'use client'

import { useState, useCallback, useRef } from 'react'
import Link from 'next/link'
import { usePathname, useRouter, useSearchParams } from 'next/navigation'
import { cn } from '@/lib/utils'
import { StickyNote, Plus, Tag, Folder, ChevronDown, ChevronRight, GripVertical } from 'lucide-react'
import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from '@/components/ui/tooltip'
import { useNotebooks } from '@/context/notebooks-context'
import { useNotebookDrag } from '@/context/notebook-drag-context'
import { Button } from '@/components/ui/button'
import { CreateNotebookDialog } from './create-notebook-dialog'
import { NotebookActions } from './notebook-actions'
import { DeleteNotebookDialog } from './delete-notebook-dialog'
import { EditNotebookDialog } from './edit-notebook-dialog'
import { NotebookSummaryDialog } from './notebook-summary-dialog'
import { useLanguage } from '@/lib/i18n'
import { useLabels } from '@/context/LabelContext'
import { LabelManagementDialog } from '@/components/label-management-dialog'
import { Notebook } from '@/lib/types'
import { getNotebookIcon } from '@/lib/notebook-icon'

function NotebookName({ children }: { name: string; children: React.ReactNode }) {
  return (
    <span className="relative truncate min-w-0 group-hover:overflow-visible group-hover:text-nowrap">
      <span className="group-hover:font-bold group-hover:relative group-hover:z-20 group-hover:inline-block group-hover:bg-white dark:group-hover:bg-[#1e2128] group-hover:pr-4 group-hover:shadow-[4px_0_12px_8px] group-hover:shadow-white dark:group-hover:shadow-[#1e2128]">
        {children}
      </span>
    </span>
  )
}

export function NotebooksList() {
  const pathname = usePathname()
  const searchParams = useSearchParams()
  const router = useRouter()
  const { t, language } = useLanguage()
  const { notebooks, currentNotebook, deleteNotebook, moveNoteToNotebookOptimistic, updateNotebookOrderOptimistic, isLoading } = useNotebooks()
  const { draggedNoteId, dragOverNotebookId, dragOver } = useNotebookDrag()
  const { labels } = useLabels()

  const [isCreateDialogOpen, setIsCreateDialogOpen] = useState(false)
  const [editingNotebook, setEditingNotebook] = useState<Notebook | null>(null)
  const [deletingNotebook, setDeletingNotebook] = useState<Notebook | null>(null)
  const [summaryNotebook, setSummaryNotebook] = useState<Notebook | null>(null)
  const [expandedNotebook, setExpandedNotebook] = useState<string | null>(null)
  const [labelsDialogOpen, setLabelsDialogOpen] = useState(false)

  // ── Notebook reorder drag state ──
  const draggingNbRef = useRef<string | null>(null)
  const [draggingNbId, setDraggingNbId] = useState<string | null>(null)
  const [overNbId, setOverNbId] = useState<string | null>(null)

  const currentNotebookId = searchParams.get('notebook')

  // Handle drop on a notebook (note-to-notebook OR notebook reorder)
  const handleDrop = useCallback(async (e: React.DragEvent, notebookId: string | null) => {
    e.preventDefault()
    e.stopPropagation()

    const sourceNbId = e.dataTransfer.getData('application/x-notebook')
    const noteId = e.dataTransfer.getData('text/plain')

    if (sourceNbId && notebookId && sourceNbId !== notebookId) {
      // ── Reorder notebooks ──
      const currentIds = notebooks.map((nb: Notebook) => nb.id)
      const fromIdx = currentIds.indexOf(sourceNbId)
      const toIdx = currentIds.indexOf(notebookId)
      if (fromIdx !== -1 && toIdx !== -1) {
        const newIds = [...currentIds]
        newIds.splice(fromIdx, 1)
        newIds.splice(toIdx, 0, sourceNbId)
        await updateNotebookOrderOptimistic(newIds)
      }
    } else if (noteId) {
      // ── Move note to notebook ──
      await moveNoteToNotebookOptimistic(noteId, notebookId)
    }

    dragOver(null)
    draggingNbRef.current = null
    setDraggingNbId(null)
    setOverNbId(null)
  }, [notebooks, moveNoteToNotebookOptimistic, updateNotebookOrderOptimistic, dragOver])

