v/vlib/x/vweb/README.md

# vweb - the V Web Server

A simple yet powerful web server with built-in routing, parameter handling, templating, and other
features.

## Features

- **Very fast** performance of C on the web.
- **Easy to deploy** just one binary file that also includes all templates. No need to install any
  dependencies.
- **Templates are precompiled** all errors are visible at compilation time, not at runtime.
- **Middleware** functionality similair to other big frameworks.
- **Controllers** to split up your apps logic.

## Quick Start

Run your vweb app with a live reload via `v -d vweb_livereload watch run .`

Now modifying any file in your web app (whether it's a .v file with the backend logic
or a compiled .html template file) will result in an instant refresh of your app
in the browser. No need to quit the app, rebuild it, and refresh the page in the browser!

## Deploying vweb apps

All the code, including HTML templates, is in one binary file. That's all you need to deploy.
Use the `-prod` flag when building for production.

## Getting Started

To start, you must import the module `x.vweb` and define a structure which will 
represent your app and a structure which will represent the context of a request.
These structures must be declared with the `pub` keyword.

**Example:**
```v
module main

import x.vweb

pub struct User {
pub mut:
	name string
	id   int
}

// Our context struct must embed `vweb.Context`!
pub struct Context {
	vweb.Context
pub mut:
	// In the context struct we store data that could be different
	// for each request. Like a User struct or a session id
	user       User
	session_id string
}

pub struct App {
pub:
	// In the app struct we store data that should be accessible by all endpoints.
	// For example a database or configuration values.
	secret_key string
}

// This is how endpoints are defined in vweb. This is the index route
pub fn (app &App) index(mut ctx Context) vweb.Result {
	return ctx.text('Hello V! The secret key is "${app.secret_key}"')
}

fn main() {
	mut app := &App{
		secret_key: 'secret'
	}
	// Pass the App and context type and start the web server on port 8080
	vweb.run[App, Context](mut app, 8080)
}
```

You can use the `App` struct for data you want to keep during the lifetime of your program,
or for data that you want to share between different routes.

A new `Context` struct is created every time a request is received, 
so it can contain different data for each request.

## Defining endpoints

To add endpoints to your web server, you must extend the `App` struct.
For routing you can either use auto-mapping of function names or specify the path as an attribute.
The function expects a parameter of your Context type and a response of the type `vweb.Result`.

**Example:**
```v ignore
// This endpoint can be accessed via http://server:port/hello
pub fn (app &App) hello(mut ctx Context) vweb.Result {
	return ctx.text('Hello')
}

// This endpoint can be accessed via http://server:port/foo
@['/foo']
pub fn (app &App) world(mut ctx Context) vweb.Result {
	return ctx.text('World')
}
```

### HTTP verbs

To use any HTTP verbs (or methods, as they are properly called),
such as `@[post]`, `@[get]`, `@[put]`, `@[patch]` or `@[delete]`
you can simply add the attribute before the function definition.

**Example:**

```v ignore
// only GET requests to http://server:port/world are handled by this method
@[get]
pub fn (app &App) world(mut ctx Context) vweb.Result {
	return ctx.text('World')
}

// only POST requests to http://server:port/product/create are handled by this method
@['/product/create'; post]
pub fn (app &App) create_product(mut ctx Context) vweb.Result {
	return ctx.text('product')
}
```

By default endpoints are marked as GET requests only. It is also possible to
add multiple HTTP verbs per endpoint.

**Example:**

```v ignore
// only GET and POST requests to http://server:port/login are handled by this method
@['/login'; get; post]
pub fn (app &App) login(mut ctx Context) vweb.Result {
	if ctx.req.method == .get {
		// show the login page on a GET request
		return ctx.html('<h1>Login page</h1><p>todo: make form</p>')
	} else {
		// request method is POST
		password := ctx.form['password']
		// validate password length
		if password.len < 12 {
			return ctx.text('password is too weak!')
		} else {
			// we receive a POST request, so we want to explicitly tell the browser
			// to send a GET request to the profile page.
			return ctx.redirect('/profile', .see_other)
		}
	}
}
```

### Routes with Parameters

Parameters are passed directly to an endpoint route using the colon sign `:`. The route
parameters are passed as arguments. V will cast the parameter to any of V's primitive types
(`string`, `int` etc,).

To pass a parameter to an endpoint, you simply define it inside an attribute, e. g.
`@['/hello/:user]`.
After it is defined in the attribute, you have to add it as a function parameter.

