Cache release metadata on disk

Author: AnastaZIuk

README.md

@@ -17,14 +17,20 @@
 
 ## Introduction
 
-This repository is meant to hold lightweight metadata for shared Nabla assets and CI references without forcing large binary payloads into normal Git history.
+This repository provides the NAM consumer module together with the first-party
+Nabla manifest registry and release-backed payload channels, without forcing
+large binary payloads into normal Git history.
 
 The repository itself is first-party Nabla infrastructure, but the consumer
 module is not meant to be Nabla-only. Other projects can vendor
 `nam.cmake`, keep their own `.dvc`-based manifest repository, publish payloads
 through `GitHub Release assets`, and reuse the same build-time materialization
 model.
 
+Current scope is intentionally narrow. For now the only supported remote
+payload backend is `GitHub Release assets`, and no additional backends are
+planned in the near term.
+
 The current Nabla examples layout at:
 
 - `https://github.com/Devsh-Graphics-Programming/Nabla-Example-And-Tests-Media`

cmake/NablaAssetManifests.cmake

@@ -347,11 +347,29 @@ function(_nam_get_github_release_json OUT_JSON_VAR)
     set(_meta_dir "${_cache_root}/meta/${NAM_REPO}")
     file(MAKE_DIRECTORY "${_meta_dir}")
     set(_json_file "${_meta_dir}/${NAM_TAG}.json")
+    if (EXISTS "${_json_file}")
+        file(READ "${_json_file}" _cached_file_json)
+        if (NOT _cached_file_json STREQUAL "")
+            set_property(GLOBAL PROPERTY "${_cache_key}" "${_cached_file_json}")
+            set(${OUT_JSON_VAR} "${_cached_file_json}" PARENT_SCOPE)
+            return()
+        endif()
+    endif()
+
     set(_api_url "https://api.github.com/repos/${NAM_REPO}/releases/tags/${NAM_TAG}")
-    file(DOWNLOAD "${_api_url}" "${_json_file}" STATUS _status)
-    list(GET _status 0 _status_code)
-    if (NOT _status_code EQUAL 0)
-        message(FATAL_ERROR "NablaAssetManifests: failed to query release metadata for `${NAM_REPO}` tag `${NAM_TAG}`")
+    set(_download_ok OFF)
+    set(_last_status_code "")
+    foreach(_attempt RANGE 1 3)
+        file(DOWNLOAD "${_api_url}" "${_json_file}" STATUS _status TLS_VERIFY ON)
+        list(GET _status 0 _status_code)
+        set(_last_status_code "${_status_code}")
+        if (_status_code EQUAL 0)
+            set(_download_ok ON)
+            break()
+        endif()
+    endforeach()
+    if (NOT _download_ok)
+        message(FATAL_ERROR "NablaAssetManifests: failed to query release metadata for `${NAM_REPO}` tag `${NAM_TAG}` after 3 attempts, last status `${_last_status_code}`")
     endif()
     file(READ "${_json_file}" _json)
     if (_json STREQUAL "")