'use client';

import React, { useEffect, useState } from 'react';
import { useSelector } from 'react-redux';
import { RootState } from '@/store/store';
import {
  BarChart3,
  Users,
  FileText,
  TrendingUp,
  Clock,
  AlertTriangle,
  CheckCircle2,
  Loader2,
  Cpu,
  Zap,
} from 'lucide-react';
import { Card } from '@/components/ui/card';
import { getHeader } from '@/app/(presentation-generator)/services/api/header';
import { cn } from '@/lib/utils';

interface OverviewData {
  total_presentations: number;
  this_month: number;
  this_week: number;
  active_users: number;
  approval_rate: number;
}

interface UsageData {
  daily: { date: string; count: number }[];
  top_users: { user_id: string; count: number }[];
}

interface QualityData {
  status_distribution: Record<string, number>;
  presentations_with_comments: number;
}

interface PerformanceData {
  job_status_distribution: Record<string, number>;
  avg_generation_time_seconds: number | null;
  error_rate: number;
  total_jobs: number;
}

interface AIUsageData {
  total_calls: number;
  total_input_tokens: number;
  total_output_tokens: number;
  total_tokens: number;
  by_provider: { provider: string; calls: number; tokens: number }[];
  by_model: { model: string; calls: number; tokens: number }[];
  daily: { date: string; calls: number; tokens: number }[];
}

async function fetchAnalytics(endpoint: string, clientId?: string) {
  const params = clientId ? `?client_id=${clientId}` : '';
  const response = await fetch(`/api/v1/admin/analytics/${endpoint}${params}`, {
    headers: getHeader(),
  });
  if (!response.ok) throw new Error(`Failed to fetch ${endpoint}`);
  return response.json();
}

function StatCard({
  title,
  value,
  icon: Icon,
  subtitle,
  color = 'text-[hsl(var(--primary))]',
}: {
  title: string;
  value: string | number;
  icon: React.ElementType;
  subtitle?: string;
  color?: string;
}) {
  return (
    <Card className="p-5 hover:shadow-md transition-shadow">
      <div className="flex items-start justify-between">
        <div>
          <p className="caption">{title}</p>
          <p className="text-2xl font-bold mt-1">{value}</p>
          {subtitle && <p className="caption mt-1">{subtitle}</p>}
        </div>
        <div className={cn('p-3 rounded-lg bg-[hsl(var(--primary-light))]', color)}>
          <Icon className="w-5 h-5" />
        </div>
      </div>
    </Card>
  );
}

function MiniBarChart({ data }: { data: { date: string; count: number }[] }) {
  if (!data.length) return <p className="text-gray-400 text-sm text-center py-8">No data</p>;
  const max = Math.max(...data.map((d) => d.count), 1);
  const last14 = data.slice(-14);

  return (
    <div className="flex items-end gap-1 h-32">
      {last14.map((d, i) => (
        <div key={i} className="flex-1 flex flex-col items-center gap-1">
          <div
            className="w-full bg-[#5146E5] rounded-t"
            style={{ height: `${(d.count / max) * 100}%`, minHeight: d.count > 0 ? 4 : 0 }}
          />
          <span className="text-[9px] text-gray-400 truncate w-full text-center">
            {d.date.slice(5)}
          </span>
        </div>
      ))}
    </div>
  );
}

function StatusBar({ distribution }: { distribution: Record<string, number> }) {
  const total = Object.values(distribution).reduce((a, b) => a + b, 0);
  if (total === 0) return <p className="text-gray-400 text-sm text-center py-4">No data</p>;

  const colors: Record<string, string> = {
    draft: 'bg-yellow-400',
    in_review: 'bg-blue-400',
    approved: 'bg-green-400',
  };

  return (
    <div>
      <div className="flex rounded-full overflow-hidden h-4 mb-3">
        {Object.entries(distribution).map(([status, count]) => (
          <div
            key={status}
            className={cn('transition-all', colors[status] || 'bg-gray-300')}
            style={{ width: `${(count / total) * 100}%` }}
          />
        ))}
      </div>
      <div className="flex gap-4 text-xs">
        {Object.entries(distribution).map(([status, count]) => (
          <div key={status} className="flex items-center gap-1.5">
            <div className={cn('w-2.5 h-2.5 rounded-full', colors[status] || 'bg-gray-300')} />
            <span className="capitalize">{status.replace('_', ' ')}</span>
            <span className="text-gray-400">({count})</span>
          </div>
        ))}
      </div>
    </div>
  );
}

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);
}

export default function AnalyticsPage() {
  const user = useSelector((state: RootState) => state.auth.user);
  const [overview, setOverview] = useState<OverviewData | null>(null);
  const [usage, setUsage] = useState<UsageData | null>(null);
  const [quality, setQuality] = useState<QualityData | null>(null);
  const [performance, setPerformance] = useState<PerformanceData | null>(null);
  const [aiUsage, setAiUsage] = useState<AIUsageData | null>(null);
  const [isLoading, setIsLoading] = useState(true);

