inputs: new input type org.osbuild.containers-storage

An input that pairs with the org.osbuild.containers-storage source. It
makes the host container storage available to a stage and a container ID
for the stage to use.

Unlike all the other input types, this input does not refer to static
objects in the osbuild sources store but a dynamically mounted container
store that depends on the host storage configuration and the
availability of specific containers in that store.

Co-authored-by: Achilleas Koutsou <achilleas@koutsou.net>
Co-authored-by: Gianluca Zuccarelli <gzuccare@redhat.com>

inputs/org.osbuild.containers-storage

@@ -0,0 +1,145 @@
+#!/usr/bin/python3
+"""Inputs for container images from the host storage
+
+This is an input that pairs with the org.osbuild.containers-storage
+source. It makes the host container storage available to a stage
+and a container ID for the stage to use.
+
+Unlike all the other input types, this does not refer to static
+objects in the osbuild sources store but a dynamically mounted
+container store that depends on the availability of the
+resource (the specific container) on the host.
+"""
+
+import os
+import sys
+
+from osbuild import inputs
+from osbuild.util import containers
+from osbuild.util.mnt import MountGuard
+
+SCHEMA = r"""
+"definitions": {
+  "source-options": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {
+      "name": {
+        "type": "string",
+        "description": "The name to use for the image"
+      }
+    }
+  },
+  "source-object-ref": {
+    "type": "object",
+    "additionalProperties": false,
+    "minProperties": 1,
+    "patternProperties": {
+      ".*": {
+        "$ref": "#/definitions/source-options"
+      }
+    }
+  },
+  "source-array-ref": {
+    "type": "array",
+    "minItems": 1,
+    "items": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["id"],
+      "properties": {
+        "id": {
+          "type": "string"
+        },
+        "options": {
+          "$ref": "#/definitions/source-options"
+        }
+      }
+    }
+  },
+  "source-origin": {
+    "type": "string",
+    "description": "When the origin of the input is a source",
+    "enum": ["org.osbuild.source"]
+  }
+},
+"additionalProperties": false,
+"required": ["type", "origin", "references"],
+"properties": {
+  "type": {
+    "enum": ["org.osbuild.containers-storage"]
+  },
+  "origin": {
+    "description": "The org.osbuild.source origin case",
+    "$ref": "#/definitions/source-origin"
+  },
+  "references": {
+    "description": "Container image id",
+     "oneOf": [
+      {"$ref": "#/definitions/source-array-ref"},
+      {"$ref": "#/definitions/source-object-ref"}
+    ]
+  }
+}
+"""
+
+
+class ContainersInput(inputs.InputService):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.mg = MountGuard()
+        self.storage_conf = None
+
+    def map_storage_ref(self, _source, ref, target):
+        # we only want to read the host once and only for inputs that
+        # require it. If we do this for all inputs, reading the host
+        # may cause unexpected errors.
+        if self.storage_conf is None:
+            self.storage_conf = containers.get_host_storage()
+
+        source = self.storage_conf["storage"]["graphroot"]
+        dest = os.path.join(target, "storage")
+
+        # bind mount the input directory to the destination
+        os.makedirs(dest, exist_ok=True)
+        self.mg.mount(source, dest)
+
+        return ref, "containers-storage"
+
+    def map(self, store, origin, refs, target, _options):
+        images = {}
+
+        for ref, data in refs.items():
+            source = "org.osbuild.containers-storage"
+            ref, container_format = self.map_storage_ref(source, ref, target)
+
+            images[ref] = {
+                "format": container_format,
+                "name": data["name"]
+            }
+            images[ref]["name"] = data["name"]
+
+            if container_format == "containers-storage" and self.storage_conf is not None:
+                images[ref]["storage"] = self.storage_conf["storage"]
+
+        reply = {
+            "path": target,
+            "data": {
+                "archives": images
+            }
+        }
+
+        return reply
+
+    def unmap(self):
+        self.mg.umount()
+
+
+def main():
+    service = ContainersInput.from_args(sys.argv[1:])
+    service.main()
+
+
+if __name__ == '__main__':
+    main()