'use client'

import { useState, useTransition } from 'react'
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 { Button } from '@/components/ui/button'
import { Badge } from '@/components/ui/badge'
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select'
import { PanelNavBar } from '@/components/shared/panel-nav-bar'
import { useShallow } from 'zustand/react/shallow'
import { useUserSettingsStore } from '@/stores/user-settings/store'
import { useProductWorkspaceStore } from '@/stores/product-workspace/store'
import { selectStoriesForActivePbi } from '@/stores/product-workspace/selectors'
import type { BacklogStory as WorkspaceStory } from '@/stores/product-workspace/types'
import { reorderStoriesAction } from '@/actions/stories'
import { StoryDialog, type StoryDialogState } from './story-dialog'
import { debugProps } from '@/lib/debug'
import { BacklogCard } from './backlog-card'
import { EmptyPanel } from './empty-panel'
import { DemoTooltip } from '@/components/shared/demo-tooltip'
import { cn } from '@/lib/utils'

type SortMode = 'priority' | 'code' | 'date'
const STATUS_COLORS: Record<string, string> = {
  OPEN: 'bg-status-todo/15 text-status-todo border-status-todo/30',
  IN_SPRINT: 'bg-status-in-progress/15 text-status-in-progress border-status-in-progress/30',
  DONE: 'bg-status-done/15 text-status-done border-status-done/30',
}
const STATUS_LABELS: Record<string, string> = {
  OPEN: 'Open',
  IN_SPRINT: 'In Sprint',
  DONE: 'Klaar',
}

export interface Story {
  id: string
  code: string | null
  title: string
  description: string | null
  acceptance_criteria: string | null
  priority: number
  sort_order: number
  status: string
  pbi_id: string
  sprint_id: string | null
  created_at: Date
}

interface StoryPanelProps {
  productId: string
  isDemo: boolean
}

// --- Sortable story block ---
function SortableStoryBlock({
  story,
  isSelected,
  onSelect,
  onEdit,
}: {
  story: Story
  isSelected: boolean
  onSelect: () => void
  onEdit: () => void
}) {
  const { attributes, listeners, setNodeRef, transform, transition, isDragging } = useSortable({
    id: story.id,
  })

  const style = {
    transform: CSS.Transform.toString(transform),
    transition,
    opacity: isDragging ? 0.4 : 1,
  }

  return (
    <BacklogCard
      ref={setNodeRef}
      style={style}
      {...attributes}
      {...listeners}
      title={story.title}
      code={story.code}
      priority={story.priority}
      isDragging={isDragging}
      isSelected={isSelected}
      onClick={onSelect}
      badge={
        <Badge className={cn('text-[10px] px-1.5 py-0 border', STATUS_COLORS[story.status])}>
          {STATUS_LABELS[story.status] ?? story.status}
        </Badge>
      }
      actions={
        <button
          onClick={(e) => { e.stopPropagation(); onEdit() }}
          className="inline-flex items-center justify-center min-h-7 min-w-7 text-muted-foreground hover:text-foreground rounded transition-colors"
          aria-label="Story bewerken"
        >
          <svg className="size-3.5" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
            <path d="M11 4H4a2 2 0 0 0-2 2v14a2 2 0 0 0 2 2h14a2 2 0 0 0 2-2v-7" />
            <path d="M18.5 2.5a2.121 2.121 0 0 1 3 3L12 15l-4 1 1-4 9.5-9.5z" />
          </svg>
        </button>
      }
    />
  )
}

// --- Main component ---
// PBI-74 / T-850: leest stories voor active PBI via selectStoriesForActivePbi
// (useShallow). DnD via applyOptimisticMutation('story-order').
export function StoryPanel({ productId, isDemo }: StoryPanelProps) {
  const selectedPbiId = useProductWorkspaceStore((s) => s.context.activePbiId)
  const selectedStoryId = useProductWorkspaceStore((s) => s.context.activeStoryId)
  const rawStories = useProductWorkspaceStore(useShallow(selectStoriesForActivePbi)) as WorkspaceStory[]
  const [filterStatus, setFilterStatus] = useState<string | null>(null)
  const [filterPriority, setFilterPriority] = useState<number | null>(null)
  const sortMode: SortMode = useUserSettingsStore(
    (s) => s.entities.settings.views?.storyPanel?.sort ?? 'priority',
  )
  const setPref = useUserSettingsStore((s) => s.setPref)
  const setSortMode = (v: SortMode) => void setPref(['views', 'storyPanel', 'sort'], v)
  const [storyDialogState, setStoryDialogState] = useState<StoryDialogState | null>(null)
  const [activeDragId, setActiveDragId] = useState<string | null>(null)
  const [, startTransition] = useTransition()

  // rawStories komt al gesorteerd binnen via selectStoriesForActivePbi.
  const storyMap = Object.fromEntries(rawStories.map(s => [s.id, s]))
  const orderedStories = rawStories

  const base = orderedStories
    .filter(s => !filterStatus || s.status === filterStatus)
    .filter(s => !filterPriority || s.priority === filterPriority)

  const filtered = [...base].sort((a, b) => {
    if (sortMode === 'code') {
      return (a.code ?? '').localeCompare(b.code ?? '', 'nl', { numeric: true })
    }
    if (sortMode === 'date') {
      return new Date(b.created_at).getTime() - new Date(a.created_at).getTime()
    }
    return a.priority !== b.priority ? a.priority - b.priority : 0
  })

