// nodegopher is a Grafana/Prometheus nodeGraph helper
// It builds nodegraph structure by merging static data and metrics pulled from prometheus instance
// Copyright (c) 2025 yo000 <johan@nosd.in>
//

package main

import (
	"os"
	"fmt"
	"flag"
	"sync"
	"time"
	"regexp"
	"context"
	"strconv"
	"strings"
	"syscall"
	"net/http"
	"os/signal"

	"gopkg.in/yaml.v2"
	"github.com/spf13/viper"
	"github.com/gin-gonic/gin"
	"github.com/fsnotify/fsnotify"
	log "github.com/sirupsen/logrus"

	"golang.org/x/text/language"
	"golang.org/x/text/message"

	"github.com/prometheus/common/model"
	"github.com/prometheus/client_golang/api"
	v1 "github.com/prometheus/client_golang/api/prometheus/v1"
)

const (
	gVersion = "0.2.3"
)

type PromDataSourceConfig struct {
	Name     string `yaml:"name"`
	QType    string `yaml:"type"`
	Address  string `yaml:"address"`
	Query    string `yaml:"query"`
	Timeout  int    `yaml:"timeout"`
}

type Graph struct {
	Name  string `yaml:"name"`
	Nodes []Item
	Edges []Item
}

type Item interface {
	GetId()                  string
	GetMainStat()            string
	GetMainStatQuery()       string
	GetMainStatFormat()      string
	SetMainStat(string)
	GetSecondaryStat()       string
	GetSecondaryStatQuery()  string
	GetSecondaryStatFormat() string
	SetSecondaryStat(string)
	GetThicknessQuery()      string
	SetThickness(float64)
	GetHighlightedQuery()    string
	SetHighlighted(bool)
}

// Query arguments. Based on grafana internal variables.
type QueryArgs struct {
	From     int64  `form:"from" binding:"required"`
	To       int64  `form:"to" binding:"required"`
	Interval string `form:"interval" binding:"required"`
}

// Query arguments converted to prometheus_client format
type MyRange struct {
	Start     time.Time
	End       time.Time
	Step      time.Duration
}

var (
	gPrinter *message.Printer
	gDebug bool
	gGraphs []Graph
	gDataSources []PromDataSourceConfig

	gDSVarCompRegex       *regexp.Regexp
	gGrafanaIntervalUnitRegex *regexp.Regexp

	// manipulating In-Ram configuration Mutex. reloadConfig will lock WriteMutex, consuming queries will lock ReadMutex.
	gCfgMutex sync.RWMutex
)


func (d *PromDataSourceConfig) GetData(timeRange *MyRange) (float64, error) {
	client, err := api.NewClient(api.Config{
		Address: d.Address,
	})
	if err != nil {
		log.Errorf("DataSourceConfig.GetData: Error creating client: %v\n", err)
		return 0.0, err
	}
	
	v1api := v1.NewAPI(client)
	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(d.Timeout)*time.Second)
	defer cancel()
	var result model.Value
	var warnings v1.Warnings
	if d.QType == "query" {
		result, warnings, err = v1api.Query(ctx, d.Query, time.Now(), v1.WithTimeout(time.Duration(d.Timeout)*time.Second))
	} else if d.QType == "query_range" {
		rng := v1.Range{
			Start: timeRange.Start,
			End:   timeRange.End,
			Step:  timeRange.Step,
		}
		result, warnings, err = v1api.QueryRange(ctx, d.Query, rng, v1.WithTimeout(time.Duration(d.Timeout)*time.Second))
	}
	if err != nil {
		log.Errorf("DataSourceConfig.GetData: Error querying Prometheus: %v\n", err)
		return 0.0, err
	}
	if len(warnings) > 0 {
		log.Warningf("DataSourceConfig.GetData: Warnings: %v\n", warnings)
	}
	//log.Debugf("DataSourceConfig.GetData: Result: %v\n", result)

	switch {
		case result.Type() == model.ValScalar:
			log.Errorf("This is a model.ValScalar type, not implemented!\n")
			//scalarVal := result.(*model.Scalar)
			// handle scalar stuff
		case result.Type() == model.ValVector:
			vectorVal := result.(model.Vector)
			// FIXME: Is averaging the right thing to do?
			var total float64
			for _, elem := range vectorVal {
				log.Debugf("DataSourceConfig.GetData: Value: %v\n", elem.Value)
				total += float64(elem.Value)
			}
			log.Debugf("DataSourceConfig.GetData: Total average: %f\n", total/float64(len(vectorVal)))
			return total/float64(len(vectorVal)), nil
		// QueryRange return this type
		case result.Type() == model.ValMatrix:
			matrixVal := result.(model.Matrix)
			// FIXME: Is averaging the right thing to do?
			var total float64
			var length int64
			for _, val := range matrixVal {
				for _, v := range val.Values {
					total += float64(v.Value)
				}
				length += int64(len(val.Values))
			}
			log.Debugf("DataSourceConfig.GetData: Total average: %f\n", total/float64(length))
			return total/float64(length), nil
		default:
			log.Errorf("Prometheus result is an unknown type: %T", result)
			return 0.0, nil
	}

	return 0.0, nil
}

func (g Graph) BuildMetrics(items *[]Item, timeRange *MyRange) (*[]Item, error) {
	var err error
	
