import { useQuery } from "@tanstack/react-query";
import { ArrowLeft, Archive, Eye, EyeOff } from "lucide-react";
import { useMemo, useState } from "react";
import { Link, useLocation, useParams } from "react-router-dom";

import { Button, EmptyState, Spinner } from "@/components/ui";
import { BottomSheet } from "@/components/BottomSheet";
import { PostCard } from "@/features/online/PostCard";
import { PoolFollowButton } from "@/features/follows/PoolFollowButton";
import { api } from "@/lib/api";
import { hasBackend } from "@/lib/backend";
import { cn } from "@/lib/cn";
import { renderDText } from "@/lib/dtext";
import {
  e621ErrorMessage,
  effectiveCredentials,
  fetchPool,
  fetchPostsByIds,
  postIsBlacklisted,
  type E621Pool,
  type E621Post,
} from "@/lib/e621";
import { formatDate } from "@/lib/format";
import { useIsMobile } from "@/lib/useMediaQuery";
import { useE621 } from "@/store/e621";
import { useUi } from "@/store/ui";

const CHUNK_FALLBACK = 100;

async function fetchPostsChunked(
  credentials: ReturnType<typeof effectiveCredentials>,
  ids: number[],
  chunk: number,
  signal?: AbortSignal,
): Promise<E621Post[]> {
  const posts: E621Post[] = [];
  for (let index = 0; index < ids.length; index += chunk) {
    const slice = ids.slice(index, index + chunk);
    posts.push(...(await fetchPostsByIds(credentials, slice, signal)));
  }
  return posts;
}

const categoryBadge: Record<string, string> = {
  series: "border-ctp-mauve/40 bg-ctp-mauve/15 text-ctp-mauve",
  collection: "border-ctp-blue/40 bg-ctp-blue/15 text-ctp-blue",
};

export default function PoolDetailPage() {
  const { poolId = "" } = useParams();
  const id = Number(poolId);
  const location = useLocation();
  const credentials = useE621((state) => state.credentials);
  const blacklist = useE621((state) => state.blacklist);
  const blacklistSet = useMemo(() => new Set(blacklist), [blacklist]);
  const isMobile = useIsMobile();
  const zoom = useUi((state) => state.zoom);
  // Pool posts load in chunks of the user's e621 page size (max 320).
  const e621PerPage = useUi((state) => state.e621PerPage);
  const chunk = Math.min(320, Math.max(24, e621PerPage || CHUNK_FALLBACK));

  const [visibleCount, setVisibleCount] = useState(chunk);
  const [showBlacklisted, setShowBlacklisted] = useState(false);

  const poolQuery = useQuery({
    queryKey: ["e621", "pool", id, credentials?.username ?? ""],
    queryFn: ({ signal }) =>
      fetchPool(effectiveCredentials(credentials), id, signal),
    enabled: Number.isFinite(id) && id > 0,
    staleTime: 5 * 60_000,
  });
  const pool: E621Pool | undefined = poolQuery.data;

  const postIds = useMemo(
    () => (pool?.post_ids ?? []).slice(0, visibleCount),
    [pool, visibleCount],
  );

  const postsQuery = useQuery({
    queryKey: [
      "e621",
      "pool-posts",
      id,
      postIds.join(","),
      credentials?.username ?? "",
    ],
    queryFn: ({ signal }) =>
      fetchPostsChunked(
        effectiveCredentials(credentials),
        postIds,
        chunk,
        signal,
      ),
    enabled: postIds.length > 0,
    staleTime: 5 * 60_000,
  });

  // Keep the pool's own post order, dropping ids e621 no longer serves.
  const orderedPosts = useMemo(() => {
    const byId = new Map<number, E621Post>();
    for (const post of postsQuery.data ?? []) byId.set(post.id, post);
    return postIds
      .map((postIdValue) => byId.get(postIdValue))
      .filter((post): post is E621Post => Boolean(post));
  }, [postsQuery.data, postIds]);

  const md5s = useMemo(
    () => orderedPosts.map((post) => post.file.md5),
    [orderedPosts],
  );
  const lookupQuery = useQuery({
    queryKey: ["library-lookup", md5s.join(",")],
    queryFn: () =>
      api<{ found: string[] }>("/api/files/lookup/", {
        method: "POST",
        json: { md5s },
      }),
    enabled: hasBackend() && md5s.length > 0,
    staleTime: 60_000,
  });
  const inLibrary = useMemo(
    () => new Set(lookupQuery.data?.found ?? []),
    [lookupQuery.data],
  );

  const { shownPosts, hiddenCount } = useMemo(() => {
    if (blacklistSet.size === 0 || showBlacklisted) {
      return { shownPosts: orderedPosts, hiddenCount: 0 };
    }
    const shown: E621Post[] = [];
    let hidden = 0;
    for (const post of orderedPosts) {
      if (postIsBlacklisted(post, blacklistSet).length > 0) {
        hidden += 1;
      } else {
        shown.push(post);
      }
    }
    return { shownPosts: shown, hiddenCount: hidden };
  }, [orderedPosts, blacklistSet, showBlacklisted]);

  if (!Number.isFinite(id) || id <= 0) {
    return (
      <EmptyState
        title="Pool not found"
        description={
          <Link to="/pools" className="text-ctp-blue hover:underline">
            Back to pools
          </Link>
        }
      />
    );
  }