**Example:**

```v ignore
// V will pass the parameter 'user' as a string
          vvvv
@['/hello/:user']                             vvvv
pub fn (app &App) hello_user(mut ctx Context, user string) vweb.Result {
	return ctx.text('Hello ${user}')
}

// V will pass the parameter 'id' as an int
              vv
@['/document/:id']                              vv
pub fn (app &App) get_document(mut ctx Context, id int) vweb.Result {
	return ctx.text('Hello ${user}')
}
```

If we visit http://localhost:port/hello/vaesel we would see the text `Hello vaesel`.

### Routes with Parameter Arrays

If you want multiple parameters in your route and if you want to parse the parameters 
yourself, or you want a wildcard route, you can add `...`  after the `:` and name,
e.g. `@['/:path...']`.

This will match all routes after `'/'`. For example the url `/path/to/test` would give
`path = '/path/to/test'`.

```v ignore
         vvv
@['/:path...']                              vvvv
pub fn (app &App) wildcard(mut ctx Context, path string) vweb.Result {
	return ctx.text('URL path = "${path}"')
}
```

### Query, Form and Files

You have direct access to query values by accessing the `query` field on your context struct.
You are also able to access any formdata or files that were sent
with the request with the fields `.form` and `.files` respectively.

In the following example, visiting http://localhost:port/user?name=Vweb we 
will see the text `Hello Vweb!`. And if we access the route without the `name` parameter,
http://localhost:port/user, we will see the text `no user was found`, 

**Example:**
```v ignore
@['/user'; get]
pub fn (app &App) get_user_by_id(mut ctx Context) vweb.Result {
	user_name := ctx.query['name'] or {
		// we can exit early and send a different response if no `name` parameter was passed
		return ctx.text('no user was found')
	}

	return ctx.text('Hello ${user_name}!')
}
```

### Host
To restrict an endpoint to a specific host, you can use the `host` attribute
followed by a colon `:` and the host name. You can test the Host feature locally
by adding a host to the "hosts" file of your device.

**Example:**

```v ignore
@['/'; host: 'example.com']
pub fn (app &App) hello_web(mut ctx Context) vweb.Result {
	return app.text('Hello World')
}

@['/'; host: 'api.example.org']
pub fn (app &App) hello_api(mut ctx Context) vweb.Result {
	return ctx.text('Hello API')
}

// define the handler without a host attribute last if you have conflicting paths.
@['/']
pub fn (app &App) hello_others(mut ctx Context) vweb.Result {
	return ctx.text('Hello Others')
}
```

You can also [create a controller](#controller-with-hostname) to handle all requests from a specific
host in one app struct.

### Route Matching Order

Vweb will match routes in the order that you define endpoints.

**Example:**
```v ignore
@['/:path']
pub fn (app &App) with_parameter(mut ctx Context, path string) vweb.Result {
	return ctx.text('from with_parameter, path: "${path}"')
}

@['/normal']
pub fn (app &App) normal(mut ctx Context) vweb.Result {
	return ctx.text('from normal')
}
```

In this example we defined an endpoint with a parameter first. If we access our app
on the url http://localhost:port/normal we will not see `from normal`, but 
`from with_parameter, path: "normal"`.

### Custom not found page

You can implement a `not_found` endpoint that is called when a request is made and no
matching route is found to replace the default HTTP 404 not found page. This route
has to be defined on our Context struct.

**Example:**

``` v ignore
pub fn (mut ctx Context) not_found() vweb.Result {
	// set HTTP status 404
	ctx.res.set_status(.not_found)
	return ctx.html('<h1>Page not found!</h1>')
}
```

## Static files

Vweb also provides a way of handling static files. We can mount a folder at the root
of our web app, or at a custom route. To start using static files we have to embed
`vweb.StaticHandler` on our app struct.

**Example:**

Let's say you have the following file structure:
```
.
├── static/
│   ├── css/
│   │   └── main.css
│   └── js/
│       └── main.js
└── main.v
```

If we want all the documents inside the `static` sub-directory to be publicly accessible we can
use `handle_static`.

> **Note:**
> vweb will recursively search the folder you mount; all the files inside that folder
> will be publicly available.

*main.v*
```v
module main

import x.vweb

pub struct Context {
	vweb.Context
}

pub struct App {
	vweb.StaticHandler
}

fn main() {
	mut app := &App{}

	app.handle_static('static', false)!

	vweb.run[App, Context](mut app, 8080)
}
```

If we start the app with `v run main.v` we can access our `main.css` file at 
http://localhost:8080/static/css/main.css

### Mounting folders at specific locations

In the previous example the folder `static` was mounted at `/static`. We could also choose
to mount the static folder at the root of our app: everything inside the `static` folder
is available at `/`.

