OCR/openspec/specs/result-export/spec.md

# result-export Specification

## Purpose
TBD - created by archiving change fix-v2-api-ui-issues. Update Purpose after archive.
## Requirements
### Requirement: Export Interface

The Export interface in TaskDetailPage SHALL provide streamlined download options focusing on PDF formats.

#### Scenario: Download options for completed tasks
- **WHEN** viewing a completed task in TaskDetailPage
- **THEN** the download section SHALL display only two buttons: "版面 PDF" and "流式 PDF"
- **AND** JSON, UnifiedDocument, and Markdown download buttons SHALL NOT be displayed
- **AND** the download grid SHALL use a 2-column layout

#### Scenario: Translation download options
- **WHEN** viewing completed translations in TaskDetailPage
- **THEN** each translation item SHALL display only a "流式 PDF" download button
- **AND** translation JSON download button SHALL NOT be displayed
- **AND** Layout PDF option for translations SHALL NOT be displayed
- **AND** delete translation button SHALL remain available

#### Scenario: Backend API remains unchanged
- **WHEN** external clients call download endpoints directly
- **THEN** JSON, Markdown, and UnifiedDocument endpoints SHALL still function
- **AND** translated Layout PDF endpoint SHALL still function
- **AND** no backend changes are required for this frontend simplification

### Requirement: Multi-Task Export Selection
The Export page SHALL allow users to select and export multiple tasks.

#### Scenario: Select multiple tasks for export
- **WHEN** Export page loads
- **THEN** page SHALL display list of user's completed tasks
- **AND** page SHALL provide checkboxes to select multiple tasks
- **AND** page SHALL NOT require batch ID from upload store (legacy V1 behavior)

#### Scenario: Export selected tasks
- **WHEN** user selects multiple tasks and clicks export
- **THEN** system SHALL download each selected task's results in chosen format
- **AND** downloaded files SHALL be named distinctly (e.g., `{task_id}_result.{ext}`)
- **AND** system MAY provide option to download as ZIP archive for multiple files

### Requirement: Export Configuration Persistence
Export settings (format, thresholds, templates) SHALL apply consistently to V2 task downloads.

#### Scenario: Apply confidence threshold to export
- **WHEN** user sets confidence threshold to 0.7 and exports
- **THEN** downloaded results SHALL only include OCR text with confidence >= 0.7
- **AND** threshold SHALL apply via V2 download endpoint query parameters

#### Scenario: Apply CSS template to PDF export
- **WHEN** user selects CSS template for PDF format
- **THEN** downloaded PDF SHALL use selected styling
- **AND** template SHALL be passed to V2 `/tasks/{id}/download/pdf` endpoint

### Requirement: Enhanced PDF Export with Layout Preservation

The PDF export SHALL accurately preserve document layout from both OCR and direct extraction tracks with correct coordinate transformation and multi-page support. For Direct Track, a background image rendering approach SHALL be used for visual fidelity.

#### Scenario: Export PDF from direct extraction track
- **WHEN** exporting PDF from a direct-extraction processed document
- **THEN** the system SHALL render source PDF pages as full-page background images at 2x resolution
- **AND** overlay invisible text elements using PDF Text Rendering Mode 3
- **AND** text SHALL remain selectable and searchable despite being invisible
- **AND** visual output SHALL match source document exactly

#### Scenario: Export PDF from OCR track with full structure
- **WHEN** exporting PDF from OCR-processed document
- **THEN** the PDF SHALL use all 23 PP-StructureV3 element types
- **AND** render tables with proper cell boundaries
- **AND** maintain reading order from parsing_res_list

#### Scenario: Handle coordinate transformations correctly
- **WHEN** generating PDF from UnifiedDocument
- **THEN** system SHALL use explicit page dimensions from OCR results (not inferred from bounding boxes)
- **AND** correctly transform Y-axis coordinates from top-left (OCR) to bottom-left (PDF/ReportLab) origin
- **AND** prevent vertical flipping or position misalignment errors

#### Scenario: Direct Track PDF file size increase
- **WHEN** generating Layout PDF for Direct Track documents
- **THEN** the system SHALL accept increased file size due to embedded page images
- **AND** approximately 1-2 MB per page at 2x resolution is expected
- **AND** this trade-off is accepted for improved visual fidelity

#### Scenario: Chart elements excluded from text layer
- **WHEN** generating Layout PDF containing charts
- **THEN** the system SHALL NOT include chart-internal text in the invisible text layer
- **AND** chart visuals SHALL be preserved in the background image
- **AND** chart text SHALL NOT be available for text selection or translation

### Requirement: Structure Data Export
The system SHALL provide export formats that preserve document structure for downstream processing.

