Add configuration management with Viper (Topic 2)

go.mod

@@ -6,17 +6,26 @@ require (
 	github.com/onsi/ginkgo/v2 v2.28.1
 	github.com/onsi/gomega v1.39.1
 	github.com/spf13/cobra v1.10.2
+	github.com/spf13/viper v1.21.0
 	go.yaml.in/yaml/v3 v3.0.4
 )
 
 require (
 	github.com/Masterminds/semver/v3 v3.4.0 // indirect
+	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-task/slim-sprig/v3 v3.0.0 // indirect
+	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
 	github.com/google/pprof v0.0.0-20260115054156-294ebfa9ad83 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
-	github.com/spf13/pflag v1.0.9 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
+	github.com/sagikazarmark/locafero v0.11.0 // indirect
+	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
+	github.com/spf13/afero v1.15.0 // indirect
+	github.com/spf13/cast v1.10.0 // indirect
+	github.com/spf13/pflag v1.0.10 // indirect
+	github.com/subosito/gotenv v1.6.0 // indirect
 	golang.org/x/mod v0.32.0 // indirect
 	golang.org/x/net v0.49.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect

go.sum

@@ -3,6 +3,10 @@ github.com/Masterminds/semver/v3 v3.4.0/go.mod h1:4V+yj/TJE1HU9XfppCwVMZq3I84lpr
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
+github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/gkampitakis/ciinfo v0.3.2 h1:JcuOPk8ZU7nZQjdUhctuhQofk7BGHuIy0c9Ez8BNhXs=
 github.com/gkampitakis/ciinfo v0.3.2/go.mod h1:1NIwaOcFChN4fa/B0hEBdAb6npDlFL8Bwx4dfRLRqAo=
 github.com/gkampitakis/go-diff v1.3.2 h1:Qyn0J9XJSDTgnsgHRdz9Zp24RaJeKMUHg2+PDZZdC4M=
@@ -13,6 +17,8 @@ github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-task/slim-sprig/v3 v3.0.0 h1:sUs3vkvUymDpBKi3qH1YSqBQk9+9D/8M2mN1vB6EwHI=
 github.com/go-task/slim-sprig/v3 v3.0.0/go.mod h1:W848ghGpv3Qj3dhTPRyJypKRiqCdHZiAzKg9hl15HA8=
+github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9LvH92wZUgs=
+github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/goccy/go-yaml v1.18.0 h1:8W7wMFS12Pcas7KU+VVkaiCng+kG8QiFeFwzFb+rwuw=
 github.com/goccy/go-yaml v1.18.0/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
@@ -35,17 +41,32 @@ github.com/onsi/ginkgo/v2 v2.28.1 h1:S4hj+HbZp40fNKuLUQOYLDgZLwNUVn19N3Atb98NCyI
 github.com/onsi/ginkgo/v2 v2.28.1/go.mod h1:CLtbVInNckU3/+gC8LzkGUb9oF+e8W8TdUsxPwvdOgE=
 github.com/onsi/gomega v1.39.1 h1:1IJLAad4zjPn2PsnhH70V4DKRFlrCzGBNrNaru+Vf28=
 github.com/onsi/gomega v1.39.1/go.mod h1:hL6yVALoTOxeWudERyfppUcZXjMwIMLnuSfruD2lcfg=
