> ## Documentation Index
> Fetch the complete documentation index at: https://docs.go-mizu.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Slash

> Trailing slash handling middleware for consistent URLs.

## Overview

The `slash` middleware handles trailing slashes in URLs by adding or removing them with redirects. Use it for URL consistency and SEO.

## Installation

```go theme={null}
import "github.com/go-mizu/mizu/middlewares/slash"
```

## Quick Start

```go theme={null}
app := mizu.New()

// Add trailing slash: /about → /about/
app.Use(slash.Add())

// Remove trailing slash: /about/ → /about
app.Use(slash.Remove())
```

## Functions

| Function           | Description                          |
| ------------------ | ------------------------------------ |
| `Add()`            | Add trailing slash (301 redirect)    |
| `AddCode(code)`    | Add with custom status code          |
| `Remove()`         | Remove trailing slash (301 redirect) |
| `RemoveCode(code)` | Remove with custom status code       |

## Examples

### Add Trailing Slash

```go theme={null}
app.Use(slash.Add())
// /about    → 301 → /about/
// /contact  → 301 → /contact/
// /about/   → (no redirect)
// /         → (no redirect)
```

### Remove Trailing Slash

```go theme={null}
app.Use(slash.Remove())
// /about/   → 301 → /about
// /contact/ → 301 → /contact
// /about    → (no redirect)
// /         → (no redirect)
```

### Temporary Redirect

```go theme={null}
app.Use(slash.AddCode(302))     // Temporary redirect
app.Use(slash.RemoveCode(307))  // Preserve HTTP method
```

## Behavior

* Root path `/` is never modified
* Query strings are preserved
* Uses 301 (Permanent) by default

## Technical Details

The slash middleware implements trailing slash normalization through HTTP redirects. It provides four main functions that return middleware handlers:

### Implementation

* **Add()**: Wraps `AddCode()` with HTTP 301 (Moved Permanently) status
* **AddCode(code int)**: Returns middleware that checks if path lacks trailing slash and redirects to add it
* **Remove()**: Wraps `RemoveCode()` with HTTP 301 (Moved Permanently) status
* **RemoveCode(code int)**: Returns middleware that checks if path has trailing slash and redirects to remove it

### Internal Logic

1. **Path Extraction**: Reads the request URL path from `c.Request().URL.Path`
2. **Root Protection**: Always skips the root path `/` to prevent infinite redirects
3. **Slash Detection**: Uses `strings.HasSuffix(path, "/")` to check for trailing slash
4. **Target Construction**: Builds redirect URL by adding/removing trailing slash
5. **Query Preservation**: Appends `?` + `c.Request().URL.RawQuery` if query string exists
6. **Redirect Execution**: Calls `c.Redirect(code, target)` with specified status code
7. **Pass-through**: Calls `next(c)` if no redirect needed

### Performance Characteristics

* **Zero allocations** for paths that don't need redirection
* **Single string concatenation** for building redirect target
* **Early exit** for root path and paths already in correct format
* **No regular expressions** - uses simple string operations

## Best Practices

* Choose one style and be consistent
* Use 301 for permanent SEO benefit
* Apply early in middleware chain

## Testing

The slash middleware includes comprehensive test coverage for all functions and edge cases:

| Test Case                       | Description                                            | Expected Behavior                                     |
| ------------------------------- | ------------------------------------------------------ | ----------------------------------------------------- |
| Add - adds trailing slash       | Request to `/test` with `Add()` middleware             | Redirects to `/test/` with 301 status                 |
| Add - preserves query           | Request to `/test?foo=bar` with `Add()` middleware     | Redirects to `/test/?foo=bar` preserving query string |
| Add - skips root                | Request to `/` with `Add()` middleware                 | Returns 200 OK, no redirect performed                 |
| AddCode - custom status         | Request to `/test` with `AddCode(307)` middleware      | Redirects to `/test/` with 307 status                 |
| Remove - removes trailing slash | Request to `/test/` with `Remove()` middleware         | Redirects to `/test` with 301 status                  |
| Remove - preserves query        | Request to `/test/?foo=bar` with `Remove()` middleware | Redirects to `/test?foo=bar` preserving query string  |
| Remove - skips root             | Request to `/` with `Remove()` middleware              | Returns 200 OK, no redirect performed                 |
| RemoveCode - custom status      | Request to `/test/` with `RemoveCode(302)` middleware  | Redirects to `/test` with 302 status                  |

## Related Middlewares

* [redirect](/middlewares/redirect) - General redirects
* [rewrite](/middlewares/rewrite) - URL rewriting