// Copyright 2021-2022 EMQ Technologies Co., Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package server

import (
	"encoding/json"
	"fmt"
	"github.com/gorilla/handlers"
	"github.com/gorilla/mux"
	"github.com/lf-edge/ekuiper/internal/server/middleware"
	"github.com/lf-edge/ekuiper/pkg/api"
	"github.com/lf-edge/ekuiper/pkg/ast"
	"github.com/lf-edge/ekuiper/pkg/errorx"
	"github.com/lf-edge/ekuiper/pkg/infra"
	"io"
	"io/ioutil"
	"net/http"
	"runtime"
	"strings"
	"time"
)

const (
	ContentType     = "Content-Type"
	ContentTypeJSON = "application/json"
)

type statementDescriptor struct {
	Sql string `json:"sql,omitempty"`
}

func decodeStatementDescriptor(reader io.ReadCloser) (statementDescriptor, error) {
	sd := statementDescriptor{}
	err := json.NewDecoder(reader).Decode(&sd)
	// Problems decoding
	if err != nil {
		return sd, fmt.Errorf("Error decoding the statement descriptor: %v", err)
	}
	return sd, nil
}

// Handle applies the specified error and error concept tot he HTTP response writer
func handleError(w http.ResponseWriter, err error, prefix string, logger api.Logger) {
	message := prefix
	if message != "" {
		message += ": "
	}
	message += err.Error()
	logger.Error(message)
	var ec int
	switch e := err.(type) {
	case *errorx.Error:
		switch e.Code() {
		case errorx.NOT_FOUND:
			ec = http.StatusNotFound
		default:
			ec = http.StatusBadRequest
		}
	default:
		ec = http.StatusBadRequest
	}
	http.Error(w, message, ec)
}

func jsonResponse(i interface{}, w http.ResponseWriter, logger api.Logger) {
	w.Header().Add(ContentType, ContentTypeJSON)
	enc := json.NewEncoder(w)
	err := enc.Encode(i)
	// Problems encoding
	if err != nil {
		handleError(w, err, "", logger)
	}
}

func createRestServer(ip string, port int, needToken bool) *http.Server {
	r := mux.NewRouter()
	r.HandleFunc("/", rootHandler).Methods(http.MethodGet, http.MethodPost)
	r.HandleFunc("/ping", pingHandler).Methods(http.MethodGet)
	r.HandleFunc("/streams", streamsHandler).Methods(http.MethodGet, http.MethodPost)
	r.HandleFunc("/streams/{name}", streamHandler).Methods(http.MethodGet, http.MethodDelete, http.MethodPut)
	r.HandleFunc("/tables", tablesHandler).Methods(http.MethodGet, http.MethodPost)
	r.HandleFunc("/tables/{name}", tableHandler).Methods(http.MethodGet, http.MethodDelete, http.MethodPut)
	r.HandleFunc("/rules", rulesHandler).Methods(http.MethodGet, http.MethodPost)
	r.HandleFunc("/rules/{name}", ruleHandler).Methods(http.MethodDelete, http.MethodGet, http.MethodPut)
	r.HandleFunc("/rules/{name}/status", getStatusRuleHandler).Methods(http.MethodGet)
	r.HandleFunc("/rules/{name}/start", startRuleHandler).Methods(http.MethodPost)
	r.HandleFunc("/rules/{name}/stop", stopRuleHandler).Methods(http.MethodPost)
	r.HandleFunc("/rules/{name}/restart", restartRuleHandler).Methods(http.MethodPost)
	r.HandleFunc("/rules/{name}/topo", getTopoRuleHandler).Methods(http.MethodGet)

	// Register extended routes
	for k, v := range components {
		logger.Infof("register rest endpoint for component %s", k)
		v.rest(r)
	}

	if needToken {
		r.Use(middleware.Auth)
	}

	server := &http.Server{
		Addr: fmt.Sprintf("%s:%d", ip, port),
		// Good practice to set timeouts to avoid Slowloris attacks.
		WriteTimeout: time.Second * 60 * 5,
		ReadTimeout:  time.Second * 60 * 5,
		IdleTimeout:  time.Second * 60,
		Handler:      handlers.CORS(handlers.AllowedHeaders([]string{"Accept", "Accept-Language", "Content-Type", "Content-Language", "Origin", "Authorization"}), handlers.AllowedMethods([]string{"POST", "GET", "PUT", "DELETE", "HEAD"}))(r),
	}
	server.SetKeepAlivesEnabled(false)
	return server
}

type information struct {
	Version       string `json:"version"`
	Os            string `json:"os"`
	Arch          string `json:"arch"`
	UpTimeSeconds int64  `json:"upTimeSeconds"`
}

//The handler for root
func rootHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	switch r.Method {
	case http.MethodGet, http.MethodPost:
		w.WriteHeader(http.StatusOK)
		info := new(information)
		info.Version = version
		info.UpTimeSeconds = time.Now().Unix() - startTimeStamp
		info.Os = runtime.GOOS
		info.Arch = runtime.GOARCH
		byteInfo, _ := json.Marshal(info)
		w.Write(byteInfo)
	}
}

func pingHandler(w http.ResponseWriter, _ *http.Request) {
	w.WriteHeader(http.StatusOK)
}

