From 3e379d0e04c7fbe515a5e395470bbd1ae9c0c6d2 Mon Sep 17 00:00:00 2001
From: David Son <davbson@amazon.com>
Date: Tue, 10 Sep 2024 19:20:16 +0000
Subject: [PATCH] feat: add support for finch-daemon.yaml

Signed-off-by: David Son <davbson@amazon.com>
---
 cmd/finch-daemon/main.go | 14 ++++++++++++++
 go.mod                   |  2 +-
 pkg/config/config.go     | 41 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 pkg/config/config.go

diff --git a/cmd/finch-daemon/main.go b/cmd/finch-daemon/main.go
index 5b9d1dc..ab0a6e5 100644
--- a/cmd/finch-daemon/main.go
+++ b/cmd/finch-daemon/main.go
@@ -34,6 +34,7 @@ import (
 	"github.com/runfinch/finch-daemon/internal/service/system"
 	"github.com/runfinch/finch-daemon/internal/service/volume"
 	"github.com/runfinch/finch-daemon/pkg/archive"
+	daemonConfig "github.com/runfinch/finch-daemon/pkg/config"
 	"github.com/runfinch/finch-daemon/pkg/ecc"
 	"github.com/runfinch/finch-daemon/pkg/flog"
 )
@@ -49,6 +50,7 @@ type DaemonOptions struct {
 	socketAddr  string
 	socketOwner int
 	regoPath    string
+	configPath  string
 }
 
 var options = new(DaemonOptions)
@@ -68,6 +70,7 @@ func main() {
 		" (more info: https://github.com/lima-vm/lima/blob/5a9bca3d09481ed7109b14f8d3f0074816731f43/examples/default.yaml#L340)."+
 		" -1 means no-op.")
 	rootCmd.Flags().StringVar(&options.regoPath, "rego-path", "", "Optional path to a rego policy. Currently only allowlist/denylist options are available")
+	rootCmd.Flags().StringVar(&options.configPath, "config", "", "Optional path to a settings YAML file (finch-daemon.yaml)")
 	if err := rootCmd.Execute(); err != nil {
 		log.Printf("got error: %v", err)
 		log.Fatal(err)
@@ -79,6 +82,17 @@ func runAdapter(cmd *cobra.Command, _ []string) error {
 }
 
 func run(options *DaemonOptions) error {
+	if options.configPath != "" {
+		cfg, err := daemonConfig.Load(options.configPath)
+		if err != nil {
+			return fmt.Errorf("could not read from %v: %v", options.configPath, err)
+		}
+
+		if options.regoPath == "" {
+			options.regoPath = cfg.RegoPath
+		}
+	}
+
 	// This sets the log level of the dependencies that use logrus (e.g., containerd library).
 	if options.debug {
 		logrus.SetLevel(logrus.DebugLevel)
diff --git a/go.mod b/go.mod
index 89e29f0..24aa49c 100644
--- a/go.mod
+++ b/go.mod
@@ -39,6 +39,7 @@ require (
 	golang.org/x/net v0.28.0
 	golang.org/x/sys v0.23.0
 	google.golang.org/protobuf v1.34.2
+	gopkg.in/yaml.v2 v2.4.0
 )
 
 require (
@@ -167,7 +168,6 @@ require (
 	google.golang.org/genproto v0.0.0-20240401170217-c3f982113cda // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240701130421-f6361c86f094 // indirect
 	google.golang.org/grpc v1.66.0 // indirect
-	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	k8s.io/cri-api v0.29.3 // indirect
 	lukechampine.com/blake3 v1.2.1 // indirect
diff --git a/pkg/config/config.go b/pkg/config/config.go
new file mode 100644
index 0000000..ef1dc40
--- /dev/null
+++ b/pkg/config/config.go
@@ -0,0 +1,41 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"gopkg.in/yaml.v2"
+)
+
+type Config struct {
+	RegoPath string `yaml:"rego_path,omitempty"`
+}
+
+// Load reads a YAML file from a given location and returns a new Config struct.
+func Load(cfgPath string) (*Config, error) {
+	b, err := os.ReadFile(cfgPath)
+	if err != nil {
+		// Ignore file not found errors
+		if errors.Is(err, os.ErrNotExist) {
+			return &Config{}, nil
+		}
+		return &Config{}, err
+	}
+
+	cfg := CreateDefaultConfig()
+	if err := yaml.Unmarshal(b, cfg); err != nil {
+		return &Config{}, fmt.Errorf("failed to unmarshal config file: %w", err)
+	}
+
+	return cfg, nil
+}
+
+func CreateDefaultConfig() *Config {
+	return &Config{
+		RegoPath: "",
+	}
+}