import { useCallback, useEffect, useLayoutEffect, useMemo, useState } from "react";
import {
  ArrowDown,
  ArrowUp,
  ArrowUpDown,
  BarChart3,
  Brain,
  Cpu,
  RefreshCw,
  TrendingUp,
} from "lucide-react";
import { api } from "@/lib/api";
import type {
  AnalyticsResponse,
  AnalyticsDailyEntry,
  AnalyticsModelEntry,
  AnalyticsSkillEntry,
} from "@/lib/api";
import { timeAgo } from "@/lib/utils";
import { Button } from "@nous-research/ui/ui/components/button";
import { Spinner } from "@nous-research/ui/ui/components/spinner";
import { Stats } from "@nous-research/ui/ui/components/stats";
import { Card, CardContent, CardHeader, CardTitle } from "@nous-research/ui/ui/components/card";
import { usePageHeader } from "@/contexts/usePageHeader";
import { useI18n } from "@/i18n";
import { PluginSlot } from "@/plugins";

const PERIODS = [
  { label: "7d", days: 7 },
  { label: "30d", days: 30 },
  { label: "90d", days: 90 },
] as const;

const CHART_HEIGHT_PX = 160;

function formatTokens(n: number): string {
  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(1)}M`;
  if (n >= 1_000) return `${(n / 1_000).toFixed(1)}K`;
  return String(n);
}

function formatDate(day: string): string {
  try {
    const d = new Date(day + "T00:00:00");
    return d.toLocaleDateString(undefined, { month: "short", day: "numeric" });
  } catch {
    return day;
  }
}

// ---------------------------------------------------------------------------
// Sorting
// ---------------------------------------------------------------------------

function useTableSort<T>(
  data: T[],
  defaultKey: keyof T & string,
  defaultDir: "asc" | "desc" = "desc",
) {
  const [sortKey, setSortKey] = useState<string>(defaultKey);
  const [sortDir, setSortDir] = useState<"asc" | "desc">(defaultDir);

  const sorted = useMemo(() => {
    return [...data].sort((a, b) => {
      const aVal = a[sortKey as keyof T];
      const bVal = b[sortKey as keyof T];
      // Nulls always last regardless of direction
      if (aVal === null || aVal === undefined) return 1;
      if (bVal === null || bVal === undefined) return -1;
      if (aVal === bVal) return 0;
      const cmp = aVal > bVal ? 1 : -1;
      return sortDir === "asc" ? cmp : -cmp;
    });
  }, [data, sortKey, sortDir]);

  const toggle = useCallback(
    (key: string) => {
      if (key === sortKey) {
        setSortDir((d) => (d === "asc" ? "desc" : "asc"));
      } else {
        setSortKey(key);
        setSortDir("desc");
      }
    },
    [sortKey],
  );

  return { sorted, sortKey, sortDir, toggle };
}

function SortHeader({
  label,
  col,
  sortKey,
  sortDir,
  toggle,
  className,
}: {
  label: string;
  col: string;
  sortKey: string;
  sortDir: "asc" | "desc";
  toggle: (key: string) => void;
  className?: string;
}) {
  const active = col === sortKey;
  return (
    <th
      onClick={() => toggle(col)}
      className={`cursor-pointer select-none ${className ?? ""}`}
    >
      <span className="inline-flex items-center gap-1.5 rounded px-1 -mx-1 py-0.5 hover:bg-muted/40 transition-colors">
        {label}
        {active ? (
          sortDir === "asc" ? (
            <ArrowUp className="h-3.5 w-3.5 text-foreground/80 shrink-0" />
          ) : (
            <ArrowDown className="h-3.5 w-3.5 text-foreground/80 shrink-0" />
          )
        ) : (
          <ArrowUpDown className="h-3 w-3 text-text-tertiary shrink-0" />
        )}
      </span>
    </th>
  );
}



function TokenBarChart({ daily }: { daily: AnalyticsDailyEntry[] }) {
  const { t } = useI18n();
  if (daily.length === 0) return null;

  const maxTokens = Math.max(
    ...daily.map((d) => d.input_tokens + d.output_tokens),
    1,
  );

