refactor: migrate to DDD architecture with Dishka DI

Complete architectural refactoring from simple MVC to Clean Architecture/DDD pattern:

Domain Layer:

- Add entities (Post, BaseEntity) with business logic

- Add value objects (Title, Content, Slug) with validation

- Add repository interfaces (PostRepository)

- Add domain exceptions

Application Layer:

- Add use cases (CreatePost, GetPost, UpdatePost, DeletePost, ListPosts, PublishPost)

- Add DTOs for data transfer

- Add TransactionManager interface

Infrastructure Layer:

- Add SQLAlchemy models and async database connection

- Add SQLAlchemyPostRepository implementation

- Add Dishka DI container with providers

- Add error handlers and middleware

Presentation Layer:

- Add FastAPI routes with Dishka integration

- Add Pydantic schemas

- Add dependency injection using FromDishka[T]

Other Changes:

- Remove old flat structure (api/, common/, core/, modules/)

- Add hatchling build system for package scripts

- Add blog CLI command

- Update AGENTS.md with new architecture docs

- All 48 tests passing, mypy clean, ruff clean

app/infrastructure/__init__.py

@@ -0,0 +1,35 @@
+"""Infrastructure layer exports."""
+
+from app.infrastructure.config import Settings, settings
+from app.infrastructure.database import (
+    AsyncSessionLocal,
+    Base,
+    PostORM,
+    close_db,
+    engine,
+    get_session,
+    init_db,
+)
+from app.infrastructure.di import create_container
+from app.infrastructure.middleware import register_exception_handlers
+from app.infrastructure.repositories import SQLAlchemyPostRepository
+
+__all__ = [
+    # Config
+    "Settings",
+    "settings",
+    # Database
+    "Base",
+    "PostORM",
+    "engine",
+    "AsyncSessionLocal",
+    "get_session",
+    "init_db",
+    "close_db",
+    # Repositories
+    "SQLAlchemyPostRepository",
+    # DI
+    "create_container",
+    # Middleware
+    "register_exception_handlers",
+]

app/infrastructure/config/__init__.py

@@ -0,0 +1,5 @@
+"""Infrastructure configuration."""
+
+from app.infrastructure.config.settings import Settings, settings
+
+__all__ = ["Settings", "settings"]

app/infrastructure/config/settings.py

@@ -0,0 +1,31 @@
+"""Application settings."""
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    """Application configuration settings."""
+
+    # App settings
+    app_name: str = "Blog API"
+    debug: bool = False
+    host: str = "0.0.0.0"
+    port: int = 8000
+
+    # Database settings
+    database_url: str = "sqlite:///./blog.db"
+    database_echo: bool = False
+
+    # Security settings
+    secret_key: str = "your-secret-key-change-in-production"
+    access_token_expire_minutes: int = 30
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+    )
+
+
+# Global settings instance
+settings = Settings()

app/infrastructure/database/__init__.py

@@ -0,0 +1,22 @@
+"""Database infrastructure."""
+
+from app.infrastructure.database.connection import (
+    AsyncSessionLocal,
+    close_db,
+    engine,
+    get_session,
+    get_session_context,
+    init_db,
+)
+from app.infrastructure.database.models import Base, PostORM
+
+__all__ = [
+    "Base",
+    "PostORM",
+    "engine",
+    "AsyncSessionLocal",
+    "get_session",
+    "get_session_context",
+    "init_db",
+    "close_db",
+]

app/infrastructure/database/connection.py

@@ -0,0 +1,70 @@
+"""Database connection and session management."""
+
+from contextlib import asynccontextmanager
+from typing import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncEngine,
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+
+from app.infrastructure.config import settings
+
+
+# Convert SQLite URL to async format if needed
+def _get_database_url() -> str:
+    url = settings.database_url
+    if url.startswith("sqlite:///") and not url.startswith("sqlite+aiosqlite:///"):
+        return url.replace("sqlite:///", "sqlite+aiosqlite:///")
+    return url
+
+
+# Create async engine
+engine: AsyncEngine = create_async_engine(
+    _get_database_url(),
+    echo=settings.database_echo,
+    future=True,
+)
+
+# Create session factory
+AsyncSessionLocal = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+    autoflush=False,
+    autocommit=False,
+)
+
+
+async def get_session() -> AsyncGenerator[AsyncSession, None]:
+    """Get database session."""
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+@asynccontextmanager
+async def get_session_context() -> AsyncGenerator[AsyncSession, None]:
+    """Get database session as context manager."""
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+async def init_db() -> None:
+    """Initialize database tables."""
+    from app.infrastructure.database.models import Base
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+
+async def close_db() -> None:
+    """Close database connections."""
+    await engine.dispose()

