generateSQL } = require('../lib/sql_generator');
const { sessionUser } = require('../lib/auth');

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

    // list all registered sources
    router.get('/sources', async (req, res) => {
        try {
            const result = await pool.query(
                `SELECT * FROM pf.source ORDER BY schema, tname`
            );
            res.json(result.rows);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // register a source table
    // auto-populates col_meta from information_schema with role='ignore'
    router.post('/sources', async (req, res) => {
        const { schema, tname, label } = req.body;
        const created_by = sessionUser(req);
        if (!schema || !tname) {
            return res.status(400).json({ error: 'schema and tname are required' });
        }
        if (!/^\w+$/.test(schema) || !/^\w+$/.test(tname)) {
            return res.status(400).json({ error: 'Invalid schema or table name' });
        }
        const client = await pool.connect();
        try {
            await client.query('BEGIN');

            const src = await client.query(
                `INSERT INTO pf.source (schema, tname, label, created_by)
                 VALUES ($1, $2, $3, $4)
                 RETURNING *`,
                [schema, tname, label || null, created_by || null]
            );
            const source = src.rows[0];

            // seed col_meta from information_schema
            await client.query(`
                INSERT INTO pf.col_meta (source_id, cname, role, opos)
                SELECT $1, column_name, 'dimension', ordinal_position
                FROM information_schema.columns
                WHERE table_schema = $2 AND table_name = $3
                ORDER BY ordinal_position
                ON CONFLICT (source_id, cname) DO NOTHING
            `, [source.id, schema, tname]);

            await client.query('COMMIT');
            res.status(201).json(source);
        } catch (err) {
            await client.query('ROLLBACK');
            console.error(err);
            if (err.code === '23505') {
                return res.status(409).json({ error: 'Source already registered' });
            }
            res.status(500).json({ error: err.message });
        } finally {
            client.release();
        }
    });

    // get col_meta for a source
    router.get('/sources/:id/cols', async (req, res) => {
        try {
            const result = await pool.query(
                `SELECT * FROM pf.col_meta WHERE source_id = $1 ORDER BY opos`,
                [req.params.id]
            );
            res.json(result.rows);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // save col_meta — accepts full array, upserts each row
    router.put('/sources/:id/cols', async (req, res) => {
        const sourceId = parseInt(req.params.id);
        const cols = req.body;
        if (!Array.isArray(cols)) {
            return res.status(400).json({ error: 'body must be an array' });
        }
        const client = await pool.connect();
        try {
            await client.query('BEGIN');
            for (const col of cols) {
                await client.query(`
                    INSERT INTO pf.col_meta (source_id, cname, label, role, is_key, dim_group, dim_period_col, in_grain, opos)
                    VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
                    ON CONFLICT (source_id, cname) DO UPDATE SET
                        label          = EXCLUDED.label,
                        role           = EXCLUDED.role,
                        is_key         = EXCLUDED.is_key,
                        dim_group      = EXCLUDED.dim_group,
                        dim_period_col = EXCLUDED.dim_period_col,
                        in_grain       = EXCLUDED.in_grain,
                        opos           = EXCLUDED.opos
                `, [
                    sourceId,
                    col.cname,
                    col.label          || null,
                    col.role           || 'ignore',
                    col.is_key         || false,
                    col.dim_group      || null,
                    col.dim_period_col || null,
                    col.in_grain       || false,
                    col.opos           || null
                ]);
            }
            await client.query('COMMIT');
            const result = await pool.query(
                `SELECT * FROM pf.col_meta WHERE source_id = $1 ORDER BY opos`,
                [sourceId]
            );
            res.json(result.rows);
        } catch (err) {
            await client.query('ROLLBACK');
            console.error(err);
            res.status(500).json({ error: err.message });
        } finally {
            client.release();
        }
    });

    // generate SQL for all operations from current col_meta and store in pf.sql
    router.post('/sources/:id/generate-sql', async (req, res) => {
        const sourceId = parseInt(req.params.id);
        try {
            const srcResult = await pool.query(
                `SELECT * FROM pf.source WHERE id = $1`, [sourceId]
            );
            if (srcResult.rows.length === 0) {
                return res.status(404).json({ error: 'Source not found' });
            }

            const colResult = await pool.query(
                `SELECT * FROM pf.col_meta WHERE source_id = $1 ORDER BY opos`,
                [sourceId]
            );

