flat_translations_to_tree.php

<?php
# Creates tree from flat key-value translations
# Can reduce JSON size by 10%, but adds a lot of complexity
# Maybe, it doesn't worth it:(
function make_tree ($input) {
	$keys   = array_keys($input);
	$result = [];
	// Step by step create tree by moving one character deeper
	while (count($keys)) {
		$key = $keys[0];
		// Since we use string operations inside - only string keys allowed
		if (is_string($key) && strlen($key)) {
			$prefix       = $key[0];
			$similar_keys = array_filter(
				$keys,
				function ($inner_key) use ($prefix) {
					return strlen($inner_key) && $inner_key[0] === $prefix;
				}
			);
			// Having less than 1 key doesn't make any sense
			if (count($similar_keys) > 1) {
				// Create tree
				foreach ($similar_keys as $index => $inner_key) {
					$result[$prefix][substr($inner_key, 1) ?: ''] = $input[$inner_key];
					unset($keys[$index], $input[$inner_key]);
				}
				sort($keys);
				// Compress obtained tree
				$result[$prefix] = make_tree($result[$prefix]);
				// Since obtained tree might have ony one key, concat it with current prefix to reduce unnecessary nesting
				$count = count($result[$prefix]);
				if (
					$count == 1 ||
					(
						$count == 2 &&
						is_array(array_values($result[$prefix])[0]) != is_array(array_values($result[$prefix])[1])
					)
				) {
					foreach ($result[$prefix] as $inner_key => $translations) {
						$result[$prefix.$inner_key] = $translations;
					}
					unset($result[$prefix]);
				} elseif (is_array($result[$prefix])) {
					foreach ($result[$prefix] as $inner_key => $nested_structure) {
						if (strlen($inner_key) == 1 && is_array($nested_structure)) {
							foreach ($nested_structure as $nested_key => $translations) {
								$result[$prefix][$inner_key.$nested_key] = $translations;
							}
							unset($result[$prefix][$inner_key]);
						}
					}
				}
				continue;
			}
		}
		$result[$key] = $input[$key];
		array_shift($keys);
		unset($input[$key]);
	}
	return $result;
}