import { useState } from "react";
import { Card, CardContent } from "@/components/ui/card";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/components/ui/table";
import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogTrigger } from "@/components/ui/dialog";
import { Label } from "@/components/ui/label";
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
import { Plus, Pencil, Trash2, Loader2 } from "lucide-react";
import {
  useDepartments,
  useCreateDepartment,
  useUpdateDepartment,
  useDeleteDepartment,
} from "@/hooks/queries/useAcademic";
import { useToast } from "@/hooks/use-toast";
import type { Department, DepartmentCreateRequest } from "@/types/academic";

export default function DepartmentManager() {
  const { toast } = useToast();
  const { data: deptsData, isLoading } = useDepartments();
  const depts = deptsData?.items ?? [];
  const createDept = useCreateDepartment();
  const updateDept = useUpdateDepartment();
  const deleteDept = useDeleteDepartment();
  const [showDialog, setShowDialog] = useState(false);
  const [editing, setEditing] = useState<Department | null>(null);
  const [form, setForm] = useState<DepartmentCreateRequest>({ name: "", code: "" });

  const openCreate = () => {
    setEditing(null);
    setForm({ name: "", code: "" });
    setShowDialog(true);
  };

  const openEdit = (dept: Department) => {
    setEditing(dept);
    setForm({ name: dept.name, code: dept.code, parent_id: dept.parent_id });
    setShowDialog(true);
  };

  const handleSave = () => {
    if (editing) {
      updateDept.mutate({ id: editing.id, data: form }, {
        onSuccess: () => { toast({ title: "Department updated" }); setShowDialog(false); },
        onError: () => toast({ title: "Error", description: "Failed to update", variant: "destructive" }),
      });
    } else {
      createDept.mutate(form, {
        onSuccess: () => { toast({ title: "Department created" }); setShowDialog(false); setForm({ name: "", code: "" }); },
        onError: () => toast({ title: "Error", description: "Failed to create", variant: "destructive" }),
      });
    }
  };

  const handleDelete = (id: number) => {
    if (!window.confirm("Delete this department?")) return;
    deleteDept.mutate(id, {
      onSuccess: () => toast({ title: "Department deleted" }),
      onError: () => toast({ title: "Error", description: "Failed to delete", variant: "destructive" }),
    });
  };

  const isSaving = createDept.isPending || updateDept.isPending;

  if (isLoading) return <div className="flex items-center justify-center min-h-[400px]"><div className="animate-spin rounded-full h-8 w-8 border-b-2 border-primary" /></div>;

  return (
    <div className="space-y-6">
      <div className="flex items-center justify-between">
        <div>
          <h1 className="text-2xl font-bold">Departments</h1>
          <p className="text-muted-foreground">Manage departments and their hierarchy.</p>
        </div>
        <Dialog open={showDialog} onOpenChange={setShowDialog}>
          <DialogTrigger asChild>
            <Button onClick={openCreate}><Plus className="mr-2 h-4 w-4" /> Add Department</Button>
          </DialogTrigger>
          <DialogContent>
            <DialogHeader><DialogTitle>{editing ? "Edit Department" : "Create Department"}</DialogTitle></DialogHeader>
            <div className="space-y-4 pt-4">
              <div className="space-y-2">
                <Label>Name</Label>
                <Input placeholder="e.g. Computer Science" value={form.name} onChange={e => setForm({ ...form, name: e.target.value })} />
              </div>
              <div className="space-y-2">
                <Label>Code</Label>
                <Input placeholder="e.g. CS" value={form.code} onChange={e => setForm({ ...form, code: e.target.value })} />
              </div>
              <div className="space-y-2">
                <Label>Parent Department</Label>
                <Select value={form.parent_id?.toString() ?? "none"} onValueChange={v => setForm({ ...form, parent_id: v === "none" ? undefined : Number(v) })}>
                  <SelectTrigger><SelectValue placeholder="None" /></SelectTrigger>
                  <SelectContent>
                    <SelectItem value="none">None</SelectItem>
                    {depts.filter(d => d.id !== editing?.id).map(d => (
                      <SelectItem key={d.id} value={d.id.toString()}>{d.name}</SelectItem>
                    ))}
                  </SelectContent>
                </Select>
              </div>
              <Button className="w-full" onClick={handleSave} disabled={isSaving || !form.name || !form.code}>
                {isSaving && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
                {editing ? "Update" : "Create"}
              </Button>
            </div>
          </DialogContent>
        </Dialog>
      </div>

      <Card>
        <CardContent className="pt-6">
          <Table>
            <TableHeader>
              <TableRow>
                <TableHead>Name</TableHead>
                <TableHead>Code</TableHead>
                <TableHead>Parent</TableHead>
                <TableHead>Courses</TableHead>
                <TableHead>Faculty</TableHead>
                <TableHead className="text-right">Actions</TableHead>
              </TableRow>
            </TableHeader>
            <TableBody>
              {depts.map((dept: Department) => (
                <TableRow key={dept.id}>
                  <TableCell className="font-medium">{dept.name}</TableCell>
                  <TableCell>{dept.code}</TableCell>
                  <TableCell className="text-muted-foreground">{dept.parent_name ?? "—"}</TableCell>
                  <TableCell>{dept.course_count}</TableCell>
                  <TableCell>{dept.faculty_count}</TableCell>
                  <TableCell className="text-right">
                    <div className="flex items-center justify-end gap-1">
                      <Button variant="ghost" size="icon" onClick={() => openEdit(dept)}>
                        <Pencil className="h-4 w-4" />
                      </Button>
                      <Button variant="ghost" size="icon" onClick={() => handleDelete(dept.id)} disabled={deleteDept.isPending}>
                        <Trash2 className="h-4 w-4 text-destructive" />
                      </Button>
                    </div>
                  </TableCell>
                </TableRow>
              ))}
              {depts.length === 0 && (
                <TableRow>
                  <TableCell colSpan={6} className="text-center py-8 text-muted-foreground">No departments found.</TableCell>
                </TableRow>
              )}
            </TableBody>
          </Table>
        </CardContent>
      </Card>
    </div>
  );
}