Check that account exists before posting version

This was requested by Lee in WDT due to errors on their end when a
version update is received for a callsign without a valid account.

Closes la5nta#213

internal/cmsapi/api.go

@@ -20,6 +20,7 @@ const (
 	RootURL           = "https://api.winlink.org"
 	PathVersionAdd    = "/version/add"
 	PathGatewayStatus = "/gateway/status.json"
+	PathAccountExists = "/account/exists"
 
 	// Issued December 2017 by the WDT for use with Pat
 	AccessKey = "1880278F11684B358F36845615BD039A"
@@ -59,6 +60,19 @@ func (v VersionAdd) Post() error {
 	return nil
 }
 
+func AccountExists(callsign string) (bool, error) {
+	url := RootURL + PathAccountExists + "?key=" + AccessKey + "&callsign=" + url.QueryEscape(callsign)
+	req, _ := http.NewRequest("GET", url, nil)
+	req.Header.Set("Accept", "application/json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return false, err
+	}
+	defer resp.Body.Close()
+	var obj struct{ CallsignExists bool }
+	return obj.CallsignExists, json.NewDecoder(resp.Body).Decode(&obj)
+}
+
 type GatewayStatus struct {
 	ServerName string    `json:"ServerName"`
 	ErrorCode  int       `json:"ErrorCode"`

version_report.go

@@ -15,20 +15,58 @@ import (
 	"github.com/la5nta/pat/internal/cmsapi"
 )
 
+func accountExistsCached(callsign string) (bool, error) {
+	var cache struct {
+		Expires       time.Time
+		AccountExists bool
+	}
+
+	f, err := os.OpenFile(path.Join(appDir, fmt.Sprintf(".cached_account_check_%s.json", callsign)), os.O_RDWR|os.O_CREATE, 0600)
+	if err != nil {
+		return false, err
+	}
+	json.NewDecoder(f).Decode(&cache)
+	if time.Since(cache.Expires) < 0 {
+		return cache.AccountExists, nil
+	}
+	defer func() {
+		f.Truncate(0)
+		f.Seek(0, 0)
+		json.NewEncoder(f).Encode(cache)
+	}()
+
+	exists, err := cmsapi.AccountExists(callsign)
+	if !exists || err != nil {
+		// Let's try again in 48 hours
+		cache.Expires = time.Now().Add(48 * time.Hour)
+		return false, err
+	}
+
+	// Keep this response for a month. It will probably not change.
+	cache.Expires = time.Now().Add(30 * 24 * time.Hour)
+	cache.AccountExists = exists
+	return exists, err
+}
+
 func postVersionUpdate() error {
 	var lastUpdated time.Time
 	file, err := os.OpenFile(path.Join(appDir, "last_version_report.json"), os.O_RDWR|os.O_CREATE, 0600)
 	if err != nil {
 		return err
 	}
 	defer file.Close()
-
 	json.NewDecoder(file).Decode(&lastUpdated)
-
 	if time.Since(lastUpdated) < 24*time.Hour {
 		return nil
 	}
 
+	// WDT do not want us to post version reports for callsigns without a registered account
+	if exists, err := accountExistsCached(fOptions.MyCall); err != nil {
+		return err
+	} else if !exists {
+		return nil
+	}
+
 	v := cmsapi.VersionAdd{
 		Callsign: fOptions.MyCall,
 		Program:  AppName,