<?php
/* vim: set expandtab sw=4 ts=4 sts=4: */
/**
 * Displays a list of server status variables
 *
 * @package PhpMyAdmin\Controllers
 */
declare(strict_types=1);

namespace PhpMyAdmin\Controllers\Server\Status;

use PhpMyAdmin\Util;

/**
 * Class VariablesController
 * @package PhpMyAdmin\Controllers\Server\Status
 */
class VariablesController extends AbstractController
{
    /**
     * @param array $params Request parameters
     * @return string HTML
     */
    public function index(array $params): string
    {
        if (isset($params['flush'])) {
            $this->flush($params['flush']);
        }

        if ($this->data->dataLoaded) {
            $categories = [];
            foreach ($this->data->sections as $sectionId => $sectionName) {
                if (isset($this->data->sectionUsed[$sectionId])) {
                    $categories[$sectionId] = [
                        'id' => $sectionId,
                        'name' => $sectionName,
                        'is_selected' => false,
                    ];
                    if (! empty($params['filterCategory'])
                        && $params['filterCategory'] === $sectionId
                    ) {
                        $categories[$sectionId]['is_selected'] = true;
                    }
                }
            }

            $links = [];
            foreach ($this->data->links as $sectionName => $sectionLinks) {
                $links[$sectionName] = [
                    'name' => 'status_' . $sectionName,
                    'links' => $sectionLinks,
                ];
            }

            $descriptions = $this->getDescriptions();
            $alerts = $this->getAlerts();

            $variables = [];
            foreach ($this->data->status as $name => $value) {
                $variables[$name] = [
                    'name' => $name,
                    'value' => $value,
                    'is_numeric' => is_numeric($value),
                    'class' => $this->data->allocationMap[$name] ?? null,
                    'doc' => '',
                    'has_alert' => false,
                    'is_alert' => false,
                    'description' => $descriptions[$name] ?? '',
                    'description_doc' => [],
                ];

                // Fields containing % are calculated,
                // they can not be described in MySQL documentation
                if (mb_strpos($name, '%') === false) {
                    $variables[$name]['doc'] = Util::linkToVarDocumentation(
                        $name,
                        $this->dbi->isMariaDB()
                    );
                }

                if (isset($alerts[$name])) {
                    $variables[$name]['has_alert'] = true;
                    if ($value > $alerts[$name]) {
                        $variables[$name]['is_alert'] = true;
                    }
                }

                if (isset($this->data->links[$name])) {
                    foreach ($this->data->links[$name] as $linkName => $linkUrl) {
                        $variables[$name]['description_doc'][] = [
                            'name' => $linkName,
                            'url' => $linkUrl,
                        ];
                    }
                }
            }
        }

        return $this->template->render('server/status/variables/index', [
            'is_data_loaded' => $this->data->dataLoaded,
            'filter_text' => ! empty($params['filterText']) ? $params['filterText'] : '',
            'is_only_alerts' => ! empty($params['filterAlert']),
            'is_not_formatted' => ! empty($params['dontFormat']),
            'categories' => $categories ?? [],
            'links' => $links ?? [],
            'variables' => $variables ?? [],
        ]);
    }

    /**
     * Flush status variables if requested
     *
     * @param string $flush Variable name
     * @return void
     */
    private function flush(string $flush): void
    {
        $flushCommands = [
            'STATUS',
            'TABLES',
            'QUERY CACHE',
        ];

        if (in_array($flush, $flushCommands)) {
            $this->dbi->query('FLUSH ' . $flush . ';');
        }
    }

    /**
     * @return array
     */
    private function getAlerts(): array
    {
        // name => max value before alert
        return [
            // lower is better
            // variable => max value
            'Aborted_clients' => 0,
            'Aborted_connects' => 0,

            'Binlog_cache_disk_use' => 0,

            'Created_tmp_disk_tables' => 0,

            'Handler_read_rnd' => 0,
            'Handler_read_rnd_next' => 0,

            'Innodb_buffer_pool_pages_dirty' => 0,
            'Innodb_buffer_pool_reads' => 0,
            'Innodb_buffer_pool_wait_free' => 0,
            'Innodb_log_waits' => 0,
            'Innodb_row_lock_time_avg' => 10, // ms
            'Innodb_row_lock_time_max' => 50, // ms
            'Innodb_row_lock_waits' => 0,

