From 69729de4663b43a5d05fb2f6f219590ec27f419c Mon Sep 17 00:00:00 2001
From: Evan Lezar <elezar@nvidia.com>
Date: Mon, 20 Jan 2025 13:47:37 +0100
Subject: [PATCH] Add logic to detect minimum spec version on save

Signed-off-by: Evan Lezar <elezar@nvidia.com>
---
 api/producer/options.go             | 15 +++++++++---
 api/producer/set-minimum-version.go | 36 +++++++++++++++++++++++++++++
 api/producer/spec-format.go         | 13 +++++++++++
 api/producer/writer.go              |  5 ++--
 api/producer/writer_test.go         | 19 +++++++++++++++
 5 files changed, 83 insertions(+), 5 deletions(-)
 create mode 100644 api/producer/set-minimum-version.go

diff --git a/api/producer/options.go b/api/producer/options.go
index 8c247866..c8f0b1ef 100644
--- a/api/producer/options.go
+++ b/api/producer/options.go
@@ -25,9 +25,18 @@ import (
 type Option func(*options) error
 
 type options struct {
-	specFormat  SpecFormat
-	overwrite   bool
-	permissions fs.FileMode
+	specFormat           SpecFormat
+	overwrite            bool
+	permissions          fs.FileMode
+	detectMinimumVersion bool
+}
+
+// WithDetectMinimumVersion toggles whether a minimum version should be detected for a CDI specification.
+func WithDetectMinimumVersion(detectMinimumVersion bool) Option {
+	return func(o *options) error {
+		o.detectMinimumVersion = detectMinimumVersion
+		return nil
+	}
 }
 
 // WithSpecFormat sets the output format of a CDI specification.
diff --git a/api/producer/set-minimum-version.go b/api/producer/set-minimum-version.go
new file mode 100644
index 00000000..29474204
--- /dev/null
+++ b/api/producer/set-minimum-version.go
@@ -0,0 +1,36 @@
+/*
+   Copyright © 2025 The CDI Authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package producer
+
+import (
+	"fmt"
+
+	cdi "tags.cncf.io/container-device-interface/specs-go"
+)
+
+type setMinimumRequiredVersion struct{}
+
+// Transform detects the minimum required version required for the specified
+// spec and sets the version field accordingly.
+func (d setMinimumRequiredVersion) Transform(spec *cdi.Spec) error {
+	minVersion, err := cdi.MinimumRequiredVersion(spec)
+	if err != nil {
+		return fmt.Errorf("failed to get minimum required CDI spec version: %w", err)
+	}
+	spec.Version = minVersion
+	return nil
+}
diff --git a/api/producer/spec-format.go b/api/producer/spec-format.go
index 7e4eebbb..d2900f72 100644
--- a/api/producer/spec-format.go
+++ b/api/producer/spec-format.go
@@ -83,9 +83,22 @@ func (p *specFormatter) validate() error {
 	return nil
 }
 
+// transform applies a transform to the spec associated with the CDI spec formatter.
+// This is currently limited to detecting (and updating) the spec so that the minimum
+// CDI spec version is used, but could be extended to apply other transformations.
+func (p *specFormatter) transform() error {
+	if !p.detectMinimumVersion {
+		return nil
+	}
+	return (&setMinimumRequiredVersion{}).Transform(p.Spec)
+}
+
 // contents returns the raw contents of a CDI specification.
 // Validation is performed before marshalling the contentent based on the spec format.
 func (p *specFormatter) contents() ([]byte, error) {
+	if err := p.transform(); err != nil {
+		return nil, fmt.Errorf("failed to transform spec: %w", err)
+	}
 	if err := p.validate(); err != nil {
 		return nil, fmt.Errorf("spec validation failed: %w", err)
 	}
diff --git a/api/producer/writer.go b/api/producer/writer.go
index dd9f1161..e25c6bc1 100644
--- a/api/producer/writer.go
+++ b/api/producer/writer.go
@@ -36,8 +36,9 @@ func NewSpecWriter(opts ...Option) (*SpecWriter, error) {
 		options: options{
 			overwrite: true,
 			// TODO: This could be updated to 0644 to be world-readable.
-			permissions: 0600,
-			specFormat:  DefaultSpecFormat,
+			permissions:          0600,
+			specFormat:           DefaultSpecFormat,
+			detectMinimumVersion: false,
 		},
 	}
 	for _, opt := range opts {
diff --git a/api/producer/writer_test.go b/api/producer/writer_test.go
index 778d6a5d..64bbf5a9 100644
--- a/api/producer/writer_test.go
+++ b/api/producer/writer_test.go
@@ -126,6 +126,25 @@ devices: null
 kind: example.com/class
 `,
 		},
+		{
+			description: "minimum version is detected",
+			spec: cdi.Spec{
+				Version: cdi.CurrentVersion,
+				Kind:    "example.com/class",
+				ContainerEdits: cdi.ContainerEdits{
+					DeviceNodes: []*cdi.DeviceNode{
+						{
+							Path: "/dev/foo",
+						},
+					},
+				},
+			},
+			options:             []Option{WithDetectMinimumVersion(true)},
+			filename:            "foo",
+			expectedFilename:    "foo.yaml",
+			expectedPermissions: 0600,
+			expectedOutput: `---
+cdiVersion: 0.3.0
 containerEdits:
   deviceNodes:
   - path: /dev/foo