test(#745): Add tests for cost estimator

Tests for cost estimation, pricing lookup.
Refs #745

tests/test_cost_estimator.py

@@ -0,0 +1,41 @@
+"""
+Tests for cost estimator tool (#745).
+"""
+
+import pytest
+from tools.cost_estimator import estimate_cost, get_pricing, CostEstimate, PRICING
+
+
+class TestCostEstimator:
+    def test_estimate_cost_basic(self):
+        result = estimate_cost(1000, 500, "openrouter", "claude-sonnet-4")
+        assert result.input_tokens == 1000
+        assert result.output_tokens == 500
+        assert result.total_cost_usd > 0
+    
+    def test_local_is_free(self):
+        result = estimate_cost(1000000, 1000000, "local", "llama-3")
+        assert result.total_cost_usd == 0.0
+    
+    def test_get_pricing_openrouter(self):
+        pricing = get_pricing("openrouter", "claude-opus-4")
+        assert pricing["input"] == 15.0
+        assert pricing["output"] == 75.0
+    
+    def test_get_pricing_unknown_model(self):
+        pricing = get_pricing("openrouter", "unknown-model")
+        assert pricing == PRICING["openrouter"]["default"]
+    
+    def test_get_pricing_unknown_provider(self):
+        pricing = get_pricing("unknown-provider", "model")
+        assert pricing == PRICING["openrouter"]["default"]
+    
+    def test_cost_estimate_dataclass(self):
+        result = estimate_cost(1000, 500, "nous", "hermes-3-405b")
+        assert isinstance(result, CostEstimate)
+        assert result.provider == "nous"
+        assert result.model == "hermes-3-405b"
+
+
+if __name__ == "__main__":
+    pytest.main([__file__])