            'Slow_queries' => 0,
            'Delayed_errors' => 0,
            'Select_full_join' => 0,
            'Select_range_check' => 0,
            'Sort_merge_passes' => 0,
            'Opened_tables' => 0,
            'Table_locks_waited' => 0,
            'Qcache_lowmem_prunes' => 0,

            'Qcache_free_blocks' =>
                isset($this->data->status['Qcache_total_blocks'])
                    ? $this->data->status['Qcache_total_blocks'] / 5
                    : 0,
            'Slow_launch_threads' => 0,

            // depends on Key_read_requests
            // normally lower then 1:0.01
            'Key_reads' => isset($this->data->status['Key_read_requests'])
                ? (0.01 * $this->data->status['Key_read_requests']) : 0,
            // depends on Key_write_requests
            // normally nearly 1:1
            'Key_writes' => isset($this->data->status['Key_write_requests'])
                ? (0.9 * $this->data->status['Key_write_requests']) : 0,

            'Key_buffer_fraction' => 0.5,

            // alert if more than 95% of thread cache is in use
            'Threads_cached' => isset($this->data->variables['thread_cache_size'])
                ? 0.95 * $this->data->variables['thread_cache_size'] : 0,

            // higher is better
            // variable => min value
            //'Handler read key' => '> ',
        ];
    }