#### Scenario: Export structured JSON with hierarchy
- **WHEN** user selects structured JSON format
- **THEN** export SHALL include element hierarchy and relationships
- **AND** preserve parent-child relationships (sections, lists)
- **AND** include style and formatting information

#### Scenario: Export for translation preparation
- **WHEN** user exports with translation_ready=true parameter
- **THEN** export SHALL include translatable text segments
- **AND** maintain coordinate mappings for each segment
- **AND** mark non-translatable regions

#### Scenario: Export with layout analysis
- **WHEN** user requests layout analysis export
- **THEN** system SHALL include reading order indices
- **AND** identify layout regions (header, body, footer, sidebar)
- **AND** provide confidence scores for layout detection

### Requirement: Translation Result JSON Export

The system SHALL support exporting translation results as independent JSON files following a defined schema.

#### Scenario: Export translation result JSON
- **WHEN** translation completes for a document
- **THEN** system SHALL save translation to `{filename}_translated_{lang}.json`
- **AND** file SHALL be stored alongside original `{filename}_result.json`
- **AND** original result file SHALL remain unchanged

#### Scenario: Translation JSON schema compliance
- **WHEN** translation result is saved
- **THEN** JSON SHALL include schema_version field ("1.0.0")
- **AND** SHALL include source_document reference
- **AND** SHALL include source_lang and target_lang
- **AND** SHALL include provider identifier (e.g., "dify")
- **AND** SHALL include translated_at timestamp
- **AND** SHALL include translations dict mapping element_id to translated content

#### Scenario: Translation statistics in export
- **WHEN** translation result is saved
- **THEN** JSON SHALL include statistics object with:
  - total_elements: count of all elements in document
  - translated_elements: count of successfully translated elements
  - skipped_elements: count of non-translatable elements (images, charts, etc.)
  - total_characters: character count of translated text
  - processing_time_seconds: translation duration

#### Scenario: Table cell translation in export
- **WHEN** document contains tables
- **THEN** translation JSON SHALL represent table translations as:
  ```json
  {
    "table_1_0": {
      "cells": [
        {"row": 0, "col": 0, "content": "Translated cell text"},
        {"row": 0, "col": 1, "content": "Another cell"}
      ]
    }
  }
  ```
- **AND** row/col positions SHALL match original table structure

#### Scenario: Download translation result via API
- **WHEN** GET request to `/api/v2/translate/{task_id}/result?lang={lang}`
- **THEN** system SHALL return translation JSON content
- **AND** Content-Type SHALL be application/json
- **AND** response SHALL include appropriate cache headers

#### Scenario: List available translations
- **WHEN** GET request to `/api/v2/tasks/{task_id}/translations`
- **THEN** system SHALL return list of available translation languages
- **AND** include translation metadata (translated_at, provider, statistics)

### Requirement: Translated PDF Export API

The system SHALL expose an API endpoint for downloading translated documents as PDF files.

#### Scenario: Download translated PDF via API
- **GIVEN** a task with completed translation to English
- **WHEN** POST request to `/api/v2/translate/{task_id}/pdf?lang=en`
- **THEN** system returns PDF file with translated content
- **AND** Content-Type is `application/pdf`
- **AND** Content-Disposition suggests filename like `{task_id}_translated_en.pdf`

#### Scenario: Download translated PDF with layout preservation
- **WHEN** user downloads translated PDF
- **THEN** the PDF maintains original document layout
- **AND** text positions match original document coordinates
- **AND** images and tables appear at original positions

#### Scenario: Invalid language parameter
- **GIVEN** a task with translation only to English
- **WHEN** user requests PDF with `lang=ja` (Japanese)
- **THEN** system returns 404 Not Found
- **AND** response includes available languages in error message

#### Scenario: Task not found
- **GIVEN** non-existent task_id
- **WHEN** user requests translated PDF
- **THEN** system returns 404 Not Found

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### Requirement: Frontend Translated PDF Download

The frontend SHALL provide UI controls for downloading translated PDFs.

#### Scenario: Show download button when translation complete
- **GIVEN** a task with translation status "completed"
- **WHEN** user views TaskDetailPage
- **THEN** page displays "Download Translated PDF" button
- **AND** button shows target language (e.g., "Download Translated PDF (English)")

#### Scenario: Hide download button when no translation
- **GIVEN** a task without any completed translations
- **WHEN** user views TaskDetailPage
- **THEN** "Download Translated PDF" button is not shown

#### Scenario: Download progress indication
- **GIVEN** user clicks "Download Translated PDF" button
- **WHEN** PDF generation is in progress
- **THEN** button shows loading state
- **AND** prevents double-click
- **WHEN** download completes
- **THEN** browser downloads PDF file
- **AND** button returns to normal state