Beginnings of an App Engine app to ingest Flywheel spreadsheets and produce JSON which can be played with using D3 (see https://gist.github.com/ImJasonH/5535583)

flywheel.go

package flywheel

import (
	"archive/zip"
	"encoding/json"
	"fmt"
	"log"
	"strconv"
	"time"

	"github.com/tealeg/xlsx"
)

type Data struct {
	Data []Row `json:"data"`
	//Avg   Row `json:"avg"`
	//Total Row `json:"avg"`
	//Min   Row `json:"min"`
	//Max   Row `json:"max"`
}

type Row struct {
	Time       int64   `json:"time"`
	Studio     string  `json:"studio"`
	Instructor string  `json:"instructor"`
	AvgRPM     int     `json:"avgRpm"`
	MaxRPM     int     `json:"maxRpm"`
	AvgTorq    int     `json:"avgTorq"`
	MaxTorq    int     `json:"maxTorq"`
	AvgSpeed   int     `json:"avgSpeed"`
	Duration   float64 `json:"duration"`
	Power      int     `json:"power"`
	Distance   int     `json:"distance"`
	MinCal     int     `json:"minCal"`
	MaxCal     int     `json:"maxCal"`
}

func Convert(z zip.ReadCloser) []byte {
	x, err := xlsx.ReadZip(filename)
	if err != nil {
		log.Fatal(err)
	}

	data := Data{}
	rows := []Row{}

	for i := 1; i < len(x.Sheets[0].Rows); i++ {
		cells := x.Sheets[0].Rows[i].Cells

		row := new(Row)
		dateStr := fmt.Sprintf("%s %s", cells[0].Value, cells[1].Value)
		t, err := time.Parse("20060102 15:04", dateStr)
		if err != nil {
			log.Fatal(err)
		}
		row.Time = t.Unix()

		row.Studio = cells[2].Value
		row.Instructor = cells[3].Value
		row.AvgRPM = toInt(cells[4].Value)
		row.MaxRPM = toInt(cells[5].Value)
		row.AvgTorq = toInt(cells[6].Value)
		row.MaxTorq = toInt(cells[7].Value)
		row.AvgSpeed = toInt(cells[8].Value)
		row.Duration = toFloat(cells[9].Value)
		row.Power = toInt(cells[10].Value)
		row.Distance = toInt(cells[11].Value)
		row.MinCal = toInt(cells[12].Value)
		row.MaxCal = toInt(cells[13].Value)
		rows = append(rows, *row)
	}
	data.Data = rows

	b, err := json.Marshal(data)
	if err != nil {
		log.Fatal(err)
	}
	return b
}

func toInt(s string) int {
	i, err := strconv.ParseInt(s, 10, 0)
	if err != nil {
		log.Fatal(err)
	}
	return int(i)
}

func toFloat(s string) float64 {
	i, err := strconv.ParseFloat(s, 0)
	if err != nil {
		log.Fatal(err)
	}
	return i
}

handler.go

package flywheel

import (
	"archive/zip"
	"net/http"
	"strings"
)

const maxBytes = 2 >> 20

func init() {
	http.HandleFunc("/upload", handleUpload)
}

func handleUpload(w http.ResponseWriter, r *http.Request) {
	r.ParseMultipartForm(maxBytes)
	f, fh, err := r.FormFile("file")
	if err != nil || !strings.HasSuffix(fh.Filename, ".xlsx") {
		http.Error(w, "Invalid file", http.StatusBadRequest)
		return
	}
	z, err = zip.NewReader(f, r.ContentLength)
	if err != nil {
		http.Error(w, "Invalid file", http.StatusBadRequest)
		return
	}
	w.Write(Convert(z))
}