package instance

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

//import "github.com/gin-gonic/gin"
import "github.com/looplab/fsm"
import "github.com/rs/zerolog/log"
import "git.eeqj.de/sneak/feta/storage"
import "git.eeqj.de/sneak/feta/toot"
import "git.eeqj.de/sneak/feta/jsonapis"

const nodeInfoSchemaVersionTwoName = "http://nodeinfo.diaspora.software/ns/schema/2.0"
const instanceNodeinfoTimeout = time.Second * 50
const instanceHTTPTimeout = time.Second * 120
const instanceSpiderInterval = time.Second * 120
const instanceErrorInterval = time.Second * 60 * 30

type instanceImplementation int

// Hostname is a special type for holding the hostname of an
// instance (string)
type Hostname string

const (
	implUnknown instanceImplementation = iota
	implMastodon
	implPleroma
)

// Instance stores all the information we know about an instance
type Instance struct {
	structLock                 sync.Mutex
	tootDestination            chan *toot.Toot
	ErrorCount                 uint
	SuccessCount               uint
	highestID                  int
	Hostname                   string
	Identified                 bool
	fetching                   bool
	implementation             instanceImplementation
	storageBackend             *storage.TootStorageBackend
	NextFetch                  time.Time
	nodeInfoURL                string
	ServerVersionString        string
	ServerImplementationString string
	fetchingLock               sync.Mutex
	fsm                        *fsm.FSM
	fsmLock                    sync.Mutex
}

// New returns a new instance, argument is a function that operates on the
// new instance
func New(options ...func(i *Instance)) *Instance {
	i := new(Instance)
	i.setNextFetchAfter(1 * time.Second)

	i.fsm = fsm.NewFSM(
		"STATUS_UNKNOWN",
		fsm.Events{
			{Name: "BEGIN_NODEINFO_URL_FETCH", Src: []string{"STATUS_UNKNOWN"}, Dst: "FETCHING_NODEINFO_URL"},
			{Name: "GOT_NODEINFO_URL", Src: []string{"FETCHING_NODEINFO_URL"}, Dst: "PRE_NODEINFO_FETCH"},
			{Name: "BEGIN_NODEINFO_FETCH", Src: []string{"PRE_NODEINFO_FETCH"}, Dst: "FETCHING_NODEINFO"},
			{Name: "GOT_NODEINFO", Src: []string{"FETCHING_NODEINFO"}, Dst: "READY_FOR_TOOTFETCH"},
			{Name: "FETCH_TIME_REACHED", Src: []string{"READY_FOR_TOOTFETCH"}, Dst: "READY_AND_DUE_FETCH"},
			{Name: "BEGIN_TOOT_FETCH", Src: []string{"READY_AND_DUE_FETCH"}, Dst: "FETCHING"},
			{Name: "WEIRD_NODE_RESPONSE", Src: []string{"FETCHING_NODEINFO_URL", "PRE_NODEINFO_FETCH", "FETCHING_NODEINFO"}, Dst: "WEIRD_NODE"},
			{Name: "EARLY_FETCH_ERROR", Src: []string{"FETCHING_NODEINFO_URL", "PRE_NODEINFO_FETCH", "FETCHING_NODEINFO"}, Dst: "EARLY_ERROR"},
			{Name: "TOOT_FETCH_ERROR", Src: []string{"FETCHING"}, Dst: "TOOT_FETCH_ERROR"},
			{Name: "TOOTS_FETCHED", Src: []string{"FETCHING"}, Dst: "READY_FOR_TOOTFETCH"},
		},
		fsm.Callbacks{
			"enter_state": func(e *fsm.Event) { i.fsmEnterState(e) },
		},
	)

	for _, opt := range options {
		opt(i)
	}
	return i
}

// Status returns the instance's state in the FSM
func (i *Instance) Status() string {
	i.fsmLock.Lock()
	defer i.fsmLock.Unlock()
	return i.fsm.Current()
}

// SetTootDestination takes a channel from the manager that all toots
// fetched from this instance should be pushed into. The instance is not
// responsible for deduplication, it should shove all toots on every fetch
// into the channel.
func (i *Instance) SetTootDestination(d chan *toot.Toot) {
	i.tootDestination = d
}

// Event is the method that alters the FSM
func (i *Instance) Event(eventname string) {
	i.fsmLock.Lock()
	defer i.fsmLock.Unlock()
	i.fsm.Event(eventname)
}

func (i *Instance) fsmEnterState(e *fsm.Event) {
	log.Debug().
		Str("hostname", i.Hostname).
		Str("state", e.Dst).
		Msg("instance changed state")
}

