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https://github.com/rawhat/mist

gleam HTTP server. because it glistens on a web
https://github.com/rawhat/mist

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gleam HTTP server. because it glistens on a web

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# mist



[![Package Version](https://img.shields.io/hexpm/v/mist)](https://hex.pm/packages/mist)

[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/mist/)



## A glistening Gleam web server.



To follow along with the example below, you can create a new project and add the

dependencies as follows:



```sh

$ gleam new 

$ cd 

$ gleam add mist gleam_erlang gleam_http gleam_otp

```



The main entrypoints for your application are `mist.start_http` and

`mist.start_https`. The argument to these functions is generated from the

opaque `Builder` type. It can be constructed with the `mist.new` function, and

fed updated configuration options with the associated methods (demonstrated

in the examples below).



```gleam

import gleam/bytes_builder

import gleam/erlang/process

import gleam/http/request.{type Request}

import gleam/http/response.{type Response}

import gleam/io

import gleam/iterator

import gleam/option.{None, Some}

import gleam/otp/actor

import gleam/result

import gleam/string

import mist.{type Connection, type ResponseData}



pub fn main() {

  // These values are for the Websocket process initialized below

  let selector = process.new_selector()

  let state = Nil



  let not_found =

    response.new(404)

    |> response.set_body(mist.Bytes(bytes_builder.new()))



  let assert Ok(_) =

    fn(req: Request(Connection)) -> Response(ResponseData) {

      case request.path_segments(req) {

        ["ws"] ->

          mist.websocket(

            request: req,

            on_init: fn(_conn) { #(state, Some(selector)) },

            on_close: fn(_state) { io.println("goodbye!") },

            handler: handle_ws_message,

          )

        ["echo"] -> echo_body(req)

        ["chunk"] -> serve_chunk(req)

        ["file", ..rest] -> serve_file(req, rest)

        ["form"] -> handle_form(req)



        _ -> not_found

      }

    }

    |> mist.new

    |> mist.port(3000)

    |> mist.start_http



  process.sleep_forever()

}



pub type MyMessage {

  Broadcast(String)

}



fn handle_ws_message(state, conn, message) {

  case message {

    mist.Text("ping") -> {

      let assert Ok(_) = mist.send_text_frame(conn, "pong")

      actor.continue(state)

    }

    mist.Text(_) | mist.Binary(_) -> {

      actor.continue(state)

    }

    mist.Custom(Broadcast(text)) -> {

      let assert Ok(_) = mist.send_text_frame(conn, text)

      actor.continue(state)

    }

    mist.Closed | mist.Shutdown -> actor.Stop(process.Normal)

  }

}



fn echo_body(request: Request(Connection)) -> Response(ResponseData) {

  let content_type =

    request

    |> request.get_header("content-type")

    |> result.unwrap("text/plain")



  mist.read_body(request, 1024 * 1024 * 10)

  |> result.map(fn(req) {

    response.new(200)

    |> response.set_body(mist.Bytes(bytes_builder.from_bit_array(req.body)))

    |> response.set_header("content-type", content_type)

  })

  |> result.lazy_unwrap(fn() {

    response.new(400)

    |> response.set_body(mist.Bytes(bytes_builder.new()))

  })

}



fn serve_chunk(_request: Request(Connection)) -> Response(ResponseData) {

  let iter =

    ["one", "two", "three"]

    |> iterator.from_list

    |> iterator.map(bytes_builder.from_string)



  response.new(200)

  |> response.set_body(mist.Chunked(iter))

  |> response.set_header("content-type", "text/plain")

}



fn serve_file(

  _req: Request(Connection),

  path: List(String),

) -> Response(ResponseData) {

  let file_path = string.join(path, "/")



  // Omitting validation for brevity

  mist.send_file(file_path, offset: 0, limit: None)

  |> result.map(fn(file) {

    let content_type = guess_content_type(file_path)

    response.new(200)

    |> response.prepend_header("content-type", content_type)

    |> response.set_body(file)

  })

  |> result.lazy_unwrap(fn() {

    response.new(404)

    |> response.set_body(mist.Bytes(bytes_builder.new()))

  })

}



fn handle_form(req: Request(Connection)) -> Response(ResponseData) {

  let _req = mist.read_body(req, 1024 * 1024 * 30)

  response.new(200)

  |> response.set_body(mist.Bytes(bytes_builder.new()))

}



fn guess_content_type(_path: String) -> String {

  "application/octet-stream"

}

```



## Streaming request body



```

NOTE:  This is a new feature, and I may have made some mistakes.  Please let me

know if you run into anything :)

```



When handling file uploads or `multipart/form-data`, you probably don't want to

load the whole file into memory. Previously, the only options in `mist` were to

accept bodies up to `N` bytes, or read the entire body.



Now, there is a `mist.stream` function which takes a `Request(Connection)` that

gives you back a function to start reading chunks. This function will return:



```gleam

pub type Chunk {

  Chunk(data: BitString, consume: fn(Int) -> Chunk)

  Done

}

```



NOTE: You must only call this once on the `Request(Connection)`. Since it's

reading data from the socket, this is a mutable action. The name `consume` was

chosen to hopefully make that more clear.



### Example



```gleam

// Replacing the named function in the application example above

fn handle_form(req: Request(Connection)) -> Response(ResponseData) {

  let assert Ok(consume) = mist.stream(req)

  // NOTE:  This is a little misleading, since `Iterator`s can be replayed.

  // However, this will only be running this once.

  let content =

    iterator.unfold(

      consume,

      fn(consume) {

        // Reads up to 1024 bytes from the request

        let res = consume(1024)

        case res {

          // The error will not be bubbled up to the iterator here. If either

          // we've read all the body, or we see an error, the iterator finishes

          Ok(mist.Done) | Error(_) -> iterator.Done

          // We read some data. It may be less than the specific amount above if

          // we have consumed all of the body. You'll still need to call it

          // again to ensure, since with `chunked` encoding, we need to check

          // for the last chunk.

          Ok(mist.Chunk(data, consume)) -> {

            iterator.Next(bit_builder.from_bit_string(data), consume)

          }

        }

      },

    )

  // For fun, respond with `chunked` encoding of the same iterator

  response.new(200)

  |> response.set_body(mist.Chunked(content))

}

```