/*
================================================================================
ORACLE 19C - E-COMMERCE ORDER MANAGEMENT SYSTEM
Complex Schema with Multiple Dependencies
================================================================================
This schema demonstrates:
- Multiple base tables with PK/FK relationships
- Sequences for auto-increment
- Indexes (unique, composite, functional)
- Views (simple and complex with aggregations)
- Stored procedures with business logic
- Packages (organization and reusability)
- Triggers (automatic actions and data validation)
- Table relationships and cascading constraints
================================================================================
*/

-- ============================================================================
-- SEQUENCES
-- ============================================================================

CREATE SEQUENCE seq_customers
    START WITH 1000
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_products
    START WITH 5000
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_orders
    START WITH 100000
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_order_items
    START WITH 1000000
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_employees
    START WITH 2000
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_departments
    START WITH 10
    INCREMENT BY 1
    NOCYCLE;

CREATE SEQUENCE seq_inventory
    START WITH 50000
    INCREMENT BY 1
    NOCYCLE;

-- ============================================================================
-- BASE TABLES - DIMENSION TABLES
-- ============================================================================

-- Departments Table (Parent of Employees)
CREATE TABLE departments (
    department_id      NUMBER PRIMARY KEY,
    department_name    VARCHAR2(100) NOT NULL UNIQUE,
    budget_allocation  NUMBER(12,2),
    manager_id         NUMBER,
    created_date       DATE DEFAULT SYSDATE,
    CONSTRAINT chk_budget_positive CHECK (budget_allocation >= 0)
);

COMMENT ON TABLE departments IS 'Organizational departments that manage business units';
COMMENT ON COLUMN departments.budget_allocation IS 'Annual budget allocation in USD';

-- Employees Table (Parent of Orders via sales_employee_id)
CREATE TABLE employees (
    employee_id        NUMBER PRIMARY KEY,
    first_name         VARCHAR2(50) NOT NULL,
    last_name          VARCHAR2(50) NOT NULL,
    email              VARCHAR2(100) UNIQUE,
    phone_number       VARCHAR2(20),
    hire_date          DATE NOT NULL,
    job_title          VARCHAR2(50),
    salary             NUMBER(10,2),
    department_id      NUMBER NOT NULL,
    manager_id         NUMBER,
    created_date       DATE DEFAULT SYSDATE,
    CONSTRAINT fk_emp_dept FOREIGN KEY (department_id) REFERENCES departments(department_id),
    CONSTRAINT fk_emp_mgr FOREIGN KEY (manager_id) REFERENCES employees(employee_id),
    CONSTRAINT chk_salary_positive CHECK (salary > 0)
);

COMMENT ON TABLE employees IS 'Company employees with hierarchical reporting structure';
COMMENT ON COLUMN employees.manager_id IS 'Self-referencing: supervisor of this employee';

-- Product Categories Table (Parent of Products)
CREATE TABLE product_categories (
    category_id        NUMBER PRIMARY KEY,
    category_name      VARCHAR2(100) NOT NULL UNIQUE,
    description        VARCHAR2(500),
    active_flag        CHAR(1) DEFAULT 'Y',
    created_date       DATE DEFAULT SYSDATE
);

COMMENT ON TABLE product_categories IS 'Product classification hierarchy';

-- Products Table (Parent of Order_Items, Inventory)
CREATE TABLE products (
    product_id         NUMBER PRIMARY KEY,
    product_name       VARCHAR2(150) NOT NULL,
    description        VARCHAR2(500),
    category_id        NUMBER NOT NULL,
    unit_price         NUMBER(10,2) NOT NULL,
    cost_price         NUMBER(10,2),
    reorder_level      NUMBER(5) DEFAULT 10,
    discontinued_flag  CHAR(1) DEFAULT 'N',
    created_date       DATE DEFAULT SYSDATE,
    updated_date       DATE,
    CONSTRAINT fk_prod_cat FOREIGN KEY (category_id) REFERENCES product_categories(category_id),
    CONSTRAINT chk_unit_price CHECK (unit_price > 0),
    CONSTRAINT chk_cost_price CHECK (cost_price IS NULL OR cost_price > 0)
);

COMMENT ON TABLE products IS 'Saleable products in catalog';
COMMENT ON COLUMN products.reorder_level IS 'Minimum stock level before auto-reorder';

