module.exports = grammar({
  name: "cmake",

  rules: {
    source_file: ($) => repeat($._command_invocation),

    _line_ending: ($) => $._newline,
    _seperation: ($) => choice($._space, $._line_ending),
    _space: ($) => /[ \t]+/,
    _newline: ($) => /\n+/,
    ...commands("foreach", "endforeach"),
    identifier: ($) => /[A-Za-z_][A-Za-z0-9_]*/,
    integer: ($) => /[+-]*\d+/,

    escape_sequence: ($) => choice($._escape_identity, $._escape_encoded, $._escape_semicolon),
    _escape_identity: ($) => /\\[^A-Za-z0-9;]/,
    _escape_encoded: ($) => choice("\\t", "\\r", "\\n"),
    _escape_semicolon: ($) => ";",

    variable: ($) => prec.left(repeat1(choice(/[a-zA-Z0-9/_.+-]/, $.escape_sequence))),
    variable_ref: ($) => choice($.normal_var, $.env_var, $.cache_var),
    normal_var: ($) => seq("${", $.variable, "}"),
    env_var: ($) => seq("$ENV{", $.variable, "}"),
    cache_var: ($) => seq("$CACHE{", $.variable, "}"),

    argument: ($) => choice($.bracket_argument, $.quoted_argument, $.unquoted_argument),

    bracket_argument: ($) => seq($._bracket_open, optional($.bracket_content), $._bracket_close),
    _bracket_open: ($) => seq("[", repeat("="), "["),
    bracket_content: ($) => repeat1(/[^\]]/),
    _bracket_close: ($) => seq("]", repeat("="), "]"),

    quoted_argument: ($) => seq('"', optional($.quoted_element), '"'),
    quoted_element: ($) =>
      repeat1(choice($.variable_ref, /[^\\"]/, $.escape_sequence, seq("\\", $._newline))),

    unquoted_argument: ($) => repeat1(choice($.variable_ref, /[^ ()#\"\\]/, $.escape_sequence)),

    arguments: ($) => args($, $.argument),

    foreach_command: ($) =>
      seq($.foreach, "(", args($, $.argument, "IN", "ZIP_LIST", "RANGE", "LISTS", "ITEMS"), ")"),
    endforeach_command: ($) =>
      seq($.endforeach, "(", repeat($._seperation), optional($.argument), ")"),
    foreach_loop: ($) =>
      seq($.foreach_command, repeat($._command_invocation), $.endforeach_command),
    normal_command: ($) =>
      seq($.identifier, "(", repeat($._seperation), optional($.arguments), ")"),

    _command_invocation: ($) => choice($.normal_command, $.foreach_loop),
  },
});

function iregex(s) {
  return new RegExp(
    Array.from(s).reduce((acc, value) => acc + `[${value.toLowerCase()}${value.toUpperCase()}]`, "")
  );
}

function commandName(name) {
  return { [name]: ($) => iregex(name) };
}

function commands(...names) {
  return Object.assign({}, ...names.map(commandName));
}

function args($, ...rules) {
  return seq(
    choice(...rules),
    repeat(prec.left(seq(repeat1($._seperation), optional(choice(...rules)))))
  );
}