import type { BlockNoteEditor } from "../BlockNoteEditor.js";
import {
  getBlocksChangedByTransaction,
  type BlocksChanged,
} from "../../api/getBlocksChangedByTransaction.js";
import { Transaction } from "prosemirror-state";
import { EventEmitter } from "../../util/EventEmitter.js";
import {
  BlockSchema,
  InlineContentSchema,
  StyleSchema,
} from "../../schema/index.js";

/**
 * A function that can be used to unsubscribe from an event.
 */
export type Unsubscribe = () => void;

/**
 * EventManager is a class which manages the events of the editor
 */
export class EventManager<
  BSchema extends BlockSchema,
  I extends InlineContentSchema,
  S extends StyleSchema,
> extends EventEmitter<{
  onChange: [
    ctx: {
      editor: BlockNoteEditor<BSchema, I, S>;
      transaction: Transaction;
      appendedTransactions: Transaction[];
    },
  ];
  onSelectionChange: [
    ctx: { editor: BlockNoteEditor<BSchema, I, S>; transaction: Transaction },
  ];
  onMount: [ctx: { editor: BlockNoteEditor<BSchema, I, S> }];
  onUnmount: [ctx: { editor: BlockNoteEditor<BSchema, I, S> }];
}> {
  constructor(private editor: BlockNoteEditor<BSchema, I, S>) {
    super();
    // We register tiptap events only once the editor is finished initializing
    // otherwise we would be trying to register events on a tiptap editor which does not exist yet
    editor.on("create", () => {
      editor._tiptapEditor.on(
        "update",
        ({ transaction, appendedTransactions }) => {
          this.emit("onChange", { editor, transaction, appendedTransactions });
        },
      );
      editor._tiptapEditor.on("selectionUpdate", ({ transaction }) => {
        this.emit("onSelectionChange", { editor, transaction });
      });
      editor._tiptapEditor.on("mount", () => {
        this.emit("onMount", { editor });
      });
      editor._tiptapEditor.on("unmount", () => {
        this.emit("onUnmount", { editor });
      });
    });
  }

  /**
   * Register a callback that will be called when the editor changes.
   */
  public onChange(
    callback: (
      editor: BlockNoteEditor<BSchema, I, S>,
      ctx: {
        getChanges(): BlocksChanged<BSchema, I, S>;
      },
    ) => void,
    /**
     * If true, the callback will be triggered when the changes are caused by a remote user
     * @default true
     */
    includeUpdatesFromRemote = true,
  ): Unsubscribe {
    const cb = ({
      transaction,
      appendedTransactions,
    }: {
      transaction: Transaction;
      appendedTransactions: Transaction[];
    }) => {
      if (!includeUpdatesFromRemote && isRemoteTransaction(transaction)) {
        // don't trigger the callback if the changes are caused by a remote user
        return;
      }
      callback(this.editor, {
        getChanges() {
          return getBlocksChangedByTransaction<BSchema, I, S>(
            transaction,
            appendedTransactions,
          );
        },
      });
    };
    this.on("onChange", cb);

    return () => {
      this.off("onChange", cb);
    };
  }

  /**
   * Register a callback that will be called when the selection changes.
   */
  public onSelectionChange(
    callback: (editor: BlockNoteEditor<BSchema, I, S>) => void,
    /**
     * If true, the callback will be triggered when the selection changes due to a yjs sync (i.e.: other user was typing)
     */
    includeSelectionChangedByRemote = false,
  ): Unsubscribe {
    const cb = (e: { transaction: Transaction }) => {
      if (
        !includeSelectionChangedByRemote &&
        isRemoteTransaction(e.transaction)
      ) {
        // don't trigger the callback if the selection changed because of a remote user
        return;
      }
      callback(this.editor);
    };

    this.on("onSelectionChange", cb);

    return () => {
      this.off("onSelectionChange", cb);
    };
  }

  /**
   * Register a callback that will be called when the editor is mounted.
   */
  public onMount(
    callback: (ctx: { editor: BlockNoteEditor<BSchema, I, S> }) => void,
  ): Unsubscribe {
    this.on("onMount", callback);

    return () => {
      this.off("onMount", callback);
    };
  }

  /**
   * Register a callback that will be called when the editor is unmounted.
   */
  public onUnmount(
    callback: (ctx: { editor: BlockNoteEditor<BSchema, I, S> }) => void,
  ): Unsubscribe {
    this.on("onUnmount", callback);

    return () => {
      this.off("onUnmount", callback);
    };
  }
}

function isRemoteTransaction(transaction: Transaction): boolean {
  return !!transaction.getMeta("y-sync$");
}