package protocol

import (
	"bytes"
	"encoding/json"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"hash-of-wisdom/internal/pow/challenge"
	"hash-of-wisdom/internal/quotes"
)

// TestSpecCompliance_ChallengeResponse verifies challenge response matches PROTOCOL.md format
func TestSpecCompliance_ChallengeResponse(t *testing.T) {
	resp := &ChallengeResponse{
		Challenge: &challenge.Challenge{
			Timestamp:  1640995200,
			Difficulty: 4,
			Resource:   "quotes",
			Random:     []byte{0xa1, 0xb2, 0xc3, 0xd4, 0xe5, 0xf6},
			HMAC:       []byte("base64url_encoded_signature"),
		},
	}

	var buf bytes.Buffer
	err := resp.Encode(&buf)
	require.NoError(t, err)

	// Skip header (5 bytes) and get payload
	header := buf.Bytes()[:5]
	payload := buf.Bytes()[5:]

	// Verify header format
	assert.Equal(t, byte(ChallengeResponseType), header[0])
	assert.Equal(t, uint32(len(payload)), uint32(header[1])<<24|uint32(header[2])<<16|uint32(header[3])<<8|uint32(header[4]))

	// Verify JSON payload matches spec format
	var decoded map[string]interface{}
	err = json.Unmarshal(payload, &decoded)
	require.NoError(t, err)

	// Check required fields from spec
	assert.Contains(t, decoded, "timestamp")
	assert.Contains(t, decoded, "difficulty")
	assert.Contains(t, decoded, "resource")
	assert.Contains(t, decoded, "random")
	assert.Contains(t, decoded, "hmac")

	assert.Equal(t, float64(1640995200), decoded["timestamp"])
	assert.Equal(t, float64(4), decoded["difficulty"])
	assert.Equal(t, "quotes", decoded["resource"])
}

// TestSpecCompliance_SolutionRequest verifies solution request matches PROTOCOL.md format
func TestSpecCompliance_SolutionRequest(t *testing.T) {
	req := &SolutionRequest{
		Challenge: challenge.Challenge{
			Timestamp:  1640995200,
			Difficulty: 4,
			Resource:   "quotes",
			Random:     []byte{0xa1, 0xb2, 0xc3, 0xd4, 0xe5, 0xf6},
			HMAC:       []byte("base64url_encoded_signature"),
		},
		Nonce: 12345,
	}

	var buf bytes.Buffer
	err := req.Encode(&buf)
	require.NoError(t, err)

	// Skip header and get payload
	payload := buf.Bytes()[5:]

	// Verify JSON payload matches spec format
	var decoded map[string]interface{}
	err = json.Unmarshal(payload, &decoded)
	require.NoError(t, err)

	// Check required top-level fields
	assert.Contains(t, decoded, "challenge")
	assert.Contains(t, decoded, "nonce")
	assert.Equal(t, float64(12345), decoded["nonce"])

	// Check challenge structure
	challenge := decoded["challenge"].(map[string]interface{})
	assert.Contains(t, challenge, "timestamp")
	assert.Contains(t, challenge, "difficulty")
	assert.Contains(t, challenge, "resource")
	assert.Contains(t, challenge, "random")
	assert.Contains(t, challenge, "hmac")
}

// TestSpecCompliance_QuoteResponse verifies quote response matches PROTOCOL.md format
func TestSpecCompliance_QuoteResponse(t *testing.T) {
	resp := &SolutionResponse{
		Quote: &quotes.Quote{
			Text:   "The only way to do great work is to love what you do.",
			Author: "Steve Jobs",
		},
	}

	var buf bytes.Buffer
	err := resp.Encode(&buf)
	require.NoError(t, err)

	// Skip header and get payload
	payload := buf.Bytes()[5:]

	// Verify JSON payload matches spec format
	var decoded map[string]interface{}
	err = json.Unmarshal(payload, &decoded)
	require.NoError(t, err)

	// Check required fields from spec
	assert.Contains(t, decoded, "text")
	assert.Contains(t, decoded, "author")
	assert.Equal(t, "The only way to do great work is to love what you do.", decoded["text"])
	assert.Equal(t, "Steve Jobs", decoded["author"])
}

// TestSpecCompliance_ErrorResponse verifies error response matches PROTOCOL.md format
func TestSpecCompliance_ErrorResponse(t *testing.T) {
	resp := &ErrorResponse{
		Code:       "INVALID_SOLUTION",
		Message:    "The provided PoW solution is incorrect",
		RetryAfter: 30,
		Details:    map[string]string{"reason": "hash verification failed"},
	}

	var buf bytes.Buffer
	err := resp.Encode(&buf)
	require.NoError(t, err)

	// Skip header and get payload
	payload := buf.Bytes()[5:]

	// Verify JSON payload matches spec format
	var decoded map[string]interface{}
	err = json.Unmarshal(payload, &decoded)
	require.NoError(t, err)

	// Check required fields from spec
	assert.Contains(t, decoded, "code")
	assert.Contains(t, decoded, "message")
	assert.Equal(t, "INVALID_SOLUTION", decoded["code"])
	assert.Equal(t, "The provided PoW solution is incorrect", decoded["message"])

	// Check optional fields
	assert.Contains(t, decoded, "retry_after")
	assert.Contains(t, decoded, "details")
	assert.Equal(t, float64(30), decoded["retry_after"])
}

// TestSpecCompliance_MessageSizeLimits verifies 8KB payload limit
func TestSpecCompliance_MessageSizeLimits(t *testing.T) {
	decoder := NewMessageDecoder()

	// Create a message that exceeds 8KB payload limit
	largePayload := make([]byte, MaxPayloadSize+1)
	for i := range largePayload {
		largePayload[i] = 'A'
	}

	// Create message with oversized payload
	var buf bytes.Buffer
	buf.WriteByte(byte(ChallengeRequestType))
	buf.Write([]byte{0x00, 0x00, 0x20, 0x01}) // 8193 bytes (8KB + 1)
	buf.Write(largePayload)

	// Should reject oversized payload
	_, err := decoder.Decode(&buf)
	assert.Error(t, err)
	assert.Contains(t, err.Error(), "payload length")
	assert.Contains(t, err.Error(), "exceeds maximum")
}