# Table Restructuring Summary

## Overview
This document summarizes the changes made to restructure the letter dispositions system from a single table to a more normalized structure with an association table.

## Changes Made

### 1. Database Schema Changes

#### New Migration Files Created:
- `migrations/000012_rename_dispositions_table.up.sql` - Main migration to restructure tables
- `migrations/000012_rename_dispositions_table.down.sql` - Rollback migration

#### Table Changes:
- **`letter_dispositions`** → **`letter_incoming_dispositions`**
  - Renamed table
  - Removed columns: `from_user_id`, `to_user_id`, `to_department_id`, `status`, `completed_at`
  - Renamed `from_department_id` → `department_id`
  - Added `read_at` column
  - Kept columns: `id`, `letter_id`, `department_id`, `notes`, `read_at`, `created_at`, `created_by`, `updated_at`

#### New Table Created:
- **`letter_incoming_dispositions_department`**
  - Purpose: Associates dispositions with target departments
  - Columns: `id`, `letter_incoming_disposition_id`, `department_id`, `created_at`
  - Unique constraint on `(letter_incoming_disposition_id, department_id)`

### 2. Entity Changes

#### Updated Entities:
- **`LetterDisposition`** → **`LetterIncomingDisposition`**
  - Simplified structure with only required fields
  - New table name mapping

#### New Entity:
- **`LetterIncomingDispositionDepartment`**
  - Represents the many-to-many relationship between dispositions and departments

### 3. Repository Changes

#### Updated Repositories:
- **`LetterDispositionRepository`** → **`LetterIncomingDispositionRepository`**
  - Updated to work with new entity

#### New Repository:
- **`LetterIncomingDispositionDepartmentRepository`**
  - Handles CRUD operations for the association table
  - Methods: `CreateBulk`, `ListByDisposition`

### 4. Processor Changes

#### Updated Processor:
- **`LetterProcessorImpl`**
  - Added new repository dependency
  - Updated `CreateDispositions` method to:
    - Create main disposition record
    - Create department association records
    - Maintain existing action selection functionality

### 5. Transformer Changes

#### Updated Transformer:
- **`DispositionsToContract`** function
  - Updated to work with new entity structure
  - Maps new fields: `DepartmentID`, `ReadAt`, `UpdatedAt`
  - Removed old fields: `FromDepartmentID`, `ToDepartmentID`, `Status`

### 6. Contract Changes

#### Updated Contract:
- **`DispositionResponse`** struct
  - Updated fields to match new entity structure
  - Added `ReadAt` and `UpdatedAt` fields
  - Replaced `FromDepartmentID` and `ToDepartmentID` with `DepartmentID`

### 7. Application Configuration Changes

#### Updated App Configuration:
- **`internal/app/app.go`**
  - Updated repository initialization
  - Added new repository dependency
  - Updated processor initialization with new repository

## Migration Process

### Up Migration (000012_rename_dispositions_table.up.sql):
1. Rename `letter_dispositions` to `letter_incoming_dispositions`
2. Drop unnecessary columns
3. Rename `from_department_id` to `department_id`
4. Add missing columns (`read_at`, `updated_at`)
5. Create new association table
6. Update triggers and indexes

### Down Migration (000012_rename_dispositions_table.down.sql):
1. Drop association table
2. Restore removed columns
3. Rename `department_id` back to `from_department_id`
4. Restore old triggers and indexes
5. Rename table back to `letter_dispositions`

## Benefits of New Structure

1. **Normalization**: Separates disposition metadata from department associations
2. **Flexibility**: Allows multiple departments per disposition
3. **Cleaner Data Model**: Removes redundant fields and simplifies the main table
4. **Better Performance**: Smaller main table with focused indexes
5. **Easier Maintenance**: Clear separation of concerns

## Breaking Changes

- Table name change from `letter_dispositions` to `letter_incoming_dispositions`
- Entity structure changes (removed fields, renamed fields)
- Repository interface changes
- API response structure changes

## Testing Recommendations

1. Run migration on test database
2. Test disposition creation with new structure
3. Verify department associations are created correctly
4. Test existing functionality (action selections, notes)
5. Verify rollback migration works correctly

## Rollback Plan

If issues arise, the down migration will:
1. Restore the original table structure
2. Preserve all existing data
3. Remove the new association table
4. Restore original triggers and indexes
