/*
Copyright 2026 Arctel.net

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

"use client"

import {memo, useCallback, useEffect, useRef, useState} from "react"
import {useVirtualizer} from "@tanstack/react-virtual"
import {toast} from "sonner"
import {ArrowDown, ChevronUp, Loader2} from "lucide-react"

import services from "@/lib/services"
import {ErrorInline} from "@/components/layout/error"
import {LoadingStateWithBorder} from "@/components/layout/loading"
import {Button} from "@/components/ui/button"

interface LogEntry {
  index: number
  data: string
}

// Distance (px) from bottom to treat as "at bottom"
const BOTTOM_THRESHOLD = 40
const LOG_LINE_ESTIMATE_PX = 20
const LOG_VIRTUAL_OVERSCAN = 24

const LogLine = memo(function LogLine({data}: {data: string}) {
  const level = parseLogLevel(data)
  const color = level === "error"
    ? "text-red-400"
    : level === "warn"
      ? "text-yellow-400"
      : level === "debug"
        ? "text-gray-500"
        : "text-gray-300"

  return (
    <div className={`${color} whitespace-pre-wrap break-all px-2 py-0.5 rounded hover:bg-white/5`}>
      {data}
    </div>
  )
})

function getApiBaseUrl(): string {
  if (typeof window !== "undefined") {
    // If NEXT_PUBLIC_WAVELET_BACKEND_URL is set, use it. Otherwise, use origin.
    const base = process.env.NEXT_PUBLIC_WAVELET_BACKEND_URL || ""
    if (base.startsWith("http")) return base

    // Relative URL fallback
    const proto = window.location.protocol
    const host = window.location.host
    return `${proto}//${host}${base}`
  }
  return process.env.NEXT_PUBLIC_WAVELET_BACKEND_URL || ""
}

function buildWsUrl(): string {
  const base = getApiBaseUrl()
  const wsBase = base.replace(/^http/, "ws")
  return `${wsBase}/api/v1/admin/logs/ws`
}

function parseLogLevel(line: string): "debug" | "info" | "warn" | "error" | "unknown" {
  const lower = line.toLowerCase()
  if (lower.includes("\"level\":\"error\"") || lower.includes("level=error")) return "error"
  if (lower.includes("\"level\":\"warn\"") || lower.includes("level=warn")) return "warn"
  if (lower.includes("\"level\":\"debug\"") || lower.includes("level=debug")) return "debug"
  if (lower.includes("\"level\":\"info\"") || lower.includes("level=info")) return "info"
  return "unknown"
}

export function AppLogs() {
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<Error | null>(null)

  const [logs, setLogs] = useState<LogEntry[]>([])
  const [hasMore, setHasMore] = useState(false)
  const [nextCursor, setNextCursor] = useState(0)
  const [loadingMore, setLoadingMore] = useState(false)

  // autoScroll = true → new logs auto-scroll to bottom
  const [autoScroll, setAutoScroll] = useState(true)

  const containerRef = useRef<HTMLDivElement>(null)
  const wsRef = useRef<WebSocket | null>(null)
  const autoScrollRef = useRef(autoScroll)
  const isUserScrolling = useRef(false)

  useEffect(() => { autoScrollRef.current = autoScroll }, [autoScroll])

  const rowVirtualizer = useVirtualizer({
    count: logs.length,
    getScrollElement: () => containerRef.current,
    estimateSize: () => LOG_LINE_ESTIMATE_PX,
    overscan: LOG_VIRTUAL_OVERSCAN,
    measureElement: (element) => element.getBoundingClientRect().height,
  })

  // ---- Scroll detection ------------------------------------------------
  const handleScroll = useCallback(() => {
    const el = containerRef.current
    if (!el) return

    if (!isUserScrolling.current) return

    const atBottom = el.scrollHeight - el.scrollTop - el.clientHeight < BOTTOM_THRESHOLD
    if (atBottom && !autoScrollRef.current) {
      setAutoScroll(true)
    } else if (!atBottom && autoScrollRef.current) {
      setAutoScroll(false)
    }
  }, [])

  const handleWheel = useCallback(() => { isUserScrolling.current = true }, [])
  const handleTouchStart = useCallback(() => { isUserScrolling.current = true }, [])

  useEffect(() => {
    const el = containerRef.current
    if (!el) return

    let timer: ReturnType<typeof setTimeout>
    const onScrollEnd = () => {
      clearTimeout(timer)
      timer = setTimeout(() => { isUserScrolling.current = false }, 150)
    }
    el.addEventListener("scroll", onScrollEnd, { passive: true })
    return () => {
      el.removeEventListener("scroll", onScrollEnd)
      clearTimeout(timer)
    }
  }, [])

  // ---- Auto-scroll to bottom when new logs arrive ----------------------
  useEffect(() => {
    if (!autoScroll || !containerRef.current) return
    isUserScrolling.current = false
    const el = containerRef.current
    requestAnimationFrame(() => {
      el.scrollTop = el.scrollHeight
    })
  }, [logs, autoScroll])

