import { useQuery } from "@tanstack/react-query";
import { Activity, Download, Gauge, HardDrive, MemoryStick, ScanSearch, Terminal } from "lucide-react";
import { useEffect, useRef, useState, type ReactNode } from "react";

import { EmptyState, Spinner } from "@/components/ui";
import { api } from "@/lib/api";
import { cn } from "@/lib/cn";
import { formatBytes } from "@/lib/format";
import type { StatJob, SystemStats } from "@/lib/types";
import { useAuth } from "@/store/auth";

const REFRESH_MS = 2000;

/** DESIGN.md capacity bars: blue, peach at 80%, red at 95%. */
function meterColor(percent: number): string {
  if (percent >= 95) return "bg-ctp-red";
  if (percent >= 80) return "bg-ctp-peach";
  return "bg-ctp-blue";
}

function Meter({ percent, className }: { percent: number; className?: string }) {
  return (
    <div className={cn("h-1 overflow-hidden rounded-full bg-ctp-surface0", className)}>
      <div
        className={cn("h-full rounded-full transition-all", meterColor(percent))}
        style={{ width: `${Math.min(100, Math.max(0, percent))}%` }}
      />
    </div>
  );
}

function Panel({
  title,
  icon,
  right,
  children,
  className,
}: {
  title: string;
  icon?: ReactNode;
  right?: ReactNode;
  children: ReactNode;
  className?: string;
}) {
  return (
    <section
      className={cn(
        "flex flex-col rounded-lg border border-ctp-surface0 bg-ctp-base p-4",
        className,
      )}
    >
      <div className="flex items-center justify-between gap-2">
        <h2 className="flex items-center gap-2 text-sm font-semibold text-ctp-subtext1">
          {icon}
          {title}
        </h2>
        {right}
      </div>
      <div className="mt-3 flex flex-1 flex-col gap-3">{children}</div>
    </section>
  );
}

function formatUptime(seconds: number): string {
  const days = Math.floor(seconds / 86400);
  const hours = Math.floor((seconds % 86400) / 3600);
  const minutes = Math.floor((seconds % 3600) / 60);
  if (days > 0) return `${days} d ${hours} h`;
  if (hours > 0) return `${hours} h ${minutes} m`;
  return `${minutes} m`;
}

function jobStatusClass(status: string): string {
  if (status === "error") return "text-ctp-red";
  if (status === "cancelled") return "text-ctp-overlay0";
  if (status === "complete") return "text-ctp-green";
  return "text-ctp-blue";
}

function JobRow({ job, showSummary }: { job: StatJob; showSummary?: boolean }) {
  const Icon = job.kind === "download" ? Download : ScanSearch;
  return (
    <li className="flex flex-col gap-1">
      <div className="flex items-center gap-2 text-xs">
        <Icon className="h-3.5 w-3.5 shrink-0 text-ctp-overlay0" />
        <span className="truncate font-mono text-ctp-subtext1">{job.label}</span>
        <span className={cn("ml-auto shrink-0 font-mono text-[11px]", jobStatusClass(job.status))}>
          {job.status}
        </span>
      </div>
      {showSummary ? (
        <p className="truncate pl-5 text-[11px] text-ctp-overlay0" title={job.summary ?? job.detail}>
          {job.summary ?? job.detail}
        </p>
      ) : (
        <>
          <Meter percent={job.progress} className="ml-5" />
          <p className="truncate pl-5 font-mono text-[10px] text-ctp-overlay0">
            {job.progress}% · {job.detail}
          </p>
        </>
      )}
    </li>
  );
}

function logLineClass(line: string): string {
  const level = /^(DEBUG|INFO|WARNING|ERROR|CRITICAL)\b/.exec(line)?.[1];
  if (level === "ERROR" || level === "CRITICAL") return "text-ctp-red";
  if (level === "WARNING") return "text-ctp-peach";
  if (level === "DEBUG") return "text-ctp-overlay0";
  return "text-ctp-subtext0";
}

export default function StatsPage() {
  const user = useAuth((state) => state.user);
  const staff = Boolean(
    user &&
      (user.is_staff || user.is_superuser || user.role === "staff"),
  );
  const query = useQuery({
    queryKey: ["stats"],
    queryFn: () => api<SystemStats>("/api/stats/"),
    enabled: staff,
    refetchInterval: staff ? REFRESH_MS : false,
  });
  const [autoScroll, setAutoScroll] = useState(true);
  const logRef = useRef<HTMLDivElement>(null);
  const data = query.data;
  const logLines = data?.log.lines ?? [];
  const logCount = logLines.length;

