Refactor/activity abc parser

[vanshika2720]

refactor: extract ABC parser into js/activity/abc-parser.js

Description

This PR extracts the ABC notation parser from js/activity.js into a dedicated module:

js/activity/abc-parser.js

The goal is to improve maintainability and reduce the size and complexity of the Activity implementation by isolating the ABC import subsystem into its own file.

Motivation

The ABC parser previously lived inline inside activity.js, which is one of the largest files in the codebase.

The parser is a self-contained subsystem responsible for:

• ABC note parsing
• Pitch conversion
• Duration conversion
• Block generation
• Repeat handling

Moving this logic into a dedicated module follows the same modularization approach already used by other Activity subsystems and makes future maintenance easier.

Changes

New module

Created:

js/activity/abc-parser.js

The module now contains:

• _adjustPitch()
• _abcToStandardValue()
• _createPitchBlocks()
• _searchIndexForMusicBlock()
• setupActivityAbcParser()

setupActivityAbcParser() attaches parseABC() to the Activity instance during initialization.

Activity integration

Removed the inline ABC parser implementation from:

js/activity.js

and replaced it with:

setupActivityAbcParser(this);

Loader updates

Updated:

js/loader.js

to:

• register the activity/abc-parser RequireJS path
• load the parser module before Activity initialization

Test updates

Updated:

js/__tests__/activity_startup_recovery.test.js

with a no-op setupActivityAbcParser() implementation required by the VM sandbox used in the test.

Added:

js/activity/__tests__/abc-parser.test.js

to provide coverage for:

• single-voice parsing
• multi-voice parsing
• repeat handling
• triplets
• key signature accidentals

Defensive improvements

While extracting the parser, a small number of defensive checks were added around:

• empty or incomplete voice structures
• repeat block boundary handling

These guards prevent runtime failures caused by malformed or incomplete ABC data while preserving existing behavior for valid inputs.

Preserved behavior

The following remain unchanged:

• Public API (this.parseABC(tune))
• ABC import workflow
• Generated Music Blocks structure for valid inputs
• User-facing functionality
• Existing Activity initialization flow

Result

This refactor improves separation of concerns by moving the ABC parser into its own module while maintaining compatibility with the existing ABC import pipeline and adding test coverage around parser behavior.
-[x] Documentation
-[x] Tests

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.36% | Branches: 40.05% | Functions: 53.02% | Lines: 48.74%
Master Coverage: Statements: 48.36% | Branches: 40.07% | Functions: 53.05% | Lines: 48.75%

[github-actions]

This PR has merge conflicts with master.

Please rebase your branch:

# Add upstream remote (one-time setup)
git remote add upstream https://github.com/sugarlabs/musicblocks.git

# Fetch latest master and rebase
git fetch upstream
git rebase upstream/master

# Resolve any conflicts, then:
git push --force-with-lease origin YOUR_BRANCH

Tip: Enable "Allow edits from maintainers" on this PR so we can auto-rebase for you next time. This only grants access to your PR branch. Your fork's other branches are not affected.

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.3% | Functions: 53.24% | Lines: 48.92%
Master Coverage: Statements: 48.36% | Branches: 40.06% | Functions: 53.04% | Lines: 48.75%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.31% | Functions: 53.25% | Lines: 48.93%
Master Coverage: Statements: 48.36% | Branches: 40.06% | Functions: 53.04% | Lines: 48.75%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.3% | Functions: 53.25% | Lines: 48.92%
Master Coverage: Statements: 48.36% | Branches: 40.06% | Functions: 53.04% | Lines: 48.75%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.3% | Functions: 53.25% | Lines: 48.92%
Master Coverage: Statements: 48.36% | Branches: 40.06% | Functions: 53.04% | Lines: 48.75%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.29% | Functions: 53.25% | Lines: 48.92%
Master Coverage: Statements: 49.01% | Branches: 40.47% | Functions: 53.17% | Lines: 49.42%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.3% | Functions: 53.25% | Lines: 48.92%
Master Coverage: Statements: 49.12% | Branches: 40.56% | Functions: 53.32% | Lines: 49.54%

[github-actions]

🧪 Jest Test Results

✅ All Jest tests passed! This PR is ready to merge.

Coverage: Statements: 48.53% | Branches: 40.31% | Functions: 53.25% | Lines: 48.92%
Master Coverage: Statements: 49.12% | Branches: 40.56% | Functions: 53.32% | Lines: 49.54%