// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Text.Json.Reflection;
using System.Text.Json.Serialization;
using System.Text.Json.Serialization.Metadata;
 
namespace System.Text.Json
{
    public static partial class JsonSerializer
    {
        /// <summary>
        /// Lookup the property given its name (obtained from the reader) and return it.
        /// Also sets state.Current.JsonPropertyInfo to a non-null value.
        /// </summary>
        internal static JsonPropertyInfo LookupProperty(
            object? obj,
            ReadOnlySpan<byte> unescapedPropertyName,
            ref ReadStack state,
            JsonSerializerOptions options,
            out bool useExtensionProperty,
            bool createExtensionProperty = true)
        {
            JsonTypeInfo jsonTypeInfo = state.Current.JsonTypeInfo;
            useExtensionProperty = false;
 
            JsonPropertyInfo? jsonPropertyInfo = jsonTypeInfo.GetProperty(
                unescapedPropertyName,
                ref state.Current,
                out byte[] utf8PropertyName);
 
            // Increment PropertyIndex so GetProperty() checks the next property first when called again.
            state.Current.PropertyIndex++;
 
            // For case insensitive and missing property support of JsonPath, remember the value on the temporary stack.
            state.Current.JsonPropertyName = utf8PropertyName;
 
            // Handle missing properties
            if (jsonPropertyInfo is null)
            {
                if (jsonTypeInfo.EffectiveUnmappedMemberHandling is JsonUnmappedMemberHandling.Disallow)
                {
                    Debug.Assert(jsonTypeInfo.ExtensionDataProperty is null, "jsonTypeInfo.Configure() should have caught conflicting configuration.");
                    string stringPropertyName = Encoding.UTF8.GetString(unescapedPropertyName);
                    ThrowHelper.ThrowJsonException_UnmappedJsonProperty(jsonTypeInfo.Type, stringPropertyName);
                }
 
                // Determine if we should use the extension property.
                if (jsonTypeInfo.ExtensionDataProperty is JsonPropertyInfo { HasGetter: true, HasSetter: true } dataExtProperty)
                {
                    state.Current.JsonPropertyNameAsString = Encoding.UTF8.GetString(unescapedPropertyName);
 
                    if (createExtensionProperty)
                    {
                        Debug.Assert(obj != null, "obj is null");
                        CreateExtensionDataProperty(obj, dataExtProperty, options);
                    }
 
                    jsonPropertyInfo = dataExtProperty;
                    useExtensionProperty = true;
                }
                else
                {
                    // Populate with a placeholder value required by JsonPath calculations
                    jsonPropertyInfo = JsonPropertyInfo.s_missingProperty;
                }
            }
 
            state.Current.JsonPropertyInfo = jsonPropertyInfo;
            state.Current.NumberHandling = jsonPropertyInfo.EffectiveNumberHandling;
            return jsonPropertyInfo;
        }
 
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static ReadOnlySpan<byte> GetPropertyName(
            scoped ref ReadStack state,
            ref Utf8JsonReader reader,
            JsonSerializerOptions options,
            out bool isAlreadyReadMetadataProperty)
        {
            ReadOnlySpan<byte> propertyName = reader.GetUnescapedSpan();
            isAlreadyReadMetadataProperty = false;
 
            if (state.Current.CanContainMetadata)
            {
                if (IsMetadataPropertyName(propertyName, state.Current.BaseJsonTypeInfo.PolymorphicTypeResolver))
                {
                    if (options.AllowOutOfOrderMetadataProperties)
                    {
                        isAlreadyReadMetadataProperty = true;
                    }
                    else
                    {
                        ThrowHelper.ThrowUnexpectedMetadataException(propertyName, ref reader, ref state);
                    }
                }
            }
 
            return propertyName;
        }
 
        internal static void CreateExtensionDataProperty(
            object obj,
            JsonPropertyInfo jsonPropertyInfo,
            JsonSerializerOptions options)
        {
            Debug.Assert(jsonPropertyInfo != null);
 
            object? extensionData = jsonPropertyInfo.GetValueAsObject(obj);
 
