package session

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"crypto/sha1"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"
)

type SessionStore interface {
	Set(key, value interface{}) error //set session value
	Get(key interface{}) interface{}  //get session value
	Delete(key interface{}) error     //delete session value
	SessionID() string                //back current sessionID
	SessionRelease()                  // release the resource
	Flush() error                     //delete all data
}

type Provider interface {
	SessionInit(maxlifetime int64, savePath string) error
	SessionRead(sid string) (SessionStore, error)
	SessionRegenerate(oldsid, sid string) (SessionStore, error)
	SessionDestroy(sid string) error
	SessionGC()
}

var provides = make(map[string]Provider)

// Register makes a session provide available by the provided name.
// If Register is called twice with the same name or if driver is nil,
// it panics.
func Register(name string, provide Provider) {
	if provide == nil {
		panic("session: Register provide is nil")
	}
	if _, dup := provides[name]; dup {
		panic("session: Register called twice for provider " + name)
	}
	provides[name] = provide
}

type Manager struct {
	cookieName  string //private cookiename
	provider    Provider
	maxlifetime int64
	hashfunc    string //support md5 & sha1
	hashkey     string
	maxage      int
	secure      bool
	options     []interface{}
}

//options
//1. is https  default false
//2. hashfunc  default sha1
//3. hashkey default beegosessionkey
//4. maxage default is none
func NewManager(provideName, cookieName string, maxlifetime int64, savePath string, options ...interface{}) (*Manager, error) {
	provider, ok := provides[provideName]
	if !ok {
		return nil, fmt.Errorf("session: unknown provide %q (forgotten import?)", provideName)
	}
	provider.SessionInit(maxlifetime, savePath)
	secure := false
	if len(options) > 0 {
		secure = options[0].(bool)
	}
	hashfunc := "sha1"
	if len(options) > 1 {
		hashfunc = options[1].(string)
	}
	hashkey := "beegosessionkey"
	if len(options) > 2 {
		hashkey = options[2].(string)
	}
	maxage := -1
	if len(options) > 3 {
		switch options[3].(type) {
		case int:
			if options[3].(int) > 0 {
				maxage = options[3].(int)
			} else if options[3].(int) < 0 {
				maxage = 0
			}
		case int64:
			if options[3].(int64) > 0 {
				maxage = int(options[3].(int64))
			} else if options[3].(int64) < 0 {
				maxage = 0
			}
		case int32:
			if options[3].(int32) > 0 {
				maxage = int(options[3].(int32))
			} else if options[3].(int32) < 0 {
				maxage = 0
			}
		}
	}
	return &Manager{
		provider:    provider,
		cookieName:  cookieName,
		maxlifetime: maxlifetime,
		hashfunc:    hashfunc,
		hashkey:     hashkey,
		maxage:      maxage,
		secure:      secure,
		options:     options,
	}, nil
}

//get Session
func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (session SessionStore) {
	cookie, err := r.Cookie(manager.cookieName)
	if err != nil || cookie.Value == "" {
		sid := manager.sessionId(r)
		session, _ = manager.provider.SessionRead(sid)
		cookie = &http.Cookie{Name: manager.cookieName,
			Value:    url.QueryEscape(sid),
			Path:     "/",
			HttpOnly: true,
			Secure:   manager.secure}
		if manager.maxage >= 0 {
			cookie.MaxAge = manager.maxage
		}
		//cookie.Expires = time.Now().Add(time.Duration(manager.maxlifetime) * time.Second)
		http.SetCookie(w, cookie)
		r.AddCookie(cookie)
	} else {
		//cookie.Expires = time.Now().Add(time.Duration(manager.maxlifetime) * time.Second)
		cookie.HttpOnly = true
		cookie.Path = "/"
		if manager.maxage >= 0 {
			cookie.MaxAge = manager.maxage
		}
		http.SetCookie(w, cookie)
		sid, _ := url.QueryUnescape(cookie.Value)
		session, _ = manager.provider.SessionRead(sid)
	}
	return
}

//Destroy sessionid
func (manager *Manager) SessionDestroy(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie(manager.cookieName)
	if err != nil || cookie.Value == "" {
		return
	} else {
		manager.provider.SessionDestroy(cookie.Value)
		expiration := time.Now()
		cookie := http.Cookie{Name: manager.cookieName, Path: "/", HttpOnly: true, Expires: expiration, MaxAge: -1}
		http.SetCookie(w, &cookie)
	}
}

func (manager *Manager) GC() {
	manager.provider.SessionGC()
	time.AfterFunc(time.Duration(manager.maxlifetime)*time.Second, func() { manager.GC() })
}

func (manager *Manager) SessionRegenerateId(w http.ResponseWriter, r *http.Request) (session SessionStore) {
	sid := manager.sessionId(r)
	cookie, err := r.Cookie(manager.cookieName)
	if err != nil && cookie.Value == "" {
		//delete old cookie
		session, _ = manager.provider.SessionRead(sid)
		cookie = &http.Cookie{Name: manager.cookieName,
			Value:    url.QueryEscape(sid),
			Path:     "/",
			HttpOnly: true,
			Secure:   manager.secure,
		}
	} else {
		oldsid, _ := url.QueryUnescape(cookie.Value)
		session, _ = manager.provider.SessionRegenerate(oldsid, sid)
		cookie.Value = url.QueryEscape(sid)
		cookie.HttpOnly = true
		cookie.Path = "/"
	}
	if manager.maxage >= 0 {
		cookie.MaxAge = manager.maxage
	}
	http.SetCookie(w, cookie)
	r.AddCookie(cookie)
	return
}

//remote_addr cruunixnano randdata

func (manager *Manager) sessionId(r *http.Request) (sid string) {
	bs := make([]byte, 24)
	if _, err := io.ReadFull(rand.Reader, bs); err != nil {
		return ""
	}
	sig := fmt.Sprintf("%s%d%s", r.RemoteAddr, time.Now().UnixNano(), bs)
	if manager.hashfunc == "md5" {
		h := md5.New()
		h.Write([]byte(sig))
		sid = hex.EncodeToString(h.Sum(nil))
	} else if manager.hashfunc == "sha1" {
		h := hmac.New(sha1.New, []byte(manager.hashkey))
		fmt.Fprintf(h, "%s", sig)
		sid = hex.EncodeToString(h.Sum(nil))
	} else {
		h := hmac.New(sha1.New, []byte(manager.hashkey))
		fmt.Fprintf(h, "%s", sig)
		sid = hex.EncodeToString(h.Sum(nil))
	}
	return
}