feat: Implemented the download of eQSL

internal/extsvc/eqsl.go

@@ -53,6 +53,91 @@ func eqslPost(ctx context.Context, client *http.Client, user, pswd, adif string)
 	return msg, nil
 }
 
+// eQSL Inbox download endpoint + base host. DownloadInBox.cfm builds an ADIF of
+// the account's *received* eQSLs (confirmations) and returns an HTML page that
+// links to the generated .adi file; we then fetch that file (two-step API).
+const (
+	eqslDownloadInboxURL = "https://www.eQSL.cc/qslcard/DownloadInBox.cfm"
+	eqslBaseURL          = "https://www.eQSL.cc"
+)
+
+// eqslAdiHrefRe pulls the generated .adi path out of the DownloadInBox reply,
+// e.g. `<A HREF="/qslcard/downloadedfiles/xxxx.adi">`.
+var eqslAdiHrefRe = regexp.MustCompile(`(?i)href="(/[^"]+\.adi)"`)
+
+// DownloadEQSLConfirmations fetches the account's Inbox (received eQSLs =
+// confirmations) as ADIF text. since is "YYYY-MM-DD" (only QSLs received since
+// then, incremental "last download"); qthNick comes from the config when the
+// account has several QTH profiles.
+func DownloadEQSLConfirmations(ctx context.Context, client *http.Client, cfg ServiceConfig, since string) (string, error) {
+	user := strings.ToUpper(strings.TrimSpace(cfg.Username))
+	if user == "" || strings.TrimSpace(cfg.Password) == "" {
+		return "", fmt.Errorf("eqsl: username/password not set")
+	}
+	if client == nil {
+		client = &http.Client{Timeout: 120 * time.Second}
+	}
+	q := url.Values{}
+	q.Set("UserName", user)
+	q.Set("Password", cfg.Password)
+	if nick := strings.TrimSpace(cfg.QTHNickname); nick != "" {
+		q.Set("QTHNickname", nick)
+	}
+	if s := eqslRcvdSince(since); s != "" {
+		q.Set("RcvdSince", s) // eQSL wants YYYYMMDDHHMM
+	}
+
+	// Step 1: ask eQSL to build the inbox ADIF; the reply is HTML linking to it.
+	page, err := eqslGet(ctx, client, eqslDownloadInboxURL+"?"+q.Encode())
+	if err != nil {
+		return "", err
+	}
+	if reason := authErrEQSL(page); reason != "" {
+		return "", fmt.Errorf("eqsl: %s", reason)
+	}
+	m := eqslAdiHrefRe.FindStringSubmatch(page)
+	if m == nil {
+		// eQSL reports problems inline ("Error: …", or "no QSLs" wording).
+		return "", fmt.Errorf("eqsl: no download link in response: %s", eqslReason(page))
+	}
+
+	// Step 2: fetch the generated .adi file.
+	adif, err := eqslGet(ctx, client, eqslBaseURL+m[1])
+	if err != nil {
+		return "", fmt.Errorf("eqsl: fetch adif: %w", err)
+	}
+	return adif, nil
+}
+
+// eqslGet does a plain GET and returns the body as text (32 MB cap), erroring on
+// a non-200 status.
+func eqslGet(ctx context.Context, client *http.Client, u string) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+	if err != nil {
+		return "", fmt.Errorf("eqsl: build request: %w", err)
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("eqsl: request failed: %w", err)
+	}
+	defer resp.Body.Close()
+	b, _ := io.ReadAll(io.LimitReader(resp.Body, 32*1024*1024))
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("eqsl: http %d", resp.StatusCode)
+	}
+	return string(b), nil
+}
+
+// eqslRcvdSince converts the app's "YYYY-MM-DD" into eQSL's RcvdSince format
+// "YYYYMMDDHHMM" (midnight). Empty in → empty out (full pull).
+func eqslRcvdSince(since string) string {
+	s := strings.ReplaceAll(strings.TrimSpace(since), "-", "")
+	if len(s) == 8 { // YYYYMMDD → append 0000 (00:00)
+		return s + "0000"
+	}
+	return s
+}
+
 // authErrEQSL returns a reason when the response signals bad credentials, else
 // "". eQSL replies "Error: No match on eQSL_User/eQSL_Pswd".
 func authErrEQSL(body string) string {