import { useState, useCallback, useRef, useEffect } from 'react'
import { sendChatMessage } from '../api/chat.js'
import { parseSsePayload } from '../utils/sse.js'
import { loadMessagesFromApi } from '../api/conversations.js'

export function useMessages({ activeId, refreshConversations }) {
  const [messages, setMessages] = useState([])
  const [isThinking, setIsThinking] = useState(false)
  const [statusText, setStatusText] = useState('')
  const bottomRef = useRef(null)

  const chunkedHistory = (msgs) =>
    msgs.map((msg) => ({ role: msg.role, content: msg.content }))

  // Load messages from API when active conversation changes
  useEffect(() => {
    if (!activeId) return
    let cancelled = false
    loadMessagesFromApi(activeId).then((data) => {
      if (!cancelled) setMessages(data)
    })
    return () => {
      cancelled = true
    }
  }, [activeId])

  const sendMessage = useCallback(async ({
    inputValue,
    uploadedImage,
    imageAnalysis,
    imageUrl,
    selectedTools,
    selectedDocuments,
    useRag,
    setInputValue,
    clearImageState,
    setShowTools,
  }) => {
    const trimmed = inputValue.trim()
    if ((!trimmed && !uploadedImage) || !activeId) return

    const history = chunkedHistory(messages)

    let messageContent = trimmed || (uploadedImage ? 'Please analyze the attached image' : '')

    const userMsg = {
      id: `user-${Date.now()}`,
      role: 'user',
      content: messageContent,
      ...(uploadedImage ? { image: uploadedImage, image_url: imageUrl } : {}),
    }
    setMessages((prev) => [...prev, userMsg, { id: `assistant-${Date.now()}`, role: 'assistant', content: '' }])

    setInputValue('')
    clearImageState()
    setIsThinking(true)
    setStatusText('Thinking...')
    setShowTools(false)

    try {
      const reader = await sendChatMessage({
        message: messageContent,
        history,
        conversationId: activeId,
        toolNames: selectedTools,
        documentIds: selectedDocuments,
        useRag,
        imageUrl,
        imageAnalysis,
      })

      const decoder = new TextDecoder()
      let buffer = ''
      let receivedAnyEvent = false

      // Track whether timeout has fired — if so, the readLoop is still running
      // and will populate the message naturally when chunks arrive.
      let slowResponse = false

      // 90-second timeout: show friendly status instead of replacing message with "Error:"
      const SLOW_MS = 90000
      const slowTimer = setTimeout(() => {
        slowResponse = true
        setStatusText(receivedAnyEvent
          ? 'Still working on it...'
          : 'Waiting for the response...')

        // Safety net: if still no data after another 2 minutes, show fallback text
        setTimeout(() => {
          setMessages((prev) => {
            const lastIndex = prev.length - 1
            return prev.map((m, i) =>
              i === lastIndex && m.role === 'assistant' && m.content === ''
                ? { ...m, content: 'The server did not respond. Please try again.' }
                : m,
            )
          })
          setIsThinking(false)
          setStatusText('')
        }, 120000)
      }, SLOW_MS)

      const readLoop = (async () => {
        while (true) {
          const { value, done } = await reader.read()
          if (done) break
          receivedAnyEvent = true
          buffer += decoder.decode(value, { stream: true })
          const parts = buffer.split('\n\n')
          buffer = parts.pop() || ''

          for (const part of parts) {
            if (!part.trim()) continue
            const { event, data } = parseSsePayload(part)
            let payload = {}
            try {
              payload = JSON.parse(data)
            } catch {
              payload = { text: data }
            }

            if (event === 'status') {
              setStatusText(payload.state || 'Thinking...')
            }

            if (event === 'tool') {
              setStatusText(`Using tool: ${payload.tool || 'tool'}`)
            }

            if (event === 'chunk') {
              // If timeout previously fired, update status so user sees progress
              if (slowResponse) {
                setStatusText('Receiving response...')
              }
              setMessages((prev) => {
                const lastIndex = prev.length - 1
                const content = prev[lastIndex]?.content || ''
                return prev.map((m, i) =>
                  i === lastIndex && m.role === 'assistant'
                    ? { ...m, content: `${content}${payload.text || ''}` }
                    : m,
                )
              })
            }

            if (event === 'done') {
              clearTimeout(slowTimer)
              setIsThinking(false)
              setStatusText('')
              refreshConversations()
            }
          }
        }
      })()

      await readLoop
    } catch (error) {
      // Only catch genuine errors (network failure, server error) — not timeout
      setMessages((prev) =>
        prev.map((m) =>
          m.role === 'assistant' && m.content === ''
            ? { ...m, content: `${error.message}` }
            : m,
        ),
      )
      setIsThinking(false)
      setStatusText('')
    }
  }, [activeId, messages, refreshConversations])

  return {
    messages,
    setMessages,
    isThinking,
    setIsThinking,
    statusText,
    setStatusText,
    bottomRef,
    sendMessage,
  }
}