export class RPCError extends Error {

  constructor(source) {
    
    super("A remote error occured");
    
    this.source = source;
    this.name = this.constructor.name;

    if (typeof Error.captureStackTrace === 'function') {
      Error.captureStackTrace(this, this.constructor);
    } else { 
      this.stack = (new Error(message)).stack; 
    }

  }

  getSource() {
    return this.source;
  }

}

export class JSONRPC {
  
  constructor(endpoint) {
    this.endpoint = endpoint;
    this.id = 0;
  }

  call(method, params, isNotification = false) {
    const requestId = this.id++;
    return fetch(this.endpoint, {
      method: 'POST',
      headers:{
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        id: isNotification ? null : requestId,
        method,
        params: params || [],
      })
    })
    .then(res => res.json())
    .then(result => {
      if (result.error) throw new RPCError(result.error);
      if (!isNotification && requestId !== result.id) throw new Error("unexpected id in rpc response");
      return result;
    });
  }

}