package takuzu

import "fmt"

// This file contains the takuzu validation error type.

const (

	ErrorNil = iota

	ErrorDuplicate

	ErrorTooManyValues

	ErrorTooManyAdjacentValues

)

type validationError struct {

	ErrorType    int

	LineNumber   *int

	ColumnNumber *int

	CellValue    *int

}

func (e validationError) Error() string {

	var axis string

	var n int

	// Currently we don't have validation errors with both

	// line and column so we can get the axis:

	if e.LineNumber != nil {

		axis = "line"

		n = *e.LineNumber

	} else if e.ColumnNumber != nil {

		axis = "column"

		n = *e.ColumnNumber

	}

	switch e.ErrorType {

	case ErrorNil:

		return ""

	case ErrorDuplicate:

		if axis == "" {

			return "internal validation error"

		}

		return fmt.Sprintf("duplicate %ss (%d)", axis, n)

	case ErrorTooManyValues:

		if axis == "" || e.CellValue == nil {

			return "internal validation error"

		}

		var numberStr string

		if *e.CellValue == 0 {

			numberStr = "zeroes"

		} else if *e.CellValue == 1 {

			numberStr = "ones"

		} else {

			return "internal validation error"

		}

		return fmt.Sprintf("%s %d: too many %s", axis, n, numberStr)

	case ErrorTooManyAdjacentValues:

		if axis == "" || e.CellValue == nil {

			return "internal validation error"

		}

		return fmt.Sprintf("%s %d: 3+ same values %d", axis, n, *e.CellValue)

	}

	return "internal validation error"

}