package strava

import (
	"bytes"
	"errors"
	"fmt"
	"net/url"
	"strconv"
	"time"

	"github.com/jftuga/geodist"
	"github.com/martinlehoux/biking_home/ride"
	"github.com/martinlehoux/kagamigo/kcore"
	"github.com/tkrajina/gpxgo/gpx"
)

const garminTrackPointExtensionNamespace = "http://www.garmin.com/xmlschemas/TrackPointExtension/v1"

var ErrNoTrackPoints = errors.New("activity has no track points")

type Activity struct {
	ID                  int64     `json:"id"`
	Name                string    `json:"name"`
	Type                string    `json:"type"`
	SportType           string    `json:"sport_type"`
	StartDate           time.Time `json:"start_date"`
	DistanceM           float64   `json:"distance"`
	MovingTimeS         int64     `json:"moving_time"`
	ElapsedTimeS        int64     `json:"elapsed_time"`
	TotalElevationGainM float64   `json:"total_elevation_gain"`
	AverageSpeedMps     float64   `json:"average_speed"`
}

func (c *Client) List(from, to time.Time) ([]Activity, error) {
	return c.list(from, to, "Ride", "MountainBikeRide")
}

func (c *Client) list(from, to time.Time, types ...string) ([]Activity, error) {
	allowed := map[string]bool{}
	for _, t := range types {
		allowed[t] = true
	}
	var all []Activity
	for page := 1; ; page++ {
		q := url.Values{}
		q.Set("per_page", "200")
		q.Set("page", strconv.Itoa(page))
		if !from.IsZero() {
			q.Set("after", strconv.FormatInt(from.Unix(), 10))
		}
		if !to.IsZero() {
			q.Set("before", strconv.FormatInt(to.Unix(), 10))
		}
		var batch []Activity
		err := c.GetJSON("/athlete/activities?"+q.Encode(), &batch)
		if err != nil {
			return nil, kcore.Wrap(err, "failed to list Strava activities")
		}
		if len(batch) == 0 {
			break
		}
		for _, activity := range batch {
			if len(allowed) == 0 || allowed[activity.Type] || allowed[activity.SportType] {
				all = append(all, activity)
			}
		}
		if len(batch) < 200 {
			break
		}
	}
	return all, nil
}

func (c *Client) Get(id int64) (Activity, []byte, []byte, error) {
	var activity Activity
	if err := c.GetJSON(fmt.Sprintf("/activities/%d", id), &activity); err != nil {
		return Activity{}, nil, nil, kcore.Wrap(err, "failed to get Strava activity")
	}
	streams, err := c.activityStreams(id)
	if err != nil {
		return Activity{}, nil, nil, err
	}
	gpxData, err := activityGPX(activity, streams)
	if err != nil {
		return activity, nil, nil, err
	}
	fitData, err := activityFIT(activity, streams)
	if err != nil {
		return activity, nil, nil, err
	}
	return activity, gpxData, fitData, nil
}

type activityStreams struct {
	LatLng    [][2]float64
	Altitude  []float64
	Seconds   []float64
	HeartRate []*float64
	Cadence   []*float64
	Power     []*float64
}

type nullableFloatStream struct {
	Data []*float64 `json:"data"`
}

func (c *Client) activityStreams(id int64) (activityStreams, error) {
	path := fmt.Sprintf("/activities/%d/streams?keys=latlng,altitude,time,heartrate,cadence,watts&key_by_type=true", id)
	var streams struct {
		LatLng *struct {
			Data [][2]float64 `json:"data"`
		} `json:"latlng"`
		Altitude *struct {
			Data []float64 `json:"data"`
		} `json:"altitude"`
		Time *struct {
			Data []float64 `json:"data"`
		} `json:"time"`
		HeartRate *nullableFloatStream `json:"heartrate"`
		Cadence   *nullableFloatStream `json:"cadence"`
		Power     *nullableFloatStream `json:"watts"`
	}
	err := c.GetJSON(path, &streams)
	if err != nil {
		return activityStreams{}, kcore.Wrap(err, "failed to fetch Strava streams")
	}
	result := activityStreams{}
	if streams.LatLng != nil {
		result.LatLng = streams.LatLng.Data
	}
	if streams.Altitude != nil {
		result.Altitude = streams.Altitude.Data
	}
	if streams.Time != nil {
		result.Seconds = streams.Time.Data
	}
	if streams.HeartRate != nil {
		result.HeartRate = streams.HeartRate.Data
	}
	if streams.Cadence != nil {
		result.Cadence = streams.Cadence.Data
	}
	if streams.Power != nil {
		result.Power = streams.Power.Data
	}
	return result, nil
}

