// Copyright 2014 The Gogs Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package base

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"crypto/sha1"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"hash"
	"html/template"
	"math"
	"net/http"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"github.com/Unknwon/com"
	"github.com/Unknwon/i18n"

	"github.com/gogits/chardet"

	"github.com/gogits/gogs/modules/log"
	"github.com/gogits/gogs/modules/setting"
)

// EncodeMD5 encodes string to md5 hex value.
func EncodeMD5(str string) string {
	m := md5.New()
	m.Write([]byte(str))
	return hex.EncodeToString(m.Sum(nil))
}

// Encode string to sha1 hex value.
func EncodeSha1(str string) string {
	h := sha1.New()
	h.Write([]byte(str))
	return hex.EncodeToString(h.Sum(nil))
}

func ShortSha(sha1 string) string {
	if len(sha1) == 40 {
		return sha1[:10]
	}
	return sha1
}

func DetectEncoding(content []byte) (string, error) {
	if utf8.Valid(content) {
		log.Debug("Detected encoding: utf-8 (fast)")
		return "UTF-8", nil
	}

	result, err := chardet.NewTextDetector().DetectBest(content)
	if result.Charset != "UTF-8" && len(setting.Repository.AnsiCharset) > 0 {
		log.Debug("Using default AnsiCharset: %s", setting.Repository.AnsiCharset)
		return setting.Repository.AnsiCharset, err
	}

	log.Debug("Detected encoding: %s", result.Charset)
	return result.Charset, err
}

func BasicAuthDecode(encoded string) (string, string, error) {
	s, err := base64.StdEncoding.DecodeString(encoded)
	if err != nil {
		return "", "", err
	}

	auth := strings.SplitN(string(s), ":", 2)
	return auth[0], auth[1], nil
}

func BasicAuthEncode(username, password string) string {
	return base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
}

// GetRandomString generate random string by specify chars.
func GetRandomString(n int, alphabets ...byte) string {
	const alphanum = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
	var bytes = make([]byte, n)
	rand.Read(bytes)
	for i, b := range bytes {
		if len(alphabets) == 0 {
			bytes[i] = alphanum[b%byte(len(alphanum))]
		} else {
			bytes[i] = alphabets[b%byte(len(alphabets))]
		}
	}
	return string(bytes)
}

// http://code.google.com/p/go/source/browse/pbkdf2/pbkdf2.go?repo=crypto
// FIXME: use https://godoc.org/golang.org/x/crypto/pbkdf2?
func PBKDF2(password, salt []byte, iter, keyLen int, h func() hash.Hash) []byte {
	prf := hmac.New(h, password)
	hashLen := prf.Size()
	numBlocks := (keyLen + hashLen - 1) / hashLen

	var buf [4]byte
	dk := make([]byte, 0, numBlocks*hashLen)
	U := make([]byte, hashLen)
	for block := 1; block <= numBlocks; block++ {
		// N.B.: || means concatenation, ^ means XOR
		// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
		// U_1 = PRF(password, salt || uint(i))
		prf.Reset()
		prf.Write(salt)
		buf[0] = byte(block >> 24)
		buf[1] = byte(block >> 16)
		buf[2] = byte(block >> 8)
		buf[3] = byte(block)
		prf.Write(buf[:4])
		dk = prf.Sum(dk)
		T := dk[len(dk)-hashLen:]
		copy(U, T)

		// U_n = PRF(password, U_(n-1))
		for n := 2; n <= iter; n++ {
			prf.Reset()
			prf.Write(U)
			U = U[:0]
			U = prf.Sum(U)
			for x := range U {
				T[x] ^= U[x]
			}
		}
	}
	return dk[:keyLen]
}

// verify time limit code
func VerifyTimeLimitCode(data string, minutes int, code string) bool {
	if len(code) <= 18 {
		return false
	}

	// split code
	start := code[:12]
	lives := code[12:18]
	if d, err := com.StrTo(lives).Int(); err == nil {
		minutes = d
	}

	// right active code
	retCode := CreateTimeLimitCode(data, minutes, start)
	if retCode == code && minutes > 0 {
		// check time is expired or not
		before, _ := time.ParseInLocation("200601021504", start, time.Local)
		now := time.Now()
		if before.Add(time.Minute*time.Duration(minutes)).Unix() > now.Unix() {
			return true
		}
	}

	return false
}

const TimeLimitCodeLength = 12 + 6 + 40

// create a time limit code
// code format: 12 length date time string + 6 minutes string + 40 sha1 encoded string
func CreateTimeLimitCode(data string, minutes int, startInf interface{}) string {
	format := "200601021504"

	var start, end time.Time
	var startStr, endStr string

	if startInf == nil {
		// Use now time create code
		start = time.Now()
		startStr = start.Format(format)
	} else {
		// use start string create code
		startStr = startInf.(string)
		start, _ = time.ParseInLocation(format, startStr, time.Local)
		startStr = start.Format(format)
	}

	end = start.Add(time.Minute * time.Duration(minutes))
	endStr = end.Format(format)

