# File Manager

## Objective

Give people a familiar place to browse, rename, move, and delete their files.

A folder-based file browser with multi-select, rename, move, copy, delete, and search across the user's stored files.

## Before You Begin

This feature is being added to an application that already exists and already
works. Do not scaffold a new project, and do not assume a blank slate.

Inspect the codebase first and establish:

- The existing application structure and where code of this kind already lives.
- The framework and version in use.
- The existing design system — colours, spacing, typography, and component conventions.
- Existing UI components you can reuse instead of writing new ones.
- The existing database structure, if this feature needs to persist anything.
- The existing authentication and authorization system, if this feature is user-scoped.
- Dependencies already installed, so you don't add a library that duplicates one.
- The existing test setup and conventions.

Only start writing code once you understand the above. If the application
already implements part of this feature, extend it rather than replacing it.

## Implementation Instructions

1. Build on the files the app already stores. Reuse the existing File Upload for adding files and the existing Secure File Downloads for reading them back, rather than creating a second storage path with its own rules.
2. Ship the operations people expect from a file browser and nothing more: navigate folders, create a folder, rename, move, copy, delete, and search by name. Sharing, versioning, and permissions editing are separate features that should be deferred rather than half-built.
3. Make every destructive action recoverable. Deleted items go to a trash with a retention window and a restore, because a file browser without an undo will eventually lose someone's work.
4. Show a breadcrumb of the current path and keep it in the URL, so a folder can be linked, bookmarked, and returned to with the back button.
5. Do not treat folders as a display convenience layered over a flat bucket. Model the hierarchy properly, or move, rename, and delete will each need their own inconsistent special cases.

## UI and UX Requirements

Match the application's existing design system exactly. Reuse its components,
spacing, and typography. This feature should look like it was always there.

## Responsive Requirements

Works on mobile, tablet, and desktop. Touch targets are large enough to hit on a
phone, and nothing overflows horizontally at 320px.

## Accessibility Requirements

- Fully keyboard navigable.
- Correct semantic elements and ARIA roles.
- Visible focus states.
- Meets WCAG AA contrast.
- Dynamic changes are announced to screen readers.
- Respects prefers-reduced-motion.

## Edge Cases

- Moving or copying into a folder that already holds a file of that name must ask: keep both, replace, or cancel. Silently overwriting is data loss the user never sees happen.
- Multi-select and drag targets designed for a mouse become unusable on touch. Provide an explicit selection mode and a move-to-folder action that does not require dragging.
- A folder with thousands of items must paginate or virtualize, and search must run server-side. Loading a whole folder to filter it in the browser will hang the tab.
- Permissions have to be enforced on every operation, not just on the listing. A user who cannot see a file must not be able to rename, move, or delete it by knowing its identifier.
- A batch move that fails partway must leave a coherent result. Report which items moved and which did not, and never leave a file recorded in two places or in none.
- Names arrive with path separators, leading dots, trailing spaces, control characters, and lengths no filesystem accepts. Normalise and validate on the server, not only in the input field.
- Moving a folder moves everything under it, which can be a very large operation. Run it in the background with progress, and block moving a folder into its own descendant.
- Two people or two tabs acting on the same folder will collide. Refresh the listing after each operation and report clearly when a target no longer exists.

## Testing

Exercise the feature end to end in the running application. Cover every edge case
above, then run the existing test suite and confirm nothing regressed.

## Acceptance Criteria

- [ ] Users can browse folders, and create, rename, move, copy, and delete files and folders.
- [ ] Name collisions prompt for a choice and never overwrite silently.
- [ ] Selection, move, and delete are fully usable on a touch screen without dragging.
- [ ] Folders with thousands of items load and search without freezing.
- [ ] Every operation authorises against the acting user, not just the listing.
- [ ] A partially failed batch reports exactly what succeeded and leaves no orphaned records.
- [ ] Deleted items are recoverable from trash for a defined window and the current folder is reflected in the URL.
- [ ] The feature matches the existing design system.
- [ ] No existing functionality is broken.

## Adaptation Rules

- Match the existing design system. Do not introduce a new colour palette,
  spacing scale, or component library.
- Reuse existing components and utilities wherever they fit.
- Follow the naming, file layout, and code style already present.
- Do not upgrade, replace, or remove existing dependencies to make this
  feature fit. Adapt the feature to the app, not the app to the feature.
- Do not break existing functionality. If a change is genuinely required in
  existing code, make the smallest one that works and say so.
- If something in these instructions conflicts with how the application is
  built, follow the application and explain the deviation.

## Final Verification

Before you report the work as done:

1. Re-read the acceptance criteria above and check each one against what you
   actually built.
2. Run the application and exercise the feature end to end.
3. Run the existing test suite and confirm you have broken nothing.
4. Check the feature on mobile, tablet, and desktop widths.
5. Check keyboard navigation and focus handling.
6. Summarize what changed: files added, files modified, and anything you
   deliberately did differently because of how this application is built.

If any acceptance criterion is unmet, fix it before reporting completion.