Device Detection

The mobile middleware automatically parses device information from HTTP headers and User-Agent strings, providing rich context about the client device in your handlers.

Quick Start

import "github.com/go-mizu/mizu/mobile"

app := mizu.New()

// Add mobile middleware
app.Use(mobile.New())

app.Get("/api/profile", func(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    return c.JSON(200, map[string]any{
        "platform":    device.Platform.String(),
        "os_version":  device.OSVersion,
        "app_version": device.AppVersion,
        "device_id":   device.DeviceID,
        "model":       device.DeviceModel,
        "timezone":    device.Timezone,
        "locale":      device.Locale,
    })
})

The Device Struct

type Device struct {
    // Platform is the operating system (ios, android, windows, etc.)
    Platform Platform

    // OSVersion is the OS version (e.g., "17.0", "14.0")
    OSVersion string

    // AppVersion is the client app version (e.g., "1.2.3")
    AppVersion string

    // AppBuild is the build number (e.g., "123", "2024.01.15")
    AppBuild string

    // DeviceID is a unique device identifier
    DeviceID string

    // DeviceModel is the device model (e.g., "iPhone15,2", "Pixel 8")
    DeviceModel string

    // Locale is the device locale (e.g., "en-US", "ja-JP")
    Locale string

    // Timezone is the IANA timezone (e.g., "America/New_York")
    Timezone string

    // PushToken is the push notification token (if provided)
    PushToken string

    // PushProvider is APNS, FCM, or WNS
    PushProvider PushProvider

    // UserAgent is the raw User-Agent header
    UserAgent string
}

Platform Types

The Platform type represents the client operating system:

const (
    PlatformIOS     Platform = "ios"
    PlatformAndroid Platform = "android"
    PlatformWindows Platform = "windows"
    PlatformMacOS   Platform = "macos"
    PlatformWeb     Platform = "web"
    PlatformUnknown Platform = "unknown"
)

Platform Methods

// String returns the platform as a string
device.Platform.String() // "ios"

// IsMobile returns true for iOS and Android
device.Platform.IsMobile() // true

// IsDesktop returns true for Windows and macOS
device.Platform.IsDesktop() // false

// IsNative returns true for all except web and unknown
device.Platform.IsNative() // true

Header Parsing

The middleware parses these standard headers:

Header	Field	Example
`X-Device-ID`	DeviceID	`550e8400-e29b-41d4-a716-446655440000`
`X-App-Version`	AppVersion	`2.1.0`
`X-App-Build`	AppBuild	`2024.01.15`
`X-Device-Model`	DeviceModel	`iPhone15,2`
`X-Platform`	Platform	`ios`
`X-OS-Version`	OSVersion	`17.0`
`X-Timezone`	Timezone	`America/New_York`
`X-Locale`	Locale	`en-US`
`X-Push-Token`	PushToken	`abc123...`

Platform Detection Priority

Explicit header - X-Platform header takes priority
User-Agent parsing - Falls back to User-Agent analysis
Unknown - Default if no detection succeeds

// Header takes priority
// Request: X-Platform: ios
device.Platform // PlatformIOS

// Falls back to User-Agent
// Request: User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_0...)
device.Platform // PlatformIOS

Configuration Options

Basic Options

app.Use(mobile.WithOptions(mobile.Options{
    // Require X-Device-ID header
    RequireDeviceID: true,

    // Require X-App-Version header
    RequireAppVersion: true,

    // Skip specific paths
    SkipPaths: []string{"/health", "/metrics"},
}))

Platform Restrictions

app.Use(mobile.WithOptions(mobile.Options{
    // Only allow iOS and Android
    AllowedPlatforms: []mobile.Platform{
        mobile.PlatformIOS,
        mobile.PlatformAndroid,
    },
}))

Minimum App Version

app.Use(mobile.WithOptions(mobile.Options{
    RequireAppVersion: true,
    MinAppVersion:     "1.5.0",
}))

Requests with versions below 1.5.0 receive:

{
  "code": "upgrade_required",
  "message": "Please update to the latest version",
  "details": {
    "current_version": "1.4.0",
    "minimum_version": "1.5.0"
  }
}

With response header: X-Min-App-Version: 1.5.0

Custom Error Handlers

app.Use(mobile.WithOptions(mobile.Options{
    RequireDeviceID: true,

    OnMissingHeader: func(c *mizu.Ctx, header string) error {
        return c.JSON(400, map[string]string{
            "error": "Missing header: " + header,
        })
    },

