use crate::*;
use std::iter::Iterator;

pub const DEFAULT_PPQ: f64 = 96.0;
/// FIXME: remove this and use PPQ from timebase everywhere:
pub const PPQ: usize = 96;

/// A unit of time, represented as an atomic 64-bit float.
///
/// According to https://stackoverflow.com/a/873367, as per IEEE754,
/// every integer between 1 and 2^53 can be represented exactly.
/// This should mean that, even at 192kHz sampling rate, over 1 year of audio
/// can be clocked in microseconds with f64 without losing precision.
pub trait TimeUnit {
    /// Returns current value
    fn get (&self) -> f64;
    /// Sets new value, returns old
    fn set (&self, value: f64) -> f64;
}
/// Implement arithmetic for a unit of time
macro_rules! impl_op {
    ($T:ident, $Op:ident, $method:ident, |$a:ident,$b:ident|{$impl:expr}) => {
        impl $Op<Self> for $T {
            type Output = Self; #[inline] fn $method (self, other: Self) -> Self::Output {
                let $a = self.get(); let $b = other.get(); Self($impl.into())
            }
        }
        impl $Op<usize> for $T {
            type Output = Self; #[inline] fn $method (self, other: usize) -> Self::Output {
                let $a = self.get(); let $b = other as f64; Self($impl.into())
            }
        }
        impl $Op<f64> for $T {
            type Output = Self; #[inline] fn $method (self, other: f64) -> Self::Output {
                let $a = self.get(); let $b = other; Self($impl.into())
            }
        }
    }
}
/// Define and implement a unit of time
macro_rules! impl_time_unit {
    ($T:ident) => {
        impl TimeUnit for $T {
            fn get (&self) -> f64 { self.0.load(Ordering::Relaxed) }
            fn set (&self, value: f64) -> f64 {
                let old = self.get();
                self.0.store(value, Ordering::Relaxed);
                old
            }
        }
        impl_op!($T, Add, add, |a, b|{a + b});
        impl_op!($T, Sub, sub, |a, b|{a - b});
        impl_op!($T, Mul, mul, |a, b|{a * b});
        impl_op!($T, Div, div, |a, b|{a / b});
        impl_op!($T, Rem, rem, |a, b|{a % b});
        impl From<f64>   for $T  { fn from (value: f64)   -> Self { Self(value.into()) } }
        impl From<usize> for $T  { fn from (value: usize) -> Self { Self((value as f64).into()) } }
        impl Into<f64>   for $T  { fn into (self) -> f64   { self.get() } }
        impl Into<usize> for $T  { fn into (self) -> usize { self.get() as usize } }
        impl Into<f64>   for &$T { fn into (self) -> f64   { self.get() } }
        impl Into<usize> for &$T { fn into (self) -> usize { self.get() as usize } }
        impl Clone for $T { fn clone (&self) -> Self { Self(self.get().into()) } }
    }
}

/// Audio sample rate in Hz (samples per second)
#[derive(Debug, Default)] pub struct SampleRate(AtomicF64);
impl_time_unit!(SampleRate);
impl SampleRate {
    /// Return the duration of a sample in microseconds (floating)
    #[inline] pub fn usec_per_sample (&self) -> f64 {
        1_000_000f64 / self.get()
    }
    /// Return the duration of a sample in microseconds (floating)
    #[inline] pub fn sample_per_usec (&self) -> f64 {
        self.get() / 1_000_000f64
    }
    /// Convert a number of samples to microseconds (floating)
    #[inline] pub fn samples_to_usec (&self, samples: f64) -> f64 {
        self.usec_per_sample() * samples
    }
    /// Convert a number of microseconds to samples (floating)
    #[inline] pub fn usecs_to_sample (&self, usecs:   f64) -> f64 {
        self.sample_per_usec() * usecs
    }
}

/// Tempo in beats per minute
#[derive(Debug, Default)] pub struct BeatsPerMinute(AtomicF64);
impl_time_unit!(BeatsPerMinute);

/// MIDI resolution in PPQ (pulses per quarter note)
#[derive(Debug, Default)] pub struct PulsesPerQuaver(AtomicF64);
impl_time_unit!(PulsesPerQuaver);

