package kraftakt

import (
	"context"
	"encoding/json"
	"fmt"
	"html/template"
	"io/ioutil"
	"net/http"
	"sync"
	"time"

	"github.com/octo/kraftakt/app"
	"github.com/octo/kraftakt/fitbit"
	"github.com/octo/kraftakt/gfit"
	"google.golang.org/appengine"
	"google.golang.org/appengine/datastore"
	"google.golang.org/appengine/delay"
	"google.golang.org/appengine/log"
	"google.golang.org/appengine/user"
)

var delayedHandleNotifications = delay.Func("handleNotifications", handleNotifications)

var templates *template.Template

func init() {
	http.Handle("/login", AuthenticatedHandler(loginHandler))
	http.Handle("/fitbit/connect", AuthenticatedHandler(fitbitConnectHandler))
	http.Handle("/fitbit/grant", AuthenticatedHandler(fitbitGrantHandler))
	http.Handle("/fitbit/disconnect", AuthenticatedHandler(fitbitDisconnectHandler))
	http.Handle("/google/connect", AuthenticatedHandler(googleConnectHandler))
	http.Handle("/google/grant", AuthenticatedHandler(googleGrantHandler))
	http.Handle("/google/disconnect", AuthenticatedHandler(googleDisconnectHandler))
	// unauthenticated
	http.Handle("/fitbit/notify", ContextHandler(fitbitNotifyHandler))
	http.Handle("/", ContextHandler(indexHandler))

	t, err := template.ParseGlob("templates/*.html")
	if err != nil {
		panic(err)
	}
	templates = t
}

func internalServerError(ctx context.Context, w http.ResponseWriter, err error) {
	log.Errorf(ctx, "%v", err)

	http.Error(w, "Internal Server Error\n\nReference: "+appengine.RequestID(ctx), http.StatusInternalServerError)
}

// ContextHandler implements http.Handler
type ContextHandler func(context.Context, http.ResponseWriter, *http.Request) error

func (hndl ContextHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ctx := appengine.NewContext(r)

	if err := app.LoadConfig(ctx); err != nil {
		internalServerError(ctx, w, fmt.Errorf("LoadConfig() = %v", err))
		return
	}

	if err := hndl(ctx, w, r); err != nil {
		internalServerError(ctx, w, err)
		return
	}
}

type AuthenticatedHandler func(context.Context, http.ResponseWriter, *http.Request, *app.User) error

func (hndl AuthenticatedHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ctx := appengine.NewContext(r)

	if err := app.LoadConfig(ctx); err != nil {
		internalServerError(ctx, w, fmt.Errorf("LoadConfig() = %v", err))
		return
	}

	gaeUser := user.Current(ctx)
	if gaeUser == nil {
		url, err := user.LoginURL(ctx, r.URL.String())
		if err != nil {
			internalServerError(ctx, w, fmt.Errorf("LoginURL() = %v", err))
			return
		}
		http.Redirect(w, r, url, http.StatusTemporaryRedirect)
		return
	}

	u, err := app.NewUser(ctx, gaeUser.Email)
	if err != nil {
		internalServerError(ctx, w, fmt.Errorf("NewUser(%q) = %v", gaeUser.Email, err))
		return
	}

	if err := hndl(ctx, w, r, u); err != nil {
		internalServerError(ctx, w, err)
		return
	}
}

func indexHandler(ctx context.Context, w http.ResponseWriter, _ *http.Request) error {
	var templateData struct {
		HaveFitbit    bool
		HaveGoogleFit bool
		*app.User
	}
	templateName := "main.html"

	if gaeUser := user.Current(ctx); gaeUser != nil {
		templateName = "loggedin.html"

		u, err := app.NewUser(ctx, gaeUser.Email)
		if err != nil {
			return err
		}
		templateData.User = u

		_, err = u.Token(ctx, "Fitbit")
		if err != nil && err != datastore.ErrNoSuchEntity {
			return err
		}
		templateData.HaveFitbit = (err == nil)

