Synchronize deck only if necessary

Look at the modification time of the deck, and synchronize if it has
been modified after the last deck read.

1 files changed, 38 insertions, 6 deletions

diff --git a/src/db/db.rs b/src/db/db.rs
index 30ea1da..b42da3f 100644
--- a/src/db/db.rs
+++ b/src/db/db.rs
@@ -19,13 +19,23 @@ pub fn init(database: String) -> Result<Connection> {
     Ok(conn)
 }
 
+pub fn last_deck_read(conn: &Connection) -> Option<u64> {
+    let mut stmt = conn
+        .prepare("SELECT deck_read FROM cards ORDER BY deck_read DESC LIMIT 1")
+        .ok()?;
+
+    let mut rows = stmt.query([]).ok()?;
+    let row = rows.next().ok()??;
+    row.get(0).ok()?
+}
+
 /// Synchronize the DB with the deck:
 ///
 /// - insert new cards,
 /// - keep existing cards,
 /// - hide unused cards (keep state in case the card is added back afterward).
 pub fn synchronize(conn: &Connection, entries: Vec<Entry>) -> Result<()> {
-    let now = time::now()?;
+    let now = time::seconds_since_unix_epoch()?;
 
     let state = serde_json::to_string(&space_repetition::init())?;
 
@@ -76,19 +86,21 @@ fn delete_read_before(conn: &Connection, t: u64) -> Result<()> {
 }
 
 pub fn pick_random_ready(conn: &Connection) -> Option<Card> {
+    let now = time::seconds_since_unix_epoch().ok()?;
+
     let mut stmt = conn
         .prepare(
             "
         SELECT question, responses, state, ready
         FROM cards
-        WHERE deleted IS NULL
+        WHERE deleted IS NULL AND ready <= ?
         ORDER BY RANDOM()
         LIMIT 1
         ",
         )
         .ok()?;
 
-    let mut rows = stmt.query([]).ok()?;
+    let mut rows = stmt.query([now]).ok()?;
     let row = rows.next().ok()??;
     let state_str: String = row.get(2).ok()?;
     let responses_str: String = row.get(1).ok()?;
@@ -101,9 +113,29 @@ pub fn pick_random_ready(conn: &Connection) -> Option<Card> {
     })
 }
 
+pub fn next_ready(conn: &Connection) -> Option<u64> {
+    let mut stmt = conn
+        .prepare(
+            "
+        SELECT ready 
+        FROM cards 
+        WHERE deleted IS NULL
+        ORDER BY ready
+        LIMIT 1
+    ",
+        )
+        .ok()?;
+
+    let mut rows = stmt.query([]).ok()?;
+    let row = rows.next().ok()??;
+    row.get(0).ok()?
+}
+
 pub fn count_available(conn: &Connection) -> Option<i32> {
-    let now = time::now().ok()?;
-    let mut stmt = conn.prepare("SELECT COUNT(*) FROM cards WHERE ready <= ? AND deleted IS NULL").ok()?;
+    let now = time::seconds_since_unix_epoch().ok()?;
+    let mut stmt = conn
+        .prepare("SELECT COUNT(*) FROM cards WHERE ready <= ? AND deleted IS NULL")
+        .ok()?;
 
     let mut rows = stmt.query([now]).ok()?;
     let row = rows.next().ok()??;
@@ -111,7 +143,7 @@ pub fn count_available(conn: &Connection) -> Option<i32> {
 }
 
 pub fn update(conn: &Connection, question: &String, state: &space_repetition::State) -> Result<()> {
-    let now = time::now()?;
+    let now = time::seconds_since_unix_epoch()?;
     let ready = now + state.get_interval_seconds();
     let state_str = serde_json::to_string(state)?;