  useEffect(() => {
    if (!autoScroll || !logRef.current) return;
    logRef.current.scrollTop = logRef.current.scrollHeight;
  }, [logCount, autoScroll]);

  if (!staff) {
    return (
      <EmptyState
        title="Staff only"
        description="This dashboard is limited to staff accounts."
      />
    );
  }

  if (query.isPending) {
    return (
      <div className="flex justify-center py-24">
        <Spinner className="h-6 w-6" />
      </div>
    );
  }

  if (query.isError || !data) {
    return (
      <EmptyState
        title="Could not load statistics"
        description="The backend did not answer the stats endpoint."
      />
    );
  }

  const { system, gpus, disk, jobs, log } = data;
  const memoryPercent = system.memory.percent;
  const cores = system.cpu.per_cpu ?? [];

  return (
    <div className="mx-auto flex w-full max-w-6xl flex-col gap-6">
      <header className="flex flex-wrap items-end justify-between gap-2">
        <div>
          <h1 className="text-lg font-semibold">Stats</h1>
          <p className="mt-1 text-sm text-ctp-overlay0">
            Host telemetry, background jobs and the application log. Refreshing
            every {REFRESH_MS / 1000} s.
          </p>
        </div>
        <p className="font-mono text-[11px] text-ctp-overlay0">
          up {formatUptime(system.uptime_seconds)}
        </p>
      </header>

      <div className="grid gap-4 sm:grid-cols-2 xl:grid-cols-4">
        <Panel
          title="CPU"
          icon={<Gauge className="h-4 w-4 text-ctp-overlay0" />}
          right={
            <span className="font-mono text-xs text-ctp-subtext1">
              {system.cpu.percent.toFixed(1)}%
            </span>
          }
        >
          <p className="text-[11px] text-ctp-overlay0">
            {system.cpu.cores} logical cores
            {system.cpu.physical_cores
              ? ` · ${system.cpu.physical_cores} physical`
              : ""}
            {system.cpu.load.length > 0
              ? ` · load ${system.cpu.load.join(" / ")}`
              : ""}
          </p>
          <Meter percent={system.cpu.percent} />
          <div className="flex flex-wrap gap-1">
            {cores.map((value, index) => (
              <span
                key={index}
                title={`Core ${index}: ${value}%`}
                className="h-6 w-1.5 overflow-hidden rounded-sm bg-ctp-surface0"
              >
                <span
                  className={cn("block w-full", meterColor(value))}
                  style={{
                    height: `${Math.min(100, Math.max(0, value))}%`,
                    marginTop: `${100 - Math.min(100, Math.max(0, value))}%`,
                  }}
                />
              </span>
            ))}
          </div>
        </Panel>

        <Panel
          title="Memory"
          icon={<MemoryStick className="h-4 w-4 text-ctp-overlay0" />}
          right={
            <span className="font-mono text-xs text-ctp-subtext1">
              {memoryPercent.toFixed(1)}%
            </span>
          }
        >
          <p className="font-mono text-[11px] text-ctp-overlay0">
            {formatBytes(system.memory.used)} /{" "}
            {formatBytes(system.memory.total)} · {formatBytes(system.memory.available)} free
          </p>
          <Meter percent={memoryPercent} />
          {system.memory.swap_total > 0 ? (
            <>
              <p className="font-mono text-[11px] text-ctp-overlay0">
                swap {formatBytes(system.memory.swap_used)} /{" "}
                {formatBytes(system.memory.swap_total)}
              </p>
              <Meter percent={system.memory.swap_percent} />
            </>
          ) : null}
        </Panel>

