// Standard
use std::marker::PhantomData;

// Library
use gfx::{self, traits::Factory};
use image::{DynamicImage, GenericImageView};
use vek::Vec2;

// Local
use super::{gfx_backend, Pipeline, RenderError};

type ShaderFormat = (gfx::format::R8_G8_B8_A8, gfx::format::Srgb);

/// Represents an image that has been uploaded to the GPU.
pub struct Texture<P: Pipeline> {
    pub tex: gfx::handle::Texture<
        gfx_backend::Resources,
        <ShaderFormat as gfx::format::Formatted>::Surface,
    >,
    pub srv: gfx::handle::ShaderResourceView<
        gfx_backend::Resources,
        <ShaderFormat as gfx::format::Formatted>::View,
    >,
    pub sampler: gfx::handle::Sampler<gfx_backend::Resources>,
    _phantom: PhantomData<P>,
}

impl<P: Pipeline> Texture<P> {
    pub fn new(
        factory: &mut gfx_backend::Factory,
        image: &DynamicImage,
    ) -> Result<Self, RenderError> {
        let (tex, srv) = factory
            .create_texture_immutable_u8::<ShaderFormat>(
                gfx::texture::Kind::D2(
                    image.width() as u16,
                    image.height() as u16,
                    gfx::texture::AaMode::Single,
                ),
                gfx::texture::Mipmap::Provided,
                &[&image.to_rgba().into_raw()],
            )
            .map_err(|err| RenderError::CombinedError(err))?;

        Ok(Self {
            tex,
            srv,
            sampler: factory.create_sampler(gfx::texture::SamplerInfo::new(
                gfx::texture::FilterMethod::Scale,
                gfx::texture::WrapMode::Clamp,
            )),
            _phantom: PhantomData,
        })
    }
    pub fn new_dynamic(
        factory: &mut gfx_backend::Factory,
        width: u16,
        height: u16,
    ) -> Result<Self, RenderError> {
        let tex = factory.create_texture(
            gfx::texture::Kind::D2(
                width,
                height,
                gfx::texture::AaMode::Single,
            ),
            1 as gfx::texture::Level,
            gfx::memory::Bind::SHADER_RESOURCE,
            gfx::memory::Usage::Dynamic,
            Some(<<ShaderFormat as gfx::format::Formatted>::Channel as gfx::format::ChannelTyped>::get_channel_type()),
        )
            .map_err(|err| RenderError::CombinedError(gfx::CombinedError::Texture(err)))?;

        let srv = factory
            .view_texture_as_shader_resource::<ShaderFormat>(
                &tex,
                (0, 0),
                gfx::format::Swizzle::new(),
            )
            .map_err(|err| RenderError::CombinedError(gfx::CombinedError::Resource(err)))?;

        Ok(Self {
            tex,
            srv,
            sampler: factory.create_sampler(gfx::texture::SamplerInfo::new(
                gfx::texture::FilterMethod::Scale,
                gfx::texture::WrapMode::Clamp,
            )),
            _phantom: PhantomData,
        })
    }

    // Updates a texture with the given data (used for updating the glyph cache texture)
    pub fn update(
        &self,
        encoder: &mut gfx::Encoder<gfx_backend::Resources, gfx_backend::CommandBuffer>,
        offset: [u16; 2],
        size: [u16; 2],
        data: &[[u8; 4]],
    ) -> Result<(), RenderError> {
        let info = gfx::texture::ImageInfoCommon {
            xoffset: offset[0],
            yoffset: offset[1],
            zoffset: 0,
            width: size[0],
            height: size[1],
            depth: 0,
            format: (),
            mipmap: 0,
        };
        encoder
            .update_texture::<<ShaderFormat as gfx::format::Formatted>::Surface, ShaderFormat>(
                &self.tex, None, info, data,
            )
            .map_err(|err| RenderError::TexUpdateError(err))
    }
    /// Get dimensions of the represented image
    pub fn get_dimensions(&self) -> Vec2<u16> {
        let (w, h, ..) = self.tex.get_info().kind.get_dimensions();
        Vec2::new(w, h)
    }
}