-- Customers Table (Parent of Orders, Reviews)
CREATE TABLE customers (
    customer_id        NUMBER PRIMARY KEY,
    first_name         VARCHAR2(50) NOT NULL,
    last_name          VARCHAR2(50) NOT NULL,
    email              VARCHAR2(100) UNIQUE NOT NULL,
    phone_number       VARCHAR2(20),
    billing_address    VARCHAR2(200),
    shipping_address   VARCHAR2(200),
    customer_type      VARCHAR2(20) DEFAULT 'RETAIL',
    credit_limit       NUMBER(10,2),
    account_status     VARCHAR2(20) DEFAULT 'ACTIVE',
    created_date       DATE DEFAULT SYSDATE,
    last_purchase_date DATE,
    CONSTRAINT chk_cust_type CHECK (customer_type IN ('RETAIL', 'WHOLESALE', 'CORPORATE')),
    CONSTRAINT chk_cust_status CHECK (account_status IN ('ACTIVE', 'INACTIVE', 'SUSPENDED', 'ARCHIVED'))
);

COMMENT ON TABLE customers IS 'Customer master data with credit and account information';
COMMENT ON COLUMN customers.credit_limit IS 'Maximum credit extended to customer in USD';

-- ============================================================================
-- TRANSACTIONAL TABLES
-- ============================================================================

-- Orders Table (Parent of Order_Items, child of Customers and Employees)
CREATE TABLE orders (
    order_id           NUMBER PRIMARY KEY,
    customer_id        NUMBER NOT NULL,
    sales_employee_id  NUMBER NOT NULL,
    order_date         DATE NOT NULL,
    delivery_date      DATE,
    order_status       VARCHAR2(30) DEFAULT 'PENDING',
    total_amount       NUMBER(12,2),
    tax_amount         NUMBER(12,2),
    discount_amount    NUMBER(12,2),
    payment_method     VARCHAR2(30),
    notes              VARCHAR2(500),
    created_date       DATE DEFAULT SYSDATE,
    CONSTRAINT fk_ord_cust FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE CASCADE,
    CONSTRAINT fk_ord_emp FOREIGN KEY (sales_employee_id) REFERENCES employees(employee_id),
    CONSTRAINT chk_ord_status CHECK (order_status IN ('PENDING', 'CONFIRMED', 'SHIPPED', 'DELIVERED', 'CANCELLED', 'RETURNED')),
    CONSTRAINT chk_ord_total CHECK (total_amount >= 0),
    CONSTRAINT chk_payment CHECK (payment_method IN ('CREDIT_CARD', 'BANK_TRANSFER', 'CASH', 'CHECK', 'DIGITAL_WALLET'))
);

COMMENT ON TABLE orders IS 'Sales orders placed by customers';
COMMENT ON COLUMN orders.sales_employee_id IS 'Employee who processed this order (FK to employees)';

-- Order_Items Table (Child of Orders and Products)
CREATE TABLE order_items (
    order_item_id      NUMBER PRIMARY KEY,
    order_id           NUMBER NOT NULL,
    product_id         NUMBER NOT NULL,
    quantity           NUMBER(6) NOT NULL,
    unit_price         NUMBER(10,2) NOT NULL,
    line_total         NUMBER(12,2),
    discount_percent   NUMBER(5,2) DEFAULT 0,
    created_date       DATE DEFAULT SYSDATE,
    CONSTRAINT fk_oi_ord FOREIGN KEY (order_id) REFERENCES orders(order_id) ON DELETE CASCADE,
    CONSTRAINT fk_oi_prod FOREIGN KEY (product_id) REFERENCES products(product_id),
    CONSTRAINT chk_qty CHECK (quantity > 0)
);

COMMENT ON TABLE order_items IS 'Individual line items within an order';

-- Inventory Table (Child of Products)
CREATE TABLE inventory (
    inventory_id       NUMBER PRIMARY KEY,
    product_id         NUMBER NOT NULL UNIQUE,
    warehouse_location VARCHAR2(50),
    quantity_on_hand   NUMBER(10) DEFAULT 0,
    quantity_reserved  NUMBER(10) DEFAULT 0,
    quantity_available NUMBER(10) DEFAULT 0,
    last_stock_check   DATE,
    reorder_quantity   NUMBER(5),
    supplier_id        NUMBER,
    updated_date       DATE DEFAULT SYSDATE,
    CONSTRAINT fk_inv_prod FOREIGN KEY (product_id) REFERENCES products(product_id) ON DELETE CASCADE,
    CONSTRAINT chk_qty_onhand CHECK (quantity_on_hand >= 0),
    CONSTRAINT chk_qty_reserved CHECK (quantity_reserved >= 0),
    CONSTRAINT chk_qty_available CHECK (quantity_available >= 0)
);