app/infrastructure/database/models.py

@@ -0,0 +1,40 @@
+"""SQLAlchemy ORM models."""
+
+from datetime import datetime, timezone
+from uuid import uuid4
+
+from sqlalchemy import JSON, Boolean, DateTime, String, Text
+from sqlalchemy.orm import Mapped, declarative_base, mapped_column
+
+Base = declarative_base()
+
+
+class PostORM(Base):  # type: ignore[valid-type,misc]
+    """SQLAlchemy model for Blog Post."""
+
+    __tablename__ = "posts"
+
+    id: Mapped[str] = mapped_column(
+        String(36), primary_key=True, default=lambda: str(uuid4())
+    )
+    title: Mapped[str] = mapped_column(String(200), nullable=False)
+    content: Mapped[str] = mapped_column(Text, nullable=False)
+    slug: Mapped[str] = mapped_column(
+        String(200), nullable=False, unique=True, index=True
+    )
+    author_id: Mapped[str] = mapped_column(String(100), nullable=False, index=True)
+    published: Mapped[bool] = mapped_column(
+        Boolean, default=False, nullable=False, index=True
+    )
+    tags: Mapped[list[str]] = mapped_column(JSON, default=list)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc),
+        nullable=False,
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+        nullable=False,
+    )

app/infrastructure/di/__init__.py

@@ -0,0 +1,7 @@
+"""Dependency Injection using Dishka."""
+
+from app.infrastructure.di.container import create_container
+
+__all__ = [
+    "create_container",
+]

app/infrastructure/di/container.py

@@ -0,0 +1,20 @@
+"""Dishka container setup."""
+
+from dishka import AsyncContainer, make_async_container
+
+from app.infrastructure.di.providers import (
+    DatabaseProvider,
+    RepositoryProvider,
+    TransactionManagerProvider,
+    UseCaseProvider,
+)
+
+
+def create_container() -> AsyncContainer:
+    """Create and configure Dishka container."""
+    return make_async_container(
+        DatabaseProvider(),
+        RepositoryProvider(),
+        TransactionManagerProvider(),
+        UseCaseProvider(),
+    )

app/infrastructure/di/providers.py

@@ -0,0 +1,133 @@
+"""Dishka providers for dependency injection."""
+
+from typing import AsyncGenerator
+
+from dishka import Provider, Scope, provide
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession
+
+from app.application import (
+    CreatePostUseCase,
+    DeletePostUseCase,
+    GetPostUseCase,
+    ListPostsUseCase,
+    PublishPostUseCase,
+    UpdatePostUseCase,
+)
+from app.application.interfaces import TransactionManager
+from app.domain.repositories import PostRepository
+from app.infrastructure.database.connection import AsyncSessionLocal, engine
+from app.infrastructure.repositories.post import SQLAlchemyPostRepository
+
+
+class DatabaseProvider(Provider):
+    """Provider for database-related dependencies."""
+
+    @provide(scope=Scope.APP)
+    def get_engine(self) -> AsyncEngine:
+        """Provide SQLAlchemy engine."""
+        return engine
+
+    @provide(scope=Scope.REQUEST)
+    async def get_session(self) -> AsyncGenerator[AsyncSession, None]:
+        """Provide database session per request."""
+        async with AsyncSessionLocal() as session:
+            try:
+                yield session
+            finally:
+                await session.close()
+
+
+class RepositoryProvider(Provider):
+    """Provider for repository implementations."""
+
+    @provide(scope=Scope.REQUEST)
+    def get_post_repository(self, session: AsyncSession) -> PostRepository:
+        """Provide PostRepository implementation."""
+        return SQLAlchemyPostRepository(session)
+
+
+class TransactionManagerProvider(Provider):
+    """Provider for transaction manager."""
+
+    @provide(scope=Scope.REQUEST)
+    def get_transaction_manager(self, session: AsyncSession) -> TransactionManager:
+        """Provide TransactionManager implementation."""
+        from app.infrastructure.di.transaction_manager import SessionTransactionManager
+
+        return SessionTransactionManager(session)
+
+
+class UseCaseProvider(Provider):
+    """Provider for use cases."""
+
+    @provide(scope=Scope.REQUEST)
+    def get_create_post_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> CreatePostUseCase:
+        """Provide CreatePostUseCase."""
+        return CreatePostUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
+    @provide(scope=Scope.REQUEST)
+    def get_get_post_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> GetPostUseCase:
+        """Provide GetPostUseCase."""
+        return GetPostUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
+    @provide(scope=Scope.REQUEST)
+    def get_update_post_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> UpdatePostUseCase:
+        """Provide UpdatePostUseCase."""
+        return UpdatePostUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
+    @provide(scope=Scope.REQUEST)
+    def get_delete_post_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> DeletePostUseCase:
+        """Provide DeletePostUseCase."""
+        return DeletePostUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
+    @provide(scope=Scope.REQUEST)
+    def get_list_posts_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> ListPostsUseCase:
+        """Provide ListPostsUseCase."""
+        return ListPostsUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
+    @provide(scope=Scope.REQUEST)
+    def get_publish_post_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> PublishPostUseCase:
+        """Provide PublishPostUseCase."""
+        return PublishPostUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )

