//! Reset and Clock Control

use core::cmp;

use cast::u32;
use stm32l4::stm32l4x2::{rcc, RCC};

use flash::ACR;
use time::Hertz;

/// Extension trait that constrains the `RCC` peripheral
pub trait RccExt {
    /// Constrains the `RCC` peripheral so it plays nicely with the other abstractions
    fn constrain(self) -> Rcc;
}

impl RccExt for RCC {
    fn constrain(self) -> Rcc {
        Rcc {
            ahb1: AHB1 { _0: () },
            ahb2: AHB2 { _0: () },
            ahb3: AHB3 { _0: () },
            apb1r1: APB1R1 { _0: () },
            apb1r2: APB1R2 { _0: () },
            apb2: APB2 { _0: () },
            bdcr: BDCR { _0: () },
            csr: CSR { _0: () },
            cfgr: CFGR {
                hclk: None,
                pclk1: None,
                pclk2: None,
                sysclk: None,
                pllcfg: None,
            },
        }
    }
}

/// Constrained RCC peripheral
pub struct Rcc {
    /// AMBA High-performance Bus (AHB1) registers
    pub ahb1: AHB1,
    /// AMBA High-performance Bus (AHB2) registers
    pub ahb2: AHB2,
    /// AMBA High-performance Bus (AHB3) registers
    pub ahb3: AHB3,
    /// Advanced Peripheral Bus 1 (APB1) registers
    pub apb1r1: APB1R1,
    /// Advanced Peripheral Bus 1 (APB2) registers
    pub apb1r2: APB1R2,
    /// Advanced Peripheral Bus 2 (APB2) registers
    pub apb2: APB2,
    /// Clock configuration register
    pub cfgr: CFGR,
    /// Backup domain control register
    pub bdcr: BDCR,
    /// Control/Status Register
    pub csr: CSR, 
}

// CSR Control/Status Register
pub struct CSR {
    _0: (),
}

impl CSR {
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn csr(&mut self) -> &rcc::CSR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).csr }
    }
}

// BDCR Backup domain control register registers
pub struct BDCR {
    _0: (),
}

impl BDCR {
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn enr(&mut self) -> &rcc::BDCR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).bdcr }
    }
}

// AMBA High-performance Bus (AHB1) registers
pub struct AHB1 {
    _0: (),
}

impl AHB1 {
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn enr(&mut self) -> &rcc::AHB1ENR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb1enr }
    }
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn rstr(&mut self) -> &rcc::AHB1RSTR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb1rstr }
    }
}

// AMBA High-performance Bus (AHB2) registers
pub struct AHB2 {
    _0: (),
}

impl AHB2 {
    pub(crate) fn enr(&mut self) -> &rcc::AHB2ENR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb2enr }
    }

    pub(crate) fn rstr(&mut self) -> &rcc::AHB2RSTR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb2rstr }
    }
}

// AMBA High-performance Bus (AHB3) registers
pub struct AHB3 {
    _0: (),
}

impl AHB3 {
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn enr(&mut self) -> &rcc::AHB3ENR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb3enr }
    }
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn rstr(&mut self) -> &rcc::AHB3RSTR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).ahb3rstr }
    }
}

/// Advanced Peripheral Bus 1 (APB1) registers
pub struct APB1R1 {
    _0: (),
}

impl APB1R1 {
    pub(crate) fn enr(&mut self) -> &rcc::APB1ENR1 {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb1enr1 }
    }

    pub(crate) fn rstr(&mut self) -> &rcc::APB1RSTR1 {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb1rstr1 }
    }
}

/// Advanced Peripheral Bus 1 (APB1) registers
pub struct APB1R2 {
    _0: (),
}

impl APB1R2 {
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn enr(&mut self) -> &rcc::APB1ENR2 {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb1enr2 }
    }
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn rstr(&mut self) -> &rcc::APB1RSTR2 {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb1rstr2 }
    }
}

