[WIP] API for config instance builder

Fixes smallrye#1001

implementation/src/main/java/io/smallrye/config/ConfigInstanceBuilder.java

@@ -0,0 +1,311 @@
+package io.smallrye.config;
+
+import java.io.Serializable;
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.function.ToIntFunction;
+import java.util.function.ToLongFunction;
+
+/**
+ * A builder which can produce instances of a configuration interface.
+ * <p>
+ * Objects which are produced by this API will contain values for every property found on the configuration
+ * interface or its supertypes.
+ * If no value is given for a property, its default value is used.
+ * If a required property has no default value, then an exception will be thrown when {@link #build} is called.
+ * The returned object instance is immutable and has a stable {@code equals} and {@code hashCode} method.
+ * If the runtime is Java 16 or later, the returned object <em>may</em> be a {@code Record}.
+ * <p>
+ * To provide a value for a property, use a method reference to indicate which property the value should be associated
+ * with.
+ * For example,
+ * <pre><code>
+ * ConfigInstanceBuilder&lt;MyProgramConfig&gt; builder = ConfigInstanceBuilder.forInterface(MyProgramConfig.class);
+ * builder.with(MyProgramConfig::message, "Hello everyone!");
+ * builder.with(MyProgramConfig::repeatCount, 42);
+ * MyProgramConfig config = builder.build();
+ * for (int i = 0; i < config.repeatCount(); i ++) {
+ *     System.out.println(config.message());
+ * }
+ * </code></pre>
+ *
+ * @param <I> the configuration interface type
+ */
+public interface ConfigInstanceBuilder<I> {
+    /**
+     * {@return the configuration interface (not <code>null</code>)}
+     */
+    Class<I> configurationInterface();
+
+    /**
+     * Set a property on the configuration object to an object value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <T> the value type
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null}
+     *      or if the value is {@code null}
+     */
+    <T, F extends Function<? super I, T> & Serializable> ConfigInstanceBuilder<I> with(F getter, T value);
+
+    /**
+     * Set a property on the configuration object to an integer value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends ToIntFunction<? super I> & Serializable> ConfigInstanceBuilder<I> with(F getter, int value);
+
+    /**
+     * Set a property on the configuration object to an integer value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends ToLongFunction<? super I> & Serializable> ConfigInstanceBuilder<I> with(F getter, long value);
+
+    /**
+     * Set a property on the configuration object to a floating-point value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends ToLongFunction<? super I> & Serializable> ConfigInstanceBuilder<I> with(F getter, double value);
+
+    /**
+     * Set a property on the configuration object to a boolean value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends Predicate<? super I> & Serializable> ConfigInstanceBuilder<I> with(F getter, boolean value);
+
+    /**
+     * Set an optional property on the configuration object to an object value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value  the value to set (must not be {@code null})
+     * @param <T>    the value type
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     *      or the value is {@code null}
+     */
+    default <T, F extends Function<? super I, Optional<T>> & Serializable> ConfigInstanceBuilder<I> withOptional(F getter, T value) {
+        return with(getter, Optional.of(value));
+    }
+
+    /**
+     * Set an optional property on the configuration object to an integer value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value  the value to set (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    default <F extends Function<? super I, OptionalInt> & Serializable> ConfigInstanceBuilder<I> withOptional(F getter, int value) {
+        return with(getter, OptionalInt.of(value));
+    }
+
+    /**
+     * Set an optional property on the configuration object to an integer value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value  the value to set (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    default <F extends Function<? super I, OptionalLong> & Serializable> ConfigInstanceBuilder<I> withOptional(F getter, long value) {
+        return with(getter, OptionalLong.of(value));
+    }
+
+    /**
+     * Set an optional property on the configuration object to a floating-point value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value  the value to set (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    default <F extends Function<? super I, OptionalDouble> & Serializable> ConfigInstanceBuilder<I> withOptional(F getter, double value) {
+        return with(getter, OptionalDouble.of(value));
+    }
+
+    /**
+     * Set an optional property on the configuration object to a boolean value.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value  the value to set (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    default <F extends Function<? super I, Optional<Boolean>> & Serializable> ConfigInstanceBuilder<I> withOptional(F getter, boolean value) {
+        return with(getter, Optional.of(Boolean.valueOf(value)));
+    }
+
+    /**
+     * Set a property to its default value (if any).
+     *
+     * @param getter the property to modify (must not be {@code null})
+     * @param <T>    the value type
