package core

import (
	"strings"
	"sync"
	"time"

	"git.wntrmute.dev/kyle/goutils/backoff"
	"git.wntrmute.dev/kyle/goutils/log"
	"github.com/gregdel/pushover"
)

// MessageBuffer is how many messages to back up. This represents a
// balance between expected usage and anticipated spikes. It is
// entirely empirical as I don't have data to drive this decision.
const MessageBuffer = 16

type Account struct {
	p            *pushover.Pushover
	nextTransmit time.Time
	q            chan *Message
	lock         *sync.Mutex
	bo           *backoff.Backoff
}

func (a *Account) Queue() chan<- *Message {
	return a.q
}

func NewAccount(token string) *Account {
	return &Account{
		p:    pushover.New(token),
		q:    make(chan *Message, MessageBuffer),
		lock: &sync.Mutex{},
		bo:   backoff.New(4*time.Hour, 5*time.Second),
	}
}

func (a *Account) UpdateLimit(limit *pushover.Limit) {
	a.lock.Lock()
	if limit.Remaining > 0 {
		return
	}

	a.nextTransmit = limit.NextReset.Add(time.Second)
}

func (a *Account) Receive() {
	for {
		m, closed := <-a.q
		if !closed {
			panic("channel closed")
		}

		a.Push(m)
	}
}

func (a *Account) push(m *pushover.Message, r *pushover.Recipient) (*pushover.Response, error) {
	for time.Now().Before(a.nextTransmit) {
		log.Infof("delaying until next transmit: %s", a.nextTransmit.Format(time.DateTime))
		wait := time.Until(a.nextTransmit)
		time.Sleep(wait)
	}

	resp, err := a.p.SendMessage(m, r)
	if err != nil {
		return resp, err
	}

	if resp.Limit != nil {
		log.Debugf("API limits: %d / %d remaining", resp.Limit.Remaining, resp.Limit.Total)
		log.Debugf("API next reset: %s", resp.Limit.NextReset.Format(time.DateTime))
		a.UpdateLimit(resp.Limit)
	}

	return resp, nil
}

func (a *Account) Push(m *Message) {
	for i, r := range m.r {
		recipient := pushover.NewRecipient(r)
		resp, err := a.push(m.m, recipient)
		if err != nil {
			// if there's an error, log it, clean up the recipient list.
			log.Errf("core: failed to send message: %s", err)

			if resp.Status/100 == 4 {
				log.Errf("core: the Pushover API reported the following errors: %s", strings.Join(resp.Errors, ", "))
				log.Infoln("core: 4XX error from Pushover API; not retrying - dropping the message")
				return
			}
			log.Infoln("core: requeueing message that failed to send")
			log.Infoln("core: backing off")
			m.r = m.r[i:]
			a.q <- m
			time.Sleep(a.bo.Duration())
			return
		}

		a.bo.Reset()
	}

	return
}