//! This models contains structs that help move the camera in a user-friendly way.

const EPSILON: f32 = 0.001;

use glium::glutin::{
    Event,
    WindowEvent,
    ElementState,
    MouseButton,
    MouseScrollDelta,
};

use math::vector::{Vector2, Vector3};
use renderer::camera::Camera;
use model::Model;

/// The trait that all controls should implement.
pub trait Controls {

    /// Modifies the camera depending on the event.
    fn manage_event(&mut self, event: &Event, camera: &mut Camera);
}

/// An orbit controls allowing to orbit around an object.
///
/// Only object centered are supported.
pub struct OrbitControls {
    /// The last position of the mouse.
    mouse_position: Vector2<f32>,

    /// Wether the left click of the mouse is pressed or not.
    pressed: bool,

    /// The theta angle of the position of the camera in spheric coordinates.
    theta: f32,

    /// The phi angle of the position of the camera in spheric coordinates.
    phi: f32,

    /// The distance between the camera and the origin.
    distance: f32,

    /// The sensitiviy of the rotation of the mouse.
    sensitivity: f32,

    /// The center of the object.
    center: Vector3<f32>,
}

impl OrbitControls {

    /// Creates a new orbit controls, and initializes the camera.
    pub fn new(center: Vector3<f32>, distance: f32, camera: &mut Camera) -> OrbitControls {
        let controls = OrbitControls {
            mouse_position: Vector2::new(0.0, 0.0),
            pressed: false,
            theta: 0.0,
            phi: 0.0,
            distance: distance,
            sensitivity: 200.0,
            center: center,
        };

        *camera.position.x_mut() = controls.distance * controls.theta.cos();
        *camera.position.y_mut() = 0.0;
        *camera.position.z_mut() = controls.distance * controls.phi.sin();
        camera.position += controls.center;
        camera.target = controls.center;

        controls
    }

    /// Creates orbit controls that are mode to rotate around a model.
    pub fn around(model: &Model, camera: &mut Camera) -> OrbitControls {
        // Compute bounding box
        let bounding_box = model.bounding_box();
        let center = (bounding_box.min() + bounding_box.max()) / 2.0;
        let distance = (bounding_box.max() - bounding_box.min()).norm();

        OrbitControls::new(
            Vector3::new(center.x() as f32, center.y() as f32, center.z() as f32),
            distance as f32,
            camera
        )

    }
}

impl Controls for OrbitControls {
    fn manage_event(&mut self, event: &Event, camera: &mut Camera) {
        match *event {

            Event::WindowEvent {
                event: WindowEvent::MouseInput {
                    button: MouseButton::Left,
                    state, ..
                }, ..
            } => {
                self.pressed = state == ElementState::Pressed;
            },

            Event::WindowEvent {
                event: WindowEvent::MouseWheel {
                    delta: MouseScrollDelta::LineDelta(_, y), ..
                }, ..
            } => {
                self.distance -= y;

                *camera.position.x_mut() = self.distance * self.phi.cos() * self.theta.cos();
                *camera.position.y_mut() = self.distance * self.phi.sin();
                *camera.position.z_mut() = self.distance * self.phi.cos() * self.theta.sin();

                camera.position += self.center;
                camera.target = self.center;
            },

            Event::WindowEvent{
                event: WindowEvent::CursorMoved {
                    position: (x, y), ..
                }, ..
            } => {
                let current_position = Vector2::new(x as f32, y as f32);

                if self.pressed {
                    let difference = (current_position - self.mouse_position) / self.sensitivity;

                    self.theta += difference.x();
                    self.phi   += difference.y();

                    use std::f32::consts::PI;
                    self.phi = self.phi.max(- PI/2.0 + EPSILON);
                    self.phi = self.phi.min(  PI/2.0 - EPSILON);

                    *camera.position.x_mut() = self.distance * self.phi.cos() * self.theta.cos();
                    *camera.position.y_mut() = self.distance * self.phi.sin();
                    *camera.position.z_mut() = self.distance * self.phi.cos() * self.theta.sin();

                    camera.position += self.center;
                    camera.target = self.center;

                }

                // Record new position
                self.mouse_position = current_position;
            },

            _ => (),
        }
    }
}