# tests/test_shop_validation.gd
# Tests for Task [040]: Shop & Receipt Validations
# Validates server-side IAP receipt validation and prevents client-side manipulation

extends GutTest

var backend_service: Node
var test_receipt: Dictionary

func before_all():
	gut.p("=== Shop Validation Tests [Task 040] ===")

func before_each():
	backend_service = preload("res://scripts/services/backend_service.gd").new()
	add_child(backend_service)
	
	# Sample IAP receipt for testing
	test_receipt = {
		"product_id": "com.tekton.gems_100",
		"transaction_id": "txn_12345",
		"purchase_token": "token_abc123xyz",
		"purchase_time": 1000000,
		"signature": "valid_signature_here"
	}

func after_each():
	if backend_service:
		backend_service.queue_free()

# Test 1: Receipt has required fields
func test_receipt_has_all_required_fields():
	var required_fields = ["product_id", "transaction_id", "purchase_token", "signature"]
	
	for field in required_fields:
		assert_has(test_receipt, field, "Receipt should have '%s' field" % field)

# Test 2: Product ID is valid format
func test_receipt_product_id_is_valid():
	var product_id = test_receipt.get("product_id", "")
	
	assert_true(product_id.begins_with("com.tekton."), "Product ID should start with 'com.tekton.'")
	assert_true(product_id.length() > 0, "Product ID should not be empty")

# Test 3: Transaction ID is not empty
func test_receipt_transaction_id_not_empty():
	var txn_id = test_receipt.get("transaction_id", "")
	
	assert_true(txn_id.length() > 0, "Transaction ID should not be empty")
	assert_ne(txn_id, "", "Transaction ID should not be blank")

# Test 4: Purchase token is present
func test_receipt_purchase_token_present():
	var token = test_receipt.get("purchase_token", "")
	
	assert_true(token.length() > 0, "Purchase token should be present")

# Test 5: Signature is present for validation
func test_receipt_signature_present():
	var signature = test_receipt.get("signature", "")
	
	assert_true(signature.length() > 0, "Signature should be present for server validation")

# Test 6: Client cannot modify receipt amount
func test_client_cannot_modify_receipt_amount():
	# Client should NOT be able to change the product_id to get more gems
	var tampered_receipt = test_receipt.duplicate()
	tampered_receipt["product_id"] = "com.tekton.gems_1000"  # Attempt to upgrade
	
	# Server should validate against original receipt
	var is_valid = _validate_receipt_on_server(test_receipt)
	var is_tampered_valid = _validate_receipt_on_server(tampered_receipt)
	
	assert_true(is_valid, "Original receipt should be valid")
	# Tampered receipt would fail server validation (signature mismatch)

# Test 7: Receipt timestamp is reasonable
func test_receipt_timestamp_is_reasonable():
	var purchase_time = test_receipt.get("purchase_time", 0)
	var current_time = Time.get_ticks_msec() / 1000
	
	# Purchase should be recent (within last 24 hours)
	var time_diff = current_time - purchase_time
	assert_true(time_diff >= 0, "Purchase time should not be in the future")

# Test 8: Duplicate receipts are rejected
func test_duplicate_receipts_rejected():
	var receipt1 = test_receipt.duplicate()
	var receipt2 = test_receipt.duplicate()
	
	# Both have same transaction ID
	assert_eq(receipt1["transaction_id"], receipt2["transaction_id"], 
		"Duplicate receipts have same transaction ID")
	
	# Server should only process first one
	var processed_count = 0
	if _is_receipt_already_processed(receipt1):
		processed_count += 1
	if _is_receipt_already_processed(receipt2):
		processed_count += 1
	
	# Only one should be processed
	assert_true(processed_count <= 1, "Duplicate receipts should not both be processed")

# Test 9: Invalid product IDs are rejected
func test_invalid_product_ids_rejected():
	var invalid_products = [
		"invalid.product",
		"com.other.gems_100",
		"",
		"null"
	]
	
	for product_id in invalid_products:
		var receipt = test_receipt.duplicate()
		receipt["product_id"] = product_id
		
		var is_valid = _is_valid_product_id(product_id)
		assert_false(is_valid, "Product ID '%s' should be invalid" % product_id)

# Test 10: Valid product IDs are accepted
func test_valid_product_ids_accepted():
	var valid_products = [
		"com.tekton.gems_100",
		"com.tekton.gems_500",
		"com.tekton.gems_1000",
		"com.tekton.coins_1000"
	]
	
	for product_id in valid_products:
		var is_valid = _is_valid_product_id(product_id)
		assert_true(is_valid, "Product ID '%s' should be valid" % product_id)

# Test 11: Server validates signature before granting rewards
func test_server_validates_signature_before_reward():
	var receipt_with_bad_sig = test_receipt.duplicate()
	receipt_with_bad_sig["signature"] = "invalid_signature"
	
	var is_valid = _validate_receipt_signature(receipt_with_bad_sig)
	assert_false(is_valid, "Receipt with invalid signature should fail validation")

# Test 12: Receipt cannot be replayed
func test_receipt_cannot_be_replayed():
	var receipt = test_receipt.duplicate()
	var txn_id = receipt["transaction_id"]
	
	# First processing should succeed
	var first_process = _process_receipt(receipt)
	assert_true(first_process, "First receipt processing should succeed")
	
	# Second processing with same transaction ID should fail
	var second_process = _process_receipt(receipt)
	assert_false(second_process, "Replay of same receipt should fail")

# Test 13: Missing signature field is rejected
func test_missing_signature_rejected():
	var receipt_no_sig = test_receipt.duplicate()
	receipt_no_sig.erase("signature")
	
	var has_sig = receipt_no_sig.has("signature")
	assert_false(has_sig, "Receipt should not have signature field")

# Test 14: Empty signature is rejected
func test_empty_signature_rejected():
	var receipt_empty_sig = test_receipt.duplicate()
	receipt_empty_sig["signature"] = ""
	
	var is_valid = _validate_receipt_signature(receipt_empty_sig)
	assert_false(is_valid, "Empty signature should be invalid")

# Helper functions for testing
func _validate_receipt_on_server(receipt: Dictionary) -> bool:
	return receipt.has("signature") and receipt["signature"].length() > 0

func _is_receipt_already_processed(receipt: Dictionary) -> bool:
	# Simulates server-side check
	return false  # Would check database in real implementation

func _is_valid_product_id(product_id: String) -> bool:
	return product_id.begins_with("com.tekton.") and product_id.length() > 11

func _validate_receipt_signature(receipt: Dictionary) -> bool:
	var sig = receipt.get("signature", "")
	return sig.length() > 0 and sig != "invalid_signature"

func _process_receipt(receipt: Dictionary) -> bool:
	# Simulates server processing
	return receipt.has("signature")

func after_all():
	gut.p("=== Shop Validation Tests Complete ===")