            // validate required roles
            const colMeta = colResult.rows;
            const roles   = new Set(colMeta.map(c => c.role));
            const missing = ['value', 'date'].filter(r => !roles.has(r));
            if (missing.length > 0) {
                return res.status(400).json({
                    error: `col_meta is missing required roles: ${missing.join(', ')}`
                });
            }
            if (!colMeta.some(c => c.role === 'dimension')) {
                return res.status(400).json({ error: 'col_meta has no dimension columns' });
            }

            const sqls   = generateSQL(srcResult.rows[0], colMeta);
            const client = await pool.connect();
            try {
                await client.query('BEGIN');
                for (const [operation, sql] of Object.entries(sqls)) {
                    await client.query(`
                        INSERT INTO pf.sql (source_id, operation, sql, generated_at)
                        VALUES ($1, $2, $3, now())
                        ON CONFLICT (source_id, operation) DO UPDATE SET
                            sql          = EXCLUDED.sql,
                            generated_at = EXCLUDED.generated_at
                    `, [sourceId, operation, sql]);
                }
                // drop operations this generation no longer produces — e.g. get_agg
                // after the grain has been cleared, which would otherwise leave a
                // stale template the load path would still pick up
                await client.query(
                    `DELETE FROM pf.sql WHERE source_id = $1 AND operation <> ALL($2::text[])`,
                    [sourceId, Object.keys(sqls)]
                );
                await client.query('COMMIT');
            } catch (err) {
                await client.query('ROLLBACK');
                throw err;
            } finally {
                client.release();
            }

            res.json({ message: 'SQL generated', operations: Object.keys(sqls) });
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // view generated SQL for a source (for inspection / debug)
    router.get('/sources/:id/sql', async (req, res) => {
        try {
            const result = await pool.query(
                `SELECT operation, sql, generated_at
                 FROM pf.sql WHERE source_id = $1 ORDER BY operation`,
                [req.params.id]
            );
            res.json(result.rows);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // get distinct values for a key column (used to populate operation panel dropdowns)
    router.get('/sources/:id/values/:col', async (req, res) => {
        const col = req.params.col;
        try {
            const srcResult = await pool.query(
                `SELECT schema, tname FROM pf.source WHERE id = $1`, [req.params.id]
            );
            if (srcResult.rows.length === 0) return res.status(404).json({ error: 'Source not found' });

            // validate col is a key dimension on this source
            const metaResult = await pool.query(
                `SELECT 1 FROM pf.col_meta WHERE source_id = $1 AND cname = $2 AND is_key = true`,
                [req.params.id, col]
            );
            if (metaResult.rows.length === 0) {
                return res.status(400).json({ error: `"${col}" is not a key column` });
            }

            // ?q= narrows, ?limit= caps. A key column can be very wide -- part on
            // osm_skinny has 11,290 distinct values -- so returning the lot to fill a
            // completion list is both a slow query and a large response for a control
            // that can only usefully show a handful.
            const { schema, tname } = srcResult.rows[0];
            const q     = (req.query.q || '').trim();
            const limit = Math.min(parseInt(req.query.limit) || 5000, 5000);

            const params = [];
            let filter = `WHERE "${col}" IS NOT NULL`;
            if (q) {
                params.push(`%${q}%`);
                filter += ` AND "${col}"::text ILIKE $${params.length}`;
            }
            params.push(limit);

            const result = await pool.query(
                `SELECT DISTINCT "${col}"::text AS val FROM ${schema}.${tname}
                 ${filter} ORDER BY 1 LIMIT $${params.length}`,
                params
            );
            res.json(result.rows.map(r => r.val));
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // Resolve a dim_group to its key column and siblings, or explain why it cannot be.
    async function resolveGroup(sourceId, group) {
        const { rows: meta } = await pool.query(
            `SELECT * FROM pf.col_meta WHERE source_id = $1 ORDER BY opos`, [sourceId]);
        const members = meta.filter(c => c.dim_group === group);
        if (!members.length) {
            const err = new Error(`No columns are grouped as "${group}" on this source`);
            err.status = 404; throw err;
        }
        const keyCol = members.find(c => c.is_key);
        if (!keyCol) {
            const err = new Error(
                `Group "${group}" has no is_key column, so its members have nothing to be keyed on`);
            err.status = 400; throw err;
        }
        return {
            keyCol,
            siblings:  members.filter(c => c.cname !== keyCol.cname),
            // recency column: the source's primary date, the same one the generator
            // treats as the date for loads
            dateCol: meta.find(c => c.role === 'date')?.cname || null,
        };
    }

