fix(core): prevent TCP chunk escape sequence breakage in InputParser

[ionfwsrijan]

Fix: InputParser TCP chunk escape sequence breakage

Changes

packages/core/src/input/InputParser.ts

• Replaced the fixed 200ms timeout for lone ESC bytes with a new _startEscapeTimeout() method that uses a 500ms timeout.
• Added timeout restart in the escape buffer concatenation handler: each partial chunk resets the timer, preventing false standalone ESC emission.
• Cleaned up the lone ESC code path by extracting timeout logic into its own method.

Fixes

• Escape sequences fragmented across TCP chunks (SSH, serial connections) with >200ms gaps were incorrectly parsed as standalone Escape keypresses followed by garbage characters
• After the initial ESC timeout fired, subsequent sequence bytes were processed as regular input, corrupting the input stream
• 200ms window was too aggressive for high-latency network connections

Closes #1957

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of the Escape key so incomplete or delayed key sequences are buffered more reliably.
  • Restarts the Escape timeout when more input arrives, reducing misread key events.
  • Lone Escape presses now emit consistently after a short delay.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: cef0eeba-e532-435d-a07d-41bc80546846

📥 Commits

Reviewing files that changed from the base of the PR and between 3833157 and 92bd707.

📒 Files selected for processing (2)

• packages/core/src/input/InputParser.test.ts
• packages/core/src/input/InputParser.ts

📝 Walkthrough

Walkthrough

Escape-key parsing in InputParser.ts was refactored to use a new _startEscapeTimeout() method that centralizes timeout management for buffered escape sequences. The lone-ESC inline setTimeout was replaced with buffering plus this helper, and fragmented escape parsing now restarts the timeout when bytes remain incomplete.

Changes

Escape Timeout Consolidation

Layer / File(s)	Summary
New _startEscapeTimeout() helper packages/core/src/input/InputParser.ts	Adds a private method that clears any existing timeout, sets a 500ms timer, and on expiry emits an escape key event from _escapeBuffer, then clears the buffer and timeout handle.
Wire helper into ESC handling paths packages/core/src/input/InputParser.ts	Restarts the escape timeout via the new helper after _tryParseEscape() when buffered bytes remain incomplete, and replaces the lone-ESC inline setTimeout with buffering plus a call to _startEscapeTimeout().

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• Karanjot786/TermUI#770: Both PRs modify InputParser.ts's escape-sequence buffering/timeout emission logic.
• Karanjot786/TermUI#1064: Both PRs change escape-buffering/parsing logic to prevent mis-emitting keys from split escape sequences.
• Karanjot786/TermUI#1806: Both PRs modify escape-buffering/timeout logic including _tryParseEscape behavior.

Suggested labels: level:intermediate

Suggested reviewers: Karanjot786

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the InputParser escape-sequence fix.
Description check	✅ Passed	It covers the change summary and linked issue, though some template sections like package list and checklist are omitted.
Linked Issues check	✅ Passed	The changes match #1957 by buffering fragmented ESC sequences and restarting the timer so split control keys parse correctly.
Out of Scope Changes check	✅ Passed	The patch stays focused on InputParser escape handling and adds no unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

packages/core/src/input/InputParser.ts (1)

203-207: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Add the escape timeout in packages/core/src/input/InputParser.ts:203-207.
When the first chunk starts with \x1b but already has more bytes, _tryParseEscape() can leave _escapeBuffer populated without scheduling _startEscapeTimeout(), so a stalled sequence can keep swallowing later keystrokes.

Proposed fix

         if (str.startsWith('\x1b')) {
             this._escapeBuffer = data;
             this._tryParseEscape();
+            if (this._escapeBuffer.length > 0) {
+                this._startEscapeTimeout();
+            }
             return;
         }

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/core/src/input/InputParser.ts` around lines 203 - 207, The
escape-sequence handling in InputParser._tryParseEscape can leave _escapeBuffer
set without starting the escape timeout when the first chunk begins with \x1b
and already contains more bytes. Update the early escape branch in InputParser
to schedule _startEscapeTimeout() whenever _escapeBuffer is populated from that
path, so stalled sequences will still time out and stop swallowing later
keystrokes.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/core/src/input/InputParser.ts`:
- Around line 314-336: Update the escape-sequence tests to match the new 500ms
behavior in InputParser._startEscapeTimeout so they still cover the standalone
Escape path; replace the existing 200ms/250ms timing in the relevant tests with
500ms-safe advances. Also extract the hardcoded 500 in _startEscapeTimeout into
a shared ESCAPE_TIMEOUT_MS constant (ideally reused with the paste timeout) so
the timeout value stays consistent across implementation and tests.

---

Outside diff comments:
In `@packages/core/src/input/InputParser.ts`:
- Around line 203-207: The escape-sequence handling in
InputParser._tryParseEscape can leave _escapeBuffer set without starting the
escape timeout when the first chunk begins with \x1b and already contains more
bytes. Update the early escape branch in InputParser to schedule
_startEscapeTimeout() whenever _escapeBuffer is populated from that path, so
stalled sequences will still time out and stop swallowing later keystrokes.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: ef502fc8-bdbf-45bf-a39a-889bd73227bf

📥 Commits

Reviewing files that changed from the base of the PR and between 5f479e6 and 3833157.

📒 Files selected for processing (1)

• packages/core/src/input/InputParser.ts

[ionfwsrijan]

@Karanjot786 Please review this