	// create sha1 encode string
	sh := sha1.New()
	sh.Write([]byte(data + setting.SecretKey + startStr + endStr + com.ToStr(minutes)))
	encoded := hex.EncodeToString(sh.Sum(nil))

	code := fmt.Sprintf("%s%06d%s", startStr, minutes, encoded)
	return code
}

// HashEmail hashes email address to MD5 string.
// https://en.gravatar.com/site/implement/hash/
func HashEmail(email string) string {
	email = strings.ToLower(strings.TrimSpace(email))
	h := md5.New()
	h.Write([]byte(email))
	return hex.EncodeToString(h.Sum(nil))
}

// AvatarLink returns avatar link by given email.
func AvatarLink(email string) string {
	if setting.DisableGravatar || setting.OfflineMode {
		return setting.AppSubUrl + "/img/avatar_default.png"
	}

	return setting.GravatarSource + HashEmail(email)
}

// Seconds-based time units
const (
	Minute = 60
	Hour   = 60 * Minute
	Day    = 24 * Hour
	Week   = 7 * Day
	Month  = 30 * Day
	Year   = 12 * Month
)

func computeTimeDiff(diff int64) (int64, string) {
	diffStr := ""
	switch {
	case diff <= 0:
		diff = 0
		diffStr = "now"
	case diff < 2:
		diff = 0
		diffStr = "1 second"
	case diff < 1*Minute:
		diffStr = fmt.Sprintf("%d seconds", diff)
		diff = 0

	case diff < 2*Minute:
		diff -= 1 * Minute
		diffStr = "1 minute"
	case diff < 1*Hour:
		diffStr = fmt.Sprintf("%d minutes", diff/Minute)
		diff -= diff / Minute * Minute

	case diff < 2*Hour:
		diff -= 1 * Hour
		diffStr = "1 hour"
	case diff < 1*Day:
		diffStr = fmt.Sprintf("%d hours", diff/Hour)
		diff -= diff / Hour * Hour

	case diff < 2*Day:
		diff -= 1 * Day
		diffStr = "1 day"
	case diff < 1*Week:
		diffStr = fmt.Sprintf("%d days", diff/Day)
		diff -= diff / Day * Day

	case diff < 2*Week:
		diff -= 1 * Week
		diffStr = "1 week"
	case diff < 1*Month:
		diffStr = fmt.Sprintf("%d weeks", diff/Week)
		diff -= diff / Week * Week

	case diff < 2*Month:
		diff -= 1 * Month
		diffStr = "1 month"
	case diff < 1*Year:
		diffStr = fmt.Sprintf("%d months", diff/Month)
		diff -= diff / Month * Month

	case diff < 2*Year:
		diff -= 1 * Year
		diffStr = "1 year"
	default:
		diffStr = fmt.Sprintf("%d years", diff/Year)
		diff = 0
	}
	return diff, diffStr
}

// TimeSincePro calculates the time interval and generate full user-friendly string.
func TimeSincePro(then time.Time) string {
	now := time.Now()
	diff := now.Unix() - then.Unix()

	if then.After(now) {
		return "future"
	}

	var timeStr, diffStr string
	for {
		if diff == 0 {
			break
		}

		diff, diffStr = computeTimeDiff(diff)
		timeStr += ", " + diffStr
	}
	return strings.TrimPrefix(timeStr, ", ")
}

func timeSince(then time.Time, lang string) string {
	now := time.Now()

	lbl := i18n.Tr(lang, "tool.ago")
	diff := now.Unix() - then.Unix()
	if then.After(now) {
		lbl = i18n.Tr(lang, "tool.from_now")
		diff = then.Unix() - now.Unix()
	}

	switch {
	case diff <= 0:
		return i18n.Tr(lang, "tool.now")
	case diff <= 2:
		return i18n.Tr(lang, "tool.1s", lbl)
	case diff < 1*Minute:
		return i18n.Tr(lang, "tool.seconds", diff, lbl)

	case diff < 2*Minute:
		return i18n.Tr(lang, "tool.1m", lbl)
	case diff < 1*Hour:
		return i18n.Tr(lang, "tool.minutes", diff/Minute, lbl)

	case diff < 2*Hour:
		return i18n.Tr(lang, "tool.1h", lbl)
	case diff < 1*Day:
		return i18n.Tr(lang, "tool.hours", diff/Hour, lbl)

	case diff < 2*Day:
		return i18n.Tr(lang, "tool.1d", lbl)
	case diff < 1*Week:
		return i18n.Tr(lang, "tool.days", diff/Day, lbl)

	case diff < 2*Week:
		return i18n.Tr(lang, "tool.1w", lbl)
	case diff < 1*Month:
		return i18n.Tr(lang, "tool.weeks", diff/Week, lbl)

	case diff < 2*Month:
		return i18n.Tr(lang, "tool.1mon", lbl)
	case diff < 1*Year:
		return i18n.Tr(lang, "tool.months", diff/Month, lbl)

	case diff < 2*Year:
		return i18n.Tr(lang, "tool.1y", lbl)
	default:
		return i18n.Tr(lang, "tool.years", diff/Year, lbl)
	}
}

func RawTimeSince(t time.Time, lang string) string {
	return timeSince(t, lang)
}

