import { useLocation, useNavigate } from 'react-router-dom';
import { useSelector, useDispatch } from 'react-redux';
import {
  Drawer,
  List,
  ListItemButton,
  ListItemIcon,
  ListItemText,
  Toolbar,
  Box,
  Typography,
  Tooltip,
  useMediaQuery,
  useTheme,
} from '@mui/material';
import DashboardIcon from '@mui/icons-material/Dashboard';
import DescriptionIcon from '@mui/icons-material/Description';
import AddCircleIcon from '@mui/icons-material/AddCircle';
import AdminPanelSettingsIcon from '@mui/icons-material/AdminPanelSettings';
import AssignmentIcon from '@mui/icons-material/Assignment';
import PeopleIcon from '@mui/icons-material/People';
import { selectSidebarOpen, setSidebarOpen } from '../app/slices/uiSlice';
import { selectUser } from '../app/slices/authSlice';
import type { RootState } from '../app/store';
import { DRAWER_WIDTH } from '../constants';

const COLLAPSED_WIDTH = 72;

const dispatcherNav = [
  { label: 'Dashboard', path: '/', icon: <DashboardIcon fontSize="small" /> },
  { label: 'My Proposals', path: '/proposals', icon: <DescriptionIcon fontSize="small" /> },
  { label: 'New Proposal', path: '/proposals/new', icon: <AddCircleIcon fontSize="small" /> },
];

const adminNav = [
  { label: 'Admin Queue', path: '/admin', icon: <AdminPanelSettingsIcon fontSize="small" /> },
  { label: 'All Proposals', path: '/admin/proposals', icon: <AssignmentIcon fontSize="small" /> },
];

const sysadminNav = [
  { label: 'Users', path: '/admin/users', icon: <PeopleIcon fontSize="small" /> },
];

const ALL_NAV_PATHS = new Set(
  [...dispatcherNav, ...adminNav, ...sysadminNav].map(n => n.path)
);

function isNavActive(pathname: string, itemPath: string): boolean {
  if (pathname === itemPath) return true;
  if (ALL_NAV_PATHS.has(pathname)) return false;
  if (itemPath === '/' || itemPath === '/admin') return false;
  return pathname.startsWith(itemPath + '/');
}

export default function Sidebar() {
  const navigate = useNavigate();
  const location = useLocation();
  const dispatch = useDispatch();
  const theme = useTheme();
  const open = useSelector((state: RootState) => selectSidebarOpen(state));
  const user = useSelector((state: RootState) => selectUser(state));

  const isMobile = useMediaQuery(theme.breakpoints.down('md')); // <900px
  const isCollapsed = useMediaQuery(theme.breakpoints.between('md', 'lg')); // 900–1200px

  const isAdmin = user?.role === 'Admin' || user?.role === 'SysAdmin';
  const isSysAdmin = user?.role === 'SysAdmin';
  const navItems = dispatcherNav;

  const drawerVariant = isMobile ? 'temporary' : 'persistent';
  const effectiveWidth = isCollapsed ? COLLAPSED_WIDTH : DRAWER_WIDTH;

  const handleNavClick = (path: string) => {
    navigate(path);
    if (isMobile) {
      dispatch(setSidebarOpen(false));
    }
  };

  const handleDrawerClose = () => {
    dispatch(setSidebarOpen(false));
  };

  const renderNavItem = (item: { label: string; path: string; icon: React.ReactNode }) => {
    const button = (
      <ListItemButton
        key={item.path}
        selected={isNavActive(location.pathname, item.path)}
        onClick={() => handleNavClick(item.path)}
        sx={{
          py: 1,
          justifyContent: isCollapsed ? 'center' : 'flex-start',
          minHeight: 40,
        }}
      >
        <ListItemIcon
          sx={{
            minWidth: isCollapsed ? 0 : 40,
            justifyContent: 'center',
          }}
        >
          {item.icon}
        </ListItemIcon>
        {!isCollapsed && (
          <ListItemText primary={item.label} primaryTypographyProps={{ fontSize: '13px' }} />
        )}
      </ListItemButton>
    );

    if (isCollapsed) {
      return (
        <Tooltip key={item.path} title={item.label} placement="right" arrow>
          {button}
        </Tooltip>
      );
    }

    return button;
  };

  return (
    <Drawer
      variant={drawerVariant}
      open={open}
      onClose={handleDrawerClose}
      sx={{
        width: open ? effectiveWidth : 0,
        flexShrink: 0,
        transition: 'width 250ms ease',
        '& .MuiDrawer-paper': {
          width: effectiveWidth,
          boxSizing: 'border-box',
          overflowX: 'hidden',
        },
      }}
    >
      <Toolbar sx={{ minHeight: 64 }} />
      <Box sx={{ overflow: 'auto', flexGrow: 1, pt: 1 }}>
        {isAdmin && (
          <>
            {!isCollapsed && (
              <Typography
                sx={{
                  fontSize: '11px',
                  fontWeight: 700,
                  letterSpacing: '0.08em',
                  textTransform: 'uppercase',
                  color: '#94A3B8',
                  px: 2.5,
                  mb: 0.5,
                }}
              >
                Admin
              </Typography>
            )}
            <List disablePadding>
              {adminNav.map((item) => renderNavItem(item))}
              {isSysAdmin && sysadminNav.map((item) => renderNavItem(item))}
            </List>
          </>
        )}
        {!isCollapsed && (
          <Typography
            sx={{
              fontSize: '11px',
              fontWeight: 700,
              letterSpacing: '0.08em',
              textTransform: 'uppercase',
              color: '#94A3B8',
              px: 2.5,
              mt: isAdmin ? 2 : 0,
              mb: 0.5,
            }}
          >
            Proposals
          </Typography>
        )}
        <List disablePadding>
          {navItems.map((item) => renderNavItem(item))}
        </List>
      </Box>
      {user && !isCollapsed && (
        <Box sx={{ p: 2, mt: 'auto', borderTop: '1px solid #DDE3E8' }}>
          <Box sx={{ fontSize: '13px', fontWeight: 500, color: '#1F2933' }}>{user.displayName}</Box>
          <Box sx={{ fontSize: '11px', color: '#8A949E' }}>{user.role}</Box>
        </Box>
      )}
    </Drawer>
  );
}