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use crate::{
    intervals::{OCTAVE, TONIC},
    math::{gpf, power_of_two},
    ratio::Ratio,
};
use std::ops::{Add, AddAssign};

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub enum Ordinal {
    Otonal,
    Utonal,
}

#[derive(Clone, Copy, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub struct Pitch {
    pub cents: f32,
    pub ratio: Ratio,
    pub limit: i32,
    pub ordinal: Ordinal,
}

pub trait Pitchable {
    fn to_pitch(&self) -> Pitch;
}

impl Pitchable for (i32, i32) {
    fn to_pitch(&self) -> Pitch {
        let ratio = Ratio::new(*self);
        Pitch {
            cents: cents(ratio),
            ratio: flatten(ratio),
            limit: limit(ratio),
            ordinal: determine_ordinal(ratio),
        }
    }
}

impl Pitchable for i32 {
    fn to_pitch(&self) -> Pitch {
        let ratio = Ratio::new((*self, 1));
        Pitch {
            cents: cents(ratio),
            ratio: flatten(ratio),
            limit: limit(ratio),
            ordinal: determine_ordinal(ratio),
        }
    }
}

impl Pitchable for Ratio {
    fn to_pitch(&self) -> Pitch {
        let ratio = flatten(*self);
        Pitch {
            cents: cents(ratio),
            ratio,
            limit: limit(ratio),
            ordinal: determine_ordinal(ratio),
        }
    }
}

impl Pitchable for Pitch {
    fn to_pitch(&self) -> Pitch {
        Pitch {
            cents: self.cents,
            ratio: flatten(self.ratio),
            limit: self.limit,
            ordinal: self.ordinal,
        }
    }
}

impl Add for Pitch {
    type Output = Pitch;

    fn add(self, rhs: Pitch) -> Pitch {
        Pitch::new(self.ratio * rhs.ratio)
    }
}

impl AddAssign for Pitch {
    fn add_assign(&mut self, rhs: Self) {
        *self = *self + rhs;
    }
}

impl Pitch {
    pub fn new<T: Pitchable>(pitchable: T) -> Pitch {
        pitchable.to_pitch()
    }

    pub fn walk(&self, times: i32) -> Vec<Pitch> {
        let mut pitches = vec![Pitch::new((1, 1))];
        for _ in 1..times {
            let last_pitch = pitches.last().unwrap();
            let next_pitch = *last_pitch + *self;
            pitches.push(next_pitch)
        }
        pitches
    }
}

fn cents(ratio: Ratio) -> f32 {
    let cents_per_octave = 1_200f32;
    let ratio_as_float = ratio.numerator as f32 / ratio.denominator as f32;

    (cents_per_octave / 2f32.log10()) * ratio_as_float.log10()
}

fn flatten(ratio: Ratio) -> Ratio {
    let tonic = Ratio::new(TONIC);
    let octave = Ratio::new(OCTAVE);
    let mut r = ratio;
    loop {
        if r > octave {
            r /= octave;
        } else if r < tonic {
            r *= octave;
        } else {
            return r;
        }
    }
}

fn limit(ratio: Ratio) -> i32 {
    let gpf_from_numerator = gpf(ratio.numerator);
    let gpf_from_denominator = gpf(ratio.denominator);

    gpf_from_numerator.max(gpf_from_denominator)
}

pub fn determine_ordinal(ratio: Ratio) -> Ordinal {
    if power_of_two(ratio.denominator) {
        Ordinal::Otonal
    } else {
        Ordinal::Utonal
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::f32;

    fn p(n: i32, d: i32) -> Pitch {
        Pitch::new((n, d))
    }

    #[test]
    fn cents_works() {
        let fifth = Ratio::new((3, 2));
        let value = cents(fifth);
        let abs_diff = (value.abs() - value).abs();

        assert!(abs_diff <= f32::EPSILON);
    }

    #[test]
    fn flatten_works() {
        let a = p(18, 4);

        assert_eq!(a.ratio, Ratio::new((9, 8)));
    }

    #[test]
    fn walk_works() {
        let expected = vec![p(1, 1), p(3, 2), p(9, 8)];
        let actual = Pitch::new((3, 2)).walk(3);

        assert_eq!(expected, actual);
    }
}