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use hir::db::HirDatabase;
use ra_text_edit::TextEditBuilder;
use ra_db::FileRange;
use ra_syntax::{
SourceFile, TextRange, AstNode, TextUnit, SyntaxNode,
algo::{find_leaf_at_offset, find_node_at_offset, find_covering_node, LeafAtOffset},
};
use ra_ide_api_light::formatting::{leading_indent, reindent};
use crate::{AssistLabel, AssistAction};
pub(crate) enum Assist {
Unresolved(AssistLabel),
Resolved(AssistLabel, AssistAction),
}
/// `AssistCtx` allows to apply an assist or check if it could be applied.
///
/// Assists use a somewhat overengineered approach, given the current needs. The
/// assists workflow consists of two phases. In the first phase, a user asks for
/// the list of available assists. In the second phase, the user picks a
/// particular assist and it gets applied.
///
/// There are two peculiarities here:
///
/// * first, we ideally avoid computing more things then necessary to answer
/// "is assist applicable" in the first phase.
/// * second, when we are applying assist, we don't have a guarantee that there
/// weren't any changes between the point when user asked for assists and when
/// they applied a particular assist. So, when applying assist, we need to do
/// all the checks from scratch.
///
/// To avoid repeating the same code twice for both "check" and "apply"
/// functions, we use an approach reminiscent of that of Django's function based
/// views dealing with forms. Each assist receives a runtime parameter,
/// `should_compute_edit`. It first check if an edit is applicable (potentially
/// computing info required to compute the actual edit). If it is applicable,
/// and `should_compute_edit` is `true`, it then computes the actual edit.
///
/// So, to implement the original assists workflow, we can first apply each edit
/// with `should_compute_edit = false`, and then applying the selected edit
/// again, with `should_compute_edit = true` this time.
///
/// Note, however, that we don't actually use such two-phase logic at the
/// moment, because the LSP API is pretty awkward in this place, and it's much
/// easier to just compute the edit eagerly :-)#[derive(Debug, Clone)]
#[derive(Debug)]
pub(crate) struct AssistCtx<'a, DB> {
pub(crate) db: &'a DB,
pub(crate) frange: FileRange,
source_file: &'a SourceFile,
should_compute_edit: bool,
}
impl<'a, DB> Clone for AssistCtx<'a, DB> {
fn clone(&self) -> Self {
AssistCtx {
db: self.db,
frange: self.frange,
source_file: self.source_file,
should_compute_edit: self.should_compute_edit,
}
}
}
impl<'a, DB: HirDatabase> AssistCtx<'a, DB> {
pub(crate) fn with_ctx<F, T>(db: &DB, frange: FileRange, should_compute_edit: bool, f: F) -> T
where
F: FnOnce(AssistCtx<DB>) -> T,
{
let source_file = &db.parse(frange.file_id);
let ctx = AssistCtx {
db,
frange,
source_file,
should_compute_edit,
};
f(ctx)
}
pub(crate) fn build(
self,
label: impl Into<String>,
f: impl FnOnce(&mut AssistBuilder),
) -> Option<Assist> {
let label = AssistLabel {
label: label.into(),
};
if !self.should_compute_edit {
return Some(Assist::Unresolved(label));
}
let action = {
let mut edit = AssistBuilder::default();
f(&mut edit);
edit.build()
};
Some(Assist::Resolved(label, action))
}
pub(crate) fn leaf_at_offset(&self) -> LeafAtOffset<&'a SyntaxNode> {
find_leaf_at_offset(self.source_file.syntax(), self.frange.range.start())
}
pub(crate) fn node_at_offset<N: AstNode>(&self) -> Option<&'a N> {
find_node_at_offset(self.source_file.syntax(), self.frange.range.start())
}
pub(crate) fn covering_node(&self) -> &'a SyntaxNode {
find_covering_node(self.source_file.syntax(), self.frange.range)
}
}
#[derive(Default)]
pub(crate) struct AssistBuilder {
edit: TextEditBuilder,
cursor_position: Option<TextUnit>,
}
impl AssistBuilder {
pub(crate) fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
self.edit.replace(range, replace_with.into())
}
pub(crate) fn replace_node_and_indent(
&mut self,
node: &SyntaxNode,
replace_with: impl Into<String>,
) {
let mut replace_with = replace_with.into();
if let Some(indent) = leading_indent(node) {
replace_with = reindent(&replace_with, indent)
}
self.replace(node.range(), replace_with)
}
#[allow(unused)]
pub(crate) fn delete(&mut self, range: TextRange) {
self.edit.delete(range)
}
pub(crate) fn insert(&mut self, offset: TextUnit, text: impl Into<String>) {
self.edit.insert(offset, text.into())
}
pub(crate) fn set_cursor(&mut self, offset: TextUnit) {
self.cursor_position = Some(offset)
}
fn build(self) -> AssistAction {
AssistAction {
edit: self.edit.finish(),
cursor_position: self.cursor_position,
}
}
}
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