/**
 * 上游客户端 · 样例文件实现（实施计划 §6：仓库根实测响应快照 —— `api.log.token.json`
 * / `api.status.json`，未入库、绝不提交）。开发期以 `UPSTREAM_SOURCE=fixture` 启用。
 *
 * 快照缺失的接口（`/api/usage/token` 无快照）就地按实测结构合成：总量类字段取自
 * `api.log.token.json` 首条日志的 `other.subscription_*`（真实形状），保证 fixture
 * 下的登记结果与 seed 数据（阶段 4）同一形状。
 *
 * 错误分支的仿真约定（key 内容大小写不敏感；仅 fixture 模式生效，见实施计划「实现假设」）：
 * 含 `reject` → 401 key_rejected · 含 `forbidden` → 403 key_rejected · 含 `unavailable` → 网络故障
 */
import { readFileSync } from 'node:fs'

import { DEFAULT_QUOTA_PER_UNIT } from '@naku/shared'

import { env } from '../lib/env'
import { errorMessage, UpstreamError } from './errors'
import type { UpstreamClient } from './client'
import type { UpstreamLogRecord, UpstreamStatus, UpstreamTokenUsage } from './types'

/** 仓库根（本文件位于 apps/server/src/upstream/）——样例快照的默认目录 */
const REPO_ROOT = new URL('../../../../', import.meta.url)

export interface FixtureUpstreamOptions {
  /** 样例文件目录；缺省取 env.newapiFixtureDir，再退到仓库根 */
  dir?: string | URL
}

function readSnapshot<T>(dir: string | URL, name: string): T {
  try {
    return JSON.parse(readFileSync(new URL(name, dir), 'utf8')) as T
  } catch (err) {
    throw new UpstreamError(
      'upstream_unavailable',
      `样例文件不可用（${name}）：${errorMessage(err)}`,
    )
  }
}

function asNumber(v: unknown, fallback: number): number {
  return typeof v === 'number' && Number.isFinite(v) ? v : fallback
}

export function createFixtureClient(options: FixtureUpstreamOptions = {}): UpstreamClient {
  // env.newapiFixtureDir 为「空 = 仓库根」的语义，故用 ||（空字符串要退到 REPO_ROOT）
  const dir = options.dir || env.newapiFixtureDir || REPO_ROOT

  /** 仿真约定：错误分支由 key 内容触发 */
  function simulate(key: string): void {
    const k = key.toLowerCase()
    if (k.includes('reject')) throw new UpstreamError('key_rejected', 'fixture：模拟上游拒绝该 key（401）', 401)
    if (k.includes('forbidden')) throw new UpstreamError('key_rejected', 'fixture：模拟账号被封禁（403）', 403)
    if (k.includes('unavailable')) {
      throw new UpstreamError('upstream_unavailable', 'fixture：模拟上游不可达（网络故障）')
    }
  }

  function loadLogs(): UpstreamLogRecord[] {
    const snap = readSnapshot<{ data?: UpstreamLogRecord[] }>(dir, 'api.log.token.json')
    if (!Array.isArray(snap.data)) {
      throw new UpstreamError('upstream_unavailable', '样例文件结构异常（api.log.token.json 缺 data[]）')
    }
    return snap.data
  }

  return {
    async fetchTokenUsage(plainKey: string): Promise<UpstreamTokenUsage> {
      simulate(plainKey)
      const first = loadLogs()[0]
      let other: Record<string, unknown> = {}
      if (first?.other) {
        try {
          other = JSON.parse(first.other) as Record<string, unknown>
        } catch {
          other = {} // 样例 other 解析失败不致命：退到兜底值
        }
      }
      const totalGranted = asNumber(other.subscription_total, 800_000_000)
      const totalUsed = asNumber(other.subscription_used, 85_579_458)
      return {
        name: first?.token_name ?? 'fixture-token',
        total_granted: totalGranted,
        total_used: totalUsed,
        total_available: totalGranted - totalUsed,
        unlimited_quota: false,
        model_limits: {},
        model_limits_enabled: false,
        expires_at: 0, // 永不过期
      }
    },
    async fetchLogs(plainKey: string): Promise<UpstreamLogRecord[]> {
      simulate(plainKey)
      return loadLogs()
    },
    async fetchStatus(): Promise<UpstreamStatus> {
      const snap = readSnapshot<{ data?: Record<string, unknown> }>(dir, 'api.status.json')
      const data = snap.data
      if (!data || typeof data !== 'object') {
        throw new UpstreamError('upstream_unavailable', '样例文件结构异常（api.status.json 缺 data）')
      }
      return {
        ...data,
        quota_per_unit: asNumber(data.quota_per_unit, DEFAULT_QUOTA_PER_UNIT),
      } as UpstreamStatus
    },
  }
}