COMMENT ON TABLE inventory IS 'Real-time inventory management for products';

-- Customer_Reviews Table (Child of Customers and Products)
CREATE TABLE customer_reviews (
    review_id          NUMBER PRIMARY KEY,
    customer_id        NUMBER NOT NULL,
    product_id         NUMBER NOT NULL,
    review_rating      NUMBER(2) DEFAULT 5,
    review_text        VARCHAR2(1000),
    helpful_count      NUMBER(5) DEFAULT 0,
    review_status      VARCHAR2(20) DEFAULT 'PENDING',
    created_date       DATE DEFAULT SYSDATE,
    moderated_date     DATE,
    CONSTRAINT fk_rev_cust FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE CASCADE,
    CONSTRAINT fk_rev_prod FOREIGN KEY (product_id) REFERENCES products(product_id) ON DELETE CASCADE,
    CONSTRAINT chk_rating CHECK (review_rating BETWEEN 1 AND 5),
    CONSTRAINT chk_rev_status CHECK (review_status IN ('PENDING', 'APPROVED', 'REJECTED', 'FLAGGED'))
);

COMMENT ON TABLE customer_reviews IS 'Customer product ratings and reviews with moderation workflow';

-- ============================================================================
-- INDEXES
-- ============================================================================

-- Composite indexes on frequently filtered columns
CREATE INDEX idx_orders_customer_date 
    ON orders(customer_id, order_date DESC);

CREATE INDEX idx_orders_employee_status 
    ON orders(sales_employee_id, order_status);

CREATE INDEX idx_order_items_product 
    ON order_items(product_id);

-- Unique index for email lookup


-- Functional index for case-insensitive searches
CREATE INDEX idx_product_name_upper 
    ON products(UPPER(product_name));

CREATE INDEX idx_category_name_upper 
    ON product_categories(UPPER(category_name));

-- Index for inventory queries
CREATE INDEX idx_inventory_warehouse 
    ON inventory(warehouse_location);

-- Index for review queries
CREATE INDEX idx_reviews_product_rating 
    ON customer_reviews(product_id, review_rating DESC);

-- ============================================================================
-- VIEWS
-- ============================================================================

-- Simple View: Active Customers
CREATE OR REPLACE VIEW v_active_customers AS
SELECT 
    customer_id,
    first_name,
    last_name,
    email,
    customer_type,
    account_status,
    last_purchase_date
FROM customers
WHERE account_status = 'ACTIVE';

COMMENT ON TABLE v_active_customers IS 'Filtered view of active customer accounts only';

-- Complex View: Order Summary with Customer and Employee Details
CREATE OR REPLACE VIEW v_order_summary AS
SELECT 
    o.order_id,
    c.customer_id,
    c.first_name || ' ' || c.last_name AS customer_name,
    c.email AS customer_email,
    e.employee_id,
    e.first_name || ' ' || e.last_name AS sales_person,
    o.order_date,
    o.delivery_date,
    o.order_status,
    COUNT(oi.order_item_id) AS line_item_count,
    SUM(oi.quantity) AS total_items,
    o.total_amount,
    o.tax_amount,
    o.discount_amount,
    (o.total_amount + o.tax_amount - o.discount_amount) AS net_amount
FROM orders o
    JOIN customers c ON o.customer_id = c.customer_id
    JOIN employees e ON o.sales_employee_id = e.employee_id
    LEFT JOIN order_items oi ON o.order_id = oi.order_id
GROUP BY 
    o.order_id, c.customer_id, c.first_name, c.last_name, c.email,
    e.employee_id, e.first_name, e.last_name,
    o.order_date, o.delivery_date, o.order_status,
    o.total_amount, o.tax_amount, o.discount_amount;

COMMENT ON TABLE v_order_summary IS 'Comprehensive order view with aggregated metrics and related customer/employee data';

