bind/scan.go

package bind

import (
	"errors"
	"fmt"
	"math"
	"reflect"
	"strconv"
	"strings"
	"time"
)

var timeLayouts = []string{
	time.RFC3339,
	time.RFC3339Nano,
	time.DateTime,
	time.DateOnly,
	time.TimeOnly,
	time.RFC822,
	time.RFC822Z,
	time.RFC850,
	time.RFC1123,
	time.RFC1123Z,
	time.ANSIC,
	time.UnixDate,
	time.RubyDate,
	time.Kitchen,
	time.Layout,
	time.Stamp,
	time.StampMilli,
	time.StampMicro,
	time.StampNano,
}

func intParse[T any](parse func(string, int, int) (T, error), s string, byteSize int) (T, error) {
	bitSize := byteSize * 8
	switch {
	case strings.HasPrefix(s, "0b"):
		return parse(s[2:], 2, bitSize)
	case strings.HasPrefix(s, "0x"):
		return parse(s[2:], 16, bitSize)
	case strings.HasPrefix(s, "0"):
		return parse(s[1:], 8, bitSize)
	default:
		return parse(s, 10, bitSize)
	}
}

func parseInt(s string, byteSize int) (int64, error) {
	return intParse(strconv.ParseInt, s, byteSize)
}

func parseUint(s string, byteSize int) (uint64, error) {
	return intParse(strconv.ParseUint, s, byteSize)
}

func floatToTime(f float64) time.Time {
	s := int64(f)
	ns := int64((f - float64(s)) * 1_000_000_000)
	return time.Unix(s, ns)
}

func scanConvert(t reflect.Type, v any) (any, bool) {
	if isAny(t) {
		return v, true
	}

	r := reflect.ValueOf(v)
	if r.CanConvert(t) {
		return r.Convert(t).Interface(), true
	}

	if t != reflect.TypeFor[time.Time]() {
		return nil, false
	}

	fi := reflect.TypeFor[float64]()
	if !r.CanConvert(fi) {
		return nil, false
	}

	f := r.Convert(fi).Interface().(float64)
	return floatToTime(f), true
}

func parseTime(s string) (any, error) {
	const errMsg = "failed to parse time"
	for _, l := range timeLayouts {
		if t, err := time.Parse(l, s); err == nil {
			return t, nil
		}
	}

	ss := strings.Split(s, ".")
	if len(ss) > 2 {
		return nil, errors.New(errMsg)
	}

	if len(ss) == 1 {
		i, err := parseInt(ss[0], 8)
		if err != nil {
			return nil, errors.New(errMsg)
		}

		return time.Unix(i, 0), nil
	}

	sec, err := parseInt(ss[0], 8)
	if err != nil {
		return nil, errors.New(errMsg)
	}

	dec := strings.TrimLeft(ss[1], "0")
	i, err := parseInt(dec, 8)
	if err != nil {
		return nil, errors.New(errMsg)
	}

	zeros := len(ss[1]) - len(dec)
	nanosec := int64(float64(i) * math.Pow10(9-zeros-len(dec)))
	return time.Unix(sec, nanosec), nil
}

func scanString(t reflect.Type, s string) (any, bool) {
	var (
		v   any
		err error
	)

	switch t.Kind() {
	case reflect.Bool:
		v, err = strconv.ParseBool(s)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		if isDuration(t) {
			v, err = time.ParseDuration(s)
		}

		if !isDuration(t) || err != nil {
			v, err = parseInt(s, int(t.Size()))
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		v, err = parseUint(s, int(t.Size()))
	case reflect.Float32, reflect.Float64:
		v, err = strconv.ParseFloat(s, int(t.Size())*8)
	case reflect.String:
		v = s
	default:
		if isTime(t) {
			v, err = parseTime(s)
		} else {
			return nil, false
		}
	}

	if err != nil {
		return nil, false
	}

	p := reflect.New(t)
	p.Elem().Set(reflect.ValueOf(v).Convert(t))
	return p.Elem().Interface(), true
}

func scan(t reflect.Type, v any) (any, bool) {
	if vv, ok := scanConvert(t, v); ok {
		return vv, true
	}

	r := reflect.ValueOf(v)
	if r.Kind() != reflect.String {
		return nil, false
	}

	return scanString(t, fmt.Sprint(v))
}