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use std::env;
use std::io::Write;
use std::path::{Path, PathBuf};
use crate::error::{CacheError, Error, ErrorKind};
use crate::parse::parse_binary_file;
use crate::semantics::{Import, TypedHir};
use crate::syntax::Hash;
use crate::syntax::{binary, Expr};
use crate::Parsed;
use std::fs::File;
#[cfg(unix)]
const ALTERNATE_ENV_VAR: &str = "HOME";
#[cfg(windows)]
const ALTERNATE_ENV_VAR: &str = "LOCALAPPDATA";
fn alternate_env_var_cache_dir() -> Option<PathBuf> {
env::var(ALTERNATE_ENV_VAR)
.map(PathBuf::from)
.map(|env_dir| env_dir.join(".cache").join("dhall"))
.ok()
}
fn env_var_cache_dir() -> Option<PathBuf> {
env::var("XDG_CACHE_HOME")
.map(PathBuf::from)
.map(|cache_home| cache_home.join("dhall"))
.ok()
}
fn load_cache_dir() -> Result<PathBuf, CacheError> {
env_var_cache_dir()
.or_else(alternate_env_var_cache_dir)
.ok_or(CacheError::MissingConfiguration)
}
pub struct Cache {
cache_dir: Option<PathBuf>,
}
impl Cache {
pub fn new() -> Cache {
// Should warn that we can't initialize cache on error
let cache_dir = load_cache_dir().and_then(|path| {
std::fs::create_dir_all(path.as_path())
.map(|_| path)
.map_err(|e| CacheError::InitialisationError { cause: e })
});
Cache {
cache_dir: cache_dir.ok(),
}
}
}
impl Cache {
fn cache_file(&self, import: &Import) -> Option<PathBuf> {
self.cache_dir
.as_ref()
.and_then(|cache_dir| {
import.hash.as_ref().map(|hash| (cache_dir, hash))
})
.map(|(cache_dir, hash)| cache_dir.join(cache_filename(hash)))
}
fn search_cache_file(&self, import: &Import) -> Option<PathBuf> {
self.cache_file(import)
.filter(|cache_file| cache_file.exists())
}
fn search_cache(&self, import: &Import) -> Option<Result<Parsed, Error>> {
self.search_cache_file(import)
.map(|cache_file| parse_binary_file(cache_file.as_path()))
}
// Side effect since we don't use the result
fn delete_cache(&self, import: &Import) {
self.search_cache_file(import)
.map(|cache_file| std::fs::remove_file(cache_file.as_path()));
}
// Side effect since we don't use the result
fn save_expr(&self, import: &Import, expr: &Expr) {
self.cache_file(import)
.map(|cache_file| save_expr(cache_file.as_path(), expr));
}
pub fn caching_import<F, R>(
&self,
import: &Import,
fetcher: F,
mut resolver: R,
) -> Result<TypedHir, Error>
where
F: FnOnce() -> Result<Parsed, Error>,
R: FnMut(Parsed) -> Result<TypedHir, Error>,
{
// Lookup the cache
self.search_cache(import)
// On cache found
.and_then(|cache_result| {
// Try to resolve the cache imported content
match cache_result.and_then(|parsed| resolver(parsed)).and_then(
|typed_hir| {
check_hash(import.hash.as_ref().unwrap(), typed_hir)
},
) {
// Cache content is invalid (can't be parsed / can't be resolved / content sha invalid )
Err(_) => {
// Delete cache file since it's invalid
self.delete_cache(import);
// Result as there were no cache
None
}
// Cache valid
r => Some(r),
}
})
.unwrap_or_else(|| {
// Fetch and resolve as provided
let imported = fetcher().and_then(resolver);
// Save in cache the result if ok
let _ = imported.as_ref().map(|(hir, _)| {
self.save_expr(import, &hir.to_expr_noopts())
});
imported
})
}
}
fn save_expr(file_path: &Path, expr: &Expr) -> Result<(), Error> {
File::create(file_path)?.write_all(binary::encode(expr)?.as_slice())?;
Ok(())
}
fn check_hash(hash: &Hash, typed_hir: TypedHir) -> Result<TypedHir, Error> {
if hash.as_ref()[..] != typed_hir.0.to_expr_alpha().hash()?[..] {
Err(Error::new(ErrorKind::Cache(CacheError::CacheHashInvalid)))
} else {
Ok(typed_hir)
}
}
fn cache_filename<A: AsRef<[u8]>>(v: A) -> String {
format!("1220{}", hex::encode(v.as_ref()))
}
impl AsRef<[u8]> for Hash {
fn as_ref(&self) -> &[u8] {
match self {
Hash::SHA256(sha) => sha.as_slice(),
}
}
}
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