feat: Add TokenTracker to track token usage for LLM calls

lightrag/utils.py

@@ -953,3 +953,53 @@ def check_storage_env_vars(storage_name: str) -> None:
             f"Storage implementation '{storage_name}' requires the following "
             f"environment variables: {', '.join(missing_vars)}"
         )
+
+
+class TokenTracker:
+    """Track token usage for LLM calls."""
+
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.prompt_tokens = 0
+        self.completion_tokens = 0
+        self.total_tokens = 0
+        self.call_count = 0
+
+    def add_usage(self, token_counts):
+        """Add token usage from one LLM call.
+
+        Args:
+            token_counts: A dictionary containing prompt_tokens, completion_tokens, total_tokens
+        """
+        self.prompt_tokens += token_counts.get("prompt_tokens", 0)
+        self.completion_tokens += token_counts.get("completion_tokens", 0)
+
+        # If total_tokens is provided, use it directly; otherwise calculate the sum
+        if "total_tokens" in token_counts:
+            self.total_tokens += token_counts["total_tokens"]
+        else:
+            self.total_tokens += token_counts.get(
+                "prompt_tokens", 0
+            ) + token_counts.get("completion_tokens", 0)
+
+        self.call_count += 1
+
+    def get_usage(self):
+        """Get current usage statistics."""
+        return {
+            "prompt_tokens": self.prompt_tokens,
+            "completion_tokens": self.completion_tokens,
+            "total_tokens": self.total_tokens,
+            "call_count": self.call_count,
+        }
+
+    def __str__(self):
+        usage = self.get_usage()
+        return (
+            f"LLM call count: {usage['call_count']}, "
+            f"Prompt tokens: {usage['prompt_tokens']}, "
+            f"Completion tokens: {usage['completion_tokens']}, "
+            f"Total tokens: {usage['total_tokens']}"
+        )