backend.json

{
  "entities": {
    "User": {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "title": "User",
      "type": "object",
      "description": "Represents a user of the ZeppFusion AI application.",
      "properties": {
        "id": {
          "type": "string",
          "description": "Unique identifier for the User entity."
        },
        "email": {
          "type": "string",
          "description": "Email address of the user.",
          "format": "email"
        },
        "displayName": {
          "type": "string",
          "description": "Display name of the user."
        },
        "creationDate": {
          "type": "string",
          "description": "Date and time the user account was created.",
          "format": "date-time"
        },
        "lastLogin": {
          "type": "string",
          "description": "Date and time of the user's last login.",
          "format": "date-time"
        },
        "theme": {
          "type": "string",
          "description": "The user's preferred theme.",
          "enum": [
            "light",
            "dark",
            "system"
          ]
        }
      },
      "required": [
        "id",
        "email",
        "displayName",
        "creationDate"
      ]
    },
    "ChatSession": {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "title": "ChatSession",
      "type": "object",
      "description": "Represents a chat session between a user and one or more AI models.",
      "properties": {
        "id": {
          "type": "string",
          "description": "Unique identifier for the ChatSession entity."
        },
        "userId": {
          "type": "string",
          "description": "Reference to User. (Relationship: User 1:N ChatSession)"
        },
        "modelUsed": {
          "type": "string",
          "description": "The AI model used in this chat session (e.g., Gemini, ChatGPT 3)."
        },
        "startTime": {
          "type": "string",
          "description": "Date and time the chat session started.",
          "format": "date-time"
        },
        "endTime": {
          "type": "string",
          "description": "Date and time the chat session ended.",
          "format": "date-time"
        }
      },
      "required": [
        "id",
        "userId",
        "modelUsed",
        "startTime"
      ]
    },
    "Message": {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "title": "Message",
      "type": "object",
      "description": "Represents a single message within a chat session.",
      "properties": {
        "id": {
          "type": "string",
          "description": "Unique identifier for the Message entity."
        },
        "chatSessionId": {
          "type": "string",
          "description": "Reference to ChatSession. (Relationship: ChatSession 1:N Message)"
        },
        "sender": {
          "type": "string",
          "description": "Indicates who sent the message (e.g., user, Gemini, ChatGPT)."
        },
        "content": {
          "type": "string",
          "description": "The text content of the message."
        },
        "timestamp": {
          "type": "string",
          "description": "Date and time the message was sent.",
          "format": "date-time"
        }
      },
      "required": [
        "id",
        "chatSessionId",
        "sender",
        "content",
        "timestamp"
      ]
    }
  },
  "auth": {
    "providers": [
      "password",
      "anonymous"
    ]
  },
  "firestore": {
    "structure": [
      {
        "path": "/users/{userId}",
        "definition": {
          "entityName": "User",
          "schema": {
            "$ref": "#/backend/entities/User"
          },
          "description": "Stores user profile data. Path-based ownership enables simple security rules.",
          "params": [
            {
              "name": "userId",
              "description": "The unique identifier of the user."
            }
          ]
        }
      },
      {
        "path": "/users/{userId}/chatSessions/{chatSessionId}",
        "definition": {
          "entityName": "ChatSession",
          "schema": {
            "$ref": "#/backend/entities/ChatSession"
          },
          "description": "Stores chat session data for a specific user. Nested under users for ownership.",
          "params": [
            {
              "name": "userId",
              "description": "The unique identifier of the user."
            },
            {
              "name": "chatSessionId",
              "description": "The unique identifier of the chat session."
            }
          ]
        }
      },
      {
        "path": "/users/{userId}/chatSessions/{chatSessionId}/messages/{messageId}",
        "definition": {
          "entityName": "Message",
          "schema": {
            "$ref": "#/backend/entities/Message"
          },
          "description": "Stores messages within a chat session. Nested under chat sessions for data locality and ownership.",
          "params": [
            {
              "name": "userId",
              "description": "The unique identifier of the user."
            },
            {
              "name": "chatSessionId",
              "description": "The unique identifier of the chat session."
            },
            {
              "name": "messageId",
              "description": "The unique identifier of the message."
            }
          ]
        }
      }
    ],
    "reasoning": "The Firestore structure is designed to ensure authorization independence, clarity, and scalability. User data is stored under `/users/{userId}`, providing path-based ownership, and chat sessions and messages are nested under the user for clear ownership and easy querying. Denormalization is avoided since the application use case fits a strict ownership model. This structure allows for simple and robust security rules based on `request.auth.uid` without requiring complex `get()` calls, thus ensuring atomic operations and ease of debugging.  The structure also facilitates secure list operations, as each collection has a consistent security posture due to the path-based ownership and nested structure."
  }
}