/*
 * SPDX-License-Identifier: MIT OR BlueOak-1.0.0
 * Copyright (c) 2018-2019 Andre Richter <andre.o.richter@gmail.com>
 * Copyright (c) Berkus Decker <berkus+vesper@metta.systems>
 * Original code distributed under MIT, additional changes are under BlueOak-1.0.0
 */

use {
    super::BcmHost,
    crate::platform::MMIODerefWrapper,
    core::marker::PhantomData,
    tock_registers::{
        fields::FieldValue,
        interfaces::{ReadWriteable, Readable, Writeable},
        register_structs,
        registers::{ReadOnly, ReadWrite, WriteOnly},
    },
};

// Descriptions taken from
// https://github.com/raspberrypi/documentation/files/1888662/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf

/// Generates `pub enums` with no variants for each `ident` passed in.
macro states($($name:ident),*) {
$(pub enum $name {  })*
}

// Possible states for a GPIO pin.
states! {
    Uninitialized, Input, Output, Alt
}

register_structs! {
    /// The offsets for each register.
    /// From <https://wiki.osdev.org/Raspberry_Pi_Bare_Bones> and
    /// <https://github.com/raspberrypi/documentation/files/1888662/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf>
    #[allow(non_snake_case)]
    RegisterBlock {
        (0x00 => pub FSEL: [ReadWrite<u32>; 6]), // function select
        (0x18 => __reserved_1),
        (0x1c => pub SET: [WriteOnly<u32>; 2]), // set output pin
        (0x24 => __reserved_2),
        (0x28 => pub CLR: [WriteOnly<u32>; 2]), // clear output pin
        (0x30 => __reserved_3),
        (0x34 => pub LEV: [ReadOnly<u32>; 2]), // get input pin level
        (0x3c => __reserved_4),
        (0x40 => pub EDS: [ReadWrite<u32>; 2]),
        (0x48 => __reserved_5),
        (0x4c => pub REN: [ReadWrite<u32>; 2]),
        (0x54 => __reserved_6),
        (0x58 => pub FEN: [ReadWrite<u32>; 2]),
        (0x60 => __reserved_7),
        (0x64 => pub HEN: [ReadWrite<u32>; 2]),
        (0x6c => __reserved_8),
        (0x70 => pub LEN: [ReadWrite<u32>; 2]),
        (0x78 => __reserved_9),
        (0x7c => pub AREN: [ReadWrite<u32>; 2]),
        (0x84 => __reserved_10),
        (0x88 => pub AFEN: [ReadWrite<u32>; 2]),
        (0x90 => __reserved_11),
        #[cfg(feature = "rpi3")]
        (0x94 => pub PUD: ReadWrite<u32>), // pull up down
        #[cfg(feature = "rpi3")]
        (0x98 => pub PUDCLK: [ReadWrite<u32>; 2]),
        #[cfg(feature = "rpi3")]
        (0xa0 => __reserved_12),
        #[cfg(feature = "rpi4")]
        (0xe4 => PullUpDownControl: [ReadWrite<u32>; 4]),
        (0xf4 => @END),
    }
}

// Hide RegisterBlock from public api.
type Registers = MMIODerefWrapper<RegisterBlock>;

/// Public interface to the GPIO MMIO area
pub struct GPIO {
    registers: Registers,
}

pub const GPIO_START: usize = 0x20_0000;

impl Default for GPIO {
    fn default() -> GPIO {
        // Default RPi3 GPIO base address
        const GPIO_BASE: usize = BcmHost::get_peripheral_address() + GPIO_START;
        unsafe { GPIO::new(GPIO_BASE) }
    }
}

impl GPIO {
    /// # Safety
    ///
    /// Unsafe, duh!
    pub const unsafe fn new(base_addr: usize) -> GPIO {
        GPIO {
            registers: Registers::new(base_addr),
        }
    }

    pub fn get_pin(&self, pin: usize) -> Pin<Uninitialized> {
        unsafe { Pin::new(pin, self.registers.base_addr) }
    }

