job: new API for dynamic job creation

Job::new() can be used to create jobs in-memory

Job.update() is replaced with Job.save() which can create new database
entries and consumes Job to avoid the need to update job ID after saving
it to the database.

src/job.rs

@@ -162,18 +162,41 @@ impl fmt::Display for Job {
 }
 
 impl Job {
+    fn new(action: Action, foreign_id: u32, param: Params, delay_seconds: i64) -> Self {
+        let timestamp = time();
+
+        Self {
+            job_id: 0,
+            action,
+            foreign_id,
+            desired_timestamp: timestamp + delay_seconds,
+            added_timestamp: timestamp,
+            tries: 0,
+            param,
+            pending_error: None,
+        }
+    }
+
     /// Deletes the job from the database.
     fn delete(&self, context: &Context) -> bool {
+        if self.job_id != 0 {
             context
                 .sql
                 .execute("DELETE FROM jobs WHERE id=?;", params![self.job_id as i32])
                 .is_ok()
+        } else {
+            // Already deleted.
+            true
+        }
     }
 
-    /// Updates the job already stored in the database.
+    /// Saves the job to the database, creating a new entry if necessary.
     ///
-    /// To add a new job, use [job_add].
-    fn update(&self, context: &Context) -> bool {
+    /// The Job is consumed by this method.
+    fn save(self, context: &Context) -> bool {
+        let thread: Thread = self.action.into();
+
+        if self.job_id != 0 {
             sql::execute(
                 context,
                 &context.sql,
@@ -186,6 +209,21 @@ impl Job {
                 ],
             )
             .is_ok()
+        } else {
+            sql::execute(
+                context,
+                &context.sql,
+                "INSERT INTO jobs (added_timestamp, thread, action, foreign_id, param, desired_timestamp) VALUES (?,?,?,?,?,?);",
+                params![
+                    self.added_timestamp,
+                    thread,
+                    self.action,
+                    self.foreign_id,
+                    self.param.to_string(),
+                    self.desired_timestamp
+                ]
+            ).is_ok()
+        }
     }
 
     fn smtp_send<F>(
@@ -1071,7 +1109,6 @@ fn job_perform(context: &Context, thread: Thread, probe_network: bool) {
                     job.tries = tries;
                     let time_offset = get_backoff_time_offset(tries);
                     job.desired_timestamp = time() + time_offset;
-                    job.update(context);
                     info!(
                         context,
                         "{}-job #{} not succeeded on try #{}, retry in {} seconds.",
@@ -1080,6 +1117,7 @@ fn job_perform(context: &Context, thread: Thread, probe_network: bool) {
                         tries,
                         time_offset
                     );
+                    job.save(context);
                     if thread == Thread::Smtp && tries < JOB_RETRIES - 1 {
                         context
                             .smtp_state
@@ -1237,28 +1275,17 @@ pub fn job_add(
         return;
     }
 
-    let timestamp = time();
+    let job = Job::new(action, foreign_id as u32, param, delay_seconds);
+    job.save(context);
+
+    if delay_seconds == 0 {
         let thread: Thread = action.into();
-
-    sql::execute(
-        context,
-        &context.sql,
-        "INSERT INTO jobs (added_timestamp, thread, action, foreign_id, param, desired_timestamp) VALUES (?,?,?,?,?,?);",
-        params![
-            timestamp,
-            thread,
-            action,
-            foreign_id,
-            param.to_string(),
-            (timestamp + delay_seconds as i64)
-        ]
-    ).ok();
-
         match thread {
             Thread::Imap => interrupt_inbox_idle(context),
             Thread::Smtp => interrupt_smtp_idle(context),
             Thread::Unknown => {}
         }
+    }
 }
 
 pub fn interrupt_smtp_idle(context: &Context) {