  // Handle drag over a notebook
  const handleDragOver = useCallback((e: React.DragEvent, notebookId: string | null) => {
    e.preventDefault()
    if (draggingNbRef.current) {
      // Notebook reorder mode — just track the insertion target
      setOverNbId(notebookId)
    } else {
      // Note-to-notebook mode
      dragOver(notebookId)
    }
  }, [dragOver])

  // Handle drag leave
  const handleDragLeave = useCallback(() => {
    if (draggingNbRef.current) {
      setOverNbId(null)
    } else {
      dragOver(null)
    }
  }, [dragOver])

  // ── Notebook reorder handlers ──
  const handleNotebookDragStart = useCallback((e: React.DragEvent, notebookId: string) => {
    e.dataTransfer.setData('application/x-notebook', notebookId)
    e.dataTransfer.effectAllowed = 'move'
    draggingNbRef.current = notebookId
    // Slight delay so the drag ghost renders before opacity change
    setTimeout(() => setDraggingNbId(notebookId), 0)
  }, [])

  const handleNotebookDragEnd = useCallback(() => {
    draggingNbRef.current = null
    setDraggingNbId(null)
    setOverNbId(null)
    dragOver(null)
  }, [dragOver])

  const handleSelectNotebook = (notebookId: string | null) => {
    const params = new URLSearchParams(searchParams)

    if (notebookId) {
      params.set('notebook', notebookId)
    } else {
      params.delete('notebook')
    }

    // Clear other filters
    params.delete('labels')
    params.delete('search')

    router.push(`/?${params.toString()}`)
  }

  const handleToggleExpand = (notebookId: string) => {
    setExpandedNotebook((prev) => (prev === notebookId ? null : notebookId))
  }

  const handleLabelFilter = (labelName: string, notebookId: string) => {
    const params = new URLSearchParams(searchParams)
    const currentLabels = params.get('labels')?.split(',').filter(Boolean) || []

    if (currentLabels.includes(labelName)) {
      params.set('labels', currentLabels.filter((l: string) => l !== labelName).join(','))
    } else {
      params.set('labels', [...currentLabels, labelName].join(','))
    }

    params.set('notebook', notebookId)
    router.push(`/?${params.toString()}`)
  }

  if (isLoading) {
    return (
      <div className="my-2">
        <div className="px-4 py-2">
          <div className="text-xs text-gray-500">{t('common.loading')}</div>
        </div>
      </div>
    )
  }

  return (
    <>
      <LabelManagementDialog open={labelsDialogOpen} onOpenChange={setLabelsDialogOpen} />
      <div className="flex flex-col pt-1">
        {/* Header with Add Button */}
        <div className="group mt-1 flex cursor-pointer items-center justify-between px-3 py-2 text-muted-foreground hover:text-foreground">
          <span className="text-xs font-semibold uppercase tracking-wider">{t('nav.notebooks') || 'NOTEBOOKS'}</span>
          <button
            onClick={() => setIsCreateDialogOpen(true)}
            className="p-1 hover:bg-gray-200 dark:hover:bg-gray-700 rounded-full transition-colors"
            title={t('notebooks.create') || 'Create notebook'}
          >
            <Plus className="w-4 h-4" />
          </button>
        </div>

        {/* Notebooks Loop */}
        {notebooks.map((notebook: Notebook) => {
          const isActive = currentNotebookId === notebook.id
          const isExpanded = expandedNotebook === notebook.id
          const isDragOver = dragOverNotebookId === notebook.id

