[PATCH proxmox-mail-forward 5/5] only ever forward for one product, favoring PVE over PBS over PDM

[Lukas Wagner <l.wagner@proxmox.com>]

Co-installations of products should hopefully be not that common, but a
defined order might be easier to grasp for users than having to deal
with notifications being sent through multiple products.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>
---
 src/main.rs | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 92a2804..b089bb0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,6 +6,9 @@
 //! The message is passed via stdin.
 //! The binary is installed with setuid permissions and will thus run as
 //! root (euid ~ root, ruid ~ nobody)
+//!
+//! If multiple products are co-installed, only one of the products is ever responsible for
+//! forwarding the email. The order is PVE > PBS > PDM.
 
 use std::io::Read;
 use std::path::Path;
@@ -137,22 +140,18 @@ fn main() {
     // Read the mail that is to be forwarded from stdin
     match read_stdin() {
         Ok(mail) => {
-            // Assume a PVE installation if /etc/pve exists
             if Path::new(PVE_CFG_PATH).exists() {
+                // Assume a PVE installation if /etc/pve exists
                 if let Err(err) = forward_for_pve(&mail) {
                     error!("could not forward mail for Proxmox VE: {err:#}");
                 }
-            }
-
-            // Assume a PBS installation if /etc/proxmox-backup exists
-            if Path::new(PBS_CFG_PATH).exists() {
+            } else if Path::new(PBS_CFG_PATH).exists() {
+                // Assume a PBS installation if /etc/proxmox-backup exists
                 if let Err(err) = forward_for_pbs(&mail) {
                     error!("could not forward mail for Proxmox Backup Server: {err:#}");
                 }
-            }
-
-            // Assume a PDM installation if /etc/proxmox-datacenter-manager exists
-            if Path::new(PDM_CFG_PATH).exists() {
+            } else if Path::new(PDM_CFG_PATH).exists() {
+                // Assume a PDM installation if /etc/proxmox-datacenter-manager exists
                 if let Err(err) = forward_for_pdm(&mail) {
                     error!("could not forward mail for Proxmox Datacenter Manager: {err:#}");
                 }
-- 
2.47.3