package inns

// The package implements the basic
// Russian Federation INN format
// storing it in int64 to keep
// searching and storing as
// quick as possible.

import (
	"strings"
	"unicode"
	"strconv"
	"fmt"
	"slices"
)

type InnType uint8
const (
	IncorrectInnType InnType = iota
	LegalInnType
	IndividualInnType
)

func removeSpaces(s string) string {
	return strings.Map(func(r rune) rune{
		if unicode.IsSpace(r) {
			return -1
		}
		return r
	}, s)
}

type Inn int64

func NewFromInt64(innRaw int64) (Inn, error) {
	inn := Inn(innRaw)
	if !inn.isCorrectLen() {
		return -1, IncorrectLenErr
	}

	if !inn.isSumCorrect() {
		return -1, SumsNotMatchErr
	}

	return inn, nil

}
// Convert string with spaces into the INN
// and return error if anything is wrong with it.
func NewFromStr(str string) (Inn, error) {
	str = removeSpaces(str)
	innRaw, err := strconv.ParseInt(str, 10, 64)
	if err != nil {
		return -1, IncorrectFormatErr
	}
	return NewFromInt64(innRaw)
}


func (inn Inn) Type() InnType {
	ln := inn.length()
	switch ln {
	case 9, 10:
		return LegalInnType
	case 11, 12:
		return IndividualInnType
	}
	return IncorrectInnType
}

func (inn Inn) length() int {
	ln := 0
	for {
		if inn == 0 {
			break
		}
		inn /= 10
		ln++
	}
	if ln == 9 || ln == 11 {
		ln++
	}
	return ln
}

func (inn Inn) isCorrectLen() bool {
	ln := inn.length()
	if ln == 9 || ln == 11 {
		ln++
	}
	return ln == 10 || ln == 12
}

var (
	// Koefs for the control sum.
	innSum10 = [9]int64{
		2, 4, 10, 3, 5, 9, 4, 6, 8,
	}
	innSum11 = [10]int64{
		7, 2, 4, 10, 3, 5, 9, 4, 6, 8,
	}
	innSum12 = [11]int64{
		3, 7, 2, 4, 10, 3, 5, 9, 4, 6, 8,
	}
)

// Get the integer representation of digits in string INN.
func (inn Inn) digits() []int64 {
	ln := inn.length()
	v := int64(inn)
	ret := make([]int64, ln)
	for i := 0 ; i<ln ; i++{
		ret[i] = v % 10
		v /= 10
	}
	slices.Reverse(ret)
	return ret
}

// 
func (inn Inn) specifiedSum() int64 {
	ln := inn.length()
	v := int64(inn)
	switch ln {
	case 10:
		return v%10
	case 12:
		return v%100
	default:
		return -1
	}
}

// Returns the supposed control sum rune. (the last number)
func (inn Inn) sum() int64 {
	d := inn.digits()
	ln := inn.length()
	switch ln {
	case 10 :
		var n10 int64
		for i, ni := range d[:9] {
			n10 += innSum10[i] * ni
		}
		n10 = (n10 % 11) % 10
		return n10
	case 12 :
		var n11 int64
		for i, ni := range d[:10] {
			n11 += innSum11[i] * ni
		}
		n11 = (n11 % 11) % 10

		var n12 int64
		for i, ni := range d[:10] {
			n12 += innSum12[i] * ni
		}
		n12 += innSum12[10] * n11
		n12 = (n12 % 11) % 10

		return n11*10 + n12
	}
	return -1
}

func (inn Inn) isSumCorrect() bool {
	return inn.specifiedSum() == inn.sum()
}

func (inn Inn) String() string {
	return fmt.Sprintf("%d", inn)
}

// Fancy way to print INN with space delimiters.
func (inn Inn) Fancy() string {
	ln := inn.length()
	str := fmt.Sprintf("%d", inn)

	// Adding zero depending on length.
	if len(str) == 9 || len(str) == 11 {
		str = "0"+str
	}

	switch ln {
	case 10 :
		return fmt.Sprintf("%s %s %s", str[:4], str[4:9], str[9:])
	case 12 :
		return fmt.Sprintf("%s %s %s", str[:4], str[4:10], str[10:])
	}

	// Reaching the point if the length is incorrect.
	return "<"+IncorrectLenErr.Error()+">"
}