    /**
     * Returns a list of variable descriptions
     *
     * @return array
     */
    private function getDescriptions(): array
    {
        /**
         * Messages are built using the message name
         */
        return [
            'Aborted_clients' => __(
                'The number of connections that were aborted because the client died'
                . ' without closing the connection properly.'
            ),
            'Aborted_connects' => __(
                'The number of failed attempts to connect to the MySQL server.'
            ),
            'Binlog_cache_disk_use' => __(
                'The number of transactions that used the temporary binary log cache'
                . ' but that exceeded the value of binlog_cache_size and used a'
                . ' temporary file to store statements from the transaction.'
            ),
            'Binlog_cache_use' => __(
                'The number of transactions that used the temporary binary log cache.'
            ),
            'Connections' => __(
                'The number of connection attempts (successful or not)'
                . ' to the MySQL server.'
            ),
            'Created_tmp_disk_tables' => __(
                'The number of temporary tables on disk created automatically by'
                . ' the server while executing statements. If'
                . ' Created_tmp_disk_tables is big, you may want to increase the'
                . ' tmp_table_size  value to cause temporary tables to be'
                . ' memory-based instead of disk-based.'
            ),
            'Created_tmp_files' => __(
                'How many temporary files mysqld has created.'
            ),
            'Created_tmp_tables' => __(
                'The number of in-memory temporary tables created automatically'
                . ' by the server while executing statements.'
            ),
            'Delayed_errors' => __(
                'The number of rows written with INSERT DELAYED for which some'
                . ' error occurred (probably duplicate key).'
            ),
            'Delayed_insert_threads' => __(
                'The number of INSERT DELAYED handler threads in use. Every'
                . ' different table on which one uses INSERT DELAYED gets'
                . ' its own thread.'
            ),
            'Delayed_writes' => __(
                'The number of INSERT DELAYED rows written.'
            ),
            'Flush_commands'  => __(
                'The number of executed FLUSH statements.'
            ),
            'Handler_commit' => __(
                'The number of internal COMMIT statements.'
            ),
            'Handler_delete' => __(
                'The number of times a row was deleted from a table.'
            ),
            'Handler_discover' => __(
                'The MySQL server can ask the NDB Cluster storage engine if it'
                . ' knows about a table with a given name. This is called discovery.'
                . ' Handler_discover indicates the number of time tables have been'
                . ' discovered.'
            ),
            'Handler_read_first' => __(
                'The number of times the first entry was read from an index. If this'
                . ' is high, it suggests that the server is doing a lot of full'
                . ' index scans; for example, SELECT col1 FROM foo, assuming that'
                . ' col1 is indexed.'
            ),
            'Handler_read_key' => __(
                'The number of requests to read a row based on a key. If this is'
                . ' high, it is a good indication that your queries and tables'
                . ' are properly indexed.'
            ),
            'Handler_read_next' => __(
                'The number of requests to read the next row in key order. This is'
                . ' incremented if you are querying an index column with a range'
                . ' constraint or if you are doing an index scan.'
            ),
            'Handler_read_prev' => __(
                'The number of requests to read the previous row in key order.'
                . ' This read method is mainly used to optimize ORDER BY … DESC.'
            ),
            'Handler_read_rnd' => __(
                'The number of requests to read a row based on a fixed position.'
                . ' This is high if you are doing a lot of queries that require'
                . ' sorting of the result. You probably have a lot of queries that'
                . ' require MySQL to scan whole tables or you have joins that'
                . ' don\'t use keys properly.'
            ),
            'Handler_read_rnd_next' => __(
                'The number of requests to read the next row in the data file.'
                . ' This is high if you are doing a lot of table scans. Generally'
                . ' this suggests that your tables are not properly indexed or that'
                . ' your queries are not written to take advantage of the indexes'
                . ' you have.'
            ),
            'Handler_rollback' => __(
                'The number of internal ROLLBACK statements.'
            ),
            'Handler_update' => __(
                'The number of requests to update a row in a table.'
            ),
            'Handler_write' => __(
                'The number of requests to insert a row in a table.'
            ),
            'Innodb_buffer_pool_pages_data' => __(
                'The number of pages containing data (dirty or clean).'
            ),
            'Innodb_buffer_pool_pages_dirty' => __(
                'The number of pages currently dirty.'
            ),
            'Innodb_buffer_pool_pages_flushed' => __(
                'The number of buffer pool pages that have been requested'
                . ' to be flushed.'
            ),
            'Innodb_buffer_pool_pages_free' => __(
                'The number of free pages.'
            ),
            'Innodb_buffer_pool_pages_latched' => __(
                'The number of latched pages in InnoDB buffer pool. These are pages'
                . ' currently being read or written or that can\'t be flushed or'
                . ' removed for some other reason.'
            ),
            'Innodb_buffer_pool_pages_misc' => __(
                'The number of pages busy because they have been allocated for'
                . ' administrative overhead such as row locks or the adaptive'
                . ' hash index. This value can also be calculated as'
                . ' Innodb_buffer_pool_pages_total - Innodb_buffer_pool_pages_free'
                . ' - Innodb_buffer_pool_pages_data.'
            ),
            'Innodb_buffer_pool_pages_total' => __(
                'Total size of buffer pool, in pages.'
            ),
            'Innodb_buffer_pool_read_ahead_rnd' => __(