  // Auto-filter by user's clientId
  const clientId = user?.clientId || undefined;

  useEffect(() => {
    if (!user) return;
    loadAll();
  }, [user?.clientId]);

  const loadAll = async () => {
    setIsLoading(true);
    try {
      const [o, u, q, p, ai] = await Promise.all([
        fetchAnalytics('overview', clientId),
        fetchAnalytics('usage', clientId),
        fetchAnalytics('quality', clientId),
        fetchAnalytics('performance', clientId),
        fetchAnalytics('ai-usage', clientId).catch(() => null),
      ]);
      setOverview(o);
      setUsage(u);
      setQuality(q);
      setPerformance(p);
      setAiUsage(ai);
    } catch (e) {
      console.error('Analytics load error:', e);
    } finally {
      setIsLoading(false);
    }
  };

  if (isLoading && !overview) {
    return (
      <div className="flex items-center justify-center h-64">
        <Loader2 className="w-8 h-8 animate-spin text-gray-400" />
      </div>
    );
  }

  return (
    <div className="space-y-6">
      <div className="flex items-center justify-between">
        <h1 className="text-2xl font-semibold">Analytics</h1>
      </div>

      {/* Overview Cards */}
      {overview && (
        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-5 gap-4">
          <StatCard
            title="Total Presentations"
            value={overview.total_presentations}
            icon={FileText}
          />
          <StatCard
            title="This Month"
            value={overview.this_month}
            icon={TrendingUp}
            color="text-green-600"
          />
          <StatCard
            title="This Week"
            value={overview.this_week}
            icon={BarChart3}
            color="text-blue-600"
          />
          <StatCard
            title="Active Users"
            value={overview.active_users}
            icon={Users}
            subtitle="Last 30 days"
          />
          <StatCard
            title="Approval Rate"
            value={`${overview.approval_rate}%`}
            icon={CheckCircle2}
            color="text-green-600"
          />
        </div>
      )}

      {/* Charts Row */}
      <div className="grid grid-cols-1 lg:grid-cols-2 gap-6">
        <Card className="p-5">
          <h3 className="text-sm font-semibold mb-4">Presentations per Day</h3>
          {usage ? <MiniBarChart data={usage.daily} /> : <p className="text-gray-400">Loading...</p>}
        </Card>

        <Card className="p-5">
          <h3 className="text-sm font-semibold mb-4">Status Distribution</h3>
          {quality ? (
            <StatusBar distribution={quality.status_distribution} />
          ) : (
            <p className="text-gray-400">Loading...</p>
          )}
        </Card>
      </div>

      {/* Performance Row */}
      {performance && (
        <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
          <StatCard
            title="Avg Generation Time"
            value={
              performance.avg_generation_time_seconds
                ? `${Math.round(performance.avg_generation_time_seconds)}s`
                : 'N/A'
            }
            icon={Clock}
            color="text-orange-600"
          />
          <StatCard
            title="Total Jobs"
            value={performance.total_jobs}
            icon={BarChart3}
          />
          <StatCard
            title="Error Rate"
            value={`${performance.error_rate}%`}
            icon={AlertTriangle}
            color={performance.error_rate > 10 ? 'text-red-600' : 'text-green-600'}
          />
        </div>
      )}

      {/* AI Usage Section */}
      {aiUsage && (
        <>
          <h2 className="text-lg font-semibold mt-2">AI Model Usage</h2>
          <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
            <StatCard
              title="Total AI Calls"
              value={aiUsage.total_calls}
              icon={Cpu}
              color="text-purple-600"
            />
            <StatCard
              title="Input Tokens"
              value={formatTokens(aiUsage.total_input_tokens)}
              icon={Zap}
              color="text-blue-600"
            />
            <StatCard
              title="Output Tokens"
              value={formatTokens(aiUsage.total_output_tokens)}
              icon={Zap}
              color="text-green-600"
            />
          </div>

          {aiUsage.by_provider.length > 0 && (
            <Card className="p-5">
              <h3 className="text-sm font-semibold mb-4">Usage by Provider</h3>
              <div className="space-y-2">
                {aiUsage.by_provider.map((p) => {
                  const maxCalls = Math.max(...aiUsage.by_provider.map((x) => x.calls), 1);
                  return (
                    <div key={p.provider} className="flex items-center gap-3">
                      <span className="text-sm font-medium w-24 capitalize">{p.provider}</span>
                      <div className="flex-1">
                        <div
                          className="h-6 bg-purple-100 rounded flex items-center px-2"
                          style={{ width: `${(p.calls / maxCalls) * 100}%`, minWidth: 60 }}
                        >
                          <span className="text-xs font-medium">{p.calls} calls</span>
                        </div>
                      </div>
                      <span className="text-xs text-gray-400 w-20 text-right">
                        {formatTokens(p.tokens)} tokens
                      </span>
                    </div>
                  );
                })}
              </div>
            </Card>
          )}
        </>
      )}

      {/* Top Users */}
      {usage && usage.top_users.length > 0 && (
        <Card className="p-5">
          <h3 className="text-sm font-semibold mb-4">Top Users (Last 30 Days)</h3>
          <div className="space-y-2">
            {usage.top_users.map((u, i) => {
              const maxCount = usage.top_users[0].count || 1;
              return (
                <div key={u.user_id} className="flex items-center gap-3">
                  <span className="text-xs text-gray-400 w-5">{i + 1}.</span>
                  <div className="flex-1">
                    <div
                      className="h-6 bg-[#5146E5]/10 rounded flex items-center px-2"
                      style={{ width: `${(u.count / maxCount) * 100}%`, minWidth: 60 }}
                    >
                      <span className="text-xs font-medium truncate">
                        {u.user_id.slice(0, 8)}...
                      </span>
                    </div>
                  </div>
                  <span className="text-sm font-semibold text-gray-700">{u.count}</span>
                </div>
              );
            })}
          </div>
        </Card>
      )}
    </div>
  );
}