init comment-service

services/comment-service/comment_service/postgres/migrations/000001_init_comments.down.sql

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+DROP TABLE IF EXISTS comments CASCADE;

services/comment-service/comment_service/postgres/migrations/000001_init_comments.up.sql

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+CREATE TABLE comments (
+    "id" serial PRIMARY KEY,
+    
+    "post_id" varchar(64) NOT NULL,
+    "author_id" varchar(64) NOT NULL,
+
+    "message" varchar(512) NOT NULL,
+
+    "created_at" timestamp NOT NULL DEFAULT timezone('utc', now()),
+    "updated_at" timestamp
+);

services/comment-service/comment_service/postgres/repository.py

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+from typing import List
+
+from databases import Database
+
+from comment_service.events.producer import CommentEventProducer
+from comment_service.models.exceptions import ServiceException, ServiceErrorCode
+from comment_service.models.service import CommentDBRepository, Comment, CommentCreate, CommentUpdate
+
+
+class ServiceDBRepository(CommentDBRepository):
+    """Database repository responsible for actions
+    relating to the postgres database.
+    
+    This repository will be utilised by other upstream repositories
+    or the Kafka event consumers.
+
+    Attributes:
+        _db (Database): The postgres database connection handler.
+        _event_prod (CommentEventProducer): Used to dispatch events upon execution of a CRUD action.
+
+    """
+    def __init__(self, db: Database, event_producer: CommentEventProducer) -> None:
+        self._db = db
+        self._event_prod = event_producer
+
+    def _result_to_comment(self, result) -> Comment:
+        return Comment(
+            id=result.id,
+            post_id=result.post_id,
+            author_id=result.author_id,
+            message=result.message,
+            created_at=result.created_at,
+            updated_at=result._mapping.get("updated_at", None)
+        )
+
+    async def get_post_comments(self, post_id: str) -> List[Comment]:
+        query = "SELECT id, post_id, author_id, message, created_at, updated_at FROM comments WHERE post_id = :post_id"
+        rows = await self._db.fetch_all(query=query, values={"post_id": post_id})
+        return [self._result_to_comment(result) for result in rows]
+    
+    async def create_comment(self, data: CommentCreate) -> Comment:
+        query = "INSERT INTO comments (post_id, author_id, message) VALUES (:post_id, :author_id, :message) RETURNING id"
+        result = await self._db.execute(query=query, values={"post_id": data.post_id, "author_id": data.author_id, "message": data.message})
+
+        comment = await self.get_comment(result)
+        await self._event_prod.send_created_event(comment)
+        return comment
+
+    async def update_comment(self, comment_id: int, data: CommentUpdate) -> Comment:
+        query = "UPDATE comments SET message = :message, updated_at = now() WHERE id = :comment_id"
+        await self._db.execute(query=query, values={"message": data.message, "comment_id": comment_id})
+
+        comment = await self.get_comment(comment_id)
+        await self._event_prod.send_updated_event(comment)
+        return comment
+    
+    async def delete_comment(self, comment_id: int) -> None:
+        comment = await self.get_comment(comment_id)
+
+        query = "DELETE FROM comments WHERE id = :comment_id"
+        await self._db.execute(query=query, values={"comment_id": comment_id})
+
+        await self._event_prod.send_deleted_event(comment)
+    
+    async def get_comment(self, comment_id: int) -> Comment:
+        query = "SELECT id, post_id, author_id, message, created_at, updated_at FROM comments WHERE id = :comment_id"
+        result = await self._db.fetch_one(query=query, values={"comment_id": comment_id})
+        if result is None:
+            raise ServiceException(message="no comment found", error_code=ServiceErrorCode.NOT_FOUND)
+        
+        return self._result_to_comment(result)
+
+    async def delete_post_comments(self, post_id: str) -> None:
+        comments = await self.get_post_comments(post_id)
+
+        query = "DELETE FROM comments WHERE post_id = :post_id"
+        await self._db.execute(query=query, values={"post_id": post_id})
+
+        for comment in comments:
+            await self._event_prod.send_deleted_event(comment)
+    
+    async def delete_user_comments(self, user_id: str) -> None:
+        comments = await self.get_post_comments(user_id)
+
+        query = "DELETE FROM comments WHERE author_id = :author_id"
+        await self._db.execute(query=query, values={"author_id": user_id})
+
+        for comment in comments:
+            await self._event_prod.send_deleted_event(comment)
+
+    async def _get_user_comments(self, user_id: str) -> List[Comment]:
+        query = "SELECT id, post_id, author_id, message, created_at, updated_at FROM comments WHERE author_id = :user_id"
+        rows = await self._db.fetch_all(query=query, values={"user_id": user_id})
+        return [self._result_to_comment(result) for result in rows]

services/comment-service/comment_service/postgres/service.py

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+import logging
+
+from databases import Database
+
+from comment_service.models.config import Config
+from comment_service.events.producer import CommentEventProducer
+from comment_service.postgres.repository import ServiceDBRepository
+
+
+async def connect_database(config: Config) -> Database:
+    """Opens a connection to the database.
+    
+    Args:
+        config (Config): The app configuration.
+
+    Returns:
+        A connected databases.Database instance
+
+    """
+    db = Database(config.postgres_dsn)
+    try:
+        await db.connect()
+    except Exception:
+        logging.error("failed to connect to postgresql database")
+        raise
+    
+    return db
+
+
+async def create_db_repository(config: Config, event_producer: CommentEventProducer) -> ServiceDBRepository:
+    """Create the database repository.
+    
+    Open a database connection and instantialise the
+    database repository.
+
+    Returns:
+        ServiceDBRepository
+    
+    """
+    db = await connect_database(config)
+    return ServiceDBRepository(db, event_producer)