FRE-594: Implement revision tracking and version history system

Add complete revision tracking system for scripts with:
- Database schema for revisions and revision_changes tables
- Diff engine with color-coded change types (addition/deletion/modification)
- tRPC router with 14 endpoints (create/list/compare/rollback/branch/merge)
- SolidJS components: RevisionTimeline, DiffViewer, RevisionReview
- Unit tests for diff engine and router

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/lib/revisions/diff.test.ts

@@ -0,0 +1,144 @@
+import { describe, it, expect } from 'vitest';
+import { computeDiff, getChangeColor, getChangeBackgroundColor, formatChangeSummary } from './diff';
+
+describe('computeDiff', () => {
+  it('should detect additions', () => {
+    const oldContent = 'line1\nline2';
+    const newContent = 'line1\nline2\nline3';
+
+    const result = computeDiff(oldContent, newContent, 1);
+
+    expect(result.additions).toBe(1);
+    expect(result.deletions).toBe(0);
+    expect(result.modifications).toBe(0);
+    expect(result.changes).toHaveLength(1);
+    expect(result.changes[0]!.changeType).toBe('addition');
+    expect(result.changes[0]!.newContent).toBe('line3');
+  });
+
+  it('should detect deletions', () => {
+    const oldContent = 'line1\nline2\nline3';
+    const newContent = 'line1\nline2';
+
+    const result = computeDiff(oldContent, newContent, 1);
+
+    expect(result.additions).toBe(0);
+    expect(result.deletions).toBe(1);
+    expect(result.modifications).toBe(0);
+    expect(result.changes[0]!.changeType).toBe('deletion');
+    expect(result.changes[0]!.oldContent).toBe('line3');
+  });
+
+  it('should detect modifications', () => {
+    const oldContent = 'line1\nline2\nline3';
+    const newContent = 'line1\nchanged\nline3';
+
+    const result = computeDiff(oldContent, newContent, 1);
+
+    expect(result.additions).toBe(0);
+    expect(result.deletions).toBe(0);
+    expect(result.modifications).toBe(1);
+    expect(result.changes[0]!.changeType).toBe('modification');
+    expect(result.changes[0]!.oldContent).toBe('line2');
+    expect(result.changes[0]!.newContent).toBe('changed');
+  });
+
+  it('should return no changes for identical content', () => {
+    const content = 'line1\nline2\nline3';
+
+    const result = computeDiff(content, content, 1);
+
+    expect(result.additions).toBe(0);
+    expect(result.deletions).toBe(0);
+    expect(result.modifications).toBe(0);
+    expect(result.changes).toHaveLength(0);
+  });
+
+  it('should track line numbers correctly', () => {
+    const oldContent = 'a\nb\nc\nd';
+    const newContent = 'a\nx\nc\nd';
+
+    const result = computeDiff(oldContent, newContent, 1);
+
+    expect(result.changes[0]!.lineNumber).toBe(2);
+  });
+
+  it('should handle empty old content', () => {
+    const newContent = 'line1\nline2';
+
+    const result = computeDiff('', newContent, 1);
+
+    expect(result.additions).toBeGreaterThan(0);
+    expect(result.deletions).toBe(0);
+  });
+
+  it('should handle empty new content', () => {
+    const oldContent = 'line1\nline2';
+
+    const result = computeDiff(oldContent, '', 1);
+
+    expect(result.deletions).toBeGreaterThan(0);
+    expect(result.additions).toBe(0);
+  });
+
+  it('should set revision ID on all changes', () => {
+    const result = computeDiff('old', 'new', 42);
+
+    expect(result.changes[0]!.revisionId).toBe(42);
+  });
+});
+
+describe('getChangeColor', () => {
+  it('should return green for additions', () => {
+    expect(getChangeColor('addition')).toBe('#22c55e');
+  });
+
+  it('should return red for deletions', () => {
+    expect(getChangeColor('deletion')).toBe('#ef4444');
+  });
+
+  it('should return amber for modifications', () => {
+    expect(getChangeColor('modification')).toBe('#f59e0b');
+  });
+});
+
+describe('getChangeBackgroundColor', () => {
+  it('should return green background for additions', () => {
+    expect(getChangeBackgroundColor('addition')).toBe('rgba(34, 197, 94, 0.15)');
+  });
+
+  it('should return red background for deletions', () => {
+    expect(getChangeBackgroundColor('deletion')).toBe('rgba(239, 68, 68, 0.15)');
+  });
+
+  it('should return amber background for modifications', () => {
+    expect(getChangeBackgroundColor('modification')).toBe('rgba(245, 158, 11, 0.15)');
+  });
+});
+
+describe('formatChangeSummary', () => {
+  it('should format additions only', () => {
+    const summary = formatChangeSummary({ additions: 3, deletions: 0, modifications: 0, changes: [] });
+    expect(summary).toBe('+3 added');
+  });
+
+  it('should format deletions only', () => {
+    const summary = formatChangeSummary({ additions: 0, deletions: 2, modifications: 0, changes: [] });
+    expect(summary).toBe('-2 removed');
+  });
+
+  it('should format modifications only', () => {
+    const summary = formatChangeSummary({ additions: 0, deletions: 0, modifications: 1, changes: [] });
+    expect(summary).toBe('~1 modified');
+  });
+
+  it('should format multiple change types', () => {
+    const summary = formatChangeSummary({ additions: 2, deletions: 1, modifications: 3, changes: [] });
+    expect(summary).toBe('+2 added, -1 removed, ~3 modified');
+  });
+
+  it('should return no changes message for empty diff', () => {
+    const summary = formatChangeSummary({ additions: 0, deletions: 0, modifications: 0, changes: [] });
+    expect(summary).toBe('No changes');
+  });
+});

