Crypto Wallet and Holdings Schema

erDiagram
  APP_USER ||--o{ WALLET : owns
  CHAIN ||--o{ WALLET : "hosts"
  CHAIN ||--o{ TOKEN : "issues"
  WALLET ||--o{ BALANCE : holds
  TOKEN ||--o{ BALANCE : "held as"
  WALLET ||--o{ CHAIN_TX : records
  TOKEN ||--o{ CHAIN_TX : moves
  APP_USER {
    int id PK
    string email
  }
  CHAIN {
    int id PK
    string name
    int chain_id
  }
  WALLET {
    int id PK
    int user_id FK
    int chain_ref FK
    string address
  }
  TOKEN {
    int id PK
    int chain_ref FK
    string symbol
    string contract_address
    int decimals
  }
  BALANCE {
    int id PK
    int wallet_id FK
    int token_id FK
    decimal amount
  }
  CHAIN_TX {
    int id PK
    int wallet_id FK
    int token_id FK
    string tx_hash
    decimal amount
    string direction
    datetime block_time
  }