          // Get icon component
          const NotebookIcon = getNotebookIcon(notebook.icon || 'folder')

          return (
            <div
              key={notebook.id}
              className={cn(
                "group flex flex-col transition-opacity duration-150",
                draggingNbId === notebook.id && "opacity-40"
              )}
              draggable
              onDragStart={(e) => handleNotebookDragStart(e, notebook.id)}
              onDragEnd={handleNotebookDragEnd}
            >
              {/* Insertion indicator above this notebook when reordering */}
              {overNbId === notebook.id && draggingNbId !== notebook.id && (
                <div className="h-0.5 bg-primary/70 mx-4 rounded-full mb-0.5 transition-all" />
              )}
              {isActive ? (
                // Active notebook with expanded labels
                <div
                  onDrop={(e) => handleDrop(e, notebook.id)}
                  onDragOver={(e) => handleDragOver(e, notebook.id)}
                  onDragLeave={handleDragLeave}
                  className={cn(
                    "flex flex-col me-2 rounded-e-full transition-all relative",
                    !notebook.color && "bg-primary/10 dark:bg-primary/20",
                    isDragOver && "ring-2 ring-primary ring-dashed"
                  )}
                  style={notebook.color ? { backgroundColor: `${notebook.color}20` } : undefined}
                >
                  {/* Header */}
                  <div className="pointer-events-auto flex items-center justify-between px-3 py-3">
                    <div className="flex items-center gap-4 min-w-0 flex-1">
                      <NotebookIcon
                        className={cn("w-5 h-5 flex-shrink-0 fill-current", !notebook.color && "text-primary dark:text-primary-foreground")}
                        style={notebook.color ? { color: notebook.color } : undefined}
                      />
                      <NotebookName name={notebook.name}>
                        <span
                          className={cn("text-[15px] font-medium tracking-wide", !notebook.color && "text-primary dark:text-primary-foreground")}
                          style={notebook.color ? { color: notebook.color } : undefined}
                        >
                          {notebook.name}
                        </span>
                      </NotebookName>
                    </div>
                    <div className="flex items-center gap-1 flex-shrink-0">
                      {/* Actions menu for active notebook */}
                      <NotebookActions
                        notebook={notebook}
                        onEdit={() => setEditingNotebook(notebook)}
                        onDelete={() => setDeletingNotebook(notebook)}
                        onSummary={() => setSummaryNotebook(notebook)}
                      />
                      <button
                        type="button"
                        onClick={(e) => {
                          e.stopPropagation()
                          handleToggleExpand(notebook.id)
                        }}
                        className={cn(
                          "shrink-0 rounded-full p-1 transition-colors",
                          !notebook.color &&
                            "text-primary hover:text-primary/80 dark:text-primary-foreground dark:hover:text-primary-foreground/80"
                        )}
                        style={notebook.color ? { color: notebook.color } : undefined}
                        aria-expanded={isExpanded}
                      >
                        <ChevronDown className={cn("h-4 w-4 transition-transform", isExpanded && "rotate-180")} />
                      </button>
                    </div>
                  </div>

