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.
---
 Cargo.lock     | 47 -----------------------------------------------
 Cargo.toml     |  1 -
 src/db/db.rs   | 17 +++++------------
 src/gui/gui.rs |  2 +-
 4 files changed, 6 insertions(+), 61 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 55d77f0..d7bf371 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -109,7 +109,6 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "chrono",
- "rand",
  "rusqlite",
  "rusqlite_migration",
  "serde",
@@ -246,12 +245,6 @@ version = "0.3.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "12295df4f294471248581bc09bef3c38a5e46f1e36d6a37353621a0c6c357e1f"
 
-[[package]]
-name = "ppv-lite86"
-version = "0.2.15"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed0cfbc8191465bed66e1718596ee0b0b35d5ee1f41c5df2189d0fe8bde535ba"
-
 [[package]]
 name = "proc-macro-error"
 version = "1.0.4"
@@ -294,46 +287,6 @@ dependencies = [
  "proc-macro2",
 ]
 
-[[package]]
-name = "rand"
-version = "0.8.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e7573632e6454cf6b99d7aac4ccca54be06da05aca2ef7423d22d27d4d4bcd8"
-dependencies = [
- "libc",
- "rand_chacha",
- "rand_core",
- "rand_hc",
-]
-
-[[package]]
-name = "rand_chacha"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
-dependencies = [
- "ppv-lite86",
- "rand_core",
-]
-
-[[package]]
-name = "rand_core"
-version = "0.6.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d34f1408f55294453790c48b2f1ebbb1c5b4b7563eb1f418bcfcfdbb06ebb4e7"
-dependencies = [
- "getrandom",
-]
-
-[[package]]
-name = "rand_hc"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d51e9f596de227fda2ea6c84607f5558e196eeaf43c986b724ba4fb8fdf497e7"
-dependencies = [
- "rand_core",
-]
-
 [[package]]
 name = "redox_syscall"
 version = "0.2.10"
diff --git a/Cargo.toml b/Cargo.toml
index 95f0f5c..ce79a66 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2018"
 [dependencies]
 anyhow = "1.0"
 chrono = "0.4"
-rand = "0.8"
 rusqlite = { version = "0.26", features = [ "chrono" ] }
 rusqlite_migration = "0.5"
 serde = { version = "1.0", features = ["derive"] }
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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