import {
  useSessions,
  useCancelQuery,
  useTerminateBackend,
} from "@/hooks/use-management";
import { Badge } from "@/components/ui/badge";
import { Button } from "@/components/ui/button";
import { toast } from "sonner";
import { Loader2, XCircle, Skull, RefreshCw } from "lucide-react";
import { useQueryClient } from "@tanstack/react-query";

interface Props {
  connectionId: string;
}

function getStateBadge(state: string | null) {
  if (!state) return null;
  const colors: Record<string, string> = {
    idle: "bg-green-500/15 text-green-600",
    active: "bg-yellow-500/15 text-yellow-600",
    "idle in transaction": "bg-orange-500/15 text-orange-600",
    disabled: "bg-red-500/15 text-red-600",
  };
  return (
    <Badge variant="outline" className={`text-[9px] px-1 py-0 ${colors[state] ?? ""}`}>
      {state}
    </Badge>
  );
}

function formatDuration(queryStart: string | null): string {
  if (!queryStart) return "-";
  const start = new Date(queryStart).getTime();
  const now = Date.now();
  const diffSec = Math.floor((now - start) / 1000);
  if (diffSec < 0) return "-";
  if (diffSec < 60) return `${diffSec}s`;
  if (diffSec < 3600) return `${Math.floor(diffSec / 60)}m ${diffSec % 60}s`;
  return `${Math.floor(diffSec / 3600)}h ${Math.floor((diffSec % 3600) / 60)}m`;
}

function getDurationColor(queryStart: string | null, state: string | null): string {
  if (state !== "active" || !queryStart) return "";
  const diffSec = (Date.now() - new Date(queryStart).getTime()) / 1000;
  if (diffSec > 30) return "text-red-500 font-semibold";
  if (diffSec > 5) return "text-yellow-500 font-semibold";
  return "";
}

export function SessionsView({ connectionId }: Props) {
  const { data: sessions, isLoading } = useSessions(connectionId);
  const cancelMutation = useCancelQuery();
  const terminateMutation = useTerminateBackend();
  const queryClient = useQueryClient();

  const handleCancel = (pid: number) => {
    cancelMutation.mutate(
      { connectionId, pid },
      {
        onSuccess: () => toast.success(`Cancel signal sent to PID ${pid}`),
        onError: (err) => toast.error("Cancel failed", { description: String(err) }),
      }
    );
  };

  const handleTerminate = (pid: number) => {
    if (!confirm(`Terminate backend PID ${pid}? This will kill the session.`)) return;
    terminateMutation.mutate(
      { connectionId, pid },
      {
        onSuccess: () => toast.success(`Terminate signal sent to PID ${pid}`),
        onError: (err) => toast.error("Terminate failed", { description: String(err) }),
      }
    );
  };

  if (isLoading) {
    return (
      <div className="flex h-full items-center justify-center text-muted-foreground">
        <Loader2 className="mr-2 h-5 w-5 animate-spin" />
        Loading sessions...
      </div>
    );
  }

  return (
    <div className="flex h-full flex-col">
      <div className="flex items-center gap-2 border-b px-3 py-1.5">
        <span className="text-xs font-semibold">Active Sessions</span>
        <Badge variant="secondary" className="text-[10px]">
          {sessions?.length ?? 0}
        </Badge>
        <span className="text-[10px] text-muted-foreground">Auto-refresh: 5s</span>
        <Button
          variant="ghost"
          size="sm"
          className="ml-auto h-6 gap-1 text-xs"
          onClick={() => queryClient.invalidateQueries({ queryKey: ["sessions"] })}
        >
          <RefreshCw className="h-3 w-3" />
          Refresh
        </Button>
      </div>

      <div className="flex-1 overflow-auto">
        <table className="w-full text-xs">
          <thead className="sticky top-0 bg-card border-b">
            <tr>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">PID</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">User</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Database</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">State</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Duration</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Wait</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Query</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Client</th>
              <th className="px-2 py-1.5 text-left font-medium text-muted-foreground">Actions</th>
            </tr>
          </thead>
          <tbody>
            {sessions?.map((s) => (
              <tr key={s.pid} className="border-b hover:bg-accent/50">
                <td className="px-2 py-1 font-mono">{s.pid}</td>
                <td className="px-2 py-1">{s.usename ?? "-"}</td>
                <td className="px-2 py-1">{s.datname ?? "-"}</td>
                <td className="px-2 py-1">{getStateBadge(s.state)}</td>
                <td className={`px-2 py-1 ${getDurationColor(s.query_start, s.state)}`}>
                  {formatDuration(s.query_start)}
                </td>
                <td className="px-2 py-1 text-muted-foreground">
                  {s.wait_event ? `${s.wait_event_type}: ${s.wait_event}` : "-"}
                </td>
                <td className="px-2 py-1 max-w-xs truncate font-mono" title={s.query ?? ""}>
                  {s.query ? (s.query.length > 60 ? s.query.slice(0, 60) + "..." : s.query) : "-"}
                </td>
                <td className="px-2 py-1 text-muted-foreground">{s.client_addr ?? "-"}</td>
                <td className="px-2 py-1">
                  <div className="flex gap-0.5">
                    <Button
                      variant="ghost"
                      size="sm"
                      className="h-5 w-5 p-0"
                      title="Cancel Query"
                      onClick={() => handleCancel(s.pid)}
                    >
                      <XCircle className="h-3 w-3 text-yellow-500" />
                    </Button>
                    <Button
                      variant="ghost"
                      size="sm"
                      className="h-5 w-5 p-0"
                      title="Terminate Backend"
                      onClick={() => handleTerminate(s.pid)}
                    >
                      <Skull className="h-3 w-3 text-red-500" />
                    </Button>
                  </div>
                </td>
              </tr>
            ))}
          </tbody>
        </table>
        {(!sessions || sessions.length === 0) && (
          <div className="py-8 text-center text-xs text-muted-foreground">
            No active sessions
          </div>
        )}
      </div>
    </div>
  );
}