# Docker Compose file format version
# 3.9 is a commonly used Compose file version
# version: "3.9"

# Defines all containers (services) that belong to this application
services:

  # MongoDB database service
  mongo:
    # Uses the official MongoDB image, version 7
    image: mongo:7

    # Gives the container a fixed name so it is easier to identify in Docker
    container_name: mongo-crud-db

    # Automatically restarts the container if it stops because of a failure
    restart: on-failure

    # Environment variables passed into the MongoDB container
    environment:
      # Creates the MongoDB root/admin username on first startup
      MONGO_INITDB_ROOT_USERNAME: admin

      # Creates the MongoDB root/admin password on first startup
      MONGO_INITDB_ROOT_PASSWORD: admin123

    # Connects this container to the custom Docker network below
    networks:
      - mongo-crud-net

    # Mounts a named Docker volume into MongoDB's data folder
    # This keeps database data persistent even if the container is recreated
    volumes:
      - mongo_crud_data:/data/db

  # Flask web application service
  web:
    # Builds the image from the Dockerfile in the current folder
    build: .

    # Gives the web container a fixed name
    container_name: mongo-crud-web

    # Automatically restarts the container if it fails
    restart: on-failure

    # Tells Docker to start the mongo service before the web service
    # Note: this does not guarantee MongoDB is fully ready, only that it starts first
    depends_on:
      - mongo

    # Environment variables passed into the Flask application
    environment:
      # MongoDB connection string used by the Flask app
      # The hostname "mongo" works because it is the service name on the Docker network
      MONGO_URI: mongodb://admin:admin123@mongo:27017/

      # MongoDB database name the app should use
      MONGO_DB_NAME: appdb

      # MongoDB collection name the app should use
      MONGO_COLLECTION_NAME: products

      # Flask secret key used for sessions and flash messages
      SECRET_KEY: mongo-crud-secret

      # Port the Flask app listens on inside the container
      PORT: 8080

    # Maps ports between the host machine and the container
    # Left side = host port, right side = container port
    ports:
      - "8080:8080"

    # Connects the web container to the same Docker network as MongoDB
    networks:
      - mongo-crud-net

# Defines custom Docker networks used by the application
networks:
  mongo-crud-net:
    # Explicitly sets the network name instead of letting Docker generate one
    name: mongo-crud-net

# Defines named Docker volumes used by the application
volumes:
  mongo_crud_data:
    # Explicitly sets the volume name
    # This volume stores MongoDB files persistently
    name: mongo_crud_data