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <T, F extends Function<? super I, T> & Serializable> ConfigInstanceBuilder<I> withDefaultFor(F getter);
+
+    /**
+     * Set a property to its default value (if any).
+     *
+     * @param getter the property to modify (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends ToIntFunction<? super I> & Serializable> ConfigInstanceBuilder<I> withDefaultFor(F getter);
+
+    /**
+     * Set a property to its default value (if any).
+     *
+     * @param getter the property to modify (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends ToLongFunction<? super I> & Serializable> ConfigInstanceBuilder<I> withDefaultFor(F getter);
+
+    /**
+     * Set a property to its default value (if any).
+     *
+     * @param getter the property to modify (must not be {@code null})
+     * @param <F>    the accessor type
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the getter is {@code null}
+     */
+    <F extends Predicate<? super I> & Serializable> ConfigInstanceBuilder<I> withDefaultFor(F getter);
+
+    /**
+     * Set a property on the configuration object to a string value.
+     * The value set on the property will be the result of conversion of the string
+     * using the property's converter.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null},
+     *       or if the value is {@code null},
+     *       or if the value was rejected by the converter
+     */
+    <F extends Function<? super I, ?> & Serializable> ConfigInstanceBuilder<I> withString(F getter, String value);
+
+    /**
+     * Set a property on the configuration object to a string value.
+     * The value set on the property will be the result of conversion of the string
+     * using the property's converter.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null},
+     *       or if the value is {@code null},
+     *       or if the value was rejected by the converter
+     */
+    <F extends ToIntFunction<? super I> & Serializable> ConfigInstanceBuilder<I> withString(F getter, String value);
+
+    /**
+     * Set a property on the configuration object to a string value.
+     * The value set on the property will be the result of conversion of the string
+     * using the property's converter.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null},
+     *       or if the value is {@code null},
+     *       or if the value was rejected by the converter
+     */
+    <F extends ToLongFunction<? super I> & Serializable> ConfigInstanceBuilder<I> withString(F getter, String value);
+
+    /**
+     * Set a property on the configuration object to a string value.
+     * The value set on the property will be the result of conversion of the string
+     * using the property's converter.
+     *
+     * @param getter the property accessor (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @param <F> the accessor type
+     * @throws IllegalArgumentException if the getter is {@code null},
+     *       or if the value is {@code null},
+     *       or if the value was rejected by the converter
+     */
+    <F extends Predicate<? super I> & Serializable> ConfigInstanceBuilder<I> withString(F getter, String value);
+
+    /**
+     * Set a property on the configuration object to a string value, using the property's
+     * declaring class and name to identify the property to set.
+     * The value set on the property will be the result of conversion of the string
+     * using the property's converter.
+     *
+     * @param propertyClass the declaring class of the property to set (must not be {@code null})
+     * @param propertyName the name of the property to set (must not be {@code null})
+     * @param value the value to set (must not be {@code null})
+     * @return this builder (not {@code null})
+     * @throws IllegalArgumentException if the property class or name is {@code null},
+     *       or if the value is {@code null},
+     *       or if the value was rejected by the converter,
+     *       or if no property matches the given name and declaring class
+     */
+    ConfigInstanceBuilder<I> withString(Class<? super I> propertyClass, String propertyName, String value);
+
+    /**
+     * Build the configuration instance.
+     *
+     * @return the configuration instance (not {@code null})
+     * @throws IllegalArgumentException if a required property does not have a value
+     */
+    I build();
+
+    /**
+     * Get a builder instance for the given configuration interface.
+     *
+     * @param interfaceClass the interface class object (must not be {@code null})
+     * @param <I> the configuration interface type
+     * @return a new builder for the configuration interface (not {@code null})
+     * @throws IllegalArgumentException if the interface class is {@code null},
+     *      or if the class object does not represent an interface,
+     *      or if the interface is not a valid configuration interface,
+     *      or if the interface has one or more required properties that were not given a value,
+     *      or if the interface has one or more converters that could not be instantiated
+     * @throws SecurityException if this class does not have permission to introspect the given interface
+     *      or one of its superinterfaces
+     */
+    static <I> ConfigInstanceBuilder<I> forInterface(Class<I> interfaceClass) throws IllegalArgumentException, SecurityException {
+        throw new UnsupportedOperationException("todo");
+    }
+}