// Lock locks the instance's mutex for reading/writing from the structure
func (i *Instance) Lock() {
	i.structLock.Lock()
}

// Unlock unlocks the instance's mutex for reading/writing from the structure
func (i *Instance) Unlock() {
	i.structLock.Unlock()
}

func (i *Instance) bumpFetch() {
	i.Lock()
	defer i.Unlock()
	i.NextFetch = time.Now().Add(120 * time.Second)
}

func (i *Instance) setNextFetchAfter(d time.Duration) {
	i.Lock()
	defer i.Unlock()
	i.NextFetch = time.Now().Add(d)
}

// Fetch prepares an instance for fetching.  Bad name, fix it.
// FIXME(sneak)
func (i *Instance) Fetch() {
	i.fetchingLock.Lock()
	defer i.fetchingLock.Unlock()

	i.setNextFetchAfter(instanceErrorInterval)

	err := i.DetectNodeTypeIfNecessary()
	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msg("unable to fetch instance metadata")
		return
	}

	i.setNextFetchAfter(instanceSpiderInterval)
	log.Info().
		Str("hostname", i.Hostname).
		Msg("instance now ready for fetch")
}

// FIXME rename this function
func (i *Instance) dueForFetch() bool {
	// this just checks FSM state, the ticker must update it and do time
	// calcs
	if i.Status() == "READY_AND_DUE_FETCH" {
		return true
	}
	return false
}

func (i *Instance) isNowPastFetchTime() bool {
	return time.Now().After(i.NextFetch)
}

// Tick is responsible for pushing idle instance records between states.
// The instances will transition between states when doing stuff (e.g.
// investigating, fetching, et c) as well.
func (i *Instance) Tick() {
	if i.Status() == "READY_FOR_TOOTFETCH" {
		if i.isNowPastFetchTime() {
			i.Event("FETCH_TIME_REACHED")
		}
	} else if i.Status() == "STATUS_UNKNOWN" {
		i.Fetch()
	} else if i.Status() == "READY_AND_DUE_FETCH" {
		i.fetchRecentToots()
	}
}

func (i *Instance) nodeIdentified() bool {
	i.Lock()
	defer i.Unlock()
	if i.implementation > implUnknown {
		return true
	}
	return false
}

// DetectNodeTypeIfNecessary does some network requests if the node is as
// yet unidenfitied. No-op otherwise.
func (i *Instance) DetectNodeTypeIfNecessary() error {
	if !i.nodeIdentified() {
		return i.fetchNodeInfo()
	}
	return nil
}

func (i *Instance) registerError() {
	i.Lock()
	defer i.Unlock()
	i.ErrorCount++
}

func (i *Instance) registerSuccess() {
	i.Lock()
	defer i.Unlock()
	i.SuccessCount++
}

// Up returns true if the success count is >0
func (i *Instance) Up() bool {
	i.Lock()
	defer i.Unlock()
	return i.SuccessCount > 0
}

func (i *Instance) fetchNodeInfoURL() error {
	url := fmt.Sprintf("https://%s/.well-known/nodeinfo", i.Hostname)
	var c = &http.Client{
		Timeout: instanceNodeinfoTimeout,
	}

	log.Debug().
		Str("url", url).
		Str("hostname", i.Hostname).
		Msg("fetching nodeinfo reference URL")

	i.Event("BEGIN_NODEINFO_URL_FETCH")
	resp, err := c.Get(url)
	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msg("unable to fetch nodeinfo, node is down?")
		i.registerError()
		i.Event("EARLY_FETCH_ERROR")
		return err
	}

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

	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msg("unable to read nodeinfo")
		i.registerError()
		i.Event("EARLY_FETCH_ERROR")
		return err
	}

	nir := new(jsonapis.NodeInfoWellKnownResponse)
	err = json.Unmarshal(body, &nir)
	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msg("unable to parse nodeinfo, node is weird")
		i.registerError()
		i.Event("WEIRD_NODE_RESPONSE")
		return err
	}

	for _, item := range nir.Links {
		if item.Rel == nodeInfoSchemaVersionTwoName {
			log.Debug().
				Str("hostname", i.Hostname).
				Str("nodeinfourl", item.Href).
				Msg("success fetching url for nodeinfo")

			i.Lock()
			i.nodeInfoURL = item.Href
			i.Unlock()
			i.registerSuccess()
			i.Event("GOT_NODEINFO_URL")
			return nil
		}
		log.Debug().
			Str("hostname", i.Hostname).
			Str("item-rel", item.Rel).
			Str("item-href", item.Href).
			Msg("nodeinfo entry")
	}

	log.Error().
		Str("hostname", i.Hostname).
		Msg("incomplete nodeinfo")
	i.registerError()
	i.Event("WEIRD_NODE_RESPONSE")
	return errors.New("incomplete nodeinfo")
}

func (i *Instance) fetchNodeInfo() error {
	err := i.fetchNodeInfoURL()

	if err != nil {
		return err
	}

	var c = &http.Client{
		Timeout: instanceNodeinfoTimeout,
	}

	//FIXME make sure the nodeinfourl is on the same domain as the instance
	//hostname
	i.Lock()
	url := i.nodeInfoURL
	i.Unlock()

	i.Event("BEGIN_NODEINFO_FETCH")
	resp, err := c.Get(url)

