Add the exercises command

Subcommands have been added to it which are similar to the ones on words
on purpose.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

2 files changed, 179 insertions, 0 deletions

diff --git a/lib/mihi/src/lib.rs b/lib/mihi/src/lib.rs
index 7a5bfc9..7d5cc8c 100644
--- a/lib/mihi/src/lib.rs
+++ b/lib/mihi/src/lib.rs
@@ -533,3 +533,159 @@ fn get_connection() -> Result<rusqlite::Connection, String> {
         ),
     }
 }
+
+#[derive(Clone, Copy, Debug, Default)]
+pub enum ExerciseKind {
+    #[default]
+    Pensum = 0,
+    Translation,
+    Transformation,
+    Numerical,
+}
+
+impl std::fmt::Display for ExerciseKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Self::Pensum => write!(f, "Pensum"),
+            Self::Translation => write!(f, "Translation"),
+            Self::Transformation => write!(f, "Transformation"),
+            Self::Numerical => write!(f, "Numerical"),
+        }
+    }
+}
+
+impl TryFrom<usize> for ExerciseKind {
+    type Error = &'static str;
+
+    fn try_from(value: usize) -> Result<Self, Self::Error> {
+        match value {
+            0 => Ok(Self::Pensum),
+            1 => Ok(Self::Translation),
+            2 => Ok(Self::Transformation),
+            3 => Ok(Self::Numerical),
+            _ => Err("unknonwn kind!"),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct Exercise {
+    pub id: i32,
+    pub title: String,
+    pub enunciate: String,
+    pub solution: String,
+    pub lessons: String,
+    pub kind: ExerciseKind,
+}
+
+/// Creates the given exercise into the database.
+pub fn create_exercise(exercise: Exercise) -> Result<(), String> {
+    let conn = get_connection()?;
+    match conn.execute(
+        "INSERT INTO exercises (title, enunciate, solution, lessons, kind, \
+                                updated_at, created_at) \
+         VALUES (?1, ?2, ?3, ?4, ?5, datetime('now'), datetime('now'))",
+        params![
+            exercise.title,
+            exercise.enunciate,
+            exercise.solution,
+            exercise.lessons,
+            exercise.kind as usize,
+        ],
+    ) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(format!("could not create '{}': {}", exercise.title, e)),
+    }
+}
+
+pub fn select_by_title(filter: Option<String>) -> Result<Vec<String>, String> {
+    let conn = get_connection()?;
+
+    let mut stmt;
+    let mut it = match filter {
+        Some(filter) => {
+            stmt = conn
+                .prepare(
+                    "SELECT title FROM exercises WHERE title LIKE ('%' || ?1 || '%') ORDER BY title",
+                )
+                .unwrap();
+            stmt.query([filter.as_str()]).unwrap()
+        }
+        None => {
+            stmt = conn
+                .prepare("SELECT title FROM exercises ORDER BY title")
+                .unwrap();
+            stmt.query([]).unwrap()
+        }
+    };
+
+    let mut res = vec![];
+    while let Some(row) = it.next().unwrap() {
+        res.push(row.get::<usize, String>(0).unwrap());
+    }
+    Ok(res)
+}
+
+pub fn find_exercise_by_title(title: &str) -> Result<Exercise, String> {
+    let conn = get_connection()?;
+    let mut stmt = conn
+        .prepare(
+            "SELECT id, title, enunciate, solution, lessons, kind  \
+             FROM exercises \
+             WHERE title = ?1",
+        )
+        .unwrap();
+    let mut it = stmt.query([title]).unwrap();
+
+    match it.next() {
+        Err(_) => Err("no exercises were found with this title".to_string()),
+        Ok(rows) => match rows {
+            Some(row) => Ok(Exercise {
+                id: row.get(0).unwrap(),
+                title: row.get(1).unwrap(),
+                enunciate: row.get(2).unwrap(),
+                solution: row.get(3).unwrap(),
+                lessons: row.get(4).unwrap(),
+                kind: row.get::<usize, usize>(5).unwrap().try_into()?,
+            }),
+            None => Err("no exercises were found with this title".to_string()),
+        },
+    }
+}
+
+/// Updates the given exercise.
+pub fn update_exercise(exercise: Exercise) -> Result<(), String> {
+    if exercise.id == 0 {
+        return Err("invalid exercise to update; seems it has not been created before".to_string());
+    }
+
+    let conn = get_connection()?;
+
+    match conn.execute(
+        "UPDATE exercises \
+         SET title = ?2, enunciate = ?3, solution = ?4, lessons = ?5, kind = ?6, \
+             updated_at = datetime('now') \
+         WHERE id = ?1",
+        params![
+            exercise.id,
+            exercise.title,
+            exercise.enunciate,
+            exercise.solution,
+            exercise.lessons,
+            exercise.kind as usize,
+        ],
+    ) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(format!("could not update '{}': {}", exercise.title, e)),
+    }
+}
+
+/// Delete an exercise from the database.
+pub fn delete_exercise(title: &str) -> Result<(), String> {
+    let conn = get_connection()?;
+
+    match conn.execute("DELETE FROM exercises WHERE title = ?1", params![title]) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(format!("could not remove '{title}': {e}")),
+    }
+}
diff --git a/lib/mihi/src/migrate.rs b/lib/mihi/src/migrate.rs
index 9b1e831..97f32c9 100644
--- a/lib/mihi/src/migrate.rs
+++ b/lib/mihi/src/migrate.rs
@@ -42,5 +42,28 @@ CREATE UNIQUE INDEX IF NOT EXISTS "index_words_on_enunciated" ON "words" ("enunc
         (),
     )?;
 
+    connection.execute(
+        r#"
+CREATE TABLE IF NOT EXISTS "exercises" (
+       "id" integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+       "title" varchar NOT NULL,
+       "enunciate" text NOT NULL,
+       "solution" text NOT NULL,
+       "lessons" text NOT NULL,
+       "kind" integer DEFAULT 0,
+       "created_at" datetime(6) NOT NULL,
+       "updated_at" datetime(6) NOT NULL
+);
+"#,
+        (),
+    )?;
+
+    connection.execute(
+        r#"
+CREATE UNIQUE INDEX IF NOT EXISTS "index_exercises_on_title" ON "exercises" ("title");
+"#,
+        (),
+    )?;
+
     Ok(0)
 }