-- Aggregation View: Product Performance
CREATE OR REPLACE VIEW v_product_performance AS
SELECT 
    p.product_id,
    p.product_name,
    pc.category_name,
    p.unit_price,
    COUNT(DISTINCT oi.order_id) AS orders_count,
    SUM(oi.quantity) AS total_quantity_sold,
    SUM(oi.line_total) AS total_revenue,
    ROUND(AVG(oi.quantity), 2) AS avg_qty_per_order,
    COUNT(DISTINCT cr.review_id) AS review_count,
    ROUND(AVG(cr.review_rating), 2) AS avg_rating,
    i.quantity_on_hand,
    i.quantity_reserved,
    i.quantity_available
FROM products p
    JOIN product_categories pc ON p.category_id = pc.category_id
    LEFT JOIN order_items oi ON p.product_id = oi.product_id
    LEFT JOIN customer_reviews cr ON p.product_id = cr.product_id AND cr.review_status = 'APPROVED'
    LEFT JOIN inventory i ON p.product_id = i.product_id
WHERE p.discontinued_flag = 'N'
GROUP BY 
    p.product_id, p.product_name, pc.category_name, p.unit_price,
    i.quantity_on_hand, i.quantity_reserved, i.quantity_available;

COMMENT ON TABLE v_product_performance IS 'Multi-dimensional view showing sales, reviews, and inventory for each product';

-- View: Employee Sales Performance
CREATE OR REPLACE VIEW v_employee_sales_performance AS
SELECT 
    e.employee_id,
    e.first_name || ' ' || e.last_name AS employee_name,
    e.job_title,
    d.department_name,
    COUNT(DISTINCT o.order_id) AS total_orders,
    SUM(o.total_amount) AS total_sales_amount,
    ROUND(AVG(o.total_amount), 2) AS avg_order_value,
    COUNT(DISTINCT o.customer_id) AS unique_customers,
    MAX(o.order_date) AS last_order_date
FROM employees e
    JOIN departments d ON e.department_id = d.department_id
    LEFT JOIN orders o ON e.employee_id = o.sales_employee_id
GROUP BY 
    e.employee_id, e.first_name, e.last_name, e.job_title, d.department_name;

COMMENT ON TABLE v_employee_sales_performance IS 'Sales metrics aggregated at employee level with department context';

-- ============================================================================
-- STORED PROCEDURES
-- ============================================================================

-- Procedure 1: Create New Order with Validation
CREATE OR REPLACE PROCEDURE proc_create_order(
    p_customer_id       IN NUMBER,
    p_employee_id       IN NUMBER,
    p_delivery_date     IN DATE,
    p_order_id          OUT NUMBER,
    p_status_msg        OUT VARCHAR2
)
IS
    v_customer_count    NUMBER;
    v_employee_count    NUMBER;
    v_total_amount      NUMBER := 0;
BEGIN
    -- Validate customer exists
    SELECT COUNT(*) INTO v_customer_count FROM customers 
    WHERE customer_id = p_customer_id AND account_status = 'ACTIVE';
    
    IF v_customer_count = 0 THEN
        p_status_msg := 'ERROR: Customer not found or inactive';
        RETURN;
    END IF;
    
    -- Validate employee exists
    SELECT COUNT(*) INTO v_employee_count FROM employees 
    WHERE employee_id = p_employee_id;
    
    IF v_employee_count = 0 THEN
        p_status_msg := 'ERROR: Employee not found';
        RETURN;
    END IF;
    
    -- Create order
    SELECT seq_orders.NEXTVAL INTO p_order_id FROM DUAL;
    
    INSERT INTO orders (
        order_id, customer_id, sales_employee_id, order_date, delivery_date,
        order_status, total_amount, tax_amount, discount_amount, created_date
    ) VALUES (
        p_order_id, p_customer_id, p_employee_id, SYSDATE, p_delivery_date,
        'PENDING', 0, 0, 0, SYSDATE
    );
    
    p_status_msg := 'SUCCESS: Order created with ID ' || p_order_id;
    COMMIT;
    
EXCEPTION WHEN OTHERS THEN
    p_status_msg := 'ERROR: ' || SQLERRM;
    ROLLBACK;
END proc_create_order;
/

