/**
 * OpenCode Go 模型价格表 + 每次请求的用量/费用估算记录。
 * 零 pi 依赖的纯业务模块。
 *
 * 实测：每次 chat/completions 响应自带 usage（含 cached_tokens / cache_write_tokens），
 * 但 cost 字段恒为 "0"（Go 包月制，官方不按次结算金额）。因此金额只能自己按 token × 单价估算。
 * 价格表来自官方文档 https://opencode.ai/docs/go/（静态数据，需内置）。
 */

/** 单价（美元 / 百万 token）。可选峰/谷两档。 */
export interface ModelPrice {
  input: number;
  output: number;
  cacheRead: number;
  cacheWrite?: number;
  // 简化的峰谷配置：peak 为 true 时使用 peak 价
  peakInput?: number;
  peakOutput?: number;
  peakCacheRead?: number;
  peakCacheWrite?: number;
}

export const DEFAULT_PRICES: Record<string, ModelPrice> = {
  "deepseek-v4-flash": {
    input: 0.22, output: 0.66, cacheRead: 0.007,
    peakInput: 0.44, peakOutput: 1.32, peakCacheRead: 0.014,
  },
  "deepseek-v4-pro": {
    input: 0.66, output: 1.98, cacheRead: 0.022,
    peakInput: 1.32, peakOutput: 3.96, peakCacheRead: 0.044,
  },
  // 其余模型：普通单价（来自官方文档），无峰谷时 pe 为同一值
  "glm-5.3": { input: 1.4, output: 4.4, cacheRead: 0.26 },
  "glm-5.2": { input: 1.4, output: 4.4, cacheRead: 0.26 },
  "glm-5.1": { input: 1.4, output: 4.4, cacheRead: 0.26 },
  "gpt-5.6-luna": { input: 0.2, output: 1.2, cacheRead: 0.02, cacheWrite: 0.25, peakInput: 0.4, peakOutput: 1.8, peakCacheRead: 0.04, peakCacheWrite: 0.5 },
  "kimi-k3": { input: 3.0, output: 15.0, cacheRead: 0.3 },
  "kimi-k2.7-code": { input: 0.95, output: 4.0, cacheRead: 0.19 },
  "kimi-k2.6": { input: 0.95, output: 4.0, cacheRead: 0.16 },
  "mimo-v2.5": { input: 0.14, output: 0.28, cacheRead: 0.0028 },
  "mimo-v2.5-pro": { input: 0.435, output: 0.87, cacheRead: 0.003625 },
  "minimax-m3": { input: 0.3, output: 1.2, cacheRead: 0.06 },
  "minimax-m2.7": { input: 0.3, output: 1.2, cacheRead: 0.06, cacheWrite: 0.375 },
  "qwen3.8-max": { input: 2.0, output: 6.0, cacheRead: 0.25, cacheWrite: 2.5 },
  "qwen3.7-max": { input: 2.5, output: 7.5, cacheRead: 0.5, cacheWrite: 3.125 },
  "qwen3.7-plus": { input: 0.4, output: 1.6, cacheRead: 0.04, cacheWrite: 0.5 },
  "qwen3.6-plus": { input: 0.5, output: 3.0, cacheRead: 0.05, cacheWrite: 0.625 },
  "hy3": { input: 0.14, output: 0.58, cacheRead: 0.035 },
};

export function isPeakHour(date = new Date()): boolean {
  // Peak: 01:00-04:00 与 06:00-10:00 UTC
  const h = date.getUTCHours();
  return (h >= 1 && h < 4) || (h >= 6 && h < 10);
}

export interface CostBreakdown {
  /** 美元，估算值 */
  input: number;
  output: number;
  cacheRead: number;
  cacheWrite: number;
  total: number;
}

/**
 * 估算一次请求的费用（美元）。
 * modelId: 如 deepseek-v4-flash；peak: 是否按峰时价；priceMap: 可注入自定义价格表。
 */
export function estimateCost(
  modelId: string | undefined,
  usage: { prompt?: number; completion?: number; cached?: number; cacheWrite?: number },
  peak: boolean,
  priceMap: Record<string, ModelPrice> = DEFAULT_PRICES,
): CostBreakdown {
  const base = modelId ? priceMap[modelId] : undefined;
  const inputPrice = peak && base?.peakInput !== undefined ? base.peakInput : base?.input ?? 0;
  const outputPrice = peak && base?.peakOutput !== undefined ? base.peakOutput : base?.output ?? 0;
  const cacheReadPrice = peak && base?.peakCacheRead !== undefined ? base.peakCacheRead : base?.cacheRead ?? 0;
  const cacheWritePrice = peak && base?.peakCacheWrite !== undefined ? base.peakCacheWrite : base?.cacheWrite ?? 0;

  const prompt = usage.prompt ?? 0;
  const cached = usage.cached ?? 0;
  const cacheWrite = usage.cacheWrite ?? 0;
  const completion = usage.completion ?? 0;

  // 缓存命中的 token 属于 prompt，但按 cacheRead 计价；未命中部分按正常 input 价。
  const nonCachedPrompt = Math.max(0, prompt - cached);
  const input = (nonCachedPrompt * inputPrice) / 1_000_000;
  const cacheReadCost = (cached * cacheReadPrice) / 1_000_000;
  const cacheWriteCost = (cacheWrite * cacheWritePrice) / 1_000_000;
  const output = (completion * outputPrice) / 1_000_000;

  return {
    input: round(input),
    output: round(output),
    cacheRead: round(cacheReadCost),
    cacheWrite: round(cacheWriteCost),
    total: round(input + output + cacheReadCost + cacheWriteCost),
  };
}

function round(n: number): number {
  return Math.round(n * 1e6) / 1e6;
}

/** 一次请求的用量记录（落盘/汇总用）。 */
export interface UsageRecord {
  ts: number;
  sessionId?: string;
  model?: string;
  prompt: number;
  completion: number;
  cached: number;
  cacheWrite: number;
  peak: boolean;
  cost: CostBreakdown;
}

export interface UsageStats {
  records: number;
  prompt: number;
  completion: number;
  cached: number;
  cacheWrite: number;
  cost: CostBreakdown;
  /** 缓存命中率 = cached / (cached+nonCachedPrompt)，0~1；无记录为 0 */
  cacheHitRate: number;
}

export function summarizeStats(records: UsageRecord[]): UsageStats {
  let prompt = 0;
  let completion = 0;
  let cached = 0;
  let cacheWrite = 0;
  const cost: CostBreakdown = { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 };
  for (const r of records) {
    prompt += r.prompt;
    completion += r.completion;
    cached += r.cached;
    cacheWrite += r.cacheWrite;
    cost.input += r.cost.input;
    cost.output += r.cost.output;
    cost.cacheRead += r.cost.cacheRead;
    cost.cacheWrite += r.cost.cacheWrite;
    cost.total += r.cost.total;
  }
  const nonCachedPrompt = Math.max(0, prompt - cached);
  const cacheHitRate = nonCachedPrompt + cached > 0 ? cached / (cached + nonCachedPrompt) : 0;
  return {
    records: records.length,
    prompt,
    completion,
    cached,
    cacheWrite,
    cost,
    cacheHitRate: round(cacheHitRate),
  };
}