package ntfy

import (
	"bufio"
	"encoding/json"
	"log"
	"net/http"
	"net/url"
	"path"
	"time"
)

type Message struct {
	Id      string `json:"id"`
	Time    int    `json:"time"`
	Message string `json:"message"`
	Event   string `json:"event"`
}

type NtfyWatcher struct {
	Endpoint string
	Topics   []string
}

func (w *NtfyWatcher) Watch() chan Message {
	notifications := make(chan Message)

	for _, topic := range w.Topics {
		log.Println("subscribing to topic:", topic)

		go func() {
			retryCount := 5
			retryTime := 5 * time.Second
			retries := retryCount

			sleepAndDecrementRetry := func() {
				log.Println("waiting 5 seconds before reconnecting. retries left:", retries, "topic:", topic, "endpoint:", w.Endpoint)
				time.Sleep(retryTime)
				retries--
			}

			for true {
				if retries == 0 {
					log.Fatal("too many retries, exiting")
				}

				endpoint, _ := url.JoinPath(w.Endpoint, path.Join(topic, "json"))
				resp, err := http.Get(endpoint)
				if err != nil {
					log.Println("error connecting to endpoint:", err)
					sleepAndDecrementRetry()
					continue
				}

				defer resp.Body.Close()
				scanner := bufio.NewScanner(resp.Body)
				for scanner.Scan() {
					bytes := scanner.Bytes()
					var msg Message
					err := json.Unmarshal(bytes, &msg)
					if err != nil {
						log.Println("could not unmarshal message:", err)
						continue
					}

					if msg.Event == "keepalive" {
						log.Println("received keepalive message")
						continue
					}
					if msg.Event != "message" {
						log.Println("received unknown event:", msg.Event)
						continue
					}

					log.Println("received notification:", msg)
					notifications <- msg
					retries = retryCount // reset retries
				}

				if err := scanner.Err(); err != nil {
					log.Println("error reading response body:", err)
					sleepAndDecrementRetry()
				}
			}
		}()
	}

	return notifications
}

func MakeNtfyWatcher(endpoint string, topics []string) *NtfyWatcher {
	return &NtfyWatcher{
		Endpoint: endpoint,
		Topics:   topics,
	}
}