+github.com/pelletier/go-toml/v2 v2.2.4 h1:mye9XuhQ6gvn5h28+VilKrrPoQVanw5PMw/TB0t5Ec4=
+github.com/pelletier/go-toml/v2 v2.2.4/go.mod h1:2gIqNv+qfxSVS7cM2xJQKtLSTLUE9V8t9Stt+h56mCY=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR38lUII=
 github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/sagikazarmark/locafero v0.11.0 h1:1iurJgmM9G3PA/I+wWYIOw/5SyBtxapeHDcg+AAIFXc=
+github.com/sagikazarmark/locafero v0.11.0/go.mod h1:nVIGvgyzw595SUSUE6tvCp3YYTeHs15MvlmU87WwIik=
+github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 h1:+jumHNA0Wrelhe64i8F6HNlS8pkoyMv5sreGx2Ry5Rw=
+github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8/go.mod h1:3n1Cwaq1E1/1lhQhtRK2ts/ZwZEhjcQeJQ1RuC6Q/8U=
+github.com/spf13/afero v1.15.0 h1:b/YBCLWAJdFWJTN9cLhiXXcD7mzKn9Dm86dNnfyQw1I=
+github.com/spf13/afero v1.15.0/go.mod h1:NC2ByUVxtQs4b3sIUphxK0NioZnmxgyCrfzeuq8lxMg=
+github.com/spf13/cast v1.10.0 h1:h2x0u2shc1QuLHfxi+cTJvs30+ZAHOGRic8uyGTDWxY=
+github.com/spf13/cast v1.10.0/go.mod h1:jNfB8QC9IA6ZuY2ZjDp0KtFO2LZZlg4S/7bzP6qqeHo=
 github.com/spf13/cobra v1.10.2 h1:DMTTonx5m65Ic0GOoRY2c16WCbHxOOw6xxezuLaBpcU=
 github.com/spf13/cobra v1.10.2/go.mod h1:7C1pvHqHw5A4vrJfjNwvOdzYu0Gml16OCs2GRiTUUS4=
-github.com/spf13/pflag v1.0.9 h1:9exaQaMOCwffKiiiYk6/BndUBv+iRViNW+4lEMi0PvY=
 github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
-github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
+github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/spf13/viper v1.21.0 h1:x5S+0EU27Lbphp4UKm1C+1oQO+rKx36vfCoaVebLFSU=
+github.com/spf13/viper v1.21.0/go.mod h1:P0lhsswPGWD/1lZJ9ny3fYnVqxiegrlNrEmgLjbTCAY=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/subosito/gotenv v1.6.0 h1:9NlTDc1FTs4qu0DDq7AEtTPNw6SVm7uBMsUCUjABIf8=
+github.com/subosito/gotenv v1.6.0/go.mod h1:Dk4QP5c2W3ibzajGcXpNraDfq2IrhjMIvMSWPKKo0FU=
 github.com/tidwall/gjson v1.18.0 h1:FIDeeyB800efLX89e5a8Y0BNH+LOngJyGrIWxG2FKQY=
 github.com/tidwall/gjson v1.18.0/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=
@@ -71,7 +92,7 @@ golang.org/x/tools v0.41.0/go.mod h1:XSY6eDqxVNiYgezAVqqCeihT4j1U2CCsqvH3WhQpnlg
 google.golang.org/protobuf v1.36.7 h1:IgrO7UwFQGJdRNXH/sQux4R1Dj1WAKcLElzeeRaXV2A=
 google.golang.org/protobuf v1.36.7/go.mod h1:jduwjTPXsFjZGTmRluh+L6NjiWu7pchiJ2/5YcXBHnY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
-gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/commands/root.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/dcm-project/cli/internal/config"
 	"github.com/spf13/cobra"
 )
 
