1 files changed, 32 insertions, 0 deletions
diff --git a/browser/background.js b/browser/background.js
new file mode 100644
index 0000000..7fc4a82
--- /dev/null
+++ b/browser/background.js
@@ -0,0 +1,32 @@
+/**
+ * @template T
+ * @param {T[]} arr
+ * @param {(v: T) => boolean} predicate
+ */
+function removeFirst(arr, predicate) {
+    const idx = arr.findIndex(predicate);
+    if (idx !== -1) arr.splice(idx, 1);
+}
+
+chrome.webRequest.onHeadersReceived.addListener(
+    ({ responseHeaders, type, url }) => {
+        if (!responseHeaders) return;
+
+        if (type === "main_frame") {
+            // In main frame requests, the CSP needs to be removed to enable fetching of custom css
+            // as desired by the user
+            removeFirst(responseHeaders, h => h.name.toLowerCase() === "content-security-policy");
+        } else if (type === "stylesheet" && url.startsWith("https://raw.githubusercontent.com")) {
+            // Most users will load css from GitHub, but GitHub doesn't set the correct content type,
+            // so we fix it here
+            removeFirst(responseHeaders, h => h.name.toLowerCase() === "content-type");
+            responseHeaders.push({
+                name: "Content-Type",
+                value: "text/css"
+            });
+        }
+        return { responseHeaders };
+    },
+    { urls: ["https://raw.githubusercontent.com/*", "*://*.discord.com/*"], types: ["main_frame", "stylesheet"] },
+    ["blocking", "responseHeaders"]
+);