//
//  rhimportd
//
//  The Radio Helsinki Rivendell Import Daemon
//
//
//  Copyright (C) 2015-2016 Christian Pointner <equinox@helsinki.at>
//
//  This file is part of rhimportd.
//
//  rhimportd is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  any later version.
//
//  rhimportd is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with rhimportd. If not, see <http://www.gnu.org/licenses/>.
//

package rhimport

import (
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"net/http"
	"time"

	"code.helsinki.at/rhrd-go/rddb"
)

type newSessionResponse struct {
	id           string
	session      *SessionChan
	responsecode int
	errorstring  string
}

type newSessionRequest struct {
	ctx      *Context
	refId    string
	response chan newSessionResponse
}

type getSessionResponse struct {
	session      *SessionChan
	refId        string
	responsecode int
	errorstring  string
}

type getSessionRequest struct {
	user     string
	id       string
	refId    string
	response chan getSessionResponse
}

type SessionsUpdateCB func(added, removed map[string]string, userdata interface{}) bool

type SessionsListCB struct {
	cb       SessionsUpdateCB
	userdata interface{}
}

type listSessionsResponse struct {
	sessions     map[string]string
	responsecode int
	errorstring  string
}

type listSessionsRequest struct {
	user     string
	password string
	trusted  bool
	callback SessionsUpdateCB
	userdata interface{}
	response chan listSessionsResponse
}

type removeSessionResponse struct {
	responsecode int
	errorstring  string
}

type removeSessionRequest struct {
	user     string
	id       string
	response chan removeSessionResponse
}

type SessionStoreSessionElement struct {
	s     *Session
	refId string
}

type SessionStoreUserElement struct {
	sessions  map[string]*SessionStoreSessionElement
	updateCBs []SessionsListCB
}

func (user *SessionStoreUserElement) callUpdateHandler(added, removed map[string]string) {
	var keptCBs []SessionsListCB
	for _, cb := range user.updateCBs {
		if cb.cb != nil {
			if keep := cb.cb(added, removed, cb.userdata); keep {
				keptCBs = append(keptCBs, cb)
			}
		}
	}
	user.updateCBs = keptCBs
}

func (user *SessionStoreUserElement) callUpdateHandlerAdd(id, refId string) {
	added := make(map[string]string)
	added[id] = refId
	user.callUpdateHandler(added, nil)
}

func (user *SessionStoreUserElement) callUpdateHandlerRemove(id, refId string) {
	removed := make(map[string]string)
	removed[id] = refId
	user.callUpdateHandler(nil, removed)
}

type SessionStore struct {
	store      map[string]*SessionStoreUserElement
	conf       *Config
	db         *rddb.DBChan
	quit       chan bool
	done       chan bool
	newChan    chan newSessionRequest
	getChan    chan getSessionRequest
	listChan   chan listSessionsRequest
	removeChan chan removeSessionRequest
}

func generateSessionId() (string, error) {
	var b [32]byte
	if _, err := rand.Read(b[:]); err != nil {
		return "", err
	}
	return base64.RawStdEncoding.EncodeToString(b[:]), nil
}

func (store *SessionStore) new(ctx *Context, refId string) (resp newSessionResponse) {
	resp.responsecode = http.StatusOK
	resp.errorstring = "OK"
	if !ctx.Trusted {
		if ok, err := store.db.CheckPassword(ctx.UserName, ctx.Password); err != nil {
			resp.responsecode = http.StatusInternalServerError
			resp.errorstring = err.Error()
			return
		} else if !ok {
			resp.responsecode = http.StatusUnauthorized
			resp.errorstring = "invalid username and/or password"
			return
		}
	}
	id, err := generateSessionId()
	if err != nil {
		resp.responsecode = http.StatusInternalServerError
		resp.errorstring = err.Error()
		return
	}

	resp.id = id
	if _, exists := store.store[ctx.UserName]; !exists {
		newuser := &SessionStoreUserElement{}
		newuser.sessions = make(map[string]*SessionStoreSessionElement)
		store.store[ctx.UserName] = newuser
	}
	ctx.conf = store.conf
	ctx.db = store.db
	s := &SessionStoreSessionElement{newSession(ctx, func() { store.GetInterface().Remove(ctx.UserName, resp.id) }), refId}
	store.store[ctx.UserName].sessions[resp.id] = s
	resp.session = store.store[ctx.UserName].sessions[resp.id].s.getInterface()
	rhdl.Printf("SessionStore: created session for '%s' -> %s", ctx.UserName, resp.id)
	store.store[ctx.UserName].callUpdateHandlerAdd(resp.id, refId)
	return
}

func (store *SessionStore) get(username, id string) (resp getSessionResponse) {
	resp.responsecode = http.StatusOK
	resp.errorstring = "OK"

	user, exists := store.store[username]
	if !exists {
		resp.responsecode = http.StatusNotFound
		resp.errorstring = fmt.Sprintf("SessionStore: session '%s/%s' not found", username, id)
		return
	}

	if session, exists := user.sessions[id]; exists {
		resp.session = session.s.getInterface()
		resp.refId = session.refId
		return
	}
	resp.responsecode = http.StatusNotFound
	resp.errorstring = fmt.Sprintf("SessionStore: session '%s/%s' not found", username, id)
	return
}

