Language

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Overview

• Multi-language support
• Content localization
• Language-based routing

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Installation

import "github.com/go-mizu/mizu/middlewares/language"

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Quick Start

app := mizu.New()

app.Use(language.New(language.Options{
    Supported: []string{"en", "es", "fr", "de"},
    Default:   "en",
}))

app.Get("/", func(c *mizu.Ctx) error {
    lang := language.Get(c)
    return c.JSON(200, map[string]string{"language": lang})
})

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Configuration

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Options

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Examples

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Basic Detection

app.Use(language.New(language.Options{
    Supported: []string{"en", "es", "fr"},
    Default:   "en",
}))

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From Query Parameter

// GET /page?lang=es
app.Use(language.New(language.Options{
    Supported: []string{"en", "es"},
    QueryKey:  "language",
}))

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Persist in Cookie

app.Use(language.New(language.Options{
    Supported:  []string{"en", "es", "fr"},
    CookieName: "preferred_language",
}))

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Language-Based Routing

app.Get("/:lang/page", func(c *mizu.Ctx) error {
    lang := c.Param("lang")
    // Validate and use language
    return c.JSON(200, getContent(lang))
})

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Detection Order

1. Query parameter (?lang=es)
2. Cookie (lang=es)
3. Accept-Language header
4. Default language

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API Reference

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Functions

// New creates language middleware
func New(opts Options) mizu.Middleware

// Get returns detected language
func Get(c *mizu.Ctx) string

// Set sets language preference
func Set(c *mizu.Ctx, lang string)

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Technical Details

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Implementation Architecture

1. Context Storage: Detected language is stored in the request context using a private contextKey type
2. Case-Insensitive Matching: All language comparisons are performed case-insensitively using lowercase normalization
3. Regional Support: Handles both base language codes (e.g., “en”) and regional variants (e.g., “en-US”, “en-GB”)
4. Quality-Based Parsing: Accept-Language header parsing respects quality values (q-values) for prioritization

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Key Components

• isSupported(): Validates if a language code exists in the supported languages map
• normalize(): Converts detected language codes to the exact format defined in supported languages
• parseAcceptLanguage(): Parses Accept-Language header with quality values, sorts by quality descending
• Path Prefix Handling: When enabled, strips the language prefix from the URL path (e.g., /fr/page becomes /page)

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Configuration Defaults

// Default values when not specified
QueryParam:  "lang"          // Query parameter name
CookieName:  "lang"          // Cookie name
Header:      "Accept-Language" // HTTP header
PathPrefix:  false           // Path prefix detection disabled
Default:     supported[0]    // First supported language

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Best Practices

• Support common language codes
• Provide language switcher UI
• Persist user preference
• Use ISO 639-1 codes (en, es, fr)

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Testing

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Related Middlewares

• timezone - Timezone detection
• vary - Vary headers