Send a SMS message via Twilio

export default async function main(args) {
  // Extract necessary variables from args
  const { phoneNumber, messageBody, twilioAccountSid, twilioAuthToken, twilioNumber } = args.inputVars;
  
  // Custom Base64 encoding
  function base64Encode(str) {
    // Define the character set for Base64 encoding
    const charSet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    let base64 = '';

    for (let i = 0; i < str.length; i += 3) {
      const byte1 = str.charCodeAt(i);
      const byte2 = str.charCodeAt(i + 1) || 0;
      const byte3 = str.charCodeAt(i + 2) || 0;

      const enc1 = byte1 >> 2;
      const enc2 = ((byte1 & 0x03) << 4) | (byte2 >> 4);
      const enc3 = i + 1 < str.length ? ((byte2 & 0x0f) << 2) | (byte3 >> 6) : 64;
      const enc4 = i + 2 < str.length ? (byte3 & 0x3f) : 64;

      base64 += charSet.charAt(enc1) + charSet.charAt(enc2) + charSet.charAt(enc3) + charSet.charAt(enc4);
    }

    return base64;
  }

  // Construct the POST data string for the Twilio API request
  const postData = `To=${encodeURIComponent(phoneNumber)}&From=${encodeURIComponent(twilioNumber)}&Body=${encodeURIComponent(messageBody)}`;

  // Twilio API endpoint for sending SMS
  const twilioUrl = `https://api.twilio.com/2010-04-01/Accounts/${twilioAccountSid}/Messages.json`;

  // Prepare the authorization header using the custom base64 encoding function
  const encodedCredentials = base64Encode(`${twilioAccountSid}:${twilioAuthToken}`);

  // Set up the headers for the Twilio API request
  const headers = {
    'Authorization': `Basic ${encodedCredentials}`,
    'Content-Type': 'application/x-www-form-urlencoded'
  };

  // Send the SMS message using Twilio's API
  try {
    const response = await fetch(twilioUrl, {
      method: 'POST',
      headers: headers,
      body: postData
    });

    // Access the response directly (Voiceflow's modification to the standard Fetch API)
    const jsonResponse = response.json; // Accessing the JSON response

    // Handle the Twilio response here
    if (jsonResponse && jsonResponse.sid) {
      // Message sent successfully
      return {
        next: {
          path: 'success'
        },
        trace: [{
          type: 'text',
          payload: {
            message: `Message sent successfully to ${phoneNumber}`
          }
        }]
      };
    } else {
      // Message failed to send
      return {
        next: {
          path: 'fail'
        },
        trace: [{
          type: 'text',
          payload: {
            message: `Failed to send message: ${jsonResponse.message}`
          }
        }]
      };
    }
  } catch (error) {
    // Handle fetch errors
    return {
      next: {
        path: 'fail'
      },
      trace: [{
        type: 'text',
        payload: {
          message: `Error sending message: ${error.message}`
        }
      }]
    };
  }
}