import { ReadlineKeymap, type ReadlineKeymapName } from "./keymap.js";

const bindingPattern = /^"((?:\\.|[^"\\])*)":\s*(.+)$/;
const macroPattern = /^"((?:\\.|[^"\\])*)"$/;

/** A source-located error from canonical `bind -p` output. */
export class InputrcParseError extends Error {
  constructor(
    readonly line: number,
    message: string,
  ) {
    super(`Inputrc parse error on line ${line}: ${message}`);
    this.name = "InputrcParseError";
  }
}

/**
 * Parse the stable inputrc-like output emitted by `bind -m <keymap> -p`.
 * This is intentionally narrower than the portable user-inputrc parser: Bash
 * has already resolved includes and conditionals before producing this form.
 */
export function parseCanonicalKeymap(
  name: ReadlineKeymapName,
  source: string,
): ReadlineKeymap {
  let keymap = ReadlineKeymap.empty(name);

  for (const [index, line] of source.split("\n").entries()) {
    const trimmed = line.trim();
    if (trimmed.length === 0 || trimmed.startsWith("#")) continue;

    const binding = trimmed.match(bindingPattern);
    if (binding === null) {
      throw new InputrcParseError(
        index + 1,
        "expected a quoted key sequence binding",
      );
    }

    const sequence = binding[1];
    const value = binding[2]?.trim();
    if (sequence === undefined || value === undefined || value.length === 0) {
      throw new InputrcParseError(
        index + 1,
        "binding is missing a key sequence or value",
      );
    }

    const macro = value.match(macroPattern);
    keymap = keymap.withBinding(
      sequence,
      macro === null
        ? { kind: "command", command: value }
        : { kind: "macro", expansion: macro[1] ?? "" },
    );
  }

  return keymap;
}