Enviar WhatsApp con Kotlin: ejemplo de API REST (OkHttp y Android)

cURL

curl -X POST https://api.zapzapapi.com/api/v1/SEU_INSTANCE_ID/send/text \
  -H "Content-Type: application/json" \
  -H "x-api-key: SUA_API_KEY" \
  -H "x-api-secret: SEU_API_SECRET" \
  -d '{"number":"5511999999999","text":"Olá! Teste de envio pela API."}'

Kotlin

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.RequestBody.Companion.toRequestBody
import org.json.JSONObject
import java.util.concurrent.TimeUnit

class ZapZapClient(
    private val instancia: String,
    private val key: String,
    private val secret: String,
) {
    private val http = OkHttpClient.Builder()
        .connectTimeout(5, TimeUnit.SECONDS)
        .readTimeout(30, TimeUnit.SECONDS)
        .build()
    private val json = "application/json".toMediaType()

    suspend fun enviarTexto(numero: String, texto: String): String = post(
        "/send/text",
        JSONObject().put("number", numero).put("text", texto),
    )

    private suspend fun post(caminho: String, corpo: JSONObject): String =
        withContext(Dispatchers.IO) {
            val req = Request.Builder()
                .url("https://api.zapzapapi.com/api/v1/" + instancia + caminho)
                .header("x-api-key", key)
                .header("x-api-secret", secret)
                .post(corpo.toString().toRequestBody(json))
                .build()
            http.newCall(req).execute().use { r ->
                val texto = r.body?.string().orEmpty()
                check(r.isSuccessful) { "ZapZap " + r.code + ": " + texto }
                texto
            }
        }
}

Kotlin

// dentro de ZapZapClient
suspend fun enviarPdf(numero: String, url: String, nome: String, legenda: String = ""): String = post(
    "/send/media",
    JSONObject()
        .put("number", numero)
        .put("type", "document")
        .put("file", url)
        .put("docName", nome)
        .put("text", legenda),
)

Kotlin (Ktor)

import io.ktor.http.HttpStatusCode
import io.ktor.server.application.*
import io.ktor.server.request.receive
import io.ktor.server.response.respond
import io.ktor.server.routing.*

data class Aviso(val numero: String, val texto: String)

fun Application.rotas(zap: ZapZapClient) {
    routing {
        post("/avisos") {
            // aqui: autentique o usuário do app e aplique limites seus
            val aviso = call.receive<Aviso>()
            val resposta = runCatching { zap.enviarTexto(aviso.numero, aviso.texto) }
            resposta.onSuccess { call.respond(HttpStatusCode.Accepted, it) }
                .onFailure { call.respond(HttpStatusCode.BadGateway, "falha no envio") }
        }
    }
}