package mongostore

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/gorilla/securecookie"
	"github.com/gorilla/sessions"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo"
)

type MongoStore struct {
	client  *mongo.Client
	Codecs  []securecookie.Codec
	Options *sessions.Options

	dbDatabaseName   string
	dbCollectionName string
	dbTimeout        time.Duration
}

func NewMongoStore(client *mongo.Client, dbDatabase, dbCollection string, dbTimeout time.Duration, keyPairs ...[]byte) *MongoStore {
	s := new(MongoStore)
	s.client = client
	s.dbDatabaseName = dbDatabase
	s.dbCollectionName = dbCollection
	s.dbTimeout = dbTimeout
	s.Options = &sessions.Options{
		Path:   "/",
		MaxAge: 86400 * 30 * 365,
	}
	s.Codecs = securecookie.CodecsFromPairs(keyPairs...)
	return s
}

func (s *MongoStore) MaxAge(age int) {
	s.Options.MaxAge = age

	for _, codec := range s.Codecs {
		if sc, ok := codec.(*securecookie.SecureCookie); ok {
			sc.MaxAge(age)
		}
	}
}

func (s *MongoStore) New(r *http.Request, name string) (*sessions.Session, error) {
	session := sessions.NewSession(s, name)
	session.Options = &sessions.Options{
		Path:     s.Options.Path,
		MaxAge:   s.Options.MaxAge,
		Domain:   s.Options.Domain,
		Secure:   s.Options.Secure,
		HttpOnly: s.Options.HttpOnly,
	}
	session.IsNew = true
	cookie, e := r.Cookie(name)
	if e != nil {
		return session, e
	}
	e = securecookie.DecodeMulti(name, cookie.Value, &session.ID, s.Codecs...)
	if e != nil {
		return session, e
	}
	e = s.load(session)
	if e != nil {
		return session, e
	} else {
		session.IsNew = false
	}
	return session, nil
}

func (s *MongoStore) Get(r *http.Request, name string) (*sessions.Session, error) {
	return sessions.GetRegistry(r).Get(s, name)
}

func (s *MongoStore) Save(r *http.Request, w http.ResponseWriter, session *sessions.Session) error {
	if session.Options.MaxAge < 0 {
		if e := s.remove(session); e != nil {
			return e
		}
		http.SetCookie(w, sessions.NewCookie(session.Name(), "", session.Options))
	} else {
		if session.ID == "" {
			session.ID = primitive.NewObjectID().Hex()
		}
		if e := s.save(session); e != nil {
			return e
		}
		encoded, e := securecookie.EncodeMulti(session.Name(), session.ID, s.Codecs...)
		if e != nil {
			return e
		}
		http.SetCookie(w, sessions.NewCookie(session.Name(), encoded, session.Options))
	}
	return nil
}

func (s *MongoStore) Close() error {
	ctx, _ := context.WithTimeout(context.Background(), s.dbTimeout)
	return s.client.Disconnect(ctx)
}

func (s *MongoStore) load(session *sessions.Session) error {
	oid, e := primitive.ObjectIDFromHex(session.ID)
	if e != nil {
		return e
	}
	collection := s.client.Database(s.dbDatabaseName).Collection(s.dbCollectionName)
	ctx, _ := context.WithTimeout(context.Background(), s.dbTimeout)
	result := collection.FindOne(ctx, bson.M{"_id": oid})
	ns := new(Session)
	if e := result.Decode(ns); e != nil {
		return e
	}
	if e := securecookie.DecodeMulti(session.Name(), ns.Data, &session.Values, s.Codecs...); e != nil {
		return e
	}
	return nil
}

func (s *MongoStore) save(session *sessions.Session) error {
	oid, e := primitive.ObjectIDFromHex(session.ID)
	if e != nil {
		return e
	}
	collection := s.client.Database(s.dbDatabaseName).Collection(s.dbCollectionName)
	ctx, _ := context.WithTimeout(context.Background(), s.dbTimeout)

	var modified time.Time
	if val, ok := session.Values["modified"]; ok {
		modified, ok = val.(time.Time)
		if !ok {
			return errors.New("mongostore: invalid modified value")
		}
	} else {
		modified = time.Now()
	}
	encoded, e := securecookie.EncodeMulti(session.Name(), session.Values, s.Codecs...)
	if e != nil {
		return e
	}
	ns := new(Session)
	ns.ID = oid
	ns.Data = encoded
	ns.Modified = modified
	if session.IsNew {
		if _, e := collection.InsertOne(ctx, ns); e != nil {
			return e
		}
	} else {
		if _, e := collection.ReplaceOne(ctx, bson.M{"_id": oid}, ns); e != nil {
			return e
		}
	}
	return nil
}

func (s *MongoStore) remove(session *sessions.Session) error {
	oid, e := primitive.ObjectIDFromHex(session.ID)
	if e != nil {
		return e
	}
	collection := s.client.Database(s.dbDatabaseName).Collection(s.dbCollectionName)
	ctx, _ := context.WithTimeout(context.Background(), s.dbTimeout)
	dr, e := collection.DeleteOne(ctx, bson.M{"_id": oid})
	if e != nil {
		return e
	}
	if dr.DeletedCount != 1 {
		return errors.New(fmt.Sprintf("DeletedCount (%d) != 1", dr.DeletedCount))
	}
	return nil
}