"use client"

import { useState, useEffect, useRef, useCallback } from "react"
import { getKnowledgeGraphDataAction } from "../actions"
import type { GraphViewMode, KnowledgeGraphData } from "../types"

interface UseGraphDataResult {
  data: KnowledgeGraphData | null
  isLoading: boolean
  error: string | null
  reload: () => void
}

/**
 * 图谱数据加载 Hook。
 *
 * 按 textbookId + viewMode 加载，切换 viewMode 时重新加载。
 * 使用派生值模式（isLoading 从 data.viewMode 派生），避免 effect 中同步 setState。
 */
export function useGraphData(
  textbookId: string,
  viewMode: GraphViewMode,
): UseGraphDataResult {
  const [data, setData] = useState<KnowledgeGraphData | null>(null)
  const [error, setError] = useState<string | null>(null)
  const [reloadTrigger, setReloadTrigger] = useState(0)
  const lastRequestKey = useRef<string>("")

  const reload = useCallback(() => {
    setReloadTrigger((n) => n + 1)
  }, [])

  // 派生 loading 状态：无数据或当前数据不匹配请求的 viewMode
  const isLoading = data === null || data.viewMode !== viewMode

  useEffect(() => {
    if (!textbookId) return

    const requestKey = `${textbookId}:${viewMode}:${reloadTrigger}`
    if (lastRequestKey.current === requestKey) return
    lastRequestKey.current = requestKey

    let cancelled = false

    getKnowledgeGraphDataAction(textbookId, viewMode)
      .then((result) => {
        if (cancelled) return
        if (result.success && result.data) {
          setData(result.data)
          setError(null)
        } else {
          setData(null)
          setError(result.message ?? "Unknown error")
        }
      })
      .catch((e: unknown) => {
        if (!cancelled) {
          setData(null)
          setError(e instanceof Error ? e.message : "Unknown error")
        }
      })

    return () => {
      cancelled = true
    }
  }, [textbookId, viewMode, reloadTrigger])

  return { data, isLoading, error, reload }
}