Code from OpaDevCamp #1

cmd

opa test.opa hello.opa --database mongo

hello.opa

import stdlib.core.web.resource

database todoList {
    Todolist.todolist /todos
}

todo_urls = parser {
        | "/todo"(.*)  : Resource.page("foo", 
                                       <h1>Hello</h1>
                                       <label for="todo">Todo:</label>
                                       <input id="todo" onnewline={
                                           function (_) { 
                                               item = Dom.get_value(#todo) ;
                                               /todoList/todos/items <+ item
                                               #todos =+ <li>{ item }</li>
                                           }
                                       }>What's next</input>
                                       <ul id="todos">
                                       { 
                                           List.map(function(item) { <li> { item } </li> }, /todoList/todos/items)
                                       }
                                       </ul>
                                      )
    }

Server.start( 
    Server.http,   
    { custom:todo_urls }
)

test.opa

type Todolist.todolist = { list(string) items }

module Todolist {
   
    function add(list, item) {
        { items : List.add(item,list.items) }
    }

    function size(list) {
        List.length(list.items)
    }

    function remove(list, item) {
        {items: List.filter(function(anItem) { anItem != item }, list.items)}
    }
}

emptyTodolist = { items : [] }
nonEmptyTodoList = { items : ["do something"] }
twoElementsTodoList = { items : ["do something", "do something else"] }

@assert(Todolist.size(Todolist.add(emptyTodolist, "do something")) == 1)
@assert(Todolist.size(Todolist.add(nonEmptyTodoList, "do something else")) == 2)
@assert(Todolist.size(Todolist.remove(nonEmptyTodoList, "do something")) == 0)
@assert(Todolist.remove(twoElementsTodoList, "do something else") == { items: ["do something"]})