feat(logic): add block_height/1 predicate

x/logic/predicate/block.go

@@ -0,0 +1,25 @@
+package predicate
+
+import (
+	"context"
+
+	"github.com/ichiban/prolog/engine"
+)
+
+// BlockHeight is higher order function that given a context returns the following predicate:
+//
+//	block_height(?Height)
+//
+// where Height represents the current chain height at the time of the query.
+// The predicate is non-deterministic, producing a different height each time it is called.
+func BlockHeight(ctx context.Context) engine.Predicate1 {
+	return func(vm *engine.VM, height engine.Term, cont engine.Cont, env *engine.Env) *engine.Promise {
+		sdkContext, err := UnwrapSDKContext(ctx)
+		if err != nil {
+			return engine.Error(err)
+		}
+
+		return engine.Unify(vm, height, engine.Integer(sdkContext.BlockHeight()), cont, env)
+	}
+}
+