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package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"os"
"strings"
"time"
)
// downloadCategory downloads the given category from celestrack
func downloadCategory(categoryName string) {
timeNow := time.Now().Unix()
// path where the category is stored
categoryPath := fmt.Sprintf("data/%s.txt", categoryName)
// conditions used to define if a new category should be downloaded or not
var nonexistant bool
var tooOld = false
// find out if the category all ready exists
if _, err := os.Stat(categoryPath); os.IsNotExist(err) {
nonexistant = true
} else {
// find out how old it is
categoryFileStat, _ := os.Stat(categoryPath)
categoryFileModTime := categoryFileStat.ModTime()
categoryFileModTimeUnix := categoryFileModTime.Unix()
if int(timeNow-categoryFileModTimeUnix) > categoryAgeThreshold {
tooOld = true
}
}
// if the local cache is too old or nonexistant, redownload
if tooOld || nonexistant {
log.Println("[c] cache to old, redownloading...")
// define where to download the TLEs from
base := "https://celestrak.com/NORAD/elements/"
downloadURL := fmt.Sprintf("%s%s.txt", base, categoryName)
// define the HTTP GET request and make it
resp, err := http.Get(downloadURL)
if err != nil {
log.Printf("Could not download %s", categoryName)
}
defer resp.Body.Close()
// read the respose from the GET request
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
log.Printf("Could not read the category %s", categoryName)
}
// write the response to the corresponding file
filename := fmt.Sprintf("data/%s.txt", categoryName)
f, err := os.Create(filename) // creating the file
if err != nil {
fmt.Printf("Could not create file data/%s.txt", categoryName)
}
_, err = f.WriteString(string(body)) // writing the TLE to the file
if err != nil {
fmt.Printf("Could not write to file data/%s.txt", categoryName)
}
log.Println("[c] Done.")
}
}
// dumpall dumps all the categories into the data folder
func dumpall() {
// read the name of the categories from the categories.txt file and write
// the result to the categories slice
content, err := ioutil.ReadFile("categories.txt")
if err != nil {
log.Printf("%s\n", "could not read categories.txt file!")
}
lines := strings.Split(string(content), "\n")
for _, line := range lines {
if line != "" {
categories = append(categories, line)
}
}
// download all the categories to the data/<category name> directory
for _, category := range categories {
log.Printf("downloading %s... ", category)
downloadCategory(category)
}
}
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