database.rules.json

{
  "rules": {
    "channels": {
      ".read": "auth != null",
      "$channelId": {
        ".write": "auth != null",
        ".validate": "newData.hasChildren(['id', 'name', 'createdBy', 'details'])",
        "id": {
          ".validate": "newData.val() === $channelId"
        },
        "name": {
          ".validate": "newData.val().length > 0"
        },
        "details": {
          ".validate": "newData.val().length > 0"
        }
      }
    },
    "messages": {
      "$channelId": {
        ".read": "auth != null",
        ".validate": "root.child('channels/'+$channelId).exists()",
        "$messageId": {
          ".write": "auth != null",
          ".validate": "(newData.hasChildren(['content', 'user', 'timestamp']) && !newData.hasChildren(['image'])) || (newData.hasChildren(['image', 'user', 'timestamp']) && !newData.hasChildren(['content']))",
          "content": {
            ".validate": "newData.val().length > 0"
          },
          "image": {
            ".validate": "newData.val().length > 0"
          },
          "user": {
            ".validate": "newData.hasChildren(['id', 'name', 'avatar'])"
          }
        }
      }
    },
    "privateMessages": {
      "$uid1": {
        "$uid2": {
          ".read": "auth != null && ($uid1 === auth.uid || $uid2 === auth.uid)",
          "$messageId": {
            ".write": "auth != null",
            ".validate": "(newData.hasChildren(['content', 'user', 'timestamp']) && !newData.hasChildren(['image'])) || (newData.hasChildren(['image', 'user', 'timestamp']) && !newData.hasChildren(['content']))",
            "content": {
              ".validate": "newData.val().length > 0"
            },
            "image": {
              ".validate": "newData.val().length > 0"
            },
            "user": {
              ".validate": "newData.hasChildren(['id', 'name', 'avatar'])"
            }
          }
        }
      }
    },
    "presence": {
      ".read": "auth != null",
      ".write": "auth != null"
    },
    "typing": {
      ".read": "auth != null",
      ".write": "auth != null"
    },
    "users": {
      ".read": "auth != null",
      "$uid": {
        ".write": "auth != null && auth.uid === $uid",
        ".validate": "newData.hasChildren(['name', 'avatar'])",
        "name": {
          ".validate": "newData.val().length > 0"
        },
        "avatar": {
          ".validate": "newData.val().length > 0"
        }
      }
    }
  }
}