feat: package manager state support (#19)

Fixes #18

pkgmgr/env.go

@@ -0,0 +1,5 @@
+package pkgmgr
+
+type Environment struct {
+	// TODO
+}

pkgmgr/pkgmgr.go

@@ -14,14 +14,30 @@
 
 package pkgmgr
 
+import (
+	"errors"
+	"fmt"
+)
+
+// ErrOperationFailed is a placeholder error for operations that directly log errors.
+// It's used to signify when an operation has failed when the actual error message is
+// sent through the provided logger
+var ErrOperationFailed = errors.New("the operation has failed")
+
 type PackageManager struct {
 	config Config
+	state  *State
 	// TODO
 }
 
 func NewPackageManager(cfg Config) (*PackageManager, error) {
+	// Make sure that a logger was provided, since we use it for pretty much all feedback
+	if cfg.Logger == nil {
+		return nil, errors.New("you must provide a logger")
+	}
 	p := &PackageManager{
 		config: cfg,
+		state:  NewState(cfg),
 	}
 	if err := p.init(); err != nil {
 		return nil, err
@@ -38,7 +54,13 @@ func NewDefaultPackageManager() (*PackageManager, error) {
 }
 
 func (p *PackageManager) init() error {
-	// TODO: create config/cache dirs
 	p.config.Logger.Debug("initializing package manager")
+	if err := p.state.Load(); err != nil {
+		return fmt.Errorf("failed to load state: %s", err)
+	}
+	// TODO: remove me
+	if err := p.state.Save(); err != nil {
+		return err
+	}
 	return nil
 }

pkgmgr/state.go

@@ -0,0 +1,92 @@
+package pkgmgr
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
+const (
+	environmentsFilename = "environments.json"
+)
+
+type State struct {
+	config       Config
+	Environments []Environment
+	// TODO: installed packages
+}
+
+func NewState(cfg Config) *State {
+	return &State{
+		config:       cfg,
+		Environments: make([]Environment, 0),
+	}
+}
+
+func (s *State) Load() error {
+	if err := s.loadEnvironments(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *State) Save() error {
+	if err := s.saveEnvironments(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *State) loadFile(filename string, dest any) error {
+	tmpPath := filepath.Join(
+		s.config.ConfigDir,
+		filename,
+	)
+	// Check if the file exists and we can access it
+	if _, err := os.Stat(tmpPath); err != nil {
+		// Treat no file like an empty file
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	content, err := os.ReadFile(tmpPath)
+	if err != nil {
+		return err
+	}
+	if err := json.Unmarshal(content, dest); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *State) saveFile(filename string, src any) error {
+	// Create parent directory if it doesn't exist
+	if _, err := os.Stat(s.config.ConfigDir); err != nil {
+		if os.IsNotExist(err) {
+			if err := os.MkdirAll(s.config.ConfigDir, os.ModePerm); err != nil {
+				return err
+			}
+		}
+	}
+	tmpPath := filepath.Join(
+		s.config.ConfigDir,
+		filename,
+	)
+	jsonContent, err := json.Marshal(src)
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(tmpPath, jsonContent, os.ModePerm); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *State) loadEnvironments() error {
+	return s.loadFile(environmentsFilename, &(s.Environments))
+}
+
+func (s *State) saveEnvironments() error {
+	return s.saveFile(environmentsFilename, &(s.Environments))
+}