/*
 *
 * (c) Copyright Ascensio System Limited 2010-2018
 *
 * This program is freeware. You can redistribute it and/or modify it under the terms of the GNU 
 * General Public License (GPL) version 3 as published by the Free Software Foundation (https://www.gnu.org/copyleft/gpl.html). 
 * In accordance with Section 7(a) of the GNU GPL its Section 15 shall be amended to the effect that 
 * Ascensio System SIA expressly excludes the warranty of non-infringement of any third-party rights.
 *
 * THIS PROGRAM IS DISTRIBUTED WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE. For more details, see GNU GPL at https://www.gnu.org/copyleft/gpl.html
 *
 * You can contact Ascensio System SIA by email at sales@onlyoffice.com
 *
 * The interactive user interfaces in modified source and object code versions of ONLYOFFICE must display 
 * Appropriate Legal Notices, as required under Section 5 of the GNU GPL version 3.
 *
 * Pursuant to Section 7 § 3(b) of the GNU GPL you must retain the original ONLYOFFICE logo which contains 
 * relevant author attributions when distributing the software. If the display of the logo in its graphic 
 * form is not reasonably feasible for technical reasons, you must include the words "Powered by ONLYOFFICE" 
 * in every copy of the program you distribute. 
 * Pursuant to Section 7 § 3(e) we decline to grant you any rights under trademark law for use of our trademarks.
 *
*/


using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

using ASC.Common;
using ASC.Common.Logging;

using Microsoft.Extensions.Options;

using Newtonsoft.Json;

namespace ASC.Core.Common.Billing
{
    [Singletone]
    public class CouponManager
    {
        private IEnumerable<AvangateProduct> Products { get; set; }
        private IEnumerable<string> Groups { get; set; }
        private readonly int Percent;
        private readonly int Schedule;
        private readonly string VendorCode;
        private readonly byte[] Secret;
        private readonly Uri BaseAddress;
        private readonly string ApiVersion;
        private readonly SemaphoreSlim SemaphoreSlim = new SemaphoreSlim(1, 1);
        private readonly ILog Log;

        public CouponManager(IOptionsMonitor<ILog> option)
        {
            SemaphoreSlim = new SemaphoreSlim(1, 1);
            Log = option.CurrentValue;

            try
            {
                var cfg = (AvangateCfgSectionHandler)ConfigurationManager.GetSection("avangate");
                Secret = Encoding.UTF8.GetBytes(cfg.Secret);
                VendorCode = cfg.Vendor;
                Percent = cfg.Percent;
                Schedule = cfg.Schedule;
                BaseAddress = new Uri(cfg.BaseAddress);
                ApiVersion = "/rest/" + cfg.ApiVersion.TrimStart('/');
                Groups = (cfg.Groups ?? "").Split(',', '|', ' ');
            }
            catch (Exception e)
            {
                Secret = Encoding.UTF8.GetBytes("");
                VendorCode = "";
                Percent = AvangateCfgSectionHandler.DefaultPercent;
                Schedule = AvangateCfgSectionHandler.DefaultShedule;
                BaseAddress = new Uri(AvangateCfgSectionHandler.DefaultAdress);
                ApiVersion = AvangateCfgSectionHandler.DefaultApiVersion;
                Groups = new List<string>();
                Log.Fatal(e);
            }
        }

        public string CreateCoupon(TenantManager tenantManager)
        {
            return CreatePromotionAsync(tenantManager).Result;
        }

        private async Task<string> CreatePromotionAsync(TenantManager tenantManager)
        {
            try
            {
                using var httpClient = PrepaireClient();
                using var content = new StringContent(await Promotion.GeneratePromotion(Log, this, tenantManager, Percent, Schedule), Encoding.Default, "application/json");
                using var response = await httpClient.PostAsync(string.Format("{0}/promotions/", ApiVersion), content);
                if (!response.IsSuccessStatusCode)
                    throw new Exception(response.ReasonPhrase);

                var result = await response.Content.ReadAsStringAsync();
                await Task.Delay(1000 - DateTime.UtcNow.Millisecond); // otherwise authorize exception
                var createdPromotion = JsonConvert.DeserializeObject<Promotion>(result);
                return createdPromotion.Coupon.Code;
            }
            catch (Exception ex)
            {
                Log.Error(ex.Message, ex);
                throw;
            }
        }

        internal async Task<IEnumerable<AvangateProduct>> GetProducts()
        {
            if (Products != null) return Products;

            await SemaphoreSlim.WaitAsync();

            if (Products != null)
            {
                SemaphoreSlim.Release();
                return Products;
            }

            try
            {
                using var httpClient = PrepaireClient();
                using var response = await httpClient.GetAsync(string.Format("{0}/products/?Limit=1000&Enabled=true", ApiVersion));
                if (!response.IsSuccessStatusCode)
                    throw new Exception(response.ReasonPhrase);

                var result = await response.Content.ReadAsStringAsync();
                Log.Debug(result);

                var products = JsonConvert.DeserializeObject<List<AvangateProduct>>(result);
                products = products.Where(r => r.ProductGroup != null && Groups.Contains(r.ProductGroup.Code)).ToList();
                return Products = products;
            }
            catch (Exception ex)
            {
                Log.Error(ex.Message, ex);
                throw;
            }
            finally
            {
                SemaphoreSlim.Release();
            }
        }