  return (
    <Card>
      <CardHeader>
        <div className="flex items-center gap-2">
          <BarChart3 className="h-5 w-5 text-muted-foreground" />
          <CardTitle className="text-base">
            {t.analytics.dailyTokenUsage}
          </CardTitle>
        </div>
        <div className="flex items-center gap-4 font-mondwest normal-case text-xs text-muted-foreground">
          <div className="flex items-center gap-1.5">
            <div
              className="h-2.5 w-2.5"
              style={{ backgroundColor: "var(--series-input-token)" }}
            />
            {t.analytics.input}
          </div>
          <div className="flex items-center gap-1.5">
            <div
              className="h-2.5 w-2.5"
              style={{ backgroundColor: "var(--series-output-token)" }}
            />
            {t.analytics.output}
          </div>
        </div>
      </CardHeader>
      <CardContent>
        <div
          className="flex items-end gap-[2px]"
          style={{ height: CHART_HEIGHT_PX }}
        >
          {daily.map((d) => {
            const total = d.input_tokens + d.output_tokens;
            const inputH = Math.round(
              (d.input_tokens / maxTokens) * CHART_HEIGHT_PX,
            );
            const outputH = Math.round(
              (d.output_tokens / maxTokens) * CHART_HEIGHT_PX,
            );
            return (
              <div
                key={d.day}
                className="flex-1 min-w-0 group relative flex flex-col justify-end"
                style={{ height: CHART_HEIGHT_PX }}
              >
                <div className="absolute bottom-full left-1/2 -translate-x-1/2 mb-2 hidden group-hover:block z-10 pointer-events-none">
                  <div className="font-mondwest normal-case bg-card border border-border px-2.5 py-1.5 text-xs text-foreground shadow-lg whitespace-nowrap">
                    <div className="font-medium">{formatDate(d.day)}</div>
                    <div>
                      {t.analytics.input}: {formatTokens(d.input_tokens)}
                    </div>
                    <div>
                      {t.analytics.output}: {formatTokens(d.output_tokens)}
                    </div>
                    <div>
                      {t.analytics.total}: {formatTokens(total)}
                    </div>
                  </div>
                </div>

                <div
                  className="w-full"
                  style={{
                    backgroundColor:
                      "color-mix(in srgb, var(--series-input-token) 70%, transparent)",
                    height: Math.max(inputH, total > 0 ? 1 : 0),
                  }}
                />

                <div
                  className="w-full"
                  style={{
                    backgroundColor:
                      "color-mix(in srgb, var(--series-output-token) 70%, transparent)",
                    height: Math.max(outputH, d.output_tokens > 0 ? 1 : 0),
                  }}
                />
              </div>
            );
          })}
        </div>

        <div className="flex justify-between mt-2 font-mondwest normal-case text-xs text-text-tertiary">
          <span>{daily.length > 0 ? formatDate(daily[0].day) : ""}</span>
          {daily.length > 2 && (
            <span>{formatDate(daily[Math.floor(daily.length / 2)].day)}</span>
          )}
          <span>
            {daily.length > 1 ? formatDate(daily[daily.length - 1].day) : ""}
          </span>
        </div>
      </CardContent>
    </Card>
  );
}

function DailyTable({ daily }: { daily: AnalyticsDailyEntry[] }) {
  const { t } = useI18n();
  const { sorted, sortKey, sortDir, toggle } = useTableSort(daily, "day", "desc");

  if (daily.length === 0) return null;

  return (
    <Card>
      <CardHeader>
        <div className="flex items-center gap-2">
          <TrendingUp className="h-5 w-5 text-muted-foreground" />
          <CardTitle className="text-base">
            {t.analytics.dailyBreakdown}
          </CardTitle>
        </div>
      </CardHeader>
      <CardContent>
        <div className="overflow-x-auto">
          <table className="w-full font-mondwest normal-case text-sm">
            <thead>
              <tr className="border-b border-border text-muted-foreground text-xs">
                <SortHeader label={t.analytics.date} col="day" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-left py-2 pr-4 font-medium" />
                <SortHeader label={t.sessions.title} col="sessions" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.input} col="input_tokens" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.output} col="output_tokens" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 pl-4 font-medium" />
              </tr>
            </thead>
            <tbody>
              {sorted.map((d) => (
                <tr
                    key={d.day}
                    className="border-b border-border/50 hover:bg-secondary/20 transition-colors"
                  >
                  <td className="py-2 pr-4 font-medium">
                      {formatDate(d.day)}
                    </td>
                  <td className="text-right py-2 px-4 text-muted-foreground">
                      {d.sessions}
                    </td>
                  <td className="text-right py-2 px-4">
                    <span style={{ color: "var(--series-input-token)" }}>
                        {formatTokens(d.input_tokens)}
                      </span>
                  </td>
                  <td className="text-right py-2 pl-4">
                    <span style={{ color: "var(--series-output-token)" }}>
                        {formatTokens(d.output_tokens)}
                      </span>
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      </CardContent>
    </Card>
  );
}

function ModelTable({ models }: { models: AnalyticsModelEntry[] }) {
  const { t } = useI18n();
  const { sorted, sortKey, sortDir, toggle } = useTableSort(models, "input_tokens", "desc");

  if (models.length === 0) return null;