**Example:**
```v ignore
// change the second argument to `true` to mount a folder at the app root
app.handle_static('static', true)!
```
We can now access `main.css` directly at http://localhost:8080/css/main.css

It is also possible to mount the `static` folder at a custom path.

**Example:**
```v ignore
// mount the folder 'static' at path '/public', the path has to start with '/'
app.mount_static_folder_at('static', '/public')
```

If we run our app the `main.css` file is available at http://localhost:8080/public/main.css

### Dealing with MIME types

By default vweb will map the extension of a file to a MIME type. If any of your static file's
extensions do not have a default MIME type in vweb, vweb will throw an error and you
have to add your MIME type to `.static_mime_types` yourself.

**Example:**

Let's say you have the following file structure:
```
.
├── static/
│   └── file.what
└── main.v
```
```v ignore
app.handle_static('static', true)!
```
This code will throw an error, because vweb has no default MIME type for a `.what` file extension.
```
unkown MIME type for file extension ".what"
```
To fix this we have to provide a MIME type for the `.what` file extension:
```v ignore
app.static_mime_types['.what'] = 'txt/plain'
app.handle_static('static', true)!
```


## Middleware

Middleware in web development is (loosely defined) a hidden layer that sits between
what a user requests (the HTTP Request) and what a user sees (the HTTP Response).
We can use this middleware layer to provide "hidden" functionality to our apps endpoints.

To use vweb's middleware we have to embed `vweb.Middleware` on our app struct and provide
the type of which context struct should be used.

**Example:**
```v ignore
pub struct App {
	vweb.Middleware[Context]
}
```

### Use case

We could, for example, get the cookies for an HTTP request and check if the user has already 
accepted our cookie policy. Let's modify our Context struct to store whether the user has
accepted our policy or not.

**Example:**
```v ignore
pub struct Context {
	vweb.Context
pub mut:
	has_accepted_cookies bool
}
```

In vweb middleware functions take a `mut` parameter with the type of your context struct
and must return `bool`. We have full access to modify our Context struct!

The return value indicates to vweb whether it can continue or has to stop. If we send a 
response to the client in a middleware function vweb has to stop, so we return `false`.

**Example:**
```v ignore
pub fn check_cookie_policy(mut ctx Context) bool {
	// get the cookie
	cookie_value := ctx.get_cookie('accepted_cookies') or { '' }
	// check if the cookie has been set
	if cookie_value == 'true' {
		ctx.has_accepted_cookies = true
	}
	// we don't send a response, so we must return true
	return true
}
```

We can check this value in an endpoint and return a different response.

**Example:**
```v ignore
@['/only-cookies']
pub fn (app &App) only_cookie_route(mut ctx Context) vweb.Result {
	if ctx.has_accepted_cookies {
		return ctx.text('Welcome!')
	} else {
		return ctx.text('You must accept the cookie policy!')
	}
}
```

There is one thing left for our middleware to work: we have to register our `only_cookie_route`
function as middleware for our app. We must do this after the app is created and before the
app is started.

**Example:**
```v ignore
fn main() {
	mut app := &App{}

	// register middleware for all routes
	app.use(handler: only_cookie_route)

	// Pass the App and context type and start the web server on port 8080
	vweb.run[App, Context](mut app, 8080)
}
```

### Types of middleware

In the previous example we used so called "global" middleware. This type of middleware 
applies to every endpoint defined on our app struct; global. It is also possible
to register middleware for only a certain route(s).

**Example:**
```v ignore
// register middleware only for the route '/auth'
app.route_use('/auth', handler: auth_middleware)
// register middleware only for the route '/documents/' with a parameter
// e.g. '/documents/5'
app.route_use('/documents/:id')
// register middleware with a parameter array. The middleware will be registered
// for all routes that start with '/user/' e.g. '/user/profile/update'
app.route_use('/user/:path...')
```

### Evaluation moment

By default the registered middleware functions are executed *before* a method on your
app struct is called. You can also change this behaviour to execute middleware functions
*after* a method on your app struct is called, but before the response is sent!

**Example:**
```v ignore
pub fn modify_headers(mut ctx Context) bool {
	// add Content-Language: 'en-US' header to each response
	ctx.res.header.add(.content_language, 'en-US')
	return true
}
```
```v ignore
app.use(handler: modify_headers, after: true)
```

#### When to use which type

You could use "before" middleware to check and modify the HTTP request and you could use
"after" middleware to validate the HTTP response that will be sent or do some cleanup.

