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backend/internal/translator/common/cache_control.go

@@ -0,0 +1,67 @@
+package common
+
+import (
+	"fmt"
+
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+)
+
+// AttachCacheControl copies a Claude-compatible cache_control object from src onto dst.
+// Returns dst unchanged when cache_control is missing or not an object.
+func AttachCacheControl(dst []byte, src gjson.Result) []byte {
+	cc := src.Get("cache_control")
+	if !cc.Exists() || cc.Type == gjson.Null || !cc.IsObject() {
+		return dst
+	}
+	out, err := sjson.SetRawBytes(dst, "cache_control", []byte(cc.Raw))
+	if err != nil {
+		return dst
+	}
+	return out
+}
+
+// AttachMessageCacheControl applies message-level cache_control onto the last content block.
+// Part-level cache_control wins when the last block already has one.
+// String content is promoted to a content array so Claude can accept cache_control.
+func AttachMessageCacheControl(msg []byte, src gjson.Result) []byte {
+	cc := src.Get("cache_control")
+	if !cc.Exists() || cc.Type == gjson.Null || !cc.IsObject() {
+		return msg
+	}
+
+	content := gjson.GetBytes(msg, "content")
+	if content.IsArray() {
+		arr := content.Array()
+		if len(arr) == 0 {
+			return msg
+		}
+		lastIdx := len(arr) - 1
+		if arr[lastIdx].Get("cache_control").Exists() {
+			return msg
+		}
+		path := fmt.Sprintf("content.%d.cache_control", lastIdx)
+		out, err := sjson.SetRawBytes(msg, path, []byte(cc.Raw))
+		if err != nil {
+			return msg
+		}
+		return out
+	}
+
+	if content.Type != gjson.String {
+		return msg
+	}
+
+	textPart := []byte(`{"type":"text","text":""}`)
+	textPart, _ = sjson.SetBytes(textPart, "text", content.String())
+	textPart, errSet := sjson.SetRawBytes(textPart, "cache_control", []byte(cc.Raw))
+	if errSet != nil {
+		return msg
+	}
+	out, err := sjson.SetRawBytes(msg, "content", []byte("[]"))
+	if err != nil {
+		return msg
+	}
+	out, _ = sjson.SetRawBytes(out, "content.-1", textPart)
+	return out
+}