Relative time, fixes.

util/sql3util/arg.go

@@ -1,6 +1,9 @@
 package sql3util
 
-import "strings"
+import (
+	"strings"
+	"time"
+)
 
 // NamedArg splits an named arg into a key and value,
 // around an equals sign.
@@ -63,3 +66,115 @@ func ParseBool(s string) (b, ok bool) {
 	}
 	return false, false
 }
+
+// ParseTimeShift parses a time shift modifier,
+// also the output of timediff.
+//
+// https://sqlite.org/lang_datefunc.html
+func ParseTimeShift(s string) (years, months, days int, duration time.Duration, ok bool) {
+	// Sign part: ±
+	neg := strings.HasPrefix(s, "-")
+	sign := neg || strings.HasPrefix(s, "+")
+	if sign {
+		s = s[1:]
+	}
+
+	if ok = len(s) >= 5; !ok {
+		return // !ok
+	}
+
+	defer func() {
+		if neg {
+			years = -years
+			months = -months
+			days = -days
+			duration = -duration
+		}
+	}()
+
+	// Date part: YYYY-MM-DD
+	if s[4] == '-' {
+		if ok = sign && len(s) >= 10 && s[7] == '-'; !ok {
+			return // !ok
+		}
+		if years, ok = parseInt(s[0:4]); !ok {
+			return // !ok
+		}
+		if months, ok = parseInt(s[5:7]); !ok {
+			return // !ok
+		}
+		if days, ok = parseInt(s[8:10]); !ok {
+			return // !ok
+		}
+		if len(s) == 10 {
+			return
+		}
+		if ok = s[10] == ' '; !ok {
+			return // !ok
+		}
+		s = s[11:]
+	}
+
+	// Time part: HH:MM
+	if ok = len(s) >= 5 && s[2] == ':'; !ok {
+		return // !ok
+	}
+
+	var hours, minutes int
+	if hours, ok = parseInt(s[0:2]); !ok {
+		return
+	}
+	if minutes, ok = parseInt(s[3:5]); !ok {
+		return
+	}
+	duration = time.Duration(hours)*time.Hour + time.Duration(minutes)*time.Minute
+
+	if len(s) == 5 {
+		return
+	}
+	if ok = len(s) >= 8 && s[5] == ':'; !ok {
+		return // !ok
+	}
+
+	// Seconds part: HH:MM:SS
+	var seconds int
+	if seconds, ok = parseInt(s[6:8]); !ok {
+		return
+	}
+	duration += time.Duration(seconds) * time.Second
+
+	if len(s) == 8 {
+		return
+	}
+	if ok = len(s) >= 10 && s[8] == '.'; !ok {
+		return // !ok
+	}
+	s = s[9:]
+
+	// Nanosecond part: HH:MM:SS.SSS
+	var nanos int
+	if nanos, ok = parseInt(s[0:min(9, len(s))]); !ok {
+		return
+	}
+	for i := len(s); i < 9; i++ {
+		nanos *= 10
+	}
+	duration += time.Duration(nanos)
+
+	// Subnanosecond part.
+	if len(s) > 9 {
+		_, ok = parseInt(s[9:])
+	}
+	return
+}
+
+func parseInt(s string) (i int, _ bool) {
+	for _, r := range []byte(s) {
+		r -= '0'
+		if r > 9 {
+			return
+		}
+		i = i*10 + int(r)
+	}
+	return i, true
+}

util/sql3util/arg_test.go

@@ -2,6 +2,7 @@ package sql3util_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/ncruces/go-sqlite3/util/sql3util"
 )
@@ -53,3 +54,43 @@ func TestParseBool(t *testing.T) {
 		})
 	}
 }
+
+func TestParseTimeShift(t *testing.T) {
+	epoch := time.Unix(0, 0)
+	tests := []struct {
+		str string
+		val time.Time
+		ok  bool
+	}{
+		{"", epoch, false},
+		{"0001-12-30", epoch, false},
+		{"+_001-12-30", epoch, false},
+		{"+0001-_2-30", epoch.AddDate(1, 0, 0), false},
+		{"+0001-12-_0", epoch.AddDate(1, 12, 0), false},
+		{"+0001-12-30", epoch.AddDate(1, 12, 30), true},
+		{"-0001-12-30", epoch.AddDate(-1, -12, -30), true},
+		{"+0001-12-30T", epoch.AddDate(1, 12, 30), false},
+		{"+0001-12-30 12", epoch.AddDate(1, 12, 30), false},
+		{"+0001-12-30 _2:30", epoch.AddDate(1, 12, 30), false},
+		{"+0001-12-30 12:_0", epoch.AddDate(1, 12, 30), false},
+		{"+0001-12-30 12:30", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 30*time.Minute), true},
+		{"+0001-12-30 12:30:", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 30*time.Minute), false},
+		{"+0001-12-30 12:30:_0", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 30*time.Minute), false},
+		{"+0001-12-30 12:30:60", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute), true},
+		{"+0001-12-30 12:30:60.", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute), false},
+		{"+0001-12-30 12:30:60._", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute), false},
+		{"+0001-12-30 12:30:60.1", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute + 100*time.Millisecond), true},
+		{"+0001-12-30 12:30:60.123456789_", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute + 123456789), false},
+		{"+0001-12-30 12:30:60.1234567890", epoch.AddDate(1, 12, 30).Add(12*time.Hour + 31*time.Minute + 123456789), true},
+		{"-12:30:60.1234567890", epoch.Add(-12*time.Hour - 31*time.Minute - 123456789), true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.str, func(t *testing.T) {
+			years, months, days, duration, gotOK := sql3util.ParseTimeShift(tt.str)
+			gotVal := epoch.AddDate(years, months, days).Add(duration)
+			if !gotVal.Equal(tt.val) || gotOK != tt.ok {
+				t.Errorf("ParseTimeShift(%q) = (%v, %v) want (%v, %v)", tt.str, gotVal, gotOK, tt.val, tt.ok)
+			}
+		})
+	}
+}