/// Advanced Peripheral Bus 2 (APB2) registers
pub struct APB2 {
    _0: (),
}

impl APB2 {
    pub(crate) fn enr(&mut self) -> &rcc::APB2ENR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb2enr }
    }

    pub(crate) fn rstr(&mut self) -> &rcc::APB2RSTR {
        // NOTE(unsafe) this proxy grants exclusive access to this register
        unsafe { &(*RCC::ptr()).apb2rstr }
    }
}

const HSI: u32 = 16_000_000; // Hz

/// Clock configuration
pub struct CFGR {
    hclk: Option<u32>,
    pclk1: Option<u32>,
    pclk2: Option<u32>,
    sysclk: Option<u32>,
    pllcfg: Option<PllConfig>
}

impl CFGR {
    /// Sets a frequency for the AHB bus
    pub fn hclk<F>(mut self, freq: F) -> Self
    where
        F: Into<Hertz>,
    {
        self.hclk = Some(freq.into().0);
        self
    }

    /// Sets a frequency for the APB1 bus
    pub fn pclk1<F>(mut self, freq: F) -> Self
    where
        F: Into<Hertz>,
    {
        self.pclk1 = Some(freq.into().0);
        self
    }

    /// Sets a frequency for the APB2 bus
    pub fn pclk2<F>(mut self, freq: F) -> Self
    where
        F: Into<Hertz>,
    {
        self.pclk2 = Some(freq.into().0);
        self
    }

    /// Sets the system (core) frequency
    pub fn sysclk<F>(mut self, freq: F) -> Self
    where
        F: Into<Hertz>,
    {
        self.sysclk = Some(freq.into().0);
        self
    }

    /// Sets the system (core) frequency with some pll configuration
    pub fn sysclk_with_pll<F>(mut self, freq: F, cfg: PllConfig) -> Self
    where
        F: Into<Hertz>,
    {
        self.pllcfg = Some(cfg);
        self.sysclk = Some(freq.into().0);
        self
    }

    /// Freezes the clock configuration, making it effective
    pub fn freeze(self, acr: &mut ACR) -> Clocks {

        let pllconf = if self.pllcfg.is_none() {
            let plln = (2 * self.sysclk.unwrap_or(HSI)) / HSI;
            let plln = cmp::min(cmp::max(plln, 2), 16);
            if plln == 2 {
                None
            } else {
                // create a best effort pll config, just multiply n
                // TODO should we reject this configuration as the clocks stored in RCC could cause timing issues?
                let conf = PllConfig {
                    m: 0b0,
                    r: 0b0,
                    n: plln as u8
                };
                Some(conf)
            }
            
        } else {
            let conf = self.pllcfg.unwrap();
            Some(conf)
        };

        let sysclk = self.sysclk.unwrap_or(HSI);

        assert!(sysclk <= 80_000_000);

        let hpre_bits = self.hclk
            .map(|hclk| match sysclk / hclk {
                0 => unreachable!(),
                1 => 0b0000,
                2 => 0b1000,
                3...5 => 0b1001,
                6...11 => 0b1010,
                12...39 => 0b1011,
                40...95 => 0b1100,
                96...191 => 0b1101,
                192...383 => 0b1110,
                _ => 0b1111,
            })
            .unwrap_or(0b0000);

        let hclk = sysclk / (1 << (hpre_bits));

        assert!(hclk <= sysclk);

        let ppre1_bits = self.pclk1
            .map(|pclk1| match hclk / pclk1 {
                0 => unreachable!(),
                1 => 0b000,
                2 => 0b100,
                3...5 => 0b101,
                6...11 => 0b110,
                _ => 0b111,
            })
            .unwrap_or(0b000);

        let ppre1 = 1 << (ppre1_bits);
        let pclk1 = hclk / u32(ppre1);

        assert!(pclk1 <= sysclk);

        let ppre2_bits = self.pclk2
            .map(|pclk2| match hclk / pclk2 {
                0 => unreachable!(),
                1 => 0b000,
                2 => 0b100,
                3...5 => 0b101,
                6...11 => 0b110,
                _ => 0b111,
            })
            .unwrap_or(0b000);

        let ppre2 = 1 << (ppre2_bits);
        let pclk2 = hclk / u32(ppre2);

        assert!(pclk2 <= sysclk);