func sourcesManageHandler(w http.ResponseWriter, r *http.Request, st ast.StreamType) {
	defer r.Body.Close()
	switch r.Method {
	case http.MethodGet:
		content, err := streamProcessor.ShowStream(st)
		if err != nil {
			handleError(w, err, fmt.Sprintf("%s command error", strings.Title(ast.StreamTypeMap[st])), logger)
			return
		}
		jsonResponse(content, w, logger)
	case http.MethodPost:
		v, err := decodeStatementDescriptor(r.Body)
		if err != nil {
			handleError(w, err, "Invalid body", logger)
			return
		}
		content, err := streamProcessor.ExecStreamSql(v.Sql)
		if err != nil {
			handleError(w, err, fmt.Sprintf("%s command error", strings.Title(ast.StreamTypeMap[st])), logger)
			return
		}
		w.WriteHeader(http.StatusCreated)
		w.Write([]byte(content))
	}
}

func sourceManageHandler(w http.ResponseWriter, r *http.Request, st ast.StreamType) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	switch r.Method {
	case http.MethodGet:
		content, err := streamProcessor.DescStream(name, st)
		if err != nil {
			handleError(w, err, fmt.Sprintf("describe %s error", ast.StreamTypeMap[st]), logger)
			return
		}
		jsonResponse(content, w, logger)
	case http.MethodDelete:
		content, err := streamProcessor.DropStream(name, st)
		if err != nil {
			handleError(w, err, fmt.Sprintf("delete %s error", ast.StreamTypeMap[st]), logger)
			return
		}
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(content))
	case http.MethodPut:
		v, err := decodeStatementDescriptor(r.Body)
		if err != nil {
			handleError(w, err, "Invalid body", logger)
			return
		}
		content, err := streamProcessor.ExecReplaceStream(name, v.Sql, st)
		if err != nil {
			handleError(w, err, fmt.Sprintf("%s command error", strings.Title(ast.StreamTypeMap[st])), logger)
			return
		}
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(content))
	}
}

//list or create streams
func streamsHandler(w http.ResponseWriter, r *http.Request) {
	sourcesManageHandler(w, r, ast.TypeStream)
}

//describe or delete a stream
func streamHandler(w http.ResponseWriter, r *http.Request) {
	sourceManageHandler(w, r, ast.TypeStream)
}

//list or create tables
func tablesHandler(w http.ResponseWriter, r *http.Request) {
	sourcesManageHandler(w, r, ast.TypeTable)
}

func tableHandler(w http.ResponseWriter, r *http.Request) {
	sourceManageHandler(w, r, ast.TypeTable)
}

//list or create rules
func rulesHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	switch r.Method {
	case http.MethodPost:
		body, err := ioutil.ReadAll(r.Body)
		if err != nil {
			handleError(w, err, "Invalid body", logger)
			return
		}
		r, err := ruleProcessor.ExecCreate("", string(body))
		var result string
		if err != nil {
			handleError(w, err, "Create rule error", logger)
			return
		} else {
			result = fmt.Sprintf("Rule %s was created successfully.", r.Id)
		}
		go func() {
			panicOrError := infra.SafeRun(func() error {
				//Start the rule
				rs, err := createRuleState(r)
				if err != nil {
					return err
				} else {
					err = doStartRule(rs)
					return err
				}
			})
			if panicOrError != nil {
				logger.Errorf("Rule %s start failed: %s", r.Id, panicOrError)
			}
		}()
		w.WriteHeader(http.StatusCreated)
		w.Write([]byte(result))
	case http.MethodGet:
		content, err := getAllRulesWithStatus()
		if err != nil {
			handleError(w, err, "Show rules error", logger)
			return
		}
		jsonResponse(content, w, logger)
	}
}

//describe or delete a rule
func ruleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	switch r.Method {
	case http.MethodGet:
		rule, err := ruleProcessor.GetRuleByName(name)
		if err != nil {
			handleError(w, err, "describe rule error", logger)
			return
		}
		jsonResponse(rule, w, logger)
	case http.MethodDelete:
		deleteRule(name)
		content, err := ruleProcessor.ExecDrop(name)
		if err != nil {
			handleError(w, err, "delete rule error", logger)
			return
		}
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(content))
	case http.MethodPut:
		_, err := ruleProcessor.GetRuleByName(name)
		if err != nil {
			handleError(w, err, "not found this rule", logger)
			return
		}

		body, err := ioutil.ReadAll(r.Body)
		if err != nil {
			handleError(w, err, "Invalid body", logger)
			return
		}

		r, err := ruleProcessor.ExecUpdate(name, string(body))
		var result string
		if err != nil {
			handleError(w, err, "Update rule error", logger)
			return
		} else {
			result = fmt.Sprintf("Rule %s was updated successfully.", r.Id)
		}

		err = restartRule(name)
		if err != nil {
			handleError(w, err, "restart rule error", logger)
			return
		}
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(result))
	}
}

//get status of a rule
func getStatusRuleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	content, err := getRuleStatus(name)
	if err != nil {
		handleError(w, err, "get rule status error", logger)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(content))
}

//start a rule
func startRuleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	err := startRule(name)
	if err != nil {
		handleError(w, err, "start rule error", logger)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(fmt.Sprintf("Rule %s was started", name)))
}

//stop a rule
func stopRuleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	result := stopRule(name)
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(result))
}

//restart a rule
func restartRuleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	err := restartRule(name)
	if err != nil {
		handleError(w, err, "restart rule error", logger)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(fmt.Sprintf("Rule %s was restarted", name)))
}

//get topo of a rule
func getTopoRuleHandler(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	vars := mux.Vars(r)
	name := vars["name"]

	content, err := getRuleTopo(name)
	if err != nil {
		handleError(w, err, "get rule topo error", logger)
		return
	}
	w.Header().Set(ContentType, ContentTypeJSON)
	w.Write([]byte(content))
}