"use client";

/**
 * PostScrollCard — Instagram-style post used on the scroll feed.
 *
 * Layout:
 *
 *   ┌───────────────────────────────────────┐
 *   │  ◯ name @handle                  ⋮    │  ← author header (TBD)
 *   ├───────────────────────────────────────┤
 *   │                                       │
 *   │            image carousel             │  ← square, swipeable
 *   │              (or quote)               │     (no-image variant
 *   │                                       │     fills with gradient
 *   │            • ○ ○ ○                    │     panel + serif quote)
 *   ├───────────────────────────────────────┤
 *   │  "Quoted passage shown as caption…"   │  ← truncates with "more"
 *   │  ŚRĪMAD-BHĀGAVATAM — CANTO 4, CH 5    │  ← citation
 *   └───────────────────────────────────────┘
 *
 *   • Multi-image carousel uses native CSS scroll-snap with dot indicators
 *     below; the same primitive CollectionScrollCard uses for posts.
 *   • Long captions clamp to 3 lines until the user expands via "more".
 *   • Owner action cluster (Update background / Delete) sits in the
 *     top-right of the media area, fading in on hover (desktop) and
 *     always visible on touch (mobile).
 */

import { useEffect, useRef, useState } from "react";
import Image from "next/image";
import Link from "next/link";
import { AtSign, ImageIcon, Repeat2 } from "lucide-react";
import { cn } from "@/lib/utils";
import type { Post, PostImage } from "@/lib/social";
import { displaySourceLabel } from "@/lib/source-reference";
import { useMediaQuery } from "@/components/selection-toolbar/shared";
import { UserAvatar } from "@/components/ui/user-avatar";
import { useAuth } from "@/components/auth/auth-provider";
import { postSourceHref, quoteCardBgStyle } from "./post-card-shared";
import { PostActionsFooter } from "./post-actions-footer";
import { PostCardMenu } from "./post-card-menu";
import { FeedFollowButton } from "./feed-follow-button";
import { UpdateBackgroundModal } from "../update-background-modal";
import { MentionsDrawer } from "../mentions-drawer";

export function PostScrollCard({
  post,
  onDelete,
  onUpdated,
  enableFollow = false,
}: {
  post: Post;
  onDelete?: (id: string) => void;
  onUpdated?: (updated: Post) => void;
  /** Home-feed only: show a Follow / Follow back button in the header for
   *  authors the viewer doesn't already follow. Off everywhere else. */
  enableFollow?: boolean;
}) {
  const images = post.images ?? [];
  const hasImages = images.length > 0;
  const sourceHref = postSourceHref(post);
  const isMobile = useMediaQuery("(max-width: 767px)");
  const { user } = useAuth();
  const isAuthor = !!user && user.id === post.user_id;
  const [bgModal, setBgModal] = useState(false);
  const [expanded, setExpanded] = useState(false);
  const [mentionsOpen, setMentionsOpen] = useState(false);
  // Live mention count — seeded from the hydrated post, adjusted when the
  // author edits tags in the drawer, so the icon appears/disappears in place.
  const [mentionCount, setMentionCount] = useState(post.mentions_count ?? 0);

  // The author always gets the mentions entry point (to add/remove); everyone
  // else sees it only when the post actually tags someone.
  const showMentions = mentionCount > 0 || isAuthor;

  // Top-right media overlay: a Mentions icon and the owner-only
  // Update-background button. Delete lives in the header menu.
  const topRight =
    showMentions || onUpdated ? (
      <div className="absolute top-3 right-3 z-10 flex items-center gap-2">
        {showMentions ? (
          <OwnerButton
            label="See who's mentioned"
            onClick={() => setMentionsOpen(true)}
            icon={<AtSign className="size-4" />}
          />
        ) : null}
        {onUpdated ? (
          <OwnerButton
            label="Update background"
            onClick={() => setBgModal(true)}
            icon={<ImageIcon className="size-4" />}
          />
        ) : null}
      </div>
    ) : null;

