import { create } from 'zustand'
import { toOpenAITools } from '../utils/tools'
import { safeCalc } from '../utils/calc'

const STEP_LIMIT = 6
const TIMEOUT_MS = 120000
const DEFAULT_MODEL = 'nvidia/nemotron-3-ultra-550b-a55b:free'

/* ------------------------------------------------------------------ *
 * 工具執行
 * ------------------------------------------------------------------ */
function executeTool(call) {
  const name = call?.function?.name
  let args
  try {
    args = JSON.parse(call?.function?.arguments || '{}')
  } catch {
    return '工具參數不是合法 JSON'
  }

  switch (name) {
    case 'search_web':
      return `【search_web】已查詢「${args.query}」。` +
        '（純前端環境沒有網路存取權限，此為模擬回應；要真的搜尋需改接後端服務）'
    case 'calculate':
      return safeCalc(args.expression)
    default:
      return `【${name || '未知工具'}】此環境未實作，收到參數 ${JSON.stringify(args)}`
  }
}

/* ------------------------------------------------------------------ *
 * 前置檢查與單一請求
 * ------------------------------------------------------------------ */
function validateConfig(apiConfig) {
  if (!apiConfig) return '尚未設定 API 連線'
  if (!apiConfig.apiKey?.trim()) return '尚未設定 API Key（請先開「設定」填入）'
  if (!apiConfig.supplier?.trim()) return '尚未設定 API URL'
  if (!apiConfig.model?.trim()) return '尚未設定 Model 名稱'
  return ''
}

async function requestCompletion(messages, toolsList, apiConfig) {
  const base = String(apiConfig.supplier).replace(/\/+$/, '')
  const controller = new AbortController()
  const timer = setTimeout(() => controller.abort(), TIMEOUT_MS)

  try {
    const res = await fetch(`${base}/chat/completions`, {
      method: 'POST',
      signal: controller.signal,
      headers: {
        Authorization: `Bearer ${apiConfig.apiKey.trim()}`,
        'Content-Type': 'application/json',
        'HTTP-Referer': typeof window !== 'undefined' ? window.location.origin : 'https://agent-studio',
        'X-Title': 'Agent Studio',
      },
      body: JSON.stringify({
        model: apiConfig.model,
        messages,
        tools: toOpenAITools(toolsList),
        stream: false,
      }),
    })

    let data = null
    try { data = await res.json() } catch { /* 非 JSON 回應 */ }

    if (!res.ok) {
      const detail = data?.error?.message
        || data?.error?.data?.message
        || data?.message
        || (typeof data === 'string' ? data : '無錯誤訊息')
      return { ok: false, error: `API 錯誤 ${res.status}：${detail}` }
    }
    return { ok: true, data }
  } catch (e) {
    if (e.name === 'AbortError') {
      return { ok: false, error: `請求逾時（超過 ${TIMEOUT_MS / 1000} 秒未回應）` }
    }
    return { ok: false, error: `網路錯誤：${e.message}` }
  } finally {
    clearTimeout(timer)
  }
}

/* ------------------------------------------------------------------ *
 * Store
 * ------------------------------------------------------------------ */
export const useAgentStore = create((set, get) => ({
  messages: [],
  running: false,
  step: 0,
  error: '',

  reset() {
    if (get().running) return
    set({ messages: [], step: 0, error: '' })
  },

  async runAgent(input, toolsList, apiConfig, agent) {
    const preflight = validateConfig(apiConfig)
    if (preflight) {
      set({ error: preflight })
      return { ok: false, error: preflight }
    }
    if (get().running) {
      set({ error: '已有任務正在執行，請稍候或清空對話' })
      return { ok: false, error: 'running' }
    }

    // system prompt 每輪重設，歷史訊息保留
    const history = get().messages.filter((m) => m.role !== 'system')
    const seed = agent?.systemPrompt
      ? [{ role: 'system', content: agent.systemPrompt }, ...history]
      : history

    set({ running: true, error: '', step: 0 })
    const userMsg = { role: 'user', content: input }
    set((s) => ({ messages: [...s.messages, userMsg] }))

    const messages = [...seed, userMsg]
    const add = (msg) => set((s) => ({ messages: [...s.messages, msg], error: '' }))

    for (let step = 1; step <= STEP_LIMIT; step++) {
      set({ step })

      const result = await requestCompletion(messages, toolsList, apiConfig)
      if (!result.ok) {
        add({ role: 'assistant', content: `⚠️ ${result.error}` })
        break
      }

      const message = result.data?.choices?.[0]?.message
      if (!message) {
        add({ role: 'assistant', content: '⚠️ API 回應格式異常（choices 為空）' })
        break
      }

      const assistantMsg = {
        role: 'assistant',
        content: message.content || '',
        tool_calls: message.tool_calls || [],
      }
      messages.push(assistantMsg)
      add(assistantMsg)

      const calls = assistantMsg.tool_calls
      if (calls.length === 0) break

      for (const call of calls) {
        const toolMsg = {
          role: 'tool',
          tool_call_id: call.id,
          name: call.function?.name,
          arguments: call.function?.arguments,
          content: executeTool(call),
        }
        messages.push(toolMsg)
        add(toolMsg)
      }
    }

    set({ running: false, step: 0 })
    return { ok: true }
  },
}))