"use client";

import { useEffect, useState, type ReactNode } from "react";
import Link from "next/link";
import { useRouter } from "next/navigation";
import { Check, Coins, Loader2, Paperclip } from "lucide-react";
import {
  apiDownloadPostAttachment,
  postAttachmentDownloadURL,
  type PostAttachment,
} from "@/lib/api";
import { fileExtBadge, fileKind } from "@/lib/fileKind";
import { toast } from "@/lib/toast";
import Modal from "@/components/Modal";

function formatSize(n: number) {
  if (n < 1024) return `${n} B`;
  if (n < 1024 * 1024) return `${(n / 1024).toFixed(1)} KB`;
  return `${(n / 1024 / 1024).toFixed(1)} MB`;
}

function formatPoints(n: number) {
  return n.toLocaleString("zh-CN");
}

/** 把已拿到的文件交给浏览器下载栏（付费首次须先 fetch 才能处理 402） */
function triggerBrowserDownload(blob: Blob, filename: string) {
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  a.rel = "noopener";
  document.body.appendChild(a);
  a.click();
  a.remove();
  window.setTimeout(() => URL.revokeObjectURL(url), 30_000);
}

function AttachmentMeta({
  a,
  unlocked,
}: {
  a: PostAttachment;
  unlocked: boolean;
}) {
  const paid = a.price_points > 0;
  return (
    <>
      <span className="j13-att-type" data-kind={fileKind(a.name, a.mime)} aria-hidden>
        {fileExtBadge(a.name)}
      </span>
      <span className="j13-att-main">
        <span className="j13-att-name">{a.name}</span>
        <span className="j13-att-meta">
          {formatSize(a.size)}
          {a.download_count > 0 ? ` · ${a.download_count} 次下载` : ""}
        </span>
      </span>
      <span
        className={`j13-att-price${paid ? (unlocked ? " is-unlocked" : "") : " is-free"}`}
        aria-hidden
      >
        {paid ? (
          <>
            <span className="j13-att-price-num">{formatPoints(a.price_points)}</span>
            <span className="j13-att-price-unit">
              <Coins size={12} strokeWidth={2.4} />
              {unlocked ? "已解锁" : "积分"}
            </span>
          </>
        ) : (
          <span className="j13-att-price-unit">免费</span>
        )}
      </span>
    </>
  );
}

export default function PostAttachments({
  postId,
  items,
  loggedIn,
}: {
  postId: number;
  items: PostAttachment[];
  loggedIn: boolean;
}) {
  const router = useRouter();
  const loginHref = `/login?redirect=${encodeURIComponent(`/post/${postId}`)}`;
  const [busyId, setBusyId] = useState<number | null>(null);
  const [pending, setPending] = useState<PostAttachment | null>(null);
  const [unlockedIds, setUnlockedIds] = useState<number[]>([]);
  const [freshId, setFreshId] = useState<number | null>(null);

  useEffect(() => {
    if (freshId == null) return;
    const t = window.setTimeout(() => setFreshId(null), 900);
    return () => window.clearTimeout(t);
  }, [freshId]);

  if (!items.length) return null;

  const isUnlocked = (a: PostAttachment) => a.unlocked || unlockedIds.includes(a.id);

  /** 付费未解锁：先确认再 fetch，避免积分不足时整页 JSON；成功后交给浏览器下载栏 */
  const downloadPaid = async (a: PostAttachment) => {
    if (busyId != null) return;
    setBusyId(a.id);
    try {
      const res = await apiDownloadPostAttachment(postId, a.id, a.name);
      if (res.status === 401) {
        setPending(null);
        router.push(loginHref);
        return;
      }
      if (res.error || !res.blob) {
        toast(res.error || "下载失败");
        return;
      }
      triggerBrowserDownload(res.blob, res.filename || a.name);
      setPending(null);
      setUnlockedIds((prev) => (prev.includes(a.id) ? prev : [...prev, a.id]));
      setFreshId(a.id);
      toast("已解锁", "ok");
      router.refresh();
    } catch {
      toast("下载失败，请稍后重试");
    } finally {
      setBusyId(null);
    }
  };

  const onPayCta = (a: PostAttachment) => {
    if (busyId != null) return;
    setPending(a);
  };

