function contentText(payload) {
  return payload?.content?.map((part) => part.text || '').join('') || ''
}

function parseJson(text) {
  const cleaned = text.replace(/^```(?:json)?/i, '').replace(/```$/, '').trim()
  return JSON.parse(cleaned)
}

export async function deepseek(system, user, jsonOrOptions = false) {
  const options = typeof jsonOrOptions === 'boolean'
    ? { json: jsonOrOptions }
    : { ...(jsonOrOptions || {}) }
  const json = Boolean(options.json)
  const apiKey = process.env.DEEPSEEK_API_KEY
  if (!apiKey) throw Object.assign(new Error('DEEPSEEK_API_KEY 尚未配置'), { status: 503 })
  const endpoint = `${(process.env.DEEPSEEK_BASE_URL || 'https://api.deepseek.com/anthropic').replace(/\/$/, '')}/v1/messages`
  const attempts = json ? 2 : 1
  let prompt = user
  let lastError

  for (let attempt = 0; attempt < attempts; attempt += 1) {
    const controller = new AbortController()
    const timeout = setTimeout(
      () => controller.abort(),
      Number(options.timeoutMs || process.env.AI_TIMEOUT_MS || 30000),
    )
    try {
      const response = await fetch(endpoint, {
        method: 'POST',
        signal: controller.signal,
        headers: {
          'content-type': 'application/json',
          'x-api-key': apiKey,
          'anthropic-version': '2023-06-01',
        },
        body: JSON.stringify({
          model: process.env.DEEPSEEK_MODEL || 'deepseek-v4-flash',
          max_tokens: Number(options.maxTokens || process.env.AI_MAX_TOKENS || 4096),
          temperature: options.temperature ?? (json ? 0 : 0.3),
          thinking: options.thinking === true
            ? { type: 'enabled' }
            : { type: 'disabled' },
          system,
          messages: [{ role: 'user', content: [{ type: 'text', text: prompt }] }],
        }),
      })
      const body = await response.json()
      if (!response.ok) {
        throw Object.assign(new Error(body?.error?.message || `AI 请求失败 (${response.status})`), { status: 502 })
      }
      const text = contentText(body)
      if (!json) return text
      try {
        return parseJson(text)
      } catch (error) {
        lastError = error
        prompt = `${user}\n\n上一次响应不是合法 JSON。请重新生成完整结果：只允许输出一个可被 JSON.parse 直接解析的 JSON 值；不得使用 Markdown；字符串中的双引号、换行和反斜杠必须正确转义。`
      }
    } catch (error) {
      if (error?.name === 'AbortError') {
        throw Object.assign(new Error('AI 响应超时，请稍后重试'), { status: 504 })
      }
      throw error
    } finally {
      clearTimeout(timeout)
    }
  }
  throw Object.assign(new Error('AI 返回格式异常，自动重试后仍无法解析'), { status: 502, cause: lastError })
}

export function conversationContext(messages, limit = 30) {
  return messages.slice(-limit).map((m) => {
    const role = m.sender === 'agent' ? '我方' : m.sender === 'system' ? '系统' : '对方'
    const content = m.originalText || m.attachmentName || `[${m.type || '消息'}]`
    const translation = m.translatedText && m.translatedText !== content ? `（译文：${m.translatedText}）` : ''
    return `${m.createdAt || ''} ${role}: ${content}${translation}`
  }).join('\n')
}