using System;
using System.Collections.Generic;
using System.Linq;
using Unity.Injection;
using Unity.Registration;

namespace Implab.ServiceHost.Unity {
    public class TypeRegistrationBuilder : RegistrationBuilder {

        readonly TypeResolver m_resolver;

        readonly List<InjectionMember> m_injections = new List<InjectionMember>();

        public InjectionMember[] Injections { get { return m_injections.ToArray(); } }

        public Type ImplementationType {
            get;
            private set;
        }

        internal TypeRegistrationBuilder(TypeResolver resolver, Type registrationType, Type implementationType) : base(registrationType) {
            ImplementationType = implementationType;

            // when registering a generic mapping, register all generic parameter names as local types
            if (ImplementationType.IsGenericTypeDefinition) {
                m_resolver = new TypeResolver(resolver);

                foreach (var p in ImplementationType.GetGenericArguments())
                    m_resolver.AddMapping(p.Name, p);
            } else {
                m_resolver = resolver;
            }
        }

        internal void Visit(ConstructorInjectionElement constructorInjection) {
            

            var parameters = constructorInjection.Parameters?
                .Select(x => {
                    var valueBuilder = new InjectionValueBuilder(m_resolver, null);
                    x.Visit(valueBuilder);
                    return valueBuilder.Injection;
                })
                .ToArray();

            var injection = parameters != null ? new InjectionConstructor(parameters) : new InjectionConstructor();
            m_injections.Add(injection);
        }

        internal void Visit(MethodInjectionElement methodInjection) {
            var valueContext = new InjectionValueBuilder(m_resolver, null);

            var parameters = methodInjection.Parameters?
                .Select(x => {
                    var valueBuilder = new InjectionValueBuilder(m_resolver, null);
                    x.Visit(valueBuilder);
                    return valueBuilder.Injection;
                })
                .ToArray();

            var injection = parameters != null ? new InjectionMethod(methodInjection.Name, parameters) : new InjectionMethod(methodInjection.Name);
            m_injections.Add(injection);
        }

        internal void Visit(PropertyInjectionElement propertyInjection) {
            if (propertyInjection.Value == null)
                throw new Exception($"A value value must be specified for the property '{propertyInjection.Name}'");

            var propertyType = RegistrationType.GetProperty(propertyInjection.Name)?.PropertyType;
            var valueContext = new InjectionValueBuilder(m_resolver, propertyType);

            propertyInjection.Value.Visit(valueContext);
            var injection = new InjectionProperty(propertyInjection.Name, valueContext.Injection);
            m_injections.Add(injection);
        }
    }
}