package main

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
	"time"
	"unicode"

	"github.com/hamcha/tg"
)

var remindpath *string

type Reminder struct {
	TargetID  int64
	When      int64
	Text      string
	Reference *ReminderReference
}

type ReminderReference struct {
	Chat    int64
	Message int64
}

var reminders map[string]Reminder

const ReminderMaxDuration = time.Hour * 24 * 30 * 3

func remind_init() {
	reminders = make(map[string]Reminder)
	file, err := os.Open(*remindpath)
	if err != nil {
		return
	}
	defer file.Close()
	err = json.NewDecoder(file).Decode(&reminders)
	if err != nil {
		log.Println("[remind] WARN: Could not load pending reminders (malformed or unreadable file): " + err.Error())
		return
	}
	for id := range reminders {
		go runreminder(id)
	}
	log.Printf("[remind] Loaded %d pending reminders from %s\n", len(reminders), *remindpath)
}

func remind_message(broker *tg.Broker, update tg.APIMessage) {
	if isCommand(update, "ricordami") {
		// Supported formats:
		// Xs/m/h/d   => in X seconds/minutes/hours/days
		// HH:MM      => at HH:MM    (24 hour format)
		// HH:MM:SS   => at HH:MM:SS (24 hour format)
		// dd/mm/yyyy => same hour, specific date
		// dd/mm/yyyy-HH:MM    => specific hour, specific dat
		// dd/mm/yyyy-HH:MM:SS => specific hour, specific date

		parts := strings.SplitN(*(update.Text), " ", 3)

		// Little hack to allow text-less reminders with replies
		if len(parts) == 2 && update.ReplyTo != nil {
			parts = append(parts, "")
		}

		if len(parts) < 3 {
			broker.SendTextMessage(update.Chat, "<b>Sintassi</b>\n/ricordami <i>[quando]</i> Messaggio\n\n<b>Formati supportati per [quando]</b>:\n 10s 10m 10h 10d (secondi/minuti/ore/giorni)\n 13:20 15:55:01 (ora dello stesso giorno, formato 24h)\n 11/02/2099 11/02/2099-11:20:01 (giorno diverso, stessa ora [1] o specifica [2])", &update.MessageID)
			return
		}

		format := parts[1]
		message := parts[2]

		timestamp, err := parseDuration(format)
		if err != nil {
			broker.SendTextMessage(update.Chat, err.Error(), &update.MessageID)
			return
		}

		id := strconv.FormatInt(update.Chat.ChatID, 36) + "-" + strconv.FormatInt(update.MessageID, 36)
		reminder := Reminder{
			TargetID: update.User.UserID,
			When:     timestamp.Unix(),
			Text:     message,
		}
		if update.ReplyTo != nil {
			reminder.Reference = &ReminderReference{
				Chat:    update.Chat.ChatID,
				Message: update.ReplyTo.MessageID,
			}
		}
		reminders[id] = reminder
		savereminder()
		go runreminder(id)

		whenday := "più tardi"
		_, todaym, todayd := time.Now().Date()
		_, targetm, targetd := timestamp.Date()
		if todaym != targetm || todayd != targetd {
			whenday = "il " + timestamp.Format("2/1")
		}
		whentime := "alle " + timestamp.Format("15:04:05")
		broker.SendTextMessage(update.Chat, "Ok, vedrò di avvisarti "+whenday+" "+whentime, &update.MessageID)
	}
}

func runreminder(id string) {
	// In case this is called in the init, wait until the broker is available
	for broker == nil {
		// Wait
		time.Sleep(time.Second)
	}

	// Get reminder
	r := reminders[id]
	remaining := r.When - time.Now().Unix()
	if remaining > 0 {
		// Wait remaining time
		time.Sleep(time.Second * time.Duration(remaining))
	}
	// Remind!
	broker.SendTextMessage(&tg.APIChat{ChatID: r.TargetID}, "<b>Heyla! Mi avevi chiesto di ricordarti questo:</b>\n"+r.Text, nil)
	if r.Reference != nil {
		broker.ForwardMessage(&tg.APIChat{ChatID: r.TargetID}, tg.APIMessage{MessageID: r.Reference.Message, Chat: &tg.APIChat{ChatID: r.Reference.Chat}})
	}
	// Delete reminder from pending list and save list to disk
	delete(reminders, id)
	savereminder()
}

func savereminder() {
	file, err := os.Create(*remindpath)
	if err != nil {
		log.Println("[remind] WARN: Could not open pending reminders file: " + err.Error())
		return
	}
	err = json.NewEncoder(file).Encode(reminders)
	if err != nil {
		log.Println("[macro] WARN: Could not save pending reminders into file: " + err.Error())
	}
}

func isSscanfValid(n int, err error) bool {
	return err == nil
}

func parseDuration(date string) (time.Time, error) {
	now := time.Now()
	num := 0
	sep := ' '
	hour := now.Hour()
	min := now.Minute()
	sec := now.Second()
	day := now.Day()
	month := now.Month()
	year := now.Year()
	switch {
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d-%d:%d:%d", &day, &month, &year, &hour, &min, &sec)):
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d-%d:%d", &day, &month, &year, &hour, &min)):
		sec = 0
	case isSscanfValid(fmt.Sscanf(date, "%d/%d/%d", &day, &month, &year)):
		hour = now.Hour()
		min = now.Minute()
		sec = now.Second()
	case isSscanfValid(fmt.Sscanf(date, "%d:%d:%d", &hour, &min, &sec)):
		day = now.Day()
		month = now.Month()
		year = now.Year()
	case isSscanfValid(fmt.Sscanf(date, "%d:%d", &hour, &min)):
		day = now.Day()
		month = now.Month()
		year = now.Year()
		sec = 0
	case isSscanfValid(fmt.Sscanf(date, "%d%c", &num, &sep)):
		dur := time.Duration(num)
		switch unicode.ToLower(sep) {
		case 's':
			dur *= time.Second
		case 'm':
			dur *= time.Minute
		case 'h':
			dur *= time.Hour
		case 'd':
			dur *= time.Hour * 24
		default:
			return now, fmt.Errorf("La durata ha una unità che non conosco, usa una di queste: s (secondi) m (minuti) h (ore) d (giorni)")
		}
		return now.Add(dur), nil
	default:
		return now, fmt.Errorf("Non capisco quando dovrei ricordartelo!")
	}
	loc, _ := time.LoadLocation("Local")
	targetDate := time.Date(year, month, day, hour, min, sec, 0, loc)
	if targetDate.Before(now) {
		return now, fmt.Errorf("Non posso ricordarti cose nel passato!")
	}
	if targetDate.After(now.Add(ReminderMaxDuration)) {
		return now, fmt.Errorf("Non credo riuscirei a ricordarmi qualcosa per così tanto")
	}
	return targetDate, nil
}