// file: crates/engines/engine-v1-common/src/render.rs
// version: 1

/// Maximum rectangle count carried by one engine V1 scene snapshot.
pub const ENGINE_SCENE_RECT_CAPACITY: usize = 64;

/// Platform-independent RGBA color.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct RenderColor {
    red: u8,
    green: u8,
    blue: u8,
    alpha: u8,
}

impl RenderColor {
    /// Creates an opaque RGB color.
    #[must_use]
    pub const fn rgb(red: u8, green: u8, blue: u8) -> Self {
        return Self { red, green, blue, alpha: 255 };
    }

    /// Returns the red channel.
    #[must_use]
    pub const fn red(self) -> u8 {
        return self.red;
    }

    /// Returns the green channel.
    #[must_use]
    pub const fn green(self) -> u8 {
        return self.green;
    }

    /// Returns the blue channel.
    #[must_use]
    pub const fn blue(self) -> u8 {
        return self.blue;
    }

    /// Returns the alpha channel.
    #[must_use]
    pub const fn alpha(self) -> u8 {
        return self.alpha;
    }
}

/// Rectangle expressed in normalized viewport coordinates.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct NormalizedRect {
    x: f32,
    y: f32,
    width: f32,
    height: f32,
}

impl NormalizedRect {
    /// Creates a normalized rectangle while clamping all coordinates and dimensions.
    #[must_use]
    pub fn new(x: f32, y: f32, width: f32, height: f32) -> Self {
        let x = x.clamp(0.0, 1.0);
        let y = y.clamp(0.0, 1.0);
        let width = width.clamp(0.0, 1.0 - x);
        let height = height.clamp(0.0, 1.0 - y);
        return Self { x, y, width, height };
    }

    /// Returns the normalized left coordinate.
    #[must_use]
    pub const fn x(self) -> f32 {
        return self.x;
    }

    /// Returns the normalized top coordinate.
    #[must_use]
    pub const fn y(self) -> f32 {
        return self.y;
    }

    /// Returns the normalized width.
    #[must_use]
    pub const fn width(self) -> f32 {
        return self.width;
    }

    /// Returns the normalized height.
    #[must_use]
    pub const fn height(self) -> f32 {
        return self.height;
    }

    /// Reports whether a normalized pointer coordinate lies inside this rectangle.
    #[must_use]
    pub fn contains(self, x: f32, y: f32) -> bool {
        return x >= self.x && y >= self.y && x <= self.x + self.width && y <= self.y + self.height;
    }
}

/// One colored rectangle in a platform-independent scene.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct RenderRect {
    rect: crate::NormalizedRect,
    color: crate::RenderColor,
}

impl RenderRect {
    /// Creates one colored scene rectangle.
    #[must_use]
    pub const fn new(rect: crate::NormalizedRect, color: crate::RenderColor) -> Self {
        return Self { rect, color };
    }

    /// Returns the rectangle geometry.
    #[must_use]
    pub const fn rect(self) -> crate::NormalizedRect {
        return self.rect;
    }

    /// Returns the rectangle color.
    #[must_use]
    pub const fn color(self) -> crate::RenderColor {
        return self.color;
    }
}

/// Immutable platform-independent scene snapshot.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct EngineScene {
    background: crate::RenderColor,
    rectangles: [Option<crate::RenderRect>; crate::ENGINE_SCENE_RECT_CAPACITY],
}

impl EngineScene {
    /// Creates an empty scene with the supplied background.
    #[must_use]
    pub const fn empty(background: crate::RenderColor) -> Self {
        return Self { background, rectangles: [None; crate::ENGINE_SCENE_RECT_CAPACITY] };
    }

    /// Returns the background color.
    #[must_use]
    pub const fn background(self) -> crate::RenderColor {
        return self.background;
    }

    /// Returns the rectangle slots.
    #[must_use]
    pub const fn rectangles(&self) -> &[Option<crate::RenderRect>; crate::ENGINE_SCENE_RECT_CAPACITY] {
        return &self.rectangles;
    }

    /// Returns a copy with one rectangle inserted into the first free slot.
    #[must_use]
    pub fn with_rect(mut self, rectangle: crate::RenderRect) -> Self {
        for slot in &mut self.rectangles {
            if slot.is_none() {
                *slot = Some(rectangle);
                return self;
            }
        }
        return self;
    }
}

#[cfg(test)]
#[path = "../unit_tests/render.rs"]
mod tests;