feat(display-server): add DisplayServer<F: Framebuffer> with protocol, mock adapter, and tests

crates/servers/display-server/Cargo.toml

@@ -4,3 +4,5 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+types = { workspace = true }
+server-framework = { workspace = true }

crates/servers/display-server/src/adapters/mock.rs

@@ -0,0 +1,66 @@
+use crate::framebuffer::Framebuffer;
+
+pub struct MockFramebuffer {
+    width: u16,
+    height: u16,
+    pixels: [(u16, u16, u32); 4096],
+    pixel_count: usize,
+    flushed: bool,
+}
+
+impl MockFramebuffer {
+    pub fn new(width: u16, height: u16) -> Self {
+        Self {
+            width,
+            height,
+            pixels: [(0, 0, 0); 4096],
+            pixel_count: 0,
+            flushed: false,
+        }
+    }
+
+    pub fn pixel_count(&self) -> usize {
+        self.pixel_count
+    }
+
+    pub fn was_flushed(&self) -> bool {
+        self.flushed
+    }
+
+    pub fn pixel_at(&self, index: usize) -> (u16, u16, u32) {
+        self.pixels[index]
+    }
+}
+
+impl Framebuffer for MockFramebuffer {
+    fn width(&self) -> u16 {
+        self.width
+    }
+
+    fn height(&self) -> u16 {
+        self.height
+    }
+
+    fn write_pixel(&mut self, x: u16, y: u16, color: u32) {
+        if self.pixel_count < self.pixels.len() {
+            self.pixels[self.pixel_count] = (x, y, color);
+            self.pixel_count += 1;
+        }
+    }
+
+    fn fill_rect(&mut self, x: u16, y: u16, w: u16, h: u16, color: u32) {
+        for dy in 0..h {
+            for dx in 0..w {
+                self.write_pixel(x + dx, y + dy, color);
+            }
+        }
+    }
+
+    fn clear(&mut self, _color: u32) {
+        self.pixel_count = 0;
+    }
+
+    fn flush(&mut self) {
+        self.flushed = true;
+    }
+}

crates/servers/display-server/src/adapters/mod.rs

@@ -0,0 +1 @@
+pub mod mock;

crates/servers/display-server/src/framebuffer.rs

@@ -0,0 +1,8 @@
+pub trait Framebuffer {
+    fn width(&self) -> u16;
+    fn height(&self) -> u16;
+    fn write_pixel(&mut self, x: u16, y: u16, color: u32);
+    fn fill_rect(&mut self, x: u16, y: u16, w: u16, h: u16, color: u32);
+    fn clear(&mut self, color: u32);
+    fn flush(&mut self);
+}

crates/servers/display-server/src/lib.rs

@@ -1,14 +1,10 @@
-pub fn add(left: u64, right: u64) -> u64 {
-    left + right
-}
+#![no_std]
+
+pub mod adapters;
+pub mod framebuffer;
+pub mod protocol;
+pub mod server;
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
-    }
-}
+#[path = "tests/mod.rs"]
+mod tests;

crates/servers/display-server/src/protocol.rs

@@ -0,0 +1,76 @@
+use server_framework::{Decode, Encode};
+
+#[derive(Debug, PartialEq)]
+pub enum DisplayRequest {
+    DrawRect { x: u16, y: u16, w: u16, h: u16, color: u32 },
+    Clear { color: u32 },
+    Flush,
+    GetDimensions,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum DisplayResponse {
+    Ok,
+    Dimensions { width: u16, height: u16 },
+    Error,
+}
+
+impl Encode for DisplayRequest {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            DisplayRequest::DrawRect { x, y, w, h, color } => {
+                let xy = (*x as usize) | ((*y as usize) << 16);
+                let wh = (*w as usize) | ((*h as usize) << 16);
+                [0, xy, wh, *color as usize]
+            }
+            DisplayRequest::Clear { color } => [1, *color as usize, 0, 0],
+            DisplayRequest::Flush => [2, 0, 0, 0],
+            DisplayRequest::GetDimensions => [3, 0, 0, 0],
+        }
+    }
+}
+
+impl Decode for DisplayRequest {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => {
+                let x = (words[1] & 0xFFFF) as u16;
+                let y = ((words[1] >> 16) & 0xFFFF) as u16;
+                let w = (words[2] & 0xFFFF) as u16;
+                let h = ((words[2] >> 16) & 0xFFFF) as u16;
+                let color = words[3] as u32;
+                Some(DisplayRequest::DrawRect { x, y, w, h, color })
+            }
+            1 => Some(DisplayRequest::Clear { color: words[1] as u32 }),
+            2 => Some(DisplayRequest::Flush),
+            3 => Some(DisplayRequest::GetDimensions),
+            _ => None,
+        }
+    }
+}
+
+impl Encode for DisplayResponse {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            DisplayResponse::Ok => [0, 0, 0, 0],
+            DisplayResponse::Dimensions { width, height } => {
+                [1, *width as usize, *height as usize, 0]
+            }
+            DisplayResponse::Error => [2, 0, 0, 0],
+        }
+    }
+}
+
+impl Decode for DisplayResponse {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => Some(DisplayResponse::Ok),
+            1 => Some(DisplayResponse::Dimensions {
+                width: words[1] as u16,
+                height: words[2] as u16,
+            }),
+            2 => Some(DisplayResponse::Error),
+            _ => None,
+        }
+    }
+}

