-- Migration: Add Reviews System
-- Created: 2026-01-03

-- Create reviews table
CREATE TABLE IF NOT EXISTS reviews (
    review_id SERIAL PRIMARY KEY,
    product_id INTEGER NOT NULL REFERENCES products(product_id) ON DELETE CASCADE,
    user_id INTEGER NOT NULL REFERENCES users(user_id) ON DELETE CASCADE,
    rating INTEGER NOT NULL CHECK (rating >= 1 AND rating <= 5),
    comment TEXT,
    is_approved BOOLEAN DEFAULT TRUE,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    UNIQUE(product_id, user_id) -- One review per user per product
);

-- Add indexes for better query performance
CREATE INDEX IF NOT EXISTS idx_reviews_product_id ON reviews(product_id);
CREATE INDEX IF NOT EXISTS idx_reviews_user_id ON reviews(user_id);
CREATE INDEX IF NOT EXISTS idx_reviews_rating ON reviews(rating);
CREATE INDEX IF NOT EXISTS idx_reviews_created_at ON reviews(created_at);

-- Add rating and review_count columns to products table if they don't exist
DO $$ 
BEGIN
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name='products' AND column_name='rating') THEN
        ALTER TABLE products ADD COLUMN rating DECIMAL(3,2) DEFAULT 0.00;
    END IF;
    
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name='products' AND column_name='review_count') THEN
        ALTER TABLE products ADD COLUMN review_count INTEGER DEFAULT 0;
    END IF;
END $$;

-- Create function to automatically update updated_at timestamp
CREATE OR REPLACE FUNCTION update_reviews_updated_at()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = CURRENT_TIMESTAMP;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Create trigger for reviews updated_at
DROP TRIGGER IF EXISTS trigger_reviews_updated_at ON reviews;
CREATE TRIGGER trigger_reviews_updated_at
    BEFORE UPDATE ON reviews
    FOR EACH ROW
    EXECUTE FUNCTION update_reviews_updated_at();

-- Function to update product rating and review count
CREATE OR REPLACE FUNCTION update_product_rating(p_product_id INTEGER)
RETURNS VOID AS $$
DECLARE
    avg_rating DECIMAL(3,2);
    total_reviews INTEGER;
BEGIN
    SELECT COALESCE(AVG(rating), 0.00), COUNT(*)
    INTO avg_rating, total_reviews
    FROM reviews
    WHERE product_id = p_product_id AND is_approved = TRUE;
    
    UPDATE products
    SET rating = avg_rating,
        review_count = total_reviews,
        updated_at = CURRENT_TIMESTAMP
    WHERE product_id = p_product_id;
END;
$$ LANGUAGE plpgsql;

-- Create trigger to auto-update product rating after review changes
CREATE OR REPLACE FUNCTION trigger_update_product_rating()
RETURNS TRIGGER AS $$
BEGIN
    IF TG_OP = 'DELETE' THEN
        PERFORM update_product_rating(OLD.product_id);
        RETURN OLD;
    ELSE
        PERFORM update_product_rating(NEW.product_id);
        RETURN NEW;
    END IF;
END;
$$ LANGUAGE plpgsql;

DROP TRIGGER IF EXISTS trigger_review_insert_update_product_rating ON reviews;
CREATE TRIGGER trigger_review_insert_update_product_rating
    AFTER INSERT OR UPDATE ON reviews
    FOR EACH ROW
    EXECUTE FUNCTION trigger_update_product_rating();

DROP TRIGGER IF EXISTS trigger_review_delete_update_product_rating ON reviews;
CREATE TRIGGER trigger_review_delete_update_product_rating
    AFTER DELETE ON reviews
    FOR EACH ROW
    EXECUTE FUNCTION trigger_update_product_rating();

-- Grant permissions (adjust as needed)
-- GRANT ALL PRIVILEGES ON TABLE reviews TO your_db_user;
-- GRANT USAGE, SELECT ON SEQUENCE reviews_review_id_seq TO your_db_user;