package fic

import (
	"bytes"
	"crypto/md5"
	"regexp"
	"strings"
)

// ToURLid converts the given string to a valid URLid.
func ToURLid(str string) string {
	re := regexp.MustCompile("[^a-zA-Z0-9]+")
	return strings.TrimSuffix(re.ReplaceAllLiteralString(str, "-"), "-")
}

// Apr1Md5 computes a usable hash for basic auth in Apache and nginx.
// Function copied from https://github.com/jimstudt/http-authentication/blob/master/basic/md5.go
// as it was not exported in package and comes with other unwanted functions.
// Original source code under MIT.
func Apr1Md5(password string, salt string) string {
	initBin := md5.Sum([]byte(password + salt + password))

	initText := bytes.NewBufferString(password + "$apr1$" + salt)

	for i := len(password); i > 0; i -= 16 {
		lim := i
		if lim > 16 {
			lim = 16
		}
		initText.Write(initBin[0:lim])
	}

	for i := len(password); i > 0; i >>= 1 {
		if (i & 1) == 1 {
			initText.WriteByte(byte(0))
		} else {
			initText.WriteByte(password[0])
		}
	}

	bin := md5.Sum(initText.Bytes())

	n := bytes.NewBuffer([]byte{})

	for i := 0; i < 1000; i++ {
		n.Reset()

		if (i & 1) == 1 {
			n.WriteString(password)
		} else {
			n.Write(bin[:])
		}

		if i%3 != 0 {
			n.WriteString(salt)
		}

		if i%7 != 0 {
			n.WriteString(password)
		}

		if (i & 1) == 1 {
			n.Write(bin[:])
		} else {
			n.WriteString(password)
		}

		bin = md5.Sum(n.Bytes())
	}

	result := bytes.NewBuffer([]byte{})

	fill := func(a byte, b byte, c byte) {
		v := (uint(a) << 16) + (uint(b) << 8) + uint(c)

		for i := 0; i < 4; i++ {
			result.WriteByte("./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"[v&0x3f])
			v >>= 6
		}
	}

	fill(bin[0], bin[6], bin[12])
	fill(bin[1], bin[7], bin[13])
	fill(bin[2], bin[8], bin[14])
	fill(bin[3], bin[9], bin[15])
	fill(bin[4], bin[10], bin[5])
	fill(0, 0, bin[11])

	resultString := string(result.Bytes()[0:22])

	return resultString
}