Summary

We want to rewrite website to Next.js while reducing lock-in to the metaframework. This issue tracks extracting framework-agnostic domain logic into standalone modules before / during the rewrite.

Goals

• Isolate domain logic from routing, rendering, browser APIs, and Next.js runtime concerns.
• Improve reuse across frontend, server routes, and tooling.
• Reduce migration risk by moving high-confidence pure logic first.

Proposed module split

1) @nusmods/timetable-core (high priority)

Extract from website/src/utils:

• timetables.ts
• timify.ts
• colors.ts
• optimiser.ts

Scope:

• Timetable modeling / validation
• Lesson arrangement and clash logic
• Serialization / deserialization
• Optimiser data transformations

2) @nusmods/planner-core

Extract:

• website/src/utils/planner.ts
• Pure planner selectors from website/src/selectors/planner.ts (after decoupling config/state access)

Scope:

• Prereq/conflict evaluation
• Planner domain invariants
• Planner text formatting for conflicts (non-UI)

3) @nusmods/nus-data-client

Extract:

• website/src/apis/nusmods.js
• Typed request clients from website/src/apis/{nextbus,weather,optimiser}.ts

Scope:

• Endpoint builders
• API request/response typing
• Transport adapter boundary (fetch/axios injectable)

4) @nusmods/route-schema

Extract:

• Pure path builders/parsers from website/src/views/routes/paths.ts

Scope:

• Route generation / parsing
• Share URL construction

Note:

• absolutePath() is browser-dependent and should remain as an app runtime helper.

Keep in Next.js app layer (not standalone)

• React view components (website/src/views/**)
• App entry/bootstrap (website/src/entry/**, website/src/bootstrapping/**)
• Redux wiring / persistence setup (configure-store, persistence adapters)
• Browser-only utilities (insertScript, localStorage wrappers, window/document helpers)
• Serverless platform wrappers (website/src/serverless/**, Vercel-specific handler wrappers)

Refactor prerequisites

• Split React/text helpers from domain helpers:
  • website/src/utils/modules.ts and website/src/utils/weekText.ts currently depend on utils/react.tsx
• Remove side effects from reducers before extraction:
  • reducers/theme.ts and reducers/settings.ts call Matomo tracking; move tracking to middleware/effects.

Implementation plan (incremental)

1. Extract @nusmods/timetable-core with tests migrated first.
2. Extract @nusmods/nus-data-client and @nusmods/route-schema.
3. Extract @nusmods/planner-core.
4. Replace imports in website with package imports.
5. Start Next.js app migration with extracted modules as stable dependencies.

Acceptance criteria

• New packages created under packages/ with clear public APIs.
• Existing tests for extracted logic pass in package scope.
• website consumes extracted packages (no duplicated logic).
• No framework-specific imports in extracted package entrypoints.
• Migration doc added describing dependency boundaries and ownership.

Out of scope

• Full React component rewrite
• Styling system migration
• Serverless deployment replatforming