history.go

// Package ystocks implements a library for using the Yahoo! Finance stock
// market API.
package ystocks

import (
	"encoding/csv"
	"fmt"
	"net/http"
	"strconv"
	"time"
)

// Inverted index for months; given a Month it will return the integer
// 'index' of the month minus 1 (I don't know... Can't seem to find a way to
// go backwards from Month->int in the Go API. And even more I don't know...
// Yahoo! Finance API seems to take the month minus 1... Maybe I'm missing
// something?... Odd. Whatever...).
var monthsInverted = map[time.Month]int{
	time.January:   0,
	time.February:  1,
	time.March:     2,
	time.April:     3,
	time.May:       4,
	time.June:      5,
	time.July:      6,
	time.August:    7,
	time.September: 8,
	time.October:   9,
	time.November:  10,
	time.December:  11,
}

// Constants with URL parts for API call building.
const (
	historyBaseUrl = "http://ichart.yahoo.com/table.csv?s="
	fromMonth      = "&a="
	fromDay        = "&b="
	fromYear       = "&c="
	toMonth        = "&d="
	toDay          = "&e="
	toYear         = "&f"
	interval       = "&g="
	endUrl         = "&ignore=.csv"
)

// Time interval type, see interval constants later.
type TimeInterval string

// Interval constants for daily, monthly, and weekly stock histories (thanks to
// http://code.google.com/p/yahoo-finance-managed/wiki/enumHistQuotesInterval).
const (
	DailyInterval   = "d"
	WeeklyInterval  = "w"
	MonthlyInterval = "m"
)

// Stock history data type.
type StockHistory struct {
	from     time.Time
	to       time.Time
	interval TimeInterval
	prices   []int
}

func (s *Stock) getHistory(from time.Time, to time.Time, i TimeInterval) (StockHistory, error) {
	url := historyBaseUrl + s.id +
		fromMonth + strconv.Itoa(monthsInverted[from.Month()]) +
		fromDay + strconv.Itoa(from.Day()) +
		fromYear + strconv.Itoa(from.Year()) +
		toMonth + strconv.Itoa(monthsInverted[to.Month()]) +
		toDay + strconv.Itoa(to.Day()) +
		toYear + strconv.Itoa(to.Year()) +
		interval + string(i) +
		endUrl

	// HTTP GET the CSV data
	resp, httpErr := http.Get(url)
	defer resp.Body.Close()
	if httpErr != nil {
		return nil, httpErr
	}

	// Convert string CSV data to a usable data structure
	reader := csv.NewReader(resp.Body)
	records, parseErr := reader.ReadAll()
	if parseErr != nil {
		return nil, parseErr
	}

	fmt.Println(records)

	// TODO
	prices := []int{0}
	hist := StockHistory{from, to, i, prices}
	return hist, nil
}