import { useMemo, useState } from "react";
import { Link, NavLink, useLocation } from "@/lib/router";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import {
  ChevronRight,
  MoreHorizontal,
  PauseCircle,
  Pencil,
  PlayCircle,
  Plus,
} from "lucide-react";
import { useCompany } from "../context/CompanyContext";
import { useDialogActions } from "../context/DialogContext";
import { useSidebar } from "../context/SidebarContext";
import { useToastActions } from "../context/ToastContext";
import { agentsApi } from "../api/agents";
import { authApi } from "../api/auth";
import { heartbeatsApi } from "../api/heartbeats";
import { SIDEBAR_SCROLL_RESET_STATE } from "../lib/navigation-scroll";
import { queryKeys } from "../lib/queryKeys";
import { cn, agentRouteRef, agentUrl } from "../lib/utils";
import { useAgentOrder } from "../hooks/useAgentOrder";
import { AgentIcon } from "./AgentIconPicker";
import { BudgetSidebarMarker } from "./BudgetSidebarMarker";
import { Button } from "@/components/ui/button";
import {
  Collapsible,
  CollapsibleContent,
  CollapsibleTrigger,
} from "@/components/ui/collapsible";
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuSeparator,
  DropdownMenuTrigger,
} from "@/components/ui/dropdown-menu";
import type { Agent } from "@paperclipai/shared";

function SidebarAgentItem({
  activeAgentId,
  activeTab,
  agent,
  disabled,
  isMobile,
  onPauseResume,
  runCount,
  setSidebarOpen,
}: {
  activeAgentId: string | null;
  activeTab: string | null;
  agent: Agent;
  disabled: boolean;
  isMobile: boolean;
  onPauseResume: (agent: Agent, action: "pause" | "resume") => void;
  runCount: number;
  setSidebarOpen: (open: boolean) => void;
}) {
  const routeRef = agentRouteRef(agent);
  const href = activeTab ? `${agentUrl(agent)}/${activeTab}` : agentUrl(agent);
  const editHref = `${agentUrl(agent)}/configuration`;
  const isActive = activeAgentId === routeRef;
  const isPaused = agent.status === "paused";
  const isBudgetPaused = isPaused && agent.pauseReason === "budget";
  const pauseResumeLabel = isPaused ? "Resume agent" : "Pause agent";
  const pauseResumeDisabled = disabled || agent.status === "pending_approval" || isBudgetPaused;
  const pauseResumeDisabledLabel = disabled
    ? "Updating..."
    : isBudgetPaused
      ? "Budget paused"
      : pauseResumeLabel;

  return (
    <div className="group/agent relative flex items-center">
      <NavLink
        to={href}
        state={SIDEBAR_SCROLL_RESET_STATE}
        onClick={() => {
          if (isMobile) setSidebarOpen(false);
        }}
        className={cn(
          "flex min-w-0 flex-1 items-center gap-2.5 px-3 py-1.5 pr-8 text-[13px] font-medium transition-colors",
          isActive
            ? "bg-accent text-foreground"
            : "text-foreground/80 hover:bg-accent/50 hover:text-foreground"
        )}
      >
        <AgentIcon icon={agent.icon} className="shrink-0 h-3.5 w-3.5 text-muted-foreground" />
        <span className="flex-1 truncate">{agent.name}</span>
        {(agent.pauseReason === "budget" || runCount > 0) && (
          <span className="ml-auto flex items-center gap-1.5 shrink-0">
            {agent.pauseReason === "budget" ? (
              <BudgetSidebarMarker title="Agent paused by budget" />
            ) : null}
            {runCount > 0 ? (
              <span className="relative flex h-2 w-2">
                <span className="animate-pulse absolute inline-flex h-full w-full rounded-full bg-blue-400 opacity-75" />
                <span className="relative inline-flex rounded-full h-2 w-2 bg-blue-500" />
              </span>
            ) : null}
            {runCount > 0 ? (
              <span className="text-[11px] font-medium text-blue-600 dark:text-blue-400">
                {runCount} live
              </span>
            ) : null}
          </span>
        )}
      </NavLink>

      <DropdownMenu>
        <DropdownMenuTrigger asChild>
          <Button
            variant="ghost"
            size="icon-xs"
            className={cn(
              "absolute right-1 top-1/2 h-6 w-6 -translate-y-1/2 transition-opacity data-[state=open]:pointer-events-auto data-[state=open]:opacity-100",
              isMobile
                ? "opacity-100"
                : "pointer-events-none opacity-0 group-hover/agent:pointer-events-auto group-hover/agent:opacity-100 group-focus-within/agent:pointer-events-auto group-focus-within/agent:opacity-100",
            )}
            aria-label={`Open actions for ${agent.name}`}
          >
            <MoreHorizontal className="h-3.5 w-3.5" />
          </Button>
        </DropdownMenuTrigger>
        <DropdownMenuContent align="end" className="w-44">
          <DropdownMenuItem asChild>
            <Link
              to={editHref}
              onClick={() => {
                if (isMobile) setSidebarOpen(false);
              }}
            >
              <Pencil className="size-4" />
              <span>Edit agent</span>
            </Link>
          </DropdownMenuItem>
          <DropdownMenuSeparator />
          <DropdownMenuItem
            onClick={() => {
              if (pauseResumeDisabled) return;
              onPauseResume(agent, isPaused ? "resume" : "pause");
            }}
            disabled={pauseResumeDisabled}
            title={isBudgetPaused ? "Agent was paused by budget limits" : undefined}
          >
            {isPaused ? <PlayCircle className="size-4" /> : <PauseCircle className="size-4" />}
            <span>{pauseResumeDisabledLabel}</span>
          </DropdownMenuItem>
        </DropdownMenuContent>
      </DropdownMenu>
    </div>
  );
}

