/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 plugin

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/grafana/grafana-plugin-sdk-go/backend"
	"github.com/grafana/grafana-plugin-sdk-go/backend/instancemgmt"
	"github.com/grafana/grafana-plugin-sdk-go/backend/log"
	"github.com/grafana/grafana-plugin-sdk-go/data"
)

// Make sure IoTDBDatasource implements required interfaces. This is important to do
// since otherwise we will only get a not implemented error response from plugin in
// runtime. In this example datasource instance implements backend.QueryDataHandler,
// backend.CheckHealthHandler, backend.StreamHandler interfaces. Plugin should not
// implement all these interfaces - only those which are required for a particular task.
// For example if plugin does not need streaming functionality then you are free to remove
// methods that implement backend.StreamHandler. Implementing instancemgmt.InstanceDisposer
// is useful to clean up resources used by previous datasource instance when a new datasource
// instance created upon datasource settings changed.
var (
	_ backend.QueryDataHandler      = (*IoTDBDataSource)(nil)
	_ backend.CheckHealthHandler    = (*IoTDBDataSource)(nil)
	_ backend.StreamHandler         = (*IoTDBDataSource)(nil)
	_ instancemgmt.InstanceDisposer = (*IoTDBDataSource)(nil)
)

// NewSampleDatasource creates a new datasource instance.
func NewSampleDatasource(d backend.DataSourceInstanceSettings) (instancemgmt.Instance, error) {
	var dm dataSourceModel
	if err := json.Unmarshal(d.JSONData, &dm); err != nil {
		return nil, err
	}
	return &IoTDBDataSource{Username: dm.Username, Password: dm.Password, Ulr: dm.Url}, nil
}

// SampleDatasource is an example datasource which can respond to data queries, reports
// its health and has streaming skills.
type IoTDBDataSource struct {
	Password string
	Username string
	Ulr      string
}

// Dispose here tells plugin SDK that plugin wants to clean up resources when a new instance
// created. As soon as datasource settings change detected by SDK old datasource instance will
// be disposed and a new one will be created using NewSampleDatasource factory function.
func (d *IoTDBDataSource) Dispose() {
	// Clean up datasource instance resources.
}

// QueryData handles multiple queries and returns multiple responses.
// req contains the queries []DataQuery (where each query contains RefID as a unique identifier).
// The QueryDataResponse contains a map of RefID to the response for each query, and each response
// contains Frames ([]*Frame).
func (d *IoTDBDataSource) QueryData(ctx context.Context, req *backend.QueryDataRequest) (*backend.QueryDataResponse, error) {
	log.DefaultLogger.Info("QueryData called", "request", req)
	// create response struct
	response := backend.NewQueryDataResponse()

	// loop over queries and execute them individually.
	for _, q := range req.Queries {
		res := d.query(ctx, req.PluginContext, q)

		// save the response in a hashmap
		// based on with RefID as identifier
		response.Responses[q.RefID] = res
	}

	return response, nil
}

type dataSourceModel struct {
	Username string `json:"username"`
	Password string `json:"password"`
	Url      string `json:"url"`
}

type groupBy struct {
	GroupByLevel     string `json:"groupByLevel"`
	SamplingInterval string `json:"samplingInterval"`
	Step             string `json:"step"`
}

type queryParam struct {
	Expression   []string `json:"expression"`
	PrefixPath   []string `json:"prefixPath"`
	StartTime    int64    `json:"startTime"`
	EndTime      int64    `json:"endTime"`
	Condition    string   `json:"condition"`
	Control      string   `json:"control"`
	Aggregated   string   `json:"aggregated"`
	Paths        []string `json:"paths"`
	AggregateFun string   `json:"aggregateFun"`
	FillClauses  string   `json:"fillClauses"`
	GroupBy      groupBy  `json:"groupBy"`
}

type QueryDataReq struct {
	Expression []string `json:"expression"`
	PrefixPath []string `json:"prefixPath"`
	StartTime  int64    `json:"startTime"`
	EndTime    int64    `json:"endTime"`
	Condition  string   `json:"condition"`
	Control    string   `json:"control"`
}

type QueryDataResponse struct {
	Expressions []string    `json:"expressions"`
	Timestamps  []int64     `json:"timestamps"`
	Values      [][]float32 `json:"values"`
	ColumnNames interface{} `json:"columnNames"`
	Code        int32       `json:"code"`
	Message     string      `json:"message"`
}

