import { processDataStream } from 'ai'

export type MessagePartType = 'text' | 'reasoning' | 'tool-call' | 'tool-result'

export interface MessagePart {
  id: string
  type: MessagePartType
  text?: string
  toolName?: string
  toolCallId?: string
  args?: unknown
  result?: unknown
  state?: 'call' | 'result'
  reasoningLoading?: boolean
  reasoningDuration?: number
}

export interface LlmChatMessage {
  id: string
  role: 'user' | 'assistant'
  content: string
  parts?: MessagePart[]
}

export interface UseLlmChatOptions {
  modelId: () => number | null
  apiEndpoint?: string
  systemPrompt?: () => string
  enableThinking?: () => boolean
  enableTools?: () => boolean
}

export function useLlmChat(options: UseLlmChatOptions) {
  const {
    modelId,
    apiEndpoint = '/api/llm/chat',
    systemPrompt,
    enableThinking,
    enableTools,
  } = options

  const messages = ref<LlmChatMessage[]>([])
  const isLoading = ref(false)
  const errorMessage = ref('')

  let abortController: AbortController | null = null

  function generateId(): string {
    return Date.now().toString(36) + Math.random().toString(36).slice(2)
  }

  function getOrCreateLastPart(msg: LlmChatMessage, type: MessagePartType): MessagePart | null {
    if (!msg.parts) msg.parts = []
    const last = msg.parts[msg.parts.length - 1]
    if (last && last.type === type) return last
    return null
  }

  function appendPart(msg: LlmChatMessage, part: MessagePart) {
    if (!msg.parts) msg.parts = []
    msg.parts.push(part)
  }

  function updateLastReasoningDuration(msg: LlmChatMessage) {
    if (!msg.parts) return
    for (let i = msg.parts.length - 1; i >= 0; i--) {
      const p = msg.parts[i]
      if (!p) continue
      if (p.type === 'reasoning' && p.reasoningLoading) {
        p.reasoningLoading = false
        return
      }
    }
  }

  async function sendMessage(text: string) {
    const trimmed = text.trim()
    const mid = modelId()
    if (!trimmed || mid === null || isLoading.value) return

    errorMessage.value = ''

    const userMsg: LlmChatMessage = { id: generateId(), role: 'user', content: trimmed }
    messages.value.push(userMsg)

    const assistantMsg: LlmChatMessage = {
      id: generateId(),
      role: 'assistant',
      content: '',
      parts: [],
    }
    messages.value.push(assistantMsg)
    const assistantIdx = messages.value.length - 1

    isLoading.value = true
    abortController = new AbortController()

    let reasoningStartTime: number | null = null

    try {
      const res = await fetch(apiEndpoint, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          modelId: mid,
          messages: [
            ...(systemPrompt?.() ? [{ role: 'system' as const, content: systemPrompt() }] : []),
            ...messages.value
              .filter(m => m.content)
              .map(m => ({ role: m.role, content: m.content })),
          ],
          enableThinking: enableThinking?.() ?? false,
          enableTools: enableTools?.() ?? false,
        }),
        signal: abortController.signal,
      })

      if (!res.ok) {
        const errText = await res.text()
        throw new Error(errText || `请求失败 (${res.status})`)
      }

      if (!res.body) {
        throw new Error('响应体为空')
      }

      await processDataStream({
        stream: res.body,
        onReasoningPart: (text) => {
          const msg = messages.value[assistantIdx]
          if (!msg) return
          let part = getOrCreateLastPart(msg, 'reasoning')
          if (!part) {
            if (reasoningStartTime === null) reasoningStartTime = Date.now()
            part = { id: generateId(), type: 'reasoning', text: '', reasoningLoading: true }
            appendPart(msg, part)
          }
          part.text = (part.text ?? '') + text
        },
        onTextPart: (text) => {
          const msg = messages.value[assistantIdx]
          if (!msg) return
          updateLastReasoningDuration(msg)
          let part = getOrCreateLastPart(msg, 'text')
          if (!part) {
            part = { id: generateId(), type: 'text', text: '' }
            appendPart(msg, part)
          }
          part.text = (part.text ?? '') + text
          msg.content += text
        },
        onErrorPart: (error) => {
          errorMessage.value = error || '流式响应出错'
        },
        onToolCallPart: (part) => {
          const msg = messages.value[assistantIdx]
          if (!msg) return
          updateLastReasoningDuration(msg)
          appendPart(msg, {
            id: generateId(),
            type: 'tool-call',
            toolName: part.toolName,
            toolCallId: part.toolCallId,
            args: part.args,
            state: 'call',
          })
        },
        onToolResultPart: (part) => {
          const msg = messages.value[assistantIdx]
          if (!msg || !msg.parts) return
          const callPart = msg.parts.find(p => p.type === 'tool-call' && p.toolCallId === part.toolCallId)
          if (callPart) {
            callPart.result = part.result
            callPart.state = 'result'
          }
        },
      })

      const msg = messages.value[assistantIdx]
      if (msg) updateLastReasoningDuration(msg)

      // 检查是否有实际内容产出
      const finalMsg = messages.value[assistantIdx]
      if (finalMsg && !errorMessage.value) {
        const hasText = finalMsg.parts?.some(p => p.type === 'text' && p.text)
        const hasToolCall = finalMsg.parts?.some(p => p.type === 'tool-call')
        if (!hasText && !hasToolCall) {
          // 完全无内容，移除空消息
          errorMessage.value = '模型未返回任何内容（可能已达到工具调用次数上限或模型无响应）'
          messages.value.splice(assistantIdx, 1)
        } else if (!hasText && hasToolCall) {
          // 有工具调用但无最终文本回答（maxSteps 用完），保留工具记录，追加提示
          finalMsg.parts?.push({
            id: generateId(),
            type: 'text',
            text: '（已达到工具调用次数上限，模型未能生成最终回答。以上是工具调用的尝试记录。）',
          })
        }
      }
    } catch (err: any) {
      if (err.name === 'AbortError') {
        // user stopped
      } else {
        errorMessage.value = err.message || '请求失败'
        const msg = messages.value[assistantIdx]
        if (msg && !msg.content && (!msg.parts || msg.parts.length === 0)) {
          messages.value.splice(assistantIdx, 1)
        }
      }
    } finally {
      isLoading.value = false
      abortController = null
    }
  }

  function stopGeneration() {
    if (abortController) {
      abortController.abort()
      abortController = null
    }
  }

  function clearChat() {
    messages.value = []
    errorMessage.value = ''
  }

  return {
    messages,
    isLoading,
    errorMessage,
    sendMessage,
    stopGeneration,
    clearChat,
  }
}