Anything you can do in "before" middleware, you can do in "after" middleware.

### Evaluation order

Vweb will handle requests in the following order:

1. Execute global "before" middleware
2. Execute "before" middleware that matches the requested route
3. Execute the endpoint handler on your app struct
4. Execute global "after" middleware
5. Execute "after" middleware that matches the requested route

In each step, except for step `3`, vweb will evaluate the middleware in the order that 
they are registered; when you call `app.use` or `app.route_use`. 

### Early exit

If any middleware sends a response (and thus must return `false`) vweb will not execute any
other middleware, or the endpoint method, and immediately send the response.

**Example:**
```v ignore
pub fn early_exit(mut ctx Context) bool {
	ctx.text('early exit')
	// we send a response from middleware, so we have to return false
	return false
}

pub fn logger(mut ctx Context) bool {
	println('received request for "${ctx.req.url}"')
	return true
}
```
```v ignore
app.use(handler: early_exit)
app.use(handler: logger)
```

Because we register `early_exit` before `logger` our logging middleware will never be executed!

## Controllers

Controllers can be used to split up your app logic so you are able to have one struct
per "route group".  E.g. a struct `Admin` for urls starting with `'/admin'` and a struct `Foo`
for urls starting with `'/foo'`. 

To use controllers we have to embed `vweb.Controller` on
our app struct and when we register a controller we also have to specify
what the type of the context struct will be. That means that is is possible
to have a different context struct for each controller and the main app struct.

**Example:**
```v
module main

import x.vweb

pub struct Context {
	vweb.Context
}

pub struct App {
	vweb.Controller
}

// this endpoint will be available at '/'
pub fn (app &App) index(mut ctx Context) vweb.Result {
	return ctx.text('from app')
}

pub struct Admin {}

// this endpoint will be available at '/admin/'
pub fn (app &Admin) index(mut ctx Context) vweb.Result {
	return ctx.text('from admin')
}

pub struct Foo {}

// this endpoint will be available at '/foo/'
pub fn (app &Foo) index(mut ctx Context) vweb.Result {
	return ctx.text('from foo')
}

fn main() {
	mut app := &App{}

	// register the controllers the same way as how we start a vweb app
	mut admin_app := &Admin{}
	app.register_controller[Admin, Context]('/admin', mut admin_app)!

	mut foo_app := &Foo{}
	app.register_controller[Foo, Context]('/foo', mut foo_app)!

	vweb.run[App, Context](mut app, 8080)
}
```

You can do everything with a controller struct as with a regular `App` struct.
Register middleware, add static files and you can even register other controllers!

### Routing

Any route inside a controller struct is treated as a relative route to its controller namespace.

```v ignore
@['/path']
pub fn (app &Admin) path(mut ctx Context) vweb.Result {
    return ctx.text('Admin')
}
```
When we registerted the controller with 
`app.register_controller[Admin, Context]('/admin', mut admin_app)!` 
we told vweb that the namespace of that controller is `'/admin'` so in this example we would
see the text "Admin" if we navigate to the url `'/admin/path'`.

Vweb doesn't support duplicate routes, so if we add the following
route to the example the code will produce an error.

```v ignore
@['/admin/path']
pub fn (app &App) admin_path(mut ctx Context) vweb.Result {
    return ctx.text('Admin overwrite')
}
```
There will be an error, because the controller `Admin` handles all routes starting with
`'/admin'`: the endpoint `admin_path` is unreachable.

### Controller with hostname

You can also set a host for a controller. All requests coming to that host will be handled
by the controller.

**Example:**
```v ignore
struct Example {}

// You can only access this route at example.com: http://example.com/
pub fn (app &Example) index(mut ctx Context) vweb.Result {
	return ctx.text('Example')
}
```
```v ignore
mut example_app := &Example{}
// set the controllers hostname to 'example.com' and handle all routes starting with '/',
// we handle requests with any route to 'example.com'
app.register_controller[Example, Context]('example.com', '/', mut example_app)!
```

## Context Methods

vweb has a number of utility methods that make it easier to handle requests and send responses.
These methods are available on `vweb.Context` and directly on your own context struct if you
embed `vweb.Context`. Below are some of te most used methods, look at the 
[standard library documentation](https://modules.vlang.io/) to see them all.

### Request methods

You can directly access the HTTP request on the `.req` field.

