// Package ptr contains some utility methods related to pointers.
package ptr

import (
	"database/sql"

	"golang.org/x/exp/constraints"
)

type number interface {
	constraints.Integer | constraints.Float
}

// Ref returns a reference to v.
func Ref[T any](v T) *T {
	return &v
}

// NilOrEmpty returns true if s is nil or the empty string.
func NilOrEmpty(s *string) bool {
	return s == nil || *s == ""
}

// NilToEmpty coalesces a nil value to the empty value.
func NilToEmpty[T any](s *T) T {
	var def T
	if s == nil {
		return def
	}
	return *s
}

// NilToDefault coalesces a nil value to the provided default value.
func NilToDefault[T any](s *T, def T) T {
	if s == nil {
		return def
	}
	return *s
}

// NilOrZero returns true if v is nil or 0.
func NilOrZero[T number](v *T) bool {
	return v == nil || *v == 0
}

// FromNullString returns a pointer to the string when it is valid and nil
// otherwise.
func FromNullString(v sql.NullString) *string {
	if !v.Valid {
		return nil
	}
	value := v.String
	return &value
}