        {gpus.length > 0 ? (
          gpus.map((gpu) => (
            <Panel
              key={gpu.name}
              title="GPU"
              icon={<Activity className="h-4 w-4 text-ctp-overlay0" />}
              right={
                <span className="font-mono text-xs text-ctp-subtext1">
                  {gpu.utilization ?? "?"}%
                </span>
              }
            >
              <p className="truncate text-[11px] text-ctp-overlay0" title={gpu.name}>
                {gpu.name}
              </p>
              <Meter percent={gpu.utilization ?? 0} />
              <p className="font-mono text-[11px] text-ctp-overlay0">
                {gpu.memory_used !== null && gpu.memory_total !== null
                  ? `vram ${formatBytes(gpu.memory_used)} / ${formatBytes(gpu.memory_total)}`
                  : "vram unknown"}
                {gpu.temperature !== null ? ` · ${gpu.temperature}°C` : ""}
              </p>
            </Panel>
          ))
        ) : (
          <Panel
            title="GPU"
            icon={<Activity className="h-4 w-4 text-ctp-overlay0" />}
          >
            <p className="text-[11px] text-ctp-overlay0">
              No NVIDIA GPU reported by nvidia-smi.
            </p>
          </Panel>
        )}

        <Panel
          title="Disk"
          icon={<HardDrive className="h-4 w-4 text-ctp-overlay0" />}
          right={
            <span className="font-mono text-xs text-ctp-subtext1">
              {disk.watched_folder.percent_used.toFixed(1)}%
            </span>
          }
        >
          <p className="font-mono text-[11px] text-ctp-overlay0">
            {formatBytes(disk.watched_folder.used)} /{" "}
            {formatBytes(disk.watched_folder.total)} · {formatBytes(disk.watched_folder.free)} free
          </p>
          <Meter percent={disk.watched_folder.percent_used} />
          <p className="truncate font-mono text-[11px] text-ctp-overlay0" title={disk.watched_folder.path}>
            library {formatBytes(disk.watched_folder.library_size)} ·{" "}
            {disk.library_items} items
          </p>
          <p className="truncate font-mono text-[11px] text-ctp-overlay0" title={disk.media.path}>
            media {formatBytes(disk.media.size)} · temp{" "}
            {formatBytes(disk.temp.size)} ({disk.temp.files} files)
          </p>
        </Panel>
      </div>

      <div className="grid gap-4 lg:grid-cols-2">
        <Panel
          title="Active jobs"
          icon={<Activity className="h-4 w-4 text-ctp-overlay0" />}
          right={
            <span className="font-mono text-[11px] text-ctp-overlay0">
              {jobs.active_count} running
            </span>
          }
        >
          {jobs.active.length === 0 ? (
            <p className="text-xs text-ctp-overlay0">
              Nothing running — downloads and match scans appear here.
            </p>
          ) : (
            <ul className="flex flex-col gap-3">
              {jobs.active.map((job) => (
                <JobRow key={`${job.kind}-${job.id}`} job={job} />
              ))}
            </ul>
          )}
        </Panel>

        <Panel
          title="Recently finished"
          icon={<Download className="h-4 w-4 text-ctp-overlay0" />}
        >
          {jobs.recent.length === 0 ? (
            <p className="text-xs text-ctp-overlay0">No finished jobs yet.</p>
          ) : (
            <ul className="flex flex-col gap-3">
              {jobs.recent.map((job) => (
                <JobRow key={`${job.kind}-${job.id}`} job={job} showSummary />
              ))}
            </ul>
          )}
        </Panel>
      </div>

      <Panel
        title="Log"
        icon={<Terminal className="h-4 w-4 text-ctp-overlay0" />}
        right={
          <div className="flex items-center gap-3">
            <label className="flex items-center gap-1.5 text-[11px] text-ctp-overlay0">
              <input
                type="checkbox"
                checked={autoScroll}
                onChange={(event) => setAutoScroll(event.target.checked)}
                className="accent-ctp-mauve"
              />
              auto-scroll
            </label>
            <span className="truncate font-mono text-[10px] text-ctp-overlay0" title={log.path}>
              {log.path}
            </span>
          </div>
        }
      >
        {log.missing ? (
          <p className="text-xs text-ctp-overlay0">
            No log file yet — it is created on the next log write.
          </p>
        ) : (
          <div
            ref={logRef}
            className="max-h-80 overflow-auto rounded-md bg-ctp-crust/60 p-3 font-mono text-[11px] leading-relaxed"
          >
            {logLines.map((line, index) => (
              <div key={index} className={cn("whitespace-pre-wrap", logLineClass(line))}>
                {line}
              </div>
            ))}
          </div>
        )}
      </Panel>
    </div>
  );
}