/// Timestamp in microseconds
#[derive(Debug, Default)] pub struct Microsecond(AtomicF64);
impl_time_unit!(Microsecond);
impl Microsecond {
    #[inline] pub fn format_msu (&self) -> String {
        let usecs              = self.get() as usize;
        let (seconds, msecs)   = (usecs / 1000000, usecs / 1000 % 1000);
        let (minutes, seconds) = (seconds / 60, seconds % 60);
        format!("{minutes}:{seconds:02}:{msecs:03}")
    }
}

/// Timestamp in audio samples
#[derive(Debug, Default)] pub struct SampleCount(AtomicF64);
impl_time_unit!(SampleCount);

/// Timestamp in MIDI pulses
#[derive(Debug, Default)] pub struct Pulse(AtomicF64);
impl_time_unit!(Pulse);

/// Quantization setting for launching clips
#[derive(Debug, Default)] pub struct LaunchSync(AtomicF64);
impl_time_unit!(LaunchSync);

/// Quantization setting for notes
#[derive(Debug, Default)] pub struct Quantize(AtomicF64);
impl_time_unit!(Quantize);

/// Temporal resolutions: sample rate, tempo, MIDI pulses per quaver (beat)
#[derive(Debug, Clone)]
pub struct Timebase {
    /// Audio samples per second
    pub sr:  SampleRate,
    /// MIDI beats per minute
    pub bpm: BeatsPerMinute,
    /// MIDI ticks per beat
    pub ppq: PulsesPerQuaver,
}
impl Timebase {
    /// Specify sample rate, BPM and PPQ
    pub fn new (
        s: impl Into<SampleRate>,
        b: impl Into<BeatsPerMinute>,
        p: impl Into<PulsesPerQuaver>
    ) -> Self {
        Self { sr: s.into(), bpm: b.into(), ppq: p.into() }
    }
    /// Iterate over ticks between start and end.
    #[inline] pub fn pulses_between_samples (&self, start: usize, end: usize) -> TicksIterator {
        TicksIterator { spp: self.samples_per_pulse(), sample: start, start, end }
    }
    /// Return the duration fo a beat in microseconds
    #[inline] pub fn usec_per_beat (&self) -> f64 { 60_000_000f64 / self.bpm.get() }
    /// Return the number of beats in a second
    #[inline] pub fn beat_per_second (&self) -> f64 { self.bpm.get() / 60f64 }
    /// Return the number of microseconds corresponding to a note of the given duration
    #[inline] pub fn note_to_usec (&self, (num, den): (f64, f64)) -> f64 {
        4.0 * self.usec_per_beat() * num / den
    }
    /// Return duration of a pulse in microseconds (BPM-dependent)
    #[inline] pub fn pulse_per_usec (&self) -> f64 { self.ppq.get() / self.usec_per_beat() }
    /// Return duration of a pulse in microseconds (BPM-dependent)
    #[inline] pub fn usec_per_pulse (&self) -> f64 { self.usec_per_beat() / self.ppq.get() }
    /// Return number of pulses to which a number of microseconds corresponds (BPM-dependent)
    #[inline] pub fn usecs_to_pulse (&self, usec: f64) -> f64 { usec * self.pulse_per_usec() }
    /// Convert a number of pulses to a sample number (SR- and BPM-dependent)
    #[inline] pub fn pulses_to_usec (&self, pulse: f64) -> f64 { pulse / self.usec_per_pulse() }
    /// Return number of pulses in a second (BPM-dependent)
    #[inline] pub fn pulses_per_second (&self) -> f64 { self.beat_per_second() * self.ppq.get() }
    /// Return fraction of a pulse to which a sample corresponds (SR- and BPM-dependent)
    #[inline] pub fn pulses_per_sample (&self) -> f64 {
        self.usec_per_pulse() / self.sr.usec_per_sample()
    }
    /// Return number of samples in a pulse (SR- and BPM-dependent)
    #[inline] pub fn samples_per_pulse (&self) -> f64 {
        self.sr.get() / self.pulses_per_second()
    }
    /// Convert a number of pulses to a sample number (SR- and BPM-dependent)
    #[inline] pub fn pulses_to_sample (&self, p: f64) -> f64 {
        self.pulses_per_sample() * p
    }
    /// Convert a number of samples to a pulse number (SR- and BPM-dependent)
    #[inline] pub fn samples_to_pulse (&self, s: f64) -> f64 {
        s / self.pulses_per_sample()
    }
    /// Return the number of samples corresponding to a note of the given duration
    #[inline] pub fn note_to_samples (&self, note: (f64, f64)) -> f64 {
        self.usec_to_sample(self.note_to_usec(note))
    }
    /// Return the number of samples corresponding to the given number of microseconds
    #[inline] pub fn usec_to_sample (&self, usec: f64) -> f64 {
        usec * self.sr.get() / 1000f64
    }
    /// Return the quantized position of a moment in time given a step
    #[inline] pub fn quantize (&self, step: (f64, f64), time: f64) -> (f64, f64) {
        let step = self.note_to_usec(step);
        (time / step, time % step)
    }
    /// Quantize a collection of events
    #[inline] pub fn quantize_into <E: Iterator<Item=(f64, f64)> + Sized, T> (
        &self, step: (f64, f64), events: E
    ) -> Vec<(f64, f64)> {
        events.map(|(time, event)|(self.quantize(step, time).0, event)).collect()
