using BinaryDad.Extensions;
using Newtonsoft.Json;
using Salesforce.NET.Entities;
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using Newtonsoft.Json.Converters;
using System.Net;

namespace Salesforce.NET
{
    public class SalesforceApiClient
    {
        private const string ContextKey = "SalesforceApiContext";

        private readonly Task initializationTask;
        private readonly string batchProcessingConnectionString;

        const string apiVersion = "51.0";

        private SalesforceContext SalesforceContext
        {
            get => CacheHelper.Get<SalesforceContext>(ContextKey);
            set => CacheHelper.Add(ContextKey, value, 1440);
        }

        public SalesforceApiClient(SalesforceCredentials credentials)
        {
            if (SalesforceContext == null)
            {
                // authenticate from constructor, but task is awaited prior to invoking request
                initializationTask = AuthenticateAsync(credentials);
            }
        }

        /// <summary>
        /// Retrieves a single Salesforce record by ID
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="id"></param>
        /// <returns></returns>
        public async Task<T> GetAsync<T>(string id) where T : SalesforceEntity
        {
            var salesforceObject = GetObjectName<T>();

            var getApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}/{id}");

            return await InvokeRequestAsync(async httpClient =>
            {
                var response = await httpClient.GetAsync(getApiUrl);

                return await response.Content.ReadAsAsync<T>();
            });
        }

        /// <summary>
        /// Retrieves a single Salesforce record matching on an external ID
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="externalIdProperty">The property representing of the external ID to lookup</param>
        /// <param name="id"></param>
        /// <returns></returns>
        public async Task<T> GetAsync<T>(Expression<Func<T, object>> externalIdProperty, string id) where T : SalesforceEntity
        {
            var salesforceObject = GetObjectName<T>();

            if (externalIdProperty.Body is MemberExpression memberExpression)
            {
                var jsonProperty = memberExpression.Member.GetCustomAttribute<JsonPropertyAttribute>();

                var propertyName = jsonProperty?.PropertyName ?? memberExpression.Member.Name;

                var getApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}/{propertyName}/{id}");

                return await InvokeRequestAsync(async httpClient =>
                {
                    var response = await httpClient.GetAsync(getApiUrl);

                    return await response.Content.ReadAsAsync<T>();
                });
            }

            throw new ArgumentException("External ID must be a property expression", nameof(externalIdProperty));
        }

        /// <summary>
        /// Creates a new Salesforce record
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="record"></param>
        /// <returns></returns>
        public async Task<Result<string>> CreateAsync<T>(T record) where T : SalesforceEntity
        {
            var result = new Result<string>();

            var salesforceObject = GetObjectName<T>();

            var createApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}");

            return await InvokeRequestAsync(async httpClient =>
            {
                record.SerializeReadOnlyProperties = false;

                var response = await httpClient.PostAsJsonAsync(createApiUrl, record);

                var createResponse = await response.Content.ReadAsAsync<CreateResponse>();

                if (createResponse.Success)
                {
                    record.RecordId = createResponse.RecordId;

                    result.Data = createResponse.RecordId;
                    result.Success = true;
                }
                else
                {
                    // TODO: parse error response
                    result.AddError($"Error creating record");
                }

                return result;
            });
        }

        /// <summary>
        /// Creates a set of new Salesforce records
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="records"></param>
        /// <returns></returns>
        public async Task<Result> CreateAsync<T>(IEnumerable<T> records) where T : SalesforceEntity
        {
            var result = new Result();

            var salesforceObject = GetObjectName<T>();

            var createApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}");

            return await InvokeRequestAsync(async httpClient =>
            {
                var messages = new List<string>();

                // default to true until any fail in loop
                result.Success = true;

                foreach (var record in records)
                {
                    record.SerializeReadOnlyProperties = false;

                    var response = await httpClient.PostAsJsonAsync(createApiUrl, record);

                    var responseBody = await response.Content.ReadAsStringAsync();

                    if (response.IsSuccessStatusCode)
                    {
                        var createResponse = responseBody.Deserialize<CreateResponse>();

                        if (createResponse.Success)
                        {
                            record.RecordId = createResponse.RecordId;

                            messages.Add($"Created record with ID {record.RecordId}");
                        }
                        else
                        {
                            // TODO: follow pattern of batch lead create, consolidate response inti Result<T>
                            result.AddError($"Error creating record");
                        }
                    }
                    else
                    {
                        var errorResponse = responseBody.Deserialize<ErrorCollectionResponse>();

