use super::sealed::RccPeripheral;
use crate::pac::pwr::vals::Vos;
use crate::pac::rcc::vals::{Hpre, Ppre, Sw};
use crate::pac::{FLASH, PWR, RCC};
use crate::rcc::{set_freqs, Clocks};
use crate::time::Hertz;

const HSI: u32 = 16_000_000;

/// Clocks configuration
#[non_exhaustive]
#[derive(Default)]
pub struct Config {
    pub hse: Option<Hertz>,
    pub bypass_hse: bool,
    pub hclk: Option<Hertz>,
    pub sys_ck: Option<Hertz>,
    pub pclk1: Option<Hertz>,
    pub pclk2: Option<Hertz>,

    pub pll48: bool,
}

unsafe fn setup_pll(
    pllsrcclk: u32,
    use_hse: bool,
    pllsysclk: Option<u32>,
    pll48clk: bool,
) -> PllResults {
    use crate::pac::rcc::vals::{Pllp, Pllsrc};

    let sysclk = pllsysclk.unwrap_or(pllsrcclk);
    if pllsysclk.is_none() && !pll48clk {
        RCC.pllcfgr()
            .modify(|w| w.set_pllsrc(Pllsrc(use_hse as u8)));

        return PllResults {
            use_pll: false,
            pllsysclk: None,
            pll48clk: None,
        };
    }
    // Input divisor from PLL source clock, must result to frequency in
    // the range from 1 to 2 MHz
    let pllm_min = (pllsrcclk + 1_999_999) / 2_000_000;
    let pllm_max = pllsrcclk / 1_000_000;

    // Sysclk output divisor must be one of 2, 4, 6 or 8
    let sysclk_div = core::cmp::min(8, (432_000_000 / sysclk) & !1);

    let target_freq = if pll48clk {
        48_000_000
    } else {
        sysclk * sysclk_div
    };

    // Find the lowest pllm value that minimize the difference between
    // target frequency and the real vco_out frequency.
    let pllm = unwrap!((pllm_min..=pllm_max).min_by_key(|pllm| {
        let vco_in = pllsrcclk / pllm;
        let plln = target_freq / vco_in;
        target_freq - vco_in * plln
    }));

    let vco_in = pllsrcclk / pllm;
    assert!((1_000_000..=2_000_000).contains(&vco_in));

    // Main scaler, must result in >= 100MHz (>= 192MHz for F401)
    // and <= 432MHz, min 50, max 432
    let plln = if pll48clk {
        // try the different valid pllq according to the valid
        // main scaller values, and take the best
        let pllq = unwrap!((4..=9).min_by_key(|pllq| {
            let plln = 48_000_000 * pllq / vco_in;
            let pll48_diff = 48_000_000 - vco_in * plln / pllq;
            let sysclk_diff = (sysclk as i32 - (vco_in * plln / sysclk_div) as i32).abs();
            (pll48_diff, sysclk_diff)
        }));
        48_000_000 * pllq / vco_in
    } else {
        sysclk * sysclk_div / vco_in
    };

    let pllp = (sysclk_div / 2) - 1;

    let pllq = (vco_in * plln + 47_999_999) / 48_000_000;
    let real_pll48clk = vco_in * plln / pllq;

    RCC.pllcfgr().modify(|w| {
        w.set_pllm(pllm as u8);
        w.set_plln(plln as u16);
        w.set_pllp(Pllp(pllp as u8));
        w.set_pllq(pllq as u8);
        w.set_pllsrc(Pllsrc(use_hse as u8));
    });

    let real_pllsysclk = vco_in * plln / sysclk_div;

    PllResults {
        use_pll: true,
        pllsysclk: Some(real_pllsysclk),
        pll48clk: if pll48clk { Some(real_pll48clk) } else { None },
    }
}

unsafe fn flash_setup(sysclk: u32) {
    use crate::pac::flash::vals::Latency;