	// Acquire Read Lock. This won't prevent other queries being answered, but reloadConfig WLock will have to wait until we finish
	gCfgMutex.RLock()
	defer gCfgMutex.RUnlock()

	for _, item := range *items {
		// Handle mainStat
		if len(item.GetMainStatQuery()) > 0 {
			log.Debugf("Item %s have mainstatquery: %s\n", item.GetId(), item.GetMainStatQuery())
			r := gDSVarCompRegex.FindStringSubmatch(item.GetMainStatQuery())
			if len(r) > 1 {
				var value float64
				dsname := strings.TrimSpace(r[1])
				log.Debugf("buildMetrics: datasource from mainstatquery : %s\n", dsname)
				for _, d := range gDataSources {
					if strings.EqualFold(d.Name, dsname) {
						value, err = d.GetData(timeRange)
						if err != nil {
							return nil, err
						}
						break
					}
				}
				format := item.GetMainStatFormat()
				if len(format) == 0 {
					format = "%f"
				}
				log.Debugf("buildMetrics: Replace %s mainstat with %s\n", item.GetId(), gPrinter.Sprintf(format, value))
				item.SetMainStat(gPrinter.Sprintf(format, value))
			} else {
				log.Errorf("buildMetrics: Item %s mainstatquery unparseable: %s\n", item.GetId(), item.GetMainStatQuery())
			}
		}
		// Handle secondaryStat
		if len(item.GetSecondaryStatQuery()) > 0 {
			log.Debugf("Item %s have mainstatquery: %s\n", item.GetId(), item.GetSecondaryStatQuery())
			r := gDSVarCompRegex.FindStringSubmatch(item.GetSecondaryStatQuery())
			if len(r) > 1 {
				var value float64
				dsname := strings.TrimSpace(r[1])
				log.Debugf("buildMetrics: datasource from secondarystatquery : %s\n", dsname)
				for _, d := range gDataSources {
					if strings.EqualFold(d.Name, dsname) {
						value, err = d.GetData(timeRange)
						if err != nil {
							return nil, err
						}
						break
					}
				}
				format := item.GetSecondaryStatFormat()
				if len(format) == 0 {
					format = "%f"
				}
				log.Debugf("buildMetrics: Replace %s secondarystat with %s\n", item.GetId(), gPrinter.Sprintf(format, value))
				item.SetSecondaryStat(gPrinter.Sprintf(format, value))
			} else {
				log.Errorf("buildMetrics: Item %s secondarystatquery unparseable: %s\n", item.GetId(), item.GetSecondaryStatQuery())
			}
		}
		// Handle highlighted
		if len(item.GetHighlightedQuery()) > 0 {
			log.Debugf("buildMetrics: Item %s have highlightedquery: %s\n", item.GetId(), item.GetHighlightedQuery())
			r := gDSVarCompRegex.FindStringSubmatch(item.GetHighlightedQuery())
			if len(r) > 1 {
				var value float64
				dsname := strings.TrimSpace(r[1])
				log.Debugf("buildMetrics: datasource from highlightedquery : %s\n", dsname)
				for _, d := range gDataSources {
					if strings.EqualFold(d.Name, dsname) {
						value, err = d.GetData(timeRange)
						if err != nil {
							return nil, err
						}
						break
					}
				}
				highlight := false
				if value == 0 {
					highlight = false
				} else {
					highlight = true
				}
				log.Debugf("buildMetrics: Replace %s highlighted with %t\n", item.GetId(), highlight)
				item.SetHighlighted(highlight)
			} else {
				log.Errorf("buildMetrics: Item %s highlightedquery unparseable: %s\n", item.GetId(), item.GetHighlightedQuery())
			}
		}
		switch item.(type) {
			case *Edge:
				if len(item.GetThicknessQuery()) > 0 {
					log.Debugf("buildMetrics: Item %s have thicknessquery: %s\n", item.GetId(), item.GetThicknessQuery())
					r := gDSVarCompRegex.FindStringSubmatch(item.GetThicknessQuery())
					if len(r) > 1 {
						var value float64
						dsname := strings.TrimSpace(r[1])
						log.Debugf("buildMetrics: datasource from thicknessquery : %s\n", dsname)
						for _, d := range gDataSources {
							if strings.EqualFold(d.Name, dsname) {
								value, err = d.GetData(timeRange)
								if err != nil {
									return nil, err
								}
								break
							}
						}
						log.Debugf("buildMetrics: Replace %s thickness with %s\n", item.GetId(), fmt.Sprintf("%0.0f", value))
						item.SetThickness(value)
					} else {
						log.Errorf("buildMetrics: Item %s thicknessquery unparseable: %s\n", item.GetId(), item.GetThicknessQuery())
					}
				}
		}
	}
	return items, nil
}

