// Copyright (c) Acrosync LLC. All rights reserved.
// Licensed under the Fair Source License 0.9 (https://fair.io/)
// User Limitation: 5 users

package duplicacy

import (
    "fmt"
    "os"
    "bufio"
    "io"
    "io/ioutil"
    "time"
    "path"
    "path/filepath"
    "regexp"
    "strings"
    "strconv"
    "runtime"
    "crypto/sha256"

    "golang.org/x/crypto/pbkdf2"
    "github.com/gilbertchen/gopass"
)

var RunInBackground bool = false

type RateLimitedReader struct {
    Content []byte
    Rate float64
    Next int
    StartTime time.Time
}

func CreateRateLimitedReader(content []byte, rate int) (*RateLimitedReader) {
    return &RateLimitedReader {
        Content: content,
        Rate: float64(rate * 1024),
        Next: 0,
    }
}

func (reader *RateLimitedReader) Length() (int64) {
    return int64(len(reader.Content))
}

func (reader *RateLimitedReader) Reset() {
    reader.Next = 0
}

func (reader *RateLimitedReader)  Seek(offset int64, whence int) (int64, error) {
    if whence == io.SeekStart {
        reader.Next = int(offset)
    } else if whence == io.SeekCurrent {
        reader.Next += int(offset)
    } else {
        reader.Next = len(reader.Content) - int(offset)
    }
    return int64(reader.Next), nil
}

func (reader *RateLimitedReader) Read(p []byte) (n int, err error) {

    if reader.Next >= len(reader.Content) {
        return 0, io.EOF
    }

    if reader.Rate <= 0 {
        n := copy(p, reader.Content[reader.Next:])
        reader.Next += n
        if reader.Next >= len(reader.Content) {
            return n, io.EOF
        }
        return n, nil
    }

    if reader.StartTime.IsZero() {
        reader.StartTime = time.Now()
    }

    elapsed := time.Since(reader.StartTime).Seconds()
    delay := float64(reader.Next) / reader.Rate - elapsed
    end := reader.Next + int(reader.Rate / 5)
    if delay > 0 {
        time.Sleep(time.Duration(delay *  float64(time.Second)))
    } else {
        end += - int(delay * reader.Rate)
    }

    if end > len(reader.Content) {
        end = len(reader.Content)
    }

    n = copy(p, reader.Content[reader.Next : end])
    reader.Next += n
    return n, nil
}

func RateLimitedCopy(writer io.Writer, reader io.Reader, rate int) (written int64, err error) {
    if rate <= 0 {
        return io.Copy(writer, reader)
    }
    for range time.Tick(time.Second / 5) {
        n, err := io.CopyN(writer, reader, int64(rate * 1024 / 5))
        written += n
        if err != nil {
            if err == io.EOF {
                return written, nil
            } else {
                return written, err
            }
        }
    }
    return written, nil
}

// GenerateKeyFromPassword generates a key from the password.
func GenerateKeyFromPassword(password string) []byte {
    return pbkdf2.Key([]byte(password), DEFAULT_KEY, 16384, 32, sha256.New)
}

// GetPassword attempts to get the password from KeyChain/KeyRing, environment variables, or keyboard input.
func GetPassword(preference Preference, passwordType string, prompt string,
                 showPassword bool, resetPassword bool) (string) {

    passwordID := passwordType
    if preference.Name != "default" {
        passwordID = preference.Name + "_" + passwordID
    }

    {
        name := strings.ToUpper("duplicacy_" + passwordID)
        LOG_DEBUG("PASSWORD_ENV_VAR", "Reading the environment variable %s", name)
        if password, found := os.LookupEnv(name); found && password != "" {
            return password
        }
    }

    if len(preference.Keys) > 0 && len(preference.Keys[passwordID]) > 0 {
        LOG_DEBUG("PASSWORD_KEYCHAIN", "Reading %s from preferences", passwordID)
        return preference.Keys[passwordID]
    }

    if resetPassword && !RunInBackground {
        keyringSet(passwordID, "")
    } else {
        password := keyringGet(passwordID)
        if password != "" {
            return password
        }

        if RunInBackground {
            LOG_INFO("PASSWORD_MISSING", "%s is not found in Keychain/Keyring", passwordID)
            return ""
        }

    }

    password := ""
    fmt.Printf("%s", prompt)
    if showPassword {
        scanner := bufio.NewScanner(os.Stdin)
        scanner.Scan()
        password = scanner.Text()
    } else {
        passwordInBytes, err := gopass.GetPasswdMasked()
        if err != nil {
            LOG_ERROR("PASSWORD_READ", "Failed to read the password: %v", err)
            return ""
        }
        password = string(passwordInBytes)
    }

    return password
}

// SavePassword saves the specified password in the keyring/keychain.
func SavePassword(preference Preference, passwordType string, password string) {
    if password == "" || RunInBackground {
        return
    }

    if preference.DoNotSavePassword {
        return
    }
    passwordID := passwordType
    if preference.Name != "default" {
        passwordID = preference.Name + "_" + passwordID
    }
    keyringSet(passwordID, password)
}

