Parse TZ_LIST env. var to show zones

config.go

@@ -16,15 +16,55 @@
  **/
 package main
 
+import (
+	"fmt"
+	"os"
+	"strings"
+	"time"
+)
+
 // Config stores app configuration
 type Config struct {
 	Zones []Zone
 }
 
 // LoadConfig from os.UserConfigDir
 func LoadConfig() (*Config, error) {
-	cfg := Config{
+	conf := Config{
 		Zones: DefaultZones,
 	}
-	return &cfg, nil
+
+	zoneEnv := os.Getenv("TZ_LIST")
+	if zoneEnv == "" {
+		return &conf, nil
+	}
+	zoneNames := strings.Split(zoneEnv, ",")
+	if len(zoneNames) == 0 {
+		return &conf, nil
+	}
+	zones := make([]Zone, len(zoneNames)+1)
+
+	now := time.Now()
+	localZoneName, offset := now.Zone()
+
+	zones[0] = Zone{
+		Name:   fmt.Sprintf("(%s) Local", localZoneName),
+		DbName: localZoneName,
+		Offset: offset / 3600,
+	}
+	for i, name := range zoneNames {
+		loc, err := time.LoadLocation(name)
+		if err != nil {
+			return nil, fmt.Errorf("looking up zone %s: %w", name, err)
+		}
+		then := now.In(loc)
+		shortName, offset := then.Zone()
+		zones[i+1] = Zone{
+			DbName: loc.String(),
+			Name:   fmt.Sprintf("(%s) %s", shortName, loc),
+			Offset: offset / 3600,
+		}
+	}
+	conf.Zones = zones
+	return &conf, nil
 }

main.go

@@ -72,7 +72,7 @@ func (m model) View() string {
 		hours := strings.Builder{}
 		startAt := 0
 		if zi > 0 {
-			startAt = (z.offset - m.zones[0].offset) % 24
+			startAt = (z.Offset - m.zones[0].Offset) % 24
 		}
 
 		// A list of hours
@@ -125,7 +125,7 @@ func main() {
 	now := time.Now()
 	config, err := LoadConfig()
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error loading config: %s", err)
+		fmt.Fprintf(os.Stderr, "Config error: %s\n", err)
 		os.Exit(2)
 	}
 	var initialModel = model{

zone.go

@@ -21,24 +21,14 @@ import "time"
 var name, offset = time.Now().Zone()
 var DefaultZones = []Zone{
 	{
-		name:   "Local",
-		dbName: name,
-		offset: offset / 3600,
+		Name:   "Local",
+		DbName: name,
+		Offset: offset / 3600,
 	},
 	{
-		name:   "Paris",
-		dbName: "Europe/Paris",
-		offset: 1,
-	},
-	{
-		name:   "New-York",
-		dbName: "America/New_York",
-		offset: -5,
-	},
-	{
-		name:   "UTC",
-		dbName: "UTC",
-		offset: 0,
+		Name:   "UTC",
+		DbName: "UTC",
+		Offset: 0,
 	},
 }
 
@@ -60,13 +50,13 @@ var EmojiClocks = map[int]string{
 
 // Zone stores the name of a time zone and its integer offset from UTC.
 type Zone struct {
-	dbName string // tz db name
-	name   string // custom name
-	offset int    // Integer offset from UTC
+	DbName string // Name in tzdata
+	Name   string // Short name
+	Offset int    // Integer offset from UTC, in hours.
 }
 
 func (z Zone) String() string {
-	return z.name
+	return z.Name
 }
 
 // ClockEmoji returns the corresponding emoji clock for a given hour
@@ -83,8 +73,8 @@ func (z Zone) ShortDT() string {
 func (z Zone) currentTime() time.Time {
 	now := time.Now()
 	zName, _ := now.Zone()
-	if z.dbName != zName {
-		loc, err := time.LoadLocation(z.dbName)
+	if z.DbName != zName {
+		loc, err := time.LoadLocation(z.DbName)
 		if err != nil {
 			return now
 		}