ts/pkg/runexpr/run.go

package runexpr

import (
	"fmt"
	"time"

	"github.com/expr-lang/expr"
)

type Env struct {
	Now                                  func() time.Time
	Dur, D                               func(string) time.Duration
	Strf                                 func(any, ...any) string
	Diff                                 func(a, b time.Time) time.Duration
	Add                                  func(time.Time, time.Duration) time.Time
	Time, T                              func(string, ...string) time.Time
	Human                                func(time.Duration) string
	Years, Days, Hours, Minutes, Seconds func(time.Duration) float64
	Clock                                func(time.Time) string
	Unix                                 func(time.Time) int64
	TZ                                   func(time.Time, any) time.Time
}

func RunExpr(code string) {
	env := Env{
		Now:     time.Now,
		Dur:     parseDuration,
		D:       parseDuration,
		Strf:    strfTime,
		Diff:    timeDiff,
		Add:     timeAdd,
		Time:    newTime,
		T:       newTime,
		Human:   formatDuration,
		Years:   toYears,
		Days:    toDays,
		Hours:   toHours,
		Minutes: toMinutes,
		Seconds: toSeconds,
		Clock:   toClock,
		Unix:    toUnix,
		TZ:      toTZ,
	}

	options := []expr.Option{
		expr.Env(Env{}),
		expr.Operator("-", "Diff"), // custom operator to diff two time.Time's
		expr.Operator("+", "Add"),  // custom operator to add time.Duration to a time.Time
	}

	program, err := expr.Compile(code, options...)
	if err != nil {
		fmt.Printf("%v", err)
		return
	}

	output, err := expr.Run(program, env)
	if err != nil {
		panic(err)
	}

	fmt.Println(output)
}