  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)
    const { active, over } = event
    if (!over || active.id === over.id || !selectedPbiId) return

    const activeStory = storyMap[active.id as string]
    const overStory = storyMap[over.id as string]
    if (!activeStory || !overStory) return

    const store = useProductWorkspaceStore.getState()
    const prevOrder = [...(store.relations.storyIdsByPbi[selectedPbiId] ?? [])]
    const oldIndex = prevOrder.indexOf(active.id as string)
    const newIndex = prevOrder.indexOf(over.id as string)
    if (oldIndex === -1 || newIndex === -1) return
    const newOrder = arrayMove([...prevOrder], oldIndex, newIndex)

    const orderMutationId = store.applyOptimisticMutation({
      kind: 'story-order',
      pbiId: selectedPbiId,
      prevStoryIds: prevOrder,
    })
    useProductWorkspaceStore.setState((s) => {
      s.relations.storyIdsByPbi[selectedPbiId] = newOrder
    })

    const priorityChanged = activeStory.priority !== overStory.priority
    let priorityMutationId: string | null = null
    if (priorityChanged) {
      priorityMutationId = store.applyOptimisticMutation({
        kind: 'entity-patch',
        entity: 'story',
        id: active.id as string,
        prev: store.entities.storiesById[active.id as string],
      })
      useProductWorkspaceStore.setState((s) => {
        const story = s.entities.storiesById[active.id as string]
        if (story) story.priority = overStory.priority
      })
    }

    startTransition(async () => {
      const result = await reorderStoriesAction(
        selectedPbiId,
        productId,
        newOrder,
        priorityChanged ? overStory.priority : undefined
      )
      const st = useProductWorkspaceStore.getState()
      if (result.success) {
        if (priorityMutationId) st.settleMutation(priorityMutationId)
        st.settleMutation(orderMutationId)
      } else {
        if (priorityMutationId) st.rollbackMutation(priorityMutationId)
        st.rollbackMutation(orderMutationId)
        toast.error('Volgorde opslaan mislukt')
      }
    })
  }

  const hasActiveFilters = filterStatus !== null || filterPriority !== null

  return (
    <div className="flex flex-col h-full" {...debugProps('story-panel', 'StoryPanel', 'components/backlog/story-panel.tsx')}>
      <PanelNavBar
        title="Stories"
        actions={
          <>
            {hasActiveFilters && (
              <button onClick={() => { setFilterStatus(null); setFilterPriority(null) }} className="text-xs text-primary hover:underline">
                Filter wissen ×
              </button>
            )}
            <Select value={sortMode} onValueChange={(v) => setSortMode(v as SortMode)}>
              <SelectTrigger className="h-7 w-28 text-xs">
                <SelectValue />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value="priority">Prioriteit</SelectItem>
                <SelectItem value="code">Code</SelectItem>
                <SelectItem value="date">Datum</SelectItem>
              </SelectContent>
            </Select>
            <Select
              value={filterStatus ?? 'all'}
              onValueChange={(v) => setFilterStatus(!v || v === 'all' ? null : v)}
            >
              <SelectTrigger className="h-7 w-24 text-xs">
                <SelectValue placeholder="Status" />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value="all">Alle</SelectItem>
                <SelectItem value="OPEN">Open</SelectItem>
                <SelectItem value="IN_SPRINT">In Sprint</SelectItem>
                <SelectItem value="DONE">Klaar</SelectItem>
              </SelectContent>
            </Select>
            {selectedPbiId && (
              <DemoTooltip show={isDemo}>
                <Button
                  size="sm"
                  className="h-7 text-xs"
                  disabled={isDemo}
                  onClick={() => !isDemo && setStoryDialogState({ mode: 'create', pbiId: selectedPbiId, productId, defaultPriority: 2 })}
                >
                  + Story
                </Button>
              </DemoTooltip>
            )}
          </>
        }
      />

      <div className="flex-1 overflow-y-auto p-4" {...debugProps('story-panel__tasks')}>
        {selectedPbiId === null ? (
          <EmptyPanel message="Selecteer een PBI om de stories te bekijken." />
        ) : rawStories.length === 0 ? (
          <EmptyPanel
            message="Nog geen stories voor dit PBI."
            action={{ label: 'Maak je eerste story aan', onClick: () => setStoryDialogState({ mode: 'create', pbiId: selectedPbiId, productId, defaultPriority: 2 }), disabled: isDemo }}
          />
        ) : (
          <DndContext
            id="story-panel"
            sensors={sensors}
            collisionDetection={closestCenter}
            onDragStart={handleDragStart}
            onDragEnd={handleDragEnd}
          >
            <SortableContext items={filtered.map(s => s.id)} strategy={rectSortingStrategy}>
              <div className="grid grid-cols-3 gap-2">
                {filtered.map(story => (
                  <SortableStoryBlock
                    key={story.id}
                    story={story}
                    isSelected={selectedStoryId === story.id}
                    onSelect={() => useProductWorkspaceStore.getState().setActiveStory(story.id)}
                    onEdit={() => setStoryDialogState({ mode: 'edit', story, productId })}
                  />
                ))}
              </div>
            </SortableContext>

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

      <StoryDialog
        state={storyDialogState}
        onClose={() => setStoryDialogState(null)}
        isDemo={isDemo}
      />
    </div>
  )
}