'use client';

import { useParams } from 'next/navigation';
import {
  DndContext,
  DragEndEvent,
  DragOverlay,
  DragStartEvent,
  closestCorners,
} from '@dnd-kit/core';
import { useState, useMemo, useEffect } from 'react';
import { useEpics } from '@/lib/hooks/use-epics';
import { useStories } from '@/lib/hooks/use-stories';
import { useTasks } from '@/lib/hooks/use-tasks';
import { useSignalRContext } from '@/lib/signalr/SignalRContext';
import { useQueryClient } from '@tanstack/react-query';
import { Button } from '@/components/ui/button';
import { Plus, Loader2 } from 'lucide-react';
import { KanbanColumn } from '@/components/features/kanban/KanbanColumn';
import { IssueCard } from '@/components/features/kanban/IssueCard';
import { CreateIssueDialog } from '@/components/features/issues/CreateIssueDialog';
import type { Epic, Story, Task } from '@/types/project';

const COLUMNS = [
  { id: 'Backlog', title: 'Backlog', color: 'bg-gray-100' },
  { id: 'Todo', title: 'To Do', color: 'bg-blue-100' },
  { id: 'InProgress', title: 'In Progress', color: 'bg-yellow-100' },
  { id: 'Done', title: 'Done', color: 'bg-green-100' },
];

// Unified work item type for Kanban
type WorkItemType = 'Epic' | 'Story' | 'Task';
interface KanbanWorkItem {
  id: string;
  title: string;
  description: string;
  status: string;
  priority: string;
  type: WorkItemType;
  // Epic properties
  projectId?: string;
  // Story properties
  epicId?: string;
  // Task properties
  storyId?: string;
  // Metadata
  estimatedHours?: number;
  actualHours?: number;
  ownerId?: string;
  createdAt?: string;
  updatedAt?: string;
}

export default function KanbanPage() {
  const params = useParams();
  const projectId = params.id as string;
  const [isCreateDialogOpen, setIsCreateDialogOpen] = useState(false);
  const [activeItem, setActiveItem] = useState<KanbanWorkItem | null>(null);

  // Fetch Epic/Story/Task from ProjectManagement API
  const { data: epics, isLoading: epicsLoading } = useEpics(projectId);
  const { data: stories, isLoading: storiesLoading } = useStories();
  const { data: tasks, isLoading: tasksLoading } = useTasks();

  const isLoading = epicsLoading || storiesLoading || tasksLoading;

  // SignalR real-time updates
  const queryClient = useQueryClient();
  const { service, isConnected } = useSignalRContext();

  // Subscribe to SignalR events for real-time updates
  useEffect(() => {
    if (!isConnected || !service) {
      console.log('[Kanban] SignalR not connected, skipping event subscription');
      return;
    }

    const handlers = service.getEventHandlers();
    if (!handlers) {
      console.log('[Kanban] No event handlers available');
      return;
    }

    console.log('[Kanban] Subscribing to SignalR events...');

    // Epic events (6 events)
    const unsubEpicCreated = handlers.subscribe('epic:created', (event: any) => {
      console.log('[Kanban] Epic created:', event);
      queryClient.invalidateQueries({ queryKey: ['epics', projectId] });
    });

    const unsubEpicUpdated = handlers.subscribe('epic:updated', (event: any) => {
      console.log('[Kanban] Epic updated:', event);
      queryClient.invalidateQueries({ queryKey: ['epics', projectId] });
    });

    const unsubEpicDeleted = handlers.subscribe('epic:deleted', (event: any) => {
      console.log('[Kanban] Epic deleted:', event);
      queryClient.invalidateQueries({ queryKey: ['epics', projectId] });
    });

    const unsubEpicStatusChanged = handlers.subscribe('epic:statusChanged', (event: any) => {
      console.log('[Kanban] Epic status changed:', event);
      // Optimistic update
      queryClient.setQueryData(['epics', projectId], (old: any) => {
        if (!old) return old;
        return old.map((epic: any) =>
          epic.id === event.epicId ? { ...epic, status: event.newStatus } : epic
        );
      });
    });

    const unsubEpicAssigned = handlers.subscribe('epic:assigned', (event: any) => {
      console.log('[Kanban] Epic assigned:', event);
      queryClient.invalidateQueries({ queryKey: ['epics', projectId] });
    });

    const unsubEpicUnassigned = handlers.subscribe('epic:unassigned', (event: any) => {
      console.log('[Kanban] Epic unassigned:', event);
      queryClient.invalidateQueries({ queryKey: ['epics', projectId] });
    });

    // Story events (6 events)
    const unsubStoryCreated = handlers.subscribe('story:created', (event: any) => {
      console.log('[Kanban] Story created:', event);
      queryClient.invalidateQueries({ queryKey: ['stories'] });
    });

    const unsubStoryUpdated = handlers.subscribe('story:updated', (event: any) => {
      console.log('[Kanban] Story updated:', event);
      queryClient.invalidateQueries({ queryKey: ['stories'] });
    });

    const unsubStoryDeleted = handlers.subscribe('story:deleted', (event: any) => {
      console.log('[Kanban] Story deleted:', event);
      queryClient.invalidateQueries({ queryKey: ['stories'] });
    });

    const unsubStoryStatusChanged = handlers.subscribe('story:statusChanged', (event: any) => {
      console.log('[Kanban] Story status changed:', event);
      // Optimistic update
      queryClient.setQueryData(['stories'], (old: any) => {
        if (!old) return old;
        return old.map((story: any) =>
          story.id === event.storyId ? { ...story, status: event.newStatus } : story
        );
      });
    });

    const unsubStoryAssigned = handlers.subscribe('story:assigned', (event: any) => {
      console.log('[Kanban] Story assigned:', event);
      queryClient.invalidateQueries({ queryKey: ['stories'] });
    });

    const unsubStoryUnassigned = handlers.subscribe('story:unassigned', (event: any) => {
      console.log('[Kanban] Story unassigned:', event);
      queryClient.invalidateQueries({ queryKey: ['stories'] });
    });