app/infrastructure/di/transaction_manager.py

@@ -0,0 +1,24 @@
+"""SQLAlchemy implementation of Transaction Manager."""
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.application.interfaces import TransactionManager
+
+
+class SessionTransactionManager(TransactionManager):
+    """SQLAlchemy Session-based Transaction Manager."""
+
+    def __init__(self, session: AsyncSession) -> None:
+        self._session = session
+        self._committed: bool = False
+
+    async def commit(self) -> None:
+        """Commit the current transaction."""
+        if not self._committed:
+            await self._session.commit()
+            self._committed = True
+
+    async def rollback(self) -> None:
+        """Rollback the current transaction."""
+        if not self._committed:
+            await self._session.rollback()

app/infrastructure/middleware/__init__.py

@@ -0,0 +1,15 @@
+"""Infrastructure middleware."""
+
+from app.infrastructure.middleware.error_handler import (
+    domain_exception_handler,
+    generic_exception_handler,
+    http_exception_handler,
+    register_exception_handlers,
+)
+
+__all__ = [
+    "domain_exception_handler",
+    "http_exception_handler",
+    "generic_exception_handler",
+    "register_exception_handlers",
+]

app/infrastructure/middleware/error_handler.py

@@ -0,0 +1,93 @@
+"""Exception handling middleware."""
+
+from datetime import datetime, timezone
+
+from fastapi import FastAPI, Request
+from fastapi.responses import JSONResponse
+from starlette.exceptions import HTTPException as StarletteHTTPException
+
+from app.domain.exceptions import (
+    AlreadyExistsException,
+    DomainException,
+    ForbiddenException,
+    NotFoundException,
+    UnauthorizedException,
+    ValidationException,
+)
+
+
+def get_status_code(exc: DomainException) -> int:
+    """Map domain exceptions to HTTP status codes."""
+    match exc:
+        case ValidationException():
+            return 400
+        case UnauthorizedException():
+            return 401
+        case ForbiddenException():
+            return 403
+        case NotFoundException():
+            return 404
+        case AlreadyExistsException():
+            return 409
+        case _:
+            return 500
+
+
+async def domain_exception_handler(
+    request: Request, exc: DomainException
+) -> JSONResponse:
+    """Handle domain exceptions."""
+    status_code = get_status_code(exc)
+    return JSONResponse(
+        status_code=status_code,
+        content={
+            "error": exc.__class__.__name__,
+            "message": exc.message,
+            "timestamp": datetime.now(timezone.utc).isoformat(),
+            "path": str(request.url.path),
+        },
+    )
+
+
+async def http_exception_handler(
+    request: Request, exc: StarletteHTTPException
+) -> JSONResponse:
+    """Handle HTTP exceptions."""
+    return JSONResponse(
+        status_code=exc.status_code,
+        content={
+            "error": "HTTPException",
+            "message": str(exc.detail),
+            "timestamp": datetime.now(timezone.utc).isoformat(),
+            "path": str(request.url.path),
+        },
+    )
+
+
+async def generic_exception_handler(request: Request, exc: Exception) -> JSONResponse:
+    """Handle generic exceptions."""
+    return JSONResponse(
+        status_code=500,
+        content={
+            "error": "InternalServerError",
+            "message": "An unexpected error occurred",
+            "timestamp": datetime.now(timezone.utc).isoformat(),
+            "path": str(request.url.path),
+        },
+    )
+
+
+def register_exception_handlers(app: FastAPI) -> None:
+    """Register all exception handlers with FastAPI app."""
+    if not isinstance(app, FastAPI):
+        raise TypeError("app must be a FastAPI instance")
+
+    # Domain exceptions
+    app.add_exception_handler(DomainException, domain_exception_handler)  # type: ignore[arg-type]
+
+    # HTTP exceptions
+    app.add_exception_handler(StarletteHTTPException, http_exception_handler)  # type: ignore[arg-type]
+
+    # Generic exceptions (only in production)
+    # In development, let FastAPI show detailed traceback
+    # app.add_exception_handler(Exception, generic_exception_handler)

