api.php

<?php

/**
 * Implements Battlesnake API response functions.
 *
 * @see https://docs.battlesnake.com/snake-api
 */

/**
 * @param string $color    Must be a hexadecimal color string, preceded with a hash symbol, e.g. "#ff00ff"
 * @param string $headType Head type string, see API docs for accepted values
 * @param string $tailType Tail type string, see API docs for accepted values
 */
function startResponse(string $color, string $headType = 'beluga', string $tailType = 'block-bum') : void
{
    outputJsonResponse(['color' => $color, 'headType' => $headType, 'tailType' => $tailType]);
}

/**
 * Outputs a move response to the Battlesnake game engine.
 *
 * @param string $move Must be one of 'up', 'down', 'left', 'right', as per Battlesnake API
 *
 * @throws Exception
 */
function moveResponse(string $move) : void
{
    if (! in_array($move, ['up', 'down', 'left', 'right']))
    {
        throw new \Exception('Move must be one of [up, down, left, right]');
    }

    outputJsonResponse(['move' => $move]);
}

/**
 * Responses to requests to the /end endpoint are ignored by the Battlesnake engine, so this function outputs nothing.
 */
function endResponse() : void
{
    echo '';
}

/**
 * Echoes a traditional 'pong' response to requests to the /ping endpoint.
 */
function pingResponse() : void
{
    echo 'pong';
}

/**
 * Utility function to output an array of response data as JSON.
 *
 * @param array $responseData Array of data to be cast to an object and encoded to JSON
 */
function outputJsonResponse(array $responseData) : void
{
    $body = (object) $responseData;
    header('Content-Type: application/json');
    echo json_encode($body);
}