Creating Custom Indicators

To create a custom indicator, extend the BaseIndicator class. Here's a detailed example:

class MyCustomIndicator extends BaseIndicator {

  constructor(id, params) {
    super(id, params);
    // Validate and store any parameters
    if (!params.period || params.period <= 0) {
      throw new Error('Invalid period parameter');
    }
    //store state for each token separately
    this.tokenState = new Map();
  }

  /**
   * Called for each new price bar/candle.
   * - candle: Single row of price/volume data
   * - barIndex: Current bar index (optional, can be used for initialization)
   */
  onNewBar(candle, barIndex) {
    const token = candle.token_address;
  
    // Get or initialize state for this token
    let state = this.tokenState.get(token);
    if (!state) {
      state = { 
        values: [],
        sum: 0
      };
      this.tokenState.set(token, state);
    }

    // Update the indicator's value
    const price = candle.close; // or any other field
    state.values.push(price);
    state.sum += price;

    // Maintain rolling window if needed
    if (state.values.length > this.params.period) {
      state.sum -= state.values.shift();
    }
  }

  /**
   * Return the indicator's value for a given token
   * - token: The token address to get value for
   * - barIndex: Optional bar index (rarely used)
   * Returns: number | undefined (use NaN for "not yet ready")
   */
  getValue(token, barIndex) {
    const state = this.tokenState.get(token);
    if (!state || state.values.length < this.params.period) {
      return NaN; // Not enough data yet
    }
    return state.sum / this.params.period;
  }

  /**
   * Optional: Add custom methods to get additional values
   * Similar to how MACD has getSignal() and getHistogram()
   */
  getCustomValue(token) {
    const state = this.tokenState.get(token);
    if (!state) return NaN;
    return someCalculation(state);
  }
}

// Register your custom indicator
registerIndicator(
  "MyCustom",           // Name for this type of indicator
  MyCustomIndicator,    // Your class (not "BUILTIN")
  { period: 20 },       // Parameters
  "CUSTOM_20"          // Optional: custom ID for this instance
);

Key Points for Custom Indicators

1. State Management

   • Always use a Map to store state per token
   • Initialize state when first seeing a token
   • Consider using TypeScript-like interfaces for state objects

2. Data Access

   • The candle object in onNewBar contains a single row of data
   • All fields (open, high, low, etc.) are single values, not arrays
   • Always access the token via candle.token_address

3. Value Calculation

   • Return NaN when not enough data is available
   • Consider edge cases (division by zero, initialization, etc.)
   • Add custom methods if you need to return multiple values

4. Best Practices

   • Validate parameters in constructor
   • Use clear variable names
   • Comment complex calculations
   • Consider memory usage with rolling windows
   • Clean up old data if tokens become inactive