app/infrastructure/repositories/__init__.py

@@ -0,0 +1,5 @@
+"""Repository implementations."""
+
+from app.infrastructure.repositories.post import SQLAlchemyPostRepository
+
+__all__ = ["SQLAlchemyPostRepository"]

app/infrastructure/repositories/post.py

@@ -0,0 +1,151 @@
+"""SQLAlchemy implementation of PostRepository."""
+
+from uuid import UUID
+
+from sqlalchemy import or_, select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.domain.entities import Post
+from app.domain.repositories import PostRepository
+from app.domain.value_objects import Content, Slug, Title
+from app.infrastructure.database.models import PostORM
+
+
+class SQLAlchemyPostRepository(PostRepository):
+    """SQLAlchemy implementation of Post repository."""
+
+    def __init__(self, session: AsyncSession) -> None:
+        self._session = session
+
+    def _to_domain(self, orm: PostORM) -> Post:
+        """Convert ORM model to domain entity."""
+        return Post(
+            id=UUID(orm.id),
+            title=Title(orm.title),
+            content=Content(orm.content),
+            slug=Slug(orm.slug),
+            author_id=orm.author_id,
+            published=orm.published,
+            tags=orm.tags or [],
+            created_at=orm.created_at,
+            updated_at=orm.updated_at,
+        )
+
+    def _to_orm(self, post: Post) -> PostORM:
+        """Convert domain entity to ORM model."""
+        return PostORM(
+            id=str(post.id),
+            title=post.title.value,
+            content=post.content.value,
+            slug=post.slug.value,
+            author_id=post.author_id,
+            published=post.published,
+            tags=post.tags,
+            created_at=post.created_at,
+            updated_at=post.updated_at,
+        )
+
+    async def get_by_id(self, entity_id: UUID) -> Post | None:
+        """Get post by ID."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.id == str(entity_id))
+        )
+        orm = result.scalar_one_or_none()
+        return self._to_domain(orm) if orm else None
+
+    async def get_all(self) -> list[Post]:
+        """Get all posts."""
+        result = await self._session.execute(select(PostORM))
+        orms = result.scalars().all()
+        return [self._to_domain(orm) for orm in orms]
+
+    async def add(self, entity: Post) -> None:
+        """Add new post."""
+        orm = self._to_orm(entity)
+        self._session.add(orm)
+        # Commit делает TransactionManager
+
+    async def update(self, entity: Post) -> None:
+        """Update existing post."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.id == str(entity.id))
+        )
+        orm = result.scalar_one()
+
+        orm.title = entity.title.value
+        orm.content = entity.content.value
+        orm.slug = entity.slug.value
+        orm.published = entity.published
+        orm.tags = entity.tags
+        orm.updated_at = entity.updated_at
+
+        # Commit делает TransactionManager
+
+    async def delete(self, entity_id: UUID) -> None:
+        """Delete post by ID."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.id == str(entity_id))
+        )
+        orm = result.scalar_one_or_none()
+        if orm:
+            await self._session.delete(orm)
+
+    async def exists(self, entity_id: UUID) -> bool:
+        """Check if post exists."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.id == str(entity_id))
+        )
+        return result.scalar_one_or_none() is not None
+
+    async def get_by_slug(self, slug: str) -> Post | None:
+        """Get post by slug."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.slug == slug)
+        )
+        orm = result.scalar_one_or_none()
+        return self._to_domain(orm) if orm else None
+
+    async def get_by_author(self, author_id: str) -> list[Post]:
+        """Get posts by author."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.author_id == author_id)
+        )
+        orms = result.scalars().all()
+        return [self._to_domain(orm) for orm in orms]
+
+    async def get_published(self) -> list[Post]:
+        """Get published posts."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.published.is_(True))
+        )
+        orms = result.scalars().all()
+        return [self._to_domain(orm) for orm in orms]
+
+    async def get_by_tag(self, tag: str) -> list[Post]:
+        """Get posts by tag."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.tags.contains([tag]))
+        )
+        orms = result.scalars().all()
+        return [self._to_domain(orm) for orm in orms]
+
+    async def slug_exists(self, slug: str) -> bool:
+        """Check if slug exists."""
+        result = await self._session.execute(
+            select(PostORM).where(PostORM.slug == slug)
+        )
+        return result.scalar_one_or_none() is not None
+
+    async def search(self, query: str) -> list[Post]:
+        """Search posts."""
+        search_pattern = f"%{query}%"
+        result = await self._session.execute(
+            select(PostORM).where(
+                or_(
+                    PostORM.title.ilike(search_pattern),
+                    PostORM.content.ilike(search_pattern),
+                )
+            )
+        )
+        orms = result.scalars().all()
+        return [self._to_domain(orm) for orm in orms]