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use crate::prelude::*;
use std::cell::OnceCell;
use std::marker::PhantomData;
use std::ops::Deref;
use crate::Buffer;
/// Utility trait that allows memorizing the output of a [Format].
/// Useful to avoid re-formatting the same object twice.
pub trait MemoizeFormat<Context> {
/// Returns a formattable object that memoizes the result of `Format` by cloning.
/// Mainly useful if the same sub-tree can appear twice in the formatted output because it's
/// used inside of `if_group_breaks` or `if_group_fits_single_line`.
///
/// ```
/// use std::cell::Cell;
/// use biome_formatter::{format, write};
/// use biome_formatter::prelude::*;
/// use biome_rowan::TextSize;
///
/// struct MyFormat {
/// value: Cell<u64>
/// }
///
/// impl MyFormat {
/// pub fn new() -> Self {
/// Self { value: Cell::new(1) }
/// }
/// }
///
/// impl Format<SimpleFormatContext> for MyFormat {
/// fn fmt(&self, f: &mut Formatter<SimpleFormatContext>) -> FormatResult<()> {
/// let value = self.value.get();
/// self.value.set(value + 1);
///
/// write!(f, [dynamic_text(&std::format!("Formatted {value} times."), TextSize::from(0))])
/// }
/// }
///
/// # fn main() -> FormatResult<()> {
/// let normal = MyFormat::new();
///
/// // Calls `format` for everytime the object gets formatted
/// assert_eq!(
/// "Formatted 1 times. Formatted 2 times.",
/// format!(SimpleFormatContext::default(), [normal, space(), normal])?.print()?.as_code()
/// );
///
/// // Memoized memoizes the result and calls `format` only once.
/// let memoized = normal.memoized();
/// assert_eq!(
/// "Formatted 3 times. Formatted 3 times.",
/// format![SimpleFormatContext::default(), [memoized, space(), memoized]]?.print()?.as_code()
/// );
/// # Ok(())
/// # }
/// ```
///
fn memoized(self) -> Memoized<Self, Context>
where
Self: Sized + Format<Context>,
{
Memoized::new(self)
}
}
impl<T, Context> MemoizeFormat<Context> for T where T: Format<Context> {}
/// Memoizes the output of its inner [Format] to avoid re-formatting a potential expensive object.
#[derive(Debug)]
pub struct Memoized<F, Context> {
inner: F,
memory: OnceCell<FormatResult<Option<FormatElement>>>,
options: PhantomData<Context>,
}
impl<F, Context> Memoized<F, Context>
where
F: Format<Context>,
{
fn new(inner: F) -> Self {
Self {
inner,
memory: OnceCell::new(),
options: PhantomData,
}
}
/// Gives access to the memoized content.
///
/// Performs the formatting if the content hasn't been formatted at this point.
///
/// # Example
///
/// Inspect if some memoized content breaks.
///
/// ```rust
/// use std::cell::Cell;
/// use biome_formatter::{format, write};
/// use biome_formatter::prelude::*;
/// use biome_rowan::TextSize;
///
/// #[derive(Default)]
/// struct Counter {
/// value: Cell<u64>
/// }
///
/// impl Format<SimpleFormatContext> for Counter {
/// fn fmt(&self, f: &mut Formatter<SimpleFormatContext>) -> FormatResult<()> {
/// let current = self.value.get();
///
/// write!(f, [
/// text("Count:"),
/// space(),
/// dynamic_text(&std::format!("{current}"), TextSize::default()),
/// hard_line_break()
/// ])?;
///
/// self.value.set(current + 1);
/// Ok(())
/// }
/// }
///
/// # fn main() -> FormatResult<()> {
/// let content = format_with(|f| {
/// let mut counter = Counter::default().memoized();
/// let counter_content = counter.inspect(f)?;
///
/// if counter_content.will_break() {
/// write!(f, [text("Counter:"), block_indent(&counter)])
/// } else {
/// write!(f, [text("Counter:"), counter])
/// }?;
///
/// write!(f, [counter])
/// });
///
///
/// let formatted = format!(SimpleFormatContext::default(), [content])?;
/// assert_eq!("Counter:\n\tCount: 0\nCount: 0\n", formatted.print()?.as_code());
/// # Ok(())
/// # }
///
/// ```
pub fn inspect(&mut self, f: &mut Formatter<Context>) -> FormatResult<&[FormatElement]> {
let result = self.memory.get_or_init(|| f.intern(&self.inner));
match result.as_ref() {
Ok(Some(FormatElement::Interned(interned))) => Ok(interned.deref()),
Ok(Some(other)) => Ok(std::slice::from_ref(other)),
Ok(None) => Ok(&[]),
Err(error) => Err(*error),
}
}
}
impl<F, Context> Format<Context> for Memoized<F, Context>
where
F: Format<Context>,
{
fn fmt(&self, f: &mut Formatter<Context>) -> FormatResult<()> {
let result = self.memory.get_or_init(|| f.intern(&self.inner));
match result {
Ok(Some(elements)) => {
f.write_element(elements.clone())?;
Ok(())
}
Ok(None) => Ok(()),
Err(err) => Err(*err),
}
}
}