/**
 * PubScript editor React wrapper — the single place that constructs a TipTap
 * editor instance and exposes it to the app.
 *
 * Responsibilities:
 *   - Build the editor once (shared instance, no re-create on re-render).
 *   - Expose a decoration pipeline (`decorations` + `applyEdit`). The current
 *     decoration source is a fake/stub (`emptyDecorationSource`) so the rest
 *     of the app can be built against a stable contract; the real
 *     collaboration source is swapped in later (CHUNK #4).
 *   - Provide `applyEdit` to apply an arbitrary ProseMirror transaction.
 */
import { useEffect, useRef, useState } from "react";
import { useEditor, type UseEditorOptions } from "@tiptap/react";
import {
  DecorationSet,
} from "@tiptap/pm/view";
import type { EditorState, Transaction } from "@tiptap/pm/state";
import type { Editor as TipTapEditor, Content } from "@tiptap/core";

import { createPubScriptEditor, pubScriptExtensions } from "./schema.js";

export type { UseEditorOptions };

/**
 * A collaboration decoration source: the outer set decorates the shared
 * document, the inner set decorates a local, non-shared view. Currently a
 * stub that yields no decorations; the real collaboration source (CHUNK #4)
 * will implement this shape.
 */
export interface PubScriptDecorationSource {
  decorations: DecorationSet;
  innerDecorations: DecorationSet;
}

/**
 * Empty decoration source used as the default until a real collaboration
 * source is wired in (CHUNK #4).
 */
export const emptyDecorationSource: PubScriptDecorationSource = {
  decorations: DecorationSet.empty,
  innerDecorations: DecorationSet.empty,
};

export interface PubScriptEditorHookOptions extends Omit<UseEditorOptions, "extensions" | "onUpdate"> {
  /** Pre-existing editor instance to reuse (avoids re-creating ProseMirror state). */
  editor?: TipTapEditor;
  /** Decoration source to render. Defaults to the empty stub. */
  decorationSource?: PubScriptDecorationSource;
  /** Initial document content (ProseMirror JSON). */
  content?: Content;
  /** Called on every transaction with the live editor instance. */
  onUpdate?: (editor: TipTapEditor) => void;
  /** Whether the editor is editable. */
  editable?: boolean;
}

/**
 * Hook that builds and manages the PubScript editor. Returns the editor
 * instance, the current decoration source, and an `applyEdit` function.
 */
export function usePubScriptEditor(options: PubScriptEditorHookOptions = {}) {
  const {
    editor: sharedEditor,
    decorationSource = emptyDecorationSource,
    content,
    onUpdate,
    editable = true,
    ...useEditorOptions
  } = options;

  const editor = useEditor({
    editable,
    extensions: pubScriptExtensions,
    editorProps: {
      attributes: {
        class: "ps-editor-content",
      },
    },
    ...(content !== undefined ? { content } : {}),
    ...useEditorOptions,
  });

  // If a shared headless instance is provided, mount it into the React wrapper.
  const sharedRef = useRef<TipTapEditor | null>(sharedEditor ?? null);
  sharedRef.current = sharedEditor ?? null;

  useEffect(() => {
    if (sharedRef.current) {
      sharedRef.current.setEditable(editable);
    }
  }, [editable]);

  const [lastState, setLastState] = useState<EditorState | null>(null);

  // Surface updates to consumers and track the latest state.
  const onUpdateRef = useRef(onUpdate);
  useEffect(() => {
    onUpdateRef.current = onUpdate;
  }, [onUpdate]);

  useEffect(() => {
    if (!editor) return;
    const handler = () => {
      setLastState(editor.state);
      onUpdateRef.current?.(editor);
    };
    editor.on("update", handler);
    return () => {
      editor.off("update", handler);
    };
  }, [editor]);

  const applyEdit = (transaction: Transaction) => {
    if (!editor) return;
    editor.view.dispatch(transaction);
  };

  return { editor, decorationSource, lastState, applyEdit };
}

/**
 * Convenience factory for a headless editor instance, shared across the app.
 */
export function createEditorInstance(content?: Content): TipTapEditor {
  return createPubScriptEditor(content === undefined ? {} : { content });
}

export { createPubScriptEditor, pubScriptExtensions };