    // Task events (7 events)
    const unsubTaskCreated = handlers.subscribe('task:created', (event: any) => {
      console.log('[Kanban] Task created:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    const unsubTaskUpdated = handlers.subscribe('task:updated', (event: any) => {
      console.log('[Kanban] Task updated:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    const unsubTaskDeleted = handlers.subscribe('task:deleted', (event: any) => {
      console.log('[Kanban] Task deleted:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    const unsubTaskStatusChanged = handlers.subscribe('task:statusChanged', (event: any) => {
      console.log('[Kanban] Task status changed:', event);
      // Optimistic update
      queryClient.setQueryData(['tasks'], (old: any) => {
        if (!old) return old;
        return old.map((task: any) =>
          task.id === event.taskId ? { ...task, status: event.newStatus } : task
        );
      });
    });

    const unsubTaskAssigned = handlers.subscribe('task:assigned', (event: any) => {
      console.log('[Kanban] Task assigned:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    const unsubTaskUnassigned = handlers.subscribe('task:unassigned', (event: any) => {
      console.log('[Kanban] Task unassigned:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    const unsubTaskCompleted = handlers.subscribe('task:completed', (event: any) => {
      console.log('[Kanban] Task completed:', event);
      queryClient.invalidateQueries({ queryKey: ['tasks'] });
    });

    console.log('[Kanban] Subscribed to 19 SignalR events');

    // Cleanup all subscriptions
    return () => {
      console.log('[Kanban] Unsubscribing from SignalR events...');
      unsubEpicCreated();
      unsubEpicUpdated();
      unsubEpicDeleted();
      unsubEpicStatusChanged();
      unsubEpicAssigned();
      unsubEpicUnassigned();
      unsubStoryCreated();
      unsubStoryUpdated();
      unsubStoryDeleted();
      unsubStoryStatusChanged();
      unsubStoryAssigned();
      unsubStoryUnassigned();
      unsubTaskCreated();
      unsubTaskUpdated();
      unsubTaskDeleted();
      unsubTaskStatusChanged();
      unsubTaskAssigned();
      unsubTaskUnassigned();
      unsubTaskCompleted();
    };
  }, [isConnected, service, projectId, queryClient]);

  // Combine all work items into unified format
  const allWorkItems = useMemo(() => {
    const items: KanbanWorkItem[] = [
      ...(epics || []).map((e) => ({
        ...e,
        type: 'Epic' as const,
      })),
      ...(stories || []).map((s) => ({
        ...s,
        type: 'Story' as const,
      })),
      ...(tasks || []).map((t) => ({
        ...t,
        type: 'Task' as const,
      })),
    ];
    return items;
  }, [epics, stories, tasks]);

  // Group work items by status
  const itemsByStatus = useMemo(() => ({
    Backlog: allWorkItems.filter((i) => i.status === 'Backlog'),
    Todo: allWorkItems.filter((i) => i.status === 'Todo'),
    InProgress: allWorkItems.filter((i) => i.status === 'InProgress'),
    Done: allWorkItems.filter((i) => i.status === 'Done'),
  }), [allWorkItems]);

  const handleDragStart = (event: DragStartEvent) => {
    const item = allWorkItems.find((i) => i.id === event.active.id);
    setActiveItem(item || null);
  };

  const handleDragEnd = (event: DragEndEvent) => {
    const { active, over } = event;
    setActiveItem(null);

    if (!over || active.id === over.id) return;

    const newStatus = over.id as string;
    const item = allWorkItems.find((i) => i.id === active.id);

    if (item && item.status !== newStatus) {
      // TODO: Implement status change mutation for Epic/Story/Task
      // For now, we'll skip the mutation as we need to implement these hooks
      console.log(`TODO: Change ${item.type} ${item.id} status to ${newStatus}`);
    }
  };

  if (isLoading) {
    return (
      <div className="flex h-[50vh] items-center justify-center">
        <Loader2 className="h-8 w-8 animate-spin" />
      </div>
    );
  }

  return (
    <div className="space-y-4">
      <div className="flex items-center justify-between">
        <div>
          <h1 className="text-3xl font-bold">Kanban Board</h1>
          <p className="text-muted-foreground">
            Drag and drop to update issue status
          </p>
        </div>
        <Button onClick={() => setIsCreateDialogOpen(true)}>
          <Plus className="mr-2 h-4 w-4" />
          New Issue
        </Button>
      </div>

      <DndContext
        collisionDetection={closestCorners}
        onDragStart={handleDragStart}
        onDragEnd={handleDragEnd}
      >
        <div className="grid grid-cols-4 gap-4">
          {COLUMNS.map((column) => (
            <KanbanColumn
              key={column.id}
              id={column.id}
              title={column.title}
              issues={itemsByStatus[column.id as keyof typeof itemsByStatus] as any}
            />
          ))}
        </div>

        <DragOverlay>
          {activeItem && <IssueCard issue={activeItem as any} />}
        </DragOverlay>
      </DndContext>

      <CreateIssueDialog
        projectId={projectId}
        open={isCreateDialogOpen}
        onOpenChange={setIsCreateDialogOpen}
      />
    </div>
  );
}