// TODO: docstring

package main

import (
	"encoding/csv"
	"fmt"
	"log"
	"os"
	"strconv"
	"text/template"
	"time"
)

var timeCSVFormat = "2.1.06 15:04"   // input format
var timeXMLDateFormat = "2006-01-02" // frab xml format for dates
var timeXMLTimeFormat = "15:04"      // frab xml format for times

const csvColTitle = 0
const csvColRoom = 1
const csvColStart = 2
const csvColEnd = 3
const csvColSpeaker = 4
const csvColLang = 5

type frabSchedule struct {
	Conf conference
	Days []day
}

type conference struct {
	Title string
	Start string // date (yyyy-mm-dd)
	End   string // date (yyyy-mm-dd)
	Days  int
}

type day struct {
	Index int
	Date  string // date (yyyy-mm-dd)
	Start string // timedate (RFC3339)
	End   string // timedate (RFC3339)
	Rooms []room
}

type room struct {
	Name   string
	Events []event
}

type event struct {
	ID   int
	GUID string // autogen UUID

	Room     string
	Title    string
	Date     string // timedate (RFC3339)
	Start    string // time (hh:mm)
	Duration string // time (hh:mm)
	Language string

	Persons []person
}

type person struct {
	ID   int
	Name string
}

func fmtDuration(d time.Duration) string {
	d = d.Round(time.Minute)
	h := d / time.Hour
	d -= h * time.Hour
	m := d / time.Minute
	return fmt.Sprintf("%02d:%02d", h, m)
}

func main() {
	fmt.Println("Conference Schedule: CSV to Frab (Infobeamer) Converter")

	/*
	 * Data Input
	 */
	// read CSV contents
	csvFile, err := os.Open("schedule.csv")
	if err != nil {
		log.Fatal("Error opening CSV file:\n", err)
	}

	csvReader := csv.NewReader(csvFile)
	csvReader.Comma = ';' // MS excel default export format
	records, err := csvReader.ReadAll()
	if err != nil {
		log.Fatal("Error reading CSV file:\n", err)
	}

	// omit title row
	csvRecords := records[1:]

	/*
	 * Data Conversion
	 */
	roomsList := make(map[time.Time]map[string]int) // map of day's start time to map of room names
	var conferenceStart time.Time
	var conferenceEnd time.Time
	loc, _ := time.LoadLocation("Europe/Berlin")

	for idx, row := range csvRecords {
		// parse event times
		eventStart, err := time.ParseInLocation(timeCSVFormat, row[csvColStart], loc)
		if err != nil {
			log.Fatal("Error parsing start date in CSV file, line ", idx+1, ":\n", err)
		}
		eventEnd, err := time.ParseInLocation(timeCSVFormat, row[csvColEnd], loc)
		if err != nil {
			log.Fatal("Error parsing end date in CSV file, line ", idx+1, ":\n", err)
		}

		// create unique list of the rooms for each day
		dayStart := eventStart.Truncate(24 * time.Hour)
		if roomsList[dayStart] == nil {
			roomsList[dayStart] = make(map[string]int)
		}
		roomsList[dayStart][row[csvColRoom]] = 1

		// get conference start and end date
		if idx == 0 {
			conferenceStart = eventStart
			conferenceEnd = eventEnd
		}
		if eventStart.Before(conferenceStart) {
			conferenceStart = eventStart
		}
		if eventEnd.After(conferenceEnd) {
			conferenceEnd = eventEnd
		}
	}

	conferenceStart = conferenceStart.Truncate(24 * time.Hour)
	conferenceEnd = conferenceEnd.Truncate(24 * time.Hour).Add(24 * time.Hour)