                        var errorMessages = errorResponse
                            .Select(e => $"[{e.ErrorCode}] {e.Message}")
                            .ToList();

                        result.AddErrors(errorMessages);
                    }
                }

                if (messages.Any())
                {
                    result.Message = messages.Join("; ");
                }

                return result;
            });
        }

        /// <summary>
        /// Creates a set of new Salesforce records (TO POSSIBLY REPLACE CreateAsync(IEnumerable<T>))
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="records"></param>
        /// <returns></returns>
        public async Task<object> CreateBulkAsync<T>(IEnumerable<T> records) where T : SalesforceEntity
        {
            var salesforceObject = GetObjectName<T>();

            #region Create batch job

            var jobCreateResponse = await InvokeRequestAsync(async httpClient =>
            {
                var createApiUrl = await GetEndpointUrlAsync("jobs/ingest");

                var response = await httpClient.PostAsJsonAsync(createApiUrl, new
                {
                    @object = salesforceObject,
                    contentType = "CSV",
                    operation = "insert",
                    lineEnding = "CRLF"
                });

                return await response.Content.ReadAsAsync<JobCreateResponse>();
            });

            #endregion

            #region Upload content

            var uploadResponse = await InvokeRequestAsync(async httpClient =>
            {
                var insertApiUrl = UrlUtility.Combine(SalesforceContext.InstanceUrl, jobCreateResponse.ContentUrl);

                var recordsTable = records.ToDataTable(info => info.GetCustomAttribute<JsonPropertyAttribute>()?.PropertyName);

                var recordsCsv = recordsTable.ToCsv();

                var recordsEncoded = recordsCsv.Base64Encode();

                var csvContent = new StringContent(recordsEncoded);

                csvContent.Headers.ContentType = new MediaTypeHeaderValue("text/csv");

                httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

                var response = await httpClient.PutAsync(insertApiUrl, csvContent);

                return await response.Content.ReadAsStringAsync();
            });

            #endregion

            #region Close job

            var closeResponse = await InvokeRequestAsync(async httpClient =>
            {
                var closeApiUrl = await GetEndpointUrlAsync($"jobs/ingest/{jobCreateResponse.Id}");

                var method = new HttpMethod("PATCH");

                var body = new
                {
                    state = "UploadComplete"
                };

                var content = new StringContent(body.Serialize(), Encoding.UTF8, "application/json");

                var message = new HttpRequestMessage(method, closeApiUrl)
                {
                    Content = content
                };

                var response = await httpClient.SendAsync(message);

                return await response.Content.ReadAsStringAsync();
            });

            #endregion

            #region Get Status

            var statusResponse = await InvokeRequestAsync(async httpClient =>
            {
                var statusApiUrl = await GetEndpointUrlAsync($"jobs/ingest/{jobCreateResponse.Id}");

                var response = await httpClient.GetAsync(statusApiUrl);

                return await response.Content.ReadAsStringAsync();
            });

            #endregion

            #region Download results

            var downloadResponse = await InvokeRequestAsync(async httpClient =>
            {
                var downloadApiUrl = await GetEndpointUrlAsync($"jobs/ingest/{jobCreateResponse.Id}/failedResults");

                httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/csv"));

                var response = await httpClient.GetAsync(downloadApiUrl);

                return await response.Content.ReadAsStringAsync();
            });

            #endregion

            return null;
        }

        public Task<UpdateResponse> UpdateAsync<T>(string id, Action<T> update) where T : SalesforceEntity, new()
        {
            var record = new T()
            {
                RecordId = id
            };

            var trackable = record.AsTrackable();

            update(record);

            return UpdateAsync(trackable);
        }

        public async Task<UpdateResponse> UpdateAsync<T>(Trackable<T> record) where T : SalesforceEntity
        {
            if (record.Value.RecordId.IsNullOrWhiteSpace())
            {
                throw new ArgumentException("Record ID cannot be null or empty", nameof(record.Value.RecordId));
            }

            var salesforceObject = GetObjectName<T>();

            var createApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}/{record.Value.RecordId}");

            return await InvokeRequestAsync(async httpClient =>
            {
                var method = new HttpMethod("PATCH");

                var body = JsonConvert.SerializeObject(record.Modified, new StringEnumConverter());

                var content = new StringContent(body, Encoding.UTF8, "application/json");

                var message = new HttpRequestMessage(method, createApiUrl)
                {
                    Content = content
                };

                var response = await httpClient.SendAsync(message);

                if (response.IsSuccessStatusCode)
                {
                    return new UpdateResponse(true);
                }

                return await response.Content.ReadAsAsync<UpdateResponse>();
            });
        }