  // ---- Data fetching ---------------------------------------------------
  const fetchLogs = useCallback(async (cursor: number = 0) => {
    try {
      return await services.adminLog.getLogs(cursor)
    } catch (err) {
      throw err instanceof Error ? err : new Error("获取日志失败")
    }
  }, [])

  const loadHistory = useCallback(async (cursor: number = 0) => {
    const isInitial = cursor === 0
    if (isInitial) {
      setLoading(true)
      setError(null)
    } else {
      setLoadingMore(true)
    }

    try {
      const data = await fetchLogs(cursor)
      if (isInitial) {
        setLogs(data.lines || [])
      } else {
        const el = containerRef.current
        const previousScrollHeight = el?.scrollHeight ?? 0
        setLogs(prev => [...(data.lines || []), ...prev])

        requestAnimationFrame(() => {
          if (!el) return
          isUserScrolling.current = false
          el.scrollTop = el.scrollHeight - previousScrollHeight
        })
      }
      setHasMore(data.has_more)
      setNextCursor(data.next_cursor)
    } catch (err) {
      if (isInitial) {
        setError(err instanceof Error ? err : new Error("获取日志失败"))
      } else {
        toast.error("加载更早日志失败")
      }
    } finally {
      if (isInitial) setLoading(false)
      else setLoadingMore(false)
    }
  }, [fetchLogs])

  // ---- WebSocket -------------------------------------------------------
  const connectWs = useCallback(() => {
    if (wsRef.current) wsRef.current.close()

    const ws = new WebSocket(buildWsUrl())
    wsRef.current = ws

    ws.onmessage = (event) => {
      try {
        const msg = JSON.parse(event.data)
        if (msg.type === "log" && msg.data) {
          const entry: LogEntry = msg.data
          setLogs(prev => {
            const next = [...prev, entry]
            return next.length > 2000 ? next.slice(-2000) : next
          })
        }
      } catch { /* ignore */ }
    }

    ws.onclose = () => { wsRef.current = null }
  }, [])

  // ---- Initialize ------------------------------------------------------
  useEffect(() => {
    loadHistory(0).then(() => connectWs())
    return () => {
      wsRef.current?.close()
      wsRef.current = null
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [])

  // ---- Actions ---------------------------------------------------------
  const scrollToBottom = useCallback(() => {
    setAutoScroll(true)
    requestAnimationFrame(() => {
      if (containerRef.current) {
        containerRef.current.scrollTop = containerRef.current.scrollHeight
      }
    })
  }, [])

  const handleLoadMore = useCallback(() => {
    if (nextCursor > 0) loadHistory(nextCursor)
  }, [nextCursor, loadHistory])

  // ---- Render ----------------------------------------------------------
  if (loading) return <LoadingStateWithBorder />
  if (error) return <ErrorInline error={error} onRetry={() => loadHistory(0)} />

  return (
    <div className="flex flex-col h-full relative">
      {/* Log viewer — fixed height, scrollable */}
      <div
        ref={containerRef}
        onScroll={handleScroll}
        onWheel={handleWheel}
        onTouchStart={handleTouchStart}
        className="h-[calc(100vh-270px)] overflow-y-auto overflow-x-hidden rounded-lg border border-border/40 bg-[#0d1117] font-mono text-[13px] leading-5 relative"
      >
        {/* Load older logs */}
        {hasMore && (
          <div className="sticky top-0 z-10 flex justify-center py-1.5 bg-[#0d1117]/90 backdrop-blur-sm">
            <Button
              variant="ghost"
              size="sm"
              onClick={handleLoadMore}
              disabled={loadingMore}
              className="text-muted-foreground hover:text-foreground h-7 text-xs"
            >
              {loadingMore
                ? <><Loader2 className="size-3 mr-1.5 animate-spin" />加载中...</>
                : <><ChevronUp className="size-3 mr-1.5" />加载更早日志</>
              }
            </Button>
          </div>
        )}

        {logs.length === 0 ? (
          <div className="px-4 py-8 text-center text-gray-500">暂无日志</div>
        ) : (
          <div
            className="relative px-3 py-3"
            style={{height: `${rowVirtualizer.getTotalSize()}px`}}
          >
            {rowVirtualizer.getVirtualItems().map((virtualRow) => {
              const entry = logs[virtualRow.index]
              if (!entry) return null

              return (
                <div
                  key={entry.index}
                  ref={rowVirtualizer.measureElement}
                  data-index={virtualRow.index}
                  className="absolute top-0 left-0 w-full"
                  style={{transform: `translateY(${virtualRow.start}px)`}}
                >
                  <LogLine data={entry.data} />
                </div>
              )
            })}
          </div>
        )}
      </div>

      {/* Floating "back to latest" button */}
      {!autoScroll && (
        <div className="absolute bottom-6 left-1/2 -translate-x-1/2 z-20">
          <Button
            variant="outline"
            size="sm"
            onClick={scrollToBottom}
            className="shadow-lg bg-background/80 backdrop-blur-sm border-border/50"
          >
            <ArrowDown className="size-3.5 mr-1.5" />
            回到最新
          </Button>
        </div>
      )}
    </div>
  )
}