go-examples/tpl-ex3/main.go

package main

import (
	"encoding/csv"
	"html/template"
	"io"
	"log"
	"net/http"
	"os"
	"strconv"
)

var COLUMNS []string

type FinancialData struct {
	Date                                      string
	Open, High, Low, Close, Adj_Close, Volume float64
}

type TplData struct {
	Columns []string
	Rows    []FinancialData
}

func printHTML(tpl *template.Template, data []FinancialData, out io.Writer) {
	tplData := TplData{
		COLUMNS,
		data,
	}
	err := tpl.ExecuteTemplate(out, "tpl.html", tplData)
	if err != nil {
		panic(err)
	}
}

func readCsvLine(line []string) *FinancialData {
	data := new(FinancialData)
	for i, col := range line {
		switch COLUMNS[i] {
		case "Date":
			data.Date = col
		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)

	tpl, err := template.New("").Funcs(template.FuncMap{
		"class": func(index int) string {
			if index%2 == 0 {
				return "even"
			}
			return "odd"
		},
	}).ParseFiles("tpl.html", "script.js")
	if err != nil {
		panic(err)
	}
	http.HandleFunc("/", func(res http.ResponseWriter, req *http.Request) {
		printHTML(tpl, data, res)
	})
	http.ListenAndServe(":9000", nil)
}