const { pool } = require('../db');
const { N8N_WHATSAPP_TRIGGER_URL } = require('../config');

const TOP_BUYERS_LIMIT = 100;
const MAX_CAMPAIGN_ATTEMPTS = 3;

const enqueueStockCampaignItem = async (client, item) => {
    const query = `
        INSERT INTO stock_campaign_queue (
            base_product_name, produto_id, nome, saldo, delta_estoque
        ) VALUES ($1, $2, $3, $4, $5)
    `;

    await client.query(query, [
        item.baseProductName,
        item.produtoId,
        item.nome,
        item.saldo,
        item.deltaEstoque
    ]);
};

const getTopBuyersAllTime = async () => {
    const result = await pool.query(`
        SELECT
            MAX(cliente_nome) as nome,
            cliente_fone as fone,
            SUM(quantidade * valor_unitario) as total_gasto,
            SUM(quantidade) as total_comprado
        FROM orders
        WHERE cliente_fone IS NOT NULL
          AND cliente_fone != ''
        GROUP BY cliente_fone
        ORDER BY total_gasto DESC
        LIMIT $1;
    `, [TOP_BUYERS_LIMIT]);

    return result.rows;
};

const claimPendingCampaignItems = async () => {
    const client = await pool.connect();

    try {
        await client.query('BEGIN');

        const result = await client.query(`
            UPDATE stock_campaign_queue
            SET status = 'processing',
                attempts = attempts + 1,
                updated_at = CURRENT_TIMESTAMP,
                last_error = NULL
            WHERE id IN (
                SELECT id
                FROM stock_campaign_queue
                WHERE status IN ('pending', 'failed')
                  AND attempts < $1
                ORDER BY created_at ASC
                FOR UPDATE SKIP LOCKED
            )
            RETURNING *;
        `, [MAX_CAMPAIGN_ATTEMPTS]);

        await client.query('COMMIT');
        return result.rows;
    } catch (error) {
        await client.query('ROLLBACK');
        throw error;
    } finally {
        client.release();
    }
};

const updateCampaignItemsStatus = async (ids, status, errorMessage = null) => {
    if (!ids.length) return;

    await pool.query(`
        UPDATE stock_campaign_queue
        SET status = $1,
            last_error = $2,
            updated_at = CURRENT_TIMESTAMP,
            sent_at = CASE WHEN $1 = 'sent' THEN CURRENT_TIMESTAMP ELSE sent_at END
        WHERE id = ANY($3::int[]);
    `, [status, errorMessage, ids]);
};

const sendWhatsappCampaign = async (baseProductName, items, customers) => {
    const totalDelta = items.reduce((sum, item) => sum + Number(item.delta_estoque || 0), 0);

    const response = await fetch(N8N_WHATSAPP_TRIGGER_URL, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
            baseProduct: baseProductName,
            total_delta: totalDelta,
            sizes: items.map(item => ({
                id: item.produto_id,
                nome: item.nome,
                delta: item.delta_estoque,
                saldo: item.saldo
            })),
            customers
        })
    });

    if (!response.ok) {
        throw new Error(`WhatsApp webhook returned status ${response.status}`);
    }
};

const processPendingStockCampaigns = async () => {
    const rows = await claimPendingCampaignItems();
    const summary = {
        claimed: rows.length,
        sentGroups: 0,
        skippedGroups: 0,
        failedGroups: 0
    };

    if (!rows.length) {
        return summary;
    }

    const customers = await getTopBuyersAllTime();
    const groups = rows.reduce((acc, row) => {
        if (!acc[row.base_product_name]) acc[row.base_product_name] = [];
        acc[row.base_product_name].push(row);
        return acc;
    }, {});

    for (const [baseProductName, items] of Object.entries(groups)) {
        const ids = items.map(item => item.id);

        if (!customers.length) {
            await updateCampaignItemsStatus(ids, 'skipped', 'No customers with valid phone numbers found.');
            summary.skippedGroups += 1;
            continue;
        }

        try {
            await sendWhatsappCampaign(baseProductName, items, customers);
            await updateCampaignItemsStatus(ids, 'sent');
            summary.sentGroups += 1;
            console.log(`[Campaign Queue] Sent ${baseProductName} campaign to ${customers.length} all-time top buyers.`);
        } catch (error) {
            await updateCampaignItemsStatus(ids, 'failed', error.message);
            summary.failedGroups += 1;
            console.error(`[Campaign Queue] Failed to send ${baseProductName} campaign:`, error);
        }
    }

    return summary;
};

module.exports = {
    enqueueStockCampaignItem,
    processPendingStockCampaigns
};