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

///
/// [PrintError.WriteFailure] occurs when the underlying [io.Writer] implementation failed to write
/// the entirety of a the requested print operation.
///
pub const PrintError = io.AccessError || error {
    WriteFailure,
};

///
/// Named identifiers for number formats used in printing functions.
///
pub const Radix = enum {
    binary,
    tinary,
    quaternary,
    quinary,
    senary,
    septenary,
    octal,
    nonary,
    decimal,
    undecimal,
    duodecimal,
    tridecimal,
    tetradecimal,
    pentadecimal,
    hexadecimal,

    ///
    /// Returns the base number of `radix`.
    ///
    pub fn base(radix: Radix) u8 {
        return switch (radix) {
            .binary => 2,
            .tinary => 3,
            .quaternary => 4,
            .quinary => 5,
            .senary => 6,
            .septenary => 7,
            .octal => 8,
            .nonary => 9,
            .decimal => 10,
            .undecimal => 11,
            .duodecimal => 12,
            .tridecimal => 13,
            .tetradecimal => 14,
            .pentadecimal => 15,
            .hexadecimal => 16,
        };
    }
};

///
/// Writes `value` as a ASCII / UTF-8 encoded integer to `writer`, returning `true` if the full
/// sequence was successfully written, otherwise `false`.
///
/// The `radix` argument identifies which base system to format `value` as.
///
pub fn printInt(writer: io.Writer, radix: Radix, value: anytype) PrintError!void {
    const Int = @TypeOf(value);

    switch (@typeInfo(Int)) {
        .Int => |info| {
            if (value == 0) {
                const zero = "0";

                if ((try writer.write(zero)) != zero.len) return error.WriteFailure;
            } else {
                // Big enough to hold the hexadecimal representation of the integer type, which is
                // the largest number format accomodated for in [Radix].
                var buffer = [_]u8{0} ** (@sizeOf(Int) * (@bitSizeOf(u8) / 4));
                var buffer_count: usize = 0;
                var n1 = value;

                if (info.signedness == .signed and value < 0) {
                    // Negative value.
                    n1 = -value;
                    buffer[0] = '-';
                    buffer_count += 1;
                }

                while (n1 != 0) {
                    const base = radix.base();

                    buffer[buffer_count] = @intCast(u8, (n1 % base) + '0');
                    n1 = (n1 / base);
                    buffer_count += 1;
                }

                for (buffer[0 .. (buffer_count / 2)]) |_, i|
                    io.swap(u8, &buffer[i], &buffer[buffer_count - i - 1]);

                if ((try writer.write(buffer[0 .. buffer_count])) != buffer_count)
                    return error.WriteFailure;
            }
        },

        // Cast comptime int into known-size integer and try again.
        .ComptimeInt => return printInt(writer, radix,
            @intCast(math.IntFittingRange(value, value), value)),

        else => @compileError("`value` must be of type int or comptime_int"),
    }
}

test "printInt" {
    // Max digits to represent a decimal u8 is 3 (i.e. 127 / 255).
    var decimal_buffer = [_]u8{0} ** 3;
    var decimal_stack = stack.Fixed(u8){.buffer = &decimal_buffer};
    var decimal_writer = stack.fixedWriter(&decimal_stack);

    try printInt(decimal_writer, .decimal, 365);
    try testing.expect(decimal_stack.isFull());
}