1 files changed, 244 insertions, 0 deletions

diff --git a/crates/ra_ide_api/src/completion/completion_item.rs b/crates/ra_ide_api/src/completion/completion_item.rs
new file mode 100644
index 000000000..a25b87bee
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/completion_item.rs
@@ -0,0 +1,244 @@
+use hir::PerNs;
+
+use crate::completion::CompletionContext;
+
+/// `CompletionItem` describes a single completion variant in the editor pop-up.
+/// It is basically a POD with various properties. To construct a
+/// `CompletionItem`, use `new` method and the `Builder` struct.
+#[derive(Debug)]
+pub struct CompletionItem {
+    /// Used only internally in tests, to check only specific kind of
+    /// completion.
+    completion_kind: CompletionKind,
+    label: String,
+    lookup: Option<String>,
+    snippet: Option<String>,
+    kind: Option<CompletionItemKind>,
+}
+
+pub enum InsertText {
+    PlainText { text: String },
+    Snippet { text: String },
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CompletionItemKind {
+    Snippet,
+    Keyword,
+    Module,
+    Function,
+    Struct,
+    Enum,
+    EnumVariant,
+    Binding,
+    Field,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) enum CompletionKind {
+    /// Parser-based keyword completion.
+    Keyword,
+    /// Your usual "complete all valid identifiers".
+    Reference,
+    /// "Secret sauce" completions.
+    Magic,
+    Snippet,
+}
+
+impl CompletionItem {
+    pub(crate) fn new(completion_kind: CompletionKind, label: impl Into<String>) -> Builder {
+        let label = label.into();
+        Builder {
+            completion_kind,
+            label,
+            lookup: None,
+            snippet: None,
+            kind: None,
+        }
+    }
+    /// What user sees in pop-up in the UI.
+    pub fn label(&self) -> &str {
+        &self.label
+    }
+    /// What string is used for filtering.
+    pub fn lookup(&self) -> &str {
+        self.lookup
+            .as_ref()
+            .map(|it| it.as_str())
+            .unwrap_or(self.label())
+    }
+    /// What is inserted.
+    pub fn insert_text(&self) -> InsertText {
+        match &self.snippet {
+            None => InsertText::PlainText {
+                text: self.label.clone(),
+            },
+            Some(it) => InsertText::Snippet { text: it.clone() },
+        }
+    }
+
+    pub fn kind(&self) -> Option<CompletionItemKind> {
+        self.kind
+    }
+}
+
+/// A helper to make `CompletionItem`s.
+#[must_use]
+pub(crate) struct Builder {
+    completion_kind: CompletionKind,
+    label: String,
+    lookup: Option<String>,
+    snippet: Option<String>,
+    kind: Option<CompletionItemKind>,
+}
+
+impl Builder {
+    pub(crate) fn add_to(self, acc: &mut Completions) {
+        acc.add(self.build())
+    }
+
+    pub(crate) fn build(self) -> CompletionItem {
+        CompletionItem {
+            label: self.label,
+            lookup: self.lookup,
+            snippet: self.snippet,
+            kind: self.kind,
+            completion_kind: self.completion_kind,
+        }
+    }
+    pub(crate) fn lookup_by(mut self, lookup: impl Into<String>) -> Builder {
+        self.lookup = Some(lookup.into());
+        self
+    }
+    pub(crate) fn snippet(mut self, snippet: impl Into<String>) -> Builder {
+        self.snippet = Some(snippet.into());
+        self
+    }
+    pub(crate) fn kind(mut self, kind: CompletionItemKind) -> Builder {
+        self.kind = Some(kind);
+        self
+    }
+    pub(super) fn from_resolution(
+        mut self,
+        ctx: &CompletionContext,
+        resolution: &hir::Resolution,
+    ) -> Builder {
+        let resolved = resolution.def_id.and_then(|d| d.resolve(ctx.db).ok());
+        let kind = match resolved {
+            PerNs {
+                types: Some(hir::Def::Module(..)),
+                ..
+            } => CompletionItemKind::Module,
+            PerNs {
+                types: Some(hir::Def::Struct(..)),
+                ..
+            } => CompletionItemKind::Struct,
+            PerNs {
+                types: Some(hir::Def::Enum(..)),
+                ..
+            } => CompletionItemKind::Enum,
+            PerNs {
+                values: Some(hir::Def::Function(function)),
+                ..
+            } => return self.from_function(ctx, function),
+            _ => return self,
+        };
+        self.kind = Some(kind);
+        self
+    }
+
+    fn from_function(mut self, ctx: &CompletionContext, function: hir::Function) -> Builder {
+        // If not an import, add parenthesis automatically.
+        if ctx.use_item_syntax.is_none() {
+            if function.signature(ctx.db).args().is_empty() {
+                self.snippet = Some(format!("{}()$0", self.label));
+            } else {
+                self.snippet = Some(format!("{}($0)", self.label));
+            }
+        }
+        self.kind = Some(CompletionItemKind::Function);
+        self
+    }
+}
+
+impl Into<CompletionItem> for Builder {
+    fn into(self) -> CompletionItem {
+        self.build()
+    }
+}
+
+/// Represents an in-progress set of completions being built.
+#[derive(Debug, Default)]
+pub(crate) struct Completions {
+    buf: Vec<CompletionItem>,
+}
+
+impl Completions {
+    pub(crate) fn add(&mut self, item: impl Into<CompletionItem>) {
+        self.buf.push(item.into())
+    }
+    pub(crate) fn add_all<I>(&mut self, items: I)
+    where
+        I: IntoIterator,
+        I::Item: Into<CompletionItem>,
+    {
+        items.into_iter().for_each(|item| self.add(item.into()))
+    }
+
+    #[cfg(test)]
+    pub(crate) fn assert_match(&self, expected: &str, kind: CompletionKind) {
+        let expected = normalize(expected);
+        let actual = self.debug_render(kind);
+        test_utils::assert_eq_text!(expected.as_str(), actual.as_str(),);
+
+        /// Normalize the textual representation of `Completions`:
+        /// replace `;` with newlines, normalize whitespace
+        fn normalize(expected: &str) -> String {
+            use ra_syntax::{tokenize, TextUnit, TextRange, SyntaxKind::SEMI};
+            let mut res = String::new();
+            for line in expected.trim().lines() {
+                let line = line.trim();
+                let mut start_offset: TextUnit = 0.into();
+                // Yep, we use rust tokenize in completion tests :-)
+                for token in tokenize(line) {
+                    let range = TextRange::offset_len(start_offset, token.len);
+                    start_offset += token.len;
+                    if token.kind == SEMI {
+                        res.push('\n');
+                    } else {
+                        res.push_str(&line[range]);
+                    }
+                }
+
+                res.push('\n');
+            }
+            res
+        }
+    }
+
+    #[cfg(test)]
+    fn debug_render(&self, kind: CompletionKind) -> String {
+        let mut res = String::new();
+        for c in self.buf.iter() {
+            if c.completion_kind == kind {
+                if let Some(lookup) = &c.lookup {
+                    res.push_str(lookup);
+                    res.push_str(&format!(" {:?}", c.label));
+                } else {
+                    res.push_str(&c.label);
+                }
+                if let Some(snippet) = &c.snippet {
+                    res.push_str(&format!(" {:?}", snippet));
+                }
+                res.push('\n');
+            }
+        }
+        res
+    }
+}
+
+impl Into<Vec<CompletionItem>> for Completions {
+    fn into(self) -> Vec<CompletionItem> {
+        self.buf
+    }
+}