Postgres interval with date/time expression arithmetic.

postgres/interval.go

@@ -0,0 +1,131 @@
+package postgres
+
+import (
+	"fmt"
+	"github.com/go-jet/jet/internal/jet"
+	"github.com/go-jet/jet/internal/utils"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type quantityAndUnit float64
+
+const (
+	pow2_32 = -4.294967296e+09
+
+	YEAR quantityAndUnit = pow2_32 + iota
+	MONTH
+	WEEK
+	DAY
+	HOUR
+	MINUTE
+	SECOND
+	MILLISECOND
+	MICROSECOND
+	DECADE
+	CENTURY
+	MILLENNIUM
+)
+
+type intervalExpressionImpl struct {
+	jet.Interval
+	jet.ExpressionInterfaceImpl
+}
+
+type IntervalExpression interface {
+	jet.IsInterval
+	jet.Expression
+}
+
+func INTERVAL(quantityAndUnit ...quantityAndUnit) IntervalExpression {
+	if len(quantityAndUnit)%2 != 0 {
+		panic("jet: invalid number of quantity and unit fields")
+	}
+
+	fields := []string{}
+
+	for i := 0; i < len(quantityAndUnit); i += 2 {
+		quantity := strconv.FormatFloat(float64(quantityAndUnit[i]), 'f', -1, 64)
+		unitString := unitToString(quantityAndUnit[i+1])
+		fields = append(fields, quantity+" "+unitString)
+	}
+
+	intervalStr := fmt.Sprintf("'%s'", strings.Join(fields, " "))
+
+	newInterval := &intervalExpressionImpl{
+		Interval: jet.NewInterval(jet.Raw(intervalStr)),
+	}
+
+	newInterval.ExpressionInterfaceImpl.Parent = newInterval
+
+	return newInterval
+}
+
+func INTERVALd(duration time.Duration) IntervalExpression {
+	days, hours, minutes, seconds, microseconds := utils.ExtractDateTimeComponents(duration)
+
+	quantityAndUnits := []quantityAndUnit{}
+
+	if days > 0 {
+		quantityAndUnits = append(quantityAndUnits, quantityAndUnit(days))
+		quantityAndUnits = append(quantityAndUnits, DAY)
+	}
+
+	if hours > 0 {
+		quantityAndUnits = append(quantityAndUnits, quantityAndUnit(hours))
+		quantityAndUnits = append(quantityAndUnits, HOUR)
+	}
+
+	if minutes > 0 {
+		quantityAndUnits = append(quantityAndUnits, quantityAndUnit(minutes))
+		quantityAndUnits = append(quantityAndUnits, MINUTE)
+	}
+
+	if seconds > 0 {
+		quantityAndUnits = append(quantityAndUnits, quantityAndUnit(seconds))
+		quantityAndUnits = append(quantityAndUnits, SECOND)
+	}
+
+	if microseconds > 0 {
+		quantityAndUnits = append(quantityAndUnits, quantityAndUnit(microseconds))
+		quantityAndUnits = append(quantityAndUnits, MICROSECOND)
+	}
+
+	if len(quantityAndUnits) == 0 {
+		return INTERVAL(0, MICROSECOND)
+	}
+
+	return INTERVAL(quantityAndUnits...)
+}
+
+func unitToString(unit quantityAndUnit) string {
+	switch unit {
+	case YEAR:
+		return "YEAR"
+	case MONTH:
+		return "MONTH"
+	case WEEK:
+		return "WEEK"
+	case DAY:
+		return "DAY"
+	case HOUR:
+		return "HOUR"
+	case MINUTE:
+		return "MINUTE"
+	case SECOND:
+		return "SECOND"
+	case MILLISECOND:
+		return "MILLISECOND"
+	case MICROSECOND:
+		return "MICROSECOND"
+	case DECADE:
+		return "DECADE"
+	case CENTURY:
+		return "CENTURY"
+	case MILLENNIUM:
+		return "MILLENNIUM"
+	default:
+		panic("jet: invalid INTERVAL unit type")
+	}
+}