    OnUnsupportedPlatform: func(c *mizu.Ctx, platform mobile.Platform) error {
        return c.JSON(400, map[string]string{
            "error": "Platform not supported: " + platform.String(),
        })
    },

    OnOutdatedApp: func(c *mizu.Ctx, version, minimum string) error {
        return c.JSON(426, map[string]any{
            "error":           "Update required",
            "current_version": version,
            "minimum_version": minimum,
            "store_url":       "https://apps.apple.com/app/id123",
        })
    },
}))

Performance Optimization

app.Use(mobile.WithOptions(mobile.Options{
    // Skip User-Agent parsing for performance
    // Only use explicit headers
    SkipUserAgent: true,
}))

Using Device Context

Access in Handlers

func handler(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    // Device may be nil if middleware not applied
    if device == nil {
        return c.JSON(400, "Device context not available")
    }

    // Use device info
    log.Printf("Request from %s app v%s",
        device.Platform, device.AppVersion)

    return c.JSON(200, data)
}

Platform-Specific Logic

func handler(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    response := map[string]any{
        "features": getFeatures(),
    }

    switch device.Platform {
    case mobile.PlatformIOS:
        response["store_url"] = "https://apps.apple.com/app/id123"
        response["review_url"] = "https://apps.apple.com/app/id123?action=write-review"

    case mobile.PlatformAndroid:
        response["store_url"] = "https://play.google.com/store/apps/details?id=com.example"
        response["review_url"] = "market://details?id=com.example"

    case mobile.PlatformWeb:
        response["signup_url"] = "https://example.com/signup"
    }

    return c.JSON(200, response)
}

Version-Based Features

func handler(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    features := map[string]bool{
        "dark_mode": true,
        "biometrics": true,
    }

    // Feature requires app version 2.0+
    if mobile.CompareVersions(device.AppVersion, "2.0.0") >= 0 {
        features["widgets"] = true
    }

    // Feature requires iOS 16+
    if device.Platform == mobile.PlatformIOS {
        if mobile.CompareVersions(device.OSVersion, "16.0") >= 0 {
            features["live_activities"] = true
        }
    }

    return c.JSON(200, features)
}

Timezone-Aware Responses

func handler(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    loc, err := time.LoadLocation(device.Timezone)
    if err != nil {
        loc = time.UTC
    }

    events := getEvents()
    for i := range events {
        events[i].LocalTime = events[i].Time.In(loc).Format(time.RFC3339)
    }

    return c.JSON(200, events)
}

Localized Responses

func handler(c *mizu.Ctx) error {
    device := mobile.DeviceFromCtx(c)

    // Parse locale
    lang := "en"
    if device.Locale != "" {
        lang = strings.Split(device.Locale, "-")[0]
    }

    messages := map[string]map[string]string{
        "en": {"welcome": "Welcome!"},
        "es": {"welcome": "Bienvenido!"},
        "ja": {"welcome": "ようこそ!"},
    }

    msg, ok := messages[lang]
    if !ok {
        msg = messages["en"]
    }

    return c.JSON(200, msg)
}

User-Agent Patterns

The middleware recognizes these User-Agent patterns: iOS:

Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X)...
Mozilla/5.0 (iPad; CPU OS 17_0 like Mac OS X)...

Android:

Mozilla/5.0 (Linux; Android 14; Pixel 8)...

Windows:

Mozilla/5.0 (Windows NT 10.0; Win64; x64)...

macOS:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7)...

Client Implementation

iOS (Swift)

extension URLRequest {
    mutating func addMizuHeaders(deviceId: String) {
        setValue(deviceId, forHTTPHeaderField: "X-Device-ID")
        setValue(Bundle.main.appVersion, forHTTPHeaderField: "X-App-Version")
        setValue(Bundle.main.buildNumber, forHTTPHeaderField: "X-App-Build")
        setValue(UIDevice.current.modelIdentifier, forHTTPHeaderField: "X-Device-Model")
        setValue("ios", forHTTPHeaderField: "X-Platform")
        setValue(UIDevice.current.systemVersion, forHTTPHeaderField: "X-OS-Version")
        setValue(TimeZone.current.identifier, forHTTPHeaderField: "X-Timezone")
        setValue(Locale.current.identifier, forHTTPHeaderField: "X-Locale")
    }
}

extension Bundle {
    var appVersion: String {
        infoDictionary?["CFBundleShortVersionString"] as? String ?? "0.0.0"
    }
    var buildNumber: String {
        infoDictionary?["CFBundleVersion"] as? String ?? "0"
    }
}

