// main.go
// (Run: go build && ./yourapp)
// This server serves the static files for the client from "./public"
// and provides endpoints to load/save a single .excalidraw file.
//
// Make sure to create a "public" folder and build the SolidJS client into it.
package main

import (
	"encoding/json"
	"io"
	"log"
	"net/http"
	"os"
)

const stateFile = "drawing.excalidraw"

func main() {
	http.Handle("/", http.FileServer(http.Dir("public")))

	http.HandleFunc("/api/state", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type")

		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusOK)
			return
		}

		if r.Method == http.MethodGet {
			w.Header().Set("Content-Type", "application/json")
			data, err := os.ReadFile(stateFile)
			if err != nil {
				log.Println("No file yet or error reading file:", err)
				// If no file yet, return empty object
				w.Write([]byte(`{}`))
				return
			}
			w.Write(data)
			return
		} else if r.Method == http.MethodPost {
			log.Println("POST /api/state")
			body, err := io.ReadAll(r.Body)
			if err != nil {
				http.Error(w, "cannot read body", http.StatusBadRequest)
				return
			}
			// Validate JSON
			var js interface{}
			if err := json.Unmarshal(body, &js); err != nil {
				http.Error(w, "invalid json", http.StatusBadRequest)
				return
			}
			if err := os.WriteFile(stateFile, body, 0644); err != nil {
				http.Error(w, "cannot save file", http.StatusInternalServerError)
				return
			}
			w.WriteHeader(http.StatusOK)
			return
		}
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	})

	log.Println("Server running on http://localhost:8080")
	http.ListenAndServe(":8080", nil)
}