添加对话上下文窗口管理

Co-Authored-By: Claude <noreply@anthropic.com>

stream/tokens.go

@@ -8,6 +8,8 @@ import (
 	"unicode"
 
 	"aichat/message"
+
+	"github.com/volcengine/volcengine-go-sdk/service/arkruntime/model"
 )
 
 type Stats struct {
@@ -97,6 +99,48 @@ func EstimateChatMessagesTokens(messages []message.ChatMessage) int {
 	return total
 }
 
+func EstimateArkMessagesTokens(messages []*model.ChatCompletionMessage) int {
+	total := 0
+	for _, msg := range messages {
+		if msg == nil {
+			continue
+		}
+		total += EstimateTokenCount(string(msg.Role)) + estimateArkContentTokens(msg.Content) + 4
+		if msg.ToolCallID != "" {
+			total += EstimateTokenCount(msg.ToolCallID) + 2
+		}
+		for _, call := range msg.ToolCalls {
+			if call == nil {
+				continue
+			}
+			total += EstimateTokenCount(call.ID) + EstimateTokenCount(call.Function.Name) + EstimateTokenCount(call.Function.Arguments) + 8
+		}
+	}
+	return total
+}
+
+func estimateArkContentTokens(content *model.ChatCompletionMessageContent) int {
+	if content == nil {
+		return 0
+	}
+	if content.StringValue != nil {
+		return EstimateTokenCount(*content.StringValue)
+	}
+	total := 0
+	for _, part := range content.ListValue {
+		if part == nil {
+			continue
+		}
+		if part.Text != "" {
+			total += EstimateTokenCount(part.Text)
+		}
+		if part.ImageURL != nil {
+			total += 85
+		}
+	}
+	return total
+}
+
 func EstimateTokenCount(text string) int {
 	text = strings.TrimSpace(text)
 	if text == "" {