more refactoring , more unit tests...sigh

src/platform_ops.py

@@ -4,7 +4,10 @@ import shutil
 import subprocess
 import sys
 from pathlib import Path
-
+import hashlib
+import platform
+#from .config import APP_DATA_DIR, DOWNLOAD_TIMEOUT, ensure_dir
+from .app_log import log
 
 
 # Windows: %LOCALAPPDATA%\octo-updater\
@@ -143,4 +146,57 @@ def display_info() -> dict:
 
 
 
+# NOTE: Returns a path to an aria2c executable , otherwise returns none 
+def find_aria2c() -> str | None: 
+    return shutil.which("aria2c")
+
+
+# NOTE: Function that installs the exe for aria2c on windows devices, takes path as input , returns 
+# path to aria2c exe
+def install_aria2c_windows( APP_DATA_DIR, 
+                            ALLOWED_DOWNLOAD_HOSTS,
+                            log_fn) -> Path:
+
+    ARIA2C_PATH = os.path.join(APP_DATA_DIR, "aria2c.exe")
+
+    ARIA2_ZIP_SHA256 = "35f6514cc5dd7e98a87b3c4c2d25a0754b9b063dbe59bc0f22d483464f61e5b6"
+
+    ARIA2_ZIP_URL = (
+        "https://github.com/aria2/aria2/releases/download/"
+        "release-1.37.0/aria2-1.37.0-win-32bit-build1.zip"
+    )
+
+    #req = urllib.request.Request(ARIA2_ZIP_URL, headers={"User-Agent": UA})
+    req = urllib.request.Request(ARIA2_ZIP_URL)
+    log_fn("Fetching aria2c (one-time, ~2.5 MB)…", "acct")
+
+    with secure_urlopen(req, timeout=60, allowed_hosts=ALLOWED_DOWNLOAD_HOSTS) as r:
+        data = r.read()
+
+    digest = hashlib.sha256(data).hexdigest()
+
+    if digest != ARIA2_ZIP_SHA256:
+        raise RuntimeError(
+            f"aria2 checksum mismatch (got {digest[:12]}…); refusing to run it")
+
+    import zipfile, io
+    with zipfile.ZipFile(io.BytesIO(data)) as zf:
+        name = next((n for n in zf.namelist()
+                     if n.lower().endswith("aria2c.exe")), None)
+        if not name:
+            raise RuntimeError("aria2c.exe not found in the aria2 archive")
+        exe = zf.read(name)
+
+    ensure_dir(APP_DATA_DIR)
+    tmp = ARIA2C_PATH + ".part"
+    with open(tmp, "wb") as f:
+        f.write(exe)
+    os.replace(tmp, ARIA2C_PATH)
+    log_fn("aria2c ready.", "ok")
+
+    return ARIA2C_PATH
+
+
+        
+