"""Model pricing table and cost estimation.

Prices are USD per 1,000,000 tokens. The table is a built-in default; a suite may
extend or override entries through ``[skill_eval.pricing]`` in its config. Model
lookup is a longest-substring match so that dated/suffixed model names
(``claude-haiku-4-5-20251001``) still resolve to a base entry (``claude-haiku-4``).
"""

# USD per 1,000,000 tokens.
# GitHub Models prices: https://docs.github.com/en/billing/reference/costs-for-github-models
# Anthropic prices: https://www.anthropic.com/pricing
DEFAULT_PRICING: dict[str, dict[str, float]] = {
    # GitHub Models (OpenAI)
    "gpt-4.1": {"input": 2.00, "output": 8.00},
    "gpt-4.1-mini": {"input": 0.40, "output": 1.60},
    "gpt-4o-mini": {"input": 0.15, "output": 0.60},
    "gpt-4o": {"input": 2.50, "output": 10.00},
    # Anthropic
    "claude-opus-4": {"input": 15.00, "output": 75.00},
    "claude-sonnet-4": {"input": 3.00, "output": 15.00},
    "claude-haiku-4": {"input": 0.80, "output": 4.00},
    "claude-haiku-3": {"input": 0.80, "output": 4.00},
}


def find_pricing(
    model_name: str, pricing: dict[str, dict[str, float]]
) -> dict[str, float] | None:
    """Return the pricing entry for ``model_name`` using a longest-substring match."""
    best_key, best_len = None, 0
    for key in pricing:
        if key in model_name and len(key) > best_len:
            best_key, best_len = key, len(key)
    return pricing[best_key] if best_key else None


def calculate_cost(
    model_name: str,
    input_tokens: int,
    output_tokens: int,
    pricing: dict[str, dict[str, float]] | None = None,
) -> float | None:
    """Return the estimated USD cost, or ``None`` if the model is not in the table."""
    table = pricing if pricing is not None else DEFAULT_PRICING
    entry = find_pricing(model_name, table)
    if entry is None:
        return None
    return round(
        input_tokens * entry["input"] / 1_000_000
        + output_tokens * entry["output"] / 1_000_000,
        6,
    )