"use client";

import { useEffect, useMemo, useState } from "react";
import Link from "next/link";
import { useRouter, useSearchParams } from "next/navigation";
import { useToast } from "@/lib/toast";
import {
  COMPARE_METRICS,
  compareUrl,
  getWinnerIdx,
  overallScore,
  parseCompareSlugs,
} from "@/lib/compareScore";
import { mergeDestinationsIntoTrip } from "@/lib/tripActions";
import { useI18n } from "@/lib/i18n";
import type { Destination } from "@/lib/types";
import RingNext from "@/components/RingNext";
import { useRingSteps } from "@/lib/rings";

interface Props {
  destinations: Destination[];
}

export default function CompareClient({ destinations }: Props) {
  const searchParams = useSearchParams();
  const router = useRouter();
  const { toast } = useToast();
  const { t } = useI18n();
  const rings = useRingSteps();
  const [picked, setPicked] = useState<string[]>([]);

  useEffect(() => {
    const fromUrl = parseCompareSlugs(searchParams.get("cities"));
    if (fromUrl.length) {
      setPicked(fromUrl.filter((s) => destinations.some((d) => d.slug === s)));
      return;
    }
    setPicked([]);
  }, [searchParams, destinations]);

  const selected = useMemo(
    () => picked.map((s) => destinations.find((d) => d.slug === s)).filter((d): d is Destination => !!d),
    [picked, destinations]
  );

  const scores = selected.map(overallScore);
  const winnerIdx = scores.length ? scores.indexOf(Math.max(...scores)) : -1;

  const syncUrl = (slugs: string[]) => {
    const href = compareUrl(slugs);
    router.replace(href, { scroll: false });
  };

  const toggle = (slug: string) => {
    setPicked((prev) => {
      let next: string[];
      if (prev.includes(slug)) next = prev.filter((s) => s !== slug);
      else if (prev.length >= 4) {
        toast(t.compare.maxCities, "info");
        return prev;
      } else next = [...prev, slug];
      syncUrl(next);
      return next;
    });
  };

  const addAll = () => {
    if (selected.length < 1) return;
    const { added, skipped } = mergeDestinationsIntoTrip(selected, 1);
    if (added === 0) {
      toast(skipped ? t.compare.alreadyInPlan : t.compare.alreadyOne, "info");
      router.push("/plan");
      return;
    }
    toast(`${t.compare.addedN} ${added} ${t.compare.citiesUnit}${skipped ? `（${t.compare.skipped} ${skipped}）` : ""}`);
    router.push("/plan");
  };

  const addWinner = () => {
    if (winnerIdx < 0) return;
    const d = selected[winnerIdx];
    const { added } = mergeDestinationsIntoTrip([d], 1);
    toast(added ? `${d.emoji} ${d.name} ${t.compare.wrotePlan}` : t.compare.alreadyOne, added ? "success" : "info");
    if (added) router.push("/plan");
  };

  const share = async () => {
    if (selected.length < 2) {
      toast(t.compare.needShare, "info");
      return;
    }
    const url = `${window.location.origin}${compareUrl(selected.map((d) => d.slug))}`;
    await navigator.clipboard.writeText(url);
    toast(t.compare.linkCopied);
  };

  return (
    <div className="compare-page">
      <div className="container">
        <nav className="detail-nav">
          <Link href="/">{t.common.backHome}</Link>
          <Link href="/#destinations">{t.compare.dest}</Link>
          <Link href="/plan">{t.compare.plan}</Link>
        </nav>

        <header className="compare-page-hero">
          <span className="section-tag">{t.compare.tag}</span>
          <h1>{t.compare.title}</h1>
          <p>{t.compare.subtitle}</p>
        </header>

