package passage

import (
	"crypto/sha256"
	"strconv"
)

const (
	UseLower = 1 << iota
	UseUpper
	UseNumber
	UseSymbol
)

type Passage struct {
	valids int
	length int
	pin    string

	requireEachCharSet bool
}

func CreatePassage(pin string) *Passage {
	p := new(Passage)
	p.length = 20
	p.valids = UseLower | UseUpper | UseNumber | UseSymbol
	p.pin = pin
	return p
}

func (p *Passage) SetRequireEachCharSet(r bool) {
	p.requireEachCharSet = r
}

func (p *Passage) EnableChars(which int) {
	p.valids |= which
}

func (p *Passage) DisableChars(which int) {
	p.valids ^= which
}

func (p *Passage) SetLength(length int) {
	p.length = length
}

func (p *Passage) GetLowers() string {
	return "abcdefghijklmnopqrstuvwxyz"
}
func (p *Passage) GetUppers() string {
	return "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
}
func (p *Passage) GetNumbers() string {
	return "1234567890"
}
func (p *Passage) GetSymbols() string {
	return "~!@#$%^&*()[]{}|;:,<.>/?"
}

func (p *Passage) GetValidChars() string {
	validChars := ""
	if p.valids&UseLower == UseLower {
		validChars += p.GetLowers()
	}
	if p.valids&UseUpper == UseUpper {
		validChars += p.GetUppers()
	}
	if p.valids&UseNumber == UseNumber {
		validChars += p.GetNumbers()
	}
	if p.valids&UseSymbol == UseSymbol {
		validChars += p.GetSymbols()
	}
	return validChars
}
func (p *Passage) GetValidCharSets() []string {
	var validChars []string
	if p.valids&UseLower == UseLower {
		validChars = append(validChars, p.GetLowers())
	}
	if p.valids&UseUpper == UseUpper {
		validChars = append(validChars, p.GetUppers())
	}
	if p.valids&UseNumber == UseNumber {
		validChars = append(validChars, p.GetNumbers())
	}
	if p.valids&UseSymbol == UseSymbol {
		validChars = append(validChars, p.GetSymbols())
	}
	return validChars
}

func (p *Passage) SetPin(pin string) {
	p.pin = pin
}

func (p *Passage) GetPassword(door string) string {
	ret := ""
	hashing := p.pin + " - " + door
	shaArr := sha256.Sum256([]byte(hashing))
	var sha []byte
	for i := range shaArr {
		sha = append(sha, shaArr[i])
	}
	if p.requireEachCharSet {
		validChars := p.GetValidCharSets()
		for i := 0; i < p.length; i++ {
			set := i % len(validChars)
			ret += string(validChars[set][int(sha[i])%len(validChars)])
		}
	} else {
		validChars := p.GetValidChars()
		for i := 0; i < p.length; i++ {
			ret += string(validChars[int(sha[i])%len(validChars)])
		}
	}
	return ret
}

func (p *Passage) GetChecksum() int {
	ret := 0
	sha := sha256.Sum256([]byte(p.pin))
	for i := range sha {
		ret += int(sha[i])
	}
	return ret
}

func (p *Passage) GetChecksumAsString() string {
	return strconv.Itoa(p.GetChecksum())
}