Method Compress

pkg/context/compression_strategy.go:204–292

Compress 实现 CompressionStrategy 接口

(
	ctx context.Context,
	messages []Message,
	config WindowManagerConfig,
)

// Compress 实现 CompressionStrategy 接口
func (s *TokenBasedStrategy) Compress(
	ctx context.Context,
	messages []Message,
	config WindowManagerConfig,
) ([]Message, error) {
	// 计算目标 Token 数
	targetTokens := int(float64(config.Budget.AvailableTokens()) * s.targetUsage)

	// 计算当前 Token 数
	currentTokens, err := s.tokenCounter.EstimateMessages(ctx, messages)
	if err != nil {
		return nil, fmt.Errorf("failed to estimate current tokens: %w", err)
	}

	// 如果已经在目标范围内，不需要压缩
	if currentTokens <= targetTokens {
		return messages, nil
	}

	// 保留的消息索引（从后往前）
	keepIndices := make(map[int]bool)

	// 1. 始终保留 system 消息
	if config.AlwaysKeepSystem {
		for i, msg := range messages {
			if msg.Role == "system" {
				keepIndices[i] = true
			}
		}
	}

	// 2. 始终保留最近的 N 条消息
	recentCount := min(config.AlwaysKeepRecent, len(messages))
	for i := len(messages) - recentCount; i < len(messages); i++ {
		keepIndices[i] = true
	}

	// 3. 从后往前逐步添加消息，直到达到 Token 目标
	for i := len(messages) - 1; i >= 0; i-- {
		if keepIndices[i] {
			continue // 已经保留
		}

		// 尝试添加这条消息
		testIndices := make(map[int]bool)
		for k := range keepIndices {
			testIndices[k] = true
		}
		testIndices[i] = true

		// 构建测试消息列表
		testMessages := []Message{}
		for j := range messages {
			if testIndices[j] {
				testMessages = append(testMessages, messages[j])
			}
		}