    }
    /// Format a number of pulses into Beat.Bar.Pulse starting from 0
    #[inline] pub fn format_beats_0 (&self, pulse: f64) -> String {
        let pulse = pulse as usize;
        let ppq   = self.ppq.get() as usize;
        let (beats, pulses) = if ppq > 0 { (pulse / ppq, pulse % ppq) } else { (0, 0) };
        format!("{}.{}.{pulses:02}", beats / 4, beats % 4)
    }
    /// Format a number of pulses into Beat.Bar starting from 0
    #[inline] pub fn format_beats_0_short (&self, pulse: f64) -> String {
        let pulse = pulse as usize;
        let ppq   = self.ppq.get() as usize;
        let beats = if ppq > 0 { pulse / ppq } else { 0 };
        format!("{}.{}", beats / 4, beats % 4)
    }
    /// Format a number of pulses into Beat.Bar.Pulse starting from 1
    #[inline] pub fn format_beats_1 (&self, pulse: f64) -> String {
        let pulse = pulse as usize;
        let ppq   = self.ppq.get() as usize;
        let (beats, pulses) = if ppq > 0 { (pulse / ppq, pulse % ppq) } else { (0, 0) };
        format!("{}.{}.{pulses:02}", beats / 4 + 1, beats % 4 + 1)
    }
    /// Format a number of pulses into Beat.Bar.Pulse starting from 1
    #[inline] pub fn format_beats_1_short (&self, pulse: f64) -> String {
        let pulse = pulse as usize;
        let ppq   = self.ppq.get() as usize;
        let beats = if ppq > 0 { pulse / ppq } else { 0 };
        format!("{}.{}", beats / 4 + 1, beats % 4 + 1)
    }
}
impl Default for Timebase {
    fn default () -> Self { Self::new(48000f64, 150f64, DEFAULT_PPQ) }
}
/// A point in time in all time scales (microsecond, sample, MIDI pulse)
#[derive(Debug, Default, Clone)]
pub struct Instant {
    pub timebase: Arc<Timebase>,
    /// Current time in microseconds
    pub usec:   Microsecond,
    /// Current time in audio samples
    pub sample: SampleCount,
    /// Current time in MIDI pulses
    pub pulse:  Pulse,
}
impl Instant {
    pub fn zero (timebase: &Arc<Timebase>) -> Self {
        Self { usec: 0.into(), sample: 0.into(), pulse: 0.into(), timebase: timebase.clone() }
    }
    pub fn from_usec (timebase: &Arc<Timebase>, usec: f64) -> Self {
        Self {
            usec:     usec.into(),
            sample:   timebase.sr.usecs_to_sample(usec).into(),
            pulse:    timebase.usecs_to_pulse(usec).into(),
            timebase: timebase.clone(),
        }
    }
    pub fn from_sample (timebase: &Arc<Timebase>, sample: f64) -> Self {
        Self {
            sample:   sample.into(),
            usec:     timebase.sr.samples_to_usec(sample).into(),
            pulse:    timebase.samples_to_pulse(sample).into(),
            timebase: timebase.clone(),
        }
    }
    pub fn from_pulse (timebase: &Arc<Timebase>, pulse: f64) -> Self {
        Self {
            pulse:    pulse.into(),
            sample:   timebase.pulses_to_sample(pulse).into(),
            usec:     timebase.pulses_to_usec(pulse).into(),
            timebase: timebase.clone(),
        }
    }
    #[inline] pub fn update_from_usec (&self, usec: f64) {
        self.usec.set(usec);
        self.pulse.set(self.timebase.usecs_to_pulse(usec));
        self.sample.set(self.timebase.sr.usecs_to_sample(usec));
    }
    #[inline] pub fn update_from_sample (&self, sample: f64) {
        self.usec.set(self.timebase.sr.samples_to_usec(sample));
        self.pulse.set(self.timebase.samples_to_pulse(sample));
        self.sample.set(sample);
    }
    #[inline] pub fn update_from_pulse (&self, pulse: f64) {
        self.usec.set(self.timebase.pulses_to_usec(pulse));
        self.pulse.set(pulse);
        self.sample.set(self.timebase.pulses_to_sample(pulse));
    }
    #[inline] pub fn format_beat (&self) -> String {
        self.timebase.format_beats_1(self.pulse.get())
    }
}
/// Iterator that emits subsequent ticks within a range.
pub struct TicksIterator {
    spp:    f64,
    sample: usize,
    start:  usize,
    end:    usize,
}
impl Iterator for TicksIterator {
    type Item = (usize, usize);
    fn next (&mut self) -> Option<Self::Item> {
        loop {
            if self.sample > self.end { return None }
            let spp    = self.spp;
            let sample = self.sample as f64;
            let start  = self.start;
            let end    = self.end;
            self.sample += 1;
            //println!("{spp} {sample} {start} {end}");
            let jitter = sample.rem_euclid(spp); // ramps
            let next_jitter = (sample + 1.0).rem_euclid(spp);
            if jitter > next_jitter { // at crossing:
                let time = (sample as usize) % (end as usize-start as usize);
                let tick = (sample / spp) as usize;
                return Some((time, tick))
            }
        }
    }
}

