edas/main.go

package main

import (
	"context"
	"github.com/fsnotify/fsnotify"
	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"
	"github.com/urfave/cli/v3"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"strings"
)

var upgrader = websocket.Upgrader{CheckOrigin: func(r *http.Request) bool { return true }}
var previousLine = make(map[string]int)

func main() {
	cmd := &cli.Command{
		Name:  "edas",
		Usage: "an api for reading data from elite dangerous",
		Flags: []cli.Flag{
			&cli.StringFlag{Name: "path", Value: "%USERPROFILE%\\Saved Games\\Frontier Developments\\Elite Dangerous"},
		},
		Action: func(ctx context.Context, cmd *cli.Command) error {
			r := gin.Default()

			/* These are all the routes that just serve json data straight from the files. */
			r.GET("/backpack", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Backpack.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/cargo", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Cargo.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/fcmaterials", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "FCMaterials.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/market", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Market.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/modulesinfo", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "ModulesInfo.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/navroute", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "NavRoute.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/outfitting", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Outfitting.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/shiplocker", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "ShipLocker.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/shipyard", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Shipyard.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			r.GET("/status", func(c *gin.Context) {
				b, err := os.ReadFile(ExpandPath(filepath.Join(cmd.String("path"), "Status.json")))
				if err != nil {
					c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
				}

				c.Data(200, "application/json; charset=utf-8", b)
			})

			/* Shared variables for the watcher and websocket. */
			hub := HubNew()

			/* Read in all existing Journal files so we know what to ignore. */
			files, err := filepath.Glob(ExpandPath(filepath.Join(cmd.String("path"), "Journal.*.log")))
			if err != nil {
				return err
			}

			for _, f := range files {
				data, err := os.ReadFile(f)
				if err != nil {
					return err
				}

				lines := strings.Split(string(data), "\n")
				previousLine[filepath.Base(f)] = len(lines)
			}

			/* This is the watcher that waits for changes to the journal files. */
			watcher, err := fsnotify.NewWatcher()
			if err != nil {
				return err
			}
			defer watcher.Close()

			go func() {
				for {
					select {
					case event, ok := <-watcher.Events:
						if !ok {
							return
						}

						if event.Op.Has(fsnotify.Write) {
							data, err := processChangedFile(event.Name)
							if err != nil {
								log.Println(err)
								continue
							}
							hub.sendClient(data)
						}
					}
				}
			}()

			err = watcher.Add(ExpandPath(cmd.String("path")))
			if err != nil {
				return err
			}

			/* This is the endpoint for the websocket that publishes events. */
			r.GET("/journal", func(c *gin.Context) {
				w, r := c.Writer, c.Request
				con, err := upgrader.Upgrade(w, r, nil)
				if err != nil {
					log.Print(err)
					return
				}
				client := &Client{hub: hub, conn: con}
				client.hub.registerClient(client)

				go client.keepAlive()
			})

			return r.Run(":3000")
		},
	}

	if err := cmd.Run(context.Background(), os.Args); err != nil {
		log.Fatal(err)
	}
}

func ExpandPath(path string) string {
	re := regexp.MustCompile(`(?m)%([^%]+)%`)
	return os.ExpandEnv(re.ReplaceAllString(path, "${$1}"))
}

func processChangedFile(path string) ([]byte, error) {
	switch filepath.Base(path) {
	case "Backpack.json",
		"Cargo.json",
		"FCMaterials.json",
		"Market.json",
		"ModulesInfo.json",
		"NavRoute.json",
		"Outfitting.json",
		"ShipLocker.json",
		"Shipyard.json",
		"Status.json":
		return os.ReadFile(path)
	default:
		if strings.HasPrefix(filepath.Base(path), "Journal") {
			data, err := os.ReadFile(path)
			if err != nil {
				return nil, err
			}

			offset, ok := previousLine[filepath.Base(path)]
			if !ok {
				offset = 0
			}

			lines := strings.Split(string(data), "\n")
			nextLine := lines[offset-1]
			previousLine[filepath.Base(path)]++

			return []byte(nextLine), nil
		}
	}
	return nil, nil
}