-- Procedure 2: Add Item to Order with Stock Validation
CREATE OR REPLACE PROCEDURE proc_add_order_item(
    p_order_id          IN NUMBER,
    p_product_id        IN NUMBER,
    p_quantity          IN NUMBER,
    p_order_item_id     OUT NUMBER,
    p_status_msg        OUT VARCHAR2
)
IS
    v_product_count     NUMBER;
    v_unit_price        NUMBER;
    v_available_qty     NUMBER;
    v_line_total        NUMBER;
BEGIN
    -- Validate product exists
    SELECT COUNT(*), unit_price INTO v_product_count, v_unit_price FROM products
    WHERE product_id = p_product_id AND discontinued_flag = 'N';
    
    IF v_product_count = 0 THEN
        p_status_msg := 'ERROR: Product not found or discontinued';
        RETURN;
    END IF;
    
    -- Check inventory availability
    SELECT quantity_available INTO v_available_qty FROM inventory
    WHERE product_id = p_product_id;
    
    IF v_available_qty < p_quantity THEN
        p_status_msg := 'ERROR: Insufficient inventory. Available: ' || v_available_qty;
        RETURN;
    END IF;
    
    -- Calculate line total
    v_line_total := p_quantity * v_unit_price;
    
    -- Insert order item
    SELECT seq_order_items.NEXTVAL INTO p_order_item_id FROM DUAL;
    
    INSERT INTO order_items (
        order_item_id, order_id, product_id, quantity, unit_price, line_total, created_date
    ) VALUES (
        p_order_item_id, p_order_id, p_product_id, p_quantity, v_unit_price, v_line_total, SYSDATE
    );
    
    -- Update inventory
    UPDATE inventory
    SET quantity_reserved = quantity_reserved + p_quantity,
        quantity_available = quantity_available - p_quantity,
        updated_date = SYSDATE
    WHERE product_id = p_product_id;
    
    p_status_msg := 'SUCCESS: Item added. Line total: ' || v_line_total;
    COMMIT;
    
EXCEPTION WHEN OTHERS THEN
    p_status_msg := 'ERROR: ' || SQLERRM;
    ROLLBACK;
END proc_add_order_item;
/

-- Procedure 3: Calculate and Update Order Total
CREATE OR REPLACE PROCEDURE proc_finalize_order(
    p_order_id          IN NUMBER,
    p_tax_rate          IN NUMBER DEFAULT 0.10,
    p_discount_percent  IN NUMBER DEFAULT 0,
    p_status_msg        OUT VARCHAR2
)
IS
    v_subtotal          NUMBER;
    v_tax               NUMBER;
    v_discount          NUMBER;
    v_final_total       NUMBER;
BEGIN
    -- Calculate subtotal from line items
    SELECT COALESCE(SUM(line_total), 0) INTO v_subtotal FROM order_items
    WHERE order_id = p_order_id;
    
    -- Calculate tax and discount
    v_tax := ROUND(v_subtotal * p_tax_rate, 2);
    v_discount := ROUND(v_subtotal * (p_discount_percent / 100), 2);
    v_final_total := v_subtotal + v_tax - v_discount;
    
    -- Update order totals
    UPDATE orders
    SET total_amount = v_subtotal,
        tax_amount = v_tax,
        discount_amount = v_discount,
        order_status = 'CONFIRMED'
    WHERE order_id = p_order_id;
    
    UPDATE customers
    SET last_purchase_date = SYSDATE
    WHERE customer_id = (SELECT customer_id FROM orders WHERE order_id = p_order_id);
    
    p_status_msg := 'SUCCESS: Order finalized. Total: ' || v_final_total;
    COMMIT;
    
EXCEPTION WHEN OTHERS THEN
    p_status_msg := 'ERROR: ' || SQLERRM;
    ROLLBACK;
END proc_finalize_order;
/

-- Procedure 4: Generate Monthly Sales Report
CREATE OR REPLACE PROCEDURE proc_monthly_sales_report(
    p_year              IN NUMBER,
    p_month             IN NUMBER,
    p_report_cursor     OUT SYS_REFCURSOR
)
IS
    v_first_day         DATE;
    v_last_day          DATE;
BEGIN
    v_first_day := TRUNC(TO_DATE(p_year || '-' || LPAD(p_month, 2, '0') || '-01', 'YYYY-MM-DD'));
    v_last_day := LAST_DAY(v_first_day);
    
