Add world.term (temporary?)

src/world.zig

@@ -209,6 +209,41 @@ pub fn World(comptime ctx: anytype) type {
             }
         };
 
+        /// Creates a term iterator which allows querying for all entities
+        /// that have a specific `Id`. This function supports wildcards.
+        pub fn term(self: *Self, id: anytype) TermIterator {
+            const id_ = util.anyToId(ctx, id);
+            var term_ = std.mem.zeroInit(c.ecs_term_t, .{ .id = id_ });
+            const iter = c.ecs_term_iter(self.raw, &term_);
+            return .{ .world = self, .iter = iter };
+        }
+
+        // TODO: Move this logic to `Iter`, add `TermIter` type?
+        // TODO: Rename `Iter` to `Iterator`?
+        pub const TermIterator = struct {
+            world: *World(ctx),
+            iter: c.ecs_iter_t,
+            index: i32 = 0,
+
+            pub fn next(self: *TermIterator) ?Entity(ctx) {
+                if (self.index >= self.iter.count)
+                    if (!c.ecs_term_next(&self.iter))
+                        return null;
+
+                const result = self.iter.entities[@intCast(self.index)];
+                self.index += 1;
+                return Entity(ctx).fromRaw(self.world, result);
+            }
+
+            // TODO: Check where else in the codebase it would make sense to have `deinit` take a pointer?
+            pub fn deinit(self: *TermIterator) void {
+                // Finalize the iterator if it hasn't run to completion.
+                if ((self.iter.flags & c.EcsIterIsValid) != 0)
+                    c.ecs_iter_fini(&self.iter);
+                self.* = undefined;
+            }
+        };
+
         /// Gets the current scope of this `World`. See also: `setScope()`.
         pub fn getScope(self: *Self) ?Entity(ctx) {
             const result = c.ecs_get_scope(self.raw);