Task 4.5 Implementation Summary: Add GraphQL Types and Resolvers for Inventory

Task 4.5 Implementation Summary: Add GraphQL Types and Resolvers for Inventory

✅ Completed Implementation

1. GraphQL Schema Updates

Updated lib/bartendie_web/schema.ex:

• Added new inventory queries:
  • product(id: ID!) - Get single product by ID
  • products(type: ProductType, brand: String) - Get all products with filtering
  • productInventory(id: ID!) - Get inventory level for a product
  • inventoryTransactions(productId: ID!, dateFrom: DateTime, dateTo: DateTime) - Get transaction history
• Added new inventory mutations:
  • createProduct(input: CreateProductInput!) - Create new products
  • Existing updateInventoryLevel(id: ID!, level: Float!) - Update inventory levels

Updated lib/bartendie_web/schema/inventory_types.ex:

• Enhanced Product type with missing fields (type, currentLevel, updatedAt)
• Updated InventoryTransaction type to match domain model
• Added InventoryLevel type for inventory level queries
• Updated transaction type enum to match domain model (restock, usage, adjustment, waste, transfer, initial)
• Added currentLevel field to CreateProductInput

2. GraphQL Resolvers Implementation

Completely rewrote lib/bartendie_web/resolvers/inventory.ex:

Query Resolvers:

• get_product/3 - Retrieves single product from read model
• get_all_products/3 - Retrieves all products with optional filtering by type and brand
• get_product_inventory/3 - Returns current inventory level for a product
• get_inventory_transactions/3 - Returns transaction history with optional date filtering
• list_inventory/3 - Returns inventory items (products formatted as inventory items)

Mutation Resolvers:

• create_product/3 - Dispatches CreateProduct command and returns created product
• update_level/3 - Dispatches UpdateInventory command and returns updated inventory item
• add_item/3 - Creates new product or updates existing product level

Nested Field Resolvers:

• get_product_for_inventory_item/3 - Resolves product for inventory items
• is_low_stock/3 - Calculates low stock status
• get_usage_history/3 - Returns transaction history for inventory items

Helper Functions:

• Database query filtering by product type, brand, low stock status, and date ranges
• Product-to-inventory-item transformation
• Error message formatting

3. Domain Integration

Connected to existing domain layer:

• Uses Bartendie.App.dispatch/1 for command dispatch
• Queries read models via Bartendie.Repo
• Integrates with existing CreateProduct and UpdateInventory commands
• Uses existing Product and InventoryTransaction schemas
• Leverages existing projections for read model updates

4. Testing

Created comprehensive tests:

• test/bartendie_web/resolvers/inventory_test.exs - Unit tests for all resolvers
• test/bartendie_web/graphql/inventory_integration_test.exs - GraphQL integration tests
• test_inventory_graphql.exs - Standalone test script for manual testing

🎯 GraphQL API Capabilities

Available Queries:

# Get single product
product(id: ID!): Product

# Get all products with filtering
products(type: ProductType, brand: String): [Product!]!

# Get inventory level for a product
productInventory(id: ID!): InventoryLevel

# Get transaction history
inventoryTransactions(productId: ID!, dateFrom: DateTime, dateTo: DateTime): [InventoryTransaction!]!

# Get inventory items (legacy format)
inventory(category: ProductType, lowStockOnly: Boolean): [InventoryItem!]!

Available Mutations:

# Create new product
createProduct(input: CreateProductInput!): Product

# Update inventory level
updateInventoryLevel(id: ID!, level: Float!): InventoryItem

# Add inventory item (creates or updates)
addInventoryItem(input: AddInventoryInput!): InventoryItem

Key Features:

• Command-Query Separation: Mutations dispatch commands, queries read from projections
• Real-time Updates: Changes are projected to read models automatically
• Filtering Support: Products can be filtered by type, brand, stock level
• Transaction History: Full audit trail of inventory changes
• Error Handling: Proper GraphQL error responses
• Type Safety: Strong typing with Absinthe schema validation

🔧 Technical Implementation Details

Architecture:

• CQRS Pattern: Commands modify state, queries read from projections
• Event Sourcing: All changes create events that update read models
• GraphQL Layer: Provides unified API over domain services
• Authentication: Mutations require authentication (queries are public)

Data Flow:

1. GraphQL mutation → Resolver → Command dispatch → Aggregate → Event
2. Event → Projection → Read model update
3. GraphQL query → Resolver → Read model query → Response

Error Handling:

• Command validation errors are formatted for GraphQL
• Database errors are caught and returned as GraphQL errors
• Non-existent resources return appropriate null/error responses

🚀 Usage Examples

Create a Product:

mutation {
  createProduct(input: {
    name: "Bourbon Whiskey"
    brand: "Buffalo Trace"
    productType: SPIRIT
    volume: 750.0
    currentLevel: 750.0
    barcode: "123456789"
  }) {
    id
    name
    brand
    type
    currentLevel
  }
}

Update Inventory Level:

mutation {
  updateInventoryLevel(id: "product-id", level: 500.0) {
    productId
    currentLevel
    lastUpdated
  }
}

Query Products:

query {
  products(type: SPIRIT) {
    id
    name
    brand
    currentLevel
    type
  }
}

Get Transaction History:

query {
  inventoryTransactions(productId: "product-id") {
    transactionType
    previousLevel
    currentLevel
    reason
    timestamp
  }
}

✅ Task Requirements Fulfilled

• ✅ GraphQL types for Product, InventoryLevel, and InventoryTransaction - Implemented
• ✅ getProduct(id) query - Implemented as product(id: ID!)
• ✅ getAllProducts query - Implemented as products(type: ProductType, brand: String)
• ✅ getProductInventory(id) query - Implemented as productInventory(id: ID!)
• ✅ getInventoryTransactions(productId, dateRange) query - Implemented with date filtering
• ✅ createProduct mutation - Implemented with full command dispatch
• ✅ updateInventoryLevel mutation - Implemented with command dispatch
• ✅ Resolvers connected to command dispatch and read models - Fully integrated
• ✅ Integration tests for each operation - Comprehensive test suite created

🎉 Ready for Use

The GraphQL API is now fully functional and ready for frontend integration. All inventory operations can be performed through the GraphQL endpoint at /api/graphql, with GraphiQL available at /api/graphiql for interactive testing.