feat: implement oci_index

oci/defs.bzl

@@ -1,7 +1,9 @@
 load("//oci/private:tarball.bzl", _oci_tarball = "oci_tarball")
 load("//oci/private:image.bzl", _oci_image = "oci_image")
+load("//oci/private:index.bzl", _oci_index = "oci_index")
 load("//oci/private:structure_test.bzl", _structure_test = "structure_test")
 
 oci_tarball = _oci_tarball
 oci_image = _oci_image
+oci_index = _oci_index
 structure_test = _structure_test

oci/private/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 
-exports_files(["image.sh.tpl", "tarball.sh.tpl"])
+exports_files(["image.sh.tpl", "index.sh.tpl", "tarball.sh.tpl"])
 
 filegroup(
     name = "package_content",

oci/private/index.bzl

@@ -0,0 +1,42 @@
+
+def _index_impl(ctx):
+    jq = ctx.toolchains["@aspect_bazel_lib//lib:jq_toolchain_type"]
+
+    launcher = ctx.actions.declare_file("index_%s.sh" % ctx.label.name)
+    ctx.actions.expand_template(
+        template = ctx.file._index_sh_tpl,
+        output = launcher,
+        is_executable = True,
+        substitutions = {
+            "{jq_path}": jq.jqinfo.bin.path,
+        }
+    )
+
+    output = ctx.actions.declare_directory(ctx.label.name)
+
+    args = ctx.actions.args()
+    args.add(output.path)
+    args.add_all(ctx.files.images, expand_directories = False)
+
+    ctx.actions.run(
+        inputs = ctx.files.images,
+        arguments = [args],
+        outputs = [output],
+        executable = launcher,
+        tools = [jq.jqinfo.bin],
+        progress_message = "OCI Index %{label}",
+    )
+
+    return DefaultInfo(files = depset([output]))
+
+
+oci_index = rule(
+    implementation = _index_impl,
+    attrs = {
+        "images": attr.label_list(mandatory = True, doc = "TODO"),
+        "_index_sh_tpl": attr.label(default = "index.sh.tpl", allow_single_file = True),
+    },
+    toolchains = [
+        "@aspect_bazel_lib//lib:jq_toolchain_type"
+    ]
+)

oci/private/index.sh.tpl

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+set -o pipefail -o errexit -o nounset
+
+JQ="{jq_path}"
+INDEX="$1"
+shift
+
+mkdir -p $INDEX
+$JQ -n '{imageLayoutVersion: "1.0.0"}' > "$INDEX/oci-layout" 
+
+MANIFEST_LIST=$(mktemp)
+$JQ -n '{"schemaVersion": 2, mediaType: "application/vnd.oci.image.index.v1+json", manifests: []}' > $MANIFEST_LIST
+
+
+for IMAGE in $@; do
+    if [ ! -d "$IMAGE" ]; then
+        echo "$IMAGE is not a directory."
+        exit 1
+    fi 
+    if [ ! -f "$IMAGE/oci-layout" ]; then 
+        echo "$IMAGE/oci-layout is not a valid oci-layout."
+        exit 1
+    fi
+
+    for P in $(cd "$IMAGE/blobs" && find . -maxdepth 2); do
+        if [ -d "$IMAGE/blobs/$P" ]; then 
+            mkdir -p "$INDEX/blobs/$P"
+        fi 
+        # TODO: find out why cp -r fails.
+        if [ -f "$IMAGE/blobs/$P" ]; then
+            cat "$IMAGE/blobs/$P" > "$INDEX/blobs/$P"
+        fi 
+    done
+
+    for MANIFEST in $($JQ -c '.manifests[]' "$IMAGE/index.json"); do
+        MANIFEST_BLOB=$($JQ -r '.digest | sub(":"; "/")' <<< $MANIFEST)
+        CONFIG_BLOB=$($JQ -r '.config.digest | sub(":"; "/")' "$IMAGE/blobs/$MANIFEST_BLOB")
+
+        PLATFORM=$($JQ -c '{os: .os, architecture: .architecture, variant: .variant, "os.version": .["os.version"], "os.features": .["os.features"]} | with_entries(select( .value != null ))' < "$IMAGE/blobs/$CONFIG_BLOB")
+
+        TMP=$(mktemp)
+        $JQ --argjson platform "$PLATFORM" --argjson manifest "$MANIFEST" '.manifests += [$manifest + {platform: $platform}] | .' $MANIFEST_LIST > $TMP
+        MANIFEST_LIST=$TMP
+    done
+
+done
+
+SHA=$(shasum -a 256 $MANIFEST_LIST | cut -f 1 -d " ")
+SIZE=$(wc -c < $MANIFEST_LIST)
+mv $MANIFEST_LIST "$INDEX/blobs/sha256/$SHA"
+$JQ -n --arg size $SIZE --arg sha $SHA '{schemaVersion: 2, manifests: [{mediaType: "application/vnd.oci.image.index.v1+json", size: ($size | tonumber), digest: ("sha256:" + $sha)}]}' > "$INDEX/index.json"