ecs: begin reworking queries

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

libs/ecs/src/entities.zig

@@ -4,6 +4,7 @@ const Allocator = mem.Allocator;
 const testing = std.testing;
 const builtin = @import("builtin");
 const assert = std.debug.assert;
+const query = @import("query.zig");
 
 const is_debug = builtin.mode == .Debug;
 
@@ -332,87 +333,8 @@ pub fn Entities(comptime all_components: anytype) type {
             row_index: u32,
         };
 
-        pub const Query = Query: {
-            const namespaces = std.meta.fields(@TypeOf(all_components));
-            var fields: [namespaces.len]std.builtin.Type.UnionField = undefined;
-            inline for (namespaces, 0..) |namespace, i| {
-                const component_enum = std.meta.FieldEnum(namespace.type);
-                fields[i] = .{
-                    .name = namespace.name,
-                    .type = component_enum,
-                    .alignment = @alignOf(component_enum),
-                };
-            }
-
-            // need type_info variable (rather than embedding in @Type() call)
-            // to work around stage 1 bug
-            const type_info = std.builtin.Type{
-                .Union = .{
-                    .layout = .Auto,
-                    .tag_type = std.meta.FieldEnum(@TypeOf(all_components)),
-                    .fields = &fields,
-                    .decls = &.{},
-                },
-            };
-            break :Query @Type(type_info);
-        };
-
-        fn fullComponentName(comptime q: Query) []const u8 {
-            return @tagName(q) ++ "." ++ @tagName(@field(q, @tagName(std.meta.activeTag(q))));
-        }
-
-        pub fn Iter(comptime components: []const Query) type {
-            return struct {
-                entities: *Self,
-                archetype_index: usize = 0,
-                row_index: u32 = 0,
-
-                const Iterator = @This();
-
-                pub const Entry = struct {
-                    entity: EntityID,
-
-                    pub fn unlock(e: Entry) void {
-                        _ = e;
-                    }
-                };
-
-                pub fn next(iter: *Iterator) ?Entry {
-                    const entities = iter.entities;
-
-                    // If the archetype table we're looking at does not contain the components we're
-                    // querying for, keep searching through tables until we find one that does.
-                    var archetype = entities.archetypes.entries.get(iter.archetype_index).value;
-                    while (!hasComponents(archetype, components) or iter.row_index >= archetype.len) {
-                        iter.archetype_index += 1;
-                        iter.row_index = 0;
-                        if (iter.archetype_index >= entities.archetypes.count()) {
-                            return null;
-                        }
-                        archetype = entities.archetypes.entries.get(iter.archetype_index).value;
-                    }
-
-                    const row_entity_id = archetype.get(iter.entities.allocator, iter.row_index, "id", EntityID).?;
-                    iter.row_index += 1;
-                    return Entry{ .entity = row_entity_id };
-                }
-            };
-        }
-
-        fn hasComponents(storage: ArchetypeStorage, comptime components: []const Query) bool {
-            var archetype = storage;
-            if (components.len == 0) return false;
-            inline for (components) |component| {
-                if (!archetype.hasComponent(fullComponentName(component))) return false;
-            }
-            return true;
-        }
-
-        pub fn query(entities: *Self, comptime components: []const Query) Iter(components) {
-            return Iter(components){
-                .entities = entities,
-            };
-        }
+        /// A complex query for entities matching a given criteria
+        pub const Query = query.Query(all_components);
 
         pub fn init(allocator: Allocator) !Self {
             var entities = Self{ .allocator = allocator };

libs/ecs/src/main.zig

@@ -32,6 +32,7 @@ pub const World = @import("systems.zig").World;
 
 test "inclusion" {
     std.testing.refAllDeclsRecursive(@This());
+    std.testing.refAllDeclsRecursive(@import("query.zig"));
 }
 
 test "example" {
@@ -87,5 +88,7 @@ test "example" {
     try physics.set(player2, .id, 1234);
     try physics.set(player3, .id, 1234);
 
