export type ReadlineKeymapName = "vi-command" | "vi-insert";

/** A resolved inputrc key sequence binding. */
export type ReadlineBinding =
  | {
      kind: "command";
      command: string;
    }
  | {
      kind: "macro";
      expansion: string;
    }
  | {
      kind: "unbound";
    };

/**
 * Immutable map of canonical inputrc key-sequence strings to bindings.
 * Key-sequence decoding deliberately belongs to the trie layer added later.
 */
export class ReadlineKeymap {
  readonly #bindings: ReadonlyMap<string, ReadlineBinding>;

  private constructor(
    readonly name: ReadlineKeymapName,
    bindings: ReadonlyMap<string, ReadlineBinding>,
  ) {
    this.#bindings = bindings;
  }

  static empty(name: ReadlineKeymapName): ReadlineKeymap {
    return new ReadlineKeymap(name, new Map());
  }

  get size(): number {
    return this.#bindings.size;
  }

  resolve(sequence: string): ReadlineBinding | undefined {
    return this.#bindings.get(sequence);
  }

  withBinding(sequence: string, binding: ReadlineBinding): ReadlineKeymap {
    if (sequence.length === 0) {
      throw new RangeError("A Readline key sequence must not be empty");
    }

    const bindings = new Map(this.#bindings);
    bindings.set(sequence, binding);
    return new ReadlineKeymap(this.name, bindings);
  }

  entries(): ReadonlyArray<readonly [string, ReadlineBinding]> {
    return [...this.#bindings.entries()];
  }
}