refactor: extract core logic to a plain Go package

manager/config.go

@@ -0,0 +1,276 @@
+package manager
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/sethvargo/go-envconfig"
+	"gopkg.in/yaml.v3"
+)
+
+var ErrConfig = fmt.Errorf("%w", Err)
+
+type Mode string
+
+const (
+	User   Mode = "user"
+	System Mode = "system"
+)
+
+type ConfigFile struct {
+	Paths ConfigFilePaths `yaml:"paths" json:"paths"`
+}
+
+type ConfigFilePaths struct {
+	Shims    string `yaml:"shims" json:"shims" env:"EVM_SHIMS,overwrite"`
+	Sources  string `yaml:"sources" json:"sources"  env:"EVM_SOURCES,overwrite"`
+	Versions string `yaml:"versions" json:"versions" env:"EVM_VERSIONS,overwrite"`
+}
+
+type Config struct {
+	Mode    Mode          `yaml:"mode" json:"mode"`
+	Current CurrentConfig `yaml:"current" json:"current"`
+	Paths   PathsConfig   `yaml:"paths" json:"paths"`
+}
+
+type CurrentConfig struct {
+	Version string `yaml:"version" json:"version"`
+	SetBy   string `yaml:"set_by,omitempty" json:"set_by,omitempty"`
+}
+
+type PathsConfig struct {
+	Binary   string `yaml:"binary" json:"binary"`
+	Root     string `yaml:"root" json:"root"`
+	Shims    string `yaml:"shims" json:"shims"`
+	Sources  string `yaml:"sources" json:"sources"`
+	Versions string `yaml:"versions" json:"versions"`
+}
+
+func NewConfig() (*Config, error) {
+	mode := Mode(os.Getenv("EVM_MODE"))
+	if mode != System {
+		mode = User
+	}
+
+	defaultRoot := filepath.Join(string(os.PathSeparator), "opt", "evm")
+	if mode == User {
+		defaultRoot = filepath.Join("$HOME", ".evm")
+	}
+
+	if v := os.Getenv("EVM_ROOT"); v != "" {
+		defaultRoot = v
+	}
+
+	conf := &Config{
+		Mode: mode,
+		Paths: PathsConfig{
+			Root:     defaultRoot,
+			Shims:    "$EVM_ROOT/shims",
+			Sources:  "$EVM_ROOT/sources",
+			Versions: "$EVM_ROOT/versions",
+		},
+	}
+
+	var err error
+	conf.Paths.Root, err = conf.normalizePath(conf.Paths.Root)
+	if err != nil {
+		return nil, err
+	}
+
+	err = conf.load()
+	if err != nil {
+		return nil, err
+	}
+
+	conf.Paths.Shims, err = conf.normalizePath(conf.Paths.Shims)
+	if err != nil {
+		return nil, err
+	}
+	conf.Paths.Sources, err = conf.normalizePath(conf.Paths.Sources)
+	if err != nil {
+		return nil, err
+	}
+	conf.Paths.Versions, err = conf.normalizePath(conf.Paths.Versions)
+	if err != nil {
+		return nil, err
+	}
+
+	conf.Paths.Binary, err = os.Executable()
+	if err != nil {
+		return nil, err
+	}
+
+	err = conf.PopulateCurrent()
+	if err != nil {
+		return nil, err
+	}
+
+	return conf, nil
+}
+
+const currentFileName = "current"
+
+func (conf *Config) PopulateCurrent() error {
+	if v := os.Getenv("EVM_VERSION"); v != "" {
+		conf.Current.Version = strings.TrimSpace(v)
+		conf.Current.SetBy = "EVM_VERSION environment variable"
+
+		return nil
+	}
+
+	currentFile := filepath.Join(conf.Paths.Root, currentFileName)
+	b, err := os.ReadFile(currentFile)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil
+		}
+		return err
+	}
+
+	if len(b) > 0 {
+		conf.Current.Version = strings.TrimSpace(string(b))
+		conf.Current.SetBy = currentFile
+	}
+
+	return nil
+}
+
+var configFileNames = []string{
+	"config.yaml",
+	"config.yml",
+	"config.json",
+	"evm.yaml",
+	"evm.yml",
+	"evm.json",
+}
+
+func (c *Config) load() error {
+	var path string
+	for _, name := range configFileNames {
+		f := filepath.Join(c.Paths.Root, name)
+
+		_, err := os.Stat(f)
+		if err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				continue
+			}
+			return err
+		}
+
+		path = f
+		break
+	}
+
+	cf := &ConfigFile{}
+	if path != "" {
+		var err error
+		cf, err = c.loadConfigFile(path)
+		if err != nil {
+			return err
+		}
+	}
+
+	err := envconfig.Process(context.Background(), cf)
+	if err != nil {
+		return err
+	}
+
+	if cf.Paths.Shims != "" {
+		c.Paths.Shims = cf.Paths.Shims
+	}
+	if cf.Paths.Sources != "" {
+		c.Paths.Sources = cf.Paths.Sources
+	}
+	if cf.Paths.Versions != "" {
+		c.Paths.Versions = cf.Paths.Versions
+	}
+
+	return nil
+}
+
+func (c *Config) loadConfigFile(path string) (*ConfigFile, error) {
+	if path == "" {
+		return nil, nil
+	}
+
+	content, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	cf := &ConfigFile{}
+
+	buf := bytes.NewBuffer(content)
+	switch filepath.Ext(path) {
+	case ".yaml", ".yml":
+		dec := yaml.NewDecoder(buf)
+		dec.KnownFields(true)
+		err = dec.Decode(cf)
+	case ".json":
+		dec := json.NewDecoder(buf)
+		dec.DisallowUnknownFields()
+		err = dec.Decode(cf)
+	default:
+		return nil, fmt.Errorf(
+			`%w"%s" does not have a ".yaml", ".yml", `+
+				`or ".json" file extension`,
+			ErrConfig, path,
+		)
+	}
+	if err != nil && !errors.Is(err, io.EOF) {
+		return nil, err
+	}
+
+	return cf, nil
+}
+
+func (c *Config) normalizePath(path string) (string, error) {
+	path = strings.TrimSpace(path)
+
+	var homePrefix string
+	switch {
+	case strings.HasPrefix(path, "$HOME") ||
+		strings.HasPrefix(path, "$home"):
+		homePrefix = path[0:5]
+	case strings.HasPrefix(path, "~"):
+		homePrefix = path[0:1]
+	}
+
+	if homePrefix != "" {
+		if c.Mode == System {
+			return "", fmt.Errorf(
+				`%wEVM_MODE is set to "%s" which prohibits `+
+					`using "$HOME" or "~" in EVM_ROOT`,
+				ErrConfig, string(System),
+			)
+		}
+
+		var home string
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return "", err
+		}
+		path = filepath.Join(
+			home, strings.TrimPrefix(path, homePrefix))
+	}
+
+	if c.Paths.Root == "" {
+		return path, nil
+	}
+
+	if strings.HasPrefix(path, "$EVM_ROOT") {
+		path = filepath.Join(c.Paths.Root, path[9:])
+	} else if !filepath.IsAbs(path) {
+		path = filepath.Join(c.Paths.Root, path)
+	}
+
+	return path, nil
+}