// ascii — byte-class predicates and case folding for the ASCII range.
// Matches Hare's ascii::isdigit family. Bytes outside 0..127 always
// answer `false`. The lexer hot path uses these inline; they are
// expected to inline to a couple of compares.

export fn isdigit(c: u8) bool = {
	if (c < 48u8) { return false; };
	if (c > 57u8) { return false; };
	return true;
};

export fn isupper(c: u8) bool = {
	if (c < 65u8) { return false; };
	if (c > 90u8) { return false; };
	return true;
};

export fn islower(c: u8) bool = {
	if (c < 97u8) { return false; };
	if (c > 122u8) { return false; };
	return true;
};

export fn isalpha(c: u8) bool = {
	if (isupper(c)) { return true; };
	return islower(c);
};

export fn isalnum(c: u8) bool = {
	if (isalpha(c)) { return true; };
	return isdigit(c);
};

// isspace — the C/Hare set: space, tab, NL, VT, FF, CR.
export fn isspace(c: u8) bool = {
	if (c == 32u8) { return true; };	// ' '
	if (c == 9u8)  { return true; };	// '\t'
	if (c == 10u8) { return true; };	// '\n'
	if (c == 11u8) { return true; };	// '\v'
	if (c == 12u8) { return true; };	// '\f'
	if (c == 13u8) { return true; };	// '\r'
	return false;
};

export fn ishex(c: u8) bool = {
	if (isdigit(c)) { return true; };
	if (c >= 65u8) {
		if (c <= 70u8) { return true; };	// 'A'..'F'
	};
	if (c >= 97u8) {
		if (c <= 102u8) { return true; };	// 'a'..'f'
	};
	return false;
};

// digitval — value of `c` as a hex/decimal digit, or -1 if not one.
// Useful when scanning numeric literals.
export fn digitval(c: u8) i32 = {
	if (isdigit(c)) { return (c - 48u8): i32; };
	if (c >= 65u8) {
		if (c <= 70u8) { return ((c - 65u8) + 10u8): i32; };
	};
	if (c >= 97u8) {
		if (c <= 102u8) { return ((c - 97u8) + 10u8): i32; };
	};
	return -1;
};

// isidstart / isidpart — identifier classes used by the lexer.
// Alpha or '_' starts; alnum or '_' continues.
export fn isidstart(c: u8) bool = {
	if (isalpha(c)) { return true; };
	if (c == 95u8) { return true; };	// '_'
	return false;
};

export fn isidpart(c: u8) bool = {
	if (isalnum(c)) { return true; };
	if (c == 95u8) { return true; };
	return false;
};

// tolower / toupper — fold ASCII case. Non-letters pass through.
export fn tolower(c: u8) u8 = {
	if (isupper(c)) { return c + 32u8; };
	return c;
};

export fn toupper(c: u8) u8 = {
	if (islower(c)) { return c - 32u8; };
	return c;
};