/**
 * Visibility Events Service
 *
 * Shared utility for detecting notable inventory events:
 * - OOS (out of stock) - product disappeared from menu
 * - Back in stock - product returned to menu
 * - Brand dropped - brand no longer at store
 * - Brand added - new brand at store
 * - Price change - significant price change (>5%)
 *
 * Part of Real-Time Inventory Tracking feature.
 */

import { Pool } from 'pg';
import { Platform } from './inventory-snapshots';

export type EventType = 'oos' | 'back_in_stock' | 'brand_dropped' | 'brand_added' | 'price_change';

interface VisibilityEvent {
  dispensary_id: number;
  product_id: string | null;
  product_name: string | null;
  brand_name: string | null;
  event_type: EventType;
  previous_quantity: number | null;
  previous_price: number | null;
  new_price: number | null;
  price_change_pct: number | null;
  platform: Platform;
}

interface ProductInfo {
  id: string;
  name: string | null;
  brand: string | null;
  price: number | null;
  quantity: number | null;
}

/**
 * Extract product info from raw product based on platform.
 */
function extractProductInfo(product: any, platform: Platform): ProductInfo | null {
  let id: string | null = null;
  let name: string | null = null;
  let brand: string | null = null;
  let price: number | null = null;
  let quantity: number | null = null;

  switch (platform) {
    case 'dutchie':
      id = product.id;
      name = product.Name || product.name;
      brand = product.brand?.name || null;
      price = product.recPrices?.[0] || product.Prices?.[0] || null;
      if (product.children && Array.isArray(product.children)) {
        quantity = product.children.reduce(
          (sum: number, child: any) => sum + (child.quantityAvailable || child.quantity || 0),
          0
        );
      }
      break;

    case 'jane':
      id = String(product.product_id);
      name = product.name;
      brand = product.brand || null;
      price = product.bucket_price || product.price_gram || null;
      quantity = product.max_cart_quantity ?? null;
      break;

    case 'treez':
      id = product.id;
      name = product.name || product.menuTitle;
      brand = product.brand || null;
      price = product.customMinPrice ?? null;
      quantity = product.availableUnits ?? null;
      break;
  }

  if (!id) return null;

  return { id, name, brand, price, quantity };
}

/**
 * Detect visibility events by comparing current products to previous state.
 *
 * Call this after fetching products in any platform handler.
 * Compares current products to stored state and creates events for changes.
 *
 * @param pool - Database connection pool
 * @param dispensaryId - The dispensary ID
 * @param products - Array of raw products from the platform
 * @param platform - The platform type
 * @returns Number of events created
 */
export async function detectVisibilityEvents(
  pool: Pool,
  dispensaryId: number,
  products: any[],
  platform: Platform
): Promise<number> {
  if (!products || products.length === 0) {
    return 0;
  }

  // Get previous product state from store_products
  const { rows: previousProducts } = await pool.query(
    `
    SELECT
      provider_product_id as id,
      name,
      brand,
      price_rec as price
    FROM store_products
    WHERE dispensary_id = $1
    `,
    [dispensaryId]
  );

  // Build maps for comparison
  const previousMap = new Map<string, { name: string; brand: string | null; price: number | null }>();
  const previousBrands = new Set<string>();

  for (const p of previousProducts) {
    previousMap.set(p.id, { name: p.name, brand: p.brand, price: p.price });
    if (p.brand) previousBrands.add(p.brand);
  }

  const currentMap = new Map<string, ProductInfo>();
  const currentBrands = new Set<string>();

  for (const product of products) {
    const info = extractProductInfo(product, platform);
    if (info) {
      currentMap.set(info.id, info);
      if (info.brand) currentBrands.add(info.brand);
    }
  }

  const events: VisibilityEvent[] = [];

  // Detect OOS events (products that disappeared)
  Array.from(previousMap.entries()).forEach(([id, prev]) => {
    if (!currentMap.has(id)) {
      events.push({
        dispensary_id: dispensaryId,
        product_id: id,
        product_name: prev.name,
        brand_name: prev.brand,
        event_type: 'oos',
        previous_quantity: null,
        previous_price: prev.price,
        new_price: null,
        price_change_pct: null,
        platform,
      });
    }
  });

  // Detect back_in_stock events (products that appeared)
  Array.from(currentMap.entries()).forEach(([id, curr]) => {
    if (!previousMap.has(id)) {
      events.push({
        dispensary_id: dispensaryId,
        product_id: id,
        product_name: curr.name,
        brand_name: curr.brand,
        event_type: 'back_in_stock',
        previous_quantity: null,
        previous_price: null,
        new_price: curr.price,
        price_change_pct: null,
        platform,
      });
    }
  });

