msgpack_ext: add string convertion for decimal datetime interval

CHANGELOG.md

@@ -137,6 +137,7 @@ includes some improvements to logging.
 - Implemented stringer methods for pool.Role (#405).
 - Support the IPROTO_INSERT_ARROW request (#399).
 - A simple implementation of using the box interface (#410).
+- Function String() for types datetime, interval, decimal (#322).
 
 ### Changed
 

datetime/datetime.go

@@ -350,6 +350,11 @@ func datetimeDecoder(d *msgpack.Decoder, v reflect.Value, extLen int) error {
 	return ptr.UnmarshalMsgpack(b)
 }
 
+// This method converts Datetime to String - formats to ISO8601.
+func (d Datetime) String() string {
+	return d.time.Format(time.RFC3339Nano)
+}
+
 func init() {
 	msgpack.RegisterExtDecoder(datetimeExtID, Datetime{}, datetimeDecoder)
 	msgpack.RegisterExtEncoder(datetimeExtID, Datetime{}, datetimeEncoder)

datetime/datetime_test.go

@@ -1174,6 +1174,23 @@ func runTestMain(m *testing.M) int {
 	return m.Run()
 }
 
+func TestDatetimeString(t *testing.T) {
+
+	tm, _ := time.Parse(time.RFC3339Nano, "2010-05-24T17:51:56.000000009Z")
+	dt, err := MakeDatetime(tm)
+	if err != nil {
+		t.Fatalf("Unable to create Datetime from %s: %s", tm, err)
+	}
+
+	result := dt.String()
+	t.Logf("Result: %s", result)
+
+	expected := "2010-05-24T17:51:56.000000009Z"
+	if result != expected {
+		t.Errorf("Expected %s, got %s", expected, result)
+	}
+
+}
 func TestMain(m *testing.M) {
 	code := runTestMain(m)
 	os.Exit(code)

datetime/example_test.go

@@ -161,7 +161,7 @@ func ExampleDatetime_Interval() {
 	ival := dtFirst.Interval(dtSecond)
 	fmt.Printf("%v", ival)
 	// Output:
-	// {2 2 0 -11 0 -1 0 0 0}
+	// 2 years, 2 months, -11 days and -1 minute
 }
 
 // ExampleDatetime_Add demonstrates how to add an Interval to a Datetime value.
@@ -278,7 +278,7 @@ func ExampleInterval_Add() {
 
 	fmt.Printf("%v", ival)
 	// Output:
-	// {11 2 3 0 0 30 10 0 1}
+	// 11 years, 2 months, 3 weeks, 30 minutes and 10 seconds
 }
 
 // ExampleInterval_Sub demonstrates how to subtract two intervals.
@@ -298,5 +298,5 @@ func ExampleInterval_Sub() {
 
 	fmt.Printf("%v", ival)
 	// Output:
-	// {-9 2 3 0 0 -30 10 0 1}
+	// -9 years, 2 months, 3 weeks, -30 minutes and 10 seconds
 }

datetime/interval.go

@@ -2,7 +2,9 @@ package datetime
 
 import (
 	"bytes"
+	"fmt"
 	"reflect"
+	"strings"
 
 	"github.com/vmihailenco/msgpack/v5"
 )
@@ -216,6 +218,85 @@ func decodeInterval(d *msgpack.Decoder, v reflect.Value) (err error) {
 	return nil
 }
 
+// Returns a human-readable string representation of the interval.
+func (ival Interval) String() string {
+	if ival.countNonZeroFields() == 0 {
+		return "0 seconds"
+	}
+
+	parts := make([]string, 0, 9)
+
+	// Helper function for adding components.
+	addPart := func(value int64, singular, plural string) {
+		if value == 0 {
+			return
+		}
+		if value == 1 || value == -1 {
+			parts = append(parts, fmt.Sprintf("%d %s", value, singular))
+		} else {
+			parts = append(parts, fmt.Sprintf("%d %s", value, plural))
+		}
+	}
+
+	addPart(ival.Year, "year", "years")
+	addPart(ival.Month, "month", "months")
+	addPart(ival.Week, "week", "weeks")
+	addPart(ival.Day, "day", "days")
+	addPart(ival.Hour, "hour", "hours")
+	addPart(ival.Min, "minute", "minutes")
+
+	// Processing seconds and nanoseconds - combine if both are present.
+	if ival.Sec != 0 && ival.Nsec != 0 {
+		// Define a common symbol for proper formatting.
+		secSign := ival.Sec < 0
+		nsecSign := ival.Nsec < 0
+
+		if secSign == nsecSign {
+			// Same signs - combine them.
+			absSec := ival.Sec
+			absNsec := ival.Nsec
+			if secSign {
+				absSec = -absSec
+				absNsec = -absNsec
+			}
+			parts = append(parts, fmt.Sprintf("%s%d.%09d seconds",
+				boolToSign(secSign), absSec, absNsec))
+		} else {
+			// Different characters - output separately.
+			addPart(ival.Sec, "second", "seconds")
+			addPart(ival.Nsec, "nanosecond", "nanoseconds")
+		}
+	} else {
+		// Only seconds or only nanoseconds.
+		addPart(ival.Sec, "second", "seconds")
+		addPart(ival.Nsec, "nanosecond", "nanoseconds")
+	}
+
+	return joinIntervalParts(parts)
+}
+
+// Returns "-" for true and an empty string for false.
+func boolToSign(negative bool) string {
+	if negative {
+		return "-"
+	}
+	return ""
+}
+
+// Combines parts of an interval into a readable string.
+func joinIntervalParts(parts []string) string {
+	switch len(parts) {
+	case 0:
+		return "0 seconds"
+	case 1:
+		return parts[0]
+	case 2:
+		return parts[0] + " and " + parts[1]
+	default:
+		return strings.Join(parts[:len(parts)-1], ", ") + " and " + parts[len(parts)-1]
+	}
+}
+
 func init() {
 	msgpack.RegisterExtEncoder(interval_extId, Interval{},
 		func(e *msgpack.Encoder, v reflect.Value) (ret []byte, err error) {