type loginStatus struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

func NewQueryDataReq(expression []string, prefixPath []string, startTime int64, endTime int64, condition string, control string) *QueryDataReq {
	return &QueryDataReq{Expression: expression, PrefixPath: prefixPath, StartTime: startTime, EndTime: endTime, Condition: condition, Control: control}
}

func (d *IoTDBDataSource) query(cxt context.Context, pCtx backend.PluginContext, query backend.DataQuery) backend.DataResponse {
	response := backend.DataResponse{}
	var authorization = "Basic " + base64.StdEncoding.EncodeToString([]byte(d.Username+":"+d.Password))

	// Unmarshal the JSON into our queryModel.
	var qp queryParam
	var qdReq QueryDataReq
	response.Error = json.Unmarshal(query.JSON, &qp)
	if response.Error != nil {
		return response
	}
	qp.StartTime = query.TimeRange.From.UnixNano() / 1000000
	qp.EndTime = query.TimeRange.To.UnixNano() / 1000000

	client := &http.Client{}
	if qp.Aggregated == "Aggregation" {
		qp.Control = ""
		var expressions []string = qp.Paths[len(qp.Paths)-1:]
		var paths []string = qp.Paths[0 : len(qp.Paths)-1]
		path := "root." + strings.Join(paths, ".")
		var prefixPaths = []string{path}
		if qp.AggregateFun != "" {
			expressions[0] = qp.AggregateFun + "(" + expressions[0] + ")"
		}
		if qp.GroupBy.SamplingInterval != "" && qp.GroupBy.Step == "" {
			qp.Control += " group by([" + strconv.FormatInt(qp.StartTime, 10) + "," + strconv.FormatInt(qp.EndTime, 10) + ")," + qp.GroupBy.SamplingInterval + ")"
		}
		if qp.GroupBy.SamplingInterval != "" && qp.GroupBy.Step != "" {
			qp.Control += " group by([" + strconv.FormatInt(qp.StartTime, 10) + "," + strconv.FormatInt(qp.EndTime, 10) + ")," + qp.GroupBy.SamplingInterval + "," + qp.GroupBy.Step + ")"
		}
		if qp.GroupBy.GroupByLevel != "" {
			qp.Control += " " + qp.GroupBy.GroupByLevel
		}
		if qp.FillClauses != "" {
			qp.Control += " fill" + qp.FillClauses
		}
		qdReq = *NewQueryDataReq(expressions, prefixPaths, qp.StartTime, qp.EndTime, qp.Condition, qp.Control)
	} else {
		qdReq = *NewQueryDataReq(qp.Expression, qp.PrefixPath, qp.StartTime, qp.EndTime, qp.Condition, qp.Control)
	}
	qpJson, _ := json.Marshal(qdReq)
	reader := bytes.NewReader(qpJson)

	var dataSourceUrl = DataSourceUrlHandler(d.Ulr)

	request, _ := http.NewRequest(http.MethodPost, dataSourceUrl+"/grafana/v1/query/expression", reader)
	request.Header.Set("Content-Type", "application/json")
	request.Header.Add("Authorization", authorization)

	rsp, _ := client.Do(request)
	body, err := io.ReadAll(rsp.Body)
	if err != nil {
		log.DefaultLogger.Error("Data source is not working properly", err)
	}

	var queryDataResp QueryDataResponse
	err = json.Unmarshal(body, &queryDataResp)
	if err != nil {
		log.DefaultLogger.Error("Parsing JSON error", err)
	}

	defer rsp.Body.Close()
	if queryDataResp.Code > 0 {
		response.Error = errors.New(queryDataResp.Message)
		log.DefaultLogger.Error(queryDataResp.Message)

