feat: support debian flat repository format

MODULE.bazel

@@ -10,6 +10,7 @@ bazel_dep(name = "bazel_skylib", version = "1.5.0")
 bazel_dep(name = "aspect_bazel_lib", version = "2.7.3")
 bazel_dep(name = "container_structure_test", version = "1.16.0")
 bazel_dep(name = "rules_oci", version = "1.7.4")
+bazel_dep(name = "rules_pkg", version = "0.10.1")
 
 bazel_lib_toolchains = use_extension("@aspect_bazel_lib//lib:extensions.bzl", "toolchains")
 use_repo(bazel_lib_toolchains, "bsd_tar_toolchains")

apt/private/lockfile.bzl

@@ -16,11 +16,29 @@ def _add_package(lock, package, arch):
     k = _package_key(package, arch)
     if k in lock.fast_package_lookup:
         return
+
+    filename = package["Filename"]
+    url_root = package["Root"]
+
+    # Takes element following last '/' in string, evaluates if it is a known archive type
+    url_last_elem = package["Root"].rsplit("/", 1)[-1]
+    if url_last_elem.endswith(".gz") or url_last_elem.endswith(".xz"):
+        url_root = url_root.replace(url_last_elem, "")
+
+    # Package filename may be parsed as a relative path. Deconstruct the string, see if there is overlap with the URL
+    if filename.split("/", 1)[0] in url_root:
+        filename = filename.replace(filename.split("/", 1)[0], "")
+
+    url_root = url_root.removesuffix("/")
+    filename = filename.removeprefix("/")
+
+    url = "%s/%s" % (url_root, filename)
+
     lock.packages.append({
         "key": k,
         "name": package["Package"],
         "version": package["Version"],
-        "url": "%s/%s" % (package["Root"], package["Filename"]),
+        "url": url,
         "sha256": package["SHA256"],
         "arch": arch,
         "dependencies": [],

apt/private/package_index.bzl

@@ -9,19 +9,34 @@ def _fetch_package_index(rctx, url, dist, comp, arch, integrity):
     r = {"success": False, "integrity": None}
 
     decompression_successful = False
+
     for file_type, tool in file_types.items():
         output = "{}/Packages.{}".format(target_triple, file_type)
-        r = rctx.download(
-            url = "{}/dists/{}/{}/binary-{}/Packages.{}".format(url, dist, comp, arch, file_type),
-            output = output,
-            integrity = integrity,
-            allow_fail = True,
-        )
-        if r.success:
-            re = rctx.execute(tool + [output])
-            if re.return_code == 0:
-                decompression_successful = True
-                break
+
+        # Attempt to pull Packages archive from within the `dists` hierarchy first,
+        # if that fails - assume the repository is of type "flat"
+        try_urls = [
+            "{}/dists/{}/{}/binary-{}/Packages.{}".format(url, dist, comp, arch, file_type),
+            "{}/Packages.{}".format(url, file_type),
+        ]
+
+        for try_url in try_urls:
+            r = rctx.download(
+                url = try_url,
+                output = output,
+                integrity = integrity,
+                allow_fail = True,
+            )
+            if r.success:
+                re = rctx.execute(tool + [output])
+                if re.return_code == 0:
+                    decompression_successful = True
+                    break
+        # If we've set `decompression_successful` to true at any point in the iteration loop,
+        # break out of the loop as we have found and extracted the Package archive and have what is
+        # needed to continue.
+        if decompression_successful:
+            break
 
     if not r.success:
         fail("unable to download package index")