		_, err = u.Token(ctx, "Google")
		if err != nil && err != datastore.ErrNoSuchEntity {
			return err
		}
		templateData.HaveGoogleFit = (err == nil)
	}

	return templates.ExecuteTemplate(w, templateName, &templateData)
}

func loginHandler(_ context.Context, w http.ResponseWriter, r *http.Request, _ *app.User) error {
	// essentially a nop; all the heavy lifting (i.e. logging in) has been done by the AuthenticatedHandler wrapper.
	redirectURL := r.URL
	redirectURL.Path = "/"
	redirectURL.RawQuery = ""
	redirectURL.Fragment = ""
	http.Redirect(w, r, redirectURL.String(), http.StatusTemporaryRedirect)
	return nil
}

func fitbitConnectHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	http.Redirect(w, r, fitbit.AuthURL(ctx, u), http.StatusTemporaryRedirect)
	return nil
}

func fitbitGrantHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	if err := fitbit.ParseToken(ctx, r, u); err != nil {
		return err
	}
	c, err := fitbit.NewClient(ctx, "", u)
	if err != nil {
		return err
	}

	for _, collection := range []string{"activities", "sleep"} {
		if err := c.Subscribe(ctx, collection); err != nil {
			return fmt.Errorf("c.Subscribe(%q) = %v", collection, err)
		}
		log.Infof(ctx, "Successfully subscribed to %q", collection)
	}

	redirectURL := r.URL
	redirectURL.Path = "/"
	redirectURL.RawQuery = ""
	redirectURL.Fragment = ""
	http.Redirect(w, r, redirectURL.String(), http.StatusTemporaryRedirect)
	return nil
}

func fitbitDisconnectHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	c, err := fitbit.NewClient(ctx, "", u)
	if err != nil {
		return err
	}

	if err := c.UnsubscribeAll(ctx); err != nil {
		return fmt.Errorf("UnsubscribeAll() = %v", err)
	}

	if err := c.DeleteToken(ctx); err != nil {
		return err
	}

	redirectURL := r.URL
	redirectURL.Path = "/"
	redirectURL.RawQuery = ""
	redirectURL.Fragment = ""
	http.Redirect(w, r, redirectURL.String(), http.StatusTemporaryRedirect)
	return nil
}

func googleConnectHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	http.Redirect(w, r, gfit.AuthURL(ctx, u), http.StatusTemporaryRedirect)
	return nil
}

func googleGrantHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	if err := gfit.ParseToken(ctx, r, u); err != nil {
		return err
	}

	redirectURL := r.URL
	redirectURL.Path = "/"
	redirectURL.RawQuery = ""
	redirectURL.Fragment = ""
	http.Redirect(w, r, redirectURL.String(), http.StatusTemporaryRedirect)
	return nil
}

func googleDisconnectHandler(ctx context.Context, w http.ResponseWriter, r *http.Request, u *app.User) error {
	c, err := gfit.NewClient(ctx, u)
	if err != nil {
		return err
	}

	if err := c.DeleteToken(ctx); err != nil {
		return err
	}

	redirectURL := r.URL
	redirectURL.Path = "/"
	redirectURL.RawQuery = ""
	redirectURL.Fragment = ""
	http.Redirect(w, r, redirectURL.String(), http.StatusTemporaryRedirect)
	return nil
}

// fitbitNotifyHandler is called by Fitbit whenever there are updates to a
// subscription. It verifies the payload, splits it into individual
// notifications and adds it to the taskqueue service.
func fitbitNotifyHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) error {
	defer r.Body.Close()

	fitbitTimeout := 3 * time.Second
	ctx, cancel := context.WithTimeout(ctx, fitbitTimeout)
	defer cancel()

