package shrt

import (
  "fmt"
  "crypto/sha256"
  "errors"
  "encoding/json"
  "net/url"
  "os"
  "io"
  "bytes"
)

type Storage struct  {
  Token map[string]*shrt
  Url map[string]string
}

type shrt struct {
  URL string
  Datum string
  Count int64
}

var (
  ErrNotFound = errors.New("Url not Found")
  ErrCreateToken = errors.New("There are some problems while creating Token")
  ErrNoUrl = errors.New("String is no Url!")
)

func Open() (*Storage, error){
  s := Storage{Token: make(map[string]*shrt), Url: make(map[string]string)}
  // Open db ore create if not exist!
  if db, err := os.OpenFile("./test.db", os.O_RDWR|os.O_CREATE, 0644); err == nil {
    json.Unmarshal(StreamToByte(db), &s)
    db.Close()
    return &s, nil
  } else {
    return &s, err
  }
}

func (s *Storage) Add(URL string, value interface{}) (string, error) {
  // Check if it is a valide Url found on:
  // http://stackoverflow.com/questions/31480710/validate-url-with-standard-package-in-go
  _, err := url.ParseRequestURI(URL)
  if err != nil {
    return "", ErrNoUrl
  }

  // Create a sha256 Hash from the URL
  hash := fmt.Sprintf("%x", sha256.Sum256([]byte(URL)))

  // Test if the URL alraedy exist and return the key
  if val, ok := s.Url[hash]; ok {
    return val, nil
  }
  // Iterate to the length of hash to get the shortest output
  for hashShortestLen := 1; hashShortestLen <= 32; hashShortestLen++ {
    // Test if the Token not exist and return the new generated token
    if _, ok := s.Token[hash[:hashShortestLen]]; !ok {
      token := hash[:hashShortestLen]
      s.Token[token] = &shrt{URL: URL}
      s.Url[hash] = token
      value = s.Url[hash]
      s.Save()
      return token, nil
    }
  }

 return "", ErrCreateToken
}

func (s *Storage) Remove(URL string) error {
  return nil
}

// Get returns the URL for the given token
func (s *Storage) Get(token string) (string, bool) {
  if shrt, ok := s.Token[token]; ok {
    fmt.Printf("Url mit dem Token %s gefunden: %s \n", token, shrt.URL)
    s.Token[token].Count += 1
    s.Save()
    return shrt.URL, true
  }
  return "", false
}

func (s *Storage) All() (string) {
  b, err := json.Marshal(&s)
  if err != nil {
    return ""
  }
  return string(b)
}

func (s *Storage) Save() error {
  if db, err := os.OpenFile("./test.db", os.O_RDWR|os.O_CREATE, 0644); err == nil {
    b, err := json.Marshal(&s)
    db.Write(b)
    db.Close()
    return err
  } else {
    return err
  }
}

func StreamToByte(stream io.Reader) []byte {
  buf := new(bytes.Buffer)
  buf.ReadFrom(stream)
  return buf.Bytes()
}