    #[cfg(feature = "rpi3")]
    pub fn power_off(&self) {
        use crate::arch::loop_delay;

        // power off gpio pins (but not VCC pins)
        for bank in 0..5 {
            self.registers.FSEL[bank].set(0);
        }

        self.registers.PUD.set(0);

        loop_delay(2000);

        self.registers.PUDCLK[0].set(0xffff_ffff);
        self.registers.PUDCLK[1].set(0xffff_ffff);

        loop_delay(2000);

        // flush GPIO setup
        self.registers.PUDCLK[0].set(0);
        self.registers.PUDCLK[1].set(0);
    }

    #[cfg(feature = "rpi4")]
    pub fn power_off(&self) {
        todo!()
    }
}

/// An alternative GPIO function.
#[repr(u8)]
pub enum Function {
    Input = 0b000,
    Output = 0b001,
    Alt0 = 0b100,
    Alt1 = 0b101,
    Alt2 = 0b110,
    Alt3 = 0b111,
    Alt4 = 0b011,
    Alt5 = 0b010,
}

impl ::core::convert::From<Function> for u32 {
    fn from(f: Function) -> Self {
        f as u32
    }
}

/// Pull up/down resistor setup.
#[repr(u8)]
#[derive(PartialEq)]
pub enum PullUpDown {
    None = 0b00,
    Up = 0b01,
    Down = 0b10,
}

impl ::core::convert::From<PullUpDown> for u32 {
    fn from(p: PullUpDown) -> Self {
        p as u32
    }
}

/// A GPIO pin in state `State`.
///
/// The `State` generic always corresponds to an un-instantiable type that is
/// used solely to mark and track the state of a given GPIO pin. A `Pin`
/// structure starts in the `Uninitialized` state and must be transitioned into
/// one of `Input`, `Output`, or `Alt` via the `into_input`, `into_output`, and
/// `into_alt` methods before it can be used.
pub struct Pin<State> {
    pin: usize,
    registers: Registers,
    _state: PhantomData<State>,
}

impl<State> Pin<State> {
    /// Transitions `self` to state `NewState`, consuming `self` and returning a new
    /// `Pin` instance in state `NewState`. This method should _never_ be exposed to
    /// the public!
    #[inline(always)]
    fn transition<NewState>(self) -> Pin<NewState> {
        Pin {
            pin: self.pin,
            registers: self.registers,
            _state: PhantomData,
        }
    }

    #[cfg(feature = "rpi3")]
    pub fn set_pull_up_down(&self, pull: PullUpDown) {
        use crate::arch::loop_delay;

        let bank = self.pin / 32;
        let off = self.pin % 32;

        self.registers.PUD.set(0);

        loop_delay(2000);

        self.registers.PUDCLK[bank].modify(FieldValue::<u32, ()>::new(
            0b1,
            off,
            if pull == PullUpDown::Up { 1 } else { 0 },
        ));

        loop_delay(2000);

        self.registers.PUD.set(0);
        self.registers.PUDCLK[bank].set(0);
    }

    #[cfg(feature = "rpi4")]
    pub fn set_pull_up_down(&self, pull: PullUpDown) {
        let bank = self.pin / 16;
        let off = self.pin % 16;
        self.registers.PullUpDownControl[bank].modify(FieldValue::<u32, ()>::new(
            0b11,
            off * 2,
            pull.into(),
        ));
    }
}

impl Pin<Uninitialized> {
    /// Returns a new GPIO `Pin` structure for pin number `pin`.
    ///
    /// # Panics
    ///
    /// Panics if `pin` > `53`.
    unsafe fn new(pin: usize, base_addr: usize) -> Pin<Uninitialized> {
        if pin > 53 {
            panic!("gpio::Pin::new(): pin {} exceeds maximum of 53", pin);
        }

