package main

import "encoding/json"
import "fmt"
import "io/ioutil"
import "net/http"
import "time"
import "sync"

import "github.com/rs/zerolog/log"

const INDEX_API_TIMEOUT = time.Second * 60

// check with indices only hourly
var INDEX_CHECK_INTERVAL = time.Second * 60 * 60

// check with indices after 10 mins if they failed
var INDEX_ERROR_INTERVAL = time.Second * 60 * 10

var LOG_REPORT_INTERVAL = time.Second * 60

const mastodonIndexUrl = "https://instances.social/list.json?q%5Busers%5D=&q%5Bsearch%5D=&strict=false"
const pleromaIndexUrl = "https://distsn.org/cgi-bin/distsn-pleroma-instances-api.cgi"

type InstanceLocator struct {
	pleromaIndexNextRefresh  *time.Time
	mastodonIndexNextRefresh *time.Time
	reportInstanceVia        chan InstanceHostname
	instances                map[string]*Instance
	sync.Mutex
}

func NewInstanceLocator() *InstanceLocator {
	i := new(InstanceLocator)
	i.instances = make(map[string]*Instance)
	n := time.Now()
	i.pleromaIndexNextRefresh = &n
	i.mastodonIndexNextRefresh = &n
	return i
}

func (self *InstanceLocator) AddInstanceNotificationChannel(via chan InstanceHostname) {
	self.Lock()
	defer self.Unlock()
	self.reportInstanceVia = via
}

func (self *InstanceLocator) addInstance(hostname string) {
	self.Lock()
	defer self.Unlock()
	// only add it if we haven't seen the hostname before
	if self.instances[hostname] == nil {
		log.Info().Str("hostname", hostname).Msgf("adding discovered instance")
		self.instances[hostname] = NewInstance(hostname)
	}

}

func (self *InstanceLocator) Locate() {
	x := time.Now()
	for {
		if self.pleromaIndexNextRefresh.Before(time.Now()) {
			self.locatePleroma()
		}
		if self.mastodonIndexNextRefresh.Before(time.Now()) {
			self.locateMastodon()
		}
		time.Sleep(1 * time.Second)
		if time.Now().After(x.Add(LOG_REPORT_INTERVAL)) {
			x = time.Now()
			log.Debug().
				Str("nextMastodonIndexFetch", self.mastodonIndexNextRefresh.Format(time.RFC3339)).
				Send()
			log.Debug().
				Str("nextPleromaIndexFetch", self.pleromaIndexNextRefresh.Format(time.RFC3339)).
				Send()
			self.logInstanceReport()
		}
	}

}

func (self *InstanceLocator) logInstanceReport() {
	r := self.instanceReport()
	log.Info().
		Uint("up", r.up).
		Uint("total", r.total).
		Uint("identified", r.identified).
		Msg("instance report")
}

type InstanceLocatorReport struct {
	up         uint
	identified uint
	total      uint
}

func (r *InstanceLocatorReport) String() string {
	return fmt.Sprintf("up=%d identified=%d total=%d", r.up, r.identified, r.total)
}

func (self *InstanceLocator) NumInstances() uint {
	return self.instanceReport().total
}

func (self *InstanceLocator) instanceReport() *InstanceLocatorReport {
	self.Lock()
	defer self.Unlock()
	r := new(InstanceLocatorReport)

	r.total = uint(len(self.instances))

	for _, elem := range self.instances {
		if elem.identified == true {
			r.identified = r.identified + 1
		}

		if elem.status == InstanceStatusAlive {
			r.up = r.up + 1
		}
	}

	return r
}

func (self *InstanceLocator) locateMastodon() {
	var c = &http.Client{
		Timeout: INDEX_API_TIMEOUT,
	}

	resp, err := c.Get(mastodonIndexUrl)
	if err != nil {
		log.Error().Msgf("unable to fetch mastodon instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.mastodonIndexNextRefresh = &t
		self.Unlock()
		return
	}

	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)

	if err != nil {
		log.Error().Msgf("unable to fetch mastodon instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.mastodonIndexNextRefresh = &t
		self.Unlock()
		return
	}

	mi := new(MastodonIndexResponse)
	err = json.Unmarshal(body, &mi)
	if err != nil {
		log.Error().Msgf("unable to parse mastodon instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.mastodonIndexNextRefresh = &t
		self.Unlock()
		return
	}

	for _, instance := range mi.Instances {
		self.addInstance(instance.Name)
	}

	t := time.Now().Add(INDEX_CHECK_INTERVAL)
	self.Lock()
	self.mastodonIndexNextRefresh = &t
	self.Unlock()
}

func (self *InstanceLocator) locatePleroma() {
	var c = &http.Client{
		Timeout: INDEX_API_TIMEOUT,
	}
	resp, err := c.Get(pleromaIndexUrl)

	if err != nil {
		log.Error().Msgf("unable to fetch pleroma instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.pleromaIndexNextRefresh = &t
		self.Unlock()
		return
	}

	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)

	if err != nil {
		log.Error().Msgf("unable to fetch pleroma instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.pleromaIndexNextRefresh = &t
		self.Unlock()
		return
	}

	// fetch worked
	pi := new(PleromaIndexResponse)
	err = json.Unmarshal(body, &pi)
	if err != nil {
		log.Warn().Msgf("unable to parse pleroma instance list: %s", err)
		t := time.Now().Add(INDEX_ERROR_INTERVAL)
		self.Lock()
		self.pleromaIndexNextRefresh = &t
		self.Unlock()
		return
	}

	for _, instance := range *pi {
		self.addInstance(instance.Domain)
	}
	t := time.Now().Add(INDEX_CHECK_INTERVAL)
	self.Lock()
	self.pleromaIndexNextRefresh = &t
	self.Unlock()
}