From 6ec27861b4df113b5392d03738612a3a1e2998bf Mon Sep 17 00:00:00 2001
From: Stephen Gutekanst <stephen@hexops.com>
Date: Mon, 4 Jul 2022 22:17:58 -0700
Subject: [PATCH] mach: initial support for high-level ECS applications

Adds experimental support for high-level ECS-based applications
following hexops/mach#349

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
---
 src/engine.zig | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.zig   |  6 ++++++
 2 files changed, 56 insertions(+)
 create mode 100644 src/engine.zig

diff --git a/src/engine.zig b/src/engine.zig
new file mode 100644
index 00000000..b146b7f7
--- /dev/null
+++ b/src/engine.zig
@@ -0,0 +1,50 @@
+pub const Core = @import("Core.zig");
+pub const gpu = @import("gpu");
+pub const ecs = @import("ecs");
+
+/// The Mach engine ECS module. This enables access to `engine.get(.mach, .core)` `*Core` APIs, as
+/// to for example `.setOptions(.{.title = "foobar"})`, or to access the GPU device via
+/// `engine.get(.mach, .device)`
+pub const module = ecs.Module(.{
+    .globals = struct {
+        core: *Core,
+        device: gpu.Device,
+    },
+});
+
+pub fn App(
+    modules: anytype,
+    init: anytype, // fn (engine: *ecs.World(modules)) !void
+) type {
+    // TODO: validate modules.mach is the expected type.
+    // TODO: validate init has the right function signature
+
+    return struct {
+        engine: ecs.World(modules),
+
+        pub fn init(app: *@This(), core: *Core) !void {
+            app.* = .{
+                .engine = try ecs.World(modules).init(core.allocator),
+            };
+            app.*.engine.set(.mach, .core, core);
+            app.*.engine.set(.mach, .device, core.device);
+            try init(&app.engine);
+        }
+
+        pub fn deinit(app: *@This(), _: *Core) void {
+            app.engine.deinit();
+        }
+
+        pub fn update(app: *@This(), _: *Core) !void {
+            app.engine.tick();
+        }
+
+        pub fn resize(app: *@This(), core: *Core, width: u32, height: u32) !void {
+            _ = app;
+            _ = core;
+            _ = width;
+            _ = height;
+            // TODO: send resize messages to ECS modules
+        }
+    };
+}
diff --git a/src/main.zig b/src/main.zig
index 9cd5e332..12880dab 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -3,3 +3,9 @@ pub usingnamespace @import("enums.zig");
 pub const Core = @import("Core.zig");
 pub const Timer = @import("Timer.zig");
 pub const ResourceManager = @import("resource/ResourceManager.zig");
+pub const gpu = @import("gpu");
+pub const ecs = @import("ecs");
+
+// Engine exports
+pub const App = @import("engine.zig").App;
+pub const module = @import("engine.zig").module;