"use client";

import { useEffect, useState } from "react";
import { fetchKnowledgeStats } from "@/lib/api/knowledge";
import Link from "next/link";

interface KnowledgeStats {
  overview: {
    totalEntries: number;
    totalTags: number;
    totalLinks: number;
    publishedEntries: number;
    draftEntries: number;
    archivedEntries: number;
  };
  mostConnected: {
    id: string;
    slug: string;
    title: string;
    incomingLinks: number;
    outgoingLinks: number;
    totalConnections: number;
  }[];
  recentActivity: {
    id: string;
    slug: string;
    title: string;
    updatedAt: string;
    status: string;
  }[];
  tagDistribution: {
    id: string;
    name: string;
    slug: string;
    color: string | null;
    entryCount: number;
  }[];
}

export function StatsDashboard(): React.JSX.Element {
  const [stats, setStats] = useState<KnowledgeStats | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    async function loadStats(): Promise<void> {
      try {
        setIsLoading(true);
        const data = await fetchKnowledgeStats();
        setStats(data as KnowledgeStats);
      } catch (err) {
        setError(err instanceof Error ? err.message : "Failed to load statistics");
      } finally {
        setIsLoading(false);
      }
    }

    void loadStats();
  }, []);

  if (isLoading) {
    return (
      <div className="flex items-center justify-center p-12">
        <div className="animate-spin rounded-full h-8 w-8 border-b-2 border-blue-500" />
      </div>
    );
  }

  if (error || !stats) {
    return <div className="p-8 text-center text-red-500">Error loading statistics: {error}</div>;
  }

  const { overview, mostConnected, recentActivity, tagDistribution } = stats;

  return (
    <div className="p-6 space-y-6">
      <div className="flex items-center justify-between">
        <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-100">
          Knowledge Base Statistics
        </h1>
        <Link
          href="/knowledge"
          className="text-sm text-blue-600 hover:text-blue-800 dark:text-blue-400 dark:hover:text-blue-300"
        >
          Back to Entries
        </Link>
      </div>

      {/* Overview Cards */}
      <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
        <StatsCard
          title="Total Entries"
          value={overview.totalEntries}
          subtitle={`${String(overview.publishedEntries)} published • ${String(overview.draftEntries)} drafts`}
          icon="📚"
        />
        <StatsCard
          title="Tags"
          value={overview.totalTags}
          subtitle="Organize your knowledge"
          icon="🏷️"
        />
        <StatsCard
          title="Connections"
          value={overview.totalLinks}
          subtitle="Links between entries"
          icon="🔗"
        />
      </div>

      {/* Two Column Layout */}
      <div className="grid grid-cols-1 lg:grid-cols-2 gap-6">
        {/* Most Connected Entries */}
        <div className="bg-white dark:bg-gray-800 rounded-lg shadow p-6">
          <h2 className="text-lg font-semibold text-gray-900 dark:text-gray-100 mb-4">
            Most Connected Entries
          </h2>
          <div className="space-y-3">
            {mostConnected.slice(0, 10).map((entry) => (
              <div
                key={entry.id}
                className="flex items-center justify-between p-3 bg-gray-50 dark:bg-gray-700 rounded hover:bg-gray-100 dark:hover:bg-gray-600 transition-colors"
              >
                <div className="flex-1 min-w-0">
                  <Link
                    href={`/knowledge/${entry.slug}`}
                    className="text-sm font-medium text-gray-900 dark:text-gray-100 hover:text-blue-600 dark:hover:text-blue-400 truncate block"
                  >
                    {entry.title}
                  </Link>
                  <div className="text-xs text-gray-500 dark:text-gray-400 mt-1">
                    {entry.incomingLinks} incoming • {entry.outgoingLinks} outgoing
                  </div>
                </div>
                <div className="ml-4 flex-shrink-0">
                  <span className="inline-flex items-center justify-center w-10 h-10 rounded-full bg-blue-100 dark:bg-blue-900 text-blue-600 dark:text-blue-400 font-semibold text-sm">
                    {entry.totalConnections}
                  </span>
                </div>
              </div>
            ))}
            {mostConnected.length === 0 && (
              <p className="text-sm text-gray-500 dark:text-gray-400 text-center py-4">
                No connections yet
              </p>
            )}
          </div>
        </div>

