use core::f64;
use std::marker::PhantomData;
use std::ops::Add;
use std::ops::AddAssign;
use std::ops::Div;

use serde::ser::SerializeStruct;
use serde::Serializer;

use uom::num_traits;
use uom::si;

pub use si::f64::{Information, Ratio, Time};
pub use si::information::{byte, gibibyte, kibibyte, mebibyte, tebibyte};
pub use si::ratio::ratio;
pub use si::time::{hour, microsecond, millisecond, minute, nanosecond, second};
pub use uom::num_traits::Zero;

pub use units::{InformationUnit, IsUnit, TimeUnit};

mod units;

pub trait FormatQuantity {
    type Unit;

    fn suitable_unit(&self) -> Self::Unit;

    fn format_with_precision(&self, unit: Self::Unit, precision: usize) -> String;
    fn format(&self, unit: Self::Unit) -> String;
    fn format_auto(&self) -> String;
    fn format_value(&self, unit: Self::Unit) -> String;
}

impl FormatQuantity for Time {
    type Unit = TimeUnit;

    fn suitable_unit(&self) -> TimeUnit {
        if *self < Time::new::<millisecond>(1.0) {
            TimeUnit::MicroSecond
        } else if *self < Time::new::<second>(1.0) {
            TimeUnit::MilliSecond
        } else {
            TimeUnit::Second
        }
    }

    /// Format the time duration in the given unit with the given precision.
    fn format_with_precision(&self, u: TimeUnit, precision: usize) -> String {
        u.format(*self, precision)
    }

    /// Format the time duration in the given unit.
    fn format(&self, unit: TimeUnit) -> String {
        let value = self.format_with_precision(unit, unit.preferred_precision());
        format!("{} {}", value, unit.short_name())
    }

    /// Format the given time duration. The unit will be determined automatically.
    fn format_auto(&self) -> String {
        let unit = self.suitable_unit();
        let value = self.format(unit);
        format!("{} {}", value, unit.short_name())
    }

    /// Like `format`, but without displaying the unit.
    fn format_value(&self, unit: TimeUnit) -> String {
        self.format_with_precision(unit, unit.preferred_precision())
    }
}

pub const fn const_time_from_seconds(value: f64) -> Time {
    // Quantity::new in uom is not yet const: https://docs.rs/uom/0.36.0/uom/si/struct.Quantity.html
    Time {
        dimension: PhantomData,
        units: PhantomData,
        value,
    }
}

impl FormatQuantity for Information {
    type Unit = InformationUnit;

    fn suitable_unit(&self) -> InformationUnit {
        if *self < Information::new::<kibibyte>(1.0) {
            InformationUnit::Byte
        } else {
            InformationUnit::KibiByte
        }
    }

    /// Format the information in the given unit with the given precision.
    fn format_with_precision(&self, u: InformationUnit, precision: usize) -> String {
        u.format(*self, precision)
    }

    /// Format the information in the given unit.
    fn format(&self, unit: InformationUnit) -> String {
        let value = self.format_with_precision(unit, unit.preferred_precision());
        format!("{} {}", value, unit.short_name())
    }

    /// Format the given information. The unit will be determined automatically.
    fn format_auto(&self) -> String {
        let unit = self.suitable_unit();
        let value = self.format(unit);
        format!("{} {}", value, unit.short_name())
    }

    /// Like `format`, but without displaying the unit.
    fn format_value(&self, unit: InformationUnit) -> String {
        self.format_with_precision(unit, unit.preferred_precision())
    }
}

pub fn serialize_time<S>(t: &Time, s: S) -> Result<S::Ok, S::Error>
where
    S: Serializer,
{
    let mut state = s.serialize_struct("Time", 3)?;
    state.serialize_field("value", &t.get::<second>())?;
    state.serialize_field("unit", "second")?;
    state.end()
}

pub fn serialize_information<S>(i: &Information, s: S) -> Result<S::Ok, S::Error>
where
    S: Serializer,
{
    let mut state = s.serialize_struct("Information", 3)?;
    state.serialize_field("value", &i.get::<byte>())?;
    state.serialize_field("unit", "byte")?;
    state.end()
}

pub trait UnsafeRawValue {
    fn unsafe_raw_value(&self) -> f64;
    fn unsafe_from_raw_value(value: f64) -> Self;
}

impl UnsafeRawValue for Time {
    fn unsafe_raw_value(&self) -> f64 {
        self.get::<second>()
    }

    fn unsafe_from_raw_value(value: f64) -> Self {
        Time::new::<second>(value)
    }
}

impl UnsafeRawValue for Information {
    fn unsafe_raw_value(&self) -> f64 {
        self.get::<byte>()
    }

    fn unsafe_from_raw_value(value: f64) -> Self {
        Information::new::<byte>(value)
    }
}

macro_rules! quantity_fn {
    ($name:ident, $unwrapped_values:ident, $body:expr) => {
        pub fn $name<Q: UnsafeRawValue>(values: &[Q]) -> Q {
            let $unwrapped_values: Vec<_> = values.iter().map(|q| q.unsafe_raw_value()).collect();
            let result_value = $body;

            Q::unsafe_from_raw_value(result_value)
        }
    };
}

/// A max function that assumes no NaNs and at least one element
pub fn max<V: PartialOrd>(values: impl IntoIterator<Item = V>) -> V {
    values
        .into_iter()
        .max_by(|a, b| a.partial_cmp(b).expect("No NaN values"))
        .expect("'max' requires at least one element")
}

/// A min function that assumes no NaNs and at least one element
pub fn min<V: PartialOrd>(values: impl IntoIterator<Item = V>) -> V {
    values
        .into_iter()
        .min_by(|a, b| a.partial_cmp(b).expect("No NaN values"))
        .expect("'min' requires at least one element")
}