  return (
    <article
      id={`post-${post.id}`}
      className="rounded-2xl overflow-hidden bg-card ring-1 ring-foreground/10 scroll-mt-20 sm:scroll-mt-24 select-none"
    >
      {/* Reshare attribution — only on rows that are themselves
          reshares. Tappable link → original author's profile. The card
          body below shows the resharer as the author (this row IS the
          resharer's own post — likes, comments, background all belong
          to them, decoupled from the original). */}
      {post.reshared_from_post_id && post.original_author_handle ? (
        <Link
          href={`/u/${post.original_author_handle}`}
          className="inline-flex items-center gap-1.5 px-4 pt-3 text-xs text-muted-foreground hover:text-foreground transition-colors"
        >
          <Repeat2 className="size-3.5" />
          <span>
            Reshared from{" "}
            <span className="font-medium">@{post.original_author_handle}</span>
          </span>
        </Link>
      ) : null}
      {/* Author header — identity on the left, three-dot overflow menu
          on the right (Delete for author, Block/Report for everyone
          else; PostCardMenu hides itself when there are no items). */}
      <header className="flex items-center gap-3 px-4 py-3">
        <UserAvatar
          src={post.author_avatar_url}
          name={post.author_name ?? "Unknown"}
          className="size-9"
        />
        <div className="min-w-0 flex-1">
          <Link
            href={
              post.author_handle ? `/u/${post.author_handle}` : "#"
            }
            className="block text-sm font-semibold text-foreground truncate hover:underline"
          >
            {post.author_name || "Unknown"}
          </Link>
          {post.author_handle ? (
            <span className="block text-xs text-muted-foreground truncate">
              @{post.author_handle}
            </span>
          ) : null}
        </div>
        {enableFollow && post.author_handle && !post.viewer_follows_author ? (
          <FeedFollowButton
            handle={post.author_handle}
            followsYou={!!post.author_follows_viewer}
          />
        ) : null}
        <PostCardMenu post={post} onDelete={onDelete} />
      </header>

      {/* Media — image carousel or gradient-with-quote */}
      <div className="relative">
        {hasImages ? (
          <ImageCarousel images={images} />
        ) : (
          <QuotePanel post={post} />
        )}
        {topRight}
      </div>

      {/* Caption + citation — reference sits directly under the media
          so it's read first, with the action row below it. */}
      <div className="px-4 pt-4 pb-3 space-y-2">
        {hasImages ? (
          // When images carry the visual, the caption sits as text below.
          <Caption
            text={post.caption}
            expanded={expanded}
            onToggle={() => setExpanded((v) => !v)}
          />
        ) : null}
        <Link
          href={sourceHref}
          className="block max-w-full truncate text-[0.7rem] uppercase tracking-[0.2em] font-medium text-muted-foreground hover:text-foreground transition-colors"
        >
          {displaySourceLabel(post.source_url, post.source_title)} →
        </Link>
      </div>

      {/* Action footer — like / comment / reshare on the left, add to
          collection on the right. */}
      <div className="pt-1 pb-2 border-t border-border">
        <PostActionsFooter post={post} />
      </div>

      {onUpdated ? (
        <UpdateBackgroundModal
          open={bgModal}
          onClose={() => setBgModal(false)}
          post={post}
          isMobile={isMobile}
          onUpdated={onUpdated}
        />
      ) : null}

      <MentionsDrawer
        open={mentionsOpen}
        postId={post.id}
        authorId={post.user_id}
        onClose={() => setMentionsOpen(false)}
        onCountChange={(d) => setMentionCount((c) => Math.max(0, c + d))}
      />
    </article>
  );
}

// ─── Pieces ──────────────────────────────────────────────────────────────

function ImageCarousel({ images }: { images: PostImage[] }) {
  const [active, setActive] = useState(0);

  function onScroll(e: React.UIEvent<HTMLDivElement>) {
    const el = e.currentTarget;
    const w = el.offsetWidth;
    if (w === 0) return;
    setActive(Math.round(el.scrollLeft / w));
  }

  if (images.length === 1) {
    return (
      <div className="relative aspect-square bg-muted">
        <Image
          src={images[0].url}
          alt=""
          fill
          sizes="(max-width: 768px) 100vw, 640px"
          className="object-cover"
          unoptimized
        />
      </div>
    );
  }

