task-088: cache open file

1 files changed, 83 insertions, 0 deletions

diff --git a/schist_desktop_gui/src/cache.rs b/schist_desktop_gui/src/cache.rs
new file mode 100644
index 0000000..51e2c55
--- /dev/null
+++ b/schist_desktop_gui/src/cache.rs
@@ -0,0 +1,83 @@
+use std::{
+    fs::{create_dir_all, exists, read, write, File},
+    path::{Path, PathBuf},
+};
+
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+
+const SCHIST_CACHE_DIR: &'static str = "schist";
+const SCHIST_CACHE_FILENAME: &'static str = "schist_cache.toml";
+
+#[derive(Default, Deserialize, Serialize)]
+pub struct Cache {
+    pub last_open_file: Option<String>,
+}
+
+pub struct CacheKeys {
+    pub last_open_file: &'static str,
+}
+
+pub const CACHE_KEYS: CacheKeys = CacheKeys {
+    last_open_file: "last_open_file",
+};
+
+pub fn get_cache() -> Result<Cache> {
+    const CONTEXT: &'static str = "Failed to get cache";
+    let cache_filepath = get_and_touch_cache_filepath().context(CONTEXT)?;
+    let cache_toml = read(&cache_filepath).context(CONTEXT)?;
+    let cache_table: toml::Table = toml::from_slice(&cache_toml).context(CONTEXT)?;
+    Ok(Cache {
+        last_open_file: cache_table
+            .get(&CACHE_KEYS.last_open_file.to_string())
+            .map(|o| o.as_str().map(str::to_string))
+            .flatten(),
+    })
+}
+
+pub fn put_to_cache<T>(key: &str, value: T) -> Result<()>
+where
+    toml::Value: From<T>,
+{
+    const CONTEXT: &'static str = "Failed to save cache";
+    let cache_filepath = get_and_touch_cache_filepath().context(CONTEXT)?;
+    let curr_cache_toml = read(&cache_filepath).context(CONTEXT)?;
+    let mut cache: toml::Table = toml::from_slice(&curr_cache_toml).context(CONTEXT)?;
+    cache.insert(key.to_string(), value.into());
+    let new_cache_toml = toml::to_string(&cache).context(CONTEXT)?;
+    write(cache_filepath, new_cache_toml).context(CONTEXT)?;
+    Ok(())
+}
+
+pub fn remove_from_cache(key: &str) -> Result<()> {
+    const CONTEXT: &'static str = "Failed to remove key from cache";
+    let cache_filepath = get_and_touch_cache_filepath().context(CONTEXT)?;
+    let curr_cache_toml = read(&cache_filepath).context(CONTEXT)?;
+    let mut cache: toml::Table = toml::from_slice(&curr_cache_toml).context(CONTEXT)?;
+    cache.remove(key);
+    let new_cache_toml = toml::to_string(&cache).context(CONTEXT)?;
+    write(cache_filepath, new_cache_toml).context(CONTEXT)?;
+    Ok(())
+}
+
+fn get_and_touch_cache_filepath() -> Result<PathBuf, anyhow::Error> {
+    let cache_dir = get_and_make_schist_cache_dir()?;
+    let cache_filepath = cache_dir.join(Path::new(SCHIST_CACHE_FILENAME));
+    let does_cache_file_exist = exists(cache_filepath.clone())
+        .context("Failed to determine the existence of Schist's cache file")?;
+    if !does_cache_file_exist {
+        File::create(cache_filepath.clone()).context("Failed to create a new cache file")?;
+    }
+    Ok(cache_filepath)
+}
+
+fn get_and_make_schist_cache_dir() -> anyhow::Result<PathBuf> {
+    let cache_dir = dirs::cache_dir().context("Failed to get app cache directory")?;
+    let schist_cache_dir = cache_dir.join(Path::new(SCHIST_CACHE_DIR));
+    create_dir_all(&schist_cache_dir).context(format!(
+        "Failed to create app cache directory at {}",
+        schist_cache_dir.display()
+    ))?;
+    println!("Found app cache directory at {:?}", schist_cache_dir);
+    Ok(schist_cache_dir)
+}