import { defaultKeymap, history, historyKeymap, indentWithTab } from "@codemirror/commands";
import { markdown } from "@codemirror/lang-markdown";
import { indentUnit } from "@codemirror/language";
import { Compartment, type Extension } from "@codemirror/state";
import { placeholder as cmPlaceholder, dropCursor, EditorView, type KeyBinding, keymap } from "@codemirror/view";
import { memoMarkdownExtensions } from "@/utils/memo-markdown-extension";
import { headingDecorations } from "./headingDecorations";
import { liftListItem, sinkListItem } from "./listIndent";
import { tagAutocomplete } from "./tagAutocomplete";
import { tagMentionDecorations } from "./tagMentionDecorations";
import { memoEditorTheme } from "./theme";
import { uploadAnchorField } from "./uploadAnchors";

// Key bindings layered below the autocomplete keymap so the completion popup's
// own Tab/Escape win while it is open. On a list item, Tab/Shift-Tab nest /
// outdent it (marker-aware, CommonMark-valid); elsewhere they fall through to
// indentWithTab's plain indent. Escape blurs the editor so keyboard users keep
// an escape hatch out of the otherwise Tab-trapping editor.
const editorKeys: KeyBinding[] = [
  {
    key: "Escape",
    run: (view) => {
      view.contentDOM.blur();
      return true;
    },
  },
  { key: "Tab", run: sinkListItem },
  { key: "Shift-Tab", run: liftListItem },
];

export interface EditorExtensionsOptions {
  placeholder: string;
  onChange: (markdown: string) => void;
  onFiles: (files: File[], position: number) => void;
  onUpdate: () => void;
  onSubmit: () => void;
  getTags: () => string[];
}

export const placeholderCompartment = new Compartment();

function clipboardFiles(event: ClipboardEvent): File[] {
  const clipboard = event.clipboardData;
  if (!clipboard) return [];

  const itemFiles = Array.from(clipboard.items)
    .filter((item) => item.kind === "file")
    .map((item) => item.getAsFile())
    .filter((file): file is File => file !== null);
  return itemFiles.length > 0 ? itemFiles : Array.from(clipboard.files);
}

export function buildEditorExtensions({
  placeholder,
  onChange,
  onFiles,
  onUpdate,
  onSubmit,
  getTags,
}: EditorExtensionsOptions): Extension[] {
  // Submitting must outrank defaultKeymap's own Mod-Enter (insertBlankLine): the save
  // shortcut ends the memo, it must not also edit the document. Meta and Ctrl are bound
  // explicitly (not via the platform-dependent Mod-) so Cmd+Enter and Ctrl+Enter both
  // submit everywhere, matching the historical window-level shortcut.
  const submit = () => {
    onSubmit();
    return true;
  };
  const submitKeys: KeyBinding[] = [
    { key: "Meta-Enter", run: submit },
    { key: "Ctrl-Enter", run: submit },
  ];

  return [
    // Core editing behavior. These are the pieces from CM6 setup that this memo
    // editor uses, without enabling multi-cursor selection.
    history(),
    dropCursor(),
    // Indent with spaces (markdown), matching the 2-space bullet nesting.
    indentUnit.of("  "),
    markdown({ extensions: memoMarkdownExtensions }),
    ...memoEditorTheme,
    EditorView.lineWrapping,
    // CodeMirror disables native text assistance because it is primarily a code
    // editor. Memos is a prose editor, so restore the browser behavior used by
    // the textarea editor before v0.30. Autocorrect also keeps Windows TSF input
    // out of Chrome's autocorrect-suppression path, which has dropped committed
    // text from the emoji picker.
    EditorView.contentAttributes.of({
      autocorrect: "on",
      autocapitalize: "on",
      spellcheck: "true",
    }),
    placeholderCompartment.of(cmPlaceholder(placeholder)),
    EditorView.domEventHandlers({
      paste: (event, view) => {
        const files = clipboardFiles(event);
        if (files.length === 0) return false;
        onFiles(files, view.state.selection.main.head);
        return true;
      },
      drop: (event, view) => {
        const files = Array.from(event.dataTransfer?.files ?? []);
        if (files.length === 0) return false;
        const position = view.posAtCoords({ x: event.clientX, y: event.clientY }) ?? view.state.selection.main.head;
        onFiles(files, position);
        return true;
      },
    }),
    tagMentionDecorations,
    headingDecorations,
    uploadAnchorField,
    // tagAutocomplete must precede the editing keymap so the completion popup's
    // Enter/Tab/arrow bindings win while it is open.
    tagAutocomplete(getTags),
    keymap.of([...submitKeys, ...editorKeys, indentWithTab, ...defaultKeymap, ...historyKeymap]),
    EditorView.updateListener.of((u) => {
      if (u.docChanged) onChange(u.state.doc.toString());
      // Toolbar active-state depends only on the doc and selection; skip the
      // getActiveFormats tree walk on focus/viewport/measure-only updates.
      if (u.docChanged || u.selectionSet) onUpdate();
    }),
  ];
}