go-examples/financialjson/main.go

package main

import "encoding/csv"
import "encoding/json"
import "time"
import "io"
import "log"
import "os"
import "strconv"

var COLUMNS []string

type FinancialData struct {
	Date                                      time.Time
	Open, High, Low, Close, Adj_Close, Volume float64
}

func readCsvLine(line []string) *FinancialData {
	data := new(FinancialData)
	for i, col := range line {
		switch COLUMNS[i] {
		case "Date":
			d, err := time.Parse("2006-01-02", col)
			if err != nil {
				panic(err)
			} else {
				data.Date = d
			}
		case "Open":
			data.Open = toFloat(col)
		case "High":
			data.High = toFloat(col)
		case "Low":
			data.Low = toFloat(col)
		case "Close":
			data.Close = toFloat(col)
		case "Adj Close":
			data.Adj_Close = toFloat(col)
		case "Volume":
			data.Volume = toFloat(col)
		}
	}
	return data
}

func toFloat(v string) float64 {
	f, err := strconv.ParseFloat(v, 64)
	if err != nil {
		log.Fatalln(err)
	}
	return f
}

func readCsvHeader(line []string) {
	for _, col := range line {
		COLUMNS = append(COLUMNS, col)
	}
}

func readCsv(in io.Reader) []FinancialData {
	data := []FinancialData{}
	csvReader := csv.NewReader(in)
	for {
		line, err := csvReader.Read()
		if err == io.EOF {
			break
		} else if err != nil {
			log.Fatal(err)
		}
		if len(COLUMNS) == 0 {
			readCsvHeader(line)
		} else {
			data = append(data, *readCsvLine(line))
		}
	}
	return data

}

func main() {
	if len(os.Args) < 2 {
		log.Fatalln("Usage go-financial <file>")
	}

	// read input
	csv, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln("Error reading file", err)
	}
	defer csv.Close()

	// parse data
	data := readCsv(csv)

	// convert JSON
	var writer io.Writer
	if len(os.Args) > 2 {
		f, ferr := os.Create(os.Args[2])
		if ferr != nil {
			panic(ferr)
		}
		defer f.Close()
		writer = f
	} else {
		writer = os.Stdout
	}
	err = json.NewEncoder(writer).Encode(data)
	if err != nil {
		panic(err)
	}

}