package main

import (
    "fmt"
    "log"
    "strconv"
    "net/http"
    "github.com/PuerkitoBio/goquery"
)

// Custom user agent.
const (
    userAgent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) " +
        "AppleWebKit/537.36 (KHTML, like Gecko) " +
        "Chrome/53.0.2785.143 " +
        "Safari/537.36"
)

func getTrns() []string

// fetchUrl opens a url with GET method and sets a custom user agent.
// If url cannot be opened, then log it to a dedicated channel.
func fetchUrl(url string, chFailedUrls chan string, chIsFinished chan bool) {

    client := &http.Client{}
    req, _ := http.NewRequest("GET", url, nil)
    req.Header.Set("User-Agent", userAgent)
    resp, err := client.Do(req)
    if err != nil || resp.StatusCode != 200 {
        fmt.Println("Url failed:", url)
        chFailedUrls <- url
    }
    defer resp.Body.Close()

    doc, err := goquery.NewDocumentFromReader(resp.Body)
    if err != nil {
        log.Fatal(err)
    }
    doc.Find(".tournament-name").Each(
        func(index int, item *goquery.Selection) {
            trnLinkTag := item.Find("a")
            link, _ := trnLinkTag.Attr("href")
            fmt.Println(link)
    })

    defer func() {
        chIsFinished <- true
    }()
}

func main() {
    var first_year = 1980
    var last_year = 2018
    var base_url = "https://www.pgatour.com/tournaments/schedule.history."

    // Create 2 channels, 1 to track urls we could not open
    // and 1 to inform url fetching is done:
    chFailedUrls := make(chan string)
    chIsFinished := make(chan bool)
    urlsList := make([]string,0)

    // Open all urls concurrently using the 'go' keyword:
    for yr := first_year; yr <= last_year; yr++ {
        var url = base_url + strconv.Itoa(yr) + ".html"
        urlsList = append(urlsList, url)
        go fetchUrl(url, chFailedUrls, chIsFinished)
    }

    failedUrls := make([]string, 0)
    for i := 0; i < len(urlsList); {
        select {
        case url := <-chFailedUrls:
            failedUrls = append(failedUrls, url)
        case <-chIsFinished:
            i++
        }
    }
}