                'The number of "random" read-aheads InnoDB initiated. This happens'
                . ' when a query is to scan a large portion of a table but in'
                . ' random order.'
            ),
            'Innodb_buffer_pool_read_ahead_seq' => __(
                'The number of sequential read-aheads InnoDB initiated. This'
                . ' happens when InnoDB does a sequential full table scan.'
            ),
            'Innodb_buffer_pool_read_requests' => __(
                'The number of logical read requests InnoDB has done.'
            ),
            'Innodb_buffer_pool_reads' => __(
                'The number of logical reads that InnoDB could not satisfy'
                . ' from buffer pool and had to do a single-page read.'
            ),
            'Innodb_buffer_pool_wait_free' => __(
                'Normally, writes to the InnoDB buffer pool happen in the'
                . ' background. However, if it\'s necessary to read or create a page'
                . ' and no clean pages are available, it\'s necessary to wait for'
                . ' pages to be flushed first. This counter counts instances of'
                . ' these waits. If the buffer pool size was set properly, this'
                . ' value should be small.'
            ),
            'Innodb_buffer_pool_write_requests' => __(
                'The number writes done to the InnoDB buffer pool.'
            ),
            'Innodb_data_fsyncs' => __(
                'The number of fsync() operations so far.'
            ),
            'Innodb_data_pending_fsyncs' => __(
                'The current number of pending fsync() operations.'
            ),
            'Innodb_data_pending_reads' => __(
                'The current number of pending reads.'
            ),
            'Innodb_data_pending_writes' => __(
                'The current number of pending writes.'
            ),
            'Innodb_data_read' => __(
                'The amount of data read so far, in bytes.'
            ),
            'Innodb_data_reads' => __(
                'The total number of data reads.'
            ),
            'Innodb_data_writes' => __(
                'The total number of data writes.'
            ),
            'Innodb_data_written' => __(
                'The amount of data written so far, in bytes.'
            ),
            'Innodb_dblwr_pages_written' => __(
                'The number of pages that have been written for'
                . ' doublewrite operations.'
            ),
            'Innodb_dblwr_writes' => __(
                'The number of doublewrite operations that have been performed.'
            ),
            'Innodb_log_waits' => __(
                'The number of waits we had because log buffer was too small and'
                . ' we had to wait for it to be flushed before continuing.'
            ),
            'Innodb_log_write_requests' => __(
                'The number of log write requests.'
            ),
            'Innodb_log_writes' => __(
                'The number of physical writes to the log file.'
            ),
            'Innodb_os_log_fsyncs' => __(
                'The number of fsync() writes done to the log file.'
            ),
            'Innodb_os_log_pending_fsyncs' => __(
                'The number of pending log file fsyncs.'
            ),
            'Innodb_os_log_pending_writes' => __(
                'Pending log file writes.'
            ),
            'Innodb_os_log_written' => __(
                'The number of bytes written to the log file.'
            ),
            'Innodb_pages_created' => __(
                'The number of pages created.'
            ),
            'Innodb_page_size' => __(
                'The compiled-in InnoDB page size (default 16KB). Many values are'
                . ' counted in pages; the page size allows them to be easily'
                . ' converted to bytes.'
            ),
            'Innodb_pages_read' => __(
                'The number of pages read.'
            ),
            'Innodb_pages_written' => __(
                'The number of pages written.'
            ),
            'Innodb_row_lock_current_waits' => __(
                'The number of row locks currently being waited for.'
            ),
            'Innodb_row_lock_time_avg' => __(
                'The average time to acquire a row lock, in milliseconds.'
            ),
            'Innodb_row_lock_time' => __(
                'The total time spent in acquiring row locks, in milliseconds.'
            ),
            'Innodb_row_lock_time_max' => __(
                'The maximum time to acquire a row lock, in milliseconds.'
            ),
            'Innodb_row_lock_waits' => __(
                'The number of times a row lock had to be waited for.'
            ),
            'Innodb_rows_deleted' => __(
                'The number of rows deleted from InnoDB tables.'
            ),
            'Innodb_rows_inserted' => __(
                'The number of rows inserted in InnoDB tables.'
            ),
            'Innodb_rows_read' => __(
                'The number of rows read from InnoDB tables.'
            ),
            'Innodb_rows_updated' => __(
                'The number of rows updated in InnoDB tables.'
            ),
            'Key_blocks_not_flushed' => __(
                'The number of key blocks in the key cache that have changed but'
                . ' haven\'t yet been flushed to disk. It used to be known as'
                . ' Not_flushed_key_blocks.'
            ),
            'Key_blocks_unused' => __(
                'The number of unused blocks in the key cache. You can use this'
                . ' value to determine how much of the key cache is in use.'
            ),
            'Key_blocks_used' => __(
                'The number of used blocks in the key cache. This value is a'
                . ' high-water mark that indicates the maximum number of blocks'
                . ' that have ever been in use at one time.'
            ),
            'Key_buffer_fraction_%' => __(
                'Percentage of used key cache (calculated value)'
            ),
            'Key_read_requests' => __(
                'The number of requests to read a key block from the cache.'
            ),
            'Key_reads' => __(
                'The number of physical reads of a key block from disk. If Key_reads'
                . ' is big, then your key_buffer_size value is probably too small.'
                . ' The cache miss rate can be calculated as'
                . ' Key_reads/Key_read_requests.'
            ),
            'Key_read_ratio_%' => __(
                'Key cache miss calculated as rate of physical reads compared'
                . ' to read requests (calculated value)'
            ),
            'Key_write