        /// <summary>
        /// Retrieves Salesforce records using an object query expression
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="query"></param>
        /// <returns></returns>
        public async Task<ICollection<T>> QueryAsync<T>(Expression<Func<T, bool>> query) where T : SalesforceEntity
        {
            var salesforceObject = GetObjectName<T>();

            // build a list of properties used in the "select" portion of the query
            var properties = typeof(T)
                .GetProperties()
                .WhereIsQueryable()
                .WhereIsSerializable()
                .Select(p =>
                {
                    var jsonProperty = p.GetCustomAttribute<JsonPropertyAttribute>();

                    return jsonProperty?.PropertyName ?? p.Name;
                })
                .WhereNotNull()
                .Join(", ");

            // generate a SQL clause from the query expression
            var clause = ConvertExpression(query.Body);

            var queryApiUrl = await GetEndpointUrlAsync($"query?q=select {properties} from {salesforceObject} where {clause}");

            return await InvokeRequestAsync(async httpClient =>
            {
                var response = await httpClient.GetAsync(queryApiUrl);

                var queryResponse = await response.Content.ReadAsAsync<QueryResponse<T>>();

                var records = queryResponse.Records;

                // TODO: incorporate limit
                while (!queryResponse.Done)
                {
                    var absoluteNextRecordsUrl = UrlUtility.Combine(SalesforceContext.InstanceUrl, queryResponse.NextRecordsUrl);

                    response = await httpClient.GetAsync(absoluteNextRecordsUrl);

                    queryResponse = await response.Content.ReadAsAsync<QueryResponse<T>>();

                    records.AddRange(queryResponse.Records);
                }

                return records;
            });
        }

        /// <summary>
        /// Retrieves schema information for an entity
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public async Task<SchemaResponse> GetSchema<T>() where T : SalesforceEntity
        {
            var salesforceObject = GetObjectName<T>();

            var schemaApiUrl = await GetEndpointUrlAsync($"sobjects/{salesforceObject}/describe");

            return await InvokeRequestAsync(async httpClient =>
            {
                var response = await httpClient.GetAsync(schemaApiUrl);

                var responseBody = await response.Content.ReadAsStringAsync();

                return await response.Content.ReadAsAsync<SchemaResponse>();
            });
        }

        /// <summary>
        /// Validates whether the entity is properly mapped to its schema in Salesforce
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public async Task<Result<bool>> ValidateSchema<T>() where T : SalesforceEntity, new()
        {
            var result = new Result<bool>();
            var schema = await GetSchema<T>();

            // get the fields from Salesforce
            var salesforceFields = schema.Fields
                .Select(f => f.Name)
                .ToList();

            // get the fields for the entity
            var propertyNames = typeof(T)
                .GetProperties()
                .WhereIsSerializable()
                .WhereIsQueryable()
                .GetPropertyNames();

            // find any orphaned/mismatched fields
            var mismatchedFields = propertyNames
                .Where(p => !salesforceFields.Contains(p, StringComparer.OrdinalIgnoreCase))
                .ToList();

            result.Success = mismatchedFields.NoneOrNull();

            if (result.Success)
            {
                result.Message = "All fields are valid";
            }
            else
            {
                foreach (var mismatchedField in mismatchedFields)
                {
                    result.AddError($"Field [{mismatchedField}] was not found in source");
                }
            }

            return result;
        }

        #region Private Methods

        private async Task AuthenticateAsync(SalesforceCredentials credentials)
        {
            var baseApiUrl = credentials.IsProduction ? "https://login.salesforce.com/services" : "https://test.salesforce.com/services";

            var authenticationUrl = UrlUtility.Combine(baseApiUrl, "oauth2/token");

            var httpClient = new HttpClient();

            var authenticationRequest = new Dictionary<string, string>
            {
                ["grant_type"] = "password",
                ["client_id"] = credentials.ClientId,
                ["client_secret"] = credentials.ClientSecret,
                ["username"] = credentials.Username,
                ["password"] = WebUtility.UrlEncode(credentials.Password) + credentials.SecurityToken
            };

