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

const TOP_BUYERS_LIMIT = 100;
const MAX_CAMPAIGN_ATTEMPTS = 3;
const CAMPAIGN_DELTA_THRESHOLD = 100;

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

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

        const result = await client.query(`
            WITH ready_groups AS (
                SELECT base_product_name
                FROM stock_campaign_queue
                WHERE status IN ('pending', 'failed')
                  AND attempts < $1
                GROUP BY base_product_name
                HAVING SUM(delta_estoque) >= $2
            ),
            ready_items AS (
                SELECT queue.id
                FROM stock_campaign_queue queue
                JOIN ready_groups ON ready_groups.base_product_name = queue.base_product_name
                WHERE queue.status IN ('pending', 'failed')
                  AND queue.attempts < $1
                ORDER BY queue.created_at ASC
                FOR UPDATE OF queue SKIP LOCKED
            )
            UPDATE stock_campaign_queue
            SET status = 'processing',
                attempts = attempts + 1,
                updated_at = CURRENT_TIMESTAMP,
                last_error = NULL
            WHERE id IN (SELECT id FROM ready_items)
            RETURNING *;
        `, [MAX_CAMPAIGN_ATTEMPTS, CAMPAIGN_DELTA_THRESHOLD]);

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

const countPendingBelowThresholdGroups = async () => {
    const result = await pool.query(`
        SELECT COUNT(*)::int as count
        FROM (
            SELECT base_product_name
            FROM stock_campaign_queue
            WHERE status IN ('pending', 'failed')
              AND attempts < $1
            GROUP BY base_product_name
            HAVING SUM(delta_estoque) < $2
        ) below_threshold_groups;
    `, [MAX_CAMPAIGN_ATTEMPTS, CAMPAIGN_DELTA_THRESHOLD]);

    return result.rows[0]?.count || 0;
};

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

    await pool.query(`
        UPDATE stock_campaign_queue
        SET status = $1::varchar,
            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 formatProductList = (productNames) => {
    if (productNames.length <= 2) {
        return productNames.join(' e ');
    }

    return `${productNames.slice(0, -1).join(', ')} e ${productNames[productNames.length - 1]}`;
};

const mapCampaignProducts = (groups) => {
    return Object.entries(groups)
        .sort(([, aItems], [, bItems]) => {
            return new Date(aItems[0].created_at).getTime() - new Date(bItems[0].created_at).getTime();
        })
        .map(([baseProductName, items]) => {
            const sortedItems = [...items].sort((a, b) => String(a.nome).localeCompare(String(b.nome), 'pt-BR'));

            return {
                baseProduct: baseProductName,
                total_delta: sortedItems.reduce((sum, item) => sum + Number(item.delta_estoque || 0), 0),
                sizes: sortedItems.map(item => ({
                    id: item.produto_id,
                    nome: item.nome,
                    delta: item.delta_estoque,
                    saldo: item.saldo
                })),
                itemIds: sortedItems.map(item => item.id)
            };
        });
};

const sendWhatsappCampaign = async (products, customers) => {
    const productNames = products.map(product => product.baseProduct);
    const productsText = formatProductList(productNames);
    const allSizes = products.flatMap(product => product.sizes);
    const totalDelta = products.reduce((sum, product) => sum + product.total_delta, 0);

    const response = await fetch(N8N_WHATSAPP_TRIGGER_URL, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
            baseProduct: productsText,
            productsText,
            total_delta: totalDelta,
            sizes: allSizes,
            products: products.map(({ itemIds, ...product }) => product),
            customers
        })
    });

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

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

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

    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;
    }, {});
    const products = mapCampaignProducts(groups);
    const ids = products.flatMap(product => product.itemIds);
    const customers = await getTopBuyersAllTime();

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

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

    return summary;
};

module.exports = {
    enqueueStockCampaignItem,
    processPendingStockCampaigns
};