// RemoveEmptyDirectories remove all empty subdirectoreies under top.
func RemoveEmptyDirectories(top string) {

    stack := make([]string, 0, 256)

    stack = append(stack, top)

    for len(stack) > 0 {

        dir := stack[len(stack) - 1]
        stack = stack[:len(stack) - 1]

        files, err := ioutil.ReadDir(dir)

        if err != nil {
            continue
        }

        for _, file := range files {
            if file.IsDir() && file.Name()[0] != '.' {
                stack = append(stack, path.Join(dir, file.Name()))
            }
        }

        if len(files) == 0 {
            if os.Remove(dir) != nil {
                continue
            }

            dir = path.Dir(dir)
            for (len(dir) > len(top)) {
                files, err := ioutil.ReadDir(dir)
                if err != nil {
                    break
                }

                if len(files) == 0 {
                    if os.Remove(dir) != nil {
                        break;
                    }
                }
                dir = path.Dir(dir)
            }
        }
    }
}


// The following code was modified from the online article  'Matching Wildcards: An Algorithm', by Kirk J. Krauss,
// Dr. Dobb's, August 26, 2008. However, the version in the article doesn't handle cases like matching 'abcccd'
// against '*ccd', and the version here fixed that issue.
//
func matchPattern(text string, pattern string) bool {

    textLength := len(text)
    patternLength := len(pattern)
    afterLastWildcard := 0
    afterLastMatched := 0

    t := 0
    p := 0

    for {
        if t >= textLength {
            if p >= patternLength {
                return true           // "x" matches "x"
            } else if pattern[p] == '*' {
                p++
                continue              // "x*" matches "x" or "xy"
            }
            return false              // "x" doesn't match "xy"
        }

        w := byte(0)
        if p < patternLength {
            w = pattern[p]
        }

        if text[t] != w  {
            if w == '?' {
                t++
                p++
                continue
            } else if w == '*' {
                p++
                afterLastWildcard = p
                if p >= patternLength {
                    return true
                }
            } else if afterLastWildcard > 0 {
                p = afterLastWildcard
                t = afterLastMatched
                t++
            } else {
                return false
            }

            for t < textLength && text[t] != pattern[p] && pattern[p] != '?' {
                t++
            }

            if t >= textLength {
                return false
            }
            afterLastMatched = t
        }
        t++
        p++
   }

}

// MatchPath returns 'true' if the file 'filePath' is excluded by the specified 'patterns'.  Each pattern starts with
// either '+' or '-', whereas '-' indicates exclusion and '+' indicates inclusion.  Wildcards like '*' and '?' may
// appear in the patterns.  In case no matching pattern is found, the file will be excluded if all patterns are
// include patterns, and included otherwise.
func MatchPath(filePath string, patterns [] string) (included bool) {

    allIncludes := true
    for _, pattern := range patterns {

        if pattern[0] == '+' {
            if matchPattern(filePath, pattern[1:]) {
                return true
            }
        } else if pattern[0] == '-' {
            allIncludes = false
             if matchPattern(filePath, pattern[1:]) {
                return false
            }
        }
    }

    return !allIncludes
}

func joinPath(components ...string) string {

    combinedPath := path.Join(components...)
    if len(combinedPath) > 257 && runtime.GOOS == "windows" {
        combinedPath = `\\?\` + filepath.Join(components...)
    }
    return combinedPath
}

func PrettyNumber(number int64) (string) {

    G := int64(1024 * 1024 * 1024)
    M := int64(1024 * 1024)
    K := int64(1024)

    if number > 1000 * G {
        return fmt.Sprintf("%dG", number / G)
    } else if number > G {
        return fmt.Sprintf("%d,%03dM", number / (1000 * M), (number / M) % 1000)
    } else if number > M {
        return fmt.Sprintf("%d,%03dK", number / (1000 * K), (number / K) % 1000)
    } else if number > K {
        return fmt.Sprintf("%dK", number / K)
    } else {
        return fmt.Sprintf("%d", number)
    }
}

func PrettySize(size int64) (string) {
    if size > 1024 * 1024 {
        return fmt.Sprintf("%.2fM", float64(size) / (1024.0 * 1024.0))
    } else if size > 1024 {
        return fmt.Sprintf("%.0fK", float64(size) / 1024.0)
    } else {
        return fmt.Sprintf("%d", size)
    }
}

func PrettyTime(seconds int64) (string) {

    day := int64(3600 * 24)

    if seconds > day * 2 {
        return fmt.Sprintf("%d days %02d:%02d:%02d",
                           seconds / day, (seconds % day) / 3600, (seconds % 3600) / 60, seconds % 60)
    } else if seconds > day {
        return fmt.Sprintf("1 day %02d:%02d:%02d", (seconds % day) / 3600, (seconds % 3600) / 60, seconds % 60)
    } else if seconds > 0 {
        return fmt.Sprintf("%02d:%02d:%02d", seconds / 3600, (seconds % 3600) / 60, seconds % 60)
    } else {
        return "n/a"
    }
}

func AtoSize(sizeString string) (int) {
    sizeString = strings.ToLower(sizeString)

    sizeRegex := regexp.MustCompile(`^([0-9]+)([mk])?$`)
    matched := sizeRegex.FindStringSubmatch(sizeString)
    if matched == nil {
        return 0
    }

    size, _ := strconv.Atoi(matched[1])

    if matched[2] == "m" {
        size *= 1024 * 1024
    } else if matched[2] == "k" {
        size *= 1024
    }

    return size
}