/**
 * Per-model token pricing for cost estimation in analyzer_analyses.estimated_cost_usd.
 *
 * Rates are USD per 1,000,000 tokens.
 *
 * VERIFY QUARTERLY against https://docs.claude.com/en/docs/about-claude/pricing
 * Last verified: 2026-04-15
 */

import { HAIKU, SONNET, OPUS, type ModelId } from './models';

interface ModelRate {
  /** USD per 1M input tokens */
  input: number;
  /** USD per 1M output tokens */
  output: number;
  /** USD per 1M tokens read from prompt cache (~0.1× input) */
  cacheRead: number;
  /** USD per 1M tokens written to 5-minute prompt cache (~1.25× input) */
  cacheWrite5m: number;
}

export const PRICING: Record<ModelId, ModelRate> = {
  [HAIKU]:  { input: 1.0, output:  5.0, cacheRead: 0.1,  cacheWrite5m: 1.25 },
  [SONNET]: { input: 3.0, output: 15.0, cacheRead: 0.3,  cacheWrite5m: 3.75 },
  [OPUS]:   { input: 5.0, output: 25.0, cacheRead: 0.5,  cacheWrite5m: 6.25 },
};

export interface TokenUsage {
  input_tokens: number;
  output_tokens: number;
  cache_creation_input_tokens?: number;
  cache_read_input_tokens?: number;
}

/**
 * USD cost of a single LLM call given its token usage. Caches are billed
 * separately from raw input tokens — cache_read at ~0.1×, cache_write at ~1.25×.
 */
export function estimateCostUsd(model: ModelId, usage: TokenUsage): number {
  const rate = PRICING[model];
  const cacheRead = usage.cache_read_input_tokens ?? 0;
  const cacheWrite = usage.cache_creation_input_tokens ?? 0;
  const uncachedInput = usage.input_tokens; // SDK reports this as the uncached remainder
  const cost =
    (uncachedInput / 1_000_000) * rate.input +
    (usage.output_tokens / 1_000_000) * rate.output +
    (cacheRead / 1_000_000) * rate.cacheRead +
    (cacheWrite / 1_000_000) * rate.cacheWrite5m;
  // Round to 4 decimals (matches analyzer_analyses.estimated_cost_usd numeric(10,4)).
  return Math.round(cost * 10_000) / 10_000;
}