use crate::{err, Meter, Note, Result, Scale, MAX_LENGTH, MAX_PLAYBACK_NOTES};
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
pub enum ChordQuality {
    Major,
    Minor,
    Major7,
    Minor7,
    Sus2,
    Sus4,
}
impl ChordQuality {
    pub const ALL: [Self; 6] = [
        Self::Major,
        Self::Minor,
        Self::Major7,
        Self::Minor7,
        Self::Sus2,
        Self::Sus4,
    ];
    pub fn name(self) -> &'static str {
        match self {
            Self::Major => "Major",
            Self::Minor => "Minor",
            Self::Major7 => "Major 7",
            Self::Minor7 => "Minor 7",
            Self::Sus2 => "Sus 2",
            Self::Sus4 => "Sus 4",
        }
    }
    pub fn mask(self, root: u8) -> u16 {
        let intervals: &[u8] = match self {
            Self::Major => &[0, 4, 7],
            Self::Minor => &[0, 3, 7],
            Self::Major7 => &[0, 4, 7, 11],
            Self::Minor7 => &[0, 3, 7, 10],
            Self::Sus2 => &[0, 2, 7],
            Self::Sus4 => &[0, 5, 7],
        };
        intervals
            .iter()
            .fold(0, |mask, i| mask | 1 << ((root + i) % 12))
    }
}
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct HarmonySpan {
    pub start: u32,
    pub duration: u32,
    pub tones: u16,
    pub bass: u8,
}
#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq, Eq)]
pub struct Harmony {
    pub length: u32,
    pub spans: Vec<HarmonySpan>,
}
impl Harmony {
    pub fn validate(&self) -> Result<()> {
        if self.spans.is_empty() {
            return if self.length == 0 {
                Ok(())
            } else {
                Err(err("Empty harmony must have zero length."))
            };
        }
        if self.length == 0 || self.length > MAX_LENGTH || self.spans.len() > 256 {
            return Err(err("Harmony must fit 32 bars and at most 256 changes."));
        }
        let mut end = 0;
        for span in &self.spans {
            if span.duration == 0
                || span.start < end
                || span.start.saturating_add(span.duration) > self.length
                || span.tones == 0
                || span.tones > 0xfff
                || span.bass > 127
            {
                return Err(err("Invalid or overlapping harmonic regions."));
            }
            end = span.start + span.duration;
        }
        Ok(())
    }
    pub fn at(&self, tick: u32) -> Option<&HarmonySpan> {
        if self.length == 0 {
            return None;
        }
        let tick = tick % self.length;
        self.spans
            .iter()
            .find(|s| tick >= s.start && tick < s.start + s.duration)
    }
    pub fn from_midi(notes: &[Note], length: u32) -> Result<Self> {
        if notes.is_empty()
            || notes.len() > MAX_PLAYBACK_NOTES
            || length == 0
            || length > MAX_LENGTH
        {
            return Err(err("Import a harmony track of up to 32 bars."));
        }
        let mut edges = std::collections::BTreeSet::new();
        for n in notes {
            if n.pitch > 127 || n.duration == 0 || n.end() > length {
                return Err(err("Invalid harmony note."));
            }
            edges.insert(n.start);
            edges.insert(n.end());
        }
        let edges: Vec<_> = edges.into_iter().collect();
        let mut spans: Vec<HarmonySpan> = Vec::new();
        for pair in edges.windows(2) {
            let active: Vec<_> = notes
                .iter()
                .filter(|n| n.start <= pair[0] && n.end() > pair[0])
                .collect();
            if active.is_empty() {
                continue;
            }
            let tones = active.iter().fold(0, |mask, n| mask | 1 << (n.pitch % 12));
            let bass = active.iter().map(|n| n.pitch).min().unwrap();
            if let Some(last) = spans.last_mut() {
                if last.start + last.duration == pair[0] && last.tones == tones && last.bass == bass
                {
                    last.duration += pair[1] - pair[0];
                    continue;
                }
            }
            spans.push(HarmonySpan {
                start: pair[0],
                duration: pair[1] - pair[0],
                tones,
                bass,
            });
        }
        let context = Self { length, spans };
        context.validate()?;
        Ok(context)
    }
    pub fn progression(root: u8, scale: Scale, meter: Meter) -> Self {
        let minor = scale.minor();
        let bar = meter.bar();
        let chords = if minor {
            [
                (0, ChordQuality::Minor),
                (8, ChordQuality::Major),
                (3, ChordQuality::Major),
                (10, ChordQuality::Major),
            ]
        } else {
            [
                (0, ChordQuality::Major),
                (9, ChordQuality::Minor),
                (5, ChordQuality::Major),
                (7, ChordQuality::Major),
            ]
        };
        Self {
            length: 4 * bar,
            spans: chords
                .into_iter()
                .enumerate()
                .map(|(i, (step, quality))| {
                    let root = (root + step) % 12;
                    HarmonySpan {
                        start: i as u32 * bar,
                        duration: bar,
                        tones: quality.mask(root),
                        bass: 48 + root,
                    }
                })
                .collect(),
        }
    }
}