    // Be conservative with voltage ranges
    const FLASH_LATENCY_STEP: u32 = 30_000_000;

    critical_section::with(|_| {
        FLASH
            .acr()
            .modify(|w| w.set_latency(Latency(((sysclk - 1) / FLASH_LATENCY_STEP) as u8)));
    });
}

pub(crate) unsafe fn init(config: Config) {
    crate::peripherals::PWR::enable();

    if let Some(hse) = config.hse {
        if config.bypass_hse {
            assert!((max::HSE_BYPASS_MIN..=max::HSE_BYPASS_MAX).contains(&hse.0));
        } else {
            assert!((max::HSE_OSC_MIN..=max::HSE_OSC_MAX).contains(&hse.0));
        }
    }

    let pllsrcclk = config.hse.map(|hse| hse.0).unwrap_or(HSI);
    let sysclk = config.sys_ck.map(|sys| sys.0).unwrap_or(pllsrcclk);
    let sysclk_on_pll = sysclk != pllsrcclk;

    assert!((max::SYSCLK_MIN..=max::SYSCLK_MAX).contains(&sysclk));

    let plls = setup_pll(
        pllsrcclk,
        config.hse.is_some(),
        if sysclk_on_pll { Some(sysclk) } else { None },
        config.pll48,
    );

    if config.pll48 {
        let freq = unwrap!(plls.pll48clk);

        assert!((max::PLL_48_CLK as i32 - freq as i32).abs() <= max::PLL_48_TOLERANCE as i32);
    }

    let sysclk = if sysclk_on_pll {
        unwrap!(plls.pllsysclk)
    } else {
        sysclk
    };

    // AHB prescaler
    let hclk = config.hclk.map(|h| h.0).unwrap_or(sysclk);
    let (hpre_bits, hpre_div) = match (sysclk + hclk - 1) / hclk {
        0 => unreachable!(),
        1 => (Hpre::DIV1, 1),
        2 => (Hpre::DIV2, 2),
        3..=5 => (Hpre::DIV4, 4),
        6..=11 => (Hpre::DIV8, 8),
        12..=39 => (Hpre::DIV16, 16),
        40..=95 => (Hpre::DIV64, 64),
        96..=191 => (Hpre::DIV128, 128),
        192..=383 => (Hpre::DIV256, 256),
        _ => (Hpre::DIV512, 512),
    };

    // Calculate real AHB clock
    let hclk = sysclk / hpre_div;

    assert!(hclk <= max::HCLK_MAX);

    let pclk1 = config
        .pclk1
        .map(|p| p.0)
        .unwrap_or_else(|| core::cmp::min(max::PCLK1_MAX, hclk));

    let (ppre1_bits, ppre1) = match (hclk + pclk1 - 1) / pclk1 {
        0 => unreachable!(),
        1 => (0b000, 1),
        2 => (0b100, 2),
        3..=5 => (0b101, 4),
        6..=11 => (0b110, 8),
        _ => (0b111, 16),
    };
    let timer_mul1 = if ppre1 == 1 { 1 } else { 2 };

    // Calculate real APB1 clock
    let pclk1 = hclk / ppre1;
    assert!((max::PCLK1_MIN..=max::PCLK1_MAX).contains(&pclk1));

    let pclk2 = config
        .pclk2
        .map(|p| p.0)
        .unwrap_or_else(|| core::cmp::min(max::PCLK2_MAX, hclk));
    let (ppre2_bits, ppre2) = match (hclk + pclk2 - 1) / pclk2 {
        0 => unreachable!(),
        1 => (0b000, 1),
        2 => (0b100, 2),
        3..=5 => (0b101, 4),
        6..=11 => (0b110, 8),
        _ => (0b111, 16),
    };
    let timer_mul2 = if ppre2 == 1 { 1 } else { 2 };

