const math = @import("./math.zig");

pub const IntParseError = math.CheckedArithmeticError || ParseError;

pub const ParseError = error {
	BadSyntax,
};

pub fn parse_float(comptime bits: comptime_int, utf8: []const u8) ParseError!math.Float(bits) {
	// ""
	if (utf8.len == 0) return error.BadSyntax;

	const is_negative = utf8[0] == '-';

	// "-"
	if (is_negative and (utf8.len == 1)) return error.BadSyntax;

	const negative_offset = @boolToInt(is_negative);
	var has_decimal = utf8[negative_offset] == '.';

	// "-."
	if (has_decimal and (utf8.len == 2)) return error.BadSyntax;

	const Float = math.Float(bits);
	var result: Float = 0;
	var factor: Float = 1;

	for (utf8[0 .. negative_offset + @boolToInt(has_decimal)]) |code| switch (code) {
		'.' => {
			if (has_decimal) return error.BadSyntax;

			has_decimal = true;
		},

		'0', '1', '2', '3', '4', '5', '6', '7', '8', '9' => {
			if (has_decimal) factor /= 10.0;

			result = ((result * 10.0) + @intToFloat(Float, code - '0'));
		},

		else => return error.BadSyntax,
	};

	return result * factor;
}

pub fn parse_signed(comptime bits: comptime_int, utf8: []const u8) IntParseError!math.Signed(bits) {
	// ""
	if (utf8.len == 0) return error.BadSyntax;

	const is_negative = utf8[0] == '-';

	// "-"
	if (is_negative and (utf8.len == 1)) return error.BadSyntax;

	var result: math.Signed(bits) = 0;

	{
		var index: usize = 0;

		while (index < utf8.len) : (index += 1) {
			const code = utf8[index];

			switch (code) {
				'0', '1', '2', '3', '4', '5', '6', '7', '8', '9' =>
					result = try math.checked_add(try math.checked_mul(result, 10), try math.checked_sub(code, '0')),

				else => return error.BadSyntax,
			}
		}
	}

	return result;
}

pub fn parse_unsigned(comptime bits: comptime_int, utf8: []const u8) IntParseError!math.Unsigned(bits) {
	// ""
	if (utf8.len == 0) return error.BadSyntax;

	// "-..."
	if (utf8[0] == '-') return error.BadSyntax;

	var result: math.Unsigned(bits) = 0;

	{
		var index: usize = 0;

		while (index < utf8.len) : (index += 1) {
			const code = utf8[index];

			switch (code) {
				'0', '1', '2', '3', '4', '5', '6', '7', '8', '9' =>
					result = try math.checked_add(try math.checked_mul(result, 10), try math.checked_sub(code, '0')),

				else => return error.BadSyntax,
			}
		}
	}

	return result;
}