    OPEN p_report_cursor FOR
    SELECT 
        e.employee_id,
        e.first_name || ' ' || e.last_name AS employee_name,
        d.department_name,
        COUNT(o.order_id) AS order_count,
        SUM(o.total_amount) AS total_sales,
        ROUND(AVG(o.total_amount), 2) AS avg_order_value,
        MAX(o.order_date) AS latest_order
    FROM employees e
        JOIN departments d ON e.department_id = d.department_id
        LEFT JOIN orders o ON e.employee_id = o.sales_employee_id 
            AND o.order_date >= v_first_day 
            AND o.order_date <= v_last_day
    GROUP BY e.employee_id, e.first_name, e.last_name, d.department_name
    ORDER BY total_sales DESC;
    
EXCEPTION WHEN OTHERS THEN
    NULL;
END proc_monthly_sales_report;
/

-- ============================================================================
-- PACKAGES
-- ============================================================================

CREATE OR REPLACE PACKAGE pkg_order_management IS
    
    -- Function to check product availability
    FUNCTION fn_check_availability(
        p_product_id    IN NUMBER,
        p_quantity      IN NUMBER
    ) RETURN BOOLEAN;
    
    -- Procedure to process refund
    PROCEDURE proc_refund_order(
        p_order_id      IN NUMBER,
        p_reason        IN VARCHAR2,
        p_status_msg    OUT VARCHAR2
    );
    
    -- Function to calculate discount
    FUNCTION fn_calculate_discount(
        p_customer_id   IN NUMBER,
        p_amount        IN NUMBER
    ) RETURN NUMBER;
    
END pkg_order_management;
/

CREATE OR REPLACE PACKAGE BODY pkg_order_management IS
    
    FUNCTION fn_check_availability(
        p_product_id    IN NUMBER,
        p_quantity      IN NUMBER
    ) RETURN BOOLEAN
    IS
        v_available     NUMBER;
    BEGIN
        SELECT quantity_available INTO v_available FROM inventory
        WHERE product_id = p_product_id;
        
        RETURN v_available >= p_quantity;
    EXCEPTION WHEN OTHERS THEN
        RETURN FALSE;
    END fn_check_availability;
    
    PROCEDURE proc_refund_order(
        p_order_id      IN NUMBER,
        p_reason        IN VARCHAR2,
        p_status_msg    OUT VARCHAR2
    )
    IS
        v_product_id    NUMBER;
        v_quantity      NUMBER;
        CURSOR c_items IS
            SELECT product_id, quantity FROM order_items WHERE order_id = p_order_id;
    BEGIN
        -- Return items to inventory
        FOR rec IN c_items LOOP
            UPDATE inventory
            SET quantity_available = quantity_available + rec.quantity,
                quantity_reserved = quantity_reserved - rec.quantity,
                updated_date = SYSDATE
            WHERE product_id = rec.product_id;
        END LOOP;
        
        -- Update order status
        UPDATE orders
        SET order_status = 'RETURNED'
        WHERE order_id = p_order_id;
        
        p_status_msg := 'SUCCESS: Order refunded. Reason: ' || p_reason;
        COMMIT;
    EXCEPTION WHEN OTHERS THEN
        p_status_msg := 'ERROR: ' || SQLERRM;
        ROLLBACK;
    END proc_refund_order;
    
    FUNCTION fn_calculate_discount(
        p_customer_id   IN NUMBER,
        p_amount        IN NUMBER
    ) RETURN NUMBER
    IS
        v_total_purchases  NUMBER;
        v_discount_rate     NUMBER := 0;
    BEGIN
        SELECT COALESCE(SUM(total_amount), 0) INTO v_total_purchases
        FROM orders
        WHERE customer_id = p_customer_id AND order_status IN ('CONFIRMED', 'SHIPPED', 'DELIVERED');
        
        -- Tiered discount logic
        IF v_total_purchases > 10000 THEN
            v_discount_rate := 0.15;
        ELSIF v_total_purchases > 5000 THEN
            v_discount_rate := 0.10;
        ELSIF v_total_purchases > 1000 THEN
            v_discount_rate := 0.05;
        END IF;
        
        RETURN ROUND(p_amount * v_discount_rate, 2);
    END fn_calculate_discount;
    
END pkg_order_management;
/

-- ============================================================================
-- TRIGGERS
-- ============================================================================

-- Trigger 1: Update Product Updated_Date on Insert/Update
CREATE OR REPLACE TRIGGER trg_products_audit
BEFORE UPDATE ON products
FOR EACH ROW
BEGIN
    :NEW.updated_date := SYSDATE;
END trg_products_audit;
/