        // adjust flash wait states
        unsafe {
            acr.acr().write(|w| {
                w.latency().bits(if sysclk <= 24_000_000 {
                    0b000
                } else if sysclk <= 48_000_000 {
                    0b001
                } else {
                    0b010
                })
            })
        }

        let rcc = unsafe { &*RCC::ptr() };
        let sysclk_src_bits;
        if let Some(pllconf) = pllconf {
            // use PLL as source
            sysclk_src_bits = 0b11;
            rcc.cr.modify(|_, w| w.pllon().clear_bit());
            while rcc.cr.read().pllrdy().bit_is_set() {}

            let pllsrc_bits = 0b10; // use HSI16 as PLL source
            rcc.cr.write(|w| w.hsion().set_bit());
            while rcc.cr.read().hsirdy().bit_is_clear() {}

            rcc.pllcfgr
            .modify(|_, w| unsafe { 
                w.pllsrc()
                    .bits(pllsrc_bits)
                    .pllm().bits(pllconf.m)
                    .pllr().bits(pllconf.r)
                    .plln().bits(pllconf.n)
            });

            rcc.cr.modify(|_, w| w.pllon().set_bit());
            
            while rcc.cr.read().pllrdy().bit_is_clear() {}

            rcc.pllcfgr.modify(|_, w| w.pllren().set_bit());

            // SW: PLL selected as system clock
            rcc.cfgr.modify(|_, w| unsafe {
                w.ppre2()
                    .bits(ppre2_bits)
                    .ppre1()
                    .bits(ppre1_bits)
                    .hpre()
                    .bits(hpre_bits)
                    .sw()
                    .bits(sysclk_src_bits)
            });
        } else {
            // use HSI as source
            sysclk_src_bits = 0b01;

            rcc.cr.write(|w| w.hsion().set_bit());
            while rcc.cr.read().hsirdy().bit_is_clear() {}

            // SW: HSI selected as system clock
            rcc.cfgr.write(|w| unsafe {
                w.ppre2()
                    .bits(ppre2_bits)
                    .ppre1()
                    .bits(ppre1_bits)
                    .hpre()
                    .bits(hpre_bits)
                    .sw()
                    .bits(sysclk_src_bits)
            });
        }

        while rcc.cfgr.read().sws().bits() != sysclk_src_bits {}

        // Turn on the internal 32khz lsi oscillator
        rcc.csr.modify(|_, w| {
            w.lsion().set_bit()
        });
        // Wait until LSI is running
        while rcc.csr.read().lsirdy().bit_is_clear() {}


        Clocks {
            hclk: Hertz(hclk),
            pclk1: Hertz(pclk1),
            pclk2: Hertz(pclk2),
            ppre1,
            ppre2,
            sysclk: Hertz(sysclk),
        }
    }
}

#[derive(Clone, Copy)]
/// Pll Configuration - Calculation = ((SourceClk / m) * n) / r
pub struct PllConfig {
    /// Main PLL Division factor
    pub m: u8,
    /// Main Pll Multiplication factor
    pub n: u8,
    /// Main PLL division factor for PLLCLK (system clock)
    pub r: u8,
}

/// Frozen clock frequencies
///
/// The existence of this value indicates that the clock configuration can no longer be changed
#[derive(Clone, Copy)]
pub struct Clocks {
    hclk: Hertz,
    pclk1: Hertz,
    pclk2: Hertz,
    // TODO remove `allow`
    #[allow(dead_code)]
    ppre1: u8,
    ppre2: u8,
    sysclk: Hertz,
}

impl Clocks {
    /// Returns the frequency of the AHB
    pub fn hclk(&self) -> Hertz {
        self.hclk
    }

    /// Returns the frequency of the APB1
    pub fn pclk1(&self) -> Hertz {
        self.pclk1
    }

    /// Returns the frequency of the APB2
    pub fn pclk2(&self) -> Hertz {
        self.pclk2
    }

    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn ppre1(&self) -> u8 {
        self.ppre1
    }
    // TODO remove `allow`
    #[allow(dead_code)]
    pub(crate) fn ppre2(&self) -> u8 {
        self.ppre2
    }

    /// Returns the system (core) frequency
    pub fn sysclk(&self) -> Hertz {
        self.sysclk
    }
}