added support for invocation image

README.md

@@ -100,6 +100,27 @@ with open("/home/garethr/.kube/config") as f:
 Note that error handling for this is very work-in-progress.
 
 
+## Working with invocation images
+
+`pycnab` also has a class for working with invocation images.
+
+```python
+from cnab import CNABDirectory
+
+directory = CNABDirectory("fixtures/invocationimage")
+
+# Check whether the directory is valid
+# Raises `InvalidCNABDirectory` exception if invalid
+directory.valid()
+
+# Returns the text of the associated README file if present
+directory.readme()
+
+# Returns the text of the associated LICENSE file if present
+directory.license()
+```
+
+
 ## Thanks
 
 Thanks to [QuickType](https://quicktype.io/) for bootstrapping the creation of the Python code for manipulating `bundle.json` based on the current JSON Schema.

cnab/__init__.py

@@ -12,3 +12,4 @@ from cnab.types import (
     Bundle,
 )
 from cnab.cnab import CNAB
+from cnab.invocation_image import CNABDirectory

cnab/invocation_image.py

@@ -0,0 +1,81 @@
+import os
+from typing import Union
+
+
+class InvalidCNABDirectoryError(Exception):
+    pass
+
+
+class CNABDirectory(object):
+    path: str
+
+    def __init__(self, path: str):
+        self.path = path
+
+    def has_cnab_directory(self) -> bool:
+        cnab = os.path.join(self.path, "cnab")
+        return os.path.isdir(cnab)
+
+    def has_app_directory(self) -> bool:
+        app = os.path.join(self.path, "cnab", "app")
+        return os.path.isdir(app)
+
+    def has_no_misc_files_in_cnab_dir(self) -> bool:
+        cnab = os.path.join(self.path, "cnab")
+        for root, dirs, files in os.walk(cnab):
+            disallowed_dirs = [x for x in dirs if x not in ["app", "build"]]
+            disallowed_files = [
+                x for x in files if x not in ["LICENSE", "README.md", "README.txt"]
+            ]
+            break
+        if disallowed_dirs or disallowed_files:
+            return False
+        else:
+            return True
+
+    def has_run(self) -> bool:
+        run = os.path.join(self.path, "cnab", "app", "run")
+        return os.path.isfile(run)
+
+    def has_executable_run(self) -> bool:
+        run = os.path.join(self.path, "cnab", "app", "run")
+        return os.access(run, os.X_OK)
+
+    def readme(self) -> Union[bool, str]:
+        readme = os.path.join(self.path, "cnab", "README")
+        txt = readme + ".txt"
+        md = readme + ".md"
+        if os.path.isfile(txt):
+            with open(txt, "r") as content:
+                return content.read()
+        elif os.path.isfile(md):
+            with open(md, "r") as content:
+                return content.read()
+        else:
+            return False
+
+    def license(self) -> Union[bool, str]:
+        license = os.path.join(self.path, "cnab", "LICENSE")
+        if os.path.isfile(license):
+            with open(license, "r") as content:
+                return content.read()
+        else:
+            return False
+
+    def valid(self) -> bool:
+        errors = []
+        if not self.has_executable_run():
+            errors.append("Run entrypoint is not executable")
+        if not self.has_run():
+            errors.append("Missing a run entrypoint")
+        if not self.has_app_directory():
+            errors.append("Missing the app directory")
+        if not self.has_cnab_directory():
+            errors.append("Missing the cnab directory")
+        if not self.has_no_misc_files_in_cnab_dir():
+            errors.append("Has additional files in the cnab directory")
+
+        if len(errors) == 0:
+            return True
+        else:
+            raise InvalidCNABDirectoryError(errors)

cnab/test_invocation_image.py

@@ -0,0 +1,69 @@
+import pytest  # type: ignore
+
+from cnab import CNABDirectory
+from cnab.invocation_image import InvalidCNABDirectoryError
+
+
+class SampleCNAB(object):
+    @pytest.fixture
+    def directory(self):
+        return CNABDirectory("fixtures/invocationimage")
+
+
+class TestCNABDirectory(SampleCNAB):
+    def test_has_app_dir(self, directory):
+        assert directory.has_app_directory()
+
+    def test_has_cnab_dir(self, directory):
+        assert directory.has_cnab_directory()
+
+    def test_has_readme(self, directory):
+        assert isinstance(directory.readme(), str)
+
+    def test_has_license(self, directory):
+        assert isinstance(directory.license(), str)
+
+    def test_has_no_misc_files(self, directory):
+        assert directory.has_no_misc_files_in_cnab_dir()
+
+    def test_has_run(self, directory):
+        assert directory.has_run()
+
+    def test_has_executable(self, directory):
+        assert directory.has_executable_run()
+
+    def test_is_valid(self, directory):
+        assert directory.valid()
+
+
+class InvalidCNAB(object):
+    @pytest.fixture
+    def directory(self):
+        return CNABDirectory("fixtures/invalidinvocationimage")
+
+
+class TestInvalidCNABDirectory(InvalidCNAB):
+    def test_has_no_app_dir(self, directory):
+        assert not directory.has_app_directory()
+
+    def test_has_cnab_dir(self, directory):
+        assert directory.has_cnab_directory()
+
+    def test_has_readme(self, directory):
+        assert isinstance(directory.readme(), str)
+
+    def test_has_no_license(self, directory):
+        assert not directory.license()
+
+    def test_has_invalid_misc_files(self, directory):
+        assert not directory.has_no_misc_files_in_cnab_dir()
+
+    def test_has_no_run(self, directory):
+        assert not directory.has_run()
+
+    def test_has_no_executable(self, directory):
+        assert not directory.has_executable_run()
+
+    def test_is_invalid(self, directory):
+        with pytest.raises(InvalidCNABDirectoryError):
+            directory.valid()

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "cnab"
-version = "0.1.4"
+version = "0.1.5"
 description = "A module for working with Cloud Native Application Bundles in Python"
 authors = ["Gareth Rushgrove <gareth@morethanseven.net>"]
 license = "Apache-2.0"

pytest.ini

@@ -1,5 +1,7 @@
 [pytest]
 addopts = --black --mypy --verbose --ignore scratch --cov=cnab --cov-report term-missing
+filterwarnings =
+    ignore::DeprecationWarning
 
 markers =
     docker: tests which rely on Docker