// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading;

namespace Microsoft.ReactNative.Managed
{
  public class ReactModuleInfo
  {
    private static readonly object s_moduleInfoMutex = new object();
    private static Dictionary<Type, ReactModuleInfo> s_moduleInfos;
    private readonly Lazy<List<ReactInitializerInfo>> m_initializerInfos;
    private readonly Lazy<List<ReactConstantInfo>> m_constantInfos;
    private readonly Lazy<List<ReactConstantProviderInfo>> m_constantProviderInfos;
    private readonly Lazy<List<ReactMethodInfo>> m_methodInfos;
    private readonly Lazy<List<ReactSyncMethodInfo>> m_syncMethodInfos;
    private readonly Lazy<List<ReactFunctionInfo>> m_functionInfos;
    private readonly Lazy<List<ReactEventInfo>> m_eventInfos;

    public ReactModuleInfo(Type moduleType) : this(moduleType, moduleType.GetTypeInfo().GetCustomAttribute<ReactModuleAttribute>())
    {
    }

    public ReactModuleInfo(Type moduleType, ReactModuleAttribute moduleAttribute)
    {
      ModuleType = moduleType;
      ModuleName = GetModuleName(moduleType, moduleAttribute);
      EventEmitterName = moduleAttribute.EventEmitterName ?? "RCTDeviceEventEmitter";
      ModuleProvider = (IReactModuleBuilder moduleBuilder) =>
      {
        object module = Activator.CreateInstance(moduleType);
        AddModuleMembers(moduleBuilder, module);
        return module;
      };

      m_initializerInfos = new Lazy<List<ReactInitializerInfo>>(InitInitializerInfos, LazyThreadSafetyMode.PublicationOnly);
      m_constantInfos = new Lazy<List<ReactConstantInfo>>(InitConstantInfos, LazyThreadSafetyMode.PublicationOnly);
      m_constantProviderInfos = new Lazy<List<ReactConstantProviderInfo>>(InitConstantProviderInfos, LazyThreadSafetyMode.PublicationOnly);
      m_methodInfos = new Lazy<List<ReactMethodInfo>>(InitMethodInfos, LazyThreadSafetyMode.PublicationOnly);
      m_syncMethodInfos = new Lazy<List<ReactSyncMethodInfo>>(InitSyncMethodInfos, LazyThreadSafetyMode.PublicationOnly);
      m_functionInfos = new Lazy<List<ReactFunctionInfo>>(InitFunctionInfos, LazyThreadSafetyMode.PublicationOnly);
      m_eventInfos = new Lazy<List<ReactEventInfo>>(InitEventInfos, LazyThreadSafetyMode.PublicationOnly);
    }

    public static string GetModuleName(Type moduleType, ReactModuleAttribute moduleAttribute)
    {
      return moduleAttribute.ModuleName ?? moduleType.Name;
    }

    internal static ReactModuleInfo GetOrAddModuleInfo(Type moduleType, ReactModuleAttribute moduleAttribute)
    {
      lock (s_moduleInfoMutex)
      {
        if (s_moduleInfos is null)
        {
          s_moduleInfos = new Dictionary<Type, ReactModuleInfo>();
        }

        if (s_moduleInfos.TryGetValue(moduleType, out ReactModuleInfo moduleInfo))
        {
          return moduleInfo;
        }

        moduleInfo = new ReactModuleInfo(moduleType, moduleAttribute);
        s_moduleInfos.Add(moduleType, moduleInfo);
        return moduleInfo;
      }
    }

    private void AddModuleMembers(IReactModuleBuilder moduleBuilder, object module)
    {
      foreach (var constantInfo in m_constantInfos.Value)
      {
        constantInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var constantProviderInfo in m_constantProviderInfos.Value)
      {
        constantProviderInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var methodInfo in m_methodInfos.Value)
      {
        methodInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var syncMethodInfo in m_syncMethodInfos.Value)
      {
        syncMethodInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var eventInfo in m_eventInfos.Value)
      {
        eventInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var functionInfo in m_functionInfos.Value)
      {
        functionInfo.AddToModuleBuilder(moduleBuilder, module);
      }

      foreach (var initializerInfo in m_initializerInfos.Value)
      {
        initializerInfo.AddToModuleBuilder(moduleBuilder, module);
      }
    }