	// this is used when setting up a new subscriber in the UI. Once set
	// up, this code path should not be triggered.
	if verify := r.FormValue("verify"); verify != "" {
		if verify == app.Config.FitbitSubscriberCode {
			w.WriteHeader(http.StatusNoContent)
		} else {
			w.WriteHeader(http.StatusNotFound)
		}
		return nil
	}

	data, err := ioutil.ReadAll(r.Body)
	if err != nil {
		return err
	}

	// Fitbit recommendation: "If signature verification fails, you should
	// respond with a 404"
	if !fitbit.CheckSignature(ctx, data, r.Header.Get("X-Fitbit-Signature")) {
		log.Errorf(ctx, "signature mismatch")
		w.WriteHeader(http.StatusNotFound)
		return nil
	}

	if err := delayedHandleNotifications.Call(ctx, data); err != nil {
		return err
	}

	w.WriteHeader(http.StatusCreated)
	return nil
}

// handleNotifications parses fitbit notifications and requests the individual
// activities from Fitbit. It is executed asynchronously via the delay package.
func handleNotifications(ctx context.Context, payload []byte) error {
	log.Debugf(ctx, "NOTIFY -> %s", payload)

	if err := app.LoadConfig(ctx); err != nil {
		return err
	}

	var subscriptions []fitbit.Subscription
	if err := json.Unmarshal(payload, &subscriptions); err != nil {
		return err
	}

	wg := &sync.WaitGroup{}

	for _, s := range subscriptions {
		switch s.CollectionType {
		case "activities":
			wg.Add(1)
			go func(s fitbit.Subscription) {
				defer wg.Done()
				if err := activitiesNotification(ctx, &s); err != nil {
					log.Warningf(ctx, "activitiesNotification() = %v", err)
				}
			}(s) // copies s
		case "sleep":
			wg.Add(1)
			go func(s fitbit.Subscription) {
				defer wg.Done()
				if err := sleepNotification(ctx, &s); err != nil {
					log.Warningf(ctx, "sleepNotification() = %v", err)
				}
			}(s) // copies s
		default:
			log.Warningf(ctx, "ignoring collection type %q", s.CollectionType)

		}
	}

	wg.Wait()
	return nil
}

func activitiesNotification(ctx context.Context, s *fitbit.Subscription) error {
	u, err := fitbit.UserFromSubscriberID(ctx, s.SubscriptionID)
	if err != nil {
		return err
	}

	fitbitClient, err := fitbit.NewClient(ctx, s.OwnerID, u)
	if err != nil {
		return err
	}

	var (
		wg      = &sync.WaitGroup{}
		errs    appengine.MultiError
		summary *fitbit.ActivitySummary
		profile *fitbit.Profile
	)

	wg.Add(1)
	go func() {
		var err error
		summary, err = fitbitClient.ActivitySummary(ctx, s.Date)
		if err != nil {
			errs = append(errs, fmt.Errorf("fitbitClient.ActivitySummary(%q) = %v", s.Date, err))
		}
		wg.Done()
	}()

	wg.Add(1)
	go func() {
		var err error
		profile, err = fitbitClient.Profile(ctx)
		if err != nil {
			errs = append(errs, fmt.Errorf("fitbitClient.Profile(%q) = %v", s.Date, err))
		}
		wg.Done()
	}()

	wg.Wait()
	if len(errs) != 0 {
		return errs
	}

	tm, err := time.ParseInLocation("2006-01-02", s.Date, profile.Timezone)
	if err != nil {
		return err
	}

	log.Debugf(ctx, "%s (%s) took %d steps on %s",
		profile.Name, u.Email, summary.Summary.Steps, tm)

	gfitClient, err := gfit.NewClient(ctx, u)
	if err != nil {
		return err
	}

	wg.Add(1)
	go func() {
		if err := gfitClient.SetSteps(ctx, summary.Summary.Steps, tm); err != nil {
			errs = append(errs, fmt.Errorf("gfitClient.SetSteps(%d) = %v", summary.Summary.Steps, err))
		}
		wg.Done()
	}()

