initial commit

OpenRouter/TokenTracker.cs

@@ -0,0 +1,80 @@
+namespace AnchorCli.OpenRouter;
+
+/// <summary>
+/// Tracks token usage and calculates costs for the session.
+/// </summary>
+internal sealed class TokenTracker
+{
+    public long SessionInputTokens { get; private set; }
+    public long SessionOutputTokens { get; private set; }
+    public int RequestCount { get; private set; }
+
+    /// <summary>Maximum context window for the model (tokens). 0 = unknown.</summary>
+    public int ContextLength { get; set; }
+
+    /// <summary>Input tokens from the most recent API response — approximates current context size.</summary>
+    public int LastInputTokens { get; private set; }
+
+    /// <summary>USD per input token.</summary>
+    public decimal InputPrice { get; set; }
+
+    /// <summary>USD per output token.</summary>
+    public decimal OutputPrice { get; set; }
+
+    /// <summary>Fixed USD per API request.</summary>
+    public decimal RequestPrice { get; set; }
+
+    /// <summary>
+    /// Record usage from one response (may span multiple LLM rounds).
+    /// </summary>
+    public void AddUsage(int inputTokens, int outputTokens)
+    {
+        SessionInputTokens += inputTokens;
+        SessionOutputTokens += outputTokens;
+        LastInputTokens = inputTokens;
+        RequestCount++;
+    }
+
+    /// <summary>
+    /// Returns true if the context is getting too large and should be compacted.
+    /// Triggers at min(75% of model context, 100K tokens).
+    /// </summary>
+    public bool ShouldCompact()
+    {
+        if (LastInputTokens <= 0) return false;
+
+        int threshold = ContextLength > 0
+            ? Math.Min((int)(ContextLength * 0.75), 100_000)
+            : 100_000;
+
+        return LastInputTokens >= threshold;
+    }
+
+    /// <summary>Context usage as a percentage (0-100). Returns -1 if context length is unknown.</summary>
+    public double ContextUsagePercent =>
+        ContextLength > 0 && LastInputTokens > 0
+            ? (double)LastInputTokens / ContextLength * 100.0
+            : -1;
+
+    /// <summary>
+    /// Calculate cost for a single response.
+    /// </summary>
+    public decimal CalculateCost(int inputTokens, int outputTokens) =>
+        inputTokens * InputPrice +
+        outputTokens * OutputPrice +
+        RequestPrice;
+
+    /// <summary>
+    /// Total session cost.
+    /// </summary>
+    public decimal SessionCost =>
+        SessionInputTokens * InputPrice +
+        SessionOutputTokens * OutputPrice +
+        RequestCount * RequestPrice;
+
+    public static string FormatTokens(long count) =>
+        count >= 1_000 ? $"{count / 1_000.0:F1}k" : count.ToString("N0");
+
+    public static string FormatCost(decimal cost) =>
+        cost < 0.01m ? $"${cost:F4}" : $"${cost:F2}";
+}