From d6ea25a64ef1258d3a50f77ada90a7a6da596598 Mon Sep 17 00:00:00 2001
From: Kodi Craft <kodi@kdcf.me>
Date: Thu, 10 Oct 2024 17:55:43 +0200
Subject: [PATCH] Try implementing keeping old server jars

---
 apps/amethyst/lib/datagen.ex | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/apps/amethyst/lib/datagen.ex b/apps/amethyst/lib/datagen.ex
index b22342a..2452af9 100644
--- a/apps/amethyst/lib/datagen.ex
+++ b/apps/amethyst/lib/datagen.ex
@@ -43,19 +43,35 @@ defmodule Amethyst.DataGenerator do
     end
   end
 
-  @spec download_server_jar(:latest | String.t(), path) :: {:ok, path} | {:error, term} when path: String.t()
-  def download_server_jar(version, path) do
+  @spec get_server_jar(:latest | String.t(), path) :: {:ok, path} | {:error, term} when path: String.t()
+  def get_server_jar(version, path) do
     case get_version_meta(version) do
       {:ok, %{"downloads" => %{"server" => %{"url" => url, "sha1" => sha1}}}} ->
-        Logger.debug("Downloading server jar from #{url}, sha1: #{sha1}")
-        case Req.get(url, into: File.stream!(path)) do
-          {:ok, _} -> {:ok, path}
-          {:error, err} -> {:error, err}
+        # Check if the file already exists and has the right hash
+        Logger.debug("Checking if server jar exists at #{path} with hash #{sha1}")
+        case File.read(path) do
+          {:ok, data} ->
+            if :crypto.hash(:sha, data) == sha1 do
+              Logger.debug("Using cached server jar at #{path}")
+              {:ok, path}
+            else
+              Logger.debug("Mismatched hash, redownloading server jar")
+              download_jar(url, path)
+            end
+          {:error, _} -> download_jar(url, path)
         end
       {:error, err} -> {:error, err}
     end
   end
 
+  defp download_jar(url, path) do
+    Logger.debug("Downloading server jar from #{url}")
+    case Req.get(url, into: File.stream!(path)) do
+      {:ok, _} -> {:ok, path}
+      {:error, err} -> {:error, err}
+    end
+  end
+
   @spec get_latest_version() ::
           {:error, %{:__exception__ => true, :__struct__ => atom(), optional(atom()) => any()}}
           | {:ok, any()}