#### Get request headers

**Example:**
```v ignore
pub fn (app &App) index(mut ctx Context) vweb.Result {
	content_length := ctx.get_header(.content_length) or { '0' }
	// get custom header
	custom_header := ctx.get_custom_header('X-HEADER') or { '' }
	// ...
}
```

#### Get a cookie

**Example:**
```v ignore
pub fn (app &App) index(mut ctx Context) vweb.Result {
	cookie_val := ctx.get_cookie('token') or { '' }
	// ...
}
```

### Response methods

You can directly modify the HTTP response by changing the `res` field, 
which is of the type `http.Response`.

#### Send response with different MIME types

```v ignore
// send response HTTP_OK with content-type `text/html`
ctx.html('<h1>Hello world!</h1>')
// send response HTTP_OK with content-type `text/plain`
ctx.text('Hello world!')
// stringify the object and send response HTTP_OK with content-type `application/json`
ctx.json(User{
	name: 'test'
	age: 20
})
```

#### Sending files

**Example:**
```v ignore
pub fn (app &App) file_response(mut ctx Context) vweb.Result {
	// send the file 'image.png' in folder 'data' to the user
	return ctx.file('data/image.png')
}
```

#### Set response headers

**Example:**
```v ignore
pub fn (app &App) index(mut ctx Context) vweb.Result {
	ctx.set_header(.accept, 'text/html')
	// set custom header
	ctx.set_custom_header('X-HEADER', 'my-value')!
	// ...
}
```

#### Set a cookie

**Example:**
```v ignore
pub fn (app &App) index(mut ctx Context) vweb.Result {
	ctx.set_cookie(http.Cookie{
		name: 'token'
		value: 'true'
		path: '/'
		secure: true
		http_only: true
	})
	// ...
}
```

#### Redirect

You must pass the type of redirect to vweb:
- `moved_permanently` HTTP code 301
- `found` HTTP code 302
- `see_other` HTTP code 303
- `temporary_redirect` HTTP code 307
- `permanent_redirect` HTTP code 308

**Common use cases:**

If you want to change the request method, for example when you receive a post request and
want to redirect to another page via a GET request, you should use `see_other`. If you want
the HTTP method to stay the same you should use `found` generally speaking.

**Example:**
```v ignore
pub fn (app &App) index(mut ctx Context) vweb.Result {
	token := ctx.get_cookie('token') or { '' }
	if token == '' {
		// redirect the user to '/login' if the 'token' cookie is not set
		// we explicitly tell the browser to send a GET request
		return ctx.redirect('/login', .see_other)
	} else {
		return ctx.text('Welcome!')
	}
}
```

#### Sending error responses

**Example:**
```v ignore
pub fn (app &App) login(mut ctx Context) vweb.Result {
	if username := ctx.form['username'] {
		return ctx.text('Hello "${username}"')
	} else {
		// send an HTTP 400 Bad Request response with a message
		return ctx.request_error('missing form value "username"')
	}
}
```

You can also use `ctx.server_error(msg string)` to send an HTTP 500 internal server
error with a message.

## Advanced usage

If you need more controll over the TCP connection with a client, for example when 
you want to keep the connection open. You can call `ctx.takeover_conn`.

When this function is called you are free to do anything you want with the TCP
connection and vweb will not interfere. This means that we are responsible for
sending a response over the connection and closing it.

### Empty Result

Sometimes you want to send the response in another thread, for example when using 
[Server Sent Events](sse/README.md). When you are sure that a response will be sent
over the TCP connection you can return `vweb.no_result()`. This function does nothinng
and returns an empty `vweb.Result` struct, letting vweb know that we sent a response ourself.

> **Note:**
> It is important to call `ctx.takeover_conn` before you spawn a thread

**Example:**
```v
module main

import net
import time
import x.vweb

pub struct Context {
	vweb.Context
}

pub struct App {}

pub fn (app &App) index(mut ctx Context) vweb.Result {
	return ctx.text('hello!')
}

@['/long']
pub fn (app &App) long_response(mut ctx Context) vweb.Result {
	// let vweb know that the connection should not be closed
	ctx.takeover_conn()
	// use spawn to handle the connection in another thread
	// if we don't the whole web server will block for 10 seconds,
	// since vweb is singlethreaded
	spawn handle_connection(mut ctx.conn)
	// we will send a custom response ourself, so we can safely return an empty result
	return vweb.no_result()
}

fn handle_connection(mut conn net.TcpConn) {
	defer {
		conn.close() or {}
	}
	// block for 10 second
	time.sleep(time.second * 10)
	conn.write_string('HTTP/1.1 200 OK\r\nContent-type: text/html\r\nContent-length: 15\r\n\r\nHello takeover!') or {}
}

fn main() {
	mut app := &App{}
	vweb.run[App, Context](mut app, 8080)
}
```