Tolerate changes in the state file

1 files changed, 112 insertions, 0 deletions

diff --git a/src/app_state/state_file.rs b/src/app_state/state_file.rs
new file mode 100644
index 0000000..364a1fa
--- /dev/null
+++ b/src/app_state/state_file.rs
@@ -0,0 +1,112 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::fs;
+
+use crate::exercise::Exercise;
+
+use super::{AppState, STATE_FILE_NAME};
+
+#[derive(Deserialize)]
+pub struct ExerciseStateDeser {
+    pub name: String,
+    pub done: bool,
+}
+
+#[derive(Serialize)]
+struct ExerciseStateSer<'a> {
+    name: &'a str,
+    done: bool,
+}
+
+struct ExercisesStateSerializer<'a>(&'a [Exercise]);
+
+impl<'a> Serialize for ExercisesStateSerializer<'a> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let iter = self.0.iter().map(|exercise| ExerciseStateSer {
+            name: exercise.name,
+            done: exercise.done,
+        });
+
+        serializer.collect_seq(iter)
+    }
+}
+
+#[derive(Deserialize)]
+pub struct StateFileDeser {
+    pub current_exercise_ind: usize,
+    pub exercises: Vec<ExerciseStateDeser>,
+}
+
+#[derive(Serialize)]
+struct StateFileSer<'a> {
+    current_exercise_ind: usize,
+    exercises: ExercisesStateSerializer<'a>,
+}
+
+impl StateFileDeser {
+    pub fn read() -> Option<Self> {
+        let file_content = fs::read(STATE_FILE_NAME).ok()?;
+        serde_json::de::from_slice(&file_content).ok()
+    }
+}
+
+pub fn write(app_state: &AppState) -> Result<()> {
+    let content = StateFileSer {
+        current_exercise_ind: app_state.current_exercise_ind,
+        exercises: ExercisesStateSerializer(&app_state.exercises),
+    };
+
+    let mut buf = Vec::with_capacity(1024);
+    serde_json::ser::to_writer(&mut buf, &content).context("Failed to serialize the state")?;
+    fs::write(STATE_FILE_NAME, buf)
+        .with_context(|| format!("Failed to write the state file `{STATE_FILE_NAME}`"))?;
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+
+    use crate::info_file::Mode;
+
+    use super::*;
+
+    #[test]
+    fn ser_deser_sync() {
+        let current_exercise_ind = 1;
+        let exercises = [
+            Exercise {
+                name: "1",
+                path: Path::new("exercises/1.rs"),
+                mode: Mode::Run,
+                hint: String::new(),
+                done: true,
+            },
+            Exercise {
+                name: "2",
+                path: Path::new("exercises/2.rs"),
+                mode: Mode::Test,
+                hint: String::new(),
+                done: false,
+            },
+        ];
+
+        let ser = StateFileSer {
+            current_exercise_ind,
+            exercises: ExercisesStateSerializer(&exercises),
+        };
+        let deser: StateFileDeser =
+            serde_json::de::from_slice(&serde_json::ser::to_vec(&ser).unwrap()).unwrap();
+
+        assert_eq!(deser.current_exercise_ind, current_exercise_ind);
+        assert!(deser
+            .exercises
+            .iter()
+            .zip(exercises)
+            .all(|(deser, ser)| deser.name == ser.name && deser.done == ser.done));
+    }
+}