Doc improvements (#6)

* add default datetime format, fix default format usage
* fixed format tests
* make reference time configurable
* improve doc

README.md

@@ -2,11 +2,137 @@
 
 generic cli timestamp parser and calculator tool
 
-## Usage
+## Introduction
+
+This little utility is a commandline frontent to the amazing datetime
+parser module [anytime](https://github.com/ijt/go-anytime). It uses
+two other modules as fallback if anytime might fail:
+[now](https://github.com/jinzhu/now) and
+[dateparse](github.com/araddon/dateparse).
+
+You can use it to print timestamps from plain english phrases like
+`next December 23rd AT 5:25 PM` or `two minutes from now`. In addition
+you can calculate the difference between two timestamps and you can
+add a duration to a timestamp.
+
+
+## Example Usage
+
+In these examples the current time is always **2025-09-17T07:30:00+01:00**.
+
+Show current date and time (same as `date`):
+```default
+% ts now
+Wed Sep 17 07:30:00 +0100 2025
+```
+
+show timestamp for minus 1 hour
+```default
+% ts "1 hour ago"
+Wed Sep 17 06:30:00 +0100 2025
+```
+
+... or from a couple days ago:
+```default
+% ts "4 days ago"
+Sat Sep 13 07:30:00 +0100 2025
+```
+There are much more ways to get timestamps, see `ts -e`.
+
+We  can  also add  times  to  timestamps, here  we  want  to know  the
+timestamp from now plus 10 days and 4 hours in the future:
+```default
+% ts -a now 10d4h
+Sat Sep 27 11:30:00 +0100 2025
+```
+
+It doesn't make a difference where you position the `-a` parameter:
+```default
+% ts now -a 10d4h
+Sat Sep 27 11:30:00 +0100 2025
+```
+Of course you can also calculate the difference between two
+dates. Here we have two timestamps (maybe we took them from a log
+file) and want to know the dime elapsed between them:
 
 ```default
-This is ts, a timestamp tool.
+% ts 2025-09-17T07:30:00+01:00 2025-09-15T12:45:00+01:00
+42h45m0s
+```
+As you can see, if you do not provide a parameter, the default is to
+calculate the difference between the two args. To explicitly calculate
+the difference, use the `-d` parameter.
 
+You can of course use english phrases for time differences as well:
+```default
+% ts "today 9 am" 2025-09-15T12:45:00+01:00
+44h15m0s
+```
+
+Lets talk a little bit about formatting. You may have already
+recognized, that `ts` prints either whole timestamps or
+durations. Both output types can be modified with the `-f`
+parameter. There are predefined formats for timestamps:
+
+```default
+% ts now 
+Wed Sep 17 07:30:00 +0100 2025
+% ts now -f rfc3339
+2025-09-17T07:30:00+01:00
+% ts now -f date
+2025-09-17
+% ts now -f unix
+1758090600
+```
+
+But you can also specify your own, you have to follow the [golang
+rules for timestamp formats](https://pkg.go.dev/time#Layout),
+basically:
+
+* Year: "2006" "06"
+* Month: "Jan" "January" "01" "1"
+* Day of the week: "Mon" "Monday"
+* Day of the month: "2" "_2" "02"
+* Day of the year: "__2" "002"
+* Hour: "15" "3" "03" (PM or AM)
+* Minute: "4" "04"
+* Second: "5" "05"
+* AM/PM mark: "PM"
+
+for example:
+```default
+% ts now -f "Mon, 02.January 2006"
+Wed, 17.September 2025
+```
+
+Ok I admit look is kinda weird, complaints go the the golang dev team
+:).
+
+Duration formatting is also customizable. By default a duration looks
+like we have seen above: `44h15m0s`. But sometimes we want to know the
+number of hours or minutes. Easy:
+
+```default
+% ts now 2025-09-15T12:45:00+01:00 -f hours
+42.75
+% ts now 2025-09-15T12:45:00+01:00 -f minutes
+2565.00
+```
+
+You may also add the `-u` parameter to have the unit shown as well:
+
+```default
+% ts now 2025-09-15T12:45:00+01:00 -f hours -u
+42.75 hours
+% ts now 2025-09-15T12:45:00+01:00 -f minutes -u
+2565.00 minutes
+```
+
+## Commandline parameters
+
+Here is the list of all supported parameters:
+
+```default
 Usage: ts <time string> [<time string>]
 -d --diff     Calculate difference between two timestamps (default).
 -a --add      Add two timestamps (second parameter must be a time).
@@ -21,31 +147,6 @@ Usage: ts <time string> [<time string>]
 -e --examples Show examples or supported inputs.
 ```
 
-## Examples
-
-```default
-# diff between to day and yesterday 10 am
-% date && ts today "10am yesterday"
-Wed Sep 24 02:05:03 PM CEST 2025
-14h0m0s
-
-# show timestamp from a couple days ago
-% date && ts "3 days ago"
-Wed Sep 24 02:04:42 PM CEST 2025
-2025-09-21 14:04:42.428910108 +0200 CEST
-
-# show timestamp of one hour and 45 minutes before (-d is the defaul)
-% date && ts -d now 1h45m
-Wed Sep 24 02:04:14 PM CEST 2025
-2025-09-24 12:19:14.932440045 +0200 CEST
-
-# 10 hours from now
-% date && ts --add now 10h 
-Wed Sep 24 02:03:31 PM CEST 2025
-2025-09-25 00:03:31.304518854 +0200 CEST
-```
-
-To see a comprehensive list of supported inputs, call `ts -e`.
 