                  {/* Contextual Labels Tree */}
                  {isExpanded && (
                    <div className="flex flex-col pb-2">
                      {labels.length === 0 ? (
                        <p className="pointer-events-none ps-12 pe-4 py-2 text-xs text-muted-foreground">
                          {t('sidebar.noLabelsInNotebook')}
                        </p>
                      ) : (
                        labels.map((label: any) => (
                          <button
                            key={label.id}
                            type="button"
                            onClick={() => handleLabelFilter(label.name, notebook.id)}
                            className={cn(
                              'pointer-events-auto flex items-center gap-4 ps-12 pe-4 py-2 rounded-e-full me-2 transition-colors',
                              'hover:bg-accent/60 text-muted-foreground hover:text-foreground',
                              searchParams.get('labels')?.includes(label.name) &&
                                'font-semibold text-foreground'
                            )}
                          >
                            <Tag className="h-4 w-4 shrink-0" />
                            <span className="text-xs font-medium truncate">{label.name}</span>
                          </button>
                        ))
                      )}
                      <button
                        type="button"
                        onClick={() => setLabelsDialogOpen(true)}
                        className="pointer-events-auto flex items-center gap-2 ps-12 pe-4 py-2 mt-1 rounded-e-full me-2 transition-colors text-muted-foreground hover:text-foreground hover:bg-accent/60 group/label"
                      >
                        <Plus className="h-3 w-3 shrink-0 group-hover/label:scale-110 transition-transform" />
                        <span className="text-xs font-medium">{t('sidebar.editLabels')}</span>
                      </button>
                    </div>
                  )}
                </div>
              ) : (
                // Inactive notebook
                <div
                  onDrop={(e) => handleDrop(e, notebook.id)}
                  onDragOver={(e) => handleDragOver(e, notebook.id)}
                  onDragLeave={handleDragLeave}
                  className={cn(
                    "flex items-center relative",
                    isDragOver && "ring-2 ring-primary ring-dashed rounded-e-full me-2"
                  )}
                >
                  <TooltipProvider delayDuration={600}>
                    <Tooltip>
                      <TooltipTrigger asChild>
                        <button
                          onClick={() => handleSelectNotebook(notebook.id)}
                          className={cn(
                            "pointer-events-auto flex items-center gap-3 px-4 py-3 rounded-e-full me-2 text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-gray-800/50 transition-colors w-full pe-14",
                            isDragOver && "opacity-50"
                          )}
                        >
                          <GripVertical className="w-3.5 h-3.5 flex-shrink-0 text-gray-300 dark:text-gray-600 opacity-0 group-hover:opacity-100 transition-opacity cursor-grab active:cursor-grabbing" />
                          <NotebookIcon className="w-5 h-5 flex-shrink-0" />
                          <span className="text-[15px] font-medium tracking-wide text-start truncate min-w-0 flex-1">
                            {notebook.name}
                          </span>
                          {(notebook as any).notesCount > 0 && (
                            <span className="text-xs text-gray-400 ms-auto flex-shrink-0">({new Intl.NumberFormat(language).format((notebook as any).notesCount)})</span>
                          )}
                        </button>
                      </TooltipTrigger>
                      <TooltipContent side="right" className="text-sm font-medium">
                        {notebook.name}
                      </TooltipContent>
                    </Tooltip>
                  </TooltipProvider>

                  {/* Actions + expand on the right — always rendered, visible on hover */}
                  <div className="absolute end-3 top-1/2 -translate-y-1/2 flex items-center gap-1 opacity-0 group-hover:opacity-100 transition-opacity z-10">
                    <NotebookActions
                      notebook={notebook}
                      onEdit={() => setEditingNotebook(notebook)}
                      onDelete={() => setDeletingNotebook(notebook)}
                      onSummary={() => setSummaryNotebook(notebook)}
                    />
                    <button
                      onClick={(e) => { e.stopPropagation(); handleToggleExpand(notebook.id); }}
                      className={cn(
                        "p-1 text-gray-400 hover:text-gray-600 dark:hover:text-gray-200 transition-colors rounded-full hover:bg-gray-200 dark:hover:bg-gray-700",
                        expandedNotebook === notebook.id && "rotate-180"
                      )}
                    >
                      <ChevronDown className="w-4 h-4" />
                    </button>
                  </div>
                </div>
              )}
            </div>
          )
        })}
      </div>

      {/* Create Notebook Dialog */}
      <CreateNotebookDialog
        open={isCreateDialogOpen}
        onOpenChange={setIsCreateDialogOpen}
      />

      {/* Edit Notebook Dialog */}
      {editingNotebook && (
        <EditNotebookDialog
          notebook={editingNotebook}
          open={!!editingNotebook}
          onOpenChange={(open) => {
            if (!open) setEditingNotebook(null)
          }}
        />
      )}

      {/* Delete Confirmation Dialog */}
      {deletingNotebook && (
        <DeleteNotebookDialog
          notebook={deletingNotebook}
          open={!!deletingNotebook}
          onOpenChange={(open) => {
            if (!open) setDeletingNotebook(null)
          }}
        />
      )}

      {/* Notebook Summary Dialog */}
      <NotebookSummaryDialog
        open={!!summaryNotebook}
        onOpenChange={(open) => {
          if (!open) setSummaryNotebook(null)
        }}
        notebookId={summaryNotebook?.id ?? null}
        notebookName={summaryNotebook?.name}
      />
    </>
  )
}