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//! **A undo-redo library.**
//!
//! It is an implementation of the action pattern, where all modifications are done
//! by creating objects of actions that applies the modifications. All actions knows
//! how to undo the changes it applies, and by using the provided data structures
//! it is easy to apply, undo, and redo changes made to a target.
//!
//! # Features
//!
//! * [Action](trait.Action.html) provides the base functionality for all actions.
//! * [Record](record/struct.Record.html) provides basic undo-redo functionality.
//! * [Timeline](timeline/struct.Timeline.html) provides basic undo-redo functionality using a fixed size.
//! * [History](history/struct.History.html) provides non-linear undo-redo functionality that allows you to jump between different branches.
//! * Queues wraps a record or history and extends them with queue functionality.
//! * Checkpoints wraps a record or history and extends them with checkpoint functionality.
//! * Actions can be merged into a single action by implementing the
//! [merge](trait.Action.html#method.merge) method on the action.
//! This allows smaller actions to be used to build more complex operations, or smaller incremental changes to be
//! merged into larger changes that can be undone and redone in a single step.
//! * The target can be marked as being saved to disk and the data-structures can track the saved state and notify
//! when it changes.
//! * The amount of changes being tracked can be configured by the user so only the `N` most recent changes are stored.
//! * Configurable display formatting using the display structure.
//! * The library can be used as `no_std`.
//!
//! # Cargo Feature Flags
//!
//! * `alloc`: Enables the use of the alloc crate, enabled by default.
//! * `arrayvec`: Required for the timeline module, enabled by default.
//! * `chrono`: Enables time stamps and time travel.
//! * `serde`: Enables serialization and deserialization.
//! * `colored`: Enables colored output when visualizing the display structures.
//!
//! # Examples
//!
//! ```rust
//! use undo::{Action, History};
//!
//! struct Add(char);
//!
//! impl Action for Add {
//! type Target = String;
//! type Output = ();
//! type Error = &'static str;
//!
//! fn apply(&mut self, s: &mut String) -> undo::Result<Add> {
//! s.push(self.0);
//! Ok(())
//! }
//!
//! fn undo(&mut self, s: &mut String) -> undo::Result<Add> {
//! self.0 = s.pop().ok_or("s is empty")?;
//! Ok(())
//! }
//! }
//!
//! fn main() {
//! let mut target = String::new();
//! let mut history = History::new();
//! history.apply(&mut target, Add('a')).unwrap();
//! history.apply(&mut target, Add('b')).unwrap();
//! history.apply(&mut target, Add('c')).unwrap();
//! assert_eq!(target, "abc");
//! history.undo(&mut target).unwrap().unwrap();
//! history.undo(&mut target).unwrap().unwrap();
//! history.undo(&mut target).unwrap().unwrap();
//! assert_eq!(target, "");
//! history.redo(&mut target).unwrap().unwrap();
//! history.redo(&mut target).unwrap().unwrap();
//! history.redo(&mut target).unwrap().unwrap();
//! assert_eq!(target, "abc");
//! }
//! ```
#![no_std]
#![doc(html_root_url = "https://docs.rs/undo")]
#![deny(missing_docs)]
#![forbid(unsafe_code)]
#![cfg_attr(not(feature = "alloc"), allow(dead_code))]
#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(feature = "alloc")]
mod format;
#[cfg(feature = "alloc")]
pub mod history;
#[cfg(feature = "alloc")]
pub mod record;
#[cfg(feature = "arrayvec")]
pub mod timeline;
use crate::format::Format;
#[cfg(feature = "chrono")]
use chrono::{DateTime, Utc};
use core::fmt;
#[cfg(feature = "serde")]
use serde_crate::{Deserialize, Serialize};
#[cfg(feature = "arrayvec")]
pub use self::timeline::Timeline;
#[cfg(feature = "alloc")]
pub use self::{history::History, record::Record};
/// A specialized Result type for undo-redo operations.
pub type Result<A> = core::result::Result<<A as Action>::Output, <A as Action>::Error>;
/// Base functionality for all actions.
pub trait Action {
/// The target type.
type Target;
/// The output type.
type Output;
/// The error type.
type Error;
/// Applies the action on the target and returns `Ok` if everything went fine,
/// and `Err` if something went wrong.
fn apply(&mut self, target: &mut Self::Target) -> Result<Self>;
/// Restores the state of the target as it was before the action was applied
/// and returns `Ok` if everything went fine, and `Err` if something went wrong.
fn undo(&mut self, target: &mut Self::Target) -> Result<Self>;
/// Reapplies the action on the target and return `Ok` if everything went fine,
/// and `Err` if something went wrong.