func queryArgsToTimeRange(args QueryArgs) (MyRange, error) {
	// interval sent by Grafana could end with : ms, s, m, h, d
	var step time.Duration
	matches := gGrafanaIntervalUnitRegex.FindStringSubmatch(args.Interval)
	if len(matches) != 3 {
		return MyRange{}, fmt.Errorf("Invalid format: interval")
	}
	value, err := strconv.ParseInt(matches[gGrafanaIntervalUnitRegex.SubexpIndex("value")], 10, 64)
	if err != nil {
		return MyRange{}, fmt.Errorf("Invalid format (can not parse value): interval")
	}
	switch matches[gGrafanaIntervalUnitRegex.SubexpIndex("unit")] {
		case "ms":
			step = time.Duration(value)*time.Millisecond
		case "s":
			step = time.Duration(value)*time.Second
		case "m":
			step = time.Duration(value)*time.Minute
		case "h":
			step = time.Duration(value)*time.Hour
		case "d":
			step = time.Duration(value)*time.Hour*24
		default:
			return MyRange{}, fmt.Errorf("Invalid format (can not parse unit): interval")
	}

	return MyRange{Start: time.Unix(args.From/1000, 0), End: time.Unix(args.To/1000, 0), Step: step}, nil
}

func getGraph(name string) (Graph, error) {
	// Acquire Read Lock. This won't prevent other queries being answered, but reloadConfig WLock will have to wait until we finish
	gCfgMutex.RLock()
	defer gCfgMutex.RUnlock()

	for _, g := range gGraphs {
		if strings.EqualFold(g.Name, name) {
			return g, nil
		}
	}
	return Graph{}, fmt.Errorf("Graph not found: %s", name)
}

func initRoutes(r *gin.Engine) {
	r.GET("/ping", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{
			"message": "pong",
		})
	})
	
	// An endpoint to force read of configuration file
	r.POST("/reload", func(c *gin.Context) {
		reloadConfigFile()
		c.JSON(http.StatusOK, gin.H{
			"message": "configuration successfully reloaded",
		})
	})
	
	// An endpoint to toggle debug mode
	r.POST("/debug", func(c *gin.Context) {
		toggleDebug()
		if gDebug {
			c.JSON(http.StatusOK, gin.H{
				"message": "debug mode enabled",
			})
		} else {
			c.JSON(http.StatusOK, gin.H{
				"message": "debug mode disabled",
			})
		}
	})
	
	r.GET("/:graph/nodes", func(c *gin.Context) {
		// Validate presence and type
		var args QueryArgs
		if err := c.ShouldBindQuery(&args); err != nil {
			log.Errorf("Invalid query arguments\n")
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		timeRange, err := queryArgsToTimeRange(args)
		if err != nil {
			log.Errorf("Unable to parse query arguments\n")
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		gName := c.Param("graph")
		graph, err := getGraph(gName)
		if err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
			return
		}

		nodes, err := graph.BuildMetrics(&graph.Nodes, &timeRange)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		}
		c.JSON(http.StatusOK, nodes)
	})
	
	r.GET("/:graph/edges", func(c *gin.Context) {
		// Validate presence and type
		var args QueryArgs
		if err := c.ShouldBindQuery(&args); err != nil {
			log.Errorf("Invalid query arguments\n")
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		timeRange, err := queryArgsToTimeRange(args)
		if err != nil {
			log.Errorf("Unable to parse query arguments\n")
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		gName := c.Param("graph")
		graph, err := getGraph(gName)
		if err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
			return
		}

		edges, err := graph.BuildMetrics(&graph.Edges, &timeRange)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		}
		c.JSON(http.StatusOK, edges)
	})
}

func toggleDebug() {
	if gDebug {
		gin.SetMode(gin.ReleaseMode)
		log.SetLevel(log.InfoLevel)
		gDebug = false
	} else {
		gin.SetMode(gin.DebugMode)
		log.SetLevel(log.DebugLevel)
		gDebug = true
	}
}