	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to fetch nodeinfo data")
		i.registerError()
		i.Event("EARLY_FETCH_ERROR")
		return err
	}

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

	if err != nil {
		log.Error().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to read nodeinfo data")
		i.registerError()
		i.Event("EARLY_FETCH_ERROR")
		return err
	}

	ni := new(jsonapis.NodeInfoVersionTwoSchema)
	err = json.Unmarshal(body, &ni)
	if err != nil {
		log.Error().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to parse nodeinfo")
		i.registerError()
		i.Event("WEIRD_NODE_RESPONSE")
		return err
	}

	log.Debug().
		Str("serverVersion", ni.Software.Version).
		Str("software", ni.Software.Name).
		Str("hostname", i.Hostname).
		Str("nodeInfoURL", i.nodeInfoURL).
		Msg("received nodeinfo from instance")

	i.Lock()
	i.ServerVersionString = ni.Software.Version
	i.ServerImplementationString = ni.Software.Name
	ni.Software.Name = strings.ToLower(ni.Software.Name)

	if ni.Software.Name == "pleroma" {
		log.Debug().
			Str("hostname", i.Hostname).
			Str("software", ni.Software.Name).
			Msg("detected server software")
		i.Identified = true
		i.implementation = implPleroma
		i.Unlock()
		i.registerSuccess()
		i.Event("GOT_NODEINFO")
		return nil
	} else if ni.Software.Name == "mastodon" {
		log.Debug().
			Str("hostname", i.Hostname).
			Str("software", ni.Software.Name).
			Msg("detected server software")
		i.Identified = true
		i.implementation = implMastodon
		i.Unlock()
		i.registerSuccess()
		i.Event("GOT_NODEINFO")
		return nil
	} else {
		log.Error().
			Str("hostname", i.Hostname).
			Str("software", ni.Software.Name).
			Msg("FIXME unknown server implementation")
		i.Unlock()
		i.registerError()
		i.Event("WEIRD_NODE_RESPONSE")
		return errors.New("unknown server implementation")
	}
}

func (i *Instance) fetchRecentToots() error {
	// this would have been about a billion times shorter in python

	// it turns out pleroma supports the mastodon api so we'll just use that
	// for everything for now
	url := fmt.Sprintf("https://%s/api/v1/timelines/public?limit=40&local=true",
		i.Hostname)

	var c = &http.Client{
		Timeout: instanceHTTPTimeout,
	}

	i.Event("BEGIN_TOOT_FETCH")
	// we set the interval now to the error interval regardless here as a
	// safety against bugs to avoid fetching too frequently by logic
	// bug. if the fetch is successful, we will conditionally re-update the
	// next fetch to now+successInterval.
	i.setNextFetchAfter(instanceErrorInterval)
	resp, err := c.Get(url)

	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to fetch recent toots")
		i.registerError()
		i.Event("TOOT_FETCH_ERROR")
		return err
	}

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

	if err != nil {
		log.Debug().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to read recent toots from response")
		i.registerError()
		i.Event("TOOT_FETCH_ERROR")
		return err
	}

	tc, err := toot.NewTootCollectionFromMastodonAPIResponse(body, i.Hostname)

	if err != nil {
		log.Error().
			Str("hostname", i.Hostname).
			Err(err).
			Msgf("unable to parse recent toot list")
		i.registerError()
		i.Event("TOOT_FETCH_ERROR")
		return err
	}

	log.Info().
		Str("hostname", i.Hostname).
		Int("tootCount", len(tc)).
		Msgf("got and parsed toots")
	i.registerSuccess()
	i.Event("TOOTS_FETCHED")
	i.setNextFetchAfter(instanceSpiderInterval)

	// this should go fast as either the channel is buffered bigly or the
	// ingester receives fast and does its own buffering, but run it in its
	// own goroutine anyway because why not
	go i.sendTootsToIngester(tc)
	return nil
}

func (i *Instance) sendTootsToIngester(tc []*toot.Toot) {
	for _, item := range tc {
		i.tootDestination <- item
	}
}