package main

import (
    "database/sql"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
    "os"
    "time"

    "gopkg.in/telegram-bot-api.v4"

    _ "github.com/lib/pq"
)

var (
    config Config
    db     *sql.DB
)

type Config struct {
    // Database settings
    Host     string `json:"host"`
    Port     string `json:"port"`
    Username string `json:"username"`
    Password string `json:"password"`
    Database string `json:"database"`

    // Telegram settings
    TgToken  string `json:"tgtoken"`
    TgDomain string `json:"tgdomain"`
    TgPort   string `json:"tgport"`
}

func main() {
    log.Println("Starting application...")

    // Load configuration settings.
    data, err := ioutil.ReadFile("/etc/bot/config.json")

    switch {
    case os.IsNotExist(err):
        log.Println("Config file missing, using defaults")
        config = Config{
            // Database settings
            Host:     "localhost",
            Port:     "5432",
            Database: "postgres",
            Username: "postgres",
            Password: "postgres",

            // Telegram settings
            TgToken:  "",
            TgDomain: "",
            TgPort:   "443",
        }
    case err == nil:
        if err := json.Unmarshal(data, &config); err != nil {
            log.Fatal(err)
        }
    default:
        log.Println(err)
    }

    log.Println("Overriding configuration from environment variables")
    // Database settings
    if os.Getenv("APP_HOST") != "" {
        config.Host = os.Getenv("APP_HOST")
    }
    if os.Getenv("APP_PORT") != "" {
        config.Port = os.Getenv("APP_PORT")
    }
    if os.Getenv("APP_USERNAME") != "" {
        config.Username = os.Getenv("APP_USERNAME")
    }
    if os.Getenv("APP_PASSWORD") != "" {
        config.Password = os.Getenv("APP_PASSWORD")
    }
    if os.Getenv("APP_DATABASE") != "" {
        config.Database = os.Getenv("APP_DATABASE")
    }
    // Telegram settings
    if os.Getenv("TELEGRAM_TOKEN") != "" {
        config.TgToken = os.Getenv("TELEGRAM_TOKEN")
    }
    if os.Getenv("TELEGRAM_DOMAIN") != "" {
        config.TgDomain = os.Getenv("TELEGRAM_DOMAIN")
    }
    if os.Getenv("TELEGRAM_PORT") != "" {
        config.TgPort = os.Getenv("TELEGRAM_PORT")
    }

    // Connect to database
    log.Println(fmt.Sprintf("Connecting to database at %s:%s", config.Host, config.Port))

    psqlInfo := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=disable",
        config.Host, config.Port, config.Username, config.Password, config.Database)

    db, err = sql.Open("postgres", psqlInfo)
    if err != nil {
        log.Println(err)
    }

    var dbError error
    maxAttempts := 20
    for attempts := 1; attempts <= maxAttempts; attempts++ {
        dbError = db.Ping()
        if dbError == nil {
            break
        }
        log.Println(dbError)
        time.Sleep(time.Duration(attempts) * time.Second)
    }
    if dbError != nil {
        log.Fatal(dbError)
    }

    log.Println("Application started successfully.")

    // Main Telegram Bot
    bot, err := tgbotapi.NewBotAPI(config.TgToken)
    if err != nil {
        log.Fatal(err)
    }

    bot.Debug = false

    log.Printf("Authorized on account %s", bot.Self.UserName)

    _, err = bot.SetWebhook(tgbotapi.NewWebhook("https://" + config.TgDomain + ":" + config.TgPort + "/" + config.TgToken))
    if err != nil {
        log.Fatal(err)
    }

    updates := bot.ListenForWebhook("/" + bot.Token)
    go http.ListenAndServe("0.0.0.0:"+config.TgPort, nil)

    for update := range updates {
        if update.Message == nil {
            continue
        }

        log.Printf("[%s] %s", update.Message.From.UserName, update.Message.Text)

        msg := tgbotapi.NewMessage(update.Message.Chat.ID, update.Message.Text)
        msg.ReplyToMessageID = update.Message.MessageID

        bot.Send(msg)
    }
}