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// Copyright 2017-2019 Matthew D. Michelotti
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Contains structs relating to application rendering.
//!
//! Rendering uses OpenGL shaders designed specifically for 2D pixel art,
//! looking crisp at any scale or rotation.

use std::marker::PhantomData;

use crate::asset_id::{AppAssetId, IdU16};

use super::geom::Affine;
use super::render_buffer::RenderBuffer;
use super::core_renderer::CoreRenderer;

/// Contains methods for rendering visuals to screen.
///
/// The renderer origin is the bottom-left of the screen, with +X meaning "right" and +Y meaning "up".
/// The dimensions of the screen in renderer units ("app pixels") are `AppContext.dims()`.
/// The default scaling of each image is such that one source image pixel equals one "app pixel".
///
/// This struct has functions for entering different rendering "modes".
/// Switching between different modes (or the same mode with different parameters)
/// can be expensive, since it involves flushing graphics data and switching shaders,
/// so try to minimize these switches.
///
/// Note: due to recent refactorings, there is currently only one render mode, the "sprite mode".
/// This will likely change in the near future.
pub struct Renderer<A: AppAssetId> { b: RenderBuffer, c: CoreRenderer, phantom: PhantomData<A> }

impl<A: AppAssetId> Renderer<A> {
    pub(crate) fn new(buffer: RenderBuffer, core_renderer: CoreRenderer) -> Renderer<A> {
        let mut result = Renderer { b: buffer, c: core_renderer, phantom: PhantomData };
        result.set_scissor();
        result
    }

    /// Clears the screen with the given `color` in rgb (red-green-blue) format.
    pub fn clear(&mut self, color: (u8, u8, u8)) {
        self.b.flush(&mut self.c);
        self.c.clear(color);
    }

    /// Enters "sprite mode", for rendering sprites.
    pub fn sprite_mode(&mut self) -> SpriteRenderer<A> {
        SpriteRenderer { r: self }
    }

    pub(crate) fn app_dims(&self) -> (f64, f64) { self.b.dims.dims }

    pub(crate) fn native_px(&self) -> f64 { 1. / self.b.dims.pixel_scalar }

    pub(crate) fn to_app_pos(&self, raw_x: i32, raw_y: i32) -> (f64, f64) {
        self.b.dims.to_app_pos(raw_x, raw_y)
    }

    pub(crate) fn flush(&mut self) {
        self.b.flush(&mut self.c);
    }

    pub(crate) fn set_screen_dims(&mut self, dims: (u32, u32)) {
        if dims != self.b.dims.native_dims {
            self.b.dims.set_native_dims(dims);
            self.set_scissor();
        }
    }

    fn set_scissor(&mut self) {
        let dims = &self.b.dims;
        self.c.set_scissor(
            dims.native_pre_pad.0,
            dims.native_pre_pad.1,
            dims.used_native_dims.0,
            dims.used_native_dims.1,
        );
    }
}

/// A rendering mode for sprites.
pub struct SpriteRenderer<'a, A: AppAssetId + 'a> {
    r: &'a mut Renderer<A>,
}

impl<'a, A: AppAssetId + 'a> SpriteRenderer<'a, A> {
    /// Draws the given `sprite` using the given `affine` transformation from the origin.
    pub fn draw(&mut self, affine: &Affine, sprite: A::Sprite) {
        self.draw_flash(affine, sprite, 0.);
    }

    /// Draws the given `sprite` blended with the color white using the given `affine` transformation from the origin.
    ///
    /// `flash_ratio`, capped between `0.0` and `1.0`, controls how much blending occurs with the
    /// color white (`0.0` means use the image unaltered, `1.0` means use white completely).
    pub fn draw_flash(&mut self, affine: &Affine, sprite: A::Sprite, flash_ratio: f64) {
        self.r.b.append_sprite(&mut self.r.c, affine, sprite.id_u16(), flash_ratio);
    }
}