Invercargill/src/lib/Mapping/PropertyMapper.vala

using Invercargill.DataStructures;
namespace Invercargill.Mapping {

    public delegate TProp PropertyGetter<TClass, TProp>(TClass object) throws Error;
    public delegate bool PropertyPredicate<TClass>(TClass object);
    public delegate void PropertySetter<TClass, TProp>(TClass object, TProp value) throws Error;
    public delegate void PropertyDefaultSetter<TClass>(TClass object);
    public delegate TOut PropertyGetterTransformer<TIn, TOut>(TIn object);
    public delegate TOut PropertySetterTransformer<TIn, TOut>(TIn object) throws Error;
    public delegate T ObjectConstructor<T>();
    public class PropertyMapper<T> : Object, Mapper<T, Properties> {

        private Vector<PropertyMapping<T>> mappings;
        private ObjectConstructor<T>? constructor;

        public static PropertyMapper<T> build_for<T>(Func<PropertyMapperBuilder<T>> func) {
            int location = (int)func;
            return keyed_once<PropertyMapper<T>>(location, () => {
                var builder = new PropertyMapperBuilder<T>();
                func(builder);
                return builder.build();
            });
        }

        internal PropertyMapper(Vector<PropertyMapping<T>> mappings, ObjectConstructor<T>? constructor) {
            this.mappings = mappings;
            this.constructor = constructor;
        }

        public void map_into(T object, ReadOnlyAssociative<string, Element> properties) throws Error {
            foreach (var mapping in mappings) {
                var exists = properties.has(mapping.name);
                if(mapping.undefined_setter != null && !exists) {
                    mapping.undefined_setter(object);
                    continue;
                }
                if(mapping.undefined_setter == null && !exists){
                    throw new IndexError.KEY_NOT_FOUND(@"Failed to map into $(typeof(T).name()): Property \"$(mapping.name)\" does not have an undefined setter and no matching property was found");
                }
                var element = properties[mapping.name];
                if(mapping.null_setter != null && element.is_null()) {
                    mapping.null_setter(object);
                    continue;
                }
                if(mapping.null_setter == null && element.is_null()) {
                    throw new ElementError.INVALID_CONVERSION(@"Failed to map into $(typeof(T).name()): Property \"$(mapping.name)\" does not have a null setter and a null value was found");
                }
                mapping.setter(object, properties[mapping.name]);
            }
        }

        public T materialise(Properties properties) throws Error {
            var obj = constructor != null ? constructor() : (T) Object.new(typeof(T));
            map_into(obj, properties);
            return obj;
        }

        public Properties map_from(T object) throws Error {
            var properties = new PropertyDictionary();
            foreach (var mapping in mappings) {
                // Check undefined
                if(mapping.undefined_check != null && mapping.undefined_check(object)){
                    continue;
                }

                // Check null
                if(mapping.null_check != null && mapping.null_check(object)) {
                    properties[mapping.name] = new NullElement();
                    continue;
                }

                // Assign value
                var val = mapping.getter(object);
                properties[mapping.name] = val;
            }
            return properties;
        }

    }

    private class PropertyMapping<T> {
        public string name;
        public PropertyGetter<T, Element> getter;
        public PropertySetter<T, Element> setter;
        public PropertyPredicate<T>? null_check;
        public PropertyPredicate<T>? undefined_check;
        public PropertyDefaultSetter<T>? null_setter;
        public PropertyDefaultSetter<T>? undefined_setter;
    }

    public class PropertyMapperBuilder<T> {

        private Vector<PropertyMapping<T>> mappings;
        private ObjectConstructor<T> constructor;

        public PropertyMapperBuilder() {
            mappings = new Vector<PropertyMapping<T>>();
            // No default constructor closure: a lambda capturing `this` would
            // dangle once the (usually transient) builder is finalized while
            // the built PropertyMapper lives on. materialise() falls back to
            // the mapper's own T when no constructor was set.
            constructor = null;
        }

        public virtual PropertyMappingBuilder<T> map<TProp>(string name, owned PropertyGetter<T, TProp> getter, owned PropertySetter<T, TProp> setter) {
            PropertyMapping<T> mapping;
            if(typeof(TProp).is_a(typeof(Element))) {
                mapping = new PropertyMapping<T>() {
                    name = name,
                    getter = (owned)getter,
                    setter = (owned)setter,
                };
            }
            else {
                mapping = new PropertyMapping<T>() {
                    name = name,
                    getter = (o) => new NativeElement<TProp>(getter(o)),
                    setter = (o,d) => setter(o, d.as<TProp>())
                };
            }
            add_mapping(mapping);
            return new PropertyMappingBuilder<T>(this, mapping);
        }

        public virtual PropertyMappingBuilder<T> map_properties_with<TObj>(string name, owned PropertyGetter<T, TObj> getter, owned PropertySetter<T, TObj> setter, PropertyMapper<TObj> mapper) {
            return map_with<TObj, Properties>(name, getter, setter, mapper);
        }

        public virtual PropertyMappingBuilder<T> map_with<TNative, TElement>(string name, owned PropertyGetter<T, TNative> getter, owned PropertySetter<T, TNative> setter, Mapper<TNative, TElement> mapper) {
            var mapping = new PropertyMapping<T>() {
                name = name,
                getter = (o) => new NativeElement<TElement>(mapper.map_from(getter(o))),
                setter = (o,d) => setter(o, mapper.materialise(d.as<TElement>()))
            };
            add_mapping(mapping);
            return new PropertyMappingBuilder<T>(this, mapping);
        }

