import { useCallback, useEffect, useMemo, useState } from "react";
import { formatTreeTagDisplay } from "@/lib/treeTagDisplay";
import type { Snippet } from "@/types/snippet";
import type { TagTreeNode } from "@/types/tagTree";
import { SnippetCard } from "@/features/snippets/SnippetCard";
import { TagTreeDialog } from "@/features/tag-tree/TagTreeDialog";
import { NotesToolbar } from "@/features/notes/NotesToolbar";
import type { SortValue } from "@/features/notes/sortOptions";

export function NotesApp() {
  const [query, setQuery] = useState("");
  const [debouncedQuery, setDebouncedQuery] = useState("");
  const [sort, setSort] = useState<SortValue>("updated_desc");
  const [snippets, setSnippets] = useState<Snippet[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [tagTreeOpen, setTagTreeOpen] = useState(false);
  const [tagTreeNodes, setTagTreeNodes] = useState<TagTreeNode[]>([]);
  const [snippetListVersion, setSnippetListVersion] = useState(0);

  useEffect(() => {
    const t = window.setTimeout(() => setDebouncedQuery(query), 300);
    return () => window.clearTimeout(t);
  }, [query]);

  useEffect(() => {
    let cancelled = false;
    void (async () => {
      setLoading(true);
      setError(null);
      try {
        const params = new URLSearchParams();
        if (debouncedQuery.trim()) params.set("q", debouncedQuery.trim());
        params.set("sort", sort);
        const res = await fetch(`/api/snippets?${params.toString()}`);
        if (!res.ok) throw new Error(await res.text());
        const data = (await res.json()) as Snippet[];
        if (!cancelled) setSnippets(data);
      } catch (e) {
        if (!cancelled) setError(e instanceof Error ? e.message : "Laden fehlgeschlagen");
      } finally {
        if (!cancelled) setLoading(false);
      }
    })();
    return () => {
      cancelled = true;
    };
  }, [debouncedQuery, sort, snippetListVersion]);

  const fetchTagTree = useCallback(async () => {
    try {
      const res = await fetch("/api/tag-tree");
      if (!res.ok) return;
      setTagTreeNodes((await res.json()) as TagTreeNode[]);
    } catch {
      /* ignore */
    }
  }, []);

  useEffect(() => {
    void fetchTagTree();
  }, [fetchTagTree]);

  const treeColorByName = useMemo(() => {
    const m: Record<string, string | null> = {};
    for (const n of tagTreeNodes) {
      m[n.name] = n.color;
    }
    return m;
  }, [tagTreeNodes]);

  const treeDisplayByName = useMemo(() => {
    const m: Record<string, string> = {};
    for (const n of tagTreeNodes) {
      m[n.name] = formatTreeTagDisplay(n.name, n.label_prefix ?? null);
    }
    return m;
  }, [tagTreeNodes]);

  const replaceSnippet = useCallback((s: Snippet) => {
    setSnippets(prev => prev.map(x => (x.id === s.id ? s : x)));
  }, []);

  const removeSnippet = useCallback((id: number) => {
    setSnippets(prev => prev.filter(x => x.id !== id));
  }, []);

  const { snippetColumnLeft, snippetColumnRight } = useMemo(() => {
    const left: Snippet[] = [];
    const right: Snippet[] = [];
    snippets.forEach((s, i) => {
      if (i % 2 === 0) left.push(s);
      else right.push(s);
    });
    return { snippetColumnLeft: left, snippetColumnRight: right };
  }, [snippets]);

  const createNew = async () => {
    setError(null);
    try {
      const res = await fetch("/api/snippets", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ title: null, body: "", tags: [] }),
      });
      if (!res.ok) {
        const err = (await res.json().catch(() => null)) as { error?: string } | null;
        throw new Error(err?.error ?? res.statusText);
      }
      const created = (await res.json()) as Snippet;
      setSnippets(prev => [created, ...prev]);
    } catch (e) {
      setError(e instanceof Error ? e.message : "Neues Snippet fehlgeschlagen");
    }
  };

  return (
    <div className="mx-auto flex w-full max-w-6xl flex-col gap-4 px-4 py-4 sm:px-5 xl:max-w-7xl min-[1800px]:max-w-none min-[1800px]:px-6 min-[2200px]:px-10">
      <NotesToolbar
        query={query}
        onQueryChange={setQuery}
        sort={sort}
        onSortChange={setSort}
        tagTreeCount={tagTreeNodes.length}
        onOpenTagTree={() => setTagTreeOpen(true)}
        onCreateNew={() => void createNew()}
      />

      <TagTreeDialog
        open={tagTreeOpen}
        onOpenChange={setTagTreeOpen}
        onChanged={() => {
          void fetchTagTree();
          setSnippetListVersion(v => v + 1);
        }}
      />

      {error ? <p className="text-sm text-destructive">{error}</p> : null}
      {loading ? <p className="text-sm text-muted-foreground">Lade Snippets …</p> : null}

      {!loading && snippets.length === 0 ? (
        <p className="text-center text-sm text-muted-foreground">Keine Snippets. Mit „Neu“ starten.</p>
      ) : null}

      {snippets.length > 0 ? (
        <>
          <div className="flex flex-col gap-2 sm:gap-2.5 min-[1800px]:hidden">
            {snippets.map(s => (
              <SnippetCard
                key={s.id}
                snippet={s}
                treeColorByName={treeColorByName}
                treeDisplayByName={treeDisplayByName}
                onReplace={replaceSnippet}
                onRemove={removeSnippet}
              />
            ))}
          </div>
          <div className="hidden min-[1800px]:flex min-[1800px]:flex-row min-[1800px]:items-start min-[1800px]:gap-x-8">
            <div className="flex min-w-0 flex-1 flex-col gap-4">
              {snippetColumnLeft.map(s => (
                <SnippetCard
                  key={s.id}
                  snippet={s}
                  treeColorByName={treeColorByName}
                  treeDisplayByName={treeDisplayByName}
                  onReplace={replaceSnippet}
                  onRemove={removeSnippet}
                />
              ))}
            </div>
            <div className="flex min-w-0 flex-1 flex-col gap-4">
              {snippetColumnRight.map(s => (
                <SnippetCard
                  key={s.id}
                  snippet={s}
                  treeColorByName={treeColorByName}
                  treeDisplayByName={treeDisplayByName}
                  onReplace={replaceSnippet}
                  onRemove={removeSnippet}
                />
              ))}
            </div>
          </div>
        </>
      ) : null}
    </div>
  );
}