/// A mean function that assumes at least one element
pub fn mean<Q, P>(values: impl IntoIterator<Item = Q>) -> Q
where
    Q: AddAssign + num_traits::Zero + Div<Ratio, Output = P>,
    P: Into<Q>,
{
    let mut sum = Q::zero();
    let mut count = 0;
    for value in values {
        sum += value;
        count += 1;
    }

    let count = Ratio::new::<ratio>(count as f64);
    (sum / count).into()
}

pub fn median<Q, P>(values: impl IntoIterator<Item = Q>) -> Q
where
    Q: Copy + PartialOrd + Add<Output = Q> + Div<Ratio, Output = P>,
    P: Into<Q>,
{
    let mut values = values.into_iter().collect::<Vec<_>>();
    values.sort_by(|a, b| a.partial_cmp(b).expect("No NaN values"));

    let len = values.len();
    if len % 2 == 0 {
        let mid = len / 2;
        let a = &values[mid - 1];
        let b = &values[mid];
        ((*a + *b) / Ratio::new::<ratio>(2.)).into()
    } else {
        values[len / 2]
    }
}

quantity_fn!(standard_deviation, values, {
    let mean_value = statistical::mean(&values);
    statistical::standard_deviation(&values, Some(mean_value))
});

pub fn modified_zscores<Q: UnsafeRawValue>(values: &[Q]) -> Vec<f64> {
    let values: Vec<_> = values.iter().map(|q| q.unsafe_raw_value()).collect();
    crate::outlier_detection::modified_zscores(&values)
}

#[test]
fn test_max() {
    assert_eq!(1.0, max([1.0]));
    assert_eq!(-1.0, max([-1.0]));
    assert_eq!(-1.0, max([-2.0, -1.0]));
    assert_eq!(1.0, max([-1.0, 1.0]));
    assert_eq!(1.0, max([-1.0, 1.0, 0.0]));
}

#[test]
fn test_time() {
    let time = Time::new::<millisecond>(123.4);
    assert_eq!(time.get::<millisecond>(), 123.4);

    let time_s = time.get::<second>();
    approx::assert_relative_eq!(time_s, 0.1234);

    let time_us = time.get::<microsecond>();
    approx::assert_relative_eq!(time_us, 123400.0);
}

#[test]
fn test_information() {
    use uom::si::information::pebibyte;

    let information = Information::new::<kibibyte>(8.);
    assert_eq!(information.get::<byte>(), 8192.);

    let information_kib = information.get::<kibibyte>();
    assert_eq!(information_kib, 8.);

    let largest_exactly_representable = Information::new::<byte>(9_007_199_254_740_992.);
    assert_eq!(largest_exactly_representable.get::<pebibyte>(), 8.);
}

#[test]
fn test_format() {
    let time = Time::new::<millisecond>(123.4);
    assert_eq!(time.format(TimeUnit::Second), "0.123 s");
    assert_eq!(time.format(TimeUnit::MilliSecond), "123.4 ms");
    assert_eq!(time.format(TimeUnit::MicroSecond), "123400.0 µs");

    let peak_memory_usage = Information::new::<kibibyte>(8.);
    assert_eq!(peak_memory_usage.format(InformationUnit::Byte), "8192 B");
    assert_eq!(
        peak_memory_usage.format(InformationUnit::KibiByte),
        "8.0 KiB"
    );
}

#[test]
fn test_mean() {
    let values = vec![
        Time::new::<millisecond>(123.4),
        Time::new::<millisecond>(234.5),
    ];
    let result = mean(values.into_iter());
    assert_eq!(result.format(TimeUnit::MilliSecond), "178.9 ms");
}

#[test]
fn test_suiteable_unit() {
    assert_eq!(Time::new::<second>(1.3).suitable_unit(), TimeUnit::Second);
    assert_eq!(Time::new::<second>(1.0).suitable_unit(), TimeUnit::Second);
    assert_eq!(
        Time::new::<second>(0.999).suitable_unit(),
        TimeUnit::MilliSecond
    );
    assert_eq!(
        Time::new::<second>(0.0005).suitable_unit(),
        TimeUnit::MicroSecond
    );
    assert_eq!(
        Time::new::<second>(0.).suitable_unit(),
        TimeUnit::MicroSecond
    );
    assert_eq!(
        Time::new::<second>(1000.0).suitable_unit(),
        TimeUnit::Second
    );
}

#[test]
fn test_format_duration_unit_with_unit() {
    let out = Time::new::<second>(1.3).format(TimeUnit::Second);
    assert_eq!("1.300 s", out);

    let out = Time::new::<second>(1.3).format(TimeUnit::MilliSecond);
    assert_eq!("1300.0 ms", out);

    let out = Time::new::<second>(1.3).format(TimeUnit::MicroSecond);
    assert_eq!("1300000.0 µs", out);
}

#[test]
fn statistics() {
    let values = vec![
        Time::new::<second>(1.0),
        Time::new::<second>(2.0),
        Time::new::<second>(3.0),
    ];

    assert_eq!(
        mean(values.iter().copied()).format(TimeUnit::Second),
        "2.000 s"
    );
    assert_eq!(
        median(values.iter().copied()).format(TimeUnit::Second),
        "2.000 s"
    );
    assert_eq!(min(&values).format(TimeUnit::Second), "1.000 s");
    assert_eq!(max(&values).format(TimeUnit::Second), "3.000 s");
    assert_eq!(
        standard_deviation(&values).format(TimeUnit::Second),
        "1.000 s"
    );

    let values = vec![
        Information::new::<byte>(1.0),
        Information::new::<byte>(2.0),
        Information::new::<byte>(3.0),
    ];
    mean(values.iter().copied()).format(InformationUnit::Byte);
}