	// convert csv entries into event and sort in days
	events := make(map[int][]event) // map of day index to day's events
	eventID := 100
	speakerID := 1
	confDays := make(map[int]day) // map of day index to day structure

	for idx, row := range csvRecords {
		eventStart, err := time.ParseInLocation(timeCSVFormat, row[csvColStart], loc)
		if err != nil {
			log.Fatal("Error parsing start date in CSV file, line ", idx+1, ":\n", err)
		}
		eventEnd, err := time.ParseInLocation(timeCSVFormat, row[csvColEnd], loc)
		if err != nil {
			log.Fatal("Error parsing end date in CSV file, line ", idx+1, ":\n", err)
		}

		// create event struct and sort into day map
		var eventSpeaker []person
		if row[csvColSpeaker] != "" {
			eventSpeaker = append(eventSpeaker, person{speakerID, row[csvColSpeaker]})
		}

		dayIdx := int(eventStart.Sub(conferenceStart).Hours()/24) + 1
		eventGUID := strconv.Itoa(dayIdx) + "-" + strconv.Itoa(eventID)
		eventDateStr := eventStart.Format(time.RFC3339)
		eventStartStr := eventStart.Format(timeXMLTimeFormat)
		eventDurationStr := fmtDuration(eventEnd.Sub(eventStart))

		events[dayIdx] = append(events[dayIdx], event{eventID, eventGUID, row[csvColRoom], row[csvColTitle], eventDateStr, eventStartStr, eventDurationStr, row[csvColLang], eventSpeaker})

		// create days
		if _, ok := confDays[dayIdx]; !ok {
			dayDateStr := eventStart.Format(timeXMLDateFormat)
			dayStart := eventStart.Truncate(24 * time.Hour)
			dayEnd := dayStart.Add(24 * time.Hour)
			dayStartStr := dayStart.Format(time.RFC3339)
			dayEndStr := dayEnd.Format(time.RFC3339)

			var dayRooms []room
			for roomName := range roomsList[dayStart] {
				dayRooms = append(dayRooms, room{roomName, nil})
			}

			confDays[dayIdx] = day{dayIdx, dayDateStr, dayStartStr, dayEndStr, dayRooms}
		}

		eventID++
	}

	// sort events to rooms and day structures
	for dayIdx, eventDay := range events {
		for _, event := range eventDay {
			for roomIdx, roomName := range confDays[dayIdx].Rooms {
				if roomName.Name == event.Room {
					confDays[dayIdx].Rooms[roomIdx].Events = append(confDays[dayIdx].Rooms[roomIdx].Events, event)
				}
			}
		}
	}

	// new conference
	confDurationDays := int(conferenceEnd.Sub(conferenceStart).Hours() / 24)
	conf := conference{"Wälderhaus Veranstaltung", conferenceStart.Format(time.RFC3339), conferenceEnd.Format(time.RFC3339), confDurationDays}

	var days []day
	for _, d := range confDays {
		days = append(days, d)
	}

	sched := frabSchedule{conf, days}

	/*
	 * Data Export
	 */
	// open output file
	xmlOutput, err := os.Create("schedule.xml")
	defer xmlOutput.Close()
	if err != nil {
		log.Fatal("Error opening XML file for output:\n", err)
	}

	t := template.New("Frab XML Template")
	t, err = t.ParseFiles("tmpl/schedule.xml")
	if err != nil {
		log.Fatal("Error parsing XML template:\n", err)
	}
	err = t.ExecuteTemplate(xmlOutput, "schedule.xml", sched)
	if err != nil {
		log.Println("Error executing XML template:\n", err)
	}

	/*
	 * Print Summary
	 */
	fmt.Println("- Conference Start:", conferenceStart)
	fmt.Println("- Conference End  :", conferenceEnd)
	fmt.Println("- Days            :", confDurationDays)
	fmt.Println("- Events          :", eventID-100)

	// fmt.Println("Dump days:")
	// for _, day := range days {
	// 	fmt.Println("Day", day.Index)
	// 	for _, room := range day.Rooms {
	// 		fmt.Println("  Room", room.Name)
	// 		for _, event := range room.Events {
	// 			fmt.Println("    Event", event)
	// 		}
	// 	}
	// }

	fmt.Println("done")
}