 ## Installation
 

cmd/config.go

@@ -23,6 +23,7 @@ import (
 	"io"
 	"log"
 	"os"
+	"time"
 
 	"github.com/knadh/koanf/providers/posflag"
 	"github.com/knadh/koanf/v2"
@@ -31,7 +32,7 @@ import (
 )
 
 const (
-	VERSIONstring        = "0.0.3"
+	VERSIONstring        = "0.0.4"
 	Usage         string = `This is ts, a timestamp tool.
 
 Usage: ts <time string> [<time string>]
@@ -76,8 +77,11 @@ noon                   Yesterday at 10:15am                 Mon, 02 Jan 2006 15:
 Example durations for second parameter:
 2d1h30m  2 days, one and a half hour
 30m      30 minutes`
+
 	ModeDiff int = iota
 	ModeAdd
+
+	DefaultFormat string = "Mon Jan 02 15:04:05 MST 2006"
 )
 
 type Config struct {
@@ -92,7 +96,10 @@ type Config struct {
 	Args        []string
 	Output      io.Writer
 	Mode        int
-	TZ          string // for unit tests
+
+	// internal flags for [unit] tests
+	tz      string    // has to be set directly in code
+	refTime time.Time // must be set via env var $TSREFTIME
 }
 
 func InitConfig(output io.Writer) (*Config, error) {
@@ -127,11 +134,23 @@ func InitConfig(output io.Writer) (*Config, error) {
 	}
 
 	// fetch values
-	conf := &Config{Output: output}
+	conf := &Config{Output: output, refTime: time.Now()}
 	if err := kloader.Unmarshal("", &conf); err != nil {
 		return nil, fmt.Errorf("error unmarshalling: %w", err)
 	}
 
+	// check internal env var[s], if any
+	reftime, present := os.LookupEnv("TSREFTIME")
+	if present {
+		// e.g: 2014-01-03T00:00:00+01:00
+		ts, err := time.Parse(time.RFC3339Nano, reftime)
+		if err != nil {
+			os.Exit(Die("failed to set reference time from $TSREFTIME", err))
+		}
+
+		conf.refTime = ts
+	}
+
 	// want examples?
 	if conf.Examples {
 		_, err := fmt.Fprintln(output, Examples)

cmd/times.go

@@ -45,9 +45,10 @@ func NewTP(conf *Config, ref ...time.Time) *TimestampProccessor {
 
 	modnow.TimeFormats = append(modnow.TimeFormats, formats...)
 
-	tp := &TimestampProccessor{Config: *conf, Reference: time.Now()}
+	tp := &TimestampProccessor{Config: *conf, Reference: conf.refTime}
 
 	if len(ref) == 1 {
+		// overwritten externally by unit test
 		tp.Reference = ref[0]
 	}
 
@@ -73,9 +74,9 @@ func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
 		return ts, err
 	}
 
-	if tp.TZ != "" {
+	if tp.tz != "" {
 		// apply custom timezone
-		zone, _ := time.LoadLocation(tp.TZ)
+		zone, _ := time.LoadLocation(tp.tz)
 		ts = ts.In(zone)
 	}
 
@@ -105,7 +106,8 @@ func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
 		return err
 	}
 
-	tp.Print(ts)
+	tp.Print(TPdatetime{TimestampProccessor: *tp, Data: ts})
+	//tp.Print(ts)
 
 	return nil
 }

cmd/times_test.go

@@ -73,7 +73,7 @@ func TestParseTimestamps(t *testing.T) {
 		testname := fmt.Sprintf("parsetimestamp-%s", strings.ReplaceAll(tt.input, " ", "-"))
 		t.Run(testname, func(t *testing.T) {
 			var writer bytes.Buffer
-			tp := NewTP(&Config{Args: []string{tt.input}, Output: &writer, TZ: "UTC"}, now)
+			tp := NewTP(&Config{Args: []string{tt.input}, Output: &writer, tz: "UTC"}, now)
 
 			// writer.String()
 			ts, err := tp.Parse(tt.input)
@@ -82,7 +82,7 @@ func TestParseTimestamps(t *testing.T) {
 
 			err = tp.ProcessTimestamps()
 			assert.NoError(t, err)
-			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+			assert.EqualValues(t, tt.want.Format(DefaultFormat)+"\n", writer.String())
 		})
 	}
 }
@@ -148,7 +148,7 @@ func TestAddTimestamps(t *testing.T) {
 
 			err := tp.ProcessTimestamps()
 			assert.NoError(t, err)
-			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+			assert.EqualValues(t, tt.want.Format(DefaultFormat)+"\n", writer.String())
 		})
 	}
 }

cmd/writer.go

@@ -87,7 +87,7 @@ func (datetime TPdatetime) String() string {
 	case "datetime":
 		fallthrough
 	case "":
-		return datetime.Data.String()
+		return datetime.Data.Format(DefaultFormat)
 	default:
 		return datetime.Data.Format(datetime.Format)
 	}

cmd/writer_test.go

@@ -65,7 +65,7 @@ func TestDatetime(t *testing.T) {
 		{"date", now, "2025-09-25"},
 		{"time", now, "12:30:00"},
 		{"unix", now, "1758803400"},
-		{"datetime", now, "2025-09-25 12:30:00 +0000 UTC"},
+		{"datetime", now, "Thu Sep 25 12:30:00 UTC 2025"},
 	}
 
 	for _, tt := range tests {

t/simple.txtar

@@ -5,6 +5,6 @@ exec ts -e
 stdout 'yesterday'
 
 exec ts 3/1/2014
-stdout 2014-01-03
+stdout 'Fri Jan 03'