#![no_std]

extern crate smallvec;
use smallvec::SmallVec;

pub struct SyncDevice {
    /// sync tracks (the vertical columns in the editor)
    pub tracks: SmallVec<[SyncTrack; 64]>,
    /// rows per beat
    pub rpb: u8,
    /// beats per minute
    pub bpm: f64,
    /// rows per second
    pub rps: f64,
    pub is_paused: bool,
    /// current row
    pub row: u32,
    /// current time in milliseconds
    pub time: u32,
}

impl SyncDevice {
    pub fn new(bpm: f64, rpb: u8) -> SyncDevice {
        SyncDevice {
            tracks: SmallVec::new(),
            rpb: rpb,
            bpm: bpm,
            rps: rps(bpm, rpb),
            is_paused: true,
            row: 0,
            time: 0,
        }
    }

    pub fn set_row_from_time(&mut self) {
        let r: f64 = (self.time as f64 / 1000.0) * self.rps + 0.5;
        self.row = r as u32;
    }

    pub fn get_track_value(&self, track_id: usize) -> Result<f64, SyncError> {
        if self.tracks.len() > track_id {
            return Ok(self.tracks[track_id].value_at(self.row));
        } else {
            return Err(SyncError::TrackDoesntExist);
        }
    }
}

pub struct SyncTrack {
    /// key frames, rows where values change
    pub keys: SmallVec<[TrackKey; 64]>,
}

pub enum SyncError {
    TrackDoesntExist
}

pub struct TrackKey {
    pub row: u32,
    pub value: f32,
    /// interpolation type
    pub key_type: KeyType,
}

pub enum KeyType {
    Step, // constant until value changes
    Linear, // linear interpolation
    Smooth, // smooth curve
    Ramp, // exponential ramp
    NOOP,
}

pub enum ActiveKeyIdx {
    /// key is on this row
    ExactRow(usize),
    /// key is on a previous row
    PrevRow(usize),
    /// the row is before the first key
    BeforeFirstRow,
    /// row moved past the last row
    AfterLastRow,
}

impl SyncTrack {
    pub fn new() -> SyncTrack {
        SyncTrack {
            keys: SmallVec::new(),
        }
    }

    /// Adds a key to the track, inserting sorted by row, replacing if one already exists on that row
    pub fn add_key(&mut self, track_key: TrackKey) {

        let res = self.find_active_key_idx_for_row(track_key.row);

        if let Some(idx) = res {
            // Some kind of active key
            use self::ActiveKeyIdx::*;
            match idx {
                // replace key
                ExactRow(n) => self.keys[n] = track_key,

                // add new key
                PrevRow(n) => self.keys.insert(n+1, track_key),
                BeforeFirstRow => self.keys.insert(0, track_key),
                AfterLastRow => self.keys.push(track_key),
            }
        } else {
            // No keys, first key
            self.keys.push(track_key);
        }
    }

    /// Deletes the key found on the given row
    pub fn delete_key(&mut self, row: u32) {
        if let Some(idx) = self.find_key_idx_by_row(row) {
            self.keys.remove(idx);
        }
    }

    /// Returns index of the key with the given row, or `None`
    pub fn find_key_idx_by_row(&self, row: u32) -> Option<usize> {
        for (idx, key) in self.keys.iter().enumerate() {
            if key.row == row {
                return Some(idx);
            }
        }

        None
    }

    pub fn value_at(&self, row: u32) -> f64 {

        let hit_idx: usize;

        if let Some(hit) = self.find_active_key_idx_for_row(row) {
            use self::ActiveKeyIdx::*;
            match hit {
                ExactRow(n) => return self.keys[n].value as f64,

                PrevRow(n) => hit_idx = n,

                // hit is beyond the last key
                AfterLastRow => return self.keys[self.keys.len() - 1].value as f64,

                BeforeFirstRow => return self.keys[0].value as f64,
            }
        } else {
            return 0.0;
        }

        // return interpolated value
        let cur_key = &self.keys[hit_idx];
        let next_key = &self.keys[hit_idx + 1];

	      let t: f64 = ((row - cur_key.row) as f64) / ((next_key.row - cur_key.row) as f64);
        let a: f64 = cur_key.value as f64;
        let b: f64 = (next_key.value - cur_key.value) as f64;

        use self::KeyType::*;
        match cur_key.key_type {
            Step => return a,

            Linear => return a + b * t,

            Smooth => return a + b * (t*t * (3.0 - 2.0 * t)),

            Ramp => return a + b * t*t,

            NOOP => return 0.0,
        }

    }

    /// Find the active key idx for a row
    pub fn find_active_key_idx_for_row(&self, row: u32) -> Option<ActiveKeyIdx> {
        if self.keys.len() == 0 {
            return None;
        }

        // Linear search. Keys are sorted by row.

        let mut hit_idx: usize = 0;
        let mut ret: Option<ActiveKeyIdx> = None;

        for (idx, key) in self.keys.iter().enumerate() {
            if key.row == row {
                return Some(ActiveKeyIdx::ExactRow(idx));
            } else if key.row < row {
                hit_idx = idx;
                ret = Some(ActiveKeyIdx::PrevRow(hit_idx));
            }
        }

        if hit_idx == self.keys.len() - 1 {
            return Some(ActiveKeyIdx::AfterLastRow);
        }

        if hit_idx == 0 && ret.is_none() {
            return Some(ActiveKeyIdx::BeforeFirstRow);
        }

        ret
    }
}

impl TrackKey {
    pub fn new() -> TrackKey {
        TrackKey {
            row: 0,
            value: 0.0,
            key_type: KeyType::Step,
        }
    }
}

/// Calculate rows per second
pub fn rps(bpm: f64, rpb: u8) -> f64 {
    (bpm / 60.0) * (rpb as f64)
}

pub fn key_to_code(key: &KeyType) -> u8 {
    use self::KeyType::*;
    match *key {
        Step      => 0,
        Linear    => 1,
        Smooth    => 2,
        Ramp      => 3,
        NOOP      => 255,
    }
}

pub fn code_to_key(code: u8) -> KeyType {
    use self::KeyType::*;
    match code {
        0 => Step,
        1 => Linear,
        2 => Smooth,
        3 => Ramp,
        _ => NOOP,
    }
}