  return (
    <section className="j13-att" aria-labelledby="j13-att-title">
      <header className="j13-att-head">
        <h2 id="j13-att-title" className="j13-att-title">
          <Paperclip size={15} strokeWidth={2.25} aria-hidden />
          附件
        </h2>
        <span className="meta text-[12.5px]">{items.length} 个文件</span>
      </header>
      <ul className="j13-att-list">
        {items.map((a) => {
          const guestPaid = !loggedIn && a.price_points > 0;
          const unlocked = isUnlocked(a);
          const busy = busyId === a.id;
          const paidLocked = a.price_points > 0 && !unlocked;
          const label = guestPaid
            ? `登录后下载 ${a.name}，需 ${formatPoints(a.price_points)} 积分`
            : paidLocked
              ? `支付 ${formatPoints(a.price_points)} 积分下载 ${a.name}`
              : `下载 ${a.name}`;
          const ctaText = guestPaid
            ? "登录后下载"
            : busy
              ? "处理中…"
              : paidLocked
                ? "支付下载"
                : "下载";
          const className = [
            "j13-att-card",
            a.price_points > 0 ? "is-paid" : "",
            unlocked && a.price_points > 0 ? "is-unlocked" : "",
            busy ? "is-busy" : "",
            freshId === a.id ? "is-fresh" : "",
          ]
            .filter(Boolean)
            .join(" ");
          const ctaClass = `j13-att-cta${paidLocked || guestPaid ? " is-primary" : ""}`;
          const nativeHref = postAttachmentDownloadURL(postId, a.id);
          let cta: ReactNode;
          if (guestPaid) {
            cta = (
              <Link href={loginHref} className={ctaClass} aria-label={label}>
                {ctaText}
              </Link>
            );
          } else if (paidLocked) {
            cta = (
              <button
                type="button"
                className={ctaClass}
                aria-label={label}
                aria-busy={busy || undefined}
                disabled={busyId != null}
                onClick={() => onPayCta(a)}
              >
                {busy ? <Loader2 size={14} className="animate-spin" aria-hidden /> : null}
                {ctaText}
              </button>
            );
          } else {
            cta = (
              <a href={nativeHref} className={ctaClass} aria-label={label} download={a.name}>
                {unlocked && a.price_points > 0 ? <Check size={14} aria-hidden /> : null}
                {ctaText}
              </a>
            );
          }
          return (
            <li key={a.id}>
              <article className={className}>
                <AttachmentMeta a={a} unlocked={unlocked} />
                {cta}
              </article>
            </li>
          );
        })}
      </ul>

      <Modal
        open={!!pending}
        title="确认支付"
        description="支付一次后永久解锁，不重复扣费"
        busy={busyId != null}
        zIndexClass="z-[1100]"
        maxWidthClass="max-w-sm"
        panelClassName="p-5"
        onClose={() => {
          if (busyId != null) return;
          setPending(null);
        }}
        footer={
          <>
            <button
              type="button"
              className="btn btn-line btn-sm"
              disabled={busyId != null}
              onClick={() => {
                if (busyId != null) return;
                setPending(null);
              }}
            >
              取消
            </button>
            <button
              type="button"
              className="btn btn-primary btn-sm"
              disabled={busyId != null || !pending}
              onClick={() => {
                if (!pending) return;
                void downloadPaid(pending);
              }}
            >
              {busyId != null ? (
                <>
                  <Loader2 size={14} className="animate-spin" aria-hidden />
                  处理中…
                </>
              ) : (
                `支付 ${pending ? formatPoints(pending.price_points) : ""} 积分`
              )}
            </button>
          </>
        }
      >
        {pending ? (
          <div className="j13-att-pay">
            <div className="j13-att-pay-file">
              <span
                className="j13-att-type"
                data-kind={fileKind(pending.name, pending.mime)}
                aria-hidden
              >
                {fileExtBadge(pending.name)}
              </span>
              <div className="min-w-0">
                <p className="j13-att-pay-name">{pending.name}</p>
                <p className="meta text-[12px] !mb-0">{formatSize(pending.size)}</p>
              </div>
            </div>
            <div className="j13-att-pay-hero">
              <span className="j13-att-pay-num">{formatPoints(pending.price_points)}</span>
              <span className="j13-att-pay-unit">
                <Coins size={14} strokeWidth={2.4} aria-hidden />
                积分
              </span>
            </div>
          </div>
        ) : null}
      </Modal>
    </section>
  );
}