tools/cost_estimator.py

@@ -0,0 +1,192 @@
+"""
+Provider Cost Estimator — Estimate API costs from token counts.
+
+Provides cost estimation for different LLM providers based on
+token counts and provider pricing.
+"""
+
+from typing import Dict, Optional, Tuple
+from dataclasses import dataclass
+
+
+@dataclass
+class CostEstimate:
+    """Cost estimate for a request."""
+    input_tokens: int
+    output_tokens: int
+    input_cost_usd: float
+    output_cost_usd: float
+    total_cost_usd: float
+    provider: str
+    model: str
+
+
+# Pricing table (USD per 1M tokens) — as of April 2026
+PRICING = {
+    "openrouter": {
+        "claude-opus-4": {"input": 15.0, "output": 75.0},
+        "claude-sonnet-4": {"input": 3.0, "output": 15.0},
+        "claude-haiku-3.5": {"input": 0.80, "output": 4.0},
+        "gpt-4o": {"input": 2.50, "output": 10.0},
+        "gpt-4o-mini": {"input": 0.15, "output": 0.60},
+        "gemini-2.5-pro": {"input": 1.25, "output": 10.0},
+        "gemini-2.5-flash": {"input": 0.15, "output": 0.60},
+        "llama-4-scout": {"input": 0.20, "output": 0.80},
+        "llama-4-maverick": {"input": 0.50, "output": 2.0},
+        "default": {"input": 1.0, "output": 3.0},
+    },
+    "nous": {
+        "hermes-3-405b": {"input": 5.0, "output": 5.0},
+        "mixtral-8x22b": {"input": 2.0, "output": 2.0},
+        "hermes-2-mixtral-8x7b": {"input": 0.90, "output": 0.90},
+        "default": {"input": 2.0, "output": 2.0},
+    },
+    "anthropic": {
+        "claude-opus-4": {"input": 15.0, "output": 75.0},
+        "claude-sonnet-4": {"input": 3.0, "output": 15.0},
+        "claude-haiku-3.5": {"input": 0.80, "output": 4.0},
+        "default": {"input": 3.0, "output": 15.0},
+    },
+    "local": {
+        # Local models are free (electricity only)
+        "default": {"input": 0.0, "output": 0.0},
+    },
+}
+
+
+def get_pricing(provider: str, model: str) -> Dict[str, float]:
+    """
+    Get pricing for a provider/model combination.
+    
+    Args:
+        provider: Provider name (openrouter, nous, anthropic, local)
+        model: Model name
+        
+    Returns:
+        Dict with 'input' and 'output' prices per 1M tokens
+    """
+    provider = provider.lower().strip()
+    model = model.lower().strip()
+    
+    provider_pricing = PRICING.get(provider, PRICING["openrouter"])
+    
+    # Try exact match first
+    if model in provider_pricing:
+        return provider_pricing[model]
+    
+    # Try partial match
+    for key in provider_pricing:
+        if key in model or model in key:
+            return provider_pricing[key]
+    
+    # Default
+    return provider_pricing.get("default", {"input": 1.0, "output": 3.0})
+
+
+def estimate_cost(
+    input_tokens: int,
+    output_tokens: int,
+    provider: str = "openrouter",
+    model: str = "default"
+) -> CostEstimate:
+    """
+    Estimate cost for a request.
+    
+    Args:
+        input_tokens: Number of input tokens
+        output_tokens: Number of output tokens
+        provider: Provider name
+        model: Model name
+        
+    Returns:
+        CostEstimate with breakdown
+    """
+    pricing = get_pricing(provider, model)
+    
+    # Calculate costs (pricing is per 1M tokens)
+    input_cost = (input_tokens / 1_000_000) * pricing["input"]
+    output_cost = (output_tokens / 1_000_000) * pricing["output"]
+    total_cost = input_cost + output_cost
+    
+    return CostEstimate(
+        input_tokens=input_tokens,
+        output_tokens=output_tokens,
+        input_cost_usd=input_cost,
+        output_cost_usd=output_cost,
+        total_cost_usd=total_cost,
+        provider=provider,
+        model=model,
+    )
+
+
+def estimate_session_cost(messages: list, provider: str = "openrouter", model: str = "default") -> CostEstimate:
+    """
+    Estimate cost for a session based on message count.
+    
+    Args:
+        messages: List of messages (each with 'role' and 'content')
+        provider: Provider name
+        model: Model name
+        
+    Returns:
+        CostEstimate for the session
+    """
+    # Rough token estimation: ~4 chars per token
+    input_tokens = 0
+    output_tokens = 0
+    
+    for msg in messages:
+        content = msg.get("content", "")
+        if isinstance(content, str):
+            tokens = len(content) // 4
+            if msg.get("role") == "user":
+                input_tokens += tokens
+            elif msg.get("role") == "assistant":
+                output_tokens += tokens
+    
+    return estimate_cost(input_tokens, output_tokens, provider, model)
+
+
+def format_cost_report(estimates: list) -> str:
+    """
+    Format a list of cost estimates as a report.
+    
+    Args:
+        estimates: List of CostEstimate objects
+        
+    Returns:
+        Formatted report string
+    """
+    total_cost = sum(e.total_cost_usd for e in estimates)
+    total_input = sum(e.input_tokens for e in estimates)
+    total_output = sum(e.output_tokens for e in estimates)
+    
+    lines = [
+        "# Cost Report",
+        "",
+        f"**Total Cost:** ${total_cost:.4f}",
+        f"**Total Tokens:** {total_input + total_output:,} (input: {total_input:,}, output: {total_output:,})",
+        "",
+        "| Provider | Model | Input Tokens | Output Tokens | Cost |",
+        "|----------|-------|--------------|---------------|------|",
+    ]
+    
+    for e in estimates:
+        lines.append(f"| {e.provider} | {e.model} | {e.input_tokens:,} | {e.output_tokens:,} | ${e.total_cost_usd:.4f} |")
+    
+    lines.append("")
+    lines.append(f"*Generated by cost_estimator.py*")
+    
+    return "\n".join(lines)
+
+
+def get_supported_providers() -> list:
+    """Get list of supported providers."""
+    return list(PRICING.keys())
+
+
+def get_provider_models(provider: str) -> list:
+    """Get list of models for a provider."""
+    provider = provider.lower().strip()
+    provider_pricing = PRICING.get(provider, {})
+    return [k for k in provider_pricing.keys() if k != "default"]