	}
	// create data frame response.
	frame := data.NewFrame("response")
	for i := 0; i < len(queryDataResp.Expressions); i++ {
		times := make([]time.Time, len(queryDataResp.Timestamps))
		values := make([]float32, len(queryDataResp.Timestamps))
		for c := 0; c < len(queryDataResp.Timestamps); c++ {
			times[c] = time.Unix(queryDataResp.Timestamps[c]/1000, 0)
			values[c] = queryDataResp.Values[i][c]
		}
		frame.Fields = append(frame.Fields,
			data.NewField("time", nil, times),
			data.NewField(queryDataResp.Expressions[i], nil, values),
		)
	}

	response.Frames = append(response.Frames, frame)
	return response
}

// Whether the last character of the URL for processing datasource configuration is "/"
func DataSourceUrlHandler(url string) string {
	var lastCharacter = url[len(url)-1 : len(url)]
	if lastCharacter == "/" {
		url = url[0 : len(url)-1]
	}
	return url
}

// CheckHealth handles health checks sent from Grafana to the plugin.
// The main use case for these health checks is the test button on the
// datasource configuration page which allows users to verify that
// a datasource is working as expected.
func (d *IoTDBDataSource) CheckHealth(_ context.Context, req *backend.CheckHealthRequest) (*backend.CheckHealthResult, error) {
	log.DefaultLogger.Info("CheckHealth called", "request", req)
	var authorization = "Basic " + base64.StdEncoding.EncodeToString([]byte(d.Username+":"+d.Password))
	var status = backend.HealthStatusError
	var message = "Data source is not working properly"

	var dataSourceUrl = DataSourceUrlHandler(d.Ulr)

	client := &http.Client{}
	request, err := http.NewRequest(http.MethodGet, dataSourceUrl+"/grafana/v1/login", nil)
	if err != nil {
		panic(err)
	}
	request.Header.Add("Authorization", authorization)

	response, _ := client.Do(request)
	body, err := io.ReadAll(response.Body)
	if err != nil {
		log.DefaultLogger.Error("Data source is not working properly", err)
	}

	var loginStatus loginStatus
	err = json.Unmarshal(body, &loginStatus)
	if err != nil {
		log.DefaultLogger.Error("Parsing JSON error", err)
	} else if loginStatus.Code == 200 {
		status = backend.HealthStatusOk
		message = loginStatus.Message
	}

	defer response.Body.Close()

	return &backend.CheckHealthResult{
		Status:  status,
		Message: message,
	}, nil
}

// SubscribeStream is called when a client wants to connect to a stream. This callback
// allows sending the first message.
func (d *IoTDBDataSource) SubscribeStream(_ context.Context, req *backend.SubscribeStreamRequest) (*backend.SubscribeStreamResponse, error) {
	log.DefaultLogger.Info("SubscribeStream called", "request", req)

	status := backend.SubscribeStreamStatusPermissionDenied
	if req.Path == "stream" {
		// Allow subscribing only on expected path.
		status = backend.SubscribeStreamStatusOK
	}

	return &backend.SubscribeStreamResponse{
		Status: status,
	}, nil
}

// RunStream is called once for any open channel.  Results are shared with everyone
// subscribed to the same channel.
func (d *IoTDBDataSource) RunStream(ctx context.Context, req *backend.RunStreamRequest, sender *backend.StreamSender) error {
	log.DefaultLogger.Info("RunStream called", "request", req)

	// Create the same data frame as for query data.
	frame := data.NewFrame("response")

	// Add fields (matching the same schema used in QueryData).
	frame.Fields = append(frame.Fields,
		data.NewField("time", nil, make([]time.Time, 1)),
		data.NewField("values", nil, make([]int64, 1)),
	)

	counter := 0

	// Stream data frames periodically till stream closed by Grafana.
	for {
		select {
		case <-ctx.Done():
			log.DefaultLogger.Info("Context done, finish streaming", "path", req.Path)
			return nil
		case <-time.After(time.Second):
			// Send new data periodically.
			frame.Fields[0].Set(0, time.Now())
			frame.Fields[1].Set(0, int64(10*(counter%2+1)))

			counter++

			err := sender.SendFrame(frame, data.IncludeAll)
			if err != nil {
				log.DefaultLogger.Error("Error sending frame", "error", err)
				continue
			}
		}
	}
}

// PublishStream is called when a client sends a message to the stream.
func (d *IoTDBDataSource) PublishStream(_ context.Context, req *backend.PublishStreamRequest) (*backend.PublishStreamResponse, error) {
	log.DefaultLogger.Info("PublishStream called", "request", req)

	// Do not allow publishing at all.
	return &backend.PublishStreamResponse{
		Status: backend.PublishStreamStatusPermissionDenied,
	}, nil
}