first commit

2025-11-25 21:10:31 -05:00
commit c145062ff0
5 changed files with 434 additions and 0 deletions
@@ -0,0 +1,163 @@
+package settings
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	MaintenanceRoutinePace = time.Second
+	WarnIfFileNotFound     = false
+)
+
+type Settings struct {
+	mutex      sync.RWMutex
+	contents   map[string]string
+	filename   string
+	modtime    time.Time
+	LogUpdates atomic.Bool
+}
+
+func (s *Settings) GetFilename() string {
+	s.mutex.RLock()
+	defer s.mutex.RUnlock()
+	return s.filename
+}
+
+func (s *Settings) SetFilename(filename string) (updated bool) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	if filename == s.filename {
+		return false
+	}
+	if s.LogUpdates.Load() {
+		log.Printf("Settings::SetFilename changing from '%s' to '%s'\n", s.filename, filename)
+	}
+	s.filename = strings.Clone(filename)
+	s.modtime = time.Time{}
+	err := s.lockedUpdate()
+	if err != nil {
+		if !errors.Is(err, os.ErrNotExist) || WarnIfFileNotFound {
+			log.Printf("Settings::SetFilename %s: error from lockedUpdate: %v\n", filepath.Base(s.filename), err)
+		}
+	}
+	return true
+}
+
+func (s *Settings) lockedSetKeyValue(key, value string) bool {
+	logUpdates := s.LogUpdates.Load()
+	baseFilename := filepath.Base(s.filename)
+	if stored, found := s.contents[key]; found && stored == value {
+		return false
+	} else if found && logUpdates {
+		log.Printf("Settings::lockedKeyValue %s: updating key '%s' from value '%s' to '%s'\n", baseFilename, key, stored, value)
+	} else if !found && logUpdates {
+		log.Printf("Settings::lockedKeyValue %s: storing key '%s' with value '%s'\n", baseFilename, key, value)
+	}
+	s.contents[strings.Clone(key)] = strings.Clone(value)
+	return true
+}
+
+func (s *Settings) SetKeyValue(key, value string) (updated bool) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.lockedSetKeyValue(key, value)
+}
+
+func (s *Settings) lockedContainsKey(key string) bool {
+	_, found := s.contents[key]
+	return found
+}
+
+func (s *Settings) ContainsKey(key string) bool {
+	s.mutex.RLock()
+	defer s.mutex.RUnlock()
+	return s.lockedContainsKey(key)
+}
+
+func (s *Settings) lockedGetKeyValue(key string) string {
+	return s.contents[key]
+}
+
+func (s *Settings) GetKeyValue(key string) string {
+	s.mutex.RLock()
+	defer s.mutex.RUnlock()
+	return s.lockedGetKeyValue(key)
+}
+
+func (s *Settings) lockedUpdate() error {
+	stat, err := os.Stat(s.filename)
+	if err != nil {
+		return fmt.Errorf("error getting os.FileInfo for %s: %w", s.filename, err)
+	} else if !stat.ModTime().After(s.modtime) {
+		return nil
+	}
+	contents, err := os.ReadFile(s.filename)
+	if err != nil {
+		return fmt.Errorf("error reading %s: %w", s.filename, err)
+	}
+	scanner := NewScanner(bytes.NewReader(contents))
+loop:
+	for {
+		key, value, err := scanner.ReadNextLine()
+		if err != nil {
+			if !errors.Is(err, io.EOF) {
+				log.Printf("error from scanner.ReadNextLine: %v\n", err)
+			} else {
+				break loop
+			}
+		}
+		s.lockedSetKeyValue(key, value)
+	}
+	s.modtime = stat.ModTime()
+	return nil
+}
+
+func (s *Settings) Update() error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.lockedUpdate()
+}
+
+func (s *Settings) maintenanceRoutine(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(MaintenanceRoutinePace):
+			err := s.Update()
+			if err != nil {
+				if !errors.Is(err, os.ErrNotExist) || WarnIfFileNotFound {
+					log.Printf("Settings::maintenanceRoutine %s error from Update: %v\n", filepath.Base(s.GetFilename()), err)
+				}
+			}
+		}
+	}
+}
+
+func NewSettings(filename string, logUpdates bool) *Settings {
+	return NewSettingsWithContext(context.Background(), filename, logUpdates)
+}
+
+func NewSettingsWithContext(ctx context.Context, filename string, logUpdates bool) *Settings {
+	settings := &Settings{
+		contents: make(map[string]string),
+		filename: strings.Clone(filename),
+	}
+	settings.LogUpdates.Store(logUpdates)
+	if err := settings.lockedUpdate(); err != nil {
+		log.Printf("NewSettingsWithContext %s error from initial update: %v\n", filepath.Base(filename), err)
+	}
+	go settings.maintenanceRoutine(ctx)
+	return settings
+}