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Repository Layer

Under Reviewv0.1.0-alpha

Business modules never import database driver packages (like pgx or the MongoDB driver). Instead, they define repository interfaces in their domain layer and receive concrete implementations at runtime through the RepoProvider. Switching databases is a config change, not a code change.

The Pattern​

                 ┌──────────────────────┐
                 │     RepoProvider     │
                 └──────────┬───────────┘
                            │
           Based on:        │
           "db.type"        ├── "mongodb"  ──► mongoWishlist.NewRepository()
                            │
                            └── "postgres" ──► pgWishlist.NewRepository()

The RepoProvider is a struct held in the container (c.Repos). It reads the configured db.type and routes each repository request to the correct driver implementation. All database-specific code lives under internal/infra/db/.

Module Side: Define the Interface​

In your module's domain layer, define a repository interface with no imports from any DB package:

// internal/modules/wishlist/domain.go
package wishlist

import "context"

type Repository interface {
    Add(ctx context.Context, item *WishlistItem) error
    Get(ctx context.Context, userID string) ([]*WishlistItem, error)
}

The module only knows this interface. It never knows which database backs it.

Infra Side: Implement per Driver​

Implement the interface for each supported database:

internal/infra/db/
├── mongodb/
│   └── wishlist/
│       └── repo.go     # implements wishlist.Repository using MongoDB
└── postgres/
    └── wishlist/
        └── repo.go     # implements wishlist.Repository using pgx / GORM

Wire in RepoProvider​

Add a method to repoprovider.go that switches on db.type and returns the correct implementation:

func (rp *RepoProvider) WishlistRepo() wishlist.Repository {
    switch rp.dbType {
    case "mongodb":
        return mongoWishlist.NewRepository(rp.mongoDB)
    case "postgres":
        return pgWishlist.NewRepository(rp.pgAdapter)
    }
    return nil
}

Module Init: Fetch from Container​

In your module's Init(), call the provider method - you get back the interface, typed correctly:

func (m *Module) Init(c *engine.Container) error {
    repo := c.Repos.WishlistRepo()
    m.service = NewWishlistService(repo)
    return nil
}

The module code is identical regardless of which database is configured. Only repoprovider.go and the internal/infra/db/ implementations differ between drivers.