Adds expr functions

- modWeek returns modify week part of the date input
- random returns random number between range if given
- sub returns diff between two dates in milliseconds

pkg/expr/func_num.go

@@ -1,9 +1,10 @@
 package expr
 
 import (
-	"math"
-
 	"github.com/PaesslerAG/gval"
+	"github.com/pkg/errors"
+	"math"
+	"math/rand"
 )
 
 func NumericFunctions() []gval.Language {
@@ -19,6 +20,7 @@ func NumericFunctions() []gval.Language {
 		gval.Function("sqrt", math.Sqrt),
 		gval.Function("sum", sum),
 		gval.Function("average", average),
+		gval.Function("random", random),
 	}
 }
 
@@ -112,3 +114,30 @@ func average(v ...interface{}) float64 {
 
 	return sum / j
 }
+
+func random(v ...float64) (out float64, err error) {
+	var (
+		from, to  float64
+		totalArgs = len(v)
+	)
+
+	if totalArgs == 0 || totalArgs > 2 {
+		return 0, errors.Errorf("expecting 1 or 2 parameter, got %d", totalArgs)
+	}
+
+	if totalArgs > 0 {
+		if to = v[0]; to < 0 {
+			return 0, errors.New("unexpected input type of 1st parameter")
+		}
+	}
+
+	if totalArgs > 1 {
+		if to = v[1]; to < 0 {
+			return 0, errors.New("unexpected input type of 2nd parameter")
+		}
+		from = v[0]
+	}
+
+	out = from + rand.Float64()*(to-from)
+	return
+}

pkg/expr/func_num_test.go

@@ -76,3 +76,17 @@ func Example_average() {
 	// output:
 	// 4
 }
+
+func Example_randomWithSingleInput() {
+	eval(`max(random(6), 7)`, nil)
+
+	// output:
+	// 7
+}
+
+func Example_randomWithTwoInput() {
+	eval(`min(random(2, 6), 1)`, nil)
+
+	// output:
+	// 1
+}

pkg/expr/func_time.go

@@ -16,6 +16,7 @@ func TimeFunctions() []gval.Language {
 		gval.Function("parseISOTime", parseISOTime),
 		gval.Function("modTime", modTime),
 		gval.Function("modDate", modDate),
+		gval.Function("modWeek", modWeek),
 		gval.Function("modMonth", modMonth),
 		gval.Function("modYear", modYear),
 		gval.Function("parseDuration", time.ParseDuration),
@@ -23,6 +24,7 @@ func TimeFunctions() []gval.Language {
 		gval.Function("isLeapYear", isLeapYear),
 		gval.Function("now", now),
 		gval.Function("isWeekDay", isWeekDay),
+		gval.Function("sub", sub),
 	}
 }
 
@@ -131,6 +133,16 @@ func modDate(base interface{}, mod interface{}) (*time.Time, error) {
 	return &tmp, nil
 }
 
+func modWeek(base interface{}, mod interface{}) (*time.Time, error) {
+	t, m, err := prepMod(base, mod)
+	if err != nil {
+		return nil, err
+	}
+
+	tmp := t.AddDate(0, 0, 7*m)
+	return &tmp, nil
+}
+
 func modMonth(base interface{}, mod interface{}) (*time.Time, error) {
 	t, m, err := prepMod(base, mod)
 	if err != nil {
@@ -184,3 +196,26 @@ func strfTime(base interface{}, f string) (string, error) {
 	o, _ := strftime.Format(f, *t, strftime.WithMilliseconds('b'))
 	return o, nil
 }
+
+// sub returns difference between two date into milliseconds
+func sub(from interface{}, to interface{}) (out int64, err error) {
+	t1, _, err := prepMod(from, 0)
+	if err != nil {
+		return
+	}
+
+	t2, _, err := prepMod(to, 0)
+	if err != nil {
+		return
+	}
+
+	var duration time.Duration
+
+	if t1.After(*t2) {
+		duration = t1.Sub(*t2)
+	} else {
+		return -1, errors.New("expecting 2nd input to be less than 1st input")
+	}
+
+	return duration.Milliseconds(), nil
+}

pkg/expr/func_time_test.go

@@ -85,3 +85,52 @@ func Example_isWeekDay() {
 	// output:
 	// true
 }
+
+func Example_modTime() {
+	eval(`modTime(ghd, "+30m")`, exampleTimeParams)
+
+	// output:
+	// 1993-02-02 06:30:00 -0500 -0500
+}
+
+func Example_modWeek() {
+	eval(`modWeek(ghd, "1")`, exampleTimeParams)
+
+	// output:
+	// 1993-02-09 06:00:00 -0500 -0500
+}
+
+func Example_modDate() {
+	eval(`modDate(ghd, "5")`, exampleTimeParams)
+
+	// output:
+	// 1993-02-07 06:00:00 -0500 -0500
+}
+
+func Example_modMonth() {
+	eval(`modMonth(ghd, "1")`, exampleTimeParams)
+
+	// output:
+	// 1993-03-02 06:00:00 -0500 -0500
+}
+
+func Example_modYear() {
+	eval(`modYear(ghd, "5")`, exampleTimeParams)
+
+	// output:
+	// 1998-02-02 06:00:00 -0500 -0500
+}
+
+func Example_sub() {
+	eval(`sub(hgp, ghd)`, exampleTimeParams)
+
+	// output:
+	// 321627600000
+}
+
+func Example_subErrorCheck() {
+	eval(`sub(ghd, hgp)`, exampleTimeParams)
+
+	// output:
+	// error: can not evaluate sub(ghd, hgp): expecting 2nd input to be less than 1st input
+}