            // don't use ToQueryString() as it encodes the values
            var requestBody = authenticationRequest
                .Select(k => $"{k.Key}={k.Value}")
                .Join("&");

            var requestContent = new StringContent(requestBody, Encoding.UTF8, "application/x-www-form-urlencoded");

            var response = await httpClient.PostAsync(authenticationUrl, requestContent);

            var authenticationResponse = await response.Content.ReadAsAsync<AuthenticationResponse>();

            if (authenticationResponse.Success)
            {
                SalesforceContext = new SalesforceContext(authenticationResponse.AccessToken, authenticationResponse.InstanceUrl, authenticationResponse.TokenType);
            }
        }

        private async Task<T> InvokeRequestAsync<T>(Func<HttpClient, Task<T>> action)
        {
            await AssertInitializedAsync();

            var httpClient = new HttpClient();

            httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(SalesforceContext.TokenType.ToString(), SalesforceContext.AccessToken);

            return await action(httpClient);
        }

        private async Task<string> GetEndpointUrlAsync(string relativeApiUrl)
        {
            await AssertInitializedAsync();

            return UrlUtility.Combine(SalesforceContext.InstanceUrl, $"services/data/v{apiVersion}/{relativeApiUrl}");
        }

        private string GetObjectName<T>()
        {
            var type = typeof(T);
            var objectAttribute = type.GetCustomAttribute<SalesforceObjectAttribute>();

            return objectAttribute?.ObjectName ?? type.Name;
        }

        /// <summary>
        /// Converts an expression tree into a SQL query clause
        /// </summary>
        /// <param name="expression"></param>
        /// <returns></returns>
        private static string ConvertExpression(Expression expression)
        {
            /* NOTE: this is a work in progress, as I did not like the built-in
             * Expression.ToString(), and this allows us to customize the query to our liking */

            if (expression is BinaryExpression binaryExpression)
            {
                // traverse the tree and combine all sub expression groups
                var left = ConvertExpression(binaryExpression.Left);
                var comparison = GetExpressionType(binaryExpression.NodeType);
                var right = ConvertExpression(binaryExpression.Right);

                return $"({left} {comparison} {right})";
            }

            if (expression is ConstantExpression || expression is MethodCallExpression)
            {
                return GetExpressionValue(expression);
            }

            if (expression is MemberExpression memberExpression)
            {
                if (memberExpression.Expression is ParameterExpression)
                {
                    // NOTE: this should be be the property from the delegate's parameter

                    var jsonProperty = memberExpression.Member.GetCustomAttribute<JsonPropertyAttribute>();

                    return jsonProperty != null ? jsonProperty.PropertyName : memberExpression.Member.Name;
                }

                return GetExpressionValue(expression);
            }

            return string.Empty;
        }

        private static string GetExpressionValue(Expression expression)
        {
            var value = Expression.Lambda(expression).Compile().DynamicInvoke();

            if (expression.Type == typeof(string))
            {
                // TODO: escaping single quotes?
                return $"'{value}'";
            }

            if (expression.Type == typeof(DateTime))
            {
                return ((DateTime)value).ToString("yyyy-MM-ddThh:mm:ssZ");
            }

            if (value == null)
            {
                return string.Empty;
            }

            return value.ToString();
        }

        private static string GetExpressionType(ExpressionType expressionType)
        {
            return expressionType == ExpressionType.Equal ? "="
                : expressionType == ExpressionType.NotEqual ? "!="
                : expressionType == ExpressionType.GreaterThan ? ">"
                : expressionType == ExpressionType.GreaterThanOrEqual ? ">="
                : expressionType == ExpressionType.LessThan ? "<"
                : expressionType == ExpressionType.LessThanOrEqual ? "<="
                : expressionType == ExpressionType.AndAlso ? "and"
                : expressionType == ExpressionType.And ? "and"
                : expressionType == ExpressionType.Or ? "or"
                : expressionType == ExpressionType.OrElse ? "or"
                : "";
        }

        private async Task AssertInitializedAsync()
        {
            if (SalesforceContext == null && initializationTask != null)
            {
                await initializationTask;
            }
        }

        #endregion
    }
}