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perf(web): replace quadratic LCS with Myers diff and fix deploy workflow - #281

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williamzujkowski merged 1 commit into
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fix/deploy-and-myers-diff
Oct 6, 2026
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perf(web): replace quadratic LCS with Myers diff and fix deploy workflow#281
williamzujkowski merged 1 commit into
mainfrom
fix/deploy-and-myers-diff

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@williamzujkowski williamzujkowski commented Oct 6, 2026

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Description

This PR resolves issue #280 and fixes the GitHub Pages deployment failure in the Deploy Site workflow.

Changes

  1. Myers Diff for Legal Redline (perf(web): replace quadratic LCS diff with Myers or linear-space diff in DiffViewer #280):

    • Implemented Eugene W. Myers' (ND)$ Shortest Edit Script (SES) algorithm in apps/web/src/lib/word-diff.ts.
    • Added (\min(N, M))$ common prefix and suffix trimming before edit graph traversal.
    • Added safety cap threshold fallback ( \times M > 250,000$ or tokens $> 1,500$) to guarantee the browser main UI thread never locks on massive textual changes.
    • Refactored DiffViewer.svelte to consume computeWordDiff and WordToken from apps/web/src/lib/word-diff.ts.
    • Added vitest unit test suite covering empty inputs, word substitutions, legislative amendment texts, 50-paragraph performance benchmarks, and fallback caps.

  2. Deploy Site Workflow Monorepo Build Fix:

    • Updated .github/workflows/deploy-site.yml to build web and its workspace monorepo dependencies (@civic-source/shared, @civic-source/types) via pnpm --filter @civic-source/web... build before Astro builds.
    • Expanded workflow push trigger paths to include packages/** and scripts/** so changes to dependencies trigger site deployment.

Closes #280

@williamzujkowski
perf(web): replace quadratic LCS with Myers diff and fix deploy workflow
4070974 
- Replace O(M*N) 2D matrix LCS in DiffViewer with Myers' O(ND) algorithm in apps/web/src/lib/word-diff.ts
- Add prefix/suffix trimming and max-cells fallback cap to prevent UI locking on large statutory diffs
- Add comprehensive vitest suite in apps/web/src/__tests__/word-diff.test.ts
- Build workspace package dependencies in deploy-site workflow before web build
- Resolves #280
@williamzujkowski
williamzujkowski requested a review from a team as a code owner October 6, 2026 14:01
@williamzujkowski
williamzujkowski merged commit b85c564 into main Oct 6, 2026
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@williamzujkowski
williamzujkowski deleted the fix/deploy-and-myers-diff branch October 6, 2026 14:13
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perf(web): replace quadratic LCS diff with Myers or linear-space diff in DiffViewer

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@williamzujkowski