fix: initial hover functionality (#46)

![image](https://github.com/github-language-server/github-lsp/assets/721090/d9edeaa3-f433-4203-a7bb-533c1563fafc)

Here's `hover` triggered over an issue.

Closes #43

Author: AlexanderBrevig

src/backend.rs

@@ -4,9 +4,10 @@ use octocrab::models::{Author, Repository};
 use octocrab::params::State;
 use octocrab::Octocrab;
 use ropey::Rope;
-use tower_lsp::jsonrpc::Result;
+use tower_lsp::jsonrpc::{self, Result};
 use tower_lsp::lsp_types::{
-    CompletionItem, CompletionTextEdit, MessageType, Range, TextDocumentItem, TextEdit,
+    CompletionItem, CompletionTextEdit, Hover, HoverContents, MarkupContent, MarkupKind,
+    MessageType, Range, TextDocumentItem, TextEdit,
 };
 use tower_lsp::{lsp_types::Position, Client};
 
@@ -31,6 +32,20 @@ pub struct Backend {
 impl Backend {
     const PER_PAGE: u8 = 100;
 
+    pub fn new(client: Client, octocrab: Octocrab, owner: String, repo: String) -> Backend {
+        Backend {
+            client,
+            octocrab,
+            owner,
+            repo,
+            document_map: DashMap::new(),
+            repository_map: DashMap::new(),
+            issue_map: DashMap::new(),
+            member_map: DashMap::new(),
+            wiki_map: DashMap::new(),
+        }
+    }
+
     pub(crate) async fn initialize(&self) {
         self.initialize_issues().await;
         self.initialize_members().await;
@@ -39,6 +54,63 @@ impl Backend {
         self.initialize_wiki().await;
     }
 
+    pub async fn on_hover(&self, link: String) -> Result<Option<Hover>> {
+        let mut text = String::new();
+        //FIX: probably will cause issues for someone, maybe?
+        if link.contains("github.com") {
+            let link = link.replace("https://github.com/", "");
+            let parts = link.split('/');
+            let identifier = parts
+                .last()
+                .ok_or("No issue part in URL")
+                .map_err(|_| jsonrpc::Error::method_not_found())?;
+            if link.contains("issues") {
+                let issue = self
+                    .issue_map
+                    .iter()
+                    .filter(|issue| issue.get_label().starts_with(&format!("#{} ", identifier)))
+                    .last()
+                    .ok_or("No issue")
+                    .map_err(|_| jsonrpc::Error::method_not_found())?;
+                text = issue.get_detail().to_string();
+            } else if link.contains("wiki") {
+                text = format!("# Wiki article {}", identifier);
+            } else if link.contains('/') {
+                let repository = self
+                    .repository_map
+                    .iter()
+                    .filter(|repo| repo.get_label() == link)
+                    .last()
+                    .ok_or("No repo")
+                    .map_err(|_| jsonrpc::Error::method_not_found())?;
+                text = repository.get_detail().to_string();
+            } else {
+                let users = octocrab::instance()
+                    .search()
+                    .users(identifier)
+                    .per_page(1)
+                    .page(0u32)
+                    .send()
+                    .await
+                    .map_err(|_| {
+                        tower_lsp::jsonrpc::Error::new(
+                            tower_lsp::jsonrpc::ErrorCode::MethodNotFound,
+                        )
+                    })?;
+                let user = &users.items[0];
+                text = format!("# User {}", user.login.to_owned());
+            }
+        }
+        let hover = Hover {
+            contents: HoverContents::Markup(MarkupContent {
+                kind: MarkupKind::Markdown,
+                value: text,
+            }),
+            range: None,
+        };
+        Ok(Some(hover))
+    }
+
     pub(crate) async fn search_issue_and_pr(
         &self,
         position: Position,
@@ -340,18 +412,4 @@ impl Backend {
             self.member_map.insert(member.login.to_owned(), member);
         });
     }
-
-    pub fn new(client: Client, octocrab: Octocrab, owner: String, repo: String) -> Backend {
-        Backend {
-            client,
-            octocrab,
-            owner,
-            repo,
-            document_map: DashMap::new(),
-            repository_map: DashMap::new(),
-            issue_map: DashMap::new(),
-            member_map: DashMap::new(),
-            wiki_map: DashMap::new(),
-        }
-    }
 }

src/lsp.rs

@@ -31,6 +31,7 @@ impl LanguageServer for Backend {
 
                     file_operations: None,
                 }),
+                hover_provider: Some(HoverProviderCapability::Simple(true)),
                 ..ServerCapabilities::default()
             },
         })
@@ -174,4 +175,71 @@ impl LanguageServer for Backend {
         };
         Ok(completions.map(CompletionResponse::Array))
     }
+
+    async fn hover(&self, params: HoverParams) -> Result<Option<Hover>> {
+        let uri = params.text_document_position_params.text_document.uri;
+        let position = params.text_document_position_params.position;
+        let rope = self
+            .document_map
+            .get(&uri.to_string())
+            .ok_or(tower_lsp::jsonrpc::Error::invalid_request())?;
+
+        let line = rope
+            .get_line(position.line as usize)
+            .ok_or(tower_lsp::jsonrpc::Error::internal_error())?;
+        let character_pos = position.character as usize;
+
+        //TODO: cleanup parsing; possible to clean up with treesitter? need to investigate
+        let line = line.to_string();
+        let line = line.trim();
+        // scan backwards
+        let mut start = character_pos;
+        let mut start_search = start;
+        start = usize::MAX;
+        loop {
+            // look for the start of the (..) link part
+            if line.as_bytes()[start_search] == b'(' {
+                start = start_search + 1; // skip (
+                break;
+            }
+            if start_search == 0 {
+                break;
+            }
+            start_search -= 1;
+        }
+        // scan forwards
+        let mut end = character_pos;
+        let mut end_search = end;
+        end = usize::MIN;
+        loop {
+            // handle hover over the [..] part of a link
+            if start == usize::MAX && line.as_bytes()[end_search] == b'(' {
+                start = end_search + 1;
+            }
+            if line.as_bytes()[end_search] == b')' {
+                end = end_search; // str[..] slice will exclude ), non inclusive
+                break;
+            }
+            if end_search == line.len() - 1 {
+                break;
+            }
+            end_search += 1;
+        }
+
+        if start == usize::MAX || end == usize::MIN || start >= end {
+            self.client
+                .log_message(
+                    MessageType::ERROR,
+                    format!(
+                        "Hover search failed with invalid start {} end {} for line {}",
+                        start, end, line
+                    ),
+                )
+                .await;
+            return Ok(None);
+        }
+        let link: String = line[start..end].into();
+
+        self.on_hover(link).await
+    }
 }