features file selection and loading

File selection and loading

Active contributors: Douwe de Vries

Purpose

File loading lets users choose two local CSV files, parse them safely, detect available columns, and prepare a session for mapping. It works through browser multipart uploads and desktop raw IPC byte uploads.

Directory layout

frontend/src/components/FileSelector.tsx
frontend/src/components/app/FileSelectionStep.tsx
frontend/src/hooks/useWorkflowComparisonActions.ts
frontend/src/services/tauri.ts
src/backend/workflow.rs
src/data/csv_loader.rs

Key abstractions

Name	File	Description
FileSelectionStep	frontend/src/components/app/FileSelectionStep.tsx	Step 1 UI for File A, File B, and loading snapshots.
loadFile	frontend/src/services/tauri.ts	Browser/Tauri file upload abstraction.
CsvLoadSource	src/backend/workflow.rs	Backend input enum for file paths or bytes.
LoadedCsv	src/backend/workflow.rs	Parsed CSV plus column metadata and response payload.
load_csv_from_bytes	src/data/csv_loader.rs	CSV parsing entry point for uploaded bytes.

How it works

graph TD
    Select[User chooses CSV] --> Service[loadFile]
    Service -->|browser| Multipart[HTTP multipart]
    Service -->|desktop| RawIPC[Tauri raw IPC bytes]
    Multipart --> Workflow[load_csv_workflow]
    RawIPC --> Workflow
    Workflow --> Parser[src/data/csv_loader.rs]
    Workflow --> Virtual[src/data/json_fields.rs]
    Workflow --> Session[apply_loaded_csv_for_session]

Loading

Loading either file advances data_revision, stores CSV data and column metadata, clears stale comparison results, and refreshes suggested mappings when both files are present.

Integration points

The frontend stores headers, virtualHeaders, columns, and rowCount in AppState through frontend/src/hooks/useComparisonWorkflow.reducer.ts. The backend response is created by src/presentation/responses.rs.

Entry points for modification

Change file constraints in src/backend/workflow.rs and frontend/src/services/contracts.ts. Change parsing behavior in src/data/csv_loader.rs. Change the selection UI in frontend/src/components/FileSelector.tsx or frontend/src/components/app/FileSelectionStep.tsx.

Key source files

File	Purpose
frontend/src/components/FileSelector.tsx	CSV picker UI.
frontend/src/hooks/useWorkflowComparisonActions.ts	File load action and stale-response guard.
frontend/src/services/tauri.ts	Upload transport abstraction.
src/backend/workflow.rs	File workflow and session application.
src/data/csv_loader.rs	CSV decode and parse logic.