package protocol

import (
	"encoding/binary"
	"testing"
)

// This file demonstrates what FIELD-LEVEL testing would look like
// Currently these tests are NOT run automatically because they require
// complex parsing logic for each API.

// TestJoinGroupResponseStructure shows what we SHOULD test but currently don't
func TestJoinGroupResponseStructure(t *testing.T) {
	t.Skip("This is a demonstration test - shows what we SHOULD check")

	// Hypothetical: build a JoinGroup response
	// response := buildJoinGroupResponseV6(correlationID, generationID, protocolType, ...)

	// What we SHOULD verify:
	t.Log("Field-level checks we should perform:")
	t.Log("  1. Error code (int16) - always present")
	t.Log("  2. Generation ID (int32) - always present")
	t.Log("  3. Protocol type (string/compact string) - nullable in some versions")
	t.Log("  4. Protocol name (string/compact string) - always present")
	t.Log("  5. Leader (string/compact string) - always present")
	t.Log("  6. Member ID (string/compact string) - always present")
	t.Log("  7. Members array - NON-NULLABLE, can be empty but must exist")
	t.Log("     ^-- THIS is where the current bug is!")

	// Example of what parsing would look like:
	// offset := 0
	// errorCode := binary.BigEndian.Uint16(response[offset:])
	// offset += 2
	// generationID := binary.BigEndian.Uint32(response[offset:])
	// offset += 4
	// ... parse protocol type ...
	// ... parse protocol name ...
	// ... parse leader ...
	// ... parse member ID ...
	// membersLength := parseCompactArray(response[offset:])
	// if membersLength < 0 {
	//     t.Error("Members array is null, but it should be non-nullable!")
	// }
}

// TestProduceResponseStructure shows another example
func TestProduceResponseStructure(t *testing.T) {
	t.Skip("This is a demonstration test - shows what we SHOULD check")

	t.Log("Produce response v7 structure:")
	t.Log("  1. Topics array - must not be null")
	t.Log("     - Topic name (string)")
	t.Log("     - Partitions array - must not be null")
	t.Log("       - Partition ID (int32)")
	t.Log("       - Error code (int16)")
	t.Log("       - Base offset (int64)")
	t.Log("       - Log append time (int64)")
	t.Log("       - Log start offset (int64)")
	t.Log("  2. Throttle time (int32) - v1+")
}

// CompareWithReferenceImplementation shows ideal testing approach
func TestCompareWithReferenceImplementation(t *testing.T) {
	t.Skip("This would require a reference Kafka broker or client library")

	// Ideal approach:
	t.Log("1. Generate test data")
	t.Log("2. Build response with our Gateway")
	t.Log("3. Build response with kafka-go or Sarama library")
	t.Log("4. Compare byte-by-byte")
	t.Log("5. If different, highlight which fields differ")

	// This would catch:
	// - Wrong field order
	// - Wrong field encoding
	// - Missing fields
	// - Null vs empty distinctions
}

// CurrentTestingApproach documents what we actually do
func TestCurrentTestingApproach(t *testing.T) {
	t.Log("Current testing strategy (as of Oct 2025):")
	t.Log("")
	t.Log("LEVEL 1: Static Code Analysis")
	t.Log("  Tool: check_responses.sh")
	t.Log("  Checks: Correlation ID patterns")
	t.Log("  Coverage: Good for known issues")
	t.Log("")
	t.Log("LEVEL 2: Protocol Format Tests")
	t.Log("  Tool: TestFlexibleResponseHeaderFormat")
	t.Log("  Checks: Flexible vs non-flexible classification")
	t.Log("  Coverage: Header format only")
	t.Log("")
	t.Log("LEVEL 3: Integration Testing")
	t.Log("  Tool: Schema Registry, kafka-go, Sarama, Java client")
	t.Log("  Checks: Real client compatibility")
	t.Log("  Coverage: Complete but requires manual debugging")
	t.Log("")
	t.Log("MISSING: Field-level response body validation")
	t.Log("  This is why JoinGroup issue wasn't caught by unit tests")
}

// parseCompactArray is a helper that would be needed for field-level testing
func parseCompactArray(data []byte) int {
	// Compact array encoding: varint length (length+1 for non-null, 0 for null)
	length := int(data[0])
	if length == 0 {
		return -1 // null
	}
	return length - 1 // actual length
}

// Example of a REAL field-level test we could write
func TestMetadataResponseHasBrokers(t *testing.T) {
	t.Skip("Example of what a real field-level test would look like")

	// Build a minimal metadata response
	response := make([]byte, 0, 256)

	// Brokers array (non-nullable)
	brokerCount := uint32(1)
	response = append(response,
		byte(brokerCount>>24),
		byte(brokerCount>>16),
		byte(brokerCount>>8),
		byte(brokerCount))

	// Broker 1
	response = append(response, 0, 0, 0, 1) // node_id = 1
	// ... more fields ...

	// Parse it back
	offset := 0
	parsedCount := binary.BigEndian.Uint32(response[offset : offset+4])

	// Verify
	if parsedCount == 0 {
		t.Error("Metadata response has 0 brokers - should have at least 1")
	}

	t.Logf("✓ Metadata response correctly has %d broker(s)", parsedCount)
}