// Copyright 2019 Yunion
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package tsdb

import (
	"fmt"
	"strconv"
	"strings"
	"time"
)

type TimeRange struct {
	From string
	To   string
	now  time.Time
}

func NewTimeRange(from, to string) *TimeRange {
	return &TimeRange{
		From: from,
		To:   to,
		now:  time.Now(),
	}
}

func TryParseUnixMsEpoch(val string) (time.Time, bool) {
	if val, err := strconv.ParseInt(val, 10, 64); err == nil {
		seconds := val / 1000
		nano := (val - seconds*1000) * 1000000
		return time.Unix(seconds, nano), true
	}
	return time.Time{}, false
}

func (tr *TimeRange) ParseFrom() (time.Time, error) {
	res, ok := TryParseUnixMsEpoch(tr.From)
	if ok {
		return res, nil
	}

	fromRaw := strings.Replace(tr.From, "now-", "", 1)
	diff, err := time.ParseDuration("-" + fromRaw)
	if err != nil {
		return time.Time{}, err
	}
	return tr.now.Add(diff), nil
}

func (tr *TimeRange) ParseTo() (time.Time, error) {
	if tr.To == "now" {
		return tr.now, nil
	} else if strings.HasPrefix(tr.To, "now-") {
		withoutNow := strings.Replace(tr.To, "now-", "", 1)

		diff, err := time.ParseDuration("-" + withoutNow)
		if err != nil {
			return time.Time{}, nil
		}

		return tr.now.Add(diff), nil
	}

	if res, ok := TryParseUnixMsEpoch(tr.To); ok {
		return res, nil
	}

	return time.Time{}, fmt.Errorf("cannot parse to value %s", tr.To)
}

func (tr *TimeRange) MustGetFrom() time.Time {
	res, err := tr.ParseFrom()
	if err != nil {
		return time.Unix(0, 0)
	}
	return res
}

func (tr *TimeRange) MustGetTo() time.Time {
	res, err := tr.ParseTo()
	if err != nil {
		return time.Unix(0, 0)
	}
	return res
}

func (tr *TimeRange) GetFromAsMsEpoch() int64 {
	return tr.MustGetFrom().UnixNano() / int64(time.Millisecond)
}

func (tr *TimeRange) GetFromAsSecondsEpoch() int64 {
	return tr.GetFromAsMsEpoch() / 1000
}

func (tr *TimeRange) GetFromAsTimeUTC() time.Time {
	return tr.MustGetFrom().UTC()
}

func (tr *TimeRange) GetToAsMsEpoch() int64 {
	return tr.MustGetTo().UnixNano() / int64(time.Millisecond)
}

func (tr *TimeRange) GetToAsSecondsEpoch() int64 {
	return tr.GetToAsMsEpoch() / 1000
}

func (tr *TimeRange) GetToAsTimeUTC() time.Time {
	return tr.MustGetTo().UTC()
}

// EpochPrecisionToMs converts epoch precision to millisecond, if needed.
// Only seconds to milliseconds supported right now
func EpochPrecisionToMs(value float64) float64 {
	s := strconv.FormatFloat(value, 'e', -1, 64)
	if strings.HasSuffix(s, "e+09") {
		return value * float64(1e3)
	}

	if strings.HasSuffix(s, "e+18") {
		return value / float64(time.Millisecond)
	}

	return value
}