webtools/cmds/timestamps/input.go

package main

import (
	"time"

	"github.com/alecthomas/participle/v2"
	"github.com/alecthomas/participle/v2/lexer"
)

var basicLexer = lexer.MustSimple([]lexer.SimpleRule{
	{"Identifier", `[a-z][a-zA-Z0-9_]*`},
	{"Date", `\d{4}-\d{2}-\d{2}`},
	{"Time", `\d{2}:\d{2}:\d{2}`},
	{"Int", `\d+`},
	{"T", `T`},
	{"Z", `Z`},
	{"Whitespace", `[ ]+`},
})

var parser = participle.MustBuild[Atom](
	participle.Lexer(basicLexer),
	participle.Elide("Whitespace"),
	participle.UseLookahead(2),
)

func Parse(expr string) (TimeResult, error) {
	res, err := parser.ParseString("expr", expr)
	if err != nil {
		return nil, err
	}
	return res, nil
}

type TimeResult interface {
	Time() (time.Time, error)
	RequiresRefreshing() bool
}