'use client'

import { useState, useTransition } from 'react'
import { useRouter } from 'next/navigation'
import {
  DndContext,
  DragEndEvent,
  DragOverlay,
  DragStartEvent,
  KeyboardSensor,
  PointerSensor,
  useSensor,
  useSensors,
  closestCenter,
} from '@dnd-kit/core'
import {
  SortableContext,
  useSortable,
  rectSortingStrategy,
  arrayMove,
  sortableKeyboardCoordinates,
} from '@dnd-kit/sortable'
import { CSS } from '@dnd-kit/utilities'
import { toast } from 'sonner'
import { Badge } from '@/components/ui/badge'
import { Button } from '@/components/ui/button'
import { PanelNavBar } from '@/components/shared/panel-nav-bar'
import { DemoTooltip } from '@/components/shared/demo-tooltip'
import { useSelectionStore } from '@/stores/selection-store'
import { useBacklogStore, type BacklogTask } from '@/stores/backlog-store'
import { reorderTasksAction } from '@/actions/tasks'
import { BacklogCard } from './backlog-card'
import { EmptyPanel } from './empty-panel'
import { cn } from '@/lib/utils'

const STATUS_COLORS: Record<string, string> = {
  TO_DO: 'bg-status-todo/15 text-status-todo border-status-todo/30',
  IN_PROGRESS: 'bg-status-in-progress/15 text-status-in-progress border-status-in-progress/30',
  REVIEW: 'bg-status-review/15 text-status-review border-status-review/30',
  DONE: 'bg-status-done/15 text-status-done border-status-done/30',
}
const STATUS_LABELS: Record<string, string> = {
  TO_DO: 'To Do',
  IN_PROGRESS: 'Bezig',
  REVIEW: 'Review',
  DONE: 'Klaar',
}

function SortableTaskCard({
  task,
  isDemo,
  onClick,
}: {
  task: BacklogTask
  isDemo: boolean
  onClick: () => void
}) {
  const { attributes, listeners, setNodeRef, transform, transition, isDragging } =
    useSortable({ id: task.id })

  const style = {
    transform: CSS.Transform.toString(transform),
    transition,
  }

  return (
    <BacklogCard
      ref={setNodeRef}
      style={style}
      {...attributes}
      {...(isDemo ? {} : listeners)}
      title={task.title}
      priority={task.priority}
      isDragging={isDragging}
      onClick={onClick}
      badge={
        <Badge
          className={cn(
            'text-[10px] px-1.5 py-0 border',
            STATUS_COLORS[task.status] ?? STATUS_COLORS.TO_DO,
          )}
        >
          {STATUS_LABELS[task.status] ?? task.status}
        </Badge>
      }
    />
  )
}

interface TaskPanelProps {
  productId: string
  isDemo: boolean
  closePath: string
}

export function TaskPanel({ isDemo, closePath }: TaskPanelProps) {
  const router = useRouter()
  const [, startTransition] = useTransition()
  const selectedStoryId = useSelectionStore((s) => s.selectedStoryId)
  const tasksByStory = useBacklogStore((s) => s.tasksByStory)
  const [activeDragId, setActiveDragId] = useState<string | null>(null)
  const [localOrder, setLocalOrder] = useState<string[] | null>(null)

  const rawTasks = selectedStoryId ? (tasksByStory[selectedStoryId] ?? []) : null

  // Merge local order with rawTasks for optimistic reorder
  const tasks: BacklogTask[] | null = rawTasks === null
    ? null
    : localOrder
      ? localOrder.map((id) => rawTasks.find((t) => t.id === id)).filter(Boolean) as BacklogTask[]
      : rawTasks

  const sensors = useSensors(
    useSensor(PointerSensor, { activationConstraint: { distance: 5 } }),
    useSensor(KeyboardSensor, { coordinateGetter: sortableKeyboardCoordinates }),
  )

  function handleDragStart(event: DragStartEvent) {
    setActiveDragId(event.active.id as string)
  }

  function handleDragEnd(event: DragEndEvent) {
    setActiveDragId(null)
    if (!selectedStoryId || !tasks) return
    const { active, over } = event
    if (!over || active.id === over.id) return

    const ids = tasks.map((t) => t.id)
    const oldIndex = ids.indexOf(active.id as string)
    const newIndex = ids.indexOf(over.id as string)
    if (oldIndex === -1 || newIndex === -1) return

    const newOrder = arrayMove(ids, oldIndex, newIndex)
    setLocalOrder(newOrder)

    startTransition(async () => {
      const result = await reorderTasksAction(selectedStoryId, newOrder)
      if (result?.error) {
        setLocalOrder(null)
        toast.error(result.error)
      }
    })
  }

  const navActions = (
    <DemoTooltip show={isDemo}>
      <Button
        size="sm"
        className="h-7 text-xs"
        disabled={isDemo || !selectedStoryId}
        onClick={() => {
          if (!selectedStoryId) return
          router.push(`${closePath}?newTask=1&storyId=${selectedStoryId}`)
        }}
      >
        + Nieuwe taak
      </Button>
    </DemoTooltip>
  )

  if (tasks === null) {
    return (
      <div className="flex flex-col h-full">
        <PanelNavBar title="Taken" actions={navActions} />
        <EmptyPanel message="Selecteer een story om de taken te bekijken." />
      </div>
    )
  }

  if (tasks.length === 0) {
    return (
      <div className="flex flex-col h-full">
        <PanelNavBar title="Taken" actions={navActions} />
        <EmptyPanel
          message="Nog geen taken voor deze story."
          action={{
            label: 'Nieuwe taak',
            onClick: () => router.push(`${closePath}?newTask=1&storyId=${selectedStoryId}`),
            disabled: isDemo,
          }}
        />
      </div>
    )
  }

  const activeTask = activeDragId ? tasks.find((t) => t.id === activeDragId) : null

  return (
    <div className="flex flex-col h-full">
      <PanelNavBar title="Taken" actions={navActions} />
      <div className="flex-1 overflow-y-auto p-3">
        <DndContext
          id="task-panel"
          sensors={sensors}
          collisionDetection={closestCenter}
          onDragStart={handleDragStart}
          onDragEnd={handleDragEnd}
        >
          <SortableContext items={tasks.map((t) => t.id)} strategy={rectSortingStrategy}>
            <div className="grid grid-cols-2 gap-2">
              {tasks.map((task) => (
                <SortableTaskCard
                  key={task.id}
                  task={task}
                  isDemo={isDemo}
                  onClick={() => router.push(`${closePath}?editTask=${task.id}`)}
                />
              ))}
            </div>
          </SortableContext>

          <DragOverlay>
            {activeTask && (
              <BacklogCard
                title={activeTask.title}
                priority={activeTask.priority}
                className="border-primary shadow-xl opacity-90"
              />
            )}
          </DragOverlay>
        </DndContext>
      </div>
    </div>
  )
}