  return (
    <Card>
      <CardHeader>
        <div className="flex items-center gap-2">
          <Cpu className="h-5 w-5 text-muted-foreground" />
          <CardTitle className="text-base">
            {t.analytics.perModelBreakdown}
          </CardTitle>
        </div>
      </CardHeader>
      <CardContent>
        <div className="overflow-x-auto">
          <table className="w-full font-mondwest normal-case text-sm">
            <thead>
              <tr className="border-b border-border text-muted-foreground text-xs">
                <SortHeader label={t.analytics.model} col="model" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-left py-2 pr-4 font-medium" />
                <SortHeader label={t.sessions.title} col="sessions" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.tokens} col="input_tokens" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 pl-4 font-medium" />
              </tr>
            </thead>
            <tbody>
              {sorted.map((m) => (
                <tr
                  key={m.model}
                  className="border-b border-border/50 hover:bg-secondary/20 transition-colors"
                >
                  <td className="py-2 pr-4">
                    <span className="font-mono-ui text-xs">{m.model}</span>
                  </td>
                  <td className="text-right py-2 px-4 text-muted-foreground">
                    {m.sessions}
                  </td>
                  <td className="text-right py-2 pl-4">
                    <span style={{ color: "var(--series-input-token)" }}>
                      {formatTokens(m.input_tokens)}
                    </span>
                    {" / "}
                    <span style={{ color: "var(--series-output-token)" }}>
                      {formatTokens(m.output_tokens)}
                    </span>
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      </CardContent>
    </Card>
  );
}

function SkillTable({ skills }: { skills: AnalyticsSkillEntry[] }) {
  const { t } = useI18n();
  const { sorted, sortKey, sortDir, toggle } = useTableSort(skills, "total_count", "desc");

  if (skills.length === 0) return null;

  return (
    <Card>
      <CardHeader>
        <div className="flex items-center gap-2">
          <Brain className="h-5 w-5 text-muted-foreground" />
          <CardTitle className="text-base">{t.analytics.topSkills}</CardTitle>
        </div>
      </CardHeader>
      <CardContent>
        <div className="overflow-x-auto">
          <table className="w-full font-mondwest normal-case text-sm">
            <thead>
              <tr className="border-b border-border text-muted-foreground text-xs">
                <SortHeader label={t.analytics.skill} col="skill" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-left py-2 pr-4 font-medium" />
                <SortHeader label={t.analytics.loads} col="view_count" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.edits} col="manage_count" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.total} col="total_count" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 px-4 font-medium" />
                <SortHeader label={t.analytics.lastUsed} col="last_used_at" sortKey={sortKey} sortDir={sortDir} toggle={toggle} className="text-right py-2 pl-4 font-medium" />
              </tr>
            </thead>
            <tbody>
              {sorted.map((skill) => (
                <tr
                  key={skill.skill}
                  className="border-b border-border/50 hover:bg-secondary/20 transition-colors"
                >
                  <td className="py-2 pr-4">
                    <span className="font-mono-ui text-xs">{skill.skill}</span>
                  </td>
                  <td className="text-right py-2 px-4 text-muted-foreground">
                    {skill.view_count}
                  </td>
                  <td className="text-right py-2 px-4 text-muted-foreground">
                    {skill.manage_count}
                  </td>
                  <td className="text-right py-2 px-4">{skill.total_count}</td>
                  <td className="text-right py-2 pl-4 text-muted-foreground">
                    {skill.last_used_at ? timeAgo(skill.last_used_at) : "—"}
                  </td>
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      </CardContent>
    </Card>
  );
}

export default function AnalyticsPage() {
  const [days, setDays] = useState(30);
  const [data, setData] = useState<AnalyticsResponse | null>(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  // Gated on `dashboard.show_token_analytics` (default off).  When off the
  // page renders an explanation card instead of fetching analytics — the
  // local token counts exclude auxiliary calls and provider retries, so
  // they diverge from provider billing in ways that mislead users.
  const [showTokens, setShowTokens] = useState<boolean | null>(null);
  const { t } = useI18n();
  const { setAfterTitle, setEnd } = usePageHeader();

  useEffect(() => {
    api
      .getConfig()
      .then((cfg) => {
        const dash = (cfg?.dashboard ?? {}) as { show_token_analytics?: unknown };
        setShowTokens(dash.show_token_analytics === true);
      })
      .catch(() => setShowTokens(false));
  }, []);

  const load = useCallback(() => {
    if (!showTokens) return;
    setLoading(true);
    setError(null);
    api
      .getAnalytics(days)
      .then(setData)
      .catch((err) => setError(String(err)))
      .finally(() => setLoading(false));
  }, [days, showTokens]);

