package main

import (
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"regexp"
	"strings"
	"time"

	"github.com/PuerkitoBio/goquery"
)

type (
	// Meal contains the info about a meals
	Meal struct {
		Category string `json:"category"`
		Price    string `json:"price"`
		Title    string `json:"title"`
		Diet     string `json:"diet"`
	}
	// Menu contains all info to menues in a mensa on one day
	Menu struct {
		Day   int    `json:"day"`
		Mensa string `json:"mensa"`
		Meals []Meal `json:"meals"`
		Date  string `json:"date"`
	}
)

var (
	mensen = map[string]string{
		"Zentralmensa":  "zentralmensa",
		"Nordmensa":     "nordmensa",
		"Mensa+am+Turm": "turmmensa",
		"Mensa+Italia":  "mensaitalia",
		"Bistro+HAWK":   "bistrohawk",
	}
	trimRegex = regexp.MustCompile(`\s{2,}`)
)

func main() {
	path := "./"
	if len(os.Args) == 2 {
		path = os.Args[1] + "/"
	}

	for mensa := range mensen {
		for day := 1; day < 8; day = day + 1 {
			menu, err := operate(mensa, day)
			if err != nil {
				fmt.Println(err.Error())
				return
			}

			content, err := json.Marshal(menu)
			if err != nil {
				fmt.Println(err.Error())
				return
			}

			err = ioutil.WriteFile(fmt.Sprintf("%s/%s.%v.json", path, mensen[mensa], day), content, 0644)
			if err != nil {
				fmt.Println(err.Error())
				return
			}
		}
	}
}

func writeToFile(content []byte) error {
	err := ioutil.WriteFile(os.Args[1], content, 0644)
	if err != nil {
		return err
	}
	return nil
}

func operate(mensa string, day int) (Menu, error) {
	currentDay := int(time.Now().Weekday()) // week starts on sunday in go, but thats not relevant, because the canteen is closed on sunday
	push := 0
	if currentDay > day {
		push = 1
	}

	http.DefaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{InsecureSkipVerify: true}
	res, err := http.Get(fmt.Sprintf("http://www.studentenwerk-goettingen.de/speiseplan.html?no_cache=1&day=%v&push=%v&selectmensa=%s", day, push, mensa))
	if err != nil {
		fmt.Println(err)
	}

	document, err := goquery.NewDocumentFromResponse(res)

	if err != nil {
		return Menu{}, err
	}

	meals, err := parseMeals(document)
	if err != nil {
		return Menu{}, err
	}

	date := parseDate(document)
	return Menu{Day: day, Mensa: mensa, Meals: meals, Date: date}, nil
}

func parseDate(doc *goquery.Document) string {
	return strip(doc.Find("#speise-head2_datum").Text())
}

func strip(old string) string {
	return strings.TrimSpace(trimRegex.ReplaceAllString(old, " "))
}

func parseMeals(doc *goquery.Document) ([]Meal, error) {
	meals := []Meal{}
	doc.Find("table.speise-tblmain tbody tr").Each(func(i int, s *goquery.Selection) {
		diet, _ := s.Find(".ext_sits_speiseplan_icon").Children().Attr("alt")
		meal := Meal{
			Category: strip(s.Find(".ext_sits_preis").Text()), // yes, really preis
			Title:    strip(s.Find(".ext_sits_essen").Text()),
			Diet:     strip(diet),
		}
		meals = append(meals, meal)
	})
	return meals, nil
}