Implement a very basic comment help provider

Author: Kapil Borle

src/features/HelpCompletion.ts

@@ -4,17 +4,34 @@
 
 import vscode = require("vscode");
 import { IFeature } from "../feature";
-import { TextDocumentChangeEvent, workspace, Disposable } from "vscode";
-import { LanguageClient } from "vscode-languageclient/lib/main";
+import { TextDocumentChangeEvent, workspace, Disposable, Position } from "vscode";
+import { LanguageClient, RequestType } from "vscode-languageclient";
+
+export namespace CommentHelpRequest {
+    export const type = new RequestType<any, any, void, void>("powerShell/getCommentHelp");
+}
+
+interface CommentHelpRequestParams {
+    documentUri: string;
+    triggerPosition: Position;
+}
+
+interface CommentHelpRequestResult {
+    content: string[];
+}
+
+enum SearchState { Searching, Locked, Found };
 
 export class HelpCompletionFeature implements IFeature {
     private languageClient: LanguageClient;
     private triggerCharacters: string;
     private disposable: Disposable;
+    private searchState: SearchState;
     constructor() {
         this.triggerCharacters = "#<";
         let subscriptions = [];
         workspace.onDidChangeTextDocument(this.onEvent, this, subscriptions);
+        this.searchState = SearchState.Searching;
         this.disposable = Disposable.from(...subscriptions);
     }
 
@@ -23,10 +40,54 @@ export class HelpCompletionFeature implements IFeature {
     }
 
     dispose() {
-
+        this.disposable.dispose();
     }
 
     onEvent(changeEvent: TextDocumentChangeEvent): void {
-        console.log(`event triggered. change content: ${changeEvent.contentChanges[0].text}`);
+        let text = changeEvent.contentChanges[0].text;
+        switch (this.searchState) {
+            case SearchState.Searching:
+                if (text.length === 1 && text[0] === this.triggerCharacters[0]) {
+                    this.searchState = SearchState.Locked;
+                }
+                break;
+
+            case SearchState.Locked:
+                if (text.length === 1 && text[0] === this.triggerCharacters[1]) {
+                    this.searchState = SearchState.Found;
+                }
+                break;
+        }
+
+        let r = changeEvent.contentChanges[0].range;
+        console.log(`Search State: ${this.searchState.toString()}; Range: (${r.start.line}, ${r.start.character}), (${r.end.line}, ${r.end.character})`);
+        if (this.searchState === SearchState.Found) {
+            this.searchState = SearchState.Searching;
+            if (this.languageClient) {
+                let change = changeEvent.contentChanges[0];
+                let triggerStartPos = change.range.start;
+                let triggerEndPos = change.range.end;
+                let doc = changeEvent.document;
+                this.languageClient.sendRequest(
+                    CommentHelpRequest.type,
+                    {
+                        documentUri: changeEvent.document.uri.toString(),
+                        triggerPosition: triggerStartPos
+                    }).then(result => {
+                        let content = result.content;
+                        if (content === undefined) {
+                            return;
+                        }
+
+                        // todo allow "##" as trigger characters
+                        // todo remove the new line after help block
+                        // todo get the eol character programmatically or let the server return one whole string
+                        let editor = vscode.window.activeTextEditor;
+                        let replaceRange = new vscode.Range(triggerStartPos.translate(0, -1), triggerStartPos.translate(0, 1));
+                        let text = content.join("\r\n");
+                        editor.edit(editbuilder => editbuilder.replace(replaceRange, text));
+                    });
+            }
+        }
     }
 }