///
/// The default implementation uses the [`apply`](trait.Action.html#tymethod.apply) implementation.
fn redo(&mut self, target: &mut Self::Target) -> Result<Self> {
self.apply(target)
}
/// Used for manual merging of actions.
fn merge(&mut self, _: &mut Self) -> Merged
where
Self: Sized,
{
Merged::No
}
}
/// Says if the action have been merged with another action.
#[cfg_attr(
feature = "serde",
derive(Serialize, Deserialize),
serde(crate = "serde_crate")
)]
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
pub enum Merged {
/// The actions have been merged.
Yes,
/// The actions have not been merged.
No,
/// The two actions cancels each other out.
Annul,
}
/// A position in a history tree.
#[cfg_attr(
feature = "serde",
derive(Serialize, Deserialize),
serde(crate = "serde_crate")
)]
#[derive(Copy, Clone, Debug, Default, Hash, Eq, PartialEq)]
struct At {
branch: usize,
current: usize,
}
impl At {
const ROOT: At = At::new(0, 0);
const fn new(branch: usize, current: usize) -> At {
At { branch, current }
}
}
/// The signal used for communicating state changes.
///
/// For example, if the record can no longer redo any actions, it sends a `Redo(false)`
/// signal to tell the user.
#[cfg_attr(
feature = "serde",
derive(Serialize, Deserialize),
serde(crate = "serde_crate")
)]
#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
pub enum Signal {
/// Says if the structures can undo.
Undo(bool),
/// Says if the structures can redo.
Redo(bool),
/// Says if the target is in a saved state.
Saved(bool),
}
#[cfg_attr(
feature = "serde",
derive(Serialize, Deserialize),
serde(crate = "serde_crate")
)]
#[derive(Clone)]
struct Slot<F> {
#[cfg_attr(feature = "serde", serde(default = "Option::default", skip))]
f: Option<F>,
}
impl<F: FnMut(Signal)> Slot<F> {
fn emit(&mut self, signal: Signal) {
if let Some(ref mut f) = self.f {
f(signal);
}
}
fn emit_if(&mut self, cond: bool, signal: Signal) {
if cond {
self.emit(signal);
}
}
}
impl<F> From<F> for Slot<F> {
fn from(f: F) -> Slot<F> {
Slot { f: Some(f) }
}
}
impl<F> Default for Slot<F> {
fn default() -> Self {
Slot { f: None }
}
}
impl<F> fmt::Debug for Slot<F> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.f {
Some(_) => f.pad("Slot { .. }"),
None => f.pad("Empty"),
}
}
}
#[cfg_attr(
feature = "serde",
derive(Serialize, Deserialize),
serde(crate = "serde_crate")
)]
#[derive(Clone, Debug, Hash, Eq, PartialEq)]
struct Entry<A> {
action: A,
#[cfg(feature = "chrono")]
timestamp: DateTime<Utc>,
}
impl<A> From<A> for Entry<A> {
fn from(action: A) -> Self {
Entry {
action,
#[cfg(feature = "chrono")]
timestamp: Utc::now(),
}
}
}
impl<A: Action> Action for Entry<A> {
type Target = A::Target;
type Output = A::Output;
type Error = A::Error;
fn apply(&mut self, target: &mut Self::Target) -> Result<Self> {
self.action.apply(target)
}
fn undo(&mut self, target: &mut Self::Target) -> Result<Self> {
self.action.undo(target)
}
fn redo(&mut self, target: &mut Self::Target) -> Result<Self> {
self.action.redo(target)
}
fn merge(&mut self, entry: &mut Self) -> Merged {
self.action.merge(&mut entry.action)
}
}
impl<A: fmt::Display> fmt::Display for Entry<A> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
(&self.action as &dyn fmt::Display).fmt(f)
}
}