Skip to main content

​
Introduction to TecMeli

TecMeli is a robust Android client for Mercado Libre, designed following Senior Engineering standards. It implements a modular, secure, and highly scalable architecture that demonstrates best practices in modern Android development.

​
What is TecMeli?

TecMeli is a production-ready Android application that provides:
  • Advanced Product Search: Real-time product discovery with reactive state management
  • Detailed Product Views: Image galleries, technical specifications, and descriptions
  • Secure OAuth 2.0 Authentication: Automatic session management with background token refresh
  • Modern UI: Fluid interface built entirely with Jetpack Compose and Material 3
  • Robust Network Layer: Safe API call executor with semantic error mapping
This project was built as a demonstration of Clean Architecture principles and modern Android development best practices, making it an excellent learning resource for Android developers.

​
Technology Stack

TecMeli leverages the latest and most powerful tools in the Android ecosystem:
AreaTechnologies
LanguageKotlin + Coroutines + Flow
UIJetpack Compose + Material 3
Dependency InjectionDagger Hilt
NetworkingRetrofit + OkHttp + Gson
ArchitectureClean Architecture + MVVM
TestingMockK + MockWebServer + JUnit

​
Key Dependencies

From the project’s libs.versions.toml: 
[versions]
kotlin = "2.3.10"
composeBom = "2026.02.01"
hilt = "2.59.2"
retrofit = "3.0.0"
okhttp = "4.11.0"

​
Architecture Overview

TecMeli implements Clean Architecture optimized for Mercado Libre’s authentication flow. The application is structured in three main layers:

​
1. Presentation Layer (ui)

Built entirely with Jetpack Compose, featuring:
  • Home screen with product search
  • Product detail screen with image gallery
  • Navigation using Navigation 3
  • Material 3 theming

​
2. Domain Layer (domain)

Contains pure business logic:
  • Models: Domain entities like Product and ProductDetail
  • Use Cases: Business operations like GetProductsUseCase
  • Repository Interfaces: Contracts for data access

​
3. Data Layer (data)

Handles data operations:
  • Remote APIs: Retrofit interfaces for Mercado Libre API
  • DTOs: Data transfer objects for network responses
  • Mappers: Convert DTOs to domain models
  • Repository Implementations: Concrete implementations of domain contracts
package com.alcalist.tecmeli.domain.usecase

class GetProductsUseCase @Inject constructor(
    private val repository: ProductRepository
) {
    suspend operator fun invoke(query: String): Result<List<Product>> {
        return if (query.isBlank()) {
            Result.success(emptyList())
        } else {
            repository.searchProducts(query)
        }
    }
}

​
State Management

TecMeli uses a sealed class UiState<T> to represent all possible UI states:
UiState.kt
sealed class UiState<out T> {
    object Loading : UiState<Nothing>()
    data class Success<T>(val data: T) : UiState<T>()
    data class Error(val message: String, val exception: Throwable? = null) : UiState<Nothing>()
    object Empty : UiState<Nothing>()
}
This pattern provides:
  • Type Safety: Compile-time guarantees about state handling
  • Exhaustive When: Ensures all states are handled in UI
  • Reactive Updates: Automatic UI updates via StateFlow

​
Security & Authentication

TecMeli implements OAuth 2.0 with automatic token refresh:
1

Request Interception

Every request to the Mercado Libre API automatically includes the access token via AuthInterceptor
2

Authentication Challenge

When the server returns a 401 Unauthorized, the TokenAuthenticator intercepts the response
3

Token Refresh

A new token is requested synchronously from the auth endpoint
4

Automatic Retry

The original failed request is retried with the new token - completely transparent to the user
AuthInterceptor.kt
class AuthInterceptor @Inject constructor(
    private val tokenRepository: TokenRepository
) : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val originalRequest = chain.request()
        
        // Skip auth for token endpoint
        if (originalRequest.url.encodedPath.contains("oauth/token")) {
            return chain.proceed(originalRequest)
        }

        val token = tokenRepository.getAccessToken()
        val requestBuilder = originalRequest.newBuilder()
        
        token?.let {
            requestBuilder.addHeader("Authorization", "Bearer $it")
        }
        
        return chain.proceed(requestBuilder.build())
    }
}

​
Project Structure

com.alcalist.tecmeli/
├── core/               # Infrastructure (Network, DI, Utilities)
│   ├── di/             # Hilt Modules
│   ├── network/        # Executors, Interceptors, Logger
│   └── util/           # UiState, DateUtils
├── data/               # Data Layer Implementation
│   ├── mapper/         # DTO → Domain transformations
│   ├── remote/         # Retrofit APIs and DTOs
│   └── repository/     # Repository implementations
├── domain/             # Pure Business Logic
│   ├── model/          # Domain entities
│   ├── repository/     # Repository contracts (interfaces)
│   └── usecase/        # Use cases
└── ui/                 # Presentation Layer
    ├── navigation/     # Navigation setup
    ├── screen/         # Compose screens
    └── theme/          # Material 3 theming
TecMeli requires valid Mercado Libre API credentials to function. You’ll need to register your application on the Mercado Libre Developer Portal to obtain these credentials.

​
What’s Next?

Now that you understand what TecMeli is and its architecture, let’s get it running on your machine:

Installation

Set up your development environment and clone the project

Configuration

Configure API credentials and build the application

Build docs developers (and LLMs) love

Get started for freeTalk to us