Android (Kotlin)

class MizuHeaderInterceptor(
    private val context: Context,
    private val deviceId: String
) : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val request = chain.request().newBuilder()
            .header("X-Device-ID", deviceId)
            .header("X-App-Version", BuildConfig.VERSION_NAME)
            .header("X-App-Build", BuildConfig.VERSION_CODE.toString())
            .header("X-Device-Model", Build.MODEL)
            .header("X-Platform", "android")
            .header("X-OS-Version", Build.VERSION.RELEASE)
            .header("X-Timezone", TimeZone.getDefault().id)
            .header("X-Locale", Locale.getDefault().toLanguageTag())
            .build()

        return chain.proceed(request)
    }
}

Flutter (Dart)

class MizuClient {
  final String deviceId;
  final PackageInfo packageInfo;

  Map<String, String> get headers => {
    'X-Device-ID': deviceId,
    'X-App-Version': packageInfo.version,
    'X-App-Build': packageInfo.buildNumber,
    'X-Platform': Platform.operatingSystem,
    'X-OS-Version': Platform.operatingSystemVersion,
    'X-Timezone': DateTime.now().timeZoneName,
    'X-Locale': Platform.localeName,
  };
}

React Native (TypeScript)

import DeviceInfo from 'react-native-device-info';
import { Platform, NativeModules } from 'react-native';

const getMizuHeaders = async () => ({
  'X-Device-ID': await DeviceInfo.getUniqueId(),
  'X-App-Version': DeviceInfo.getVersion(),
  'X-App-Build': DeviceInfo.getBuildNumber(),
  'X-Device-Model': DeviceInfo.getModel(),
  'X-Platform': Platform.OS,
  'X-OS-Version': Platform.Version.toString(),
  'X-Timezone': Intl.DateTimeFormat().resolvedOptions().timeZone,
  'X-Locale': NativeModules.SettingsManager?.settings?.AppleLocale
    ?? NativeModules.I18nManager?.localeIdentifier
    ?? 'en-US',
});

Next Steps

API Versioning

Manage API versions with deprecation warnings

Structured Errors

Return consistent error responses

Push Notifications

Handle push token registration

API Reference

Complete API documentation

Getting Started

Core Concepts

Backend Features

Native Platforms

Cross-Platform

Web & Games

Deployment

Templates

Reference

Quick Start

The Device Struct

Platform Types

Platform Methods

Header Parsing

Platform Detection Priority

Configuration Options

Basic Options

Platform Restrictions

Minimum App Version

Custom Error Handlers

Performance Optimization

Using Device Context

Access in Handlers

Platform-Specific Logic

Version-Based Features

Timezone-Aware Responses

Localized Responses

User-Agent Patterns

Client Implementation

iOS (Swift)

Android (Kotlin)

Flutter (Dart)

React Native (TypeScript)

Next Steps

API Versioning

Structured Errors

Push Notifications

API Reference

Getting Started

Core Concepts

Backend Features

Native Platforms

Cross-Platform

Web & Games

Deployment

Templates

Reference

Documentation Index

​Quick Start

​The Device Struct

​Platform Types

​Platform Methods

​Header Parsing

​Platform Detection Priority

​Configuration Options

​Basic Options

​Platform Restrictions

​Minimum App Version

​Custom Error Handlers

​Performance Optimization

​Using Device Context

​Access in Handlers

​Platform-Specific Logic

​Version-Based Features

​Timezone-Aware Responses

​Localized Responses

​User-Agent Patterns

​Client Implementation

​iOS (Swift)

​Android (Kotlin)

​Flutter (Dart)

​React Native (TypeScript)

​Next Steps

API Versioning

Structured Errors

Push Notifications

API Reference

Quick Start

The Device Struct

Platform Types

Platform Methods

Header Parsing

Platform Detection Priority

Configuration Options

Basic Options

Platform Restrictions

Minimum App Version

Custom Error Handlers

Performance Optimization

Using Device Context

Access in Handlers

Platform-Specific Logic

Version-Based Features

Timezone-Aware Responses

Localized Responses

User-Agent Patterns

Client Implementation

iOS (Swift)

Android (Kotlin)

Flutter (Dart)

React Native (TypeScript)

Next Steps