import type { Position } from "./buffer.js";

export type MarkTransform = {
  readonly start: Position;
  readonly end: Position;
  readonly insertedText: string;
};

/** Named vi marks with deterministic same-line edit transforms. */
export class ViMarks {
  readonly #marks = new Map<string, Position>();

  set(name: string, position: Position): void {
    if (!/^[a-z]$/.test(name))
      throw new RangeError("Vi mark name must be a lowercase letter");
    this.#marks.set(name, { ...position });
  }

  get(name: string): Position | undefined {
    const position = this.#marks.get(name);
    return position === undefined ? undefined : { ...position };
  }

  transform(edit: MarkTransform): void {
    if (edit.start.line !== edit.end.line || edit.insertedText.includes("\n"))
      return;
    const removedLength = edit.end.column - edit.start.column;
    const delta = edit.insertedText.length - removedLength;
    for (const [name, position] of this.#marks) {
      if (
        position.line !== edit.start.line ||
        position.column < edit.start.column
      )
        continue;
      const column =
        position.column < edit.end.column
          ? edit.start.column
          : position.column + delta;
      this.#marks.set(name, { line: position.line, column });
    }
  }
}