"""Track LLM API usage and costs."""

import json
from datetime import datetime, date
from pathlib import Path
from typing import Dict, List, Optional


# Pricing per 1M tokens (as of 2026-02-13)
_PRICING = {
    "claude-haiku-4-5-20251001": {
        "input": 0.25,
        "output": 1.25,
    },
    "claude-sonnet-4-5-20250929": {
        "input": 3.00,
        "output": 15.00,
        "cache_write": 3.75,  # Cache creation
        "cache_read": 0.30,   # 90% discount on cache hits
    },
    "claude-opus-4-6": {
        "input": 15.00,
        "output": 75.00,
        "cache_write": 18.75,
        "cache_read": 1.50,
    },
}


class UsageTracker:
    """Track and calculate costs for LLM API usage."""

    def __init__(self, storage_file: str = "usage_data.json") -> None:
        self.storage_file = Path(storage_file)
        self.usage_data: List[Dict] = []
        self._load()

    def _load(self) -> None:
        """Load usage data from file."""
        if self.storage_file.exists():
            with open(self.storage_file, encoding="utf-8") as f:
                self.usage_data = json.load(f)

    def _save(self) -> None:
        """Save usage data to file."""
        with open(self.storage_file, "w", encoding="utf-8") as f:
            json.dump(self.usage_data, f, indent=2)

    def track(
        self,
        model: str,
        input_tokens: int,
        output_tokens: int,
        cache_creation_tokens: int = 0,
        cache_read_tokens: int = 0,
    ) -> None:
        """Record an API call's token usage."""
        entry = {
            "timestamp": datetime.now().isoformat(),
            "date": str(date.today()),
            "model": model,
            "input_tokens": input_tokens,
            "output_tokens": output_tokens,
            "cache_creation_tokens": cache_creation_tokens,
            "cache_read_tokens": cache_read_tokens,
        }
        self.usage_data.append(entry)
        self._save()

    def get_daily_usage(
        self, target_date: Optional[str] = None
    ) -> Dict[str, int]:
        """Get total token usage for a specific date.

        Args:
            target_date: Date string (YYYY-MM-DD). Defaults to today.

        Returns:
            Dict with total tokens by type.
        """
        if target_date is None:
            target_date = str(date.today())

        totals = {
            "input_tokens": 0,
            "output_tokens": 0,
            "cache_creation_tokens": 0,
            "cache_read_tokens": 0,
        }

        for entry in self.usage_data:
            if entry.get("date") == target_date:
                totals["input_tokens"] += entry.get("input_tokens", 0)
                totals["output_tokens"] += entry.get("output_tokens", 0)
                totals["cache_creation_tokens"] += entry.get(
                    "cache_creation_tokens", 0
                )
                totals["cache_read_tokens"] += entry.get(
                    "cache_read_tokens", 0
                )

        return totals

    def calculate_cost(
        self,
        model: str,
        input_tokens: int,
        output_tokens: int,
        cache_creation_tokens: int = 0,
        cache_read_tokens: int = 0,
    ) -> float:
        """Calculate cost in USD for token usage.

        Args:
            model: Model name (e.g., "claude-haiku-4-5-20251001")
            input_tokens: Number of input tokens
            output_tokens: Number of output tokens
            cache_creation_tokens: Tokens written to cache (Sonnet/Opus only)
            cache_read_tokens: Tokens read from cache (Sonnet/Opus only)

        Returns:
            Total cost in USD
        """
        pricing = _PRICING.get(model)
        if not pricing:
            # Unknown model, estimate using Haiku pricing (conservative)
            pricing = _PRICING["claude-haiku-4-5-20251001"]

        cost = 0.0

        # Base input/output costs
        cost += (input_tokens / 1_000_000) * pricing["input"]
        cost += (output_tokens / 1_000_000) * pricing["output"]

        # Cache costs (Sonnet/Opus only)
        if cache_creation_tokens and "cache_write" in pricing:
            cost += (cache_creation_tokens / 1_000_000) * pricing["cache_write"]
        if cache_read_tokens and "cache_read" in pricing:
            cost += (cache_read_tokens / 1_000_000) * pricing["cache_read"]

        return cost

    def get_daily_cost(self, target_date: Optional[str] = None) -> Dict:
        """Get total cost and breakdown for a specific date.

        Returns:
            Dict with total_cost, breakdown by model, and token counts
        """
        if target_date is None:
            target_date = str(date.today())

        total_cost = 0.0
        model_breakdown: Dict[str, float] = {}
        totals = self.get_daily_usage(target_date)

        for entry in self.usage_data:
            if entry.get("date") != target_date:
                continue

            model = entry["model"]
            cost = self.calculate_cost(
                model=model,
                input_tokens=entry.get("input_tokens", 0),
                output_tokens=entry.get("output_tokens", 0),
                cache_creation_tokens=entry.get("cache_creation_tokens", 0),
                cache_read_tokens=entry.get("cache_read_tokens", 0),
            )

            total_cost += cost
            model_breakdown[model] = model_breakdown.get(model, 0.0) + cost

        return {
            "date": target_date,
            "total_cost": round(total_cost, 4),
            "model_breakdown": {
                k: round(v, 4) for k, v in model_breakdown.items()
            },
            "token_totals": totals,
        }

    def get_total_cost(self) -> Dict:
        """Get lifetime total cost and stats."""
        total_cost = 0.0
        total_calls = len(self.usage_data)
        model_breakdown: Dict[str, float] = {}

        for entry in self.usage_data:
            model = entry["model"]
            cost = self.calculate_cost(
                model=model,
                input_tokens=entry.get("input_tokens", 0),
                output_tokens=entry.get("output_tokens", 0),
                cache_creation_tokens=entry.get("cache_creation_tokens", 0),
                cache_read_tokens=entry.get("cache_read_tokens", 0),
            )

            total_cost += cost
            model_breakdown[model] = model_breakdown.get(model, 0.0) + cost

        return {
            "total_cost": round(total_cost, 4),
            "total_calls": total_calls,
            "model_breakdown": {
                k: round(v, 4) for k, v in model_breakdown.items()
            },
        }