update:优化二维码长度

QRCodeService/Services/IShortCodeService.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace QRCodeService.Services
+{
+    public interface IShortCodeService
+    {
+        Task<string> GenShortCode(string url);
+    }
+}

QRCodeService/Services/ShortCodeService.cs

@@ -0,0 +1,76 @@
+using Base62;
+using Domain.AggregateModel.LinkAggregate;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace QRCodeService.Services
+{
+    public class ShortCodeService : IShortCodeService
+    {
+        private readonly ILinkRepository linkRepository;
+
+        public ShortCodeService(ILinkRepository linkRepository)
+        {
+            this.linkRepository = linkRepository;
+        }
+
+        public async Task<string> GenShortCode(string url)
+        {
+            var full = 16;
+            var length = 4;
+            var idx = 0;
+
+            while (true)
+            {
+                var code = CalculateShortCode(url, length, idx);
+                var link = await linkRepository.GetAsync(code);
+                if (link == null || link.FullUrl == url)
+                {
+                    return code;
+                }
+                idx++;
+                if (idx * length == full)
+                {
+                    idx = 0;
+                    length = 2 * length;
+                }
+            }
+            
+        }
+        /// <summary>
+        /// 计算短链接
+        /// </summary>
+        /// <param name="url"></param>
+        /// <param name="length">4(四分之一) 8(半) 16(全长)</param>
+        /// <param name="index"></param>
+        /// <returns></returns>
+        private string CalculateShortCode(string url,int length,int index)
+        {
+            using (var md5 = MD5.Create())
+            {
+                var result = md5.ComputeHash(Encoding.UTF8.GetBytes(url));
+                if (length == 4)
+                {
+                    return BitConverter.ToInt32(result, 4 * index).ToBase62();
+                }
+                if(length == 8)
+                {
+                    return BitConverter.ToInt32(result, 8 * index).ToBase62();
+                }
+                if(length == 16)
+                {
+                    return BitConverter.ToInt64(result, 0).ToBase62() + BitConverter.ToInt64(result, 8).ToBase62();
+                }
+                if(length > 16)
+                {
+                    return BitConverter.ToInt64(result, 0).ToBase62() + BitConverter.ToInt64(result, 8).ToBase62() + length.ToBase62();
+                }
+                throw (new ArgumentOutOfRangeException());
+            }
+        }
+    }
+}