1 files changed, 109 insertions, 1 deletions
diff --git a/src/ecs/components.zig b/src/ecs/components.zig
index ae379b4..bb333c9 100644
--- a/src/ecs/components.zig
+++ b/src/ecs/components.zig
@@ -1,3 +1,111 @@
 const std = @import("std");
+const Allocator = std.mem.Allocator;
 
-pub const Archetype = struct {};
+pub const Position = struct {
+    x: f32,
+    y: f32,
+    z: f32,
+};
+
+pub const Speed = struct {
+    speed: f32,
+};
+
+pub const Pool = struct {
+    comptime sets_map: std.StringHashMap([]const u8) = std.StringHashMap([]const u8).init(allocator),
+    speed_set: SparseSet(Speed),
+    allocator: Allocator,
+    free_ids: std.ArrayList(usize),
+    entities: usize,
+
+    pub fn init(allocator: Allocator) !Pool {
+        try sets_map.put(@typeName(Speed), "speed_set");
+
+        return Pool{
+            .speed_set = try SparseSet(Speed).init(allocator),
+            .allocator = allocator,
+            .free_ids = try std.ArrayList(usize).initCapacity(allocator, 100),
+            .entities = 0,
+        };
+    }
+
+    pub fn deinit(self: *Pool) void {
+        self.sets_map.deinit();
+        self.speed_set.deinit();
+    }
+
+    pub fn addComponent(self: *Pool, comptime T: type, id: usize, component: T) void {
+        var set = @field(self, try self.sets_map.get(@typeName(T)));
+
+        set.insert(id, component);
+    }
+
+    pub fn insert(self: *Pool) !usize {
+        const id = self.free_ids.pop() orelse self.entities;
+
+        self.entities += 1;
+        return id;
+    }
+
+    pub fn remove(self: *Pool, id: usize) !usize {
+        if (self.speed_set.hasComponent(id)) {
+            self.speed_set.remove(id);
+        }
+
+        self.entities -= 1;
+        self.free_ids.append(id);
+    }
+};
+
+pub fn SparseSet(comptime T: type) type {
+    return struct {
+        sparse: std.ArrayList(usize),
+        dense: std.ArrayList(usize),
+        components: std.ArrayList(T),
+
+        pub fn init(allocator: Allocator) !@This() {
+            return @This(){
+                .sparse = try std.ArrayList(usize).initCapacity(allocator, 10),
+                .dense = try std.ArrayList(usize).initCapacity(allocator, 10),
+                .components = try std.ArrayList(T).initCapacity(allocator, 10),
+            };
+        }
+
+        pub fn deinit(self: *@This()) void {
+            self.sparse.deinit();
+            self.dense.deinit();
+            self.components.deinit();
+        }
+
+        pub fn hasComponent(self: *@This(), id: usize) bool {
+            return self.dense.items[self.sparse.items[id]] == id;
+        }
+
+        pub fn insert(self: *@This(), id: usize, component: T) !void {
+            const dense_index = self.dense.items.len;
+            try self.dense.append(id);
+            try self.components.append(component);
+            try self.sparse.append(dense_index);
+        }
+
+        pub fn remove(self: *@This(), id: usize) !void {
+            const index = self.sparse.items[id];
+            const last = self.dense.getLast();
+            self.sparse.items[last] = index;
+            _ = self.dense.swapRemove(index);
+            _ = self.components.swapRemove(index);
+        }
+    };
+}
+
+pub fn test_sparse() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+
+    var pool = try Pool.init(allocator);
+    defer pool.deinit();
+
+    const entity = try pool.insert();
+    std.debug.print("new entity: {d}\n", .{entity});
+    pool.addComponent(Speed, entity, .{ .speed = 5.0 });
+}