feat(src): add price calculation function (#6)

* add pricing_on_token_usage function

* modify model names and revise functionality of calc pricing

Author: 4R5T

src/pricing.py

@@ -0,0 +1,49 @@
+# Pricing data for each model (prices are in dollars per million (1,000,000) tokens)
+MODEL_PRICING = {
+    # OpenAI models
+    "gpt-3.5-turbo": (0.5, 1.5),
+    "gpt-4o-mini": (0.15, 0.6),
+    "gpt-4o": (2.5, 10),
+    "o1-preview": (15, 60),
+    "o1-mini": (1.1, 4.4),
+    "o1": (15, 60),
+    # OpenRouter models
+    "llama3.1-405b": (3.5, 3.5),
+    # Anthropic models
+    "claude-3-sonnet-v1": (0.8, 4),
+    "claude-3-sonnet": (3, 15),
+    "claude-3-5-sonnet-v2": (3, 15),
+    "claude-3-5-sonnet": (3, 15),
+    "claude-3-haiku-v1": (0.25, 1.25),
+    "claude-3-haiku": (0.25, 1.25),
+    "claude-3-opus-v1": (15, 75),
+    "claude-3-opus": (0.8, 4),
+    # DeepSeek models
+    "deepseek-chat": (0.07, 0.27),
+    "deepseek-reasoner": (0.14, 0.55),
+    # Google Gemini models
+    "gemini-1.5-flash": (0.01875, 0.075),
+    "gemini-1.5-pro": (0.3125, 1.25),
+}
+
+def calculate_pricing(model: str, input_tokens: int, output_tokens: int) -> float:
+    # Check if the model exists
+    if model not in MODEL_PRICING:
+        for m in MODEL_PRICING:
+            if model.startswith(m):
+                model = m
+            else:
+                raise ValueError(f"Pricing for '{model}' is not found.")
+    
+    input_price, output_price = MODEL_PRICING[model]
+    
+    # Check if pricing data is available
+    if input_price is None or output_price is None:
+        raise ValueError(f"Pricing for '{model}' is unavailable.")
+    
+    # The pricing is per million (1,000,000) tokens.
+    input_cost = (input_tokens / 1000000) * input_price
+    output_cost = (output_tokens / 1000000) * output_price
+    
+    total_cost = input_cost + output_cost
+    return total_cost