From 8170fb5e432cc81986479a6a3a400e009426d76a Mon Sep 17 00:00:00 2001
From: Joris
Date: Sun, 13 Feb 2022 09:30:42 +0100
Subject: Properly shuffle card presentation from card insertion

Instead of messing with deck_read, subtracting a random amount of
seconds to it, pick a random card instead of the first ready.

This permits to remove the dependency to the rand crate.
---
 src/db/db.rs   | 17 +++++------------
 src/gui/gui.rs |  2 +-
 2 files changed, 6 insertions(+), 13 deletions(-)

(limited to 'src')

diff --git a/src/db/db.rs b/src/db/db.rs
index 590f3ea..30ea1da 100644
--- a/src/db/db.rs
+++ b/src/db/db.rs
@@ -4,7 +4,6 @@ use crate::{
     util::serialization,
 };
 use anyhow::Result;
-use rand::{rngs::ThreadRng, Rng};
 use rusqlite::{params, Connection};
 use rusqlite_migration::{Migrations, M};
 
@@ -29,18 +28,17 @@ pub fn synchronize(conn: &Connection, entries: Vec<Entry>) -> Result<()> {
     let now = time::now()?;
 
     let state = serde_json::to_string(&space_repetition::init())?;
-    let mut rng = rand::thread_rng();
 
     for entry in entries {
         let concat_1 = serialization::words_to_line(&entry.part_1);
         let concat_2 = serialization::words_to_line(&entry.part_2);
 
         for w in entry.part_1.iter() {
-            insert(&conn, &mut rng, now, &w, &concat_2, &state)?;
+            insert(&conn, now, &w, &concat_2, &state)?;
         }
 
         for w in entry.part_2.iter() {
-            insert(&conn, &mut rng, now, &w, &concat_1, &state)?;
+            insert(&conn, now, &w, &concat_1, &state)?;
         }
     }
 
@@ -51,23 +49,18 @@ pub fn synchronize(conn: &Connection, entries: Vec<Entry>) -> Result<()> {
 
 fn insert(
     conn: &Connection,
-    rng: &mut ThreadRng,
     now: u64,
     question: &String,
     responses: &String,
     state: &String,
 ) -> Result<()> {
-    // Subtract a random amount of time so that cards are not initially given in the same order as
-    // in the deck
-    let ready_sub: u64 = rng.gen_range(0..100);
-
     conn.execute(
         "
         INSERT INTO cards (question, responses, state, created, deck_read, ready)
         VALUES (?, ?, ?, ?, ?, ?)
         ON CONFLICT (question, responses) DO UPDATE SET deck_read = ?, deleted = null
         ",
-        params![question, responses, state, now, now, now - ready_sub, now],
+        params![question, responses, state, now, now, now, now],
     )?;
 
     Ok(())
@@ -82,14 +75,14 @@ fn delete_read_before(conn: &Connection, t: u64) -> Result<()> {
     Ok(())
 }
 
-pub fn next_ready(conn: &Connection) -> Option<Card> {
+pub fn pick_random_ready(conn: &Connection) -> Option<Card> {
     let mut stmt = conn
         .prepare(
             "
         SELECT question, responses, state, ready
         FROM cards
         WHERE deleted IS NULL
-        ORDER BY ready
+        ORDER BY RANDOM()
         LIMIT 1
         ",
         )
diff --git a/src/gui/gui.rs b/src/gui/gui.rs
index 94e15d8..2f41a0b 100644
--- a/src/gui/gui.rs
+++ b/src/gui/gui.rs
@@ -20,7 +20,7 @@ pub fn start(conn: &Connection, deck_name: &String) -> Result<()> {
         let now = time::now()?;
         let title = title(deck_name, answers, db::count_available(&conn).unwrap_or(0));
 
-        match db::next_ready(&conn) {
+        match db::pick_random_ready(&conn) {
             Some(card) if card.ready <= now => {
                 let difficulty = question::ask(&mut terminal, &events, &title, &card)?;
                 answers += 1;
-- 
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