export function SidebarAgents() {
  const [open, setOpen] = useState(true);
  const [pendingAgentIds, setPendingAgentIds] = useState<Set<string>>(() => new Set());
  const queryClient = useQueryClient();
  const { selectedCompanyId } = useCompany();
  const { openNewAgent } = useDialogActions();
  const { isMobile, setSidebarOpen } = useSidebar();
  const { pushToast } = useToastActions();
  const location = useLocation();

  const { data: agents } = useQuery({
    queryKey: queryKeys.agents.list(selectedCompanyId!),
    queryFn: () => agentsApi.list(selectedCompanyId!),
    enabled: !!selectedCompanyId,
  });
  const { data: session } = useQuery({
    queryKey: queryKeys.auth.session,
    queryFn: () => authApi.getSession(),
  });

  const { data: liveRuns } = useQuery({
    queryKey: queryKeys.liveRuns(selectedCompanyId!),
    queryFn: () => heartbeatsApi.liveRunsForCompany(selectedCompanyId!),
    enabled: !!selectedCompanyId,
    refetchInterval: 10_000,
  });

  const liveCountByAgent = useMemo(() => {
    const counts = new Map<string, number>();
    for (const run of liveRuns ?? []) {
      counts.set(run.agentId, (counts.get(run.agentId) ?? 0) + 1);
    }
    return counts;
  }, [liveRuns]);

  const visibleAgents = useMemo(() => {
    const filtered = (agents ?? []).filter(
      (a: Agent) => a.status !== "terminated"
    );
    return filtered;
  }, [agents]);
  const currentUserId = session?.user?.id ?? session?.session?.userId ?? null;
  const { orderedAgents } = useAgentOrder({
    agents: visibleAgents,
    companyId: selectedCompanyId,
    userId: currentUserId,
  });

  const agentMatch = location.pathname.match(/^\/(?:[^/]+\/)?agents\/([^/]+)(?:\/([^/]+))?/);
  const activeAgentId = agentMatch?.[1] ?? null;
  const activeTab = agentMatch?.[2] ?? null;

  const pauseResumeAgent = useMutation({
    mutationFn: ({ agent, action }: { agent: Agent; action: "pause" | "resume" }) =>
      action === "pause"
        ? agentsApi.pause(agent.id, selectedCompanyId ?? undefined)
        : agentsApi.resume(agent.id, selectedCompanyId ?? undefined),
    onMutate: ({ agent }) => {
      setPendingAgentIds((current) => {
        const next = new Set(current);
        next.add(agent.id);
        return next;
      });
    },
    onSuccess: async (_agent, { agent, action }) => {
      if (selectedCompanyId) {
        await Promise.all([
          queryClient.invalidateQueries({ queryKey: queryKeys.agents.list(selectedCompanyId) }),
          queryClient.invalidateQueries({ queryKey: queryKeys.liveRuns(selectedCompanyId) }),
          queryClient.invalidateQueries({ queryKey: queryKeys.dashboard(selectedCompanyId) }),
        ]);
      }
      await Promise.all([
        queryClient.invalidateQueries({ queryKey: queryKeys.agents.detail(agent.id) }),
        queryClient.invalidateQueries({ queryKey: queryKeys.agents.detail(agentRouteRef(agent)) }),
      ]);
      pushToast({
        title: action === "pause" ? "Agent paused" : "Agent resumed",
        body: agent.name,
        tone: "success",
      });
    },
    onError: (error, { agent, action }) => {
      pushToast({
        title: action === "pause" ? "Could not pause agent" : "Could not resume agent",
        body: error instanceof Error ? error.message : agent.name,
        tone: "error",
      });
    },
    onSettled: (_data, _error, { agent }) => {
      setPendingAgentIds((current) => {
        const next = new Set(current);
        next.delete(agent.id);
        return next;
      });
    },
  });

  return (
    <Collapsible open={open} onOpenChange={setOpen}>
      <div className="group">
        <div className="flex items-center px-3 py-1.5">
          <CollapsibleTrigger className="flex items-center gap-1 flex-1 min-w-0">
            <ChevronRight
              className={cn(
                "h-3 w-3 text-muted-foreground/60 transition-transform opacity-0 group-hover:opacity-100",
                open && "rotate-90"
              )}
            />
            <span className="text-[10px] font-medium uppercase tracking-widest font-mono text-muted-foreground/60">
              Agents
            </span>
          </CollapsibleTrigger>
          <button
            onClick={(e) => {
              e.stopPropagation();
              openNewAgent();
            }}
            className="flex items-center justify-center h-4 w-4 rounded text-muted-foreground/60 hover:text-foreground hover:bg-accent/50 transition-colors"
            aria-label="New agent"
          >
            <Plus className="h-3 w-3" />
          </button>
        </div>
      </div>

      <CollapsibleContent>
        <div className="flex flex-col gap-0.5 mt-0.5">
          {orderedAgents.map((agent: Agent) => {
            const runCount = liveCountByAgent.get(agent.id) ?? 0;
            return (
              <SidebarAgentItem
                key={agent.id}
                activeAgentId={activeAgentId}
                activeTab={activeTab}
                agent={agent}
                disabled={pendingAgentIds.has(agent.id)}
                isMobile={isMobile}
                onPauseResume={(targetAgent, action) => pauseResumeAgent.mutate({ agent: targetAgent, action })}
                runCount={runCount}
                setSidebarOpen={setSidebarOpen}
              />
            );
          })}
        </div>
      </CollapsibleContent>
    </Collapsible>
  );
}