kandev/docs/plans/native-code-review/task-02-djb2-and-diff-collection.md

id, title, status, wave, depends_on, plan, spec

id	title	status	wave	depends_on	plan	spec
02-djb2-and-diff-collection	Go djb2 hash and task changed-file collection	done	1		plan.md	../../specs/agents/requirements/native-code-review.md

Task 02: Go djb2 hash and task changed-file collection

Give the backend the two primitives a review run needs: the frontend-compatible diff hash, and the task's changed-file set.

Inputs

• Spec Data model (file_diff_hash must match apps/web/lib/utils/hash.ts).
• apps/web/components/review/review-dialog.tsx buildAllFiles — the dedup/priority contract the backend must mirror (uncommitted wins over committed).
• apps/backend/internal/agent/handlers/git_handlers.go computeCumulativeDiff — how to reach agentctl for a session's diff.
• apps/web/components/review/types.ts normalizeDiffContent, sanitizeReviewRepositoryName.

Work

1. internal/utility/hash/djb2.go — DJB2(s string) string. Iterate UTF-16 code units to match String.prototype.charCodeAt; accumulate in int32 with wraparound; emit strconv.FormatUint(uint64(uint32(h)), 16).
2. internal/review/diff.go (new package internal/review):
   • type ChangedFile struct { RepositoryID, RepositoryName, Path, Status, Diff, DiffHash string; Additions, Deletions int }
   • type ChangeSource interface { GitStatus(ctx, sessionID) (*agentctl.GitStatusResult, error); CumulativeDiff(ctx, sessionID) (*process.CumulativeDiffResult, error) } — satisfied by an adapter over the existing execution lookup so the runner is testable with a fake.
   • CollectChanges(ctx, src, sessionID, repositoryID string) ([]ChangedFile, error) — merge uncommitted then committed, keyed by repositoryName + "\x00" + path, uncommitted winning; normalize the diff the same way the frontend does before hashing; filter to repositoryID when non-empty; skip entries with an empty diff.

Acceptance

• DJB2 agrees with djb2Hash on the shared fixture set (ASCII, multi-byte UTF-8, empty string, a realistic diff body).
• CollectChanges returns uncommitted content for a path present in both sources, and scopes correctly for a multi-repository payload.

Verification

cd apps/backend && go test ./internal/utility/hash/... ./internal/review/...
cd apps/web && pnpm vitest run lib/utils/hash.test.ts

Files likely touched

internal/utility/hash/{djb2.go,djb2_test.go}, internal/review/{diff.go,diff_test.go}, apps/web/lib/utils/hash.test.ts (add the shared fixtures).

Output contract

Summary, files changed, tests run with results, blockers, risks, status: done, plan checkbox.