import { EditorState, PluginKey, Transaction } from "prosemirror-state";
import { EditorView } from "prosemirror-view";
import { EditorSchema } from "../schema";

/**
 * Helper to provide statically typed wrappers over ProseMirror APIs.
 *
 * Public APIs are bound so can be safely used directly, e.g.
 *
 *     interface PluginState {
 *       myPluginField: string;
 *     }
 *     const { key, getPluginState } = new PluginDescriptor<PluginState>('MyPlugin');
 */
export class PluginDescriptor<PluginState extends {}> {
  public readonly key = new PluginKey(this.name);

  constructor(private readonly name: string) {}

  public setPluginState = (
    env: {
      state: EditorState<EditorSchema>;
      tr?: Transaction<EditorSchema>;
      dispatch?: EditorView<EditorSchema>["dispatch"];
    },
    newPluginState: PluginState | ((prevPluginState: PluginState) => PluginState)
  ): void => {
    const { state, tr = env.state.tr, dispatch } = env;
    const prevPluginState = this.getPluginStateOrThrow(state);
    // https://github.com/Microsoft/TypeScript/issues/26970
    tr.setMeta(this.key, newPluginState instanceof Function ? newPluginState(prevPluginState) : newPluginState);
    if (dispatch !== undefined) {
      dispatch(tr);
    }
  };

  public getPluginState = (source: Transaction<EditorSchema> | EditorState): PluginState | null => {
    const pluginState = source instanceof Transaction ? source.getMeta(this.key) : this.key.getState(source);
    return pluginState != null ? (pluginState as PluginState) : null;
  };

  public getPluginStateOrThrow = (source: Transaction<EditorSchema> | EditorState): PluginState => {
    const pluginState = this.getPluginState(source);
    if (pluginState !== null) {
      return pluginState;
    }
    throw new Error("Missing plugin state");
  };
}