	wg.Add(1)
	go func() {
		if err := gfitClient.SetCalories(ctx, summary.Summary.CaloriesOut, tm); err != nil {
			errs = append(errs, fmt.Errorf("gfitClient.SetCalories(%d) = %v", summary.Summary.CaloriesOut, err))
		}
		wg.Done()
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()

		var distanceMeters float64
		for _, d := range summary.Summary.Distances {
			if d.Activity != "total" {
				continue
			}
			distanceMeters = 1000.0 * d.Distance
			break
		}
		if err := gfitClient.SetDistance(ctx, distanceMeters, tm); err != nil {
			errs = append(errs, fmt.Errorf("gfitClient.SetDistance(%g) = %v", distanceMeters, err))
			return
		}
	}()

	wg.Add(1)
	go func() {
		if err := gfitClient.SetHeartRate(ctx, summary.Summary.HeartRateZones, summary.Summary.RestingHeartRate, tm); err != nil {
			errs = append(errs, fmt.Errorf("gfitClient.SetHeartRate() = %v", err))
		}
		wg.Done()
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()

		var activities []gfit.Activity
		for _, a := range summary.Activities {
			if !a.HasStartTime {
				continue
			}

			startTime, err := time.ParseInLocation("2006-01-02T15:04", a.StartDate+"T"+a.StartTime, profile.Timezone)
			if err != nil {
				errs = append(errs, fmt.Errorf("gfitClient.SetActivities() = %v", err))
				return
			}
			endTime := startTime.Add(time.Duration(a.Duration) * time.Millisecond)

			activities = append(activities, gfit.Activity{
				Start: startTime,
				End:   endTime,
				Type:  a.Name,
			})
		}
		if err := gfitClient.SetActivities(ctx, activities, tm); err != nil {
			errs = append(errs, fmt.Errorf("gfitClient.SetActivities() = %v", err))
			return
		}
	}()

	wg.Wait()

	if len(errs) != 0 {
		return errs
	}
	return nil
}

func sleepNotification(ctx context.Context, s *fitbit.Subscription) error {
	u, err := fitbit.UserFromSubscriberID(ctx, s.SubscriptionID)
	if err != nil {
		return err
	}

	var (
		wg         = &sync.WaitGroup{}
		gfitClient *gfit.Client
		gfitErr    error
	)

	wg.Add(1)
	go func() {
		gfitClient, gfitErr = gfit.NewClient(ctx, u)
		wg.Done()
	}()

	fitbitClient, err := fitbit.NewClient(ctx, s.OwnerID, u)
	if err != nil {
		return err
	}

	profile, err := fitbitClient.Profile(ctx)
	if err != nil {
		return err
	}

	tm, err := time.ParseInLocation("2006-01-02", s.Date, profile.Timezone)
	if err != nil {
		return err
	}

	sleep, err := fitbitClient.Sleep(ctx, tm)
	if err != nil {
		return err
	}
	log.Debugf(ctx, "fitbitClient.Sleep(%v) returned %d sleep stages", tm, len(sleep.Stages))

	var activities []gfit.Activity
	for _, stg := range sleep.Stages {
		a := gfit.Activity{
			Start: stg.StartTime,
			End:   stg.EndTime,
		}
		switch stg.Level {
		case fitbit.SleepLevelDeep:
			a.Type = "Deep sleep"
		case fitbit.SleepLevelLight:
			a.Type = "Light sleep"
		case fitbit.SleepLevelREM:
			a.Type = "REM sleep"
		case fitbit.SleepLevelWake:
			a.Type = "Awake (during sleep cycle)"
		default:
			log.Warningf(ctx, "unexpected sleep level %v", stg.Level)
			continue
		}

		activities = append(activities, a)
	}

	wg.Wait()
	if gfitErr != nil {
		return gfitErr
	}

	log.Debugf(ctx, "passing %d activities to gfitClient.SetActivities()", len(activities))
	if err := gfitClient.SetActivities(ctx, activities, tm); err != nil {
		return fmt.Errorf("SetActivities() = %v", err)
	}

	return nil
}