    private List<ReactInitializerInfo> InitInitializerInfos()
    {
      var initializers =
        from method in ModuleType.GetMethods(BindingFlags.Public | BindingFlags.Instance)
        let initializerAttribute = method.GetCustomAttribute<ReactInitializerAttribute>()
        where initializerAttribute != null
        select new ReactInitializerInfo(method);
      return initializers.ToList();
    }

    private List<ReactMethodInfo> InitMethodInfos()
    {
      var result = new List<ReactMethodInfo>();
      foreach (var method in ModuleType.GetMethods())
      {
        var methodAttribute = method.GetCustomAttribute<ReactMethodAttribute>();
        if (methodAttribute != null)
        {
          var methodInfo = new ReactMethodInfo(method, methodAttribute);
          result.Add(methodInfo);
        }
      }

      return result;
    }

    private List<ReactSyncMethodInfo> InitSyncMethodInfos()
    {
      var result = new List<ReactSyncMethodInfo>();
      foreach (var method in ModuleType.GetMethods())
      {
        var syncMethodAttribute = method.GetCustomAttribute<ReactSyncMethodAttribute>();
        if (syncMethodAttribute != null)
        {
          var syncMethodInfo = new ReactSyncMethodInfo(method, syncMethodAttribute);
          result.Add(syncMethodInfo);
        }
      }

      return result;
    }

    private List<ReactFunctionInfo> InitFunctionInfos()
    {
      var fieldEvents =
        from field in ModuleType.GetFields(BindingFlags.Public | BindingFlags.Instance)
        let functionAttribute = field.GetCustomAttribute<ReactFunctionAttribute>()
        where functionAttribute != null && !field.IsInitOnly
        select new ReactFunctionInfo(field, functionAttribute, ModuleName);
      var propertyEvents =
        from property in ModuleType.GetProperties(BindingFlags.Public | BindingFlags.Instance)
        let functionAttribute = property.GetCustomAttribute<ReactFunctionAttribute>()
        where functionAttribute != null
        let propertySetter = property.SetMethod
        where propertySetter != null && propertySetter.IsPublic
        select new ReactFunctionInfo(property, functionAttribute, ModuleName);
      return fieldEvents.Concat(propertyEvents).ToList();
    }

    private List<ReactEventInfo> InitEventInfos()
    {
      var fieldEvents =
        from field in ModuleType.GetFields(BindingFlags.Public | BindingFlags.Instance)
        let eventAttribute = field.GetCustomAttribute<ReactEventAttribute>()
        where eventAttribute != null && !field.IsInitOnly
        select new ReactEventInfo(field, eventAttribute, EventEmitterName);
      var propertyEvents =
        from property in ModuleType.GetProperties(BindingFlags.Public | BindingFlags.Instance)
        let eventAttribute = property.GetCustomAttribute<ReactEventAttribute>()
        where eventAttribute != null
        let propertySetter = property.SetMethod
        where propertySetter != null && propertySetter.IsPublic
        select new ReactEventInfo(property, eventAttribute, EventEmitterName);
      return fieldEvents.Concat(propertyEvents).ToList();
    }

    private List<ReactConstantInfo> InitConstantInfos()
    {
      var fieldConstants =
        from field in ModuleType.GetFields(BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static)
        let constantAttribute = field.GetCustomAttribute<ReactConstantAttribute>()
        where constantAttribute != null
        let constantInfo = new ReactConstantInfo(field, constantAttribute)
        select constantInfo;
      var propertyEvents =
        from property in ModuleType.GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static)
        let constantAttribute = property.GetCustomAttribute<ReactConstantAttribute>()
        where constantAttribute != null
        let constantInfo = new ReactConstantInfo(property, constantAttribute)
        select constantInfo;
      return fieldConstants.Concat(propertyEvents).ToList();
    }

    private List<ReactConstantProviderInfo> InitConstantProviderInfos()
    {
      var constantProviders =
        from method in ModuleType.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static)
        let constantProviderAttribute = method.GetCustomAttribute<ReactConstantProviderAttribute>()
        where constantProviderAttribute != null
        select new ReactConstantProviderInfo(method);
      return constantProviders.ToList();
    }

    public Type ModuleType { get; private set; }

    public string ModuleName { get; private set; }

    public string EventEmitterName { get; private set; }

    public ReactModuleProvider ModuleProvider { get; private set; }
  }
}