-- Trigger 2: Validate Order Status Transition
CREATE OR REPLACE TRIGGER trg_orders_status_validation
BEFORE UPDATE ON orders
FOR EACH ROW
BEGIN
    IF :OLD.order_status = 'DELIVERED' AND :NEW.order_status != 'RETURNED' THEN
        RAISE_APPLICATION_ERROR(-20001, 'Cannot change status of delivered orders except to RETURNED');
    END IF;
    
    IF :OLD.order_status = 'CANCELLED' AND :NEW.order_status != 'CANCELLED' THEN
        RAISE_APPLICATION_ERROR(-20002, 'Cancelled orders cannot be modified');
    END IF;
END trg_orders_status_validation;
/

-- Trigger 3: Maintain Inventory Available Quantity
CREATE OR REPLACE TRIGGER trg_inventory_available_calc
AFTER UPDATE ON inventory
FOR EACH ROW
BEGIN
    UPDATE inventory
    SET quantity_available = quantity_on_hand - quantity_reserved
    WHERE inventory_id = :NEW.inventory_id;
END trg_inventory_available_calc;
/

-- Trigger 4: Log Review Status Changes
CREATE TABLE review_audit_log (
    log_id              NUMBER PRIMARY KEY,
    review_id           NUMBER,
    old_status          VARCHAR2(20),
    new_status          VARCHAR2(20),
    changed_by          VARCHAR2(50),
    changed_date        DATE
);

CREATE SEQUENCE seq_review_audit_log START WITH 1;

CREATE OR REPLACE TRIGGER trg_review_status_audit
AFTER UPDATE ON customer_reviews
FOR EACH ROW
BEGIN
    IF :OLD.review_status != :NEW.review_status THEN
        INSERT INTO review_audit_log (
            log_id, review_id, old_status, new_status, changed_by, changed_date
        ) VALUES (
            seq_review_audit_log.NEXTVAL, :NEW.review_id, 
            :OLD.review_status, :NEW.review_status, USER, SYSDATE
        );
    END IF;
END trg_review_status_audit;
/

-- ============================================================================
-- SUMMARY: DATABASE OBJECT DEPENDENCIES
-- ============================================================================

/*
DEPENDENCY HIERARCHY:

Level 1 - Root Tables (No dependencies on other tables):
  ├── departments
  ├── product_categories
  └── customers

Level 2 - Tables dependent on Level 1:
  ├── employees (FK → departments)
  ├── products (FK → product_categories)
  └── departments (self-referencing: manager_id → employees)

Level 3 - Tables dependent on Level 2:
  ├── orders (FK → customers, employees)
  ├── inventory (FK → products)
  └── customer_reviews (FK → customers, products)

Level 4 - Tables dependent on Level 3:
  └── order_items (FK → orders, products)

VIEWS DEPENDENCY:
  ├── v_active_customers (→ customers)
  ├── v_order_summary (→ orders, customers, employees, order_items)
  ├── v_product_performance (→ products, categories, order_items, reviews, inventory)
  └── v_employee_sales_performance (→ employees, departments, orders)

PROCEDURES/PACKAGES:
  ├── proc_create_order (→ customers, employees, orders)
  ├── proc_add_order_item (→ orders, products, inventory, order_items)
  ├── proc_finalize_order (→ orders, order_items, customers)
  ├── proc_monthly_sales_report (→ employees, departments, orders)
  ├── pkg_order_management.fn_check_availability (→ inventory)
  ├── pkg_order_management.proc_refund_order (→ order_items, inventory, orders)
  └── pkg_order_management.fn_calculate_discount (→ orders, customers)

TRIGGERS:
  ├── trg_products_audit (→ products)
  ├── trg_orders_status_validation (→ orders)
  ├── trg_inventory_available_calc (→ inventory)
  └── trg_review_status_audit (→ customer_reviews, review_audit_log)

INDEXES:
  - 14 indexes covering frequently accessed paths
  - Composite, unique, and functional indexes for performance

SEQUENCES:
  - 7 sequences for auto-increment of primary keys
*/

-- ============================================================================
-- CONSTRAINTS ALREADY ENABLED BY DEFAULT
-- ============================================================================
-- All constraints are created and enabled during table creation.
-- No additional enabling required.

-- ============================================================================
-- END OF SCHEMA CREATION
-- ============================================================================