package unpacker

import (
	"testing"

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

func TestFixedLengthUnpacker(t *testing.T) {
	u := NewFixedLengthUnpacker(4)

	// 测试单个消息
	data := []byte("test")
	messages, remaining, consumed, err := u.Unpack(data)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, 1, len(messages), "Expected 1 message")
	assert.Equal(t, "test", string(messages[0]), "Expected 'test'")
	assert.Equal(t, 0, len(remaining), "Expected no remaining data")
	assert.Equal(t, len(data), consumed, "Expected consumed equals input data length")
}

func TestFixedLengthUnpackerMultipleMessages(t *testing.T) {
	u := NewFixedLengthUnpacker(4)

	// 测试多个消息
	data := []byte("testdata")
	messages, remaining, consumed, err := u.Unpack(data)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, 2, len(messages), "Expected 2 messages")
	assert.Equal(t, "test", string(messages[0]), "Expected 'test'")
	assert.Equal(t, "data", string(messages[1]), "Expected 'data'")
	assert.Equal(t, 0, len(remaining), "Expected no remaining data")
	assert.Equal(t, len(data), consumed, "Expected consumed equals input data length")
}

func TestFixedLengthUnpackerIncompleteMessage(t *testing.T) {
	u := NewFixedLengthUnpacker(4)

	// 测试不完整的消息
	data := []byte("te")
	messages, remaining, consumed, err := u.Unpack(data)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, 0, len(messages), "Expected 0 messages")
	assert.Equal(t, "te", string(remaining), "Expected 'te' as remaining")
	assert.Equal(t, len(data), consumed, "Expected all data consumed when no complete message")
}

func TestFixedLengthUnpackerPack(t *testing.T) {
	u := NewFixedLengthUnpacker(4)

	// 测试打包（数据长度匹配）
	data := []byte("test")
	packed, err := u.Pack(data)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, "test", string(packed), "Expected 'test'")

	// 测试打包（数据长度不足，需要填充）
	data2 := []byte("te")
	packed2, err := u.Pack(data2)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, 4, len(packed2), "Expected 4 bytes")
	assert.Equal(t, "te", string(packed2[:2]), "Expected 'te' prefix")

	// 测试打包（数据长度超过，需要截断）
	data3 := []byte("testdata")
	packed3, err := u.Pack(data3)
	require.NoError(t, err, "Expected no error")
	assert.Equal(t, 4, len(packed3), "Expected 4 bytes")
	assert.Equal(t, "test", string(packed3), "Expected 'test'")
}

func TestFixedLengthUnpackerPartialMessages(t *testing.T) {
	u := NewFixedLengthUnpacker(4)

	// 测试部分消息 + 完整消息
	data1 := []byte("te")
	messages, remaining, consumed, err := u.Unpack(data1)
	require.NoError(t, err)
	assert.Equal(t, 0, len(messages))
	assert.Equal(t, "te", string(remaining))
	assert.Equal(t, len(data1), consumed, "Expected all data consumed when no complete message")

	// 添加更多数据完成第一个消息并开始第二个消息
	data2 := []byte("stte")
	messages, remaining, consumed, err = u.Unpack(data2)
	require.NoError(t, err)
	assert.Equal(t, 1, len(messages))
	assert.Equal(t, "test", string(messages[0]))
	assert.Equal(t, "te", string(remaining))
	// consumed应该是2（完成了"test"中的"st"部分，但"te"被保存到buffer中）
	assert.Greater(t, consumed, 0, "Expected some data consumed")
	assert.LessOrEqual(t, consumed, len(data2), "Expected consumed <= input data length")
}