            // For IReadOnlyDictionary, if there's an existing non-null instance, we need to create a new mutable
            // Dictionary seeded with the existing contents so we can add the deserialized extension data to it.
            bool isReadOnlyDictionary = jsonPropertyInfo.PropertyType == typeof(IReadOnlyDictionary<string, object>) ||
                                        jsonPropertyInfo.PropertyType == typeof(IReadOnlyDictionary<string, JsonElement>);
 
            if (extensionData == null || (isReadOnlyDictionary && extensionData != null))
            {
                // Create the appropriate dictionary type. We already verified the types.
#if DEBUG
                Type? underlyingIDictionaryType = jsonPropertyInfo.PropertyType.GetCompatibleGenericInterface(typeof(IDictionary<,>))
                    ?? jsonPropertyInfo.PropertyType.GetCompatibleGenericInterface(typeof(IReadOnlyDictionary<,>));
                Debug.Assert(underlyingIDictionaryType is not null);
                Type[] genericArgs = underlyingIDictionaryType.GetGenericArguments();
 
                Debug.Assert(underlyingIDictionaryType.IsGenericType);
                Debug.Assert(genericArgs.Length == 2);
                Debug.Assert(genericArgs[0].UnderlyingSystemType == typeof(string));
                Debug.Assert(
                    genericArgs[1].UnderlyingSystemType == JsonTypeInfo.ObjectType ||
                    genericArgs[1].UnderlyingSystemType == typeof(JsonElement) ||
                    genericArgs[1].UnderlyingSystemType == typeof(Nodes.JsonNode));
#endif
 
                Func<object>? createObjectForExtensionDataProp = jsonPropertyInfo.JsonTypeInfo.CreateObject
                    ?? jsonPropertyInfo.JsonTypeInfo.CreateObjectForExtensionDataProperty;
 
                if (createObjectForExtensionDataProp == null)
                {
                    // Avoid a reference to the JsonNode type for trimming
                    if (jsonPropertyInfo.PropertyType.FullName == JsonTypeInfo.JsonObjectTypeName)
                    {
                        ThrowHelper.ThrowInvalidOperationException_NodeJsonObjectCustomConverterNotAllowedOnExtensionProperty();
                    }
                    // For IReadOnlyDictionary<string, object> or IReadOnlyDictionary<string, JsonElement> interface types,
                    // create a Dictionary<TKey, TValue> instance seeded with any existing contents.
                    else if (jsonPropertyInfo.PropertyType == typeof(IReadOnlyDictionary<string, object>))
                    {
                        if (extensionData != null)
                        {
                            var existing = (IReadOnlyDictionary<string, object>)extensionData;
                            var newDict = new Dictionary<string, object>();
                            foreach (KeyValuePair<string, object> kvp in existing)
                            {
                                newDict[kvp.Key] = kvp.Value;
                            }
                            extensionData = newDict;
                        }
                        else
                        {
                            extensionData = new Dictionary<string, object>();
                        }
                        Debug.Assert(jsonPropertyInfo.Set != null);
                        jsonPropertyInfo.Set(obj, extensionData);
                        return;
                    }
                    else if (jsonPropertyInfo.PropertyType == typeof(IReadOnlyDictionary<string, JsonElement>))
                    {
                        if (extensionData != null)
                        {
                            var existing = (IReadOnlyDictionary<string, JsonElement>)extensionData;
                            var newDict = new Dictionary<string, JsonElement>();
                            foreach (KeyValuePair<string, JsonElement> kvp in existing)
                            {
                                newDict[kvp.Key] = kvp.Value;
                            }
                            extensionData = newDict;
                        }
                        else
                        {
                            extensionData = new Dictionary<string, JsonElement>();
                        }
                        Debug.Assert(jsonPropertyInfo.Set != null);
                        jsonPropertyInfo.Set(obj, extensionData);
                        return;
                    }
                    else
                    {
                        ThrowHelper.ThrowNotSupportedException_SerializationNotSupported(jsonPropertyInfo.PropertyType);
                    }
                }
 
                extensionData = createObjectForExtensionDataProp();
                Debug.Assert(jsonPropertyInfo.Set != null);
                jsonPropertyInfo.Set(obj, extensionData);
            }
 
            // We don't add the value to the dictionary here because we need to support the read-ahead functionality for Streams.
        }
    }
}