Add internal/kctl and internal/config packages with unit tests

internal/config/config.go

@@ -0,0 +1,48 @@
+// Package config loads the user-specific, non-versioned kctl-tui
+// configuration (context pairs, team label key) from a YAML file.
+package config
+
+import (
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v3"
+
+	"github.com/skoelle/kctl-tui/internal/kctl"
+)
+
+// Config is the root structure of ~/.kctl-tui/config.yaml
+type Config struct {
+	ContextPairs []kctl.ContextPair `yaml:"context_pairs"`
+	TeamLabelKey string              `yaml:"team_label_key"`
+}
+
+// DefaultPath returns the default config file location: ~/.kctl-tui/config.yaml
+func DefaultPath() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, ".kctl-tui", "config.yaml"), nil
+}
+
+// Load reads and parses the config file at path. If the file does not
+// exist, it returns a zero-value Config (no pairs, empty label key) and no
+// error, so the tool can run with sane defaults before the user has set up
+// a config file.
+func Load(path string) (Config, error) {
+	cfg := Config{}
+
+	data, err := os.ReadFile(path)
+	if os.IsNotExist(err) {
+		return cfg, nil
+	}
+	if err != nil {
+		return cfg, err
+	}
+
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return cfg, err
+	}
+	return cfg, nil
+}