encompass-zig/src/component_manager.zig

const ComponentStore = @import("component_store.zig").ComponentStore;
const TypeStore = @import("type_store.zig").TypeStore;
const Entity = @import("entity.zig").Entity;

const std = @import("std");
const mem = std.mem;
const testing = std.testing;
const Allocator = mem.Allocator;

pub const ComponentManager = struct {
    const Self = @This();

    allocator: *Allocator,
    component_stores: TypeStore,

    pub fn init(allocator: *Allocator) Self {
        return Self {
            .allocator = allocator,
            .component_stores = TypeStore.init(allocator),
        };
    }

    pub fn deinit(self: *Self) void {
        var iter = self.component_stores.map.iterator();
        while (iter.next()) |ptr| {
            // HACK: we dont know the Type here but we need to call deinit
            var storage = @intToPtr(*ComponentStore(u1), ptr.value);
            storage.deinit();
            self.allocator.destroy(storage);
        }
        self.component_stores.deinit();
    }

    pub fn register(self: *Self, comptime TComponent: type) void {
        const ptr = ComponentStore(TComponent).heapInit(self.allocator);
        self.component_stores.add(ptr.*);
    }

    pub fn set_component(self: *Self, entityID: usize, component: anytype) void {
        self.component_stores.get(ComponentStore(@TypeOf(component))).*.set(entityID, component);
    }

    pub fn get_component(self: *Self, comptime TComponent: type, entityID: usize) !TComponent {
        return self.component_stores.get(ComponentStore(TComponent)).*.get(entityID) catch |err| return err;
    }

    pub fn has_component(self: *Self, comptime TComponent: type, entityID: usize) bool {
        return self.component_stores.get(ComponentStore(TComponent)).*.has(entityID);
    }

    pub fn remove_component(self: *Self, comptime TComponent: type, entityID: usize) void {
        return self.component_stores.get(ComponentStore(TComponent)).*.remove(entityID);
    }

    pub fn read_components(self: *Self, comptime TComponent: type) []TComponent {
        return self.component_stores.get(ComponentStore(TComponent)).*.all_components();
    }

    pub fn read_entities(self: *Self, comptime TComponent: type) []Entity {
        return self.component_stores.get(ComponentStore(TComponent)).*.all_entities();
    }
};

const TestComponent = struct {
    number: i32,
};

test "add component" {
    const component = TestComponent {
        .number = 3
    };

    var component_manager = ComponentManager.init(std.testing.allocator);
    defer component_manager.deinit();

    component_manager.register(TestComponent);

    component_manager.set_component(2, component);
    var expectedComponent = try component_manager.get_component(TestComponent, 2);
    expectedComponent.number = 5; // should be immutable!

    expectedComponent = try component_manager.get_component(TestComponent, 2);
    testing.expect(expectedComponent.number == 3);
}

test "has component" {
    const component = TestComponent {
        .number = 69
    };

    var component_manager = ComponentManager.init(std.testing.allocator);
    defer component_manager.deinit();

    component_manager.register(TestComponent);

    component_manager.set_component(420, component);

    testing.expect(component_manager.has_component(TestComponent, 420));
    testing.expect(!component_manager.has_component(TestComponent, 39));
}

test "remove component" {
    const component = TestComponent {
        .number = 3
    };

    const componentTwo = TestComponent {
        .number = 8
    };

    const componentThree = TestComponent {
        .number = 14
    };

    var component_manager = ComponentManager.init(std.testing.allocator);
    defer component_manager.deinit();

    component_manager.register(TestComponent);

    component_manager.set_component(2, component);
    component_manager.set_component(5, componentTwo);
    component_manager.set_component(52, componentThree);

    var components = component_manager.remove_component(TestComponent, 5);

    testing.expect(!component_manager.has_component(TestComponent, 5));
    testing.expect(component_manager.has_component(TestComponent, 52));
}

test "read components" {
    const component = TestComponent {
        .number = 3
    };

    const componentTwo = TestComponent {
        .number = 8
    };

    const componentThree = TestComponent {
        .number = 14
    };

    var component_manager = ComponentManager.init(std.testing.allocator);
    defer component_manager.deinit();

    component_manager.register(TestComponent);

    component_manager.set_component(2, component);
    component_manager.set_component(5, componentTwo);
    component_manager.set_component(52, componentThree);

    var components = component_manager.read_components(TestComponent);

    testing.expect(components[0].number == 3);
    testing.expect(components[1].number == 8);
    testing.expect(components[2].number == 14);
}

test "read entities" {
    const component = TestComponent {
        .number = 3
    };

    const componentTwo = TestComponent {
        .number = 8
    };

    const componentThree = TestComponent {
        .number = 14
    };

    var component_manager = ComponentManager.init(std.testing.allocator);
    defer component_manager.deinit();

    component_manager.register(TestComponent);

    component_manager.set_component(2, component);
    component_manager.set_component(5, componentTwo);
    component_manager.set_component(52, componentThree);

    var entities = component_manager.read_entities(TestComponent);

    testing.expect(entities[0].ID == 2);
    testing.expect(entities[1].ID == 5);
    testing.expect(entities[2].ID == 52);
}