func reloadConfigFile() {
	// First reread config file
	if err := viper.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
			log.Fatalf("config file not found")
			os.Exit(1)
		} else {
			log.Fatalf("unknown error looking for config file: %v", err)
			os.Exit(1)
		}
	}

	switch viper.Get("language").(string) {
		case "english":
			gPrinter = message.NewPrinter(language.English)
		case "french":
			gPrinter = message.NewPrinter(language.French)
		case "german":
			gPrinter = message.NewPrinter(language.German)
		case "ukrainian":
			gPrinter = message.NewPrinter(language.Ukrainian)
		case "arabic":
			gPrinter = message.NewPrinter(language.Arabic)
		case "chinese":
			gPrinter = message.NewPrinter(language.Chinese)
		default:
			log.Errorf("Language not implented: %s. Fallback to english\n", viper.Get("language").(string))
			gPrinter = message.NewPrinter(language.English)
	}

	// then clear current config, after acquiring WriteLock
	gCfgMutex.Lock()
	defer gCfgMutex.Unlock()

	for _, g := range gGraphs {
		g.Nodes = nil
		g.Edges = nil
	}
	gGraphs = nil
	gDataSources = nil

	// Finally unmarshal graphs, nodes, edges and datasources
	gps := viper.Get("graphs").([]interface{})
	for _, g := range gps {
		yd, _ := yaml.Marshal(g)
		// Unmarshal on anonymous structs with []Edge and []Node well defined so unmarshaler know how to handle
		//  then we convert to []Items
		tmp := struct {
			Name  string `yaml:"name"`
			Nodes []Node `yaml:"nodes"`
			Edges []Edge `yaml:"edges"`
		}{}
		yaml.Unmarshal(yd, &tmp)
		var graphNodes []Item
		var graphEdges []Item
		for _, n := range tmp.Nodes {
			graphNodes = append(graphNodes, &n)
		}
		for _, e := range tmp.Edges {
			graphEdges = append(graphEdges, &e)
		}
		
		graph := Graph{
			Name:  tmp.Name,
			Nodes: graphNodes,
			Edges: graphEdges,
		}
		gGraphs = append(gGraphs, graph)
	}

	if viper.Get("datasources") == nil {
		log.Printf("no datasources found, data will be static")
		return
	}
	dss := viper.Get("datasources").([]interface{})
	for _, d := range dss {
		yd, _ := yaml.Marshal(d)
		var ds PromDataSourceConfig
		yaml.Unmarshal(yd, &ds)
		gDataSources = append(gDataSources, ds)
	}
}

func main() {
	var listen string
	var confFile string

	flag.StringVar(&confFile, "config", "", "Path to the config file")
	flag.StringVar(&listen, "listen-addr", "0.0.0.0:8080", "listen address for server")
	flag.BoolVar(&gDebug, "debug", false, "Set log level to debug")
	flag.Parse()

	if len(confFile) == 0 {
		log.Fatalf("config is mandatory")
		os.Exit(1)
	}

	viper.SetConfigFile(confFile)
	if err := viper.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
			log.Fatalf("config file not found")
			os.Exit(1)
		} else {
			log.Fatalf("unknown error looking for config file: %v", err)
			os.Exit(1)
		}
	}

	if false == gDebug {
		b := viper.GetBool("debug")
		if b {
			gDebug = b
		}
	}

	if gDebug {
		gin.SetMode(gin.DebugMode)
		log.SetLevel(log.DebugLevel)
	} else {
		log.SetLevel(log.InfoLevel)
		gin.SetMode(gin.ReleaseMode)
	}

	if strings.EqualFold(listen, "0.0.0.0:8080") && len(confFile) > 0 {
		l := viper.GetString("listen")
		if len(l) > 0 {
			listen = l
		}
	}

	// FIXME: Watch config changes. Does not work on FreeBSD. TODO: Test with linux
	viper.OnConfigChange(func(e fsnotify.Event) {
		log.Printf("Config file changed, reloading data\n")
		reloadConfigFile()
	})

	// Lets reload config on SIGHUP
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, syscall.SIGHUP)
	go func() {
		for {
			_ = <- sigs
			log.Infof("SIGHUP received, reloading configuration\n")
			reloadConfigFile()
		}
	}()

	reloadConfigFile()

	// Capture variable name. There should be only one variable. Space is tolerated before and after name.
	gDSVarCompRegex = regexp.MustCompile(`^\{\{(?:\ )?([a-zA-Z0-9\-_]+)(?:\ )?\}\}$`)

	// Grafana interval parser
	gGrafanaIntervalUnitRegex = regexp.MustCompile(`^(?P<value>[0-9]+)(?P<unit>[mshd]+)$`)

	log.Printf("Starting NodeGopher v.%s\n", gVersion)

	r := gin.Default()
	initRoutes(r)
	r.Run(listen)
}