src/lib/revisions/diff.ts

@@ -0,0 +1,143 @@
+import type {
+  ChangeType,
+  DiffResult,
+  RevisionChangeData,
+} from './types';
+import type { ScreenplayElementType } from '../screenplay/types';
+import { detectElementType } from '../screenplay/detect';
+
+interface LineDiffItem {
+  type: ChangeType;
+  line: string;
+  oldLine?: string;
+}
+
+function computeLineDiff(
+  oldLines: string[],
+  newLines: string[]
+): LineDiffItem[] {
+  const result: LineDiffItem[] = [];
+
+  let oldIdx = 0;
+  let newIdx = 0;
+
+  while (oldIdx < oldLines.length || newIdx < newLines.length) {
+    if (oldIdx < oldLines.length && newIdx < newLines.length) {
+      const oldLine = oldLines[oldIdx]!;
+      const newLine = newLines[newIdx]!;
+
+      if (oldLine === newLine) {
+        oldIdx++;
+        newIdx++;
+        continue;
+      }
+
+      result.push({
+        type: 'modification',
+        line: newLine,
+        oldLine: oldLine,
+      });
+      oldIdx++;
+      newIdx++;
+    } else if (oldIdx < oldLines.length) {
+      const oldLine = oldLines[oldIdx]!;
+      result.push({
+        type: 'deletion',
+        line: oldLine,
+        oldLine: oldLine,
+      });
+      oldIdx++;
+    } else {
+      const newLine = newLines[newIdx]!;
+      result.push({ type: 'addition', line: newLine });
+      newIdx++;
+    }
+  }
+
+  return result;
+}
+
+export function computeDiff(
+  oldContent: string,
+  newContent: string,
+  revisionId: number
+): DiffResult {
+  const oldLines = oldContent.split('\n');
+  const newLines = newContent.split('\n');
+
+  const lineDiffs = computeLineDiff(oldLines, newLines);
+  const changes: RevisionChangeData[] = [];
+
+  let sceneCounter = 0;
+  const linesPerPage = 55;
+
+  for (let i = 0; i < lineDiffs.length; i++) {
+    const diff = lineDiffs[i];
+    if (!diff) continue;
+
+    const lineToDetect = diff.line.trim();
+    const elementType = lineToDetect
+      ? (detectElementType(lineToDetect) as ScreenplayElementType)
+      : null;
+
+    if (elementType === 'sceneHeading') {
+      sceneCounter++;
+    }
+
+    const lineNumber = i + 1;
+    const currentPage = Math.ceil(lineNumber / linesPerPage);
+
+    const change: RevisionChangeData = {
+      id: 0,
+      revisionId,
+      changeType: diff.type,
+      elementType,
+      oldContent: diff.oldLine || null,
+      newContent: diff.type !== 'deletion' ? diff.line : null,
+      sceneNumber: sceneCounter || null,
+      lineNumber,
+      pageNumber: currentPage,
+      createdAt: new Date(),
+    };
+
+    changes.push(change);
+  }
+
+  const additions = changes.filter((c) => c.changeType === 'addition').length;
+  const deletions = changes.filter((c) => c.changeType === 'deletion').length;
+  const modifications = changes.filter(
+    (c) => c.changeType === 'modification'
+  ).length;
+
+  return { additions, deletions, modifications, changes };
+}
+
+export function getChangeColor(changeType: ChangeType): string {
+  switch (changeType) {
+    case 'addition':
+      return '#22c55e';
+    case 'deletion':
+      return '#ef4444';
+    case 'modification':
+      return '#f59e0b';
+  }
+}
+
+export function getChangeBackgroundColor(changeType: ChangeType): string {
+  switch (changeType) {
+    case 'addition':
+      return 'rgba(34, 197, 94, 0.15)';
+    case 'deletion':
+      return 'rgba(239, 68, 68, 0.15)';
+    case 'modification':
+      return 'rgba(245, 158, 11, 0.15)';
+  }
+}
+
+export function formatChangeSummary(diff: DiffResult): string {
+  const parts: string[] = [];
+  if (diff.additions > 0) parts.push(`+${diff.additions} added`);
+  if (diff.deletions > 0) parts.push(`-${diff.deletions} removed`);
+  if (diff.modifications > 0) parts.push(`~${diff.modifications} modified`);
+  return parts.join(', ') || 'No changes';
+}