+    //-------------------------------------------------------------------------
+    // Send events to modules
     try world.send(.tick);
 }

libs/ecs/src/query.zig

@@ -0,0 +1,113 @@
+const std = @import("std");
+const testing = std.testing;
+
+pub const QueryType = enum {
+    any,
+    all,
+};
+
+/// A complex query for entities matching a given criteria
+pub fn Query(comptime all_components: anytype) type {
+    return union(QueryType) {
+        /// Enum matching a namespace. e.g. `.game` or `.physics2d`
+        pub const Namespace = std.meta.FieldEnum(@TypeOf(all_components));
+
+        /// Enum matching a component within a namespace
+        /// e.g. `var a: Component(.physics2d) = .location`
+        pub fn Component(comptime namespace: Namespace) type {
+            return std.meta.FieldEnum(@TypeOf(@field(all_components, @tagName(namespace))));
+        }
+
+        /// Slice of enums matching a component within a namespace
+        /// e.g. `&.{.location, .rotation}`
+        pub fn ComponentList(comptime namespace: Namespace) type {
+            return []const Component(namespace);
+        }
+
+        /// Tagged union of namespaces matching lists of components
+        /// e.g. `.physics2d = .{ .location, .rotation }`
+        pub const NamespaceComponent = T: {
+            const namespaces = std.meta.fields(Namespace);
+            var fields: [namespaces.len]std.builtin.Type.UnionField = undefined;
+            inline for (namespaces, 0..) |namespace, i| {
+                const ns = std.meta.stringToEnum(Namespace, namespace.name).?;
+                fields[i] = .{
+                    .name = namespace.name,
+                    .type = ComponentList(ns),
+                    .alignment = @alignOf(ComponentList(ns)),
+                };
+            }
+
+            break :T @Type(.{ .Union = .{
+                .layout = .Auto,
+                .tag_type = Namespace,
+                .fields = &fields,
+                .decls = &.{},
+            } });
+        };
+
+        /// Matches entities with any of these components
+        any: []const NamespaceComponent,
+
+        /// Matches entities with all of these components
+        all: []const NamespaceComponent,
+    };
+}
+
+test "query" {
+    const Location = struct {
+        x: f32 = 0,
+        y: f32 = 0,
+        z: f32 = 0,
+    };
+
+    const Rotation = struct { degrees: f32 };
+
+    const all_components = .{
+        .game = .{
+            .name = []const u8,
+        },
+        .physics = .{
+            .location = Location,
+            .rotation = Rotation,
+        },
+    };
+
+    const Q = Query(all_components);
+
+    // Namespace type lets us select a single namespace.
+    try testing.expectEqual(@as(Q.Namespace, .game), .game);
+    try testing.expectEqual(@as(Q.Namespace, .physics), .physics);
+
+    // Component type lets us select a single component within a namespace.
+    try testing.expectEqual(@as(Q.Component(.physics), .location), .location);
+    try testing.expectEqual(@as(Q.Component(.game), .name), .name);
+
+    // ComponentList type lets us select multiple components within a namespace.
+    var x: Q.ComponentList(.physics) = &.{
+        .location,
+        .rotation,
+    };
+    _ = x;
+
+    // NamespaceComponent lets us select multiple components within multiple namespaces.
+    var y: []const Q.NamespaceComponent = &.{
+        .{ .physics = &.{ .location, .rotation } },
+        .{ .game = &.{.name} },
+    };
+    _ = y;
+
+    // Query matching entities with *any* of these components
+    var z: Q = .{ .any = &.{
+        .{ .physics = &.{ .location, .rotation } },
+        .{ .game = &.{.name} },
+    } };
+    _ = z;
+
+    // Query matching entities with *all* of these components.
+    var w: Q = .{ .all = &.{
+        .{ .physics = &.{ .location, .rotation } },
+        .{ .game = &.{.name} },
+    } };
+    _ = w;
+}