    // The member list for a group, as one array. Small enough to send whole --
    // 11,290 parts on osm_skinny -- so the client holds it and filters locally
    // instead of querying per keystroke.
    router.get('/sources/:id/dim/:group', async (req, res) => {
        try {
            const sourceId = parseInt(req.params.id);
            const { keyCol, siblings } = await resolveGroup(sourceId, req.params.group);
            const includeInactive = req.query.all === '1';

            const { rows } = await pool.query(`
                SELECT key_value, attrs, is_active, source_seen
                FROM pf.dim_member
                WHERE source_id = $1 AND dim_group = $2
                ${includeInactive ? '' : 'AND is_active'}
                ORDER BY key_value
            `, [sourceId, req.params.group]);

            res.json({
                group:    req.params.group,
                key_col:  keyCol.cname,
                siblings: siblings.map(c => c.cname),
                members:  rows,
            });
        } catch (err) {
            console.error(err);
            res.status(err.status || 500).json({ error: err.message });
        }
    });

    // Rebuild a group's members from the source. A merge, not a replace: curation
    // (a member deactivated by hand, or added before it ever sold) has to survive a
    // refresh, so absent members are marked source_seen = false rather than deleted.
    //
    // Slow by nature -- it reads the whole source, which for a view over a
    // transaction table is millions of rows -- so it is a deliberate action rather
    // than something that happens on a page load.
    router.post('/sources/:id/dim/:group/refresh', async (req, res) => {
        const sourceId = parseInt(req.params.id);
        const group    = req.params.group;
        try {
            const srcResult = await pool.query(
                `SELECT schema, tname FROM pf.source WHERE id = $1`, [sourceId]);
            if (!srcResult.rows.length) return res.status(404).json({ error: 'Source not found' });
            const { schema, tname } = srcResult.rows[0];

            const { keyCol, siblings, dateCol } = await resolveGroup(sourceId, group);
            if (!siblings.length) {
                return res.status(400).json({ error: `Group "${group}" has no sibling columns to store` });
            }

            const q      = (n) => `"${n}"`;
            const attrs  = siblings.map(c => `'${c.cname}', s.${q(c.cname)}::text`).join(', ');
            // A key can carry more than one attribute set across history -- 11,290
            // parts against 13,662 combinations on osm_skinny. Take the most recent
            // by the source's date column, which is the live definition.
            const recency = dateCol ? `s.${q(dateCol)} DESC NULLS LAST` : `1`;

            const started = Date.now();
            // An explicit stamp rather than now(): inside a transaction now() is the
            // transaction's start time, so "refreshed in this run" and "refreshed in
            // a run that began at the same instant" would be indistinguishable.
            const runAt   = new Date();
            const client  = await pool.connect();
            try {
                await client.query('BEGIN');
                const { rows: [{ n }] } = await client.query(`
                    WITH ranked AS (
                        SELECT s.${q(keyCol.cname)}::text AS key_value,
                               jsonb_build_object(${attrs}) AS attrs,
                               row_number() OVER (
                                   PARTITION BY s.${q(keyCol.cname)} ORDER BY ${recency}
                               ) AS rn
                        FROM ${q(schema)}.${q(tname)} s
                        WHERE s.${q(keyCol.cname)} IS NOT NULL
                    )
                    ,upserted AS (
                        INSERT INTO pf.dim_member
                            (source_id, dim_group, key_value, attrs, refreshed_at, source_seen)
                        SELECT $1, $2, key_value, attrs, $3, true
                        FROM ranked WHERE rn = 1
                        ON CONFLICT (source_id, dim_group, key_value) DO UPDATE SET
                            attrs        = EXCLUDED.attrs,
                            source_seen  = true,
                            refreshed_at = $3,
                            updated_at   = now()
                        RETURNING 1
                    )
                    SELECT count(*)::int AS n FROM upserted
                `, [sourceId, group, runAt]);