    // Calculate real APB2 clock
    let pclk2 = hclk / ppre2;
    assert!((max::PCLK2_MIN..=max::PCLK2_MAX).contains(&pclk2));

    flash_setup(sysclk);

    if config.hse.is_some() {
        RCC.cr().modify(|w| {
            w.set_hsebyp(config.bypass_hse);
            w.set_hseon(true);
        });
        while !RCC.cr().read().hserdy() {}
    }

    if plls.use_pll {
        RCC.cr().modify(|w| w.set_pllon(false));

        // enable PWR and setup VOSScale

        RCC.apb1enr().modify(|w| w.set_pwren(true));

        let vos_scale = if sysclk <= 144_000_000 {
            3
        } else if sysclk <= 168_000_000 {
            2
        } else {
            1
        };
        PWR.cr1().modify(|w| {
            w.set_vos(match vos_scale {
                3 => Vos::SCALE3,
                2 => Vos::SCALE2,
                1 => Vos::SCALE1,
                _ => panic!("Invalid VOS Scale."),
            })
        });

        RCC.cr().modify(|w| w.set_pllon(true));

        if hclk > max::HCLK_OVERDRIVE_FREQUENCY {
            PWR.cr1().modify(|w| w.set_oden(true));
            while !PWR.csr1().read().odrdy() {}

            PWR.cr1().modify(|w| w.set_odswen(true));
            while !PWR.csr1().read().odswrdy() {}
        }

        while !RCC.cr().read().pllrdy() {}
    }

    RCC.cfgr().modify(|w| {
        w.set_ppre2(Ppre(ppre2_bits));
        w.set_ppre1(Ppre(ppre1_bits));
        w.set_hpre(hpre_bits);
    });

    // Wait for the new prescalers to kick in
    // "The clocks are divided with the new prescaler factor from 1 to 16 AHB cycles after write"
    cortex_m::asm::delay(16);

    RCC.cfgr().modify(|w| {
        w.set_sw(if sysclk_on_pll {
            Sw::PLL
        } else if config.hse.is_some() {
            Sw::HSE
        } else {
            Sw::HSI
        })
    });

    set_freqs(Clocks {
        sys: Hertz(sysclk),
        apb1: Hertz(pclk1),
        apb2: Hertz(pclk2),

        apb1_tim: Hertz(pclk1 * timer_mul1),
        apb2_tim: Hertz(pclk2 * timer_mul2),

        ahb1: Hertz(hclk),
        ahb2: Hertz(hclk),
        ahb3: Hertz(hclk),

        pll48: plls.pll48clk.map(Hertz),
    });
}

struct PllResults {
    use_pll: bool,
    pllsysclk: Option<u32>,
    pll48clk: Option<u32>,
}

mod max {
    pub(crate) const HSE_OSC_MIN: u32 = 4_000_000;
    pub(crate) const HSE_OSC_MAX: u32 = 26_000_000;
    pub(crate) const HSE_BYPASS_MIN: u32 = 1_000_000;
    pub(crate) const HSE_BYPASS_MAX: u32 = 50_000_000;

    pub(crate) const HCLK_MAX: u32 = 216_000_000;
    pub(crate) const HCLK_OVERDRIVE_FREQUENCY: u32 = 180_000_000;

    pub(crate) const SYSCLK_MIN: u32 = 12_500_000;
    pub(crate) const SYSCLK_MAX: u32 = 216_000_000;

    pub(crate) const PCLK1_MIN: u32 = SYSCLK_MIN;
    pub(crate) const PCLK1_MAX: u32 = SYSCLK_MAX / 4;

    pub(crate) const PCLK2_MIN: u32 = SYSCLK_MIN;
    pub(crate) const PCLK2_MAX: u32 = SYSCLK_MAX / 2;

    // USB specification allows +-0.25%
    pub(crate) const PLL_48_CLK: u32 = 48_000_000;
    pub(crate) const PLL_48_TOLERANCE: u32 = 120_000;
}