How to set the max-height of a flex container for a specific item?

Question

.container {
      padding: 10px;
      display: flex;
      width: 80vw;
      justify-content: space-between;
      margin: 0 auto;
      margin-top: 20px;
      background: green;
  }

  .item_1 {
      max-height: 100%;
      /*max-height: 1200px;(it can be >.item_2)*/
      width: 200px;
      overflow-y: scroll;
      background: orange;

  }

  .item_2 {
      height: 800px;
      width: 800px;
      background: orange
  }

<div>
    <div class='container'>
        <div class='item_1'></div>
        <div class='item_2'></div>
    </div>
</div>

I need to set max-height of .container(green on image) == height of .item_2(orange).

If .item_1 > .item_2 i need to add scroll bar on .item_1. (third image);

If .item_1 <= .item_2 nothing special(just equal size of blocks)

How can i do it?