import sqlite3
from datetime import datetime
import os

DB_PATH = "grocery_receipts.db"

def init_db():
    """Initialize the database with required tables."""
    conn = sqlite3.connect(DB_PATH)
    cursor = conn.cursor()
    
    # Create stores table
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS stores (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL UNIQUE
        )
    ''')
    
    # Create products table
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS products (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL UNIQUE
        )
    ''')
    
    # Create receipts table
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS receipts (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            store_id INTEGER NOT NULL,
            date DATE NOT NULL,
            total REAL NOT NULL,
            FOREIGN KEY (store_id) REFERENCES stores(id)
        )
    ''')
    
    # Create receipt_items table (linking products to receipts with prices)
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS receipt_items (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            receipt_id INTEGER NOT NULL,
            product_id INTEGER NOT NULL,
            quantity REAL NOT NULL,
            price REAL NOT NULL,
            FOREIGN KEY (receipt_id) REFERENCES receipts(id),
            FOREIGN KEY (product_id) REFERENCES products(id)
        )
    ''')
    
    conn.commit()
    conn.close()

def add_receipt(store_name, date, items):
    """
    Add a receipt to the database.
    
    Args:
        store_name: Name of the store
        date: Date of the receipt (YYYY-MM-DD format)
        items: List of tuples (product_name, quantity, price_per_unit)
    """
    conn = sqlite3.connect(DB_PATH)
    cursor = conn.cursor()
    
    # Get or create store
    cursor.execute("SELECT id FROM stores WHERE name = ?", (store_name,))
    store = cursor.fetchone()
    if not store:
        cursor.execute("INSERT INTO stores (name) VALUES (?)", (store_name,))
        conn.commit()
        cursor.execute("SELECT id FROM stores WHERE name = ?", (store_name,))
        store = cursor.fetchone()
    
    store_id = store[0]
    
    # Insert receipt
    cursor.execute("INSERT INTO receipts (store_id, date, total) VALUES (?, ?, ?)",
                   (store_id, date, sum(item[1] * item[2] for item in items)))
    receipt_id = cursor.lastrowid
    
    # Insert items
    for product_name, quantity, price in items:
        # Get or create product
        cursor.execute("SELECT id FROM products WHERE name = ?", (product_name,))
        product = cursor.fetchone()
        if not product:
            cursor.execute("INSERT INTO products (name) VALUES (?)", (product_name,))
            conn.commit()
            cursor.execute("SELECT id FROM products WHERE name = ?", (product_name,))
            product = cursor.fetchone()
        
        product_id = product[0]
        cursor.execute("INSERT INTO receipt_items (receipt_id, product_id, quantity, price) VALUES (?, ?, ?, ?)",
                       (receipt_id, product_id, quantity, price))
    
    conn.commit()
    conn.close()

def get_product_prices(product_name):
    """
    Get all prices for a specific product across all receipts.
    
    Args:
        product_name: Name of the product
        
    Returns:
        List of tuples (date, store_name, quantity, price_per_unit)
    """
    conn = sqlite3.connect(DB_PATH)
    cursor = conn.cursor()
    
    cursor.execute('''
        SELECT r.date, s.name, ri.quantity, ri.price
        FROM receipt_items ri
        JOIN receipts r ON ri.receipt_id = r.id
        JOIN stores s ON r.store_id = s.id
        JOIN products p ON ri.product_id = p.id
        WHERE p.name = ?
        ORDER BY r.date
    ''', (product_name,))
    
    results = cursor.fetchall()
    conn.close()
    
    return results

def list_receipts():
    """
    List all receipts in the database.
    
    Returns:
        List of tuples (receipt_id, store_name, date, total)
    """
    conn = sqlite3.connect(DB_PATH)
    cursor = conn.cursor()
    
    cursor.execute('''
        SELECT r.id, s.name, r.date, r.total
        FROM receipts r
        JOIN stores s ON r.store_id = s.id
        ORDER BY r.date DESC
    ''')
    
    results = cursor.fetchall()
    conn.close()
    
    return results

# Initialize the database when the module is imported
init_db()

if __name__ == "__main__":
    # Example usage
    print("Grocery Receipt Tracker - Demo")
    print("=" * 30)
    
    # Add a sample receipt
    items = [
        ("Milk", 2, 1.50),
        ("Bread", 1, 2.00),
        ("Apples", 3, 0.80)
    ]
    add_receipt("SuperMarket", "2023-10-15", items)
    print("Added sample receipt to database.")
    
    # Add another receipt for comparison
    items2 = [
        ("Milk", 1, 1.30),
        ("Bread", 1, 1.80)
    ]
    add_receipt("Corner Store", "2023-10-20", items2)
    print("Added another receipt to database.")
    
    # Show all receipts
    print("\nAll Receipts:")
    for receipt in list_receipts():
        print(f"  ID: {receipt[0]}, Store: {receipt[1]}, Date: {receipt[2]}, Total: ${receipt[3]:.2f}")
    
    # Show prices for a specific product
    print("\nMilk Prices Over Time:")
    for price_info in get_product_prices("Milk"):
        print(f"  Date: {price_info[0]}, Store: {price_info[1]}, Qty: {price_info[2]}, Price: ${price_info[3]:.2f}")