//! Caching layer for downloaded remote sensing imagery files.
//!
//! Provides TTL-based file caching with symlink integration. Files are stored
//! in a cache directory keyed by SHA-256 hash of their source URL, and symlinked
//! to the output location.
//!
//! # Cache Layout
//!
//! ```text
//! ~/.rss_cache/                      (or $RSS_CACHE_DIR)
//!   ab                               (first 2 chars of hash, fan-out)
//!     cd1234...                      (full hash as filename)
//!     cd1234...meta                  (sidecar JSON: url, cached_at, size)
//! ```
//!
//! # Environment Variables
//!
//! - `RSS_CACHE_DIR` — Cache root directory (default: `~/.rss_cache`)
//! - `RSS_CACHE_TTL` — Time-to-live in seconds (default: 604800 = 7 days)

pub mod file_cache;

pub use file_cache::FileCache;
