Make a working tool.

Next step: capture a load of JSON files for the mock server.

go.mod

@@ -0,0 +1,3 @@
+module gitea.ligthert.net/golang/dcsw_server_map/mock_listener
+
+go 1.21.6

main.go

@@ -0,0 +1,91 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"time"
+)
+
+type Core struct {
+	cache     string
+	logger    *log.Logger
+	http_port string
+	folder    string
+	delay     int
+}
+
+func main() {
+
+	var core Core
+	core.logger = log.New(os.Stdout, "[MOCK] ", log.Ldate|log.Ltime)
+
+	var flagHTTP = flag.String("http", ":8888", "Listen [addres]:port for the HTTP listener.")
+	var flagFolder = flag.String("folder", "slides", "Folder to iterate through a series of .json files.")
+	var flagDelay = flag.Int("delay", 5, "Delay in seconds before moving to the next file in a series.")
+	flag.Parse()
+	core.http_port = *flagHTTP
+	core.folder = *flagFolder
+	core.delay = *flagDelay
+
+	// Kickstart the logic
+	core.logger.Println("Starting Logic Controller (LC) in the background.")
+	go core.logicController()
+
+	// Start the HTTP server
+	core.logger.Println("Starting HTTP listener on", core.http_port)
+	http.HandleFunc("/", core.serveSlides)
+	err := http.ListenAndServe(core.http_port, nil)
+	if errors.Is(err, http.ErrServerClosed) {
+		core.logger.Println("server closed.")
+	} else if err != nil {
+		core.logger.Printf("error starting server: %s\n", err)
+		os.Exit(1)
+	}
+
+}
+
+func (core *Core) logicController() {
+
+	// Find all the json files and chuck 'em in a slice
+	var files []string
+
+	entries, err := os.ReadDir(core.folder)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, e := range entries {
+		if string(e.Name())[len(e.Name())-5:] == ".json" {
+			files = append(files, e.Name())
+		}
+	}
+
+	core.logger.Println("(LC) processing the following files", files)
+
+	/// Periodically change contents
+	for {
+		for _, file := range files {
+			contents, err := os.ReadFile(core.folder + "/" + file)
+			core.check(err)
+			core.cache = string(contents)
+			time.Sleep(time.Duration(core.delay) * time.Second)
+		}
+	}
+
+}
+
+func (core *Core) serveSlides(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	io.WriteString(w, string(core.cache)+"\n") // Have \n at the end or not?
+}
+
+func (core *Core) check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}