        {/* Recent Activity */}
        <div className="bg-white dark:bg-gray-800 rounded-lg shadow p-6">
          <h2 className="text-lg font-semibold text-gray-900 dark:text-gray-100 mb-4">
            Recent Activity
          </h2>
          <div className="space-y-3">
            {recentActivity.slice(0, 10).map((entry) => (
              <div
                key={entry.id}
                className="flex items-start justify-between p-3 bg-gray-50 dark:bg-gray-700 rounded hover:bg-gray-100 dark:hover:bg-gray-600 transition-colors"
              >
                <div className="flex-1 min-w-0">
                  <Link
                    href={`/knowledge/${entry.slug}`}
                    className="text-sm font-medium text-gray-900 dark:text-gray-100 hover:text-blue-600 dark:hover:text-blue-400 truncate block"
                  >
                    {entry.title}
                  </Link>
                  <div className="text-xs text-gray-500 dark:text-gray-400 mt-1">
                    {new Date(entry.updatedAt).toLocaleDateString()} •{" "}
                    <span className="capitalize">{entry.status.toLowerCase()}</span>
                  </div>
                </div>
              </div>
            ))}
            {recentActivity.length === 0 && (
              <p className="text-sm text-gray-500 dark:text-gray-400 text-center py-4">
                No recent activity
              </p>
            )}
          </div>
        </div>
      </div>

      {/* Tag Distribution */}
      <div className="bg-white dark:bg-gray-800 rounded-lg shadow p-6">
        <h2 className="text-lg font-semibold text-gray-900 dark:text-gray-100 mb-4">
          Tag Distribution
        </h2>
        <div className="grid grid-cols-1 sm:grid-cols-2 md:grid-cols-3 lg:grid-cols-4 gap-3">
          {tagDistribution.slice(0, 12).map((tag) => (
            <div
              key={tag.id}
              className="flex items-center justify-between p-3 rounded bg-gray-50 dark:bg-gray-700"
            >
              <div className="flex items-center gap-2 flex-1 min-w-0">
                {tag.color && (
                  <div
                    className="w-3 h-3 rounded-full flex-shrink-0"
                    style={{ backgroundColor: tag.color }}
                  />
                )}
                <span className="text-sm font-medium text-gray-900 dark:text-gray-100 truncate">
                  {tag.name}
                </span>
              </div>
              <span className="ml-2 text-xs font-semibold text-gray-600 dark:text-gray-400 flex-shrink-0">
                {tag.entryCount}
              </span>
            </div>
          ))}
          {tagDistribution.length === 0 && (
            <p className="text-sm text-gray-500 dark:text-gray-400 col-span-full text-center py-4">
              No tags yet
            </p>
          )}
        </div>
      </div>
    </div>
  );
}

function StatsCard({
  title,
  value,
  subtitle,
  icon,
}: {
  title: string;
  value: number;
  subtitle: string;
  icon: string;
}): React.JSX.Element {
  return (
    <div className="bg-white dark:bg-gray-800 rounded-lg shadow p-6">
      <div className="flex items-center justify-between">
        <div>
          <p className="text-sm font-medium text-gray-600 dark:text-gray-400">{title}</p>
          <p className="text-3xl font-bold text-gray-900 dark:text-gray-100 mt-2">{value}</p>
          <p className="text-xs text-gray-500 dark:text-gray-400 mt-1">{subtitle}</p>
        </div>
        <div className="text-4xl">{icon}</div>
      </div>
    </div>
  );
}