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Improve filenames for downloaded assets. Fixes #1231

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Lymia Kanokawa 2024-05-12 20:02:58 -07:00
parent 0fb4bea64d
commit 7be46d6de5
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GPG key ID: 9314D8F6745E881E
1 changed files with 84 additions and 19 deletions
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103
DiscordChatExporter.Core/Exporting/ExportAssetDownloader.cs
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@ -2,6 +2,7 @@
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
@ -92,34 +93,46 @@ internal partial class ExportAssetDownloader(string workingDirPath, bool reuse)
internal partial class ExportAssetDownloader
{
private static string GetUrlHash(string url)
private const String CHARSET = "0123456789bcdfghjklmnpqrstvwxyz_";
private static String Base32(byte[] data)
{
// Remove signature parameters from Discord CDN URLs to normalize them
static string NormalizeUrl(string url)
var newString = new StringBuilder();
uint accum = 0;
uint bits = 0;
foreach (byte b in data)
{
var uri = new Uri(url);
if (!string.Equals(uri.Host, "cdn.discordapp.com", StringComparison.OrdinalIgnoreCase))
return url;
accum <<= 8;
accum |= b;
bits += 8;
var query = HttpUtility.ParseQueryString(uri.Query);
query.Remove("ex");
query.Remove("is");
query.Remove("hm");
return uri.GetLeftPart(UriPartial.Path) + query;
while (bits > 5)
{
char ch = CHARSET[(int)(accum & 0x1F)];
accum >>= 5;
bits -= 5;
newString.Append(ch);
}
}
if (bits != 0)
{
char ch = CHARSET[(int)(accum & 0x1F)];
newString.Append(ch);
}
return SHA256
.HashData(Encoding.UTF8.GetBytes(NormalizeUrl(url)))
.ToHex()
// 5 chars ought to be enough for anybody
.Truncate(5);
return newString.ToString();
}
private static string GetFileNameFromUrl(string url)
private static string GetUrlHash(string url)
{
var urlHash = GetUrlHash(url);
var hash = SHA256.HashData(Encoding.UTF8.GetBytes(url));
// 12 characters of base32 contains about as much entropy as a Discord snowflake
return Base32(hash).Truncate(12);
}
private static string AddHashToUrl(string url, string urlHash)
{
// Try to extract the file name from URL
var fileName = Regex.Match(url, @".+/([^?]*)").Groups[1].Value;
@ -143,4 +156,56 @@ internal partial class ExportAssetDownloader
fileNameWithoutExtension.Truncate(42) + '-' + urlHash + fileExtension
);
}
private static string GetFileNameFromUrl(string url)
{
var uri = new Uri(url);
if (string.Equals(uri.Host, "cdn.discordapp.com"))
{
string[] split = uri.AbsolutePath.Split("/");
// Attachments
if (uri.AbsolutePath.StartsWith("/attachments/") && split.Length == 5)
{
// use the attachment snowflake for attachments
if (ulong.TryParse(split[3], out var snowflake))
return AddHashToUrl(url, snowflake.ToString());
}
// Emojis
if (
uri.AbsolutePath.StartsWith("/emojis/")
&& split.Length == 3
&& split[2].Contains(".")
)
{
var nameSplit = split[2].Split(".", 2);
if (ulong.TryParse(nameSplit[0], out var snowflake))
return $"emoji-discord-{snowflake}.{nameSplit[1]}";
}
// Avatars
if (uri.AbsolutePath.StartsWith("/avatars/") && split.Length == 4)
{
return $"avatar-{split[2]}-{GetUrlHash(url)}.{split[3].Split(".").Last()}";
}
}
if (string.Equals(uri.Host, "cdn.jsdelivr.net"))
{
string[] split = uri.AbsolutePath.Split("/");
// twemoji
if (
uri.AbsolutePath.StartsWith("/gh/twitter/twemoji@latest/assets/svg/")
&& split.Length == 7
)
{
return $"emoji-twemoji-{split[6]}";
}
}
return AddHashToUrl(url, GetUrlHash(url));
}
}