  // Detect price changes (>5% change)
  Array.from(currentMap.entries()).forEach(([id, curr]) => {
    const prev = previousMap.get(id);
    if (prev && prev.price != null && curr.price != null) {
      const priceDiff = curr.price - prev.price;
      const pctChange = (priceDiff / prev.price) * 100;

      if (Math.abs(pctChange) >= 5) {
        events.push({
          dispensary_id: dispensaryId,
          product_id: id,
          product_name: curr.name,
          brand_name: curr.brand,
          event_type: 'price_change',
          previous_quantity: null,
          previous_price: prev.price,
          new_price: curr.price,
          price_change_pct: Math.round(pctChange * 100) / 100,
          platform,
        });
      }
    }
  });

  // Detect brand drops (brands that disappeared from store)
  Array.from(previousBrands).forEach((brand) => {
    if (!currentBrands.has(brand)) {
      events.push({
        dispensary_id: dispensaryId,
        product_id: null,
        product_name: null,
        brand_name: brand,
        event_type: 'brand_dropped',
        previous_quantity: null,
        previous_price: null,
        new_price: null,
        price_change_pct: null,
        platform,
      });
    }
  });

  // Detect brand additions (new brands at store)
  Array.from(currentBrands).forEach((brand) => {
    if (!previousBrands.has(brand)) {
      events.push({
        dispensary_id: dispensaryId,
        product_id: null,
        product_name: null,
        brand_name: brand,
        event_type: 'brand_added',
        previous_quantity: null,
        previous_price: null,
        new_price: null,
        price_change_pct: null,
        platform,
      });
    }
  });

  if (events.length === 0) {
    return 0;
  }

  // Bulk insert events
  const values: any[] = [];
  const placeholders: string[] = [];

  let paramIndex = 1;
  for (const e of events) {
    placeholders.push(
      `($${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++}, $${paramIndex++})`
    );
    values.push(
      e.dispensary_id,
      e.product_id,
      e.product_name,
      e.brand_name,
      e.event_type,
      e.previous_quantity,
      e.previous_price,
      e.new_price,
      e.price_change_pct,
      e.platform
    );
  }

  const query = `
    INSERT INTO product_visibility_events (
      dispensary_id,
      product_id,
      product_name,
      brand_name,
      event_type,
      previous_quantity,
      previous_price,
      new_price,
      price_change_pct,
      platform
    ) VALUES ${placeholders.join(', ')}
  `;

  await pool.query(query, values);

  console.log(`[VisibilityEvents] Created ${events.length} events for dispensary ${dispensaryId}`);

  return events.length;
}

/**
 * Get recent visibility events for a dispensary.
 */
export async function getRecentEvents(
  pool: Pool,
  dispensaryId: number,
  limit = 100
): Promise<any[]> {
  const { rows } = await pool.query(
    `
    SELECT
      id,
      product_id,
      product_name,
      brand_name,
      event_type,
      detected_at,
      previous_price,
      new_price,
      price_change_pct,
      platform,
      notified,
      acknowledged_at
    FROM product_visibility_events
    WHERE dispensary_id = $1
    ORDER BY detected_at DESC
    LIMIT $2
    `,
    [dispensaryId, limit]
  );

  return rows;
}

/**
 * Get unnotified events for external system integration.
 */
export async function getUnnotifiedEvents(
  pool: Pool,
  limit = 100
): Promise<any[]> {
  const { rows } = await pool.query(
    `
    SELECT
      e.id,
      e.dispensary_id,
      d.name as dispensary_name,
      e.product_id,
      e.product_name,
      e.brand_name,
      e.event_type,
      e.detected_at,
      e.previous_price,
      e.new_price,
      e.price_change_pct,
      e.platform
    FROM product_visibility_events e
    JOIN dispensaries d ON d.id = e.dispensary_id
    WHERE e.notified = FALSE
    ORDER BY e.detected_at DESC
    LIMIT $1
    `,
    [limit]
  );

  return rows;
}

/**
 * Mark events as notified.
 */
export async function markEventsNotified(
  pool: Pool,
  eventIds: number[]
): Promise<void> {
  if (eventIds.length === 0) return;

  await pool.query(
    `
    UPDATE product_visibility_events
    SET notified = TRUE
    WHERE id = ANY($1)
    `,
    [eventIds]
  );
}