const registers = packed struct {
    moder: u32,
    otyper: u32,
    ospeedr: u32,
    pupdr: u32,
    idr: u32,
    odr: u32,
    bsrr: u32,
    lckr: u32,
    afr: u64,
    brr: u32,
    ascr: u32,
};

const driver = struct {
    port: *registers,

    const mode = enum(u32) {
        alternate_0 = 0,
        alternate_1,
        alternate_2,
        alternate_3,
        alternate_4,
        alternate_5,
        alternate_6,
        alternate_7,
        alternate_8,
        alternate_9,
        alternate_10,
        alternate_11,
        alternate_12,
        alternate_13,
        alternate_14,
        alternate_15,
        input,
        output,
        analog,
    };

    pub fn set_mode(self: driver, pin: u4, m: mode) void {
        const offset = 2 * @as(u5, pin);
        const moder = self.port.moder & ~(@as(u32, 3) << offset);

        const mask: u32 = switch (m) {
            .input => 0,
            .output => 1,
            .analog => 3,
            else => 2,
        };

        self.port.moder = moder | (mask << offset);

        if (mask == 2) {
            const afr_offset = (4 * @as(u6, pin));
            const afr = self.port.afr & ~(@as(u64, 0xF) << afr_offset);
            self.port.afr = afr | (@as(u64, @intFromEnum(m)) << afr_offset);
        }
    }

    pub fn toggle(self: driver, pin: u4) void {
        self.port.odr ^= @as(u32, 1) << pin;
    }

    pub fn set(self: driver, pin: u4) void {
        self.port.odr |= @as(u32, 1) << pin;
    }

    pub fn clear(self: driver, pin: u4) void {
        self.port.odr &= ~(@as(u32, 1) << pin);
    }

    pub fn write(self: driver, pin: u4, val: bool) void {
        if (val) {
            self.set(pin);
        } else {
            self.clear(pin);
        }
    }

    pub fn read(self: driver, pin: u4) bool {
        return (self.port.idr & @as(u32, 1) << pin) != 0;
    }
};

pub const gpioa = driver { .port = @ptrFromInt(0x48000000) };
pub const gpiob = driver { .port = @ptrFromInt(0x48000400) };
pub const gpioc = driver { .port = @ptrFromInt(0x48000800) };
pub const gpiod = driver { .port = @ptrFromInt(0x48000C00) };
pub const gpioe = driver { .port = @ptrFromInt(0x48001000) };
pub const gpiof = driver { .port = @ptrFromInt(0x48001400) };
pub const gpiog = driver { .port = @ptrFromInt(0x48001800) };
pub const gpioh = driver { .port = @ptrFromInt(0x48001C00) };