From 890fef4f276ec44312eb936583adbbf47d7cfe9d Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sat, 6 Mar 2021 22:51:53 +0800
Subject: feat: Auto translate url in markdown post.

---
 BackEnd/Timeline/Services/MarkdownProcessor.cs | 52 ++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 BackEnd/Timeline/Services/MarkdownProcessor.cs

(limited to 'BackEnd/Timeline/Services/MarkdownProcessor.cs')

diff --git a/BackEnd/Timeline/Services/MarkdownProcessor.cs b/BackEnd/Timeline/Services/MarkdownProcessor.cs
new file mode 100644
index 00000000..f34432cd
--- /dev/null
+++ b/BackEnd/Timeline/Services/MarkdownProcessor.cs
@@ -0,0 +1,52 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Markdig;
+using Markdig.Renderers.Normalize;
+using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+using Microsoft.AspNetCore.Mvc;
+using Timeline.Controllers;
+
+namespace Timeline.Services
+{
+    public class MarkdownProcessor
+    {
+        public string Process(string text, Func<long, string> urlGenerator)
+        {
+            MarkdownDocument markdown = Markdown.Parse(text);
+            foreach (var link in markdown.Descendants().Where(e => e is LinkInline).Cast<LinkInline>())
+            {
+                if (int.TryParse(link.Url, out var dataIndex))
+                {
+                    link.Url = urlGenerator(dataIndex);
+                }
+            }
+
+            var writer = new StringWriter();
+            NormalizeRenderer renderer = new NormalizeRenderer(writer);
+            renderer.Render(markdown);
+
+            return writer.ToString();
+        }
+
+        /// <summary>Convert data url to true url with post id.</summary>
+        public string Process(string text, IUrlHelper url, string timeline, long post)
+        {
+            return Process(
+                text,
+                dataIndex => url.ActionLink(
+                    nameof(TimelinePostController.DataGet),
+                    nameof(TimelinePostController)[0..^nameof(Controller).Length],
+                    new { timeline, post, data_index = dataIndex }
+                )
+            );
+        }
+
+        public byte[] Process(byte[] data, IUrlHelper url, string timeline, long post)
+        {
+            return Encoding.UTF8.GetBytes(Process(Encoding.UTF8.GetString(data), url, timeline, post));
+        }
+    }
+}
-- 
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