<script>
  import { quintOut } from 'svelte/easing';
  import { crossfade } from 'svelte/transition';
  import { flip } from 'svelte/animate';

  const [send, receive] = crossfade({
    duration: d => Math.sqrt(d * 200),

    fallback(node, params) {
      const style = getComputedStyle(node);
      const transform = style.transform === 'none' ? '' : style.transform;

      return {
        duration: 600,
        easing: quintOut,
        css: t => `
          transform: ${transform} scale(${t});
          opacity: ${t}
        `
      };
    }
  });

  let uid = 1;

  let todos = [
    { id: uid++, done: false, description: 'write some docs' },
    { id: uid++, done: false, description: 'start writing blog post' },
    { id: uid++, done: true,  description: 'buy some milk' },
    { id: uid++, done: false, description: 'mow the lawn' },
    { id: uid++, done: false, description: 'feed the turtle' },
    { id: uid++, done: false, description: 'fix some bugs' },
  ];

  function add(input) {
    const todo = {
      id: uid++,
      done: false,
      description: input.value
    };

    todos = [todo, ...todos];
    input.value = '';
  }

  function remove(todo) {
    todos = todos.filter(t => t !== todo);
  }

  function mark(todo, done) {
    todo.done = done;
    remove(todo);
    todos = todos.concat(todo);
  }
</script>

<div class='board'>
  <input
    placeholder="what needs to be done?"
    on:keydown={e => e.which === 13 && add(e.target)}
  >

  <div class='left'>
    <h2>todo</h2>
    {#each todos.filter(t => !t.done) as todo (todo.id)}
      <label
        in:receive="{{key: todo.id}}"
        out:send="{{key: todo.id}}"
        animate:flip
      >
        <input type=checkbox on:change={() => mark(todo, true)}>
        {todo.description}
        <button on:click="{() => remove(todo)}">remove</button>
      </label>
    {/each}
  </div>

  <div class='right'>
    <h2>done</h2>
    {#each todos.filter(t => t.done) as todo (todo.id)}
      <label
        class="done"
        in:receive="{{key: todo.id}}"
        out:send="{{key: todo.id}}"
        animate:flip
      >
        <input type=checkbox checked on:change={() => mark(todo, false)}>
        {todo.description}
        <button on:click="{() => remove(todo)}">remove</button>
      </label>
    {/each}
  </div>
</div>

<style>
  .board {
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-gap: 1em;
    max-width: 36em;
    margin: 0 auto;
  }

  .board > input {
    font-size: 1.4em;
    grid-column: 1/3;
  }

  h2 {
    font-size: 2em;
    font-weight: 200;
    user-select: none;
    margin: 0 0 0.5em 0;
  }

  label {
    position: relative;
    line-height: 1.2;
    padding: 0.5em 2.5em 0.5em 2em;
    margin: 0 0 0.5em 0;
    border-radius: 2px;
    user-select: none;
    border: 1px solid hsl(240, 8%, 70%);
    background-color:hsl(240, 8%, 93%);
    color: #333;
  }

  input[type="checkbox"] {
    position: absolute;
    left: 0.5em;
    top: 0.6em;
    margin: 0;
  }

  .done {
    border: 1px solid hsl(240, 8%, 90%);
    background-color:hsl(240, 8%, 98%);
  }

  button {
    position: absolute;
    top: 0;
    right: 0.2em;
    width: 2em;
    height: 100%;
    background: no-repeat 50% 50% url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath fill='%23676778' d='M12,2C17.53,2 22,6.47 22,12C22,17.53 17.53,22 12,22C6.47,22 2,17.53 2,12C2,6.47 6.47,2 12,2M17,7H14.5L13.5,6H10.5L9.5,7H7V9H17V7M9,18H15A1,1 0 0,0 16,17V10H8V17A1,1 0 0,0 9,18Z'%3E%3C/path%3E%3C/svg%3E");
    background-size: 1.4em 1.4em;
    border: none;
    opacity: 0;
    transition: opacity 0.2s;
    text-indent: -9999px;
    cursor: pointer;
  }

  label:hover button {
    opacity: 1;
  }
</style>

animation = (node: HTMLElement, { from: DOMRect, to: DOMRect } , params: any) => {
  delay?: number,
  duration?: number,
  easing?: (t: number) => number,
  css?: (t: number, u: number) => string,
  tick?: (t: number, u: number) => void
}

DOMRect {
  bottom: number,
  height: number,
  left: number,
  right: number,
  top: number,
  width: number,
  x: number,
  y: number
}

<!-- When `list` is reordered the animation will run-->
{#each list as item, index (item)}
  <li animate:flip>{item}</li>
{/each}