  if (poolQuery.isPending) {
    return (
      <div className="flex justify-center py-24">
        <Spinner className="h-6 w-6" />
      </div>
    );
  }

  if (poolQuery.isError || !pool) {
    return (
      <EmptyState
        title="Could not load this pool"
        description={
          <>
            {e621ErrorMessage(poolQuery.error)}{" "}
            <Link to="/pools" className="text-ctp-blue hover:underline">
              Back to pools
            </Link>
          </>
        }
      />
    );
  }

  const remaining = pool.post_ids.length - postIds.length;

  return (
    <div className="mx-auto flex w-full max-w-6xl flex-col gap-6">
      <header className="flex flex-wrap items-start justify-between gap-4">
        <div className="min-w-0">
          <Link
            to="/pools"
            className="inline-flex items-center gap-1 text-sm text-ctp-subtext0 transition hover:text-ctp-text"
          >
            <ArrowLeft className="h-4 w-4" /> Pools
          </Link>
          <h1 className="mt-2 break-words text-lg font-semibold">
            {pool.name}
          </h1>
          <p className="mt-1 flex flex-wrap items-center gap-2 text-xs text-ctp-overlay0">
            <span
              className={cn(
                "rounded-full border px-1.5 py-0.5 font-mono text-[10px] font-medium capitalize",
                categoryBadge[pool.category] ??
                  "border-ctp-surface1 text-ctp-subtext0",
              )}
            >
              {pool.category}
            </span>
            <span className="font-mono">#{pool.id}</span>
            <span>{pool.post_count} posts</span>
            <span>by {pool.creator_name || `#${pool.creator_id}`}</span>
            <span>· updated {formatDate(pool.updated_at)}</span>
            {!pool.is_active ? (
              <span className="flex items-center gap-1 text-ctp-red">
                <Archive className="h-3 w-3" /> deleted
              </span>
            ) : null}
          </p>
        </div>
        <PoolFollowButton poolId={pool.id} name={pool.name} />
      </header>

      {pool.description.trim() ? (
        isMobile ? (
          <BottomSheet title="Description">
            <div className="text-sm leading-relaxed text-ctp-subtext0">
              {renderDText(pool.description)}
            </div>
          </BottomSheet>
        ) : (
          <section className="rounded-lg border border-ctp-surface0 bg-ctp-base p-4">
            <h2 className="text-sm font-semibold text-ctp-subtext1">
              Description
            </h2>
            <div className="mt-2 text-sm leading-relaxed text-ctp-subtext0">
              {renderDText(pool.description)}
            </div>
          </section>
        )
      ) : null}

      <section className="flex flex-col gap-3">
        <div className="flex flex-wrap items-center justify-between gap-2">
          <h2 className="text-sm font-semibold text-ctp-subtext1">
            Posts{" "}
            <span className="font-mono text-[11px] text-ctp-overlay0">
              {shownPosts.length}
              {hiddenCount > 0 ? ` of ${orderedPosts.length}` : ""}
            </span>
          </h2>
          {hiddenCount > 0 || showBlacklisted ? (
            <button
              type="button"
              onClick={() => setShowBlacklisted((value) => !value)}
              className="inline-flex items-center gap-1.5 text-xs text-ctp-overlay0 transition hover:text-ctp-text"
            >
              {showBlacklisted ? (
                <>
                  <EyeOff className="h-3.5 w-3.5" /> Hide blacklisted
                </>
              ) : (
                <>
                  <Eye className="h-3.5 w-3.5" /> Reveal {hiddenCount}{" "}
                  blacklisted
                </>
              )}
            </button>
          ) : null}
        </div>

        {postsQuery.isPending ? (
          <div className="flex justify-center py-24">
            <Spinner className="h-6 w-6" />
          </div>
        ) : postsQuery.isError ? (
          <EmptyState
            title="Could not load the pool's posts"
            description={e621ErrorMessage(postsQuery.error)}
          />
        ) : shownPosts.length === 0 ? (
          <EmptyState
            title="No posts to show"
            description={
              hiddenCount > 0
                ? "Everything here is blacklisted."
                : "This pool has no available posts."
            }
          />
        ) : (
          <div
            className="grid gap-3"
            style={{
              gridTemplateColumns: `repeat(auto-fill, minmax(${zoom}px, 1fr))`,
            }}
          >
            {shownPosts.map((post) => {
              const blacklisted =
                blacklistSet.size > 0 &&
                postIsBlacklisted(post, blacklistSet).length > 0;
              if (!blacklisted) {
                return (
                  <PostCard
                    key={post.id}
                    post={post}
                    inLibrary={inLibrary.has(post.file.md5)}
                    from={`${location.pathname}${location.search}`}
                  />
                );
              }
              return (
                <div
                  key={post.id}
                  className="min-w-0 rounded-lg ring-1 ring-ctp-red/50"
                  title="Matches your blacklist"
                >
                  <PostCard
                    post={post}
                    inLibrary={inLibrary.has(post.file.md5)}
                    from={`${location.pathname}${location.search}`}
                  />
                </div>
              );
            })}
          </div>
        )}

        {remaining > 0 ? (
          <div className="mt-2 flex justify-center">
            <Button
              variant="secondary"
              disabled={postsQuery.isFetching}
              onClick={() => setVisibleCount((count) => count + chunk)}
            >
              {postsQuery.isFetching
                ? "Loading…"
                : `Load more posts (${remaining} remaining)`}
            </Button>
          </div>
        ) : null}
      </section>
    </div>
  );
}