forked from dolthub/go-mysql-server
/
convert_tz.go
219 lines (177 loc) · 5.85 KB
/
convert_tz.go
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// Copyright 2021 Dolthub, Inc.
//
// 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 function
import (
"errors"
"fmt"
"math"
"regexp"
"time"
"github.com/gabereiser/go-mysql-server/sql"
"github.com/gabereiser/go-mysql-server/sql/types"
)
var offsetRegex = regexp.MustCompile(`(?m)^([+\-])(\d{2}):(\d{2})$`) // (?m)^\+|\-(\d{2}):(\d{2})$
type ConvertTz struct {
dt sql.Expression
fromTz sql.Expression
toTz sql.Expression
}
var _ sql.FunctionExpression = (*ConvertTz)(nil)
// NewConvertTz returns an implementation of the CONVERT_TZ() function.
func NewConvertTz(dt, fromTz, toTz sql.Expression) sql.Expression {
return &ConvertTz{
dt: dt,
fromTz: fromTz,
toTz: toTz,
}
}
// FunctionName implements sql.FunctionExpression
func (c *ConvertTz) FunctionName() string {
return "convert_tz"
}
// Description implements the sql.FunctionExpression interface.
func (c *ConvertTz) Description() string {
return "converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value."
}
// Resolved implements the sql.Expression interface.
func (c *ConvertTz) Resolved() bool {
return c.dt.Resolved() && c.fromTz.Resolved() && c.toTz.Resolved()
}
// String implements the sql.Expression interface.
func (c *ConvertTz) String() string {
return fmt.Sprintf("%s(%s,%s,%s)", c.FunctionName(), c.dt, c.fromTz, c.toTz)
}
// Type implements the sql.Expression interface.
func (c *ConvertTz) Type() sql.Type {
return types.Datetime
}
// IsNullable implements the sql.Expression interface.
func (c *ConvertTz) IsNullable() bool {
return true
}
// Eval implements the sql.Expression interface.
func (c *ConvertTz) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
from, err := c.fromTz.Eval(ctx, row)
if err != nil {
return nil, err
}
to, err := c.toTz.Eval(ctx, row)
if err != nil {
return nil, err
}
dt, err := c.dt.Eval(ctx, row)
if err != nil {
return nil, err
}
// If either the date, or the timezones/offsets are not correct types we return NULL.
datetime, err := types.Datetime.ConvertWithoutRangeCheck(dt)
if err != nil {
return nil, nil
}
globalTimeZone, _, _ := sql.SystemVariables.GetGlobal("time_zone")
fromStr, ok := from.(string)
if !ok {
return nil, nil
}
t := time.Now()
_, offset := t.Zone()
if fromStr == globalTimeZone.Default {
fromStr = getSystemDelta(offset)
}
toStr, ok := to.(string)
if !ok {
return nil, nil
}
if toStr == globalTimeZone.Default {
toStr = getSystemDelta(offset)
}
converted, success := convertTimeZone(datetime, fromStr, toStr)
if success {
return types.Datetime.ConvertWithoutRangeCheck(converted)
}
// If we weren't successful converting by timezone try converting via offsets.
converted, success = convertOffsets(datetime, fromStr, toStr)
if !success {
return nil, nil
}
return types.Datetime.ConvertWithoutRangeCheck(converted)
}
// convertTimeZone returns the conversion of t from timezone fromLocation to toLocation.
func convertTimeZone(datetime time.Time, fromLocation string, toLocation string) (time.Time, bool) {
fLoc, err := time.LoadLocation(fromLocation)
if err != nil {
return time.Time{}, false
}
tLoc, err := time.LoadLocation(toLocation)
if err != nil {
return time.Time{}, false
}
delta := getCopy(datetime, fLoc).Sub(getCopy(datetime, tLoc))
return datetime.Add(delta), true
}
// getCopy recreates the time t in the wanted timezone.
func getCopy(t time.Time, loc *time.Location) time.Time {
return time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), loc).UTC()
}
// convertOffsets returns the conversion of t to t + (endDuration - startDuration) and a boolean indicating success.
func convertOffsets(t time.Time, startDuration string, endDuration string) (time.Time, bool) {
fromDuration, err := getDeltaAsDuration(startDuration)
if err != nil {
return time.Time{}, false
}
toDuration, err := getDeltaAsDuration(endDuration)
if err != nil {
return time.Time{}, false
}
return t.Add(toDuration - fromDuration), true
}
// getDeltaAsDuration takes in a MySQL offset in the format (ex +01:00) and returns it as a time Duration.
func getDeltaAsDuration(d string) (time.Duration, error) {
var hours string
var mins string
var symbol string
matches := offsetRegex.FindStringSubmatch(d)
if len(matches) == 4 {
symbol = matches[1]
hours = matches[2]
mins = matches[3]
} else {
return -1, errors.New("error: unable to process time")
}
return time.ParseDuration(symbol + hours + "h" + mins + "m")
}
func getSystemDelta(offset int) string {
seconds := offset % (60 * 60 * 24)
hours := math.Floor(float64(seconds) / 60 / 60)
seconds = offset % (60 * 60)
minutes := math.Floor(float64(seconds) / 60)
result := fmt.Sprintf("%02d:%02d", int(math.Abs(hours)), int(math.Abs(minutes)))
if offset >= 0 {
result = fmt.Sprintf("+%s", result)
} else {
result = fmt.Sprintf("-%s", result)
}
return result
}
// Children implements the sql.Expression interface.
func (c *ConvertTz) Children() []sql.Expression {
return []sql.Expression{c.dt, c.fromTz, c.toTz}
}
// WithChildren implements the sql.Expression interface.
func (c *ConvertTz) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 3 {
return nil, sql.ErrInvalidChildrenNumber.New(c, len(children), 3)
}
return NewConvertTz(children[0], children[1], children[2]), nil
}