import { useState, useMemo } from 'react';
import { Plus, CheckSquare, CheckCircle2, AlertCircle, Search, ChevronDown } from 'lucide-react';
import { useQuery } from '@tanstack/react-query';
import api from '@/lib/api';
import type { Todo } from '@/types';
import { isTodoOverdue } from '@/lib/utils';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Card, CardContent } from '@/components/ui/card';
import { Checkbox } from '@/components/ui/checkbox';
import { Label } from '@/components/ui/label';
import { ListSkeleton } from '@/components/ui/skeleton';
import TodoList from './TodoList';
import TodoForm from './TodoForm';

const priorityFilters = [
  { value: '', label: 'All' },
  { value: 'none', label: 'None' },
  { value: 'low', label: 'Low' },
  { value: 'medium', label: 'Medium' },
  { value: 'high', label: 'High' },
] as const;

export default function TodosPage() {
  const [showForm, setShowForm] = useState(false);
  const [editingTodo, setEditingTodo] = useState<Todo | null>(null);
  const [filters, setFilters] = useState({
    priority: '',
    category: '',
    showCompleted: true,
    search: '',
  });

  const { data: todos = [], isLoading } = useQuery({
    queryKey: ['todos'],
    queryFn: async () => {
      const { data } = await api.get<Todo[]>('/todos');
      return data;
    },
  });

  const categories = useMemo(() => {
    const cats = new Set<string>();
    todos.forEach((t) => {
      if (t.category) cats.add(t.category);
    });
    return Array.from(cats).sort();
  }, [todos]);

  const filteredTodos = useMemo(
    () =>
      todos.filter((todo) => {
        if (filters.priority && todo.priority !== filters.priority) return false;
        if (filters.category && todo.category?.toLowerCase() !== filters.category.toLowerCase())
          return false;
        if (!filters.showCompleted && todo.completed) return false;
        if (filters.search && !todo.title.toLowerCase().includes(filters.search.toLowerCase()))
          return false;
        return true;
      }),
    [todos, filters]
  );

  const totalCount = filteredTodos.filter((t) => !t.completed).length;
  const completedCount = filteredTodos.filter((t) => t.completed).length;
  const overdueCount = filteredTodos.filter((t) => isTodoOverdue(t.due_date, t.completed)).length;

  const handleEdit = (todo: Todo) => {
    setEditingTodo(todo);
    setShowForm(true);
  };

  const handleCloseForm = () => {
    setShowForm(false);
    setEditingTodo(null);
  };

  return (
    <div className="flex flex-col h-full">
      {/* Header */}
      <div className="border-b bg-card px-6 h-16 flex items-center gap-4 shrink-0">
        <h1 className="font-heading text-2xl font-bold tracking-tight">Todos</h1>

        <div className="flex items-center rounded-md border border-border overflow-hidden ml-4">
          {priorityFilters.map((pf) => (
            <button
              key={pf.value}
              onClick={() => setFilters({ ...filters, priority: pf.value })}
              className={`px-3 py-1.5 text-sm font-medium transition-colors duration-150 ${
                filters.priority === pf.value
                  ? 'bg-accent/15 text-accent'
                  : 'text-muted-foreground hover:text-foreground hover:bg-card-elevated'
              }`}
              style={{
                backgroundColor:
                  filters.priority === pf.value ? 'hsl(var(--accent-color) / 0.15)' : undefined,
                color: filters.priority === pf.value ? 'hsl(var(--accent-color))' : undefined,
              }}
            >
              {pf.label}
            </button>
          ))}
        </div>

        <div className="relative ml-2">
          <Search className="absolute left-2.5 top-1/2 -translate-y-1/2 h-3.5 w-3.5 text-muted-foreground" />
          <Input
            placeholder="Search..."
            value={filters.search}
            onChange={(e) => setFilters({ ...filters, search: e.target.value })}
            className="w-52 h-8 pl-8 text-sm"
          />
        </div>

        <div className="relative">
          <select
            value={filters.category}
            onChange={(e) => setFilters({ ...filters, category: e.target.value })}
            className="h-8 rounded-md border border-input bg-background px-3 pr-8 text-sm text-foreground focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 appearance-none cursor-pointer"
          >
            <option value="">All Categories</option>
            {categories.map((cat) => (
              <option key={cat} value={cat}>
                {cat}
              </option>
            ))}
          </select>
          <ChevronDown className="absolute right-2 top-1/2 -translate-y-1/2 h-3.5 w-3.5 text-muted-foreground pointer-events-none" />
        </div>

        <div className="flex items-center gap-1.5">
          <Checkbox
            id="show-completed"
            checked={filters.showCompleted}
            onChange={(e) =>
              setFilters({ ...filters, showCompleted: (e.target as HTMLInputElement).checked })
            }
          />
          <Label htmlFor="show-completed" className="text-xs text-muted-foreground cursor-pointer">
            Completed
          </Label>
        </div>

        <div className="flex-1" />

        <Button onClick={() => setShowForm(true)} size="sm">
          <Plus className="mr-2 h-4 w-4" />
          Add Todo
        </Button>
      </div>

      <div className="flex-1 overflow-y-auto px-6 py-5">
        {/* Summary stats */}
        {!isLoading && todos.length > 0 && (
          <div className="grid gap-2.5 grid-cols-3 mb-5">
            <Card className="bg-gradient-to-br from-accent/[0.03] to-transparent">
              <CardContent className="p-4 flex items-center gap-3">
                <div className="p-1.5 rounded-md bg-blue-500/10">
                  <CheckSquare className="h-4 w-4 text-blue-400" />
                </div>
                <div>
                  <p className="text-[10px] tracking-wider uppercase text-muted-foreground">
                    Open
                  </p>
                  <p className="font-heading text-xl font-bold tabular-nums">{totalCount}</p>
                </div>
              </CardContent>
            </Card>
            <Card className="bg-gradient-to-br from-accent/[0.03] to-transparent">
              <CardContent className="p-4 flex items-center gap-3">
                <div className="p-1.5 rounded-md bg-green-500/10">
                  <CheckCircle2 className="h-4 w-4 text-green-400" />
                </div>
                <div>
                  <p className="text-[10px] tracking-wider uppercase text-muted-foreground">
                    Completed
                  </p>
                  <p className="font-heading text-xl font-bold tabular-nums">{completedCount}</p>
                </div>
              </CardContent>
            </Card>
            <Card className="bg-gradient-to-br from-accent/[0.03] to-transparent">
              <CardContent className="p-4 flex items-center gap-3">
                <div className="p-1.5 rounded-md bg-red-500/10">
                  <AlertCircle className="h-4 w-4 text-red-400" />
                </div>
                <div>
                  <p className="text-[10px] tracking-wider uppercase text-muted-foreground">
                    Overdue
                  </p>
                  <p className="font-heading text-xl font-bold tabular-nums">{overdueCount}</p>
                </div>
              </CardContent>
            </Card>
          </div>
        )}

        {isLoading ? (
          <ListSkeleton rows={6} />
        ) : (
          <TodoList
            todos={filteredTodos}
            onEdit={handleEdit}
            onAdd={() => setShowForm(true)}
          />
        )}
      </div>

      {showForm && <TodoForm todo={editingTodo} onClose={handleCloseForm} />}
    </div>
  );
}