<?php

namespace Kirby\Cache;

use Kirby\Exception\Exception;
use Kirby\Filesystem\Dir;
use Kirby\Filesystem\F;
use Kirby\Toolkit\Str;

/**
 * File System Cache Driver
 *
 * @package   Kirby Cache
 * @author    Bastian Allgeier <bastian@getkirby.com>
 * @link      https://getkirby.com
 * @copyright Bastian Allgeier
 * @license   https://opensource.org/licenses/MIT
 */
class FileCache extends Cache
{
	/**
	 * Full root including prefix
	 */
	protected string $root;

	/**
	 * Sets all parameters which are needed for the file cache
	 *
	 * @param array $options 'root' (required)
	 *                       'prefix' (default: none)
	 *                       'extension' (file extension for cache files, default: none)
	 */
	public function __construct(array $options)
	{
		parent::__construct([
			'root'      => null,
			'prefix'    => null,
			'extension' => null,
			...$options
		]);

		// build the full root including prefix
		$this->root = $this->options['root'];

		if (empty($this->options['prefix']) === false) {
			$this->root .= '/' . $this->options['prefix'];
		}

		// try to create the directory
		Dir::make($this->root, true);
	}

	/**
	 * Returns whether the cache is ready to
	 * store values
	 */
	public function enabled(): bool
	{
		return is_writable($this->root) === true;
	}

	/**
	 * Returns the full root including prefix
	 */
	public function root(): string
	{
		return $this->root;
	}

	/**
	 * Returns the full path to a file for a given key
	 */
	protected function file(string $key): string
	{
		// strip out invalid characters in each path segment
		// split by slash or backslash
		$keyParts = [];
		foreach (preg_split('#([\/\\\\])#', $key, 0, PREG_SPLIT_DELIM_CAPTURE) as $part) {
			switch ($part) {
				case '/':
					// forward slashes don't need special treatment
					break;

				case '\\':
					// backslashes get their own marker in the path
					// to differentiate the cache key from one with forward slashes
					$keyParts[] = '_backslash';
					break;

				case '':
					// empty part means two slashes in a row;
					// special marker like for backslashes
					$keyParts[] = '_empty';
					break;

				default:
					// an actual path segment:
					// check if the segment only contains safe characters;
					// underscores are *not* safe to guarantee uniqueness
					// as they are used in the special cases
					if (preg_match('/^[a-zA-Z0-9-]+$/', $part) === 1) {
						$keyParts[] = $part;
					} else {
						$keyParts[] = Str::slug($part) . '_' . sha1($part);
					}
			}
		}

		$file = $this->root . '/' . implode('/', $keyParts);

		if (isset($this->options['extension'])) {
			return $file . '.' . $this->options['extension'];
		}

		return $file;
	}

	/**
	 * Writes an item to the cache for a given number of minutes and
	 * returns whether the operation was successful
	 *
	 * ```php
	 * // put an item in the cache for 15 minutes
	 * $cache->set('value', 'my value', 15);
	 * ```
	 */
	public function set(string $key, $value, int $minutes = 0): bool
	{
		$file = $this->file($key);

		return F::write($file, (new Value($value, $minutes))->toJson());
	}

	/**
	 * Internal method to retrieve the raw cache value;
	 * needs to return a Value object or null if not found
	 */
	public function retrieve(string $key): Value|null
	{
		$file  = $this->file($key);
		$value = F::read($file);

		return $value ? Value::fromJson($value) : null;
	}

	/**
	 * Checks when the cache has been created;
	 * returns the creation timestamp on success
	 * and false if the item does not exist
	 */
	public function created(string $key): int|false
	{
		// use the modification timestamp
		// as indicator when the cache has been created/overwritten
		clearstatcache();

		// get the file for this cache key
		$file = $this->file($key);
		return file_exists($file) ? filemtime($file) : false;
	}

	/**
	 * Removes an item from the cache and returns
	 * whether the operation was successful
	 */
	public function remove(string $key): bool
	{
		$file = $this->file($key);

		if (is_file($file) === true && F::remove($file) === true) {
			$this->removeEmptyDirectories(dirname($file));
			return true;
		}

		return false;
	}

	/**
	 * Removes empty directories safely by checking each directory
	 * up to the root directory
	 */
	protected function removeEmptyDirectories(string $dir): void
	{
		try {
			// ensure the path doesn't end with a slash for the next comparison
			$dir = rtrim($dir, '/\/');

			// checks all directory segments until reaching the root directory
			while (Str::startsWith($dir, $this->root()) === true && $dir !== $this->root()) {
				$files = scandir($dir);

				if ($files === false) {
					$files = []; // @codeCoverageIgnore
				}

				$files = array_diff($files, ['.', '..']);

				if ($files === [] && Dir::remove($dir) === true) {
					// continue with the next level up
					$dir = dirname($dir);
				} else {
					// no need to continue with the next level up as `$dir` was not deleted
					break;
				}
			}
		} catch (Exception) { // @codeCoverageIgnore
			// silently stops the process
		}
	}

	/**
	 * Flushes the entire cache and returns
	 * whether the operation was successful
	 */
	public function flush(): bool
	{
		if (
			Dir::remove($this->root) === true &&
			Dir::make($this->root) === true
		) {
			return true;
		}

		return false; // @codeCoverageIgnore
	}
}
