Added Cache

src/cache.rs

@@ -1 +1,118 @@
 //! This module provides a local cache for CalDAV data
+
+use std::path::PathBuf;
+use std::path::Path;
+use std::error::Error;
+
+use serde::{Deserialize, Serialize};
+use async_trait::async_trait;
+
+use crate::traits::CalDavSource;
+use crate::Calendar;
+
+
+#[derive(Debug, PartialEq)]
+pub struct Cache {
+    backing_file: PathBuf,
+    data: CachedData,
+}
+
+#[derive(Default, Debug, PartialEq, Serialize, Deserialize)]
+struct CachedData {
+    calendars: Vec<Calendar>,
+}
+
+impl Cache {
+    /// Get the cache file
+    pub fn cache_file() -> PathBuf {
+        return PathBuf::from(String::from("~/.config/my-tasks/cache.json"))
+    }
+
+    /// Initialize a cache from the content of a backing file (if it exists, otherwise start with the default contents)
+    pub fn from_file(path: &Path) -> Result<Self, Box<dyn Error>> {
+        let data = match std::fs::File::open(path) {
+            Err(_) => {
+                CachedData::default()
+            },
+            Ok(file) => serde_json::from_reader(file)?,
+        };
+
+        Ok(Self{
+            backing_file: PathBuf::from(path),
+            data,
+        })
+    }
+
+    /// Initialize a cache with the default contents
+    pub fn new(path: &Path) -> Self {
+        Self{
+            backing_file: PathBuf::from(path),
+            data: CachedData::default(),
+        }
+    }
+
+    /// Store the current Cache to its backing file
+    fn save_to_file(&mut self) {
+        // Save the contents to the file
+        let path = &self.backing_file;
+        let file = match std::fs::File::create(path) {
+            Err(err) => {
+                log::warn!("Unable to save file {:?}: {}", path, err);
+                return;
+            },
+            Ok(f) => f,
+        };
+
+        if let Err(err) = serde_json::to_writer(file, &self.data) {
+            log::warn!("Unable to serialize: {}", err);
+            return;
+        };
+    }
+}
+
+impl Cache {
+    pub fn add_calendar(&mut self, calendar: Calendar) {
+        self.data.calendars.push(calendar);
+    }
+}
+
+#[async_trait]
+impl CalDavSource for Cache {
+    async fn get_calendars(&self) -> Result<&Vec<Calendar>, Box<dyn Error>> {
+        Ok(&self.data.calendars)
+    }
+
+    async fn get_calendars_mut(&mut self) -> Result<Vec<&mut Calendar>, Box<dyn Error>> {
+        Ok(
+            self.data.calendars.iter_mut()
+            .collect()
+        )
+    }
+}
+
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use url::Url;
+    use crate::calendar::SupportedComponents;
+
+    #[test]
+    fn serde_cache() {
+        let cache_path = PathBuf::from(String::from("cache.json"));
+
+        let mut cache = Cache::new(&cache_path);
+
+        let cal1 = Calendar::new("shopping list".to_string(),
+                                Url::parse("https://caldav.com/shopping").unwrap(),
+                            SupportedComponents::TODO);
+        cache.add_calendar(cal1);
+
+        cache.save_to_file();
+
+        let retrieved_cache = Cache::from_file(&cache_path).unwrap();
+        assert_eq!(cache, retrieved_cache);
+    }
+}