# meta archietecture

* [MVVM](https://docs.flutter.dev/app-architecture/guide)
  * [Data layer](https://docs.flutter.dev/app-architecture/case-study/data-layer)
    * View ⇆ ViewModel ⇆ Repository ⇆ Service
      * Model is used across.

## Package structure

The repo structure follows official [Package structure](https://docs.flutter.dev/app-architecture/case-study#package-structure). 

```
lib
├─┬─ ui
│ ├─┬─ core
│ │ ├─┬─ ui
│ │ │ └─── <shared widgets>
│ │ └─── themes
│ └─┬─ <FEATURE NAME>
│   ├─┬─ view_model
│   │ └─── <view_model class>.dart
│   └─┬─ widgets
│     ├── <feature name>_screen.dart
│     └── <other widgets>
├─┬─ domain
│ └─┬─ models
│   └─── <model name>.dart
├─┬─ data
│ ├─┬─ repositories
│ │ └─── <repository class>.dart
│ ├─┬─ services
│ │ └─── <service class>.dart
│ └─┬─ model
│   └─── <api model class>.dart
├─── config
├─── utils
├─── routing
├─── main_staging.dart
├─── main_development.dart
└─── main.dart

// The test folder contains unit and widget tests
test
├─── data
├─── domain
├─── ui
└─── utils

// The testing folder contains mocks other classes need to execute tests
testing
├─── fakes
└─── models
```

But with slight modifications.

* put each `<FEATURE NAME>/`s in `features/` sub-directory under `ui/`.
* `test/features/` contains BDD unit tests for each feature. It focuses on pure logic, therefore will not access `View` but `ViewModel` and `Model`.
* `test/widget/` contains UI widget(component) tests which focus on `View` from MVVM of each component.
* `integration_test/` for integration tests. They should be volatile to follow UI layout changes.

Some rule of thumb:
* `<object>Provider` only placed at `/lib/data/repositories/` or `/lib/data/services/` to provide data source.

## Abstraction

### terminology

* `signature asset`
  * image file of a signature, stored in the device or cloud storage
    * can drawing from canvas
* `signature card`
  * template of signature placement
  * It will include modifications such as brightness, contrast, background removal, rotation of the signature asset.
* `signature placement`
  * placed modified signature asset from signature card on a specific position on a specific page of a specific PDF document
* `document`
  * PDF document to be signed

## key dependencies

* [pdfrx](https://pub.dev/packages/pdfrx)
  * [packages/pdfrx/example/viewer/lib/main.dart](https://github.com/espresso3389/pdfrx/blob/master/packages/pdfrx/example/viewer/lib/main.dart)
  * When using pdfrx, developers should control view function e.g. zoom, scroll... by component of pdfrx e.g. `PdfViewer`, rather than introduce additional view.
    * [PdfViewer could not be scrollable when nested inside SingleChildScrollView #27](https://github.com/espresso3389/pdfrx/issues/27)
    * [How to zoom in PdfPageView #244](https://github.com/espresso3389/pdfrx/issues/244)
  * So does overlay some widgets, they should be placed using the provided overlay builder.
    * [Viewer Customization using Widget Overlay](https://pub.dev/documentation/pdfrx/latest/pdfrx/PdfViewerParams/viewerOverlayBuilder.html)
    * [Per-page Customization using Widget Overlay](https://pub.dev/documentation/pdfrx/latest/pdfrx/PdfViewerParams/pageOverlaysBuilder.html)
      * `pageOverlaysBuilder`