  useLayoutEffect(() => {
    // Period selector + refresh both live in afterTitle so the controls
    // sit immediately next to the page title instead of being pinned to
    // the far-right `end` slot. The active period is conveyed by the
    // filled (non-outlined) button — no redundant period badge.
    setAfterTitle(
      showTokens === false ? null : (
        <div className="flex flex-wrap items-center gap-1.5">
          {PERIODS.map((p) => (
            <Button
              key={p.label}
              type="button"
              size="sm"
              outlined={days !== p.days}
              onClick={() => setDays(p.days)}
            >
              {p.label}
            </Button>
          ))}
          <Button
            type="button"
            ghost
            size="icon"
            className="text-muted-foreground hover:text-foreground"
            onClick={load}
            disabled={loading}
            aria-label={t.common.refresh}
          >
            {loading ? <Spinner /> : <RefreshCw />}
          </Button>
        </div>
      ),
    );
    setEnd(null);
    return () => {
      setAfterTitle(null);
      setEnd(null);
    };
  }, [days, loading, load, setAfterTitle, setEnd, t.common.refresh, showTokens]);

  useEffect(() => {
    load();
  }, [load]);

  return (
    <div className="flex flex-col gap-6">
      <PluginSlot name="analytics:top" />

      {showTokens === false && (
        <Card>
          <CardContent className="py-12">
            <div className="mx-auto flex max-w-2xl flex-col gap-3 text-sm text-muted-foreground">
              <h2 className="font-mondwest text-display text-base tracking-wider text-foreground">
                Token analytics hidden
              </h2>
              <p>
                The token, cost, and per-day analytics on this page are a
                local debug estimate. They only count successful main-agent
                responses with a usable <span className="font-mono">usage</span>{" "}
                block, and silently exclude auxiliary calls (context
                compression, title generation, vision, session search, web
                extract, smart approvals, MCP routing, plugin LLM access)
                plus provider-side retries and fallback attempts. Cache
                writes are missing entirely.
              </p>
              <p>
                On models with heavy auxiliary traffic (Kimi K2.6, MiniMax
                M2.7) the local total can be 10x–100x lower than what your
                provider bills. Hiding these numbers is safer than letting
                them look authoritative.
              </p>
              <p>
                Check your provider dashboard (OpenRouter, Anthropic, etc.)
                for actual usage and billing. To re-enable the local debug
                estimate anyway, set{" "}
                <span className="font-mono">
                  dashboard.show_token_analytics: true
                </span>{" "}
                in <a href="/config" className="underline">Config</a>.
              </p>
            </div>
          </CardContent>
        </Card>
      )}

      {showTokens && loading && !data && (
        <div className="flex items-center justify-center py-24">
          <Spinner className="text-2xl text-primary" />
        </div>
      )}

      {showTokens && error && (
        <Card>
          <CardContent className="py-6">
            <p className="text-sm text-destructive text-center">{error}</p>
          </CardContent>
        </Card>
      )}

      {showTokens && data && (
        <>
          <div className="grid gap-6 lg:grid-cols-2">
            <Card>
              <CardContent className="py-6">
                <Stats
                  items={[
                    {
                      label: t.analytics.totalTokens,
                      value: formatTokens(
                        data.totals.total_input + data.totals.total_output,
                      ),
                    },
                    {
                      label: t.analytics.input,
                      value: formatTokens(data.totals.total_input),
                    },
                    {
                      label: t.analytics.output,
                      value: formatTokens(data.totals.total_output),
                    },
                    {
                      label: t.analytics.totalSessions,
                      value: `${data.totals.total_sessions} (~${(data.totals.total_sessions / days).toFixed(1)}${t.analytics.perDayAvg})`,
                    },
                    {
                      label: t.analytics.apiCalls,
                      value: String(
                        data.totals.total_api_calls ??
                          data.daily.reduce((sum, d) => sum + d.sessions, 0),
                      ),
                    },
                  ]}
                />
              </CardContent>
            </Card>

            <TokenBarChart daily={data.daily} />
          </div>

          <DailyTable daily={data.daily} />
          <ModelTable models={data.by_model} />
          <SkillTable skills={data.skills.top_skills} />
        </>
      )}

      {data &&
        data.daily.length === 0 &&
        data.by_model.length === 0 &&
        data.skills.top_skills.length === 0 && (
          <Card>
            <CardContent className="py-12">
              <div className="flex flex-col items-center text-muted-foreground">
                <BarChart3 className="h-8 w-8 mb-3 opacity-40" />
                <p className="text-sm font-medium">{t.analytics.noUsageData}</p>
                <p className="text-xs mt-1 text-text-tertiary">
                  {t.analytics.startSession}
                </p>
              </div>
            </CardContent>
          </Card>
        )}
      <PluginSlot name="analytics:bottom" />
    </div>
  );
}