crates/servers/display-server/src/server.rs

@@ -0,0 +1,44 @@
+use server_framework::Server;
+
+use crate::framebuffer::Framebuffer;
+use crate::protocol::{DisplayRequest, DisplayResponse};
+
+pub struct DisplayServer<F: Framebuffer> {
+    fb: F,
+}
+
+impl<F: Framebuffer> DisplayServer<F> {
+    pub fn new(fb: F) -> Self {
+        Self { fb }
+    }
+
+    pub fn framebuffer(&self) -> &F {
+        &self.fb
+    }
+}
+
+impl<F: Framebuffer> Server for DisplayServer<F> {
+    type Request = DisplayRequest;
+    type Response = DisplayResponse;
+
+    fn handle(&mut self, request: DisplayRequest) -> DisplayResponse {
+        match request {
+            DisplayRequest::DrawRect { x, y, w, h, color } => {
+                self.fb.fill_rect(x, y, w, h, color);
+                DisplayResponse::Ok
+            }
+            DisplayRequest::Clear { color } => {
+                self.fb.clear(color);
+                DisplayResponse::Ok
+            }
+            DisplayRequest::Flush => {
+                self.fb.flush();
+                DisplayResponse::Ok
+            }
+            DisplayRequest::GetDimensions => DisplayResponse::Dimensions {
+                width: self.fb.width(),
+                height: self.fb.height(),
+            },
+        }
+    }
+}

crates/servers/display-server/src/tests/mod.rs

@@ -0,0 +1,2 @@
+mod protocol;
+mod server;

crates/servers/display-server/src/tests/protocol.rs

@@ -0,0 +1,54 @@
+use crate::protocol::{DisplayRequest, DisplayResponse};
+use server_framework::{Decode, Encode};
+
+#[test]
+fn draw_rect_roundtrip() {
+    let req = DisplayRequest::DrawRect {
+        x: 10,
+        y: 20,
+        w: 100,
+        h: 50,
+        color: 0xFF0000,
+    };
+    let words = req.encode();
+    let decoded = DisplayRequest::decode(words).unwrap();
+    assert_eq!(decoded, req);
+}
+
+#[test]
+fn clear_roundtrip() {
+    let req = DisplayRequest::Clear { color: 0x00FF00 };
+    let words = req.encode();
+    let decoded = DisplayRequest::decode(words).unwrap();
+    assert_eq!(decoded, req);
+}
+
+#[test]
+fn flush_roundtrip() {
+    let words = DisplayRequest::Flush.encode();
+    let decoded = DisplayRequest::decode(words).unwrap();
+    assert_eq!(decoded, DisplayRequest::Flush);
+}
+
+#[test]
+fn get_dimensions_roundtrip() {
+    let words = DisplayRequest::GetDimensions.encode();
+    let decoded = DisplayRequest::decode(words).unwrap();
+    assert_eq!(decoded, DisplayRequest::GetDimensions);
+}
+
+#[test]
+fn dimensions_response_roundtrip() {
+    let resp = DisplayResponse::Dimensions {
+        width: 320,
+        height: 240,
+    };
+    let words = resp.encode();
+    let decoded = DisplayResponse::decode(words).unwrap();
+    assert_eq!(decoded, resp);
+}
+
+#[test]
+fn invalid_request_returns_none() {
+    assert!(DisplayRequest::decode([99, 0, 0, 0]).is_none());
+}

crates/servers/display-server/src/tests/server.rs

@@ -0,0 +1,75 @@
+use crate::adapters::mock::MockFramebuffer;
+use crate::protocol::{DisplayRequest, DisplayResponse};
+use crate::server::DisplayServer;
+use server_framework::Server;
+
+fn test_server() -> DisplayServer<MockFramebuffer> {
+    DisplayServer::new(MockFramebuffer::new(320, 240))
+}
+
+#[test]
+fn draw_rect_writes_pixels() {
+    let mut server = test_server();
+    let resp = server.handle(DisplayRequest::DrawRect {
+        x: 0,
+        y: 0,
+        w: 4,
+        h: 3,
+        color: 0xFF,
+    });
+    assert_eq!(resp, DisplayResponse::Ok);
+    assert_eq!(server.framebuffer().pixel_count(), 12);
+}
+
+#[test]
+fn clear_resets_pixels() {
+    let mut server = test_server();
+    server.handle(DisplayRequest::DrawRect {
+        x: 0,
+        y: 0,
+        w: 10,
+        h: 10,
+        color: 0xFF,
+    });
+    server.handle(DisplayRequest::Clear { color: 0 });
+    assert_eq!(server.framebuffer().pixel_count(), 0);
+}
+
+#[test]
+fn flush_sets_flag() {
+    let mut server = test_server();
+    assert!(!server.framebuffer().was_flushed());
+    server.handle(DisplayRequest::Flush);
+    assert!(server.framebuffer().was_flushed());
+}
+
+#[test]
+fn get_dimensions_returns_size() {
+    let mut server = test_server();
+    let resp = server.handle(DisplayRequest::GetDimensions);
+    assert_eq!(
+        resp,
+        DisplayResponse::Dimensions {
+            width: 320,
+            height: 240
+        }
+    );
+}
+
+#[test]
+fn draw_rect_correct_pixel_positions() {
+    let mut server = test_server();
+    server.handle(DisplayRequest::DrawRect {
+        x: 5,
+        y: 10,
+        w: 2,
+        h: 2,
+        color: 0xAB,
+    });
+    let fb = server.framebuffer();
+    assert_eq!(fb.pixel_count(), 4);
+    assert_eq!(fb.pixel_at(0), (5, 10, 0xAB));
+    assert_eq!(fb.pixel_at(1), (6, 10, 0xAB));
+    assert_eq!(fb.pixel_at(2), (5, 11, 0xAB));
+    assert_eq!(fb.pixel_at(3), (6, 11, 0xAB));
+}