# Account Model Extension Implementation

## Overview

This document describes the implementation of task 1.6: Extending the Account model to support asset management enhancements for the accounting-feature-upgrade specification.

## Feature

**Feature:** accounting-feature-upgrade  
**Task:** 1.6 扩展Account模型  
**Validates:** Requirements 1.2-1.10

## Changes Made

### 1. Model Extension (backend/internal/models/models.go)

Added the following fields to the `Account` struct:

```go
// Asset management enhancements
// Feature: accounting-feature-upgrade
// Validates: Requirements 1.2-1.10
SortOrder        int        `gorm:"default:0" json:"sort_order"`                                      // Display order for account list
WarningThreshold *float64   `gorm:"type:decimal(15,2)" json:"warning_threshold,omitempty"`            // Balance warning threshold
LastSyncTime     *time.Time `json:"last_sync_time,omitempty"`                                         // Last synchronization time
AccountCode      string     `gorm:"size:50" json:"account_code,omitempty"`                            // Account identifier (e.g., Alipay, Wechat)
AccountType      string     `gorm:"size:20;default:'asset'" json:"account_type"`                      // asset or liability
```

### 2. Database Migration (backend/migrations/004_extend_account_model.sql)

Created a SQL migration file that:
- Adds all five new fields to the `accounts` table
- Adds indexes for `sort_order` and `account_type` to optimize queries
- Includes proper comments for each field
- Follows the project's migration file format

### 3. Unit Tests (backend/internal/models/account_extension_test.go)

Created comprehensive unit tests covering:

#### Test Coverage

1. **TestAccountExtension_SortOrderField** - Verifies the sort_order field works correctly
2. **TestAccountExtension_WarningThresholdField** - Tests warning threshold with and without values
3. **TestAccountExtension_LastSyncTimeField** - Tests last sync time with and without values
4. **TestAccountExtension_AccountCodeField** - Tests various account codes (Alipay, Wechat, etc.)
5. **TestAccountExtension_AccountTypeField** - Tests asset and liability account types
6. **TestAccountExtension_WarningThresholdLogic** - Tests the warning threshold logic (Validates Requirements 1.5, 1.10)
7. **TestAccountExtension_AllFieldsTogether** - Tests all fields working together
8. **TestAccountExtension_AssetVsLiability** - Tests asset vs liability distinction (Validates Requirements 1.2)

#### Test Results

All tests pass successfully:
```
PASS: TestAccountExtension_SortOrderField
PASS: TestAccountExtension_WarningThresholdField
PASS: TestAccountExtension_LastSyncTimeField
PASS: TestAccountExtension_AccountCodeField
PASS: TestAccountExtension_AccountTypeField
PASS: TestAccountExtension_WarningThresholdLogic
PASS: TestAccountExtension_AllFieldsTogether
PASS: TestAccountExtension_AssetVsLiability
```

## Field Descriptions

### SortOrder (int)
- **Purpose:** Controls the display order of accounts in the account list
- **Default:** 0
- **Usage:** Allows users to drag and reorder accounts, with the order persisted to the database
- **Validates:** Requirements 1.3, 1.4

### WarningThreshold (*float64)
- **Purpose:** Balance threshold below which a warning should be displayed
- **Type:** Pointer to allow null values (no warning if not set)
- **Usage:** When balance < threshold, display an orange "预警" (warning) badge
- **Validates:** Requirements 1.5, 1.7, 1.10

### LastSyncTime (*time.Time)
- **Purpose:** Tracks the last time the account was synchronized
- **Type:** Pointer to allow null values
- **Format:** Displayed as "MM月DD日 HH:mm" in the UI
- **Validates:** Requirements 1.8

### AccountCode (string)
- **Purpose:** Unique identifier for the account (e.g., "Alipay", "Wechat", "ICBC-1234")
- **Max Length:** 50 characters
- **Usage:** Displayed in account details to help users identify accounts
- **Validates:** Requirements 1.9

### AccountType (string)
- **Purpose:** Classifies accounts as either "asset" or "liability"
- **Default:** "asset"
- **Values:** "asset" (positive balance accounts) or "liability" (negative balance accounts like credit cards)
- **Usage:** Used to calculate total assets (only includes asset type accounts)
- **Validates:** Requirements 1.2

## Requirements Validation

This implementation validates the following requirements from the specification:

- **1.2** - Total assets calculation only includes asset type accounts
- **1.3** - Accounts can be reordered using drag handles
- **1.4** - Account order is persisted using sort_order field
- **1.5** - Warning badge displayed when balance < threshold
- **1.7** - Warning threshold can be set in account details
- **1.8** - Last sync time is displayed in account details
- **1.9** - Account unique ID (code) is displayed in account details
- **1.10** - No warning displayed when threshold is not set (null)

## Database Schema Changes

The migration adds the following columns to the `accounts` table:

```sql
ALTER TABLE accounts 
    ADD COLUMN sort_order INT DEFAULT 0,
    ADD COLUMN warning_threshold DECIMAL(15,2) DEFAULT NULL,
    ADD COLUMN last_sync_time DATETIME DEFAULT NULL,
    ADD COLUMN account_code VARCHAR(50) DEFAULT NULL,
    ADD COLUMN account_type VARCHAR(20) DEFAULT 'asset';
```

With indexes:
```sql
ALTER TABLE accounts 
    ADD INDEX idx_accounts_sort_order (sort_order),
    ADD INDEX idx_accounts_account_type (account_type);
```

## Running the Migration

### Option 1: Using GORM AutoMigrate (Recommended)

```bash
cd backend
go run cmd/migrate/main.go
```

GORM will automatically detect the new fields and add them to the database.

### Option 2: Manual SQL Execution

```bash
mysql -u your_username -p your_database < backend/migrations/004_extend_account_model.sql
```

## Testing

Run the unit tests:

```bash
cd backend
go test -v ./internal/models -run TestAccountExtension
```

All tests should pass.

## Next Steps

After this implementation:

1. The Account model is ready for use in the asset management page
2. Backend API handlers can now use these fields for:
   - Account reordering (PUT /api/accounts/reorder)
   - Warning threshold settings
   - Sync time tracking
   - Asset vs liability filtering
3. Frontend components can display:
   - Sorted account lists
   - Warning badges
   - Sync times
   - Account codes
   - Total assets (excluding liabilities)

## Related Tasks

- Task 6.1: Implement account reordering API
- Task 9.1: Implement AssetSummaryCard component (uses AccountType)
- Task 9.2: Implement DraggableAccountList component (uses SortOrder, WarningThreshold, LastSyncTime, AccountCode)

## Notes

- All new fields are optional (nullable or have defaults) to maintain backward compatibility
- The AccountType field defaults to "asset" for existing accounts
- Warning threshold logic: `shouldWarn = threshold != nil && balance < threshold`
- The model is already registered in `AllModels()` function, so no additional registration is needed