[CHANGE] Implementing video fetching and deciphering

Manager.YouTube/Parsers/HtmlParser.cs

@@ -1,5 +1,7 @@
+using System.Text.Json.Nodes;
 using DotBased.Monads;
 using HtmlAgilityPack;
+using Manager.YouTube.Models.Parser;
 
 namespace Manager.YouTube.Parsers;
 
@@ -31,7 +33,57 @@ public static class HtmlParser
 
         return (json, isPremiumUser);
     }
-    
+
+    public static Result<YouTubeVideoData> GetVideoDataFromHtml(string html)
+    {
+        if (string.IsNullOrWhiteSpace(html))
+        {
+            return ResultError.Fail("html cannot be empty!");
+        }
+        var htmlDocument = new HtmlDocument();
+        htmlDocument.LoadHtml(html);
+
+        const string initialYoutubeData = "var ytInitialPlayerResponse = {";
+        var initialPlayerDataNode = htmlDocument.DocumentNode.SelectSingleNode($"//script[contains(., '{initialYoutubeData}')]");
+        if (string.IsNullOrWhiteSpace(initialPlayerDataNode.InnerText))
+        {
+            return ResultError.Fail("Could not find {initialPlayerData} in html script nodes!");
+        }
+        var initialPlayerDataString = ExtractJson(initialPlayerDataNode.InnerText, "var ytInitialPlayerResponse = ");
+        if (string.IsNullOrWhiteSpace(initialPlayerDataString))
+        {
+            return ResultError.Fail("Failed to extract initial player date from JSON.");
+        }
+        var parsedPlayerInitialData = JsonNode.Parse(initialPlayerDataString);
+        
+        const string initialData = "var ytInitialData = {";
+        var initialDataNode = htmlDocument.DocumentNode.SelectSingleNode($"//script[contains(., '{initialData}')]");
+        if (string.IsNullOrWhiteSpace(initialDataNode.InnerText))
+        {
+            return ResultError.Fail("Could not find {initialData} in html script nodes!");
+        }
+        
+        var initialDataJsonString = ExtractJson(initialDataNode.InnerText, "var ytInitialData = ");
+        if (string.IsNullOrWhiteSpace(initialDataJsonString))
+        {
+            return ResultError.Fail("Failed to extract initial player date from JSON.");
+        }
+        var parsedInitialData = JsonNode.Parse(initialDataJsonString);
+
+        try
+        {
+            return new YouTubeVideoData
+            {
+                YouTubePlayerData = parsedPlayerInitialData?.AsObject(),
+                YouTubeInitialData = parsedInitialData?.AsObject()
+            };
+        }
+        catch (Exception e)
+        {
+            return ResultError.Error(e, "Could not parse youtube player data.");
+        }
+    }
+
     static string? ExtractJson(string input, string marker)
     {
         var start = input.IndexOf(marker, StringComparison.Ordinal);