// mautrix-whatsapp - A Matrix-WhatsApp puppeting bridge.
// Copyright (C) 2021 Tulir Asokan
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"strings"
	"sync/atomic"
	"time"

	"github.com/Rhymen/go-whatsapp"

	"maunium.net/go/mautrix/id"
)

type BridgeErrorCode string

const (
	WANotLoggedIn   BridgeErrorCode = "logged-out"
	WANotConnected  BridgeErrorCode = "wa-not-connected"
	WAConnecting    BridgeErrorCode = "wa-connecting"
	WATimeout       BridgeErrorCode = "wa-timeout"
	WAServerTimeout BridgeErrorCode = "wa-server-timeout"
	WAPingFalse     BridgeErrorCode = "wa-ping-false"
	WAPingError     BridgeErrorCode = "wa-ping-error"
)

var bridgeHumanErrors = map[BridgeErrorCode]string{
	WANotLoggedIn:   "You're not logged into WhatsApp",
	WANotConnected:  "You're not connected to WhatsApp",
	WAConnecting:    "Trying to reconnect to WhatsApp. Please make sure WhatsApp is running on your phone and connected to the internet.",
	WATimeout:       "WhatsApp on your phone is not responding. Please make sure it is running and connected to the internet.",
	WAServerTimeout: "The WhatsApp web servers are not responding. The bridge will try to reconnect.",
	WAPingFalse:     "WhatsApp returned an error, reconnecting. Please make sure WhatsApp is running on your phone and connected to the internet.",
	WAPingError:     "WhatsApp returned an unknown error",
}

type BridgeState struct {
	OK        bool  `json:"ok"`
	Timestamp int64 `json:"timestamp"`
	TTL       int   `json:"ttl"`

	ErrorSource string          `json:"error_source,omitempty"`
	Error       BridgeErrorCode `json:"error,omitempty"`
	Message     string          `json:"message,omitempty"`

	UserID     id.UserID `json:"user_id"`
	RemoteID   string    `json:"remote_id"`
	RemoteName string    `json:"remote_name"`
}

func (pong *BridgeState) fill(user *User) {
	pong.UserID = user.MXID
	pong.RemoteID = strings.TrimSuffix(user.JID, whatsapp.NewUserSuffix)
	pong.RemoteName = fmt.Sprintf("+%s", pong.RemoteID)

	pong.Timestamp = time.Now().Unix()
	if !pong.OK {
		pong.TTL = 60
		pong.ErrorSource = "bridge"
		pong.Message = bridgeHumanErrors[pong.Error]
	} else {
		pong.TTL = 240
	}
}

func (pong *BridgeState) shouldDeduplicate(newPong *BridgeState) bool {
	if pong == nil || pong.OK != newPong.OK || pong.Error != newPong.Error {
		return false
	}
	return pong.Timestamp+int64(pong.TTL/5) > time.Now().Unix()
}

func (user *User) setupAdminTestHooks() {
	if len(user.bridge.Config.Homeserver.StatusEndpoint) == 0 {
		return
	}
	user.Conn.AdminTestHook = func(err error) {
		if errors.Is(err, whatsapp.ErrConnectionTimeout) {
			user.sendBridgeState(BridgeState{Error: WATimeout})
		} else if errors.Is(err, whatsapp.ErrWebsocketKeepaliveFailed) {
			user.sendBridgeState(BridgeState{Error: WAServerTimeout})
		} else if errors.Is(err, whatsapp.ErrPingFalse) {
			user.sendBridgeState(BridgeState{Error: WAPingFalse})
		} else if err == nil {
			user.sendBridgeState(BridgeState{OK: true})
		} else {
			user.sendBridgeState(BridgeState{Error: WAPingError})
		}
	}
	user.Conn.CountTimeoutHook = func(wsKeepaliveErrorCount int) {
		if wsKeepaliveErrorCount > 0 {
			user.sendBridgeState(BridgeState{Error: WAServerTimeout})
		} else {
			user.sendBridgeState(BridgeState{Error: WATimeout})
		}
	}
}