  return (
    <div className="relative">
      <div
        onScroll={onScroll}
        className={cn(
          "flex overflow-x-auto snap-x snap-mandatory",
          "[scrollbar-width:none] [&::-webkit-scrollbar]:hidden",
        )}
      >
        {images.map((img, i) => (
          <div
            key={img.id}
            className="relative w-full shrink-0 snap-start aspect-square bg-muted"
            aria-roledescription="slide"
            aria-label={`${i + 1} of ${images.length}`}
          >
            <Image
              src={img.url}
              alt=""
              fill
              sizes="(max-width: 768px) 100vw, 640px"
              className="object-cover"
              unoptimized
            />
          </div>
        ))}
      </div>
      <div className="absolute inset-x-0 bottom-3 flex items-center justify-center gap-1.5 pointer-events-none">
        {images.map((_, i) => (
          <span
            key={i}
            aria-hidden
            className={cn(
              "size-1.5 rounded-full transition-all",
              i === active ? "bg-white" : "bg-white/50",
            )}
          />
        ))}
      </div>
    </div>
  );
}

function QuotePanel({ post }: { post: Post }) {
  // No-image post: the entire square is a flat palette-aware surface
  // (pure white on light themes, palette-specific dark on dark themes)
  // with the quote in serif inside. Text uses --foreground so it inverts
  // automatically with the theme.
  return (
    <div
      className="relative aspect-square overflow-hidden select-none"
      style={quoteCardBgStyle()}
    >
      <div className="absolute inset-0 flex flex-col justify-center items-center p-8 sm:p-10 text-center text-foreground">
        <p className="font-[family-name:var(--font-title)] text-xl sm:text-2xl leading-relaxed max-w-md line-clamp-[8] break-words">
          “{post.caption}”
        </p>
      </div>
    </div>
  );
}

function Caption({
  text,
  expanded,
  onToggle,
}: {
  text: string;
  expanded: boolean;
  onToggle: () => void;
}) {
  // We clamp to 3 lines collapsed and expose a "More" toggle only when
  // the clamp is actually hiding something. A char-length heuristic gets
  // this wrong: a 200-char caption can fit cleanly in 3 lines on a wide
  // card (no clipping → "More" would be a false promise). Instead measure
  // scrollHeight vs clientHeight on the clamped <p>. Once we've observed
  // overflow we latch it on so "Show less" stays visible after expansion
  // (where scrollHeight would equal clientHeight and we'd otherwise lose
  // the way back).
  const pRef = useRef<HTMLParagraphElement | null>(null);
  const [overflowed, setOverflowed] = useState(false);

  useEffect(() => {
    if (expanded) return;
    const el = pRef.current;
    if (!el) return;
    const measure = () => {
      // Sub-pixel rounding can leave a 1px gap even when content fits;
      // require a real difference before flagging overflow.
      setOverflowed(el.scrollHeight - el.clientHeight > 1);
    };
    measure();
    const ro = new ResizeObserver(measure);
    ro.observe(el);
    return () => ro.disconnect();
  }, [text, expanded]);

  const showToggle = overflowed || expanded;

  return (
    <div className="text-sm text-foreground leading-relaxed">
      <p
        ref={pRef}
        className={cn(
          "font-[family-name:var(--font-title)] break-words",
          !expanded && "line-clamp-3",
        )}
      >
        “{text}”
      </p>
      {showToggle ? (
        <button
          type="button"
          onClick={onToggle}
          className="mt-1 text-xs font-medium text-muted-foreground hover:text-foreground transition-colors"
        >
          {expanded ? "Show less" : "More"}
        </button>
      ) : null}
    </div>
  );
}


function OwnerButton({
  label,
  onClick,
  icon,
}: {
  label: string;
  onClick: () => void;
  icon: React.ReactNode;
}) {
  return (
    <button
      type="button"
      onClick={onClick}
      aria-label={label}
      title={label}
      className={cn(
        "size-9 rounded-full inline-flex items-center justify-center",
        "bg-black/40 text-white hover:bg-black/60 transition-colors backdrop-blur-sm",
      )}
    >
      {icon}
    </button>
  );
}