initial commit

java/expression/common/Renderer.java

@@ -0,0 +1,60 @@
+package expression.common;
+
+import base.Functional;
+import base.Pair;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/**
+ * @author Georgiy Korneev (kgeorgiy@kgeorgiy.info)
+ */
+public interface Renderer<C, S, R> {
+    static <C, S, R> Builder<C, S, R> builder(final Node.Const<C, R> constant) {
+        return new Builder<>(constant);
+    }
+
+    R render(final Expr<C, R> expr, final S settings);
+
+    @FunctionalInterface
+    interface UnaryOperator<S, R> {
+        R apply(S settings, R arg);
+    }
+
+    @FunctionalInterface
+    interface BinaryOperator<S, R> {
+        R apply(S settings, R arg1, R arg2);
+    }
+
+    final class Builder<C, S, R> {
+        private final Node.Const<C, R> constant;
+        private final Map<String, UnaryOperator<S, R>> unary = new HashMap<>();
+        private final Map<String, BinaryOperator<S, R>> binary = new HashMap<>();
+
+        private Builder(final Node.Const<C, R> constant) {
+            this.constant = constant;
+        }
+
+        public void unary(final String name, final UnaryOperator<S, R> op) {
+            unary.put(name, op);
+        }
+
+        public void binary(final String name, final BinaryOperator<S, R> op) {
+            binary.put(name, op);
+        }
+
+        public Renderer<C, S, R> build() {
+            return (expr, settings) -> {
+                final Map<String, R> vars = expr.variables().stream()
+                        .collect(Collectors.toMap(Pair::first, Pair::second));
+                return expr.node().cata(
+                        constant,
+                        name -> Functional.get(vars, name),
+                        (name, p, arg) -> Functional.get(unary, name).apply(settings, arg),
+                        (name, arg1, arg2) -> Functional.get(binary, name).apply(settings, arg1, arg2)
+                );
+            };
+        }
+    }
+}