package validate

import (
	"strings"
)

var (
	ErrMissingPrefix    = NewError("must start with %q")
	ErrMissingSuffix    = NewError("must end with %q")
	ErrMissingSubstring = NewError("must contain %q")
)

// Prefix validates that a string begins with a given prefix.
func Prefix(prefix string) func(string) error {
	return func(value string) error {
		if !strings.HasPrefix(value, prefix) {
			return ErrMissingPrefix.With(prefix)
		}
		return nil
	}
}

// Suffix validates that a string ends with a given suffix.
func Suffix(suffix string) func(string) error {
	return func(value string) error {
		if !strings.HasSuffix(value, suffix) {
			return ErrMissingSuffix.With(suffix)
		}
		return nil
	}
}

// Contains validates that a string contains a given substring.
func Contains(substr string) func(string) error {
	return func(value string) error {
		if !strings.Contains(value, substr) {
			return ErrMissingSubstring.With(substr)
		}
		return nil
	}
}