/// (pulses, name), assuming 96 PPQ
pub const NOTE_DURATIONS: [(usize, &str);26] = [
    (1,    "1/384"),
    (2,    "1/192"),
    (3,    "1/128"),
    (4,    "1/96"),
    (6,    "1/64"),
    (8,    "1/48"),
    (12,   "1/32"),
    (16,   "1/24"),
    (24,   "1/16"),
    (32,   "1/12"),
    (48,   "1/8"),
    (64,   "1/6"),
    (96,   "1/4"),
    (128,  "1/3"),
    (192,  "1/2"),
    (256,  "2/3"),
    (384,  "1/1"),
    (512,  "4/3"),
    (576,  "3/2"),
    (768,  "2/1"),
    (1152, "3/1"),
    (1536, "4/1"),
    (2304, "6/1"),
    (3072, "8/1"),
    (3456, "9/1"),
    (6144, "16/1"),
];
/// Returns the next shorter length
pub fn prev_note_length (pulses: usize) -> usize {
    for i in 1..=16 { let length = NOTE_DURATIONS[16-i].0; if length < pulses { return length } }
    pulses
}
/// Returns the next longer length
pub fn next_note_length (pulses: usize) -> usize {
    for (length, _) in &NOTE_DURATIONS { if *length > pulses { return *length } }
    pulses
}
pub fn pulses_to_name (pulses: usize) -> &'static str {
    for (length, name) in &NOTE_DURATIONS { if *length == pulses { return name } }
    ""
}
#[cfg(test)]
mod test {
    use super::*;
    #[test]
    fn test_samples_to_ticks () {
        let ticks = Ticks(12.3).between_samples(0, 100).collect::<Vec<_>>();
        println!("{ticks:?}");
    }
}