dbx/utility.go

package dbx

import (
	"fmt"
	"reflect"
	"strings"
	"time"

	"github.com/go-jet/jet/v2/mysql"
	"golang.org/x/exp/constraints"
)

// StringToFilter processes a string to be used as a filter in an SQL LIKE
// statement. It replaces all spaces with % and adds % to the beginning and
// end of the string.
func StringToFilter(str string) string {
	// Remove any existing leading or trailing % characters
	str = strings.Trim(str, "%")

	// Replace all spaces with % and add % to the beginning and end of the string
	str = strings.ReplaceAll(str, " ", "%")
	str = "%" + str + "%"

	return str
}

// ExprValues converts a list of values to a list of mysql.Expression values using
// function f to transform the values (mysql.String for strings, mysql.Uint64, etc).
func ExprValues[T any](values []T, f func(T) mysql.Expression) []mysql.Expression {
	expressions := make([]mysql.Expression, len(values))
	for i, v := range values {
		expressions[i] = f(v)
	}
	return expressions
}

// ExprStringers converts a list of fmt.Stringers to a list of mysql.Expression values.
func ExprStringers(values []fmt.Stringer) []mysql.Expression {
	expressions := make([]mysql.Expression, len(values))
	for i, v := range values {
		expressions[i] = mysql.String(v.String())
	}
	return expressions
}

// NowPtr returns a pointer to the current time.
func NowPtr() *time.Time {
	now := time.Now()
	return &now
}

// Ptr returns a pointer to the given value of any scalar type. Returns nil if the value is a zero value.
func Ptr[T any](val T) *T {
	if reflect.ValueOf(val).IsZero() {
		return nil
	}
	return &val
}

// Val returns the value of the pointer to a scalar type, or the zero value if the pointer is nil.
func Val[T any](ptr *T) T {
	if ptr == nil {
		var zero T
		return zero
	}
	return *ptr
}

// TrimPtr trims the whitespace from a pointer to a string and returns nil only if the pointer is nil.
func TrimPtr(s *string) *string {
	if s == nil {
		return nil
	}
	trimmed := strings.TrimSpace(*s)
	return &trimmed
}

// TrimPtrToNil trims the whitespace from a pointer to a string and returns nil
// if the resulting string is empty or if the pointer is nil.
func TrimPtrToNil(s *string) *string {
	if s == nil {
		return nil
	}
	trimmed := strings.TrimSpace(*s)
	if trimmed == "" {
		return nil
	}
	return &trimmed
}

// IsZero checks if a pointer references the zero value of a given type and
// returns an error if this condition is met, otherwise returns nil if the
// pointer is nil or the value is not zero.
func IsZero[T any](ptr *T) error {
	if ptr == nil {
		return nil
	}
	if reflect.ValueOf(*ptr).IsZero() {
		return ErrValueIsZero
	}
	return nil
}

// ApplyPtr compares the existing value with a new value and returns the updated value if they differ.
// If the new value is nil, the existing value is retained. If the new value is a zero-value, the
// existing value is NOT retained, it will be set to nil. If the value is changed, targetColumn is pushed
// to updatedColumns.
func ApplyPtr[T constraints.Float | constraints.Integer | string | bool](
	existing *T,
	newVal *T,
	updatedColumns *mysql.ColumnList,
	targetColumn mysql.Column,
) *T {
	if newVal == nil {
		return existing
	}
	if reflect.ValueOf(*newVal).IsZero() {
		newVal = nil
	}
	if newVal == nil && existing == nil || newVal != nil && existing != nil && *existing == *newVal {
		return existing
	}
	*updatedColumns = append(*updatedColumns, targetColumn)
	return newVal
}

// ApplyComplexPtr compares the existing value with a new value and returns the updated value if they differ.
// The new value may be of a different type (e.g. existing is uint16 and new is uint64), but it will be
// converted to match the current type resulting in potential loss of data. If the new value is nil, the
// existing value is retained. If the new value is a zero-value, the existing value is NOT retained, it
// will be set to nil. If the value is changed, targetColumn is pushed to updatedColumns.
func ApplyComplexPtr[
	Existing constraints.Float | constraints.Integer,
	New constraints.Float | constraints.Integer,
](
	existing *Existing,
	newVal *New,
	updatedColumns *mysql.ColumnList,
	targetColumn mysql.Column,
) *Existing {
	if newVal == nil {
		return existing
	}
	cast := Existing(*newVal) // Convert new value to existing type
	if existing != nil && *existing == cast {
		return existing
	}
	if reflect.ValueOf(cast).IsZero() {
		if existing != nil {
			*updatedColumns = append(*updatedColumns, targetColumn)
		}
		return nil
	} else {
		*updatedColumns = append(*updatedColumns, targetColumn)
		return &cast
	}
}

type ApplyInterface[T any] interface {
	Equal(T) bool
	IsZero() bool
}

// ApplyInterfacePtr compares the existing value with a new value and returns the updated value if
// they differ. Comparable types must have IsZero and Equal methods. If the new value is nil, the
// existing value is retained. If the new value is a zero-value, the existing value is NOT retained,
// it will be set to nil. If the value is changed, targetColumn is pushed to updatedColumns.
func ApplyInterfacePtr[T ApplyInterface[T]](
	existing *T,
	newVal *T,
	updatedColumns *mysql.ColumnList,
	targetColumn mysql.Column,
) *T {
	if newVal == nil {
		return existing
	}
	if existing != nil && (*existing).Equal(*newVal) {
		return existing
	}
	if (*newVal).IsZero() {
		if existing != nil {
			*updatedColumns = append(*updatedColumns, targetColumn)
		}
		return nil
	} else {
		*updatedColumns = append(*updatedColumns, targetColumn)
		return newVal
	}
}

// ApplyVal compares the existing value with a pointer to a new value and returns the updated value if they
// differ. If the new value is nil, the existing value is retained. If the value is changed, targetColumn
// is pushed to updatedColumns
func ApplyVal[T constraints.Float | constraints.Integer | string | bool](
	existing T,
	newVal *T,
	updatedColumns *mysql.ColumnList,
	targetColumn mysql.Column,
) T {
	if newVal == nil {
		return existing
	}
	if existing == *newVal {
		return existing
	}
	*updatedColumns = append(*updatedColumns, targetColumn)
	return *newVal
}