func activityFIT(activity Activity, streams activityStreams) ([]byte, error) {
	if len(streams.LatLng) == 0 {
		return nil, ErrNoTrackPoints
	}
	n := len(streams.LatLng)
	distances := make([]float64, 0, n)
	elevations := make([]float64, 0, n)
	coords := make([]geodist.Coord, 0, n)
	timestamps := make([]time.Time, 0, n)
	heartRates := make([]float64, 0, n)
	cadences := make([]float64, 0, n)
	powers := make([]float64, 0, n)
	heartRateComplete := true
	cadenceComplete := true
	powerComplete := true

	distance := 0.0
	var previous *geodist.Coord
	for i := range n {
		coord := geodist.Coord{Lat: streams.LatLng[i][0], Lon: streams.LatLng[i][1]}
		if previous != nil {
			_, km := geodist.HaversineDistance(*previous, coord)
			d := km * 1000
			if d == 0 {
				continue
			}
			distance += d
		} else {
			distance = 0
		}
		previous = &coord

		var elev float64
		if i < len(streams.Altitude) {
			elev = streams.Altitude[i]
		}
		// If altitude missing and we have no value, use 0 to keep ride valid.
		// The GPX path requires elevation; this mirrors that requirement.
		distances = append(distances, distance)
		elevations = append(elevations, elev)
		coords = append(coords, coord)
		var ts time.Time
		if i < len(streams.Seconds) {
			ts = activity.StartDate.Add(time.Duration(streams.Seconds[i]) * time.Second)
		} else {
			ts = activity.StartDate.Add(time.Duration(i) * time.Second)
		}
		timestamps = append(timestamps, ts)

		if hr := streamValue(streams.HeartRate, i); hr == nil {
			heartRateComplete = false
			heartRates = append(heartRates, 0)
		} else {
			heartRates = append(heartRates, *hr)
		}
		if cad := streamValue(streams.Cadence, i); cad == nil {
			cadenceComplete = false
			cadences = append(cadences, 0)
		} else {
			cadences = append(cadences, *cad)
		}
		if pow := streamValue(streams.Power, i); pow == nil {
			powerComplete = false
			powers = append(powers, 0)
		} else {
			powers = append(powers, *pow)
		}
	}
	if len(distances) < 2 {
		return nil, errors.New("zero distance")
	}
	var hrCol, cadCol, powCol []float64
	if heartRateComplete {
		hrCol = heartRates
	}
	if cadenceComplete {
		cadCol = cadences
	}
	if powerComplete {
		powCol = powers
	}
	r := ride.FromColumnsWithMetrics(distances, elevations, coords, timestamps, hrCol, cadCol, powCol)

	var buf bytes.Buffer
	if err := ride.EncodeFIT(r, &buf); err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func activityGPX(activity Activity, streams activityStreams) ([]byte, error) {
	if len(streams.LatLng) == 0 {
		return nil, ErrNoTrackPoints
	}
	points := make([]gpx.GPXPoint, len(streams.LatLng))
	for i := range streams.LatLng {
		point := gpx.GPXPoint{
			Latitude:  streams.LatLng[i][0],
			Longitude: streams.LatLng[i][1],
		}
		if i < len(streams.Altitude) {
			point.Elevation = *gpx.NewNullableFloat64(streams.Altitude[i])
		}
		if i < len(streams.Seconds) {
			point.Timestamp = activity.StartDate.Add(time.Duration(streams.Seconds[i]) * time.Second)
		}
		addTrackPointMetric(&point, "hr", streamValue(streams.HeartRate, i))
		addTrackPointMetric(&point, "cad", streamValue(streams.Cadence, i))
		addTrackPointMetric(&point, "watts", streamValue(streams.Power, i))
		points[i] = point
	}
	doc := gpx.GPX{
		Version: "1.1",
		Creator: "biking_home",
		Name:    activity.Name,
		Tracks: []gpx.GPXTrack{{
			Name:     activity.Name,
			Segments: []gpx.GPXTrackSegment{{Points: points}},
		}},
	}
	doc.RegisterNamespace("gpxtpx", garminTrackPointExtensionNamespace)
	xmlData, err := doc.ToXml(gpx.ToXmlParams{})
	if err != nil {
		return nil, kcore.Wrap(err, "failed to build GPX XML")
	}
	return xmlData, nil
}

func streamValue(stream []*float64, i int) *float64 {
	if i >= len(stream) {
		return nil
	}
	return stream[i]
}

func addTrackPointMetric(point *gpx.GPXPoint, name string, value *float64) {
	if value == nil {
		return
	}
	extension := point.Extensions.GetOrCreateNode(gpx.NamespaceURL(garminTrackPointExtensionNamespace), "TrackPointExtension")
	extension.GetOrCreateNode(name).Data = strconv.FormatFloat(*value, 'f', -1, 64)
}