feat(cache): add file cache, cache commands, and offline fallback

src/cache.rs

@@ -1 +1,197 @@
-// Cache module placeholder for MVP foundation.
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::time::Duration;
+
+use chrono::{DateTime, Utc};
+use directories::ProjectDirs;
+use serde::de::DeserializeOwned;
+use serde::{Deserialize, Serialize};
+
+use crate::error::IdxError;
+
+const SCHEMA_VERSION: u32 = 1;
+
+#[derive(Debug, Clone)]
+pub struct Cache {
+    root: PathBuf,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+struct CacheEntry<T> {
+    fetched_at: DateTime<Utc>,
+    ttl_secs: u64,
+    schema_version: u32,
+    data: T,
+}
+
+#[derive(Debug)]
+pub struct CacheInfo {
+    pub path: PathBuf,
+    pub files: usize,
+    pub total_size: u64,
+    pub oldest: Option<DateTime<Utc>>,
+    pub newest: Option<DateTime<Utc>>,
+}
+
+impl Cache {
+    pub fn new() -> Result<Self, IdxError> {
+        Ok(Self { root: cache_dir()? })
+    }
+
+    #[cfg(test)]
+    pub fn with_root(root: PathBuf) -> Self {
+        Self { root }
+    }
+
+
+    pub fn get<T: DeserializeOwned>(&self, data_type: &str, symbol: &str) -> Result<Option<T>, IdxError> {
+        let Some(entry): Option<CacheEntry<T>> = self.read_entry(data_type, symbol)? else {
+            return Ok(None);
+        };
+        let age = Utc::now().signed_duration_since(entry.fetched_at);
+        if age > chrono::Duration::from_std(Duration::from_secs(entry.ttl_secs)).map_err(|e| IdxError::CacheMiss(e.to_string()))? {
+            return Ok(None);
+        }
+        Ok(Some(entry.data))
+    }
+
+    pub fn get_stale<T: DeserializeOwned>(&self, data_type: &str, symbol: &str) -> Result<Option<T>, IdxError> {
+        Ok(self.read_entry::<T>(data_type, symbol)?.map(|e| e.data))
+    }
+
+    pub fn put<T: Serialize>(&self, data_type: &str, symbol: &str, data: &T, ttl_secs: u64) -> Result<(), IdxError> {
+        let path = self.entry_path(data_type, symbol);
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent).map_err(|e| IdxError::Io(e.to_string()))?;
+        }
+        let entry = CacheEntry {
+            fetched_at: Utc::now(),
+            ttl_secs,
+            schema_version: SCHEMA_VERSION,
+            data,
+        };
+        let raw = serde_json::to_string_pretty(&entry).map_err(|e| IdxError::ParseError(e.to_string()))?;
+        fs::write(path, raw).map_err(|e| IdxError::Io(e.to_string()))
+    }
+
+    pub fn info(&self) -> Result<CacheInfo, IdxError> {
+        let mut files = 0usize;
+        let mut total_size = 0u64;
+        let mut oldest: Option<DateTime<Utc>> = None;
+        let mut newest: Option<DateTime<Utc>> = None;
+
+        if self.root.exists() {
+            self.walk(&self.root, &mut |p| {
+                if let Ok(meta) = fs::metadata(p)
+                    && meta.is_file()
+                {
+                    files += 1;
+                    total_size += meta.len();
+                    if let Ok(raw) = fs::read_to_string(p)
+                        && let Ok(entry) = serde_json::from_str::<CacheEntry<serde_json::Value>>(&raw)
+                    {
+                        oldest = Some(oldest.map_or(entry.fetched_at, |o| o.min(entry.fetched_at)));
+                        newest = Some(newest.map_or(entry.fetched_at, |n| n.max(entry.fetched_at)));
+                    }
+                }
+            })?;
+        }
+
+        Ok(CacheInfo {
+            path: self.root.clone(),
+            files,
+            total_size,
+            oldest,
+            newest,
+        })
+    }
+
+    pub fn clear(&self) -> Result<usize, IdxError> {
+        if !self.root.exists() {
+            return Ok(0);
+        }
+        let mut removed = 0usize;
+        self.walk(&self.root, &mut |p| {
+            if p.is_file() && fs::remove_file(p).is_ok() {
+                removed += 1;
+            }
+        })?;
+        Ok(removed)
+    }
+
+    fn walk<F: FnMut(&Path)>(&self, dir: &Path, f: &mut F) -> Result<(), IdxError> {
+        for entry in fs::read_dir(dir).map_err(|e| IdxError::Io(e.to_string()))? {
+            let entry = entry.map_err(|e| IdxError::Io(e.to_string()))?;
+            let path = entry.path();
+            if path.is_dir() {
+                self.walk(&path, f)?;
+            } else {
+                f(&path);
+            }
+        }
+        Ok(())
+    }
+
+    fn read_entry<T: DeserializeOwned>(&self, data_type: &str, symbol: &str) -> Result<Option<CacheEntry<T>>, IdxError> {
+        let path = self.entry_path(data_type, symbol);
+        if !path.exists() {
+            return Ok(None);
+        }
+        let raw = fs::read_to_string(path).map_err(|e| IdxError::Io(e.to_string()))?;
+        let entry = serde_json::from_str(&raw).map_err(|e| IdxError::ParseError(e.to_string()))?;
+        Ok(Some(entry))
+    }
+
+    fn entry_path(&self, data_type: &str, symbol: &str) -> PathBuf {
+        self.root.join(data_type).join(format!("{symbol}.json"))
+    }
+}
+
+pub fn cache_dir() -> Result<PathBuf, IdxError> {
+    ProjectDirs::from("", "", "idx")
+        .map(|d| d.cache_dir().to_path_buf())
+        .ok_or_else(|| IdxError::ConfigError("unable to resolve cache dir".to_string()))
+}
+
+#[cfg(test)]
+mod tests {
+    use std::fs;
+
+    use serde::{Deserialize, Serialize};
+
+    use super::{Cache, CacheEntry};
+
+    #[derive(Debug, Serialize, Deserialize, PartialEq)]
+    struct T {
+        v: i32,
+    }
+
+    fn tmp() -> std::path::PathBuf {
+        let p = std::env::temp_dir().join(format!("idx-cache-test-{}", std::process::id()));
+        let _ = fs::remove_dir_all(&p);
+        fs::create_dir_all(&p).expect("create tmp cache dir");
+        p
+    }
+
+    #[test]
+    fn write_read_expire_and_stale() {
+        let root = tmp();
+        let cache = Cache::with_root(root.clone());
+
+        cache.put("quote", "BBCA.JK", &T { v: 7 }, 300).expect("cache write");
+        let fresh: Option<T> = cache.get("quote", "BBCA.JK").expect("cache read fresh");
+        assert_eq!(fresh, Some(T { v: 7 }));
+
+        let path = root.join("quote/BBCA.JK.json");
+        let mut entry: CacheEntry<T> = serde_json::from_str(&fs::read_to_string(&path).expect("read cache file"))
+            .expect("parse cache entry");
+        entry.fetched_at = chrono::Utc::now() - chrono::Duration::seconds(1000);
+        fs::write(&path, serde_json::to_string(&entry).expect("serialize entry")).expect("write old entry");
+
+        let expired: Option<T> = cache.get("quote", "BBCA.JK").expect("cache read expired");
+        assert_eq!(expired, None);
+
+        let stale: Option<T> = cache.get_stale("quote", "BBCA.JK").expect("cache read stale");
+        assert_eq!(stale, Some(T { v: 7 }));
+    }
+}