package gst

import (
	"testing"
)

func TestCalculateLineItem(t *testing.T) {
	c := NewCalculator()

	product := Product{
		SKU:            "TEST01",
		BasePrice:      100,
		WholesalePrice: 90,
		GSTRate:        Rate18,
	}

	// Case 1: Retail, Intra-state
	item := c.CalculateLineItem(product, 2, CustomerRetail, false)
	if item.UnitPrice != 100 {
		t.Errorf("Expected UnitPrice 100, got %f", item.UnitPrice)
	}
	if item.TaxableVal != 200 {
		t.Errorf("Expected TaxableVal 200, got %f", item.TaxableVal)
	}
	if item.CGSTAmount != 18 { // 9% of 200
		t.Errorf("Expected CGST 18, got %f", item.CGSTAmount)
	}
	if item.IGSTAmount != 0 {
		t.Errorf("Expected IGST 0, got %f", item.IGSTAmount)
	}
	if item.TotalAmount != 236 { // 200 + 18 + 18
		t.Errorf("Expected Total 236, got %f", item.TotalAmount)
	}

	// Case 2: Wholesale, Inter-state
	item = c.CalculateLineItem(product, 10, CustomerWholesale, true)
	if item.UnitPrice != 90 {
		t.Errorf("Expected UnitPrice 90, got %f", item.UnitPrice)
	}
	if item.TaxableVal != 900 {
		t.Errorf("Expected TaxableVal 900, got %f", item.TaxableVal)
	}
	if item.CGSTAmount != 0 {
		t.Errorf("Expected CGST 0, got %f", item.CGSTAmount)
	}
	if item.IGSTAmount != 162 { // 18% of 900
		t.Errorf("Expected IGST 162, got %f", item.IGSTAmount)
	}
	if item.TotalAmount != 1062 { // 900 + 162
		t.Errorf("Expected Total 1062, got %f", item.TotalAmount)
	}
}

func TestCalculateInvoice(t *testing.T) {
	c := NewCalculator()
	product := Product{SKU: "TEST01", BasePrice: 100, GSTRate: Rate18}

	item1 := c.CalculateLineItem(product, 1, CustomerRetail, false)
	item2 := c.CalculateLineItem(product, 1, CustomerRetail, false)

	// Test with convenience fee (intra-state)
	invoice := c.CalculateInvoice([]LineItem{item1, item2}, 50, false)

	// Convenience fee is taxed at 18%
	// SubTotal should include convenience fee: 100 + 100 + 50 = 250
	expectedSubTotal := 250.0
	if invoice.SubTotal != expectedSubTotal {
		t.Errorf("Expected SubTotal %f, got %f", expectedSubTotal, invoice.SubTotal)
	}

	// Convenience fee tax: 50 * 0.18 = 9
	expectedFeeTax := 9.0
	if invoice.ConvenienceFeeTax != expectedFeeTax {
		t.Errorf("Expected ConvenienceFeeTax %f, got %f", expectedFeeTax, invoice.ConvenienceFeeTax)
	}

	// Total CGST: 9 + 9 + 4.5 = 22.5 (from items + half of fee tax)
	expectedCGST := 22.5
	if invoice.TotalCGST != expectedCGST {
		t.Errorf("Expected TotalCGST %f, got %f", expectedCGST, invoice.TotalCGST)
	}

	// GrandTotal: SubTotal + CGST + SGST = 250 + 22.5 + 22.5 = 295
	expectedTotal := 295.0
	if invoice.GrandTotal != expectedTotal {
		t.Errorf("Expected GrandTotal %f, got %f", expectedTotal, invoice.GrandTotal)
	}
}

func TestCalculateInvoiceInterState(t *testing.T) {
	c := NewCalculator()
	product := Product{SKU: "TEST01", BasePrice: 100, GSTRate: Rate18}

	item := c.CalculateLineItem(product, 1, CustomerRetail, true)

	// Test with convenience fee (inter-state)
	invoice := c.CalculateInvoice([]LineItem{item}, 50, true)

	// SubTotal: 100 + 50 = 150
	expectedSubTotal := 150.0
	if invoice.SubTotal != expectedSubTotal {
		t.Errorf("Expected SubTotal %f, got %f", expectedSubTotal, invoice.SubTotal)
	}

	// Convenience fee tax: 50 * 0.18 = 9
	expectedFeeTax := 9.0
	if invoice.ConvenienceFeeTax != expectedFeeTax {
		t.Errorf("Expected ConvenienceFeeTax %f, got %f", expectedFeeTax, invoice.ConvenienceFeeTax)
	}

	// Total IGST: 18 + 9 = 27 (from item + fee tax)
	expectedIGST := 27.0
	if invoice.TotalIGST != expectedIGST {
		t.Errorf("Expected TotalIGST %f, got %f", expectedIGST, invoice.TotalIGST)
	}

	// GrandTotal: SubTotal + IGST = 150 + 27 = 177
	expectedTotal := 177.0
	if invoice.GrandTotal != expectedTotal {
		t.Errorf("Expected GrandTotal %f, got %f", expectedTotal, invoice.GrandTotal)
	}
}