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use {Event, Input, Motion};

/// Stores the touch state.
#[derive(Copy, Clone, Deserialize, Serialize, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
pub enum Touch {
    /// The start of touch, for example
    /// a finger pressed down on a touch screen.
    Start,
    /// The move of touch, for example
    /// a finger moving while touching a touch screen.
    Move,
    /// The end of touch, for example
    /// taking a finger away from a touch screen.
    End,
    /// The cancel of touch, for example
    /// the window loses focus.
    Cancel,
}

/// Touch arguments
///
/// The `id` might be reused for different touches that do not overlap in time.
///
/// - Coordinates are normalized to support both touch screens and trackpads
/// - Supports both 2D and 3D touch
/// - The pressure direction vector should have maximum length 1
///
/// For 2D touch the pressure is pointed in the z direction.
/// Use `.pressure()` to get the pressure magnitude.
#[derive(Copy, Clone, Deserialize, Serialize, PartialEq, PartialOrd, Debug)]
pub struct TouchArgs {
    /// A unique identifier for touch device.
    pub device: i64,
    /// A unique identifier for touch event.
    pub id: i64,
    /// The touch position, normalized 0..1.
    pub position_3d: [f64; 3],
    /// The touch pressure vector, normalized 0..1.
    pub pressure_3d: [f64; 3],
    /// Whether the touch is in 3D.
    pub is_3d: bool,
    /// The touch state.
    pub touch: Touch,
}

impl TouchArgs {
    /// Creates arguments for 2D touch.
    pub fn new(device: i64, id: i64, position: [f64; 2], pressure: f64, touch: Touch) -> TouchArgs {
        TouchArgs {
            device: device,
            id: id,
            position_3d: [position[0], position[1], 0.0],
            pressure_3d: [0.0, 0.0, pressure],
            is_3d: false,
            touch: touch,
        }
    }

    /// Creates arguments for 3D touch.
    ///
    /// The pressure direction vector should have maximum length 1.
    pub fn new_3d(device: i64,
                  id: i64,
                  position_3d: [f64; 3],
                  pressure_3d: [f64; 3],
                  touch: Touch)
                  -> TouchArgs {
        TouchArgs {
            device: device,
            id: id,
            position_3d,
            pressure_3d,
            is_3d: true,
            touch: touch,
        }
    }

    /// The position of the touch in 2D.
    pub fn position(&self) -> [f64; 2] {
        [self.position_3d[0], self.position_3d[1]]
    }

    /// The position of the touch in 3D.
    pub fn position_3d(&self) -> [f64; 3] {self.position_3d}

    /// The pressure magnitude, normalized 0..1.
    pub fn pressure(&self) -> f64 {
        let px = self.pressure_3d[0];
        let py = self.pressure_3d[1];
        let pz = self.pressure_3d[2];
        (px * px + py * py + pz * pz).sqrt()
    }

    /// The pressure vector in 3D.
    pub fn pressure_3d(&self) -> [f64; 3] {self.pressure_3d}
}

/// When a touch is started, moved, ended or cancelled.
pub trait TouchEvent: Sized {
    /// Creates a touch event.
    ///
    /// Preserves time stamp from original input event, if any.
    fn from_touch_args(args: &TouchArgs, old_event: &Self) -> Option<Self>;
    /// Calls closure if this is a touch event.
    fn touch<U, F>(&self, f: F) -> Option<U> where F: FnMut(&TouchArgs) -> U;
    /// Returns touch arguments.
    fn touch_args(&self) -> Option<TouchArgs> {
        self.touch(|args| args.clone())
    }
}

impl TouchEvent for Event {
    fn from_touch_args(args: &TouchArgs, old_event: &Self) -> Option<Self> {
        let timestamp = if let Event::Input(_, x) = old_event {*x} else {None};
        Some(Event::Input(Input::Move(Motion::Touch(*args)), timestamp))
    }

    fn touch<U, F>(&self, mut f: F) -> Option<U>
        where F: FnMut(&TouchArgs) -> U
    {
        match *self {
            Event::Input(Input::Move(Motion::Touch(ref args)), _) => Some(f(args)),
            _ => None,
        }
    }
}

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

    #[test]
    fn test_input_touch() {
        let pos = [0.0; 2];
        let e: Event = TouchArgs::new(0, 0, pos, 1.0, Touch::Start).into();
        let a: Option<Event> =
            TouchEvent::from_touch_args(&TouchArgs::new(0, 0, pos, 1.0, Touch::Start), &e);
        let b: Option<Event> = a.clone()
            .unwrap()
            .touch(|t| {
                TouchEvent::from_touch_args(&TouchArgs::new(t.device,
                                                            t.id,
                                                            t.position(),
                                                            t.pressure(),
                                                            Touch::Start),
                                            a.as_ref().unwrap())
            })
            .unwrap();
        assert_eq!(a, b);
    }

    #[test]
    fn test_input_touch_3d() {
        use super::super::Event;

        let pos = [0.0; 3];
        let pressure = [0.0, 0.0, 1.0];
        let e: Event = TouchArgs::new_3d(0, 0, pos, pressure, Touch::Start).into();
        let a: Option<Event> =
            TouchEvent::from_touch_args(&TouchArgs::new_3d(0, 0, pos, pressure, Touch::Start), &e);
        let b: Option<Event> = a.clone()
            .unwrap()
            .touch(|t| {
                TouchEvent::from_touch_args(&TouchArgs::new_3d(t.device,
                                                               t.id,
                                                               t.position_3d(),
                                                               t.pressure_3d(),
                                                               Touch::Start),
                                            a.as_ref().unwrap())
            })
            .unwrap();
        assert_eq!(a, b);
    }
}