feat: Add clear command to clear the canvas

[krishivsaini]

• Created ClearStatement.java AST node
• Added CLEAR token type to TokenType enum
• Updated Lexer to recognize 'clear' keyword
• Added parseClearStatement method to Parser
• Implemented ClearStatement evaluation in Evaluator to emit ClearEvent
• Users can now use 'clear' command to reset the canvas during execution

Summary by CodeRabbit

• New Features
  • Introduced the "clear" command, allowing users to reset and clear the canvas at any point during program execution. This new command integrates seamlessly with the existing command set and enables enhanced control over canvas graphics.

[coderabbitai]

Walkthrough

The pull request adds support for a new "clear" command throughout the kidcode-core system. The "clear" keyword is recognized by the lexer as TokenType.CLEAR, parsed by the parser into a ClearStatement AST node, and evaluated by the evaluator to emit a ClearEvent for canvas clearing.

Changes

Cohort / File(s)	Summary
Lexical Recognition kidcode-core/src/main/java/com/kidcode/core/lexer/TokenType.java, kidcode-core/src/main/java/com/kidcode/core/lexer/Lexer.java	New CLEAR enum member added to TokenType; "clear" keyword mapped to TokenType.CLEAR in Lexer initialization
AST & Parsing kidcode-core/src/main/java/com/kidcode/core/ast/ClearStatement.java, kidcode-core/src/main/java/com/kidcode/core/parser/Parser.java	New ClearStatement record implementing Statement interface; parseClearStatement() method added to route CLEAR tokens; IfStatement parsing modified with unconditional advanceToNextStatement() call
Evaluation kidcode-core/src/main/java/com/kidcode/core/evaluator/Evaluator.java	ClearStatement handling added to emit ClearEvent for canvas clearing

Sequence Diagram

sequenceDiagram
    participant Input as Input: "clear"
    participant Lexer
    participant Parser
    participant Evaluator
    participant Event as ClearEvent

    Input->>Lexer: Scan "clear"
    Lexer->>Lexer: Match CLEAR keyword
    Lexer-->>Parser: TokenType.CLEAR token
    Parser->>Parser: parseClearStatement()
    Parser-->>Evaluator: ClearStatement node
    Evaluator->>Evaluator: Handle ClearStatement
    Evaluator->>Event: Emit ClearEvent
    Event-->>Event: Canvas cleared

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Parser.java IfStatement control-flow modification: The unconditional advanceToNextStatement() call after if-block processing requires careful verification to ensure it doesn't alter existing token stream behavior or introduce regressions in conditional statement parsing
• Integration consistency: Verify that ClearEvent emission in Evaluator follows the same pattern as other statement events (HomeStatement reference noted in summary)
• Cross-layer alignment: Confirm token flow between Lexer → Parser → Evaluator layers for the new CLEAR command is consistent with existing command patterns

Poem

🎨 A canvas cleared, a fresh new start,
The clear command—a rabbit's art!
From lexer's eye to parser's mind,
To evaluator's work, a new design.
Hop-hop, sweep-sweep, the screen's reset,
Drawing anew without a fret! 🐰✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The PR title "feat: Add clear command to clear the canvas" is directly and fully related to the primary change in the changeset. The pull request introduces a complete implementation of a clear command across multiple layers: a new ClearStatement AST node, CLEAR token type, lexer keyword mapping, parser support, and evaluator integration. The title accurately summarizes this main feature and is concise, specific, and free of vague terminology or noise. A reviewer scanning the commit history would clearly understand that this PR adds a clear command to reset the canvas.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

kidcode-core/src/main/java/com/kidcode/core/evaluator/Evaluator.java (1)

141-144: Emit a MoveEvent after ClearEvent to re-seed turtle state

After clearing, also send a zero-distance MoveEvent so the UI redraws the turtle at its current position/direction even if no move follows.

-        } else if (stmt instanceof ClearStatement) {
-            // Emit a clear event to clear the canvas
-            events.add(new ExecutionEvent.ClearEvent());
+        } else if (stmt instanceof ClearStatement) {
+            events.add(new ExecutionEvent.ClearEvent());
+            // Re-emit current state so the renderer redraws the turtle post-clear.
+            events.add(new ExecutionEvent.MoveEvent(
+                env.getX(), env.getY(), env.getX(), env.getY(),
+                env.getDirection(), env.isPenDown(), env.getPenColor()
+            ));
         }

kidcode-core/src/main/java/com/kidcode/core/parser/Parser.java (1)

148-152: No-arg parse is fine; optionally guard against trailing tokens

Implementation mirrors HOME. For better UX, consider detecting unexpected tokens after “clear” on the same line and adding a specific error (“'clear' takes no arguments”).

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d99503a and fd4d301.

📒 Files selected for processing (5)

• kidcode-core/src/main/java/com/kidcode/core/ast/ClearStatement.java (1 hunks)
• kidcode-core/src/main/java/com/kidcode/core/evaluator/Evaluator.java (1 hunks)
• kidcode-core/src/main/java/com/kidcode/core/lexer/Lexer.java (1 hunks)
• kidcode-core/src/main/java/com/kidcode/core/lexer/TokenType.java (1 hunks)
• kidcode-core/src/main/java/com/kidcode/core/parser/Parser.java (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

kidcode-core/src/main/java/com/kidcode/core/evaluator/Evaluator.java (1)

kidcode-web/src/main/resources/static/app.js (1)

• events (273-273)

🔇 Additional comments (4)

kidcode-core/src/main/java/com/kidcode/core/ast/ClearStatement.java (1)

3-6: LGTM; tiny polish

Record-based AST node is consistent. Optionally add a brief Javadoc for grammar (“clear” takes no args). Also confirm the module’s target JDK supports records.

kidcode-core/src/main/java/com/kidcode/core/lexer/TokenType.java (1)

5-5: Enum addition looks good

CLEAR fits under commands; no conflicts spotted.

kidcode-core/src/main/java/com/kidcode/core/lexer/Lexer.java (1)

35-36: Keyword mapping is correct

"clear" → TokenType.CLEAR aligns with TokenType and parser changes.

kidcode-core/src/main/java/com/kidcode/core/parser/Parser.java (1)

77-79: Routing for CLEAR added correctly

Dispatch to parseClearStatement keeps statement table consistent.