import { useEffect, useId, useState, type FormEvent } from "react";

import type { Asset } from "../../../contracts/studio/contract.ts";
import type { StudioAssetGateway } from "../../../application/ports/studio-asset-gateway.ts";

/** One screenful of candidates; searching, not scrolling, reaches the rest. */
const PAGE_SIZE = 50;

/**
 * A directive attribute value is delimited by double quotes (see
 * `parse-case-content.ts`'s `attributesOf`), so a value containing one would
 * corrupt the directive -- and a raw newline would spill the directive across
 * lines the block-directive parser does not expect inside an attribute. Both
 * are stripped/folded rather than escaped: there is no escape syntax the
 * parser accepts inside a directive attribute.
 */
function attributeValue(raw: string): string {
  return raw.replaceAll('"', "").replace(/\s+/gu, " ").trim();
}

function isAbortError(error: unknown): boolean {
  return error instanceof DOMException && error.name === "AbortError";
}

export function buildEvidenceDirective(
  input: Readonly<{ assetKey: string; alt: string; caption: string; zoom: boolean }>,
): string {
  const key = attributeValue(input.assetKey);
  const alt = attributeValue(input.alt);
  const caption = attributeValue(input.caption);
  return `:::evidence key="${key}" alt="${alt}" caption="${caption}" zoom="${input.zoom}"\n:::`;
}

export function AssetPicker({
  gateway,
  onInsert,
  onAssetsObserved,
}: Readonly<{
  gateway: StudioAssetGateway;
  onInsert: (directive: string) => void;
  /**
   * Every Asset this Picker has *seen* -- the first page, and each search's
   * results -- reported as it arrives. Deliberately not "the Assets to show":
   * the editor screen merges these into a resolution catalog that only grows
   * (`mergeAssetCatalog`), because Instant Preview resolves `:::evidence`
   * directives against that catalog and a narrowing search must never make an
   * already-inserted figure stop rendering. Optional so Task 10 Step 1's
   * original test (which renders `AssetPicker` on its own) keeps passing.
   */
  onAssetsObserved?: (assets: readonly Asset[]) => void;
}>) {
  const [assets, setAssets] = useState<readonly Asset[]>([]);
  const [status, setStatus] = useState<"LOADING" | "ERROR" | "READY">("LOADING");
  // Alignment follow-up, item 2. `searchDraft` is what the author is typing,
  // `q` the query actually submitted -- only `q` is an effect dependency. That
  // is a stronger guarantee than debouncing (zero requests while typing rather
  // than fewer, and no trailing request after the author stops), and it is the
  // pair `document-list.tsx` already uses for the same job.
  const [searchDraft, setSearchDraft] = useState("");
  const [q, setQ] = useState("");
  const searchId = useId();

  useEffect(() => {
    const controller = new AbortController();
    // `RequestOptions.signal` is advisory: an adapter that ignores it still
    // resolves, and an abandoned query's response would then replace the newer
    // one's results. This flag flips synchronously when `q` changes, so an
    // older search can never land last.
    let active = true;
    setStatus("LOADING");
    gateway
      .listAssets(
        { managementStatus: "READY", ...(q ? { q } : {}), limit: PAGE_SIZE },
        { signal: controller.signal },
      )
      .then((page) => {
        if (!active) return;
        setAssets(page.items);
        setStatus("READY");
        onAssetsObserved?.(page.items);
      })
      .catch((error: unknown) => {
        if (!active || isAbortError(error)) return;
        setStatus("ERROR");
      });
    return () => {
      active = false;
      controller.abort();
    };
  }, [gateway, onAssetsObserved, q]);

  // READY만 삽입 후보다. 서버 필터를 신뢰하되 방어적으로 한 번 더 거른다.
  // A query does not relax this: an asset under review is never insertable,
  // however it was found.
  const selectable = assets.filter((asset) => asset.managementStatus === "READY");

  const submitSearch = (event: FormEvent) => {
    event.preventDefault();
    setQ(searchDraft.trim());
  };

  const listMessage = status === "LOADING"
    ? "Asset 목록을 불러오는 중입니다."
    : selectable.length > 0
      ? `삽입할 수 있는 Asset ${selectable.length}개`
      : q
        ? "검색 결과가 없습니다. 다른 검색어를 입력하세요."
        : "삽입할 수 있는 Asset이 없습니다. 먼저 업로드하세요.";

  return <div className="asset-picker">
    {/* The search box stays mounted through the error and empty states: it is
        the only way to reach an asset outside the first page, so removing it
        with the list would strand the author on whatever went wrong. */}
    <form className="asset-picker-search" role="search" onSubmit={submitSearch}>
      <label htmlFor={searchId}>Asset 검색</label>
      <div>
        <input
          id={searchId}
          type="search"
          value={searchDraft}
          placeholder="Asset 키, 파일 이름"
          onChange={(event) => setSearchDraft(event.target.value)}
        />
        <button type="submit">검색</button>
      </div>
    </form>
    {status === "ERROR"
      ? <p className="studio-error" role="alert">Asset 목록을 불러오지 못했습니다.</p>
      : <p className="studio-asset-picker-empty" role="status">{listMessage}</p>}
    {selectable.length > 0 ? <ul>
      {selectable.map((asset) => <li key={asset.id}>
        <button
          type="button"
          onClick={() => onInsert(buildEvidenceDirective({
            assetKey: asset.assetKey,
            alt: asset.decorative ? "" : (asset.altText ?? ""),
            caption: "",
            zoom: asset.kind === "DIAGRAM",
          }))}
        >
          {asset.assetKey}
        </button>
      </li>)}
    </ul> : null}
  </div>;
}