        public virtual PropertyMappingBuilder<T> map_many<TObj>(string name, owned PropertyGetter<T, Enumerable<TObj>> getter, owned PropertySetter<T, Enumerable<TObj>> setter) {
            var mapping = new PropertyMapping<T>() {
                name = name,
                getter = (o) => new NativeElement<Elements>(getter(o).to_elements()),
                setter = (o,d) => setter(o, d.as<Elements>().elements_as<TObj>())
            };
            add_mapping(mapping);
            return new PropertyMappingBuilder<T>(this, mapping);;
        }

        public virtual PropertyMappingBuilder<T> map_property_groups_with<TObj>(string name, owned PropertyGetter<T, Enumerable<TObj>> getter, owned PropertySetter<T, Enumerable<TObj>> setter, PropertyMapper<TObj> mapper) {
            return map_many_with<TObj, Properties>(name, getter, setter, mapper);
        }

        public virtual PropertyMappingBuilder<T> map_many_with<TNative, TElement>(string name, owned PropertyGetter<T, Enumerable<TNative>> getter, owned PropertySetter<T, Enumerable<TNative>> setter, Mapper<TNative, TElement> mapper) {
            var mapping = new PropertyMapping<T>() {
                name = name,
                getter = (o) => new NativeElement<Elements>(getter(o).attempt_select<TElement>(i => mapper.map_from(i)).to_elements()),
                setter = (o,d) => {
                    var collection = new Series<TNative>();
                    foreach (var properties in d.as<Elements>().elements_as<TElement>()) {
                        collection.add(mapper.materialise(properties));
                    }
                    setter(o, collection.seal());
                }
            };
            add_mapping(mapping);
            return new PropertyMappingBuilder<T>(this, mapping);
        }

        public virtual PropertyMapperBuilder<T> set_constructor(ObjectConstructor<T> constructor) {
            this.constructor = constructor;
            return this;
        }

        public virtual PropertyMapper<T> build() {
            return new PropertyMapper<T>(mappings, constructor);
        }

        private void add_mapping(PropertyMapping<T> mapping) {
            mappings.add(mapping);
        }
    }


    public class PropertyMappingBuilder<T> : PropertyMapperBuilder<T> {
        private PropertyMapperBuilder<T> inner;
        private PropertyMapping<T> mapping;
        internal PropertyMappingBuilder(PropertyMapperBuilder<T> builder, PropertyMapping<T> mapping) {
            inner = builder;
            this.mapping = mapping;
        }

        public PropertyMappingBuilder<T> null_when(owned PropertyPredicate<T> predicate) {
            mapping.null_check = predicate;
            return this;
        }

        public PropertyMappingBuilder<T> undefined_when(owned PropertyPredicate<T> predicate) {
            mapping.undefined_check = predicate;
            return this;
        }

        public PropertyMappingBuilder<T> when_null(owned PropertyDefaultSetter<T> setter) {
            mapping.null_setter = setter;
            return this;
        }
        
        public PropertyMappingBuilder<T> when_undefined(owned PropertyDefaultSetter<T> setter) {
            mapping.undefined_setter = setter;
            return this;
        }

        public override PropertyMappingBuilder<T> map<TProp>(string name, owned PropertyGetter<T, TProp> getter, owned PropertySetter<T, TProp> setter) {
            return inner.map<TProp>(name, (owned)getter, (owned)setter);
        }

        public override PropertyMappingBuilder<T> map_properties_with<TObj>(string name, owned PropertyGetter<T, TObj> getter, owned PropertySetter<T, TObj> setter, PropertyMapper<TObj> mapper) {
            return inner.map_properties_with<TObj>(name, (owned)getter, (owned)setter, mapper);
        }

        public override PropertyMappingBuilder<T> map_with<TNative, TElement>(string name, owned PropertyGetter<T, TNative> getter, owned PropertySetter<T, TNative> setter, Mapper<TNative, TElement> mapper) {
            return inner.map_with<TNative, TElement>(name, (owned)getter, (owned)setter, mapper);
        }

        public override PropertyMappingBuilder<T> map_many<TObj>(string name, owned PropertyGetter<T, Enumerable<TObj>> getter, owned PropertySetter<T, Enumerable<TObj>> setter) {
            return inner.map_many<TObj>(name, (owned)getter, (owned)setter);
        }

        public override PropertyMappingBuilder<T> map_property_groups_with<TObj>(string name, owned PropertyGetter<T, Enumerable<TObj>> getter, owned PropertySetter<T, Enumerable<TObj>> setter, PropertyMapper<TObj> mapper) {
            return inner.map_property_groups_with<TObj>(name, getter, setter, mapper);
        }

        public override PropertyMappingBuilder<T> map_many_with<TNative, TElement>(string name, owned PropertyGetter<T, Enumerable<TNative>> getter, owned PropertySetter<T, Enumerable<TNative>> setter, Mapper<TNative, TElement> mapper) {
            return inner.map_many_with<TNative, TElement>(name, (owned)getter, (owned)setter, mapper);
        }

        public override PropertyMapperBuilder<T> set_constructor(ObjectConstructor<T> constructor) {
            return inner.set_constructor(constructor);
        }

        public override PropertyMapper<T> build() {
            return inner.build();
        }

    }
}