shared: build a context-card diffing utility and validation layer

[ShantKhatri]

Summary

Product doc section 4.5 describes 'Context Cards' — multiple curated cards per user (Professional, Hackathon, Community). Currently the cards.ts route handles creation, but there is no shared utility to validate card platform selections or diff two versions of a card.

Context

This utility lives in packages/shared so it can be used by both the web and mobile clients. The backend apps/backend/src/routes/cards.ts creates cards, but the validation is minimal.

Tasks

• in packages/shared/src/cards.ts (new file), create:
  • validateCardPlatforms(platforms: string[]): ValidationResult — checks that all platform IDs in a card are in PLATFORMS, max 10 platforms, no duplicates.
  • diffCardPlatforms(oldCard: string[], newCard: string[]): { added: string[], removed: string[], unchanged: string[] } — pure diff utility.
  • type CardValidationResult = { valid: boolean; errors: string[] }.
• export these from packages/shared/src/index.ts.
• write comprehensive unit tests in packages/shared/src/__tests__/cards.test.ts covering edge cases: empty array, all-invalid platforms, duplicate platforms, max exceeded.
• update the backend route apps/backend/src/routes/cards.ts to use validateCardPlatforms for input validation instead of ad-hoc checks.

Acceptance Criteria

• shared utilities are typed, exported, and tested.
• backend uses the shared validator.
• pnpm -r test passes.

Difficulty

medium — cross-package logic, requires careful TypeScript type design and edge case coverage.

[kundurukarthik15-gif]

Hello @ShantKhatri, I’m a GSSoC 2026 contributor and interested in working on this. Kindly assign it to me.

[Midoriya-w]

Hey @ShantKhatri! I'd love to work on this under GSSoC 2026.
My planned approach:
packages/shared/src/cards.ts

validateCardPlatforms(platforms: string[]): CardValidationResult checks all IDs exist in PLATFORMS, max 10 platforms, no duplicates, returns { valid: boolean; errors: string[] }
diffCardPlatforms(oldCard: string[], newCard: string[]): { added: string[], removed: string[], unchanged: string[] } pure set-based diff using Set for O(n) performance

packages/shared/src/tests/cards.test.ts

Edge cases: empty array, all-invalid platforms, duplicates, exactly 10 (pass) vs 11 (fail), mixed valid/invalid

apps/backend/src/routes/cards.ts

Replace ad-hoc validation with validateCardPlatforms, return structured errors on failure

Can I get assigned?

[Midoriya-w]

Comment on issue #31: Hey @ShantKhatri! Opened clean PR (#167) with only the shared utility files validateCardPlatforms, diffCardPlatforms, tests, and index export. Ready for review!

[kundurukarthik15-gif]

Hello @ShantKhatri, I’m a GSSoC 2026 contributor and interested in working on this. Kindly assign it to me.