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//! Files.
use std::borrow::Cow;
use enum_dispatch::enum_dispatch;
pub(crate) use crate::control::ControlledFile;
pub(crate) use crate::loaded_file::LoadedFile;
/// An identifier for a file streampager is paging.
pub type FileIndex = usize;
/// Default value for `needed_lines`.
pub(crate) const DEFAULT_NEEDED_LINES: usize = 5000;
/// Trait for getting information from a file.
#[enum_dispatch]
pub(crate) trait FileInfo {
/// The file's index.
fn index(&self) -> FileIndex;
/// The file's title.
fn title(&self) -> Cow<'_, str>;
/// The file's info.
fn info(&self) -> Cow<'_, str>;
/// True once the file is loaded and all newlines have been parsed.
fn loaded(&self) -> bool;
/// Returns the number of lines in the file.
fn lines(&self) -> usize;
/// Runs the `call` function, passing it the contents of line `index`.
/// Tries to avoid copying the data if possible, however the borrowed
/// line only lasts as long as the function call.
fn with_line<T, F>(&self, index: usize, call: F) -> Option<T>
where
F: FnMut(Cow<'_, [u8]>) -> T;
/// Set how many lines are needed.
///
/// If `self.lines()` exceeds that number, pause loading until
/// `set_needed_lines` is called with a larger number.
/// This is only effective for "streamed" input.
fn set_needed_lines(&self, lines: usize);
/// True if the loading thread has been paused.
fn paused(&self) -> bool;
}
/// A file.
#[enum_dispatch(FileInfo)]
#[derive(Clone)]
pub(crate) enum File {
LoadedFile,
ControlledFile,
}