package runexpr

import (
	"fmt"
	"log"
	"reflect"
	"regexp"
	"time"

	"github.com/lestrrat-go/strftime"
)

var (
	// matchDuration is  a regex  which matches  ES durations,  which
	// supports days (in contrast to time.Duration which does not)
	matchDuration = regexp.MustCompile(`(\d+)([ydhms])`)

	timeFormats = []string{
		time.RFC3339,
		time.RFC1123Z,
		time.RFC1123,
		time.RFC850,
		time.RFC822Z,
		time.RFC822,
		time.RubyDate,
		time.UnixDate,
		time.DateTime,
		time.DateOnly,
		time.TimeOnly,
		"02.01.2006 15:04:05", // german
		"02/01/2006 15:04:05",
		"20060102",
		"02.01.2006", // german
		"20060102150405",
		"15:04:05",
		"15:04",
	}
)

// setDefault#  either returns  the first  element  if item  if set  or
// replace. Types must match expect.
func setDefault(item []any, replace any, expect reflect.Type) any {
	if reflect.TypeOf(replace) != expect {
		log.Fatal("setDefault(): invalid types called")
	}

	if len(item) == 1 {
		return item[0]
	} else {
		return replace
	}
}

// strfTime formats a time.Time. Args are any,any to be able to use it in a pipe.
//
// eg:
//
//	now | strftime("%D")
//	strftime(now, "%D")
//	"%d.%m" | strftime(now)
func strfTime(fst any, snd ...any) string {
	var ts time.Time
	var format string

	switch firstVal := fst.(type) {
	case string:
		format = firstVal
		ts = setDefault(snd, time.Now(), reflect.TypeFor[time.Time]()).(time.Time)
	case time.Time:
		ts = firstVal
		format = setDefault(snd, "%D", reflect.TypeFor[string]()).(string)
	}

	if format == "" || ts.IsZero() {
		log.Fatal("strftime(): invalid args")
	}

	formatted, err := strftime.Format(format, ts)
	if err != nil {
		log.Fatal(err)
	}

	return formatted
}

// timeDiff  returns the  time.Duration diff  between time.Time  a and
// b. It syncs timezones first and exchanges a+b if a>b
func timeDiff(a, b time.Time) time.Duration {
	if a.Location() != b.Location() {
		b = b.In(a.Location())
	}

	if a.After(b) {
		a, b = b, a
	}

	return b.Sub(a)
}

// newTime returns  a new  tim.Time object  if ts  matches one  of the
// predefined formats. If format is set, use this.
func newTime(ts string, format ...string) time.Time {
	if len(format) > 0 {
		t, err := time.Parse(format[0], ts)
		if err == nil {
			return t
		}
	}
	for _, format := range timeFormats {
		t, err := time.Parse(format, ts)
		if err == nil {
			return t
		}
	}

	log.Fatal("new(): failed to parse timestamp")

	return time.Time{}
}

// toClock returns the HH:MM:SS time part of a time.Time
func toClock(t time.Time) string {
	h, m, s := t.Clock()
	return fmt.Sprintf("%02d:%02d:%02d", h, m, s)
}

// timeAdd adds d to t
func timeAdd(t time.Time, d time.Duration) time.Time {
	return t.Add(d)
}

// toUnix returns the epoch of t
func toUnix(t time.Time) int64 {
	return t.Unix()
}

// toTZ converts t to given time zone
func toTZ(t time.Time, tz any) time.Time {
	var z *time.Location
	var err error

	switch val := tz.(type) {
	case string:
		z, err = time.LoadLocation(val)
		if err != nil {
			log.Fatal(err)
		}

	case int:
		f := fmt.Sprintf("UTC+%d", val)
		if val < 0 {
			f = fmt.Sprintf("UTC%d", val)
		}

		z = time.FixedZone(f, val*60*60)
	}

	return t.In(z)
}