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use std::env;
use std::io::Write;
use std::path::{Path, PathBuf};
use crate::error::{CacheError, Error};
use crate::parse::parse_binary;
use crate::syntax::{binary, Hash};
use crate::Typed;
use std::ffi::OsStr;
use std::fs::File;
#[cfg(any(unix, windows))]
const CACHE_ENV_VAR: &str = "XDG_CACHE_HOME";
#[cfg(unix)]
const ALTERNATE_CACHE_ENV_VAR: &str = "HOME";
#[cfg(windows)]
const ALTERNATE_CACHE_ENV_VAR: &str = "LOCALAPPDATA";
#[cfg(any(unix, windows))]
fn default_cache_dir() -> Result<PathBuf, CacheError> {
let cache_base_path = match env::var(OsStr::new(CACHE_ENV_VAR)) {
Ok(path) => PathBuf::from(path),
Err(_) => match env::var(OsStr::new(ALTERNATE_CACHE_ENV_VAR)) {
Ok(path) => PathBuf::from(path).join(".cache"),
Err(_) => return Err(CacheError::MissingConfiguration),
},
};
Ok(cache_base_path.join("dhall"))
}
#[cfg(not(any(unix, windows)))]
fn default_cache_dir() -> Result<PathBuf, CacheError> {
Err(CacheError::MissingConfiguration)
}
#[derive(Debug, Clone, PartialEq)]
pub struct Cache {
cache_dir: PathBuf,
}
impl Cache {
pub fn new() -> Result<Cache, Error> {
let cache_dir = default_cache_dir()?;
if !cache_dir.exists() {
std::fs::create_dir_all(&cache_dir)
.map_err(|e| CacheError::InitialisationError { cause: e })?;
}
Ok(Cache { cache_dir })
}
fn entry_path(&self, hash: &Hash) -> PathBuf {
self.cache_dir.join(filename_for_hash(hash))
}
pub fn get(&self, hash: &Hash) -> Result<Typed, Error> {
let path = self.entry_path(hash);
let res = read_cache_file(&path, hash);
if res.is_err() && path.exists() {
// Delete cache file since it's invalid. We ignore the error.
let _ = std::fs::remove_file(&path);
}
res
}
pub fn insert(&self, hash: &Hash, expr: &Typed) -> Result<(), Error> {
let path = self.entry_path(hash);
write_cache_file(&path, expr)
}
}
/// Read a file from the cache, also checking that its hash is valid.
fn read_cache_file(path: &Path, hash: &Hash) -> Result<Typed, Error> {
let data = crate::utils::read_binary_file(path)?;
match hash {
Hash::SHA256(hash) => {
let actual_hash = crate::utils::sha256_hash(&data);
if hash[..] != actual_hash[..] {
return Err(CacheError::CacheHashInvalid.into());
}
}
}
Ok(parse_binary(&data)?.skip_resolve()?.typecheck()?)
}
/// Write a file to the cache.
fn write_cache_file(path: &Path, expr: &Typed) -> Result<(), Error> {
let data = binary::encode(&expr.to_expr())?;
File::create(path)?.write_all(data.as_slice())?;
Ok(())
}
fn filename_for_hash(hash: &Hash) -> String {
match hash {
Hash::SHA256(sha) => format!("1220{}", hex::encode(&sha)),
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::syntax::parse_expr;
#[test]
fn filename_for_hash_should_work() {
let hash =
Hash::SHA256(parse_expr("1").unwrap().sha256_hash().unwrap());
assert_eq!("1220d60d8415e36e86dae7f42933d3b0c4fe3ca238f057fba206c7e9fbf5d784fe15".to_string(), filename_for_hash(&hash));
}
}
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