        private HttpClient PrepaireClient()
        {
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
            const string applicationJson = "application/json";
            using var httpClient = new HttpClient { BaseAddress = BaseAddress, Timeout = TimeSpan.FromMinutes(3) };
            httpClient.DefaultRequestHeaders.TryAddWithoutValidation("accept", applicationJson);
            httpClient.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", applicationJson);
            httpClient.DefaultRequestHeaders.TryAddWithoutValidation("X-Avangate-Authentication", CreateAuthHeader());
            return httpClient;
        }

        private string CreateAuthHeader()
        {
            using var hmac = new HMACMD5(Secret);
            var date = DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss");
            var hash = VendorCode.Length + VendorCode + date.Length + date;
            var data = hmac.ComputeHash(Encoding.UTF8.GetBytes(hash));

            var sBuilder = new StringBuilder();
            foreach (var t in data)
            {
                sBuilder.Append(t.ToString("x2"));
            }

            var stringBuilder = new StringBuilder();
            stringBuilder.AppendFormat("code='{0}' ", VendorCode);
            stringBuilder.AppendFormat("date='{0}' ", date);
            stringBuilder.AppendFormat("hash='{0}'", sBuilder);
            return stringBuilder.ToString();
        }
    }

    class Promotion
    {
        public string Code { get; set; }
        public string Name { get; set; }
        public string Type { get; set; }
        public string StartDate { get; set; }
        public string EndDate { get; set; }
        public bool Enabled { get; set; }
        public int MaximumOrdersNumber { get; set; }
        public bool InstantDiscount { get; set; }
        public string ChannelType { get; set; }
        public string ApplyRecurring { get; set; }
        public Coupon Coupon { get; set; }
        public Discount Discount { get; set; }
        public IEnumerable<CouponProduct> Products { get; set; }
        public int PublishToAffiliatesNetwork { get; set; }
        public int AutoApply { get; set; }

        public static async Task<string> GeneratePromotion(ILog log, CouponManager couponManager, TenantManager tenantManager, int percent, int schedule)
        {
            try
            {
                var tenant = tenantManager.GetCurrentTenant();
                var startDate = DateTime.UtcNow.Date;
                var endDate = startDate.AddDays(schedule);
                var code = tenant.TenantAlias;

                var promotion = new Promotion
                {
                    Type = "REGULAR",
                    Enabled = true,
                    MaximumOrdersNumber = 1,
                    InstantDiscount = false,
                    ChannelType = "ECOMMERCE",
                    ApplyRecurring = "NONE",
                    PublishToAffiliatesNetwork = 0,
                    AutoApply = 0,

                    StartDate = startDate.ToString("yyyy-MM-dd"),
                    EndDate = endDate.ToString("yyyy-MM-dd"),
                    Name = string.Format("{0} {1}% off", code, percent),
                    Coupon = new Coupon { Type = "SINGLE", Code = code },
                    Discount = new Discount { Type = "PERCENT", Value = percent },
                    Products = (await couponManager.GetProducts()).Select(r => new CouponProduct { Code = r.ProductCode })

                };

                return JsonConvert.SerializeObject(promotion);
            }
            catch (Exception ex)
            {
                log.Error(ex.Message, ex);
                throw;
            }
        }
    }

    class Coupon
    {
        public string Type { get; set; }
        public string Code { get; set; }
    }

    class Discount
    {
        public string Type { get; set; }
        public int Value { get; set; }
    }

    class AvangateProduct
    {
        public string ProductCode { get; set; }
        public string ProductName { get; set; }
        public AvangateProductGroup ProductGroup { get; set; }
    }

    class AvangateProductGroup
    {
        public string Name { get; set; }
        public string Code { get; set; }
    }

    class CouponProduct
    {
        public string Code { get; set; }
    }

    class AvangateCfgSectionHandler : ConfigurationSection
    {
        public const string DefaultAdress = "https://api.avangate.com/";
        public const string DefaultApiVersion = "4.0";
        public const int DefaultPercent = 5;
        public const int DefaultShedule = 10;

        [ConfigurationProperty("secret")]
        public string Secret
        {
            get { return (string)this["secret"]; }
        }

        [ConfigurationProperty("vendor")]
        public string Vendor
        {
            get { return (string)this["vendor"]; }
            set { this["vendor"] = value; }
        }

        [ConfigurationProperty("percent", DefaultValue = DefaultPercent)]
        public int Percent
        {
            get { return Convert.ToInt32(this["percent"]); }
            set { this["percent"] = value; }
        }

        [ConfigurationProperty("schedule", DefaultValue = DefaultShedule)]
        public int Schedule
        {
            get { return Convert.ToInt32(this["schedule"]); }
            set { this["schedule"] = value; }
        }

        [ConfigurationProperty("groups")]
        public string Groups
        {
            get { return (string)this["groups"]; }
        }

        [ConfigurationProperty("address", DefaultValue = DefaultAdress)]
        public string BaseAddress
        {
            get { return (string)this["address"]; }
            set { this["address"] = value; }
        }

        [ConfigurationProperty("apiVersion", DefaultValue = DefaultApiVersion)]
        public string ApiVersion
        {
            get { return (string)this["apiVersion"]; }
            set { this["apiVersion"] = value; }
        }
    }
}