refactor: dedupe media and discord lowercase helpers

src/media/ffmpeg-exec.ts

@@ -1,6 +1,7 @@
 import { execFile, type ExecFileOptions } from "node:child_process";
 import { promisify } from "node:util";
 import { resolveSystemBin } from "../infra/resolve-system-bin.js";
+import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import {
   MEDIA_FFMPEG_MAX_BUFFER_BYTES,
   MEDIA_FFMPEG_TIMEOUT_MS,
@@ -60,9 +61,8 @@ export async function runFfmpeg(args: string[], options?: MediaExecOptions): Pro
 export function parseFfprobeCsvFields(stdout: string, maxFields: number): string[] {
   return stdout
     .trim()
-    .toLowerCase()
     .split(/[,\r\n]+/, maxFields)
-    .map((field) => field.trim());
+    .map((field) => normalizeLowercaseStringOrEmpty(field));
 }
 
 export function parseFfprobeCodecAndSampleRate(stdout: string): {

src/media/mime.ts

@@ -1,5 +1,8 @@
 import path from "node:path";
-import { normalizeOptionalLowercaseString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalLowercaseString,
+} from "../shared/string-coerce.js";
 import { type MediaKind, mediaKindFromMime } from "./constants.js";
 
 let fileTypeModulePromise: Promise<typeof import("file-type")> | undefined;
@@ -94,12 +97,12 @@ export function getFileExtension(filePath?: string | null): string | undefined {
   try {
     if (/^https?:\/\//i.test(filePath)) {
       const url = new URL(filePath);
-      return path.extname(url.pathname).toLowerCase() || undefined;
+      return normalizeLowercaseStringOrEmpty(path.extname(url.pathname)) || undefined;
     }
   } catch {
     // fall back to plain path parsing
   }
-  const ext = path.extname(filePath).toLowerCase();
+  const ext = normalizeLowercaseStringOrEmpty(path.extname(filePath));
   return ext || undefined;
 }
 
@@ -123,7 +126,7 @@ function isGenericMime(mime?: string): boolean {
   if (!mime) {
     return true;
   }
-  const m = mime.toLowerCase();
+  const m = normalizeLowercaseStringOrEmpty(mime);
   return m === "application/octet-stream" || m === "application/zip";
 }
 
@@ -171,7 +174,7 @@ export function isGifMedia(opts: {
   contentType?: string | null;
   fileName?: string | null;
 }): boolean {
-  if (opts.contentType?.toLowerCase() === "image/gif") {
+  if (normalizeOptionalLowercaseString(opts.contentType) === "image/gif") {
     return true;
   }
   const ext = getFileExtension(opts.fileName);
@@ -182,7 +185,7 @@ export function imageMimeFromFormat(format?: string | null): string | undefined
   if (!format) {
     return undefined;
   }
-  switch (format.toLowerCase()) {
+  switch (normalizeLowercaseStringOrEmpty(format)) {
     case "jpg":
     case "jpeg":
       return "image/jpeg";

src/media/web-media.ts

@@ -3,7 +3,10 @@ import { logVerbose, shouldLogVerbose } from "../globals.js";
 import { SafeOpenError, readLocalFileSafely } from "../infra/fs-safe.js";
 import { assertNoWindowsNetworkPath, safeFileURLToPath } from "../infra/local-file-access.js";
 import type { SsrFPolicy } from "../infra/net/ssrf.js";
-import { normalizeOptionalString } from "../shared/string-coerce.js";
+import {
+  normalizeLowercaseStringOrEmpty,
+  normalizeOptionalString,
+} from "../shared/string-coerce.js";
 import { resolveUserPath } from "../utils.js";
 import { maxBytesForKind, type MediaKind } from "./constants.js";
 import { fetchRemoteMedia } from "./fetch.js";
@@ -182,7 +185,9 @@ async function optimizeImageWithFallback(params: {
   meta?: { contentType?: string; fileName?: string };
 }): Promise<OptimizedImage> {
   const { buffer, cap, meta } = params;
-  const isPng = meta?.contentType === "image/png" || meta?.fileName?.toLowerCase().endsWith(".png");
+  const isPng =
+    meta?.contentType === "image/png" ||
+    normalizeLowercaseStringOrEmpty(meta?.fileName).endsWith(".png");
   const hasAlpha = isPng && (await hasAlphaChannel(buffer));
 
   if (hasAlpha) {