// TimeSince calculates the time interval and generate user-friendly string.
func TimeSince(t time.Time, lang string) template.HTML {
	return template.HTML(fmt.Sprintf(`<span class="time-since" title="%s">%s</span>`, t.Format(setting.TimeFormat), timeSince(t, lang)))
}

const (
	Byte  = 1
	KByte = Byte * 1024
	MByte = KByte * 1024
	GByte = MByte * 1024
	TByte = GByte * 1024
	PByte = TByte * 1024
	EByte = PByte * 1024
)

var bytesSizeTable = map[string]uint64{
	"b":  Byte,
	"kb": KByte,
	"mb": MByte,
	"gb": GByte,
	"tb": TByte,
	"pb": PByte,
	"eb": EByte,
}

func logn(n, b float64) float64 {
	return math.Log(n) / math.Log(b)
}

func humanateBytes(s uint64, base float64, sizes []string) string {
	if s < 10 {
		return fmt.Sprintf("%dB", s)
	}
	e := math.Floor(logn(float64(s), base))
	suffix := sizes[int(e)]
	val := float64(s) / math.Pow(base, math.Floor(e))
	f := "%.0f"
	if val < 10 {
		f = "%.1f"
	}

	return fmt.Sprintf(f+"%s", val, suffix)
}

// FileSize calculates the file size and generate user-friendly string.
func FileSize(s int64) string {
	sizes := []string{"B", "KB", "MB", "GB", "TB", "PB", "EB"}
	return humanateBytes(uint64(s), 1024, sizes)
}

// Subtract deals with subtraction of all types of number.
func Subtract(left interface{}, right interface{}) interface{} {
	var rleft, rright int64
	var fleft, fright float64
	var isInt bool = true
	switch left.(type) {
	case int:
		rleft = int64(left.(int))
	case int8:
		rleft = int64(left.(int8))
	case int16:
		rleft = int64(left.(int16))
	case int32:
		rleft = int64(left.(int32))
	case int64:
		rleft = left.(int64)
	case float32:
		fleft = float64(left.(float32))
		isInt = false
	case float64:
		fleft = left.(float64)
		isInt = false
	}

	switch right.(type) {
	case int:
		rright = int64(right.(int))
	case int8:
		rright = int64(right.(int8))
	case int16:
		rright = int64(right.(int16))
	case int32:
		rright = int64(right.(int32))
	case int64:
		rright = right.(int64)
	case float32:
		fright = float64(left.(float32))
		isInt = false
	case float64:
		fleft = left.(float64)
		isInt = false
	}

	if isInt {
		return rleft - rright
	} else {
		return fleft + float64(rleft) - (fright + float64(rright))
	}
}

// EllipsisString returns a truncated short string,
// it appends '...' in the end of the length of string is too large.
func EllipsisString(str string, length int) string {
	if len(str) < length {
		return str
	}
	return str[:length-3] + "..."
}

// TruncateString returns a truncated string with given limit,
// it returns input string if length is not reached limit.
func TruncateString(str string, limit int) string {
	if len(str) < limit {
		return str
	}
	return str[:limit]
}

// StringsToInt64s converts a slice of string to a slice of int64.
func StringsToInt64s(strs []string) []int64 {
	ints := make([]int64, len(strs))
	for i := range strs {
		ints[i] = com.StrTo(strs[i]).MustInt64()
	}
	return ints
}

// Int64sToStrings converts a slice of int64 to a slice of string.
func Int64sToStrings(ints []int64) []string {
	strs := make([]string, len(ints))
	for i := range ints {
		strs[i] = com.ToStr(ints[i])
	}
	return strs
}

// Int64sToMap converts a slice of int64 to a int64 map.
func Int64sToMap(ints []int64) map[int64]bool {
	m := make(map[int64]bool)
	for _, i := range ints {
		m[i] = true
	}
	return m
}

// IsLetter reports whether the rune is a letter (category L).
// https://github.com/golang/go/blob/master/src/go/scanner/scanner.go#L257
func IsLetter(ch rune) bool {
	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
}

func IsTextFile(data []byte) (string, bool) {
	contentType := http.DetectContentType(data)
	if strings.Index(contentType, "text/") != -1 {
		return contentType, true
	}
	return contentType, false
}

func IsImageFile(data []byte) (string, bool) {
	contentType := http.DetectContentType(data)
	if strings.Index(contentType, "image/") != -1 {
		return contentType, true
	}
	return contentType, false
}

func IsPDFFile(data []byte) (string, bool) {
	contentType := http.DetectContentType(data)
	if strings.Index(contentType, "application/pdf") != -1 {
		return contentType, true
	}
	return contentType, false
}