        <section className="compare-pick plan-panel">
          <div className="plan-panel-head">
            <h2>{t.compare.pick}（{picked.length}/4）</h2>
            <div className="plan-actions">
              <button type="button" className="btn btn-ghost btn-sm" disabled={picked.length === 0} onClick={() => { setPicked([]); syncUrl([]); }}>{t.compare.clear}</button>
              <button type="button" className="btn btn-ghost btn-sm" disabled={selected.length < 2} onClick={share}>{t.compare.copyLink}</button>
            </div>
          </div>
          <div className="compare-pick-grid">
            {destinations.map((d) => {
              const on = picked.includes(d.slug);
              return (
                <button
                  key={d.slug}
                  type="button"
                  className={`compare-pick-chip${on ? " on" : ""}`}
                  onClick={() => toggle(d.slug)}
                  aria-pressed={on}
                >
                  <span>{d.emoji}</span>
                  <strong>{d.name}</strong>
                  <small>¥{d.cost.toLocaleString()}</small>
                </button>
              );
            })}
          </div>
        </section>

        {selected.length < 2 ? (
          <div className="plan-empty compare-page-empty">
            <span className="plan-empty-icon">⚖️</span>
            <p>{t.compare.needMore} {Math.max(0, 2 - selected.length)} {t.compare.needMoreSuffix}</p>
            <Link href="/#destinations" className="btn btn-ghost">{t.compare.backDest}</Link>
          </div>
        ) : (
          <>
            <section className="plan-panel">
              <div className="compare-cards">
                {selected.map((d, i) => (
                  <div key={d.slug} className={`compare-city-card${i === winnerIdx ? " winner" : ""}`}>
                    {i === winnerIdx && <span className="compare-winner-badge">{t.compare.winner}</span>}
                    <span className="compare-city-emoji">{d.emoji}</span>
                    <h3>{d.name}</h3>
                    <span className="compare-city-country">{d.country}</span>
                    <div className="compare-score-ring">
                      <svg viewBox="0 0 80 80">
                        <circle cx="40" cy="40" r="34" fill="none" stroke="rgba(255,255,255,0.06)" strokeWidth="6" />
                        <circle
                          cx="40" cy="40" r="34" fill="none"
                          stroke="url(#comparePageGrad)" strokeWidth="6"
                          strokeLinecap="round"
                          strokeDasharray={`${scores[i] * 2.14} 214`}
                          transform="rotate(-90 40 40)"
                        />
                      </svg>
                      <span className="compare-score-num">{scores[i]}</span>
                    </div>
                    <Link href={`/destinations/${d.slug}`} className="compare-city-link">{t.common.detail}</Link>
                  </div>
                ))}
              </div>

              <div className="compare-metrics">
                {COMPARE_METRICS.map((m) => {
                  const values = selected.map(m.get);
                  const winIdx = getWinnerIdx(values, m.lowerBetter);
                  const maxVal = Math.max(...values);
                  return (
                    <div key={m.label} className="compare-metric-row">
                      <div className="compare-metric-label">{m.emoji} {m.label}</div>
                      <div className="compare-metric-bars">
                        {selected.map((d, i) => {
                          const val = m.get(d);
                          const pct = maxVal > 0 ? (val / maxVal) * 100 : 0;
                          return (
                            <div key={d.slug} className="compare-bar-item">
                              <div className="compare-bar-header">
                                <span>{d.emoji} {d.name}</span>
                                <span className={i === winIdx ? "compare-best" : ""}>
                                  {i === winIdx && "🏆 "}{m.format(val)}
                                </span>
                              </div>
                              <div className="compare-bar-track">
                                <div
                                  className={`compare-bar-fill${i === winIdx ? " best" : ""}`}
                                  style={{ width: `${pct}%` }}
                                />
                              </div>
                            </div>
                          );
                        })}
                      </div>
                    </div>
                  );
                })}
              </div>

              <div className="compare-page-actions">
                <button type="button" className="btn btn-ghost" onClick={addWinner} disabled={winnerIdx < 0}>
                  {t.compare.addWinner}
                </button>
                <button type="button" className="btn btn-primary" onClick={addAll}>
                  {t.compare.addAll}
                </button>
              </div>
            </section>

            <svg width="0" height="0">
              <defs>
                <linearGradient id="comparePageGrad" x1="0%" y1="0%" x2="100%" y2="0%">
                  <stop offset="0%" stopColor="#FF6B6B" />
                  <stop offset="50%" stopColor="#FFE66D" />
                  <stop offset="100%" stopColor="#4ECDC4" />
                </linearGradient>
              </defs>
            </svg>
          </>
        )}

        <RingNext steps={rings.afterCity} />
      </div>
    </div>
  );
}