func (store *SessionStore) list(username, password string, trusted bool, userdata interface{}, cb SessionsUpdateCB) (resp listSessionsResponse) {
	resp.responsecode = http.StatusOK
	resp.errorstring = "OK"
	if !trusted {
		if ok, err := store.db.CheckPassword(username, password); err != nil {
			resp.responsecode = http.StatusInternalServerError
			resp.errorstring = err.Error()
			return
		} else if !ok {
			resp.responsecode = http.StatusUnauthorized
			resp.errorstring = "invalid username and/or password"
			return
		}
	}
	resp.sessions = make(map[string]string)
	if user, exists := store.store[username]; exists {
		for id, e := range user.sessions {
			resp.sessions[id] = e.refId
		}
		if cb != nil {
			user.updateCBs = append(user.updateCBs, SessionsListCB{cb, userdata})
		}
	} else if cb != nil {
		newuser := &SessionStoreUserElement{}
		newuser.sessions = make(map[string]*SessionStoreSessionElement)
		newuser.updateCBs = []SessionsListCB{SessionsListCB{cb, userdata}}
		store.store[username] = newuser
	}
	return
}

func (store *SessionStore) remove(username, id string) (resp removeSessionResponse) {
	resp.responsecode = http.StatusOK
	resp.errorstring = "OK"

	user, exists := store.store[username]
	if !exists {
		resp.responsecode = http.StatusNotFound
		resp.errorstring = fmt.Sprintf("SessionStore: session '%s/%s' not found", username, id)
		return
	}

	if session, exists := user.sessions[id]; exists {
		go session.s.cleanup() // cleanup could take a while -> don't block all the other stuff
		refId := session.refId
		delete(user.sessions, id)
		rhdl.Printf("SessionStore: removed session '%s/%s'", username, id)
		user.callUpdateHandlerRemove(id, refId)

		if len(user.sessions) == 0 && len(user.updateCBs) == 0 {
			delete(store.store, username)
			rhdl.Printf("SessionStore: removed user '%s'", username)
		}
	} else {
		resp.responsecode = http.StatusNotFound
		resp.errorstring = fmt.Sprintf("SessionStore: session '%s/%s' not found", username, id)
	}
	return
}

func (store *SessionStore) maintenanceTask() {
	for name, user := range store.store {
		user.callUpdateHandler(nil, nil)
		if len(user.sessions) == 0 && len(user.updateCBs) == 0 {
			delete(store.store, name)
			rhdl.Printf("SessionStore: removed user '%s'", name)
		}
	}
}

func (store *SessionStore) dispatchRequests() {
	defer func() { store.done <- true }()

	mt := time.NewTicker(1 * time.Minute)
	for {
		select {
		case <-store.quit:
			return
		case <-mt.C:
			store.maintenanceTask()
		case req := <-store.newChan:
			req.response <- store.new(req.ctx, req.refId)
		case req := <-store.getChan:
			req.response <- store.get(req.user, req.id)
		case req := <-store.listChan:
			req.response <- store.list(req.user, req.password, req.trusted, req.userdata, req.callback)
		case req := <-store.removeChan:
			req.response <- store.remove(req.user, req.id)
		}
	}
}

// *********************************************************
// Public Interface

type SessionStoreChan struct {
	newChan    chan<- newSessionRequest
	getChan    chan<- getSessionRequest
	listChan   chan listSessionsRequest
	removeChan chan<- removeSessionRequest
}

func (store *SessionStoreChan) New(ctx *Context, refId string) (string, *SessionChan, int, string) {
	resCh := make(chan newSessionResponse)
	req := newSessionRequest{}
	req.ctx = ctx
	req.refId = refId
	req.response = resCh
	store.newChan <- req

	res := <-resCh
	return res.id, res.session, res.responsecode, res.errorstring
}

func (store *SessionStoreChan) Get(user, id string) (*SessionChan, string, int, string) {
	resCh := make(chan getSessionResponse)
	req := getSessionRequest{}
	req.user = user
	req.id = id
	req.response = resCh
	store.getChan <- req

	res := <-resCh
	return res.session, res.refId, res.responsecode, res.errorstring
}

func (store *SessionStoreChan) List(user, password string, trusted bool, userdata interface{}, cb SessionsUpdateCB) (map[string]string, int, string) {
	resCh := make(chan listSessionsResponse)
	req := listSessionsRequest{}
	req.user = user
	req.password = password
	req.trusted = trusted
	req.response = resCh
	req.callback = cb
	req.userdata = userdata
	store.listChan <- req

	res := <-resCh
	return res.sessions, res.responsecode, res.errorstring
}

func (store *SessionStoreChan) Remove(user, id string) (int, string) {
	resCh := make(chan removeSessionResponse)
	req := removeSessionRequest{}
	req.user = user
	req.id = id
	req.response = resCh
	store.removeChan <- req

	res := <-resCh
	return res.responsecode, res.errorstring
}

func (store *SessionStore) GetInterface() *SessionStoreChan {
	ch := &SessionStoreChan{}
	ch.newChan = store.newChan
	ch.getChan = store.getChan
	ch.listChan = store.listChan
	ch.removeChan = store.removeChan
	return ch
}

func (store *SessionStore) Cleanup() {
	store.quit <- true
	<-store.done
	close(store.quit)
	close(store.done)
	close(store.newChan)
	close(store.getChan)
	close(store.listChan)
	close(store.removeChan)
}

func NewSessionStore(conf *Config, db *rddb.DBChan) (store *SessionStore, err error) {
	store = new(SessionStore)
	store.conf = conf
	store.db = db
	store.quit = make(chan bool, 1)
	store.done = make(chan bool)
	store.store = make(map[string]*SessionStoreUserElement)
	store.newChan = make(chan newSessionRequest, 10)
	store.getChan = make(chan getSessionRequest, 10)
	store.listChan = make(chan listSessionsRequest, 10)
	store.removeChan = make(chan removeSessionRequest, 10)

	go store.dispatchRequests()
	return
}