        Pin {
            registers: Registers::new(base_addr),
            pin,
            _state: PhantomData,
        }
    }

    /// Enables the alternative function `function` for `self`. Consumes self
    /// and returns a `Pin` structure in the `Alt` state.
    pub fn into_alt(self, function: Function) -> Pin<Alt> {
        let bank = self.pin / 10;
        let off = self.pin % 10;
        self.registers.FSEL[bank].modify(FieldValue::<u32, ()>::new(
            0b111,
            off * 3,
            function.into(),
        ));
        self.transition()
    }

    /// Sets this pin to be an _output_ pin. Consumes self and returns a `Pin`
    /// structure in the `Output` state.
    pub fn into_output(self) -> Pin<Output> {
        self.into_alt(Function::Output).transition()
    }

    /// Sets this pin to be an _input_ pin. Consumes self and returns a `Pin`
    /// structure in the `Input` state.
    pub fn into_input(self) -> Pin<Input> {
        self.into_alt(Function::Input).transition()
    }
}

impl Pin<Output> {
    /// Sets (turns on) this pin.
    pub fn set(&mut self) {
        // Guarantees: pin number is between [0; 53] by construction.
        let bank = self.pin / 32;
        let shift = self.pin % 32;
        self.registers.SET[bank].set(1 << shift);
    }

    /// Clears (turns off) this pin.
    pub fn clear(&mut self) {
        // Guarantees: pin number is between [0; 53] by construction.
        let bank = self.pin / 32;
        let shift = self.pin % 32;
        self.registers.CLR[bank].set(1 << shift);
    }
}

pub type Level = bool;

impl Pin<Input> {
    /// Reads the pin's value. Returns `true` if the level is high and `false`
    /// if the level is low.
    pub fn level(&self) -> Level {
        // Guarantees: pin number is between [0; 53] by construction.
        let bank = self.pin / 32;
        let off = self.pin % 32;
        self.registers.LEV[bank].matches_all(FieldValue::<u32, ()>::new(1, off, 1))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test_case]
    fn test_pin_transitions() {
        let mut reg = [0u32; 40];
        let gpio = unsafe { GPIO::new(&mut reg as *mut _ as usize) };

        let _out = gpio.get_pin(1).into_output();
        assert_eq!(reg[0], 0b001_000);
        let _inp = gpio.get_pin(12).into_input();
        assert_eq!(reg[1], 0b000_000_000);
        let _alt = gpio.get_pin(35).into_alt(Function::Alt1);
        assert_eq!(reg[3], 0b101_000_000_000_000_000);
    }

    #[test_case]
    fn test_pin_outputs() {
        let mut reg = [0u32; 40];
        let gpio = unsafe { GPIO::new(&mut reg as *mut _ as usize) };

        let pin = gpio.get_pin(1);
        let mut out = pin.into_output();
        out.set();
        assert_eq!(reg[7], 0b10); // SET pin 1 = 1 << 1
        out.clear();
        assert_eq!(reg[10], 0b10); // CLR pin 1 = 1 << 1

        let pin = gpio.get_pin(35);
        let mut out = pin.into_output();
        out.set();
        assert_eq!(reg[8], 0b1000); // SET pin 35 = 1 << (35 - 32)
        out.clear();
        assert_eq!(reg[11], 0b1000); // CLR pin 35 = 1 << (35 - 32)
    }

    #[test_case]
    fn test_pin_inputs() {
        let mut reg = [0u32; 40];
        let gpio = unsafe { GPIO::new(&mut reg as *mut _ as usize) };

        let pin = gpio.get_pin(1);
        let inp = pin.into_input();
        assert_eq!(inp.level(), false);

        reg[13] = 0b10;

        assert_eq!(inp.level(), true);

        let pin = gpio.get_pin(35);
        let inp = pin.into_input();
        assert_eq!(inp.level(), false);

        reg[14] = 0b1000;

        assert_eq!(inp.level(), true);
    }
}