package main

import (
	"embed"
	_ "embed"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"strconv"
	"strings"
	"time"
	"velvettear/go-scan/config"
	"velvettear/go-scan/log"
	"velvettear/go-scan/util/date"
)

//go:embed resources
var resources embed.FS

var configuration config.Config

func main() {
	configuration = config.New()
	startServer()
}

func startServer() {
	serverAddress := configuration.ServerConfig.Address + ":" + configuration.ServerConfig.Port
	http.HandleFunc("/favicon.ico", serveResources)
	http.HandleFunc("/resources/", serveResources)
	http.HandleFunc("/", handleHTTPRequests)
	log.Info("starting server '" + serverAddress + "'...")
	error := http.ListenAndServe(serverAddress, nil)
	if error != nil {
		log.Fatal("an error occured starting the server", error.Error())
	}
}

func serveResources(writer http.ResponseWriter, request *http.Request) {
	var resource string
	if strings.HasSuffix(request.URL.Path, "favicon.ico") {
		resource = "resources/gopher.png"
	} else {
		resource = strings.TrimPrefix(request.URL.Path, "/")
	}
	bytes, error := resources.ReadFile(resource)
	if error != nil {
		log.Error("an error occured serving the resource '"+resource+"'", error.Error())
		return
	}
	log.Debug("serving '" + resource + "'...")
	if strings.HasSuffix(resource, "svg") {
		writer.Header().Set("Content-Type", "image/svg+xml")
	}
	writer.Write(bytes)
}

func handleHTTPRequests(writer http.ResponseWriter, request *http.Request) {
	if strings.ToLower(request.Method) == "post" {
		result := handleScan(request)
		writer.Header().Set("Content-Type", "application/json")
		json, _ := json.Marshal(result)
		writer.Write(json)
		return
	}
	resource := "resources/index.html"
	bytes, error := resources.ReadFile(resource)
	if error != nil {
		log.Error("an error occured serving the resource '"+resource+"'", error.Error())
		return
	}
	log.Debug("serving '" + resource + "'...")
	writer.Write(bytes)
}

func handleScan(request *http.Request) *result {
	log.Info("starting scan...")
	timestamp := date.Milliseconds()

	var parameters requestParameters
	parseErr := json.NewDecoder(request.Body).Decode(&parameters)
	if parseErr != nil {
		log.Error("error parsing request parameters", parseErr.Error())
	}
	scanName := generateScanName(parameters.Filename)
	args := []string{}
	if len(configuration.ScannerConfig.Scanner) > 0 {
		args = append(args, "-d")
		args = append(args, configuration.ScannerConfig.Scanner)
	}
	args = append(args, "-o")
	args = append(args, scanName)
	extraArgs := strings.Split(configuration.ScannerConfig.Arguments, " ")
	for index := 0; index < len(extraArgs); index++ {
		args = append(args, extraArgs[index])
	}
	log.Debug("executing command 'scanimage'...", args...)
	scanCmd := exec.Command(
		"scanimage",
		args...,
	)
	_, err := scanCmd.Output()
	if err != nil {
		log.Error("an error occured executing the scan", err.Error())
		result := &result{
			State:   "error",
			Message: err.Error(),
		}
		return result
	}
	result := &result{
		State:   "ok",
		Message: scanName,
	}
	log.Info("finished scan after "+strconv.Itoa(date.GetTimeDifference(timestamp))+"ms", scanName)
	return result
}

func generateScanName(filename string) string {
	if len(filename) == 0 {
		day := fmt.Sprint(time.Now().Day())
		if len(day) < 2 {
			day = "0" + day
		}
		month := fmt.Sprint(int(time.Now().Month()))
		if len(month) < 2 {
			month = "0" + month
		}
		hour := fmt.Sprint(time.Now().Hour())
		if len(hour) < 2 {
			hour = "0" + hour
		}
		minute := fmt.Sprint(time.Now().Minute())
		if len(minute) < 2 {
			minute = "0" + minute
		}
		second := fmt.Sprint(time.Now().Second())
		if len(second) < 2 {
			second = "0" + second
		}
		filename = day + month + fmt.Sprint(time.Now().Year()) + "-" + hour + minute + second
	}
	if !strings.HasSuffix(filename, ".png") {
		filename += ".png"
	}
	error := os.MkdirAll(configuration.ScannerConfig.OutputDirectory, 0755)
	if error != nil {
		log.Fatal("an error occurred creating the output directory", error.Error())
	}
	return configuration.ScannerConfig.OutputDirectory + filename
}

// structs
type result struct {
	State   string
	Message string
}

type requestParameters struct {
	Filename string
}