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ln-721-frontend-restructure

Type: L3 Worker Category: 7XX Project Bootstrap Parent: ln-720-structure-migrator

Frontend structure worker with two modes: SCAFFOLD (generate minimal React project from template) or RESTRUCTURE (migrate monolith to component-based architecture).

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Mode Selection

Mode	When	Input	Output
SCAFFOLD	CREATE pipeline — no existing frontend	Target stack config from ln-720	Minimal React + Vite project (~7 files)
RESTRUCTURE	TRANSFORM pipeline — existing frontend found	Monolithic React source	Component-based architecture

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Purpose & Scope

Aspect	Description
Input	Target stack config (SCAFFOLD) or monolithic React source (RESTRUCTURE)
Output	Minimal project (SCAFFOLD) or component-based architecture (RESTRUCTURE)
Framework	React + TypeScript + Vite

Scope boundaries:

• SCAFFOLD: generates minimal starter files, no business logic
• RESTRUCTURE: restructures existing code, does not add new functionality
• Works with React + TypeScript projects
• Applies transformation rules from reference files

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Workflow

SCAFFOLD Mode (CREATE pipeline)

Phase	Name	Actions	Output
S1	Generate	Create minimal React + Vite + TypeScript project files	~7 starter files
S2	Verify	Check file structure, validate configs	Valid project skeleton

RESTRUCTURE Mode (TRANSFORM pipeline)

Phase	Name	Actions	Output
1	Analyze	Scan source, detect component types, measure complexity	File inventory, complexity metrics
2	Plan	Apply split thresholds, calculate file moves, detect conflicts	Migration plan
3	Execute	Create folders, extract content, update imports	Restructured files
4	Verify	Run build, check imports, validate structure	Build success report

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SCAFFOLD Mode Phases

Phase S1: Generate Starter Files

Create minimal React + Vite + TypeScript project.

File	Purpose
package.json	Dependencies: react, react-dom, typescript, vite, @vitejs/plugin-react
vite.config.ts	Vite config with React plugin, port, proxy settings
tsconfig.json	Strict TypeScript config with path aliases
index.html	Entry HTML with root div
src/main.tsx	React entry point with StrictMode
src/App.tsx	Root App component with router placeholder
src/index.css	Base styles (reset, variables, layout)

Phase S2: Verify Scaffold

Check	Method	Expected
All files created	File existence check	7 files present
package.json valid	JSON parse	No syntax errors
tsconfig.json valid	JSON parse	No syntax errors
No hardcoded values	Content scan	Project name from config, not hardcoded

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RESTRUCTURE Mode Phases

Phase 1: Analyze

Scan current frontend structure and classify components.

Step	Action	Reference
1.1	Scan all .tsx and .ts files in source	—
1.2	Measure file complexity (lines, hooks, types)	transformation_rules.md
1.3	Classify components by category	component_patterns.md
1.4	Build import dependency graph	import_strategy.md

Output: Component inventory with classifications and metrics.

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Phase 2: Plan

Generate migration plan based on analysis.

Step	Action	Reference
2.1	Apply split thresholds to identify files to restructure	transformation_rules.md
2.2	Calculate target paths for each file	react_folder_structure.md
2.3	Identify import updates needed	import_strategy.md
2.4	Detect potential conflicts (name collisions, circular deps)	—

Output: Migration plan with Before/After mapping.

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Phase 3: Execute

Apply transformations in correct order.

Step	Action	Notes
3.1	Create directory structure	All target folders
3.2	Extract types to types.ts	Types have no dependencies
3.3	Extract constants to constants.ts	Constants depend only on types
3.4	Extract hooks to hooks.ts	Hooks depend on types, constants
3.5	Extract sub-components	Components use all above
3.6	Create barrel exports (index.ts)	For clean imports
3.7	Update all import paths	Fix references

Order is critical: Execute in sequence to avoid broken imports.

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Phase 4: Verify

Validate restructured project.

Check	Command	Expected
TypeScript compilation	npx tsc --noEmit	No errors
Build	npm run build	Success
No orphan files	Manual check	Source location empty
Imports resolve	Build success	No module not found errors

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Transformation Summary

Transformation	Before State	After State
Component Split	Single file >300 lines	Feature folder with co-located files
Type Extraction	Inline interfaces	Separate types.ts
Constant Extraction	Inline magic values	Separate constants.ts
Hook Extraction	Inline useState/useEffect	Separate hooks.ts or shared hooks
UI Component Move	Scattered in features	Centralized in components/ui/
Layout Component Move	Mixed with features	Centralized in components/layout/

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Critical Rules

• Mode Awareness: SCAFFOLD creates from template; RESTRUCTURE transforms existing — never mix
• Single Responsibility: Handle only frontend structure, no backend changes
• Idempotent: Can re-run without duplicate files or corruption
• Build Verification: Must verify build passes after changes (RESTRUCTURE: npm run build)
• Preserve Functionality: No behavioral changes, only structural (RESTRUCTURE mode)
• Backup Strategy: Do not delete source files until verification passes (RESTRUCTURE mode)
• Import Consistency: Use path aliases for shared, relative for co-located

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Definition of Done

SCAFFOLD mode:

• All 7 starter files generated
• package.json and tsconfig.json valid
• No hardcoded project names (uses config values)

RESTRUCTURE mode:

• All source files analyzed and classified
• Migration plan generated with Before/After mapping
• Directory structure created per template
• All extractions completed (types, constants, hooks, components)
• Import paths updated throughout project
• npm run build passes successfully
• No orphan imports or missing files
• Barrel exports created for shared folders

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Risk Mitigation

Risk	Detection	Mitigation
Build failure after restructure	npm run build fails	Rollback: restore from source, investigate specific error
Missing imports	Module not found errors	Scan all imports before/after, update missed paths
Circular dependencies	Build warning or runtime error	Analyze dependency graph, break cycles by extracting shared code
Lost functionality	Tests fail or UI broken	Run existing tests before/after transformation
Name collisions	Duplicate export names	Rename with feature prefix before moving

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Reference Files

File	Purpose
references/transformation_rules.md	Split thresholds, extraction rules, transformation order
references/component_patterns.md	Component classification by category
references/import_strategy.md	Import update rules, path aliases, barrel exports
references/react_folder_structure.md	Target directory structure template

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Version: 3.0.0 Last Updated: 2026-02-07