import type { Signal } from "@char/aftercare";
import { type ProjectIndex, workspacePath } from "@berry/api/projects.ts";
import { api } from "./client.ts";
import type { Scope } from "./ui.ts";

export type FolderOptions = {
  scope: Scope;
  environment: Signal<string>;
  base: () => string | null;
  projects?: Signal<ProjectIndex>;
};

type Suggestion = { path: string; project?: string; platform?: string };

let nextList = 0;

export function folderInput({ scope, environment, base, projects }: FolderOptions) {
  const id = `folder-options-${++nextList}`;
  const input = (
    <input
      id={`${id}-input`}
      type="text"
      role="combobox"
      aria-autocomplete="list"
      aria-expanded="false"
      aria-controls={id}
      autocomplete="off"
      spellcheck={false}
      placeholder="/path/to/my-directory/"
    />
  ) as HTMLInputElement;
  const list = <div id={id} role="listbox" class="folder-options" /> as HTMLElement;
  const status = <p class="folder-status" role="status" /> as HTMLElement;
  const menu = <div class="folder-menu" hidden>{list}{status}</div> as HTMLElement;
  const element = <div class="folder-input">{input}{menu}</div> as HTMLElement;
  let suggestions: Suggestion[] = [];
  // the last answer for this machine, which stands in, narrowed, while the next is fetched
  let found: string[] = [];
  let selected = -1;
  let revision = 0;
  let timer: ReturnType<typeof setTimeout> | undefined;
  let request: AbortController | undefined;
  let focused = false;

  const draw = () => {
    list.replaceChildren(...suggestions.map((suggestion, index) => (
      <button
        type="button"
        role="option"
        tabIndex={-1}
        id={`${id}-${index}`}
        aria-selected={String(index === selected)}
        title={suggestion.path}
        _onmousedown={(event) => event.preventDefault()}
        _onclick={() => choose(suggestion.path)}
      >
        <span class="folder-path">{suggestion.path}</span>
        {suggestion.project ? <span class="folder-project">{suggestion.project}</span> : []}
      </button>
    )));
    menu.hidden = suggestions.length === 0 && !status.textContent;
    input.setAttribute("aria-expanded", String(suggestions.length > 0));
    if (selected < 0) input.removeAttribute("aria-activedescendant");
    else input.setAttribute("aria-activedescendant", `${id}-${selected}`);
  };
  const cancel = () => {
    revision++;
    clearTimeout(timer);
    request?.abort();
  };
  const close = () => {
    cancel();
    suggestions = [];
    selected = -1;
    status.textContent = "";
    draw();
  };
  const choose = (path: string) => {
    input.value = path;
    input.dispatchEvent(new Event("input", { bubbles: true }));
    close();
  };
  const refresh = () => {
    cancel();
    if (!focused) return close();
    const version = revision;
    const machine = environment.get();
    const prefix = input.value;
    const saved = Object.values(projects?.get() ?? {}).flatMap((project) =>
      project.roots.filter((root) =>
        root.environment === machine &&
        (root.platform === "win32"
          ? root.cwd.toLowerCase().includes(prefix.toLowerCase())
          : root.cwd.includes(prefix))
      ).map((root) => ({ path: root.cwd, project: project.name, platform: root.platform }))
    ).slice(0, 10);
    const merge = (paths: string[]) => [
      ...saved,
      ...paths.filter((path) =>
        !saved.some((item) =>
          workspacePath(item.path, item.platform) === workspacePath(path, item.platform)
        )
      ).map((path) => ({ path })),
    ];
    suggestions = merge(found.filter((path) => path.startsWith(prefix)));
    selected = -1;
    status.textContent = suggestions.length ? "" : "finding folders…";
    draw();
    timer = setTimeout(async () => {
      request = new AbortController();
      const query = new URLSearchParams({ environment: machine, prefix });
      const cwd = base();
      if (cwd) query.set("cwd", cwd);
      try {
        const paths = await api<string[]>(
          "GET",
          `/api/folders?${query}`,
          undefined,
          request.signal,
        );
        if (version !== revision) return;
        found = paths;
        suggestions = merge(paths);
        status.textContent = suggestions.length ? "" : "no matching folders";
        draw();
      } catch (error) {
        if (version !== revision) return;
        status.textContent = (error as Error).message;
        draw();
      }
    }, 120);
  };
  input.addEventListener("focus", () => {
    focused = true;
    refresh();
  });
  input.addEventListener("input", refresh);
  input.addEventListener("blur", () => {
    focused = false;
    close();
  });
  input.addEventListener("keydown", (event) => {
    if (event.key === "Escape" && !menu.hidden) {
      event.preventDefault();
      event.stopImmediatePropagation();
      close();
    } else if ((event.key === "ArrowDown" || event.key === "ArrowUp") && suggestions.length) {
      event.preventDefault();
      selected = selected < 0
        ? event.key === "ArrowDown" ? 0 : suggestions.length - 1
        : (selected + (event.key === "ArrowDown" ? 1 : -1) + suggestions.length) %
          suggestions.length;
      draw();
      list.children[selected]?.scrollIntoView?.({ block: "nearest" });
    } else if (event.key === "Enter" && selected >= 0) {
      event.preventDefault();
      event.stopImmediatePropagation();
      choose(suggestions[selected].path);
    }
  });
  scope.add(
    environment.subscribe(() => {
      found = [];
      refresh();
    }).unsubscribe,
  );
  if (projects) scope.add(projects.subscribe(refresh).unsubscribe);
  scope.add(close);
  return { input, element };
}