//!

//! This crate is part of

//! [Arti](https://gitlab.torproject.org/tpo/core/arti/), a project to

//! implement [Tor](https://www.torproject.org/) in Rust.

//!

//! For now, users should construct storage objects directly with (for

//! example) [`FsStateMgr::from_path()`], but use them primarily via the

//! interfaces of the [`StateMgr`] trait.

#![deny(missing_docs)]

#![warn(noop_method_call)]

#![deny(unreachable_pub)]

#![warn(clippy::all)]

#![deny(clippy::await_holding_lock)]

#![deny(clippy::cargo_common_metadata)]

#![deny(clippy::cast_lossless)]

#![deny(clippy::checked_conversions)]

#![warn(clippy::cognitive_complexity)]

#![deny(clippy::debug_assert_with_mut_call)]

#![deny(clippy::exhaustive_enums)]

#![deny(clippy::exhaustive_structs)]

#![deny(clippy::expl_impl_clone_on_copy)]

#![deny(clippy::fallible_impl_from)]

#![deny(clippy::implicit_clone)]

#![deny(clippy::large_stack_arrays)]

#![warn(clippy::manual_ok_or)]

#![deny(clippy::missing_docs_in_private_items)]

#![deny(clippy::missing_panics_doc)]

#![warn(clippy::needless_borrow)]

#![warn(clippy::needless_pass_by_value)]

#![warn(clippy::option_option)]

#![warn(clippy::rc_buffer)]

#![deny(clippy::ref_option_ref)]

#![warn(clippy::semicolon_if_nothing_returned)]

#![warn(clippy::trait_duplication_in_bounds)]

#![deny(clippy::unnecessary_wraps)]

#![warn(clippy::unseparated_literal_suffix)]

#![deny(clippy::unwrap_used)]

#[cfg(not(target_arch = "wasm32"))]

mod fs;

mod handle;

#[cfg(feature = "testing")]

mod testing;

use serde::{de::DeserializeOwned, Deserialize, Serialize};

use std::sync::Arc;

/// Wrapper type for Results returned from this crate.

type Result<T> = std::result::Result<T, crate::Error>;

#[cfg(not(target_arch = "wasm32"))]

pub use fs::FsStateMgr;

pub use handle::{DynStorageHandle, StorageHandle};

pub use serde_json::Value as JsonValue;

#[cfg(feature = "testing")]

pub use testing::TestingStateMgr;

use tor_error::ErrorKind;

/// An object that can manage persistent state.

///

/// State is implemented as a simple key-value store, where the values

/// are objects that can be serialized and deserialized.

///

/// # Warnings

///

/// Current implementations may place additional limits on the types

/// of objects that can be stored.  This is not a great example of OO

/// design: eventually we should probably clarify that more.

pub trait StateMgr: Clone {

    /// Try to load the object with key `key` from the store.

    ///

    /// Return None if no such object exists.

    fn load<D>(&self, key: &str) -> Result<Option<D>>

    where

        D: DeserializeOwned;

    /// Try to save `val` with key `key` in the store.

    ///

    /// Replaces any previous value associated with `key`.

    fn store<S>(&self, key: &str, val: &S) -> Result<()>

    where

        S: Serialize;

    /// Return true if this is a read-write state manager.

    ///

    /// If it returns false, then attempts to `store` will fail with

    /// [`Error::NoLock`]

    fn can_store(&self) -> bool;

    /// Try to become a read-write state manager if possible, without

    /// blocking.

    ///

    /// This function will return an error only if something really

    /// unexpected went wrong.  It may return `Ok(_)` even if we don't

    /// acquire the lock: check the return value or call

    /// `[StateMgr::can_store()`] to see if the lock is held.

    fn try_lock(&self) -> Result<LockStatus>;

    /// Release any locks held and become a read-only state manager

    /// again. If no locks were held, do nothing.

    fn unlock(&self) -> Result<()>;

    /// Make a new [`StorageHandle`] to store values of particular type

    /// at a particular key.

    fn create_handle<T>(self, key: impl Into<String>) -> DynStorageHandle<T>

    where

        Self: Send + Sync + Sized + 'static,

        T: Serialize + DeserializeOwned + 'static,

    {

        Arc::new(handle::StorageHandleImpl::new(self, key.into()))

    }

}

/// A possible outcome from calling [`StateMgr::try_lock()`]

#[allow(clippy::exhaustive_enums)]

pub enum LockStatus {

    /// We didn't have the lock and were unable to acquire it.

    NoLock,

    /// We already held the lock, and didn't have anything to do.

    AlreadyHeld,

    /// We successfully acquired the lock for the first time.

    NewlyAcquired,

}

impl LockStatus {

    /// Return true if this status indicates that we hold the lock.

}

/// An error manipulating persistent state.

//

// Such errors are "global" in the sense that it doesn't relate to any guard or any circuit

// or anything, so callers may use `#[from]` when they include it in their own error.

#[non_exhaustive]

pub enum Error {

    /// An IO error occurred.

    #[error("IO error")]

    IoError(#[source] Arc<std::io::Error>),

    /// Tried to save without holding an exclusive lock.

    //

    // TODO This error seems to actually be sometimes used to make store a no-op.

    //      We should consider whether this is best handled as an error, but for now

    //      this seems adequate.

    #[error("Storage not locked")]

    NoLock,

    /// Problem when serializing JSON data.

    #[error("JSON serialization error")]

    Serialize(#[source] Arc<serde_json::Error>),

    /// Problem when deserializing JSON data.

    #[error("JSON serialization error")]

    Deserialize(#[source] Arc<serde_json::Error>),

}

impl tor_error::HasKind for Error {

    #[rustfmt::skip] // the tabular layout of the `match` makes this a lot clearer

        }

}

impl From<std::io::Error> for Error {

}

/// Error conversion for JSON errors; use only when loading

/// Error conversion for JSON errors; use only when storing

/// A wrapper type for types whose representation may change in future versions of Arti.

///

/// This uses `#[serde(untagged)]` to attempt deserializing as a type `T` first, and falls back

/// to a generic JSON value representation if that fails.

#[serde(untagged)]

#[allow(clippy::exhaustive_enums)]

pub enum Futureproof<T> {

    /// A successfully-deserialized `T`.

    Understandable(T),

    /// A generic JSON value, representing a failure to deserialize a `T`.

    Unknown(JsonValue),

}

impl<T> Futureproof<T> {

    /// Convert the `Futureproof` into an `Option<T>`, throwing away an `Unknown` value.

        }

}

impl<T> From<T> for Futureproof<T> {

}