//! 面向设备像素的绘制指令集合。它承载矩形、文字、裁剪与 3D 表面等原语，不直接操作 VM。
//! 平移和缩放统一作用于命令几何；文字样式和裁剪也要使用一致的设备比例。
//!
use crate::geometry::{Point, Rect};
use crate::text::TextStyle;

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
/// 设备绘制使用的 RGBA 字节通道，区别于源代码的颜色文本。
pub struct Color {
    pub red: u8,
    pub green: u8,
    pub blue: u8,
    pub alpha: u8,
}

impl Color {
    /// 从 RGB 通道构造不透明颜色值。
    pub const fn rgb(red: u8, green: u8, blue: u8) -> Self {
        Self {
            red,
            green,
            blue,
            alpha: 255,
        }
    }

    /// 从 RGBA 通道构造带透明度的颜色值。
    pub const fn rgba(red: u8, green: u8, blue: u8, alpha: u8) -> Self {
        Self {
            red,
            green,
            blue,
            alpha,
        }
    }
}

#[derive(Clone, Debug)]
/// 原生画布最终顺序执行的绘制原语，已经使用对应设备比例。
pub enum DrawCommand {
    Scene3D {
        rect: Rect,
        view: std::sync::Arc<crate::scene3d::View>,
    },
    Clear(Color),
    PushClip(Rect),
    PopClip,
    FillRoundedRect {
        rect: Rect,
        radius: f32,
        color: Color,
    },
    StrokeRoundedRect {
        rect: Rect,
        radius: f32,
        width: f32,
        color: Color,
    },
    WrappedText {
        rect: Rect,
        value: String,
        style: TextStyle,
        color: Color,
    },
    Text {
        origin: Point,
        value: String,
        style: TextStyle,
        color: Color,
    },
}

impl DrawCommand {
    /// 返回平移后的绘制命令，并同步移动命令中的相关几何。
    pub fn translated(mut self, delta: Point) -> Self {
        match &mut self {
            Self::WrappedText { rect, .. }
            | Self::Scene3D { rect, .. }
            | Self::PushClip(rect)
            | Self::FillRoundedRect { rect, .. }
            | Self::StrokeRoundedRect { rect, .. } => {
                rect.x += delta.x;
                rect.y += delta.y;
            }
            Self::Text { origin, .. } => {
                origin.x += delta.x;
                origin.y += delta.y;
            }
            _ => {}
        }
        self
    }
}

#[derive(Clone, Debug, Default)]
/// 有序绘制原语容器；命令顺序同时约束叠放和裁剪栈行为。
pub struct DisplayList {
    commands: Vec<DrawCommand>,
}

impl DisplayList {
    /// 按设备比例缩放命令，文字、边框和矩形不能分别使用不一致比例。
    pub fn scale(&mut self, scale: f32) {
        for command in &mut self.commands {
            let rect = match command {
                DrawCommand::WrappedText { rect, style, .. } => {
                    *style = style.scaled(scale);
                    Some(rect)
                }
                DrawCommand::PushClip(rect) => Some(rect),
                DrawCommand::Scene3D { rect, .. } => Some(rect),
                DrawCommand::FillRoundedRect { rect, radius, .. } => {
                    *radius *= scale;
                    Some(rect)
                }
                DrawCommand::StrokeRoundedRect {
                    rect,
                    radius,
                    width,
                    ..
                } => {
                    *radius *= scale;
                    *width *= scale;
                    Some(rect)
                }
                DrawCommand::Text { origin, style, .. } => {
                    origin.x *= scale;
                    origin.y *= scale;
                    *style = style.scaled(scale);
                    None
                }
                _ => None,
            };
            if let Some(rect) = rect {
                rect.x *= scale;
                rect.y *= scale;
                rect.width *= scale;
                rect.height *= scale;
            }
        }
    }
    /// 按绘制顺序追加一条原语，后加入的内容在合成顺序中位于后面。
    pub fn push(&mut self, command: DrawCommand) {
        self.commands.push(command);
    }

    /// 平移当前显示列表中的命令，供整块页面或管理面板放入窗口坐标。
    pub fn translate(&mut self, delta: Point) {
        for command in &mut self.commands {
            match command {
                DrawCommand::WrappedText { rect, .. }
                | DrawCommand::Scene3D { rect, .. }
                | DrawCommand::PushClip(rect)
                | DrawCommand::FillRoundedRect { rect, .. }
                | DrawCommand::StrokeRoundedRect { rect, .. } => {
                    rect.x += delta.x;
                    rect.y += delta.y;
                }
                DrawCommand::Text { origin, .. } => {
                    origin.x += delta.x;
                    origin.y += delta.y;
                }
                DrawCommand::Clear(_) | DrawCommand::PopClip => {}
            }
        }
    }

    /// 借用按绘制顺序排列的原生原语，不复制命令集合。
    pub fn commands(&self) -> &[DrawCommand] {
        &self.commands
    }

    /// 按原顺序合并另一组绘制命令，不在这里重排层次。
    pub fn extend(&mut self, other: DisplayList) {
        self.commands.extend(other.commands);
    }
}