func (user *User) createBridgeStateRequest(ctx context.Context, state *BridgeState) (req *http.Request, err error) {
	var body bytes.Buffer
	if err = json.NewEncoder(&body).Encode(&state); err != nil {
		return nil, fmt.Errorf("failed to encode bridge state JSON: %w", err)
	}

	req, err = http.NewRequestWithContext(ctx, http.MethodPost, user.bridge.Config.Homeserver.StatusEndpoint, &body)
	if err != nil {
		return
	}

	req.Header.Set("Authorization", "Bearer "+user.bridge.Config.AppService.ASToken)
	req.Header.Set("Content-Type", "application/json")
	return
}

func (user *User) sendBridgeState(state BridgeState) {
	if len(user.bridge.Config.Homeserver.StatusEndpoint) == 0 {
		return
	}

	state.fill(user)
	if user.prevBridgeStatus != nil && user.prevBridgeStatus.shouldDeduplicate(&state) {
		return
	}

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	var resp *http.Response
	if req, err := user.createBridgeStateRequest(ctx, &state); err != nil {
		user.log.Warnln("Failed to prepare bridge state update request:", err)
	} else if resp, err = http.DefaultClient.Do(req); err != nil {
		user.log.Warnln("Failed to send bridge state update:", err)
	} else if resp.StatusCode < 200 || resp.StatusCode > 299 {
		respBody, _ := ioutil.ReadAll(resp.Body)
		if respBody != nil {
			respBody = bytes.ReplaceAll(respBody, []byte("\n"), []byte("\\n"))
		}
		user.log.Warnfln("Unexpected status code %d sending bridge state update: %s", resp.StatusCode, respBody)
	} else {
		user.prevBridgeStatus = &state
		user.log.Debugfln("Sent new bridge state %+v", state)
	}
	if resp != nil && resp.Body != nil {
		_ = resp.Body.Close()
	}
}

var bridgeStatePingID uint32 = 0

func (prov *ProvisioningAPI) BridgeStatePing(w http.ResponseWriter, r *http.Request) {
	if !prov.bridge.AS.CheckServerToken(w, r) {
		return
	}
	userID := r.URL.Query().Get("user_id")
	user := prov.bridge.GetUserByMXID(id.UserID(userID))
	var resp BridgeState
	if user.Conn == nil {
		if user.Session == nil {
			resp.Error = WANotLoggedIn
		} else {
			resp.Error = WANotConnected
		}
	} else {
		if user.Conn.IsConnected() && user.Conn.IsLoggedIn() {
			pingID := atomic.AddUint32(&bridgeStatePingID, 1)
			user.log.Debugfln("Pinging WhatsApp mobile due to bridge status /ping API request (ID %d)", pingID)
			err := user.Conn.AdminTestWithSuppress(true)
			if errors.Is(r.Context().Err(), context.Canceled) {
				user.log.Warnfln("Ping request %d was canceled before we responded (response was %v)", pingID, err)
				user.prevBridgeStatus = nil
				return
			}
			user.log.Debugfln("Ping %d response: %v", pingID, err)
			if err == whatsapp.ErrPingFalse {
				user.log.Debugln("Forwarding ping false error from provisioning API to HandleError")
				go user.HandleError(err)
				resp.Error = WAPingFalse
			} else if errors.Is(err, whatsapp.ErrConnectionTimeout) {
				resp.Error = WATimeout
			}else if errors.Is(err, whatsapp.ErrWebsocketKeepaliveFailed) {
				resp.Error = WAServerTimeout
			} else if err != nil {
				resp.Error = WAPingError
			} else {
				resp.OK = true
			}
		} else if user.Conn.IsLoginInProgress() {
			resp.Error = WAConnecting
		} else if user.Conn.IsConnected() {
			resp.Error = WANotLoggedIn
		} else {
			resp.Error = WANotConnected
		}
	}
	resp.fill(user)
	user.log.Debugfln("Responding bridge state in bridge status endpoint: %+v", resp)
	jsonResponse(w, http.StatusOK, &resp)
	user.prevBridgeStatus = &resp
}