From SMS to RCS – A guide to next-generation mobile communication

using System.Net.Http.Json;

var apiKey = "YOUR_API_KEY";
var rcsUrl = "https://api.ip1.net/v3";
var smsUrl = "https://api.ip1sms.com/v2";

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("Authorization", "Bearer {apiKey}");

async Task SendSmartMessages(string[] recipients, string text)
{
    var rcsRecipients = new List();
    var smsRecipients = new List();

    // 1. Loop through and sort recipients based on capability
    foreach (var number in recipients)
    {
        try
        {
            var cap = await client.GetFromJsonAsync("{rcsUrl}/phones/{number}/capabilities");
            
            if (cap?.capable == true)
                rcsRecipients.Add(number);
            else
                smsRecipients.Add(number);
        }
        catch
        {
            smsRecipients.Add(number);
        }
    }

    // 2. Send RCS to everyone who can receive it
    if (rcsRecipients.Any())
    {
        var rcsResponse = await client.PostAsJsonAsync($"{rcsUrl}/bundles", new
        {
            brand = "my-store-inc",
            agent = "YOUR_AGENT_ID",
            content = text,
            recipients = rcsRecipients.ToArray()
        });
    }

    // 3. Send SMS to the rest
    if (smsRecipients.Any())
    {
    var smsResponse = await client.PostAsJsonAsync($"{smsUrl}/messages", new
    {
        sender = "MyCompany",
        body = text,
        recipients = smsRecipients.ToArray()
    });
}

public record CapResponse(bool capable);

var myNumbers = new[] { "46700123456", "46700987654", "456189040623" };
await SendSmartMessages(myNumbers, "Hello! This is a smart message.");;