gleamkit

WIP: Very early development, missing consistency and features

This experimental repo is a starter kit for writing HTTP APIs in Gleam based on wisp, aiming to provide a simple and opinionated setup that is production-ready (even though Gleam is still a very cutting edge language).

I am aware that Gleam has the "start simple, refactor later" philosophy (just like Golang). This starter is inspired by my own blaze, only giving the user the essentials for real, production use without going crazy on the structure.

Features

• Simple, opinionated, production ready structure
• Pattern matching based routing
• Handy body decoding and validation
• Automatic human readable errors on decoding failures
• Custom HTTP API error handling
• Request and reply utilities
• Env variables and app context configuration

Snippets

Routing:

pub fn handle_request(req: Request, _ctx: AppContext) -> Response {
  use req <- middleware.default_middleware(req)
  use req <- cors.wisp_middleware(req, default_cors())

  case req.method, wisp.path_segments(req) {
    Get, [] -> ok()
    Get, ["todos"] -> todos.handle_get_todos()
    Post, ["todos"] -> todos.handle_create_todo(req)
    Get, ["todos", id] -> todos.handle_get_todo(req, id)
    _, _ -> route_not_found()
  }
}

Body validation with automatic validation errors (found in common/core module):

pub fn handle_create_todo(req: Request) -> Response {
    // Handy direct decoding with custom error handling
    use new_todo <- decode_body(req, todos.decode_new_todo)

    let res = todos.Todo(4, new_todo.title, False)

    // Reply with status code and JSON data
    reply_data(201, todos.encode_todo(res))
}

Easy API custom error handling:

pub fn handle_get_todo(_req: Request, id: String) -> Response {
  // Early reply utility function to handle errors
  use todo_id <- unpack_or_reply(int.parse(id), fn(_) {
    // Reply with a detailed API error
    reply_error_detailed(BadRequest, "Invalid todo ID")
  })

  let item = list.find(todos, fn(t) { t.id == todo_id })

  // Match on the result and reply with data or API error
  case item {
    Ok(item) -> reply_data(200, todos.encode_todo(item))
    Error(_) -> reply_error(NotFound)
  }
}

Default HTTP errors (like NotFound) can be found in common/errors module, and you can append a detail message to them using the reply_error_detailed function.

Build and run

make  # Build the project
make run   # Run the service