using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using Implab.Diagnostics;

namespace Implab.ServiceHost.Unity {
    using static Trace<TypeResolver>;
    public class TypeResolver {
        readonly Dictionary<string, Type> m_cache = new Dictionary<string, Type>();

        Regex _nsRx = new Regex(@"^\w+(\.\w+)*$", RegexOptions.Compiled);
        readonly LinkedList<string> m_namespases = new LinkedList<string>();

        LinkedListNode<string> m_insertAt;

        readonly TypeResolver m_parent;

        public TypeResolver() : this(null) {

        }

        public TypeResolver(TypeResolver parent) {
            m_parent = parent;
            m_insertAt = new LinkedListNode<string>(string.Empty);
            m_namespases.AddFirst(m_insertAt);
        }

        public void AddNamespace(string ns) {
            Safe.ArgumentMatch(ns, nameof(ns), _nsRx);
            if (m_insertAt != null)
                m_namespases.AddAfter(m_insertAt, ns);
            else
                m_namespases.AddFirst(ns);
        }

        public void AddMapping(string typeName, Type type) {
            Safe.ArgumentNotEmpty(typeName, nameof(typeName));
            Safe.ArgumentNotNull(type, nameof(type));

            m_cache[typeName] = type;
        }

        public Type Resolve(TypeReference reference) {
            var args = reference.IsGeneric && !reference.IsOpenGeneric ? reference.GenericParameters?.Select(Resolve).ToArray() : null;
            var argc = reference.IsGeneric ? reference.GenericParameters.Length : 0;

            Type resolved;
            if (!m_cache.TryGetValue(reference.ToString(), out resolved)) {
                resolved = ResolveInternal(reference, args, argc);
                if (resolved == null)
                    throw new Exception($"Failed to resolve {reference}");
                m_cache[reference.ToString()] = resolved;
            }

            return resolved;
        }

        public Type Resolve(string typeSpec) {
            return Resolve(TypeReference.Parse(typeSpec));
        }

        Type ResolveInternal(TypeReference reference, Type[] args, int argc) {
            var resolved = ProbeInNamespaces(
                String.Join(".", new[] { reference.Namespace, reference.TypeName }.Where(x => !string.IsNullOrEmpty(x))),
                args,
                argc,
                reference.IsArray,
                reference.ToString()
            );

            if (resolved == null && m_parent != null)
                resolved = m_parent.ResolveInternal(reference, args, argc);

            return resolved;
        }

        public Type ProbeInNamespaces(string localName, Type[] args, int argc, bool isArray, string referenceName) {
            foreach (var ns in m_namespases) {
                var typeName = FormatName(new[] { ns, localName }, argc);

                var resolved = Probe(typeName);
                if (resolved != null) {
                    if (args != null && args.Length > 0) {
                        resolved = resolved.MakeGenericType(args);
                    }

                    if (isArray)
                        resolved = resolved.MakeArrayType();

                    Log("Probe succeed {0} in '{1}': {2} -> {3}", referenceName, ns, typeName, resolved.AssemblyQualifiedName);
                    return resolved;
                } else {
                    Log("Probe failed {0} in '{1}': {2}", referenceName, ns, typeName);
                }
            }

            return null;
        }

        Type Probe(string typeName) {
            var assemblies = AppDomain.CurrentDomain.GetAssemblies();

            foreach (var assembly in assemblies) {
                var type = assembly.GetType(typeName);
                if (type != null)
                    return type;
            }
            return null;
        }

        string FormatName(string[] parts, int argc) {
            var builder = new StringBuilder();

            builder.Append(String.Join(".", parts.Where(x => !string.IsNullOrEmpty(x))));
            if (argc > 0) {
                builder.Append('`');
                builder.Append(argc);
            }

            return builder.ToString();
        }
    }
}