@@ -25,6 +26,14 @@ func NewRootCommand() *cobra.Command {
 		CompletionOptions: cobra.CompletionOptions{
 			DisableDefaultCmd: true,
 		},
+		PersistentPreRunE: func(cmd *cobra.Command, _ []string) error {
+			cfg, err := config.Load(cmd)
+			if err != nil {
+				return err
+			}
+			cmd.SetContext(config.WithConfig(cmd.Context(), cfg))
+			return nil
+		},
 	}
 
 	// Wrap flag parsing errors as usage errors (exit code 2).

internal/config/config.go

@@ -0,0 +1,141 @@
+// Package config manages CLI configuration with file persistence,
+// environment variable overrides, and command-line flag overrides.
+package config
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+type contextKey struct{}
+
+// WithConfig stores a Config in the given context.
+func WithConfig(ctx context.Context, cfg *Config) context.Context {
+	return context.WithValue(ctx, contextKey{}, cfg)
+}
+
+// FromContext retrieves the Config from a context. Returns nil if not present.
+func FromContext(ctx context.Context) *Config {
+	cfg, _ := ctx.Value(contextKey{}).(*Config)
+	return cfg
+}
+
+// FromCommand retrieves the Config from a cobra.Command's context.
+func FromCommand(cmd *cobra.Command) *Config {
+	return FromContext(cmd.Context())
+}
+
+// Config holds the resolved CLI configuration.
+type Config struct {
+	APIGatewayURL string `yaml:"api-gateway-url" mapstructure:"api-gateway-url"`
+	OutputFormat  string `yaml:"output-format" mapstructure:"output-format"`
+	Timeout       int    `yaml:"timeout" mapstructure:"timeout"`
+	TLSCACert     string `yaml:"tls-ca-cert" mapstructure:"tls-ca-cert"`
+	TLSClientCert string `yaml:"tls-client-cert" mapstructure:"tls-client-cert"`
+	TLSClientKey  string `yaml:"tls-client-key" mapstructure:"tls-client-key"`
+	TLSSkipVerify bool   `yaml:"tls-skip-verify" mapstructure:"tls-skip-verify"`
+}
+
+// Load reads configuration from file, environment variables, and command-line
+// flags in the precedence order: flags > env vars > config file > defaults.
+func Load(cmd *cobra.Command) (*Config, error) {
+	v := viper.New()
+
+	// Built-in defaults (REQ-CFG-050)
+	v.SetDefault("api-gateway-url", "http://localhost:9080")
+	v.SetDefault("output-format", "table")
+	v.SetDefault("timeout", 30)
+	v.SetDefault("tls-ca-cert", "")
+	v.SetDefault("tls-client-cert", "")
+	v.SetDefault("tls-client-key", "")
+	v.SetDefault("tls-skip-verify", false)
+
+	// Environment variable binding (REQ-CFG-030)
+	v.SetEnvPrefix("DCM")
+	v.MustBindEnv("api-gateway-url", "DCM_API_GATEWAY_URL")
+	v.MustBindEnv("output-format", "DCM_OUTPUT_FORMAT")
+	v.MustBindEnv("timeout", "DCM_TIMEOUT")
+	v.MustBindEnv("tls-ca-cert", "DCM_TLS_CA_CERT")
+	v.MustBindEnv("tls-client-cert", "DCM_TLS_CLIENT_CERT")
+	v.MustBindEnv("tls-client-key", "DCM_TLS_CLIENT_KEY")
+	v.MustBindEnv("tls-skip-verify", "DCM_TLS_SKIP_VERIFY")
+
+	// Config file path (REQ-CFG-010, REQ-CFG-020)
+	configPath := configFilePath(cmd)
+	if configPath != "" {
+		v.SetConfigFile(configPath)
+	} else {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return nil, fmt.Errorf("unable to determine home directory: %w", err)
+		}
+		v.SetConfigFile(filepath.Join(home, ".dcm", "config.yaml"))
+	}
+
+	// Read config file — ignore "not found" errors (REQ-CFG-070)
+	if err := v.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			if !os.IsNotExist(err) {
+				return nil, fmt.Errorf("reading config file: %w", err)
+			}
+		}
+	}
+
+	// Bind CLI flags so they override env vars and config file (REQ-CFG-040)
+	if cmd != nil {
+		if err := bindFlags(v, cmd); err != nil {
+			return nil, err
+		}
+	}
+
+	var cfg Config
+	if err := v.Unmarshal(&cfg); err != nil {
+		return nil, fmt.Errorf("unmarshalling config: %w", err)
+	}
+
+	return &cfg, nil
+}
+
+// configFilePath resolves the config file path from the --config flag
+// or the DCM_CONFIG environment variable.
+func configFilePath(cmd *cobra.Command) string {
+	if cmd != nil {
+		f := cmd.Root().PersistentFlags().Lookup("config")
+		if f != nil && f.Changed {
+			return f.Value.String()
+		}
+	}
+	if v := os.Getenv("DCM_CONFIG"); v != "" {
+		return v
+	}
+	return ""
+}
+
+// bindFlags binds only flags that were explicitly set by the user, so that
+// unset flags don't override environment variables or config file values.
+func bindFlags(v *viper.Viper, cmd *cobra.Command) error {
+	flagToKey := map[string]string{
+		"api-gateway-url": "api-gateway-url",
+		"output":          "output-format",
+		"timeout":         "timeout",
+		"tls-ca-cert":     "tls-ca-cert",
+		"tls-client-cert": "tls-client-cert",
+		"tls-client-key":  "tls-client-key",
+		"tls-skip-verify": "tls-skip-verify",
+	}
+
+	for flagName, configKey := range flagToKey {
+		f := cmd.Root().PersistentFlags().Lookup(flagName)
+		if f != nil && f.Changed {
+			if err := v.BindPFlag(configKey, f); err != nil {
+				return fmt.Errorf("binding flag %s: %w", flagName, err)
+			}
+		}
+	}
+	return nil
+}

internal/config/config_suite_test.go

@@ -0,0 +1,13 @@
+package config_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestConfig(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Config Suite")
+}