2 files changed, 137 insertions, 0 deletions

diff --git a/crates/ide_db/src/assists.rs b/crates/ide_db/src/assists.rs
new file mode 100644
index 000000000..7881d8369
--- /dev/null
+++ b/crates/ide_db/src/assists.rs
@@ -0,0 +1,136 @@
+//! This module defines the `Assist` data structure. The actual assist live in
+//! the `ide_assists` downstream crate. We want to define the data structures in
+//! this low-level crate though, because `ide_diagnostics` also need them
+//! (fixits for diagnostics and assists are the same thing under the hood). We
+//! want to compile `ide_assists` and `ide_diagnostics` in parallel though, so
+//! we pull the common definitions upstream, to this crate.
+
+use std::str::FromStr;
+
+use syntax::TextRange;
+
+use crate::{label::Label, source_change::SourceChange};
+
+#[derive(Debug, Clone)]
+pub struct Assist {
+    pub id: AssistId,
+    /// Short description of the assist, as shown in the UI.
+    pub label: Label,
+    pub group: Option<GroupLabel>,
+    /// Target ranges are used to sort assists: the smaller the target range,
+    /// the more specific assist is, and so it should be sorted first.
+    pub target: TextRange,
+    /// Computing source change sometimes is much more costly then computing the
+    /// other fields. Additionally, the actual change is not required to show
+    /// the lightbulb UI, it only is needed when the user tries to apply an
+    /// assist. So, we compute it lazily: the API allow requesting assists with
+    /// or without source change. We could (and in fact, used to) distinguish
+    /// between resolved and unresolved assists at the type level, but this is
+    /// cumbersome, especially if you want to embed an assist into another data
+    /// structure, such as a diagnostic.
+    pub source_change: Option<SourceChange>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AssistKind {
+    // FIXME: does the None variant make sense? Probably not.
+    None,
+
+    QuickFix,
+    Generate,
+    Refactor,
+    RefactorExtract,
+    RefactorInline,
+    RefactorRewrite,
+}
+
+impl AssistKind {
+    pub fn contains(self, other: AssistKind) -> bool {
+        if self == other {
+            return true;
+        }
+
+        match self {
+            AssistKind::None | AssistKind::Generate => true,
+            AssistKind::Refactor => match other {
+                AssistKind::RefactorExtract
+                | AssistKind::RefactorInline
+                | AssistKind::RefactorRewrite => true,
+                _ => false,
+            },
+            _ => false,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        match self {
+            AssistKind::None => "None",
+            AssistKind::QuickFix => "QuickFix",
+            AssistKind::Generate => "Generate",
+            AssistKind::Refactor => "Refactor",
+            AssistKind::RefactorExtract => "RefactorExtract",
+            AssistKind::RefactorInline => "RefactorInline",
+            AssistKind::RefactorRewrite => "RefactorRewrite",
+        }
+    }
+}
+
+impl FromStr for AssistKind {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "None" => Ok(AssistKind::None),
+            "QuickFix" => Ok(AssistKind::QuickFix),
+            "Generate" => Ok(AssistKind::Generate),
+            "Refactor" => Ok(AssistKind::Refactor),
+            "RefactorExtract" => Ok(AssistKind::RefactorExtract),
+            "RefactorInline" => Ok(AssistKind::RefactorInline),
+            "RefactorRewrite" => Ok(AssistKind::RefactorRewrite),
+            unknown => Err(format!("Unknown AssistKind: '{}'", unknown)),
+        }
+    }
+}
+
+/// Unique identifier of the assist, should not be shown to the user
+/// directly.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct AssistId(pub &'static str, pub AssistKind);
+
+/// A way to control how many asssist to resolve during the assist resolution.
+/// When an assist is resolved, its edits are calculated that might be costly to always do by default.
+#[derive(Debug)]
+pub enum AssistResolveStrategy {
+    /// No assists should be resolved.
+    None,
+    /// All assists should be resolved.
+    All,
+    /// Only a certain assist should be resolved.
+    Single(SingleResolve),
+}
+
+/// Hold the [`AssistId`] data of a certain assist to resolve.
+/// The original id object cannot be used due to a `'static` lifetime
+/// and the requirement to construct this struct dynamically during the resolve handling.
+#[derive(Debug)]
+pub struct SingleResolve {
+    /// The id of the assist.
+    pub assist_id: String,
+    // The kind of the assist.
+    pub assist_kind: AssistKind,
+}
+
+impl AssistResolveStrategy {
+    pub fn should_resolve(&self, id: &AssistId) -> bool {
+        match self {
+            AssistResolveStrategy::None => false,
+            AssistResolveStrategy::All => true,
+            AssistResolveStrategy::Single(single_resolve) => {
+                single_resolve.assist_id == id.0 && single_resolve.assist_kind == id.1
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct GroupLabel(pub String);
diff --git a/crates/ide_db/src/lib.rs b/crates/ide_db/src/lib.rs
index 105607dca..2ac215c06 100644
--- a/crates/ide_db/src/lib.rs
+++ b/crates/ide_db/src/lib.rs
@@ -3,6 +3,7 @@
 //! It is mainly a `HirDatabase` for semantic analysis, plus a `SymbolsDatabase`, for fuzzy search.
 
 mod apply_change;
+pub mod assists;
 pub mod label;
 pub mod line_index;
 pub mod symbol_index;