datetime/interval_test.go

@@ -133,3 +133,172 @@ func TestIntervalTarantoolEncoding(t *testing.T) {
 		})
 	}
 }
+
+func TestIntervalString(t *testing.T) {
+	tests := []struct {
+		name     string
+		interval Interval
+		expected string
+	}{
+		{
+			name:     "empty interval",
+			interval: Interval{},
+			expected: "0 seconds",
+		},
+		{
+			name: "single component - years",
+			interval: Interval{
+				Year: 1,
+			},
+			expected: "1 year",
+		},
+		{
+			name: "multiple years",
+			interval: Interval{
+				Year: 5,
+			},
+			expected: "5 years",
+		},
+		{
+			name: "multiple components",
+			interval: Interval{
+				Year:  1,
+				Month: 2,
+				Day:   3,
+			},
+			expected: "1 year, 2 months and 3 days",
+		},
+		{
+			name: "time components",
+			interval: Interval{
+				Hour: 1,
+				Min:  30,
+				Sec:  45,
+			},
+			expected: "1 hour, 30 minutes and 45 seconds",
+		},
+		{
+			name: "seconds with nanoseconds same sign",
+			interval: Interval{
+				Sec:  5,
+				Nsec: 123456789,
+			},
+			expected: "5.123456789 seconds",
+		},
+		{
+			name: "negative seconds with nanoseconds",
+			interval: Interval{
+				Sec:  -5,
+				Nsec: -123456789,
+			},
+			expected: "-5.123456789 seconds",
+		},
+		{
+			name: "seconds and nanoseconds different signs",
+			interval: Interval{
+				Sec:  5,
+				Nsec: -123456789,
+			},
+			expected: "5 seconds and -123456789 nanoseconds",
+		},
+		{
+			name: "only nanoseconds",
+			interval: Interval{
+				Nsec: 500000000,
+			},
+			expected: "500000000 nanoseconds",
+		},
+		{
+			name: "weeks",
+			interval: Interval{
+				Week: 2,
+			},
+			expected: "2 weeks",
+		},
+		{
+			name: "complex interval",
+			interval: Interval{
+				Year:  1,
+				Month: 6,
+				Week:  2,
+				Day:   3,
+				Hour:  12,
+				Min:   30,
+				Sec:   45,
+				Nsec:  123456789,
+			},
+			expected: "1 year, 6 months, 2 weeks, 3 days, 12 hours, 30 minutes " +
+				"and 45.123456789 seconds",
+		},
+		{
+			name: "negative components",
+			interval: Interval{
+				Year: -1,
+				Day:  -2,
+				Hour: -3,
+			},
+			expected: "-1 year, -2 days and -3 hours",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := tt.interval.String()
+			if result != tt.expected {
+				t.Errorf("Interval.String() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestIntervalStringIntegration(t *testing.T) {
+	t.Run("implements Stringer", func(t *testing.T) {
+		var _ fmt.Stringer = Interval{}
+	})
+
+	t.Run("works with fmt package", func(t *testing.T) {
+		ival := Interval{Hour: 2, Min: 30}
+		result := ival.String()
+		expected := "2 hours and 30 minutes"
+		if result != expected {
+			t.Errorf("fmt.Sprintf('%%s') = %v, want %v", result, expected)
+		}
+
+		result = fmt.Sprintf("%v", ival)
+		if result != expected {
+			t.Errorf("fmt.Sprintf('%%v') = %v, want %v", result, expected)
+		}
+	})
+}
+
+func TestIntervalStringEdgeCases(t *testing.T) {
+	tests := []struct {
+		name     string
+		interval Interval
+	}{
+		{
+			name:     "max values",
+			interval: Interval{Year: 1<<63 - 1, Month: 1<<63 - 1},
+		},
+		{
+			name:     "min values",
+			interval: Interval{Year: -1 << 63, Month: -1 << 63},
+		},
+		{
+			name:     "mixed signs complex",
+			interval: Interval{Year: 1, Month: -1, Day: 1, Hour: -1},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := tt.interval.String()
+			if result == "" {
+				t.Error("Interval.String() returned empty string")
+			}
+			if len(result) > 1000 { // Разумный лимит
+				t.Error("Interval.String() returned unexpectedly long string")
+			}
+		})
+	}
+}