use crate::opengl::shader::{
    Error as ShaderError,
    Kind as ShaderKind,
    Program as ShaderProgram,
    Shader,
};
use crate::renderer::Renderable;
use crate::vertex::Vertex;

#[derive(Debug)]
pub struct Object
{
    id: Id,
    renderable: Renderable,
}

impl Object
{
    /// Returns a new `Object`.
    ///
    /// # Errors
    /// Will return `Err` if shader creation fails or if shader program linking fails.
    pub fn new(id: Id, vertices: &[Vertex]) -> Result<Self, Error>
    {
        let vertex_shader = Shader::new(ShaderKind::Vertex);

        vertex_shader
            .set_source(include_str!("../vertex.glsl"))
            .map_err(Error::CreateVertexShaderFailed)?;

        vertex_shader
            .compile()
            .map_err(Error::CreateVertexShaderFailed)?;

        let fragment_shader = Shader::new(ShaderKind::Fragment);

        fragment_shader
            .set_source(include_str!("../fragment.glsl"))
            .map_err(Error::CreateFragmentShaderFailed)?;

        fragment_shader
            .compile()
            .map_err(Error::CreateFragmentShaderFailed)?;

        let shader_program = ShaderProgram::new();

        shader_program.attach(&vertex_shader);
        shader_program.attach(&fragment_shader);

        shader_program
            .link()
            .map_err(Error::LinkShaderProgramFailed)?;

        let renderable = Renderable::new(shader_program, vertices);

        Ok(Self { id, renderable })
    }

    /// Returns the object ID.
    #[must_use]
    pub fn id(&self) -> Id
    {
        self.id
    }

    pub(crate) fn renderable(&self) -> &Renderable
    {
        &self.renderable
    }
}

/// Object error
#[derive(Debug, thiserror::Error)]
pub enum Error
{
    #[error("Failed to create vertex shader")]
    CreateVertexShaderFailed(#[source] ShaderError),

    #[error("Failed to create fragment shader")]
    CreateFragmentShaderFailed(#[source] ShaderError),

    #[error("Failed to link shader program")]
    LinkShaderProgramFailed(#[source] ShaderError),
}

/// Object ID.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Id
{
    id: u16,
}

impl Id
{
    /// Returns a new object ID.
    #[must_use]
    pub fn new(id: u16) -> Self
    {
        Self { id }
    }
}