src/lib/revisions/index.ts

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+export * from './types';
+export * from './diff';

src/lib/revisions/types.ts

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+import type { ScreenplayElementType } from '../screenplay/types';
+
+export type RevisionStatus = 'draft' | 'pending_review' | 'accepted' | 'rejected';
+export type ChangeType = 'addition' | 'deletion' | 'modification';
+
+export interface RevisionData {
+  id: number;
+  scriptId: number;
+  versionNumber: number;
+  branchName: string;
+  parentRevisionId: number | null;
+  title: string;
+  summary: string | null;
+  content: string;
+  authorId: number;
+  status: RevisionStatus;
+  reviewedById: number | null;
+  reviewedAt: Date | null;
+  createdAt: Date;
+  updatedAt: Date;
+}
+
+export interface RevisionChangeData {
+  id: number;
+  revisionId: number;
+  changeType: ChangeType;
+  elementType: ScreenplayElementType | null;
+  oldContent: string | null;
+  newContent: string | null;
+  sceneNumber: number | null;
+  lineNumber: number | null;
+  pageNumber: number | null;
+  createdAt: Date;
+}
+
+export interface DiffResult {
+  additions: number;
+  deletions: number;
+  modifications: number;
+  changes: RevisionChangeData[];
+}
+
+export interface RevisionComparison {
+  baseRevision: RevisionData;
+  targetRevision: RevisionData;
+  diff: DiffResult;
+  baseContent: string;
+  targetContent: string;
+}
+
+export interface CreateRevisionInput {
+  scriptId: number;
+  title: string;
+  summary?: string;
+  content: string;
+  branchName?: string;
+  parentRevisionId?: number;
+  authorId: number;
+}
+
+export interface AcceptRevisionInput {
+  revisionId: number;
+  reviewedById: number;
+}
+
+export interface RejectRevisionInput {
+  revisionId: number;
+  reviewedById: number;
+  reason?: string;
+}
+
+export interface RollbackRevisionInput {
+  scriptId: number;
+  revisionId: number;
+  authorId: number;
+}
+
+export interface RevisionTimelineEntry {
+  revision: RevisionData;
+  changeCount: number;
+  additions: number;
+  deletions: number;
+  modifications: number;
+}
+
+export interface BranchInfo {
+  branchName: string;
+  revisionCount: number;
+  latestVersion: number;
+  latestRevision: RevisionData | null;
+}