                // anything this run did not touch is no longer in the source
                const { rowCount: dropped } = await client.query(`
                    UPDATE pf.dim_member
                    SET source_seen = false, updated_at = now()
                    WHERE source_id = $1 AND dim_group = $2 AND source_seen
                      AND refreshed_at IS DISTINCT FROM $3
                `, [sourceId, group, runAt]);

                await client.query('COMMIT');
                res.json({ group, members: n, no_longer_in_source: dropped, ms: Date.now() - started });
            } catch (err) {
                await client.query('ROLLBACK');
                throw err;
            } finally {
                client.release();
            }
        } catch (err) {
            console.error(err);
            res.status(err.status || 500).json({ error: err.message });
        }
    });

    // given a key column value, look up sibling dim_group column values from source
    // returns { sibling_col: value, ... } if exactly one match, null if none or ambiguous
    router.get('/sources/:id/lookup', async (req, res) => {
        const { col, value } = req.query;
        if (!col || value == null || value === '') return res.json(null);
        try {
            const [srcResult, metaResult] = await Promise.all([
                pool.query(`SELECT schema, tname FROM pf.source WHERE id = $1`, [req.params.id]),
                pool.query(`SELECT * FROM pf.col_meta WHERE source_id = $1 ORDER BY opos`, [req.params.id])
            ]);
            if (srcResult.rows.length === 0) return res.status(404).json({ error: 'Source not found' });

            const keyCol = metaResult.rows.find(c => c.cname === col && c.is_key && c.dim_group);
            if (!keyCol) return res.json(null);

            const siblings = metaResult.rows.filter(c =>
                c.dim_group === keyCol.dim_group && c.cname !== col
            );
            if (!siblings.length) return res.json(null);

            const { schema, tname } = srcResult.rows[0];
            const sibCols = siblings.map(c => `"${c.cname}"`).join(', ');
            const result = await pool.query(
                `SELECT DISTINCT ${sibCols} FROM "${schema}"."${tname}" WHERE "${col}" = $1 LIMIT 2`,
                [value]
            );

            if (result.rows.length !== 1) return res.json(null);
            res.json(result.rows[0]);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // set or clear the default Perspective layout for a source.
    // Body: a Perspective view config (group_by, split_by, columns, plugin_config, …).
    // Pass null or {} to clear.
    router.put('/sources/:id/default-layout', async (req, res) => {
        try {
            const layout = req.body && Object.keys(req.body).length > 0 ? req.body : null;
            const result = await pool.query(
                `UPDATE pf.source SET default_layout = $1 WHERE id = $2 RETURNING *`,
                [layout, req.params.id]
            );
            if (result.rows.length === 0) return res.status(404).json({ error: 'Source not found' });
            res.json(result.rows[0]);
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    // deregister a source — does not drop existing forecast tables
    router.get('/dim-period/cols', async (req, res) => {
        try {
            const result = await pool.query(`
                SELECT column_name
                FROM information_schema.columns
                WHERE table_schema = 'pf' AND table_name = 'dim_period'
                  AND column_name NOT IN ('sdat', 'edat', 'drange', 'ndays')
                ORDER BY ordinal_position
            `);
            res.json(result.rows.map(r => r.column_name));
        } catch (err) {
            console.error(err);
            res.status(500).json({ error: err.message });
        }
    });

    router.delete('/sources/:id', async (req, res) => {
        try {
            const result = await pool.query(
                `DELETE FROM pf.source WHERE id = $1 RETURNING *`,
                [req.params.id]
            );
            if (result.rows.length === 0) {
                return res.status(404).json({ error: 'Source not found' });
            }
            res.json({ message: 'Source deregistered', source: result.rows[0] });
        } catch (err) {
            console.error(err);
            if (err.code === '23001' || err.code === '23503') {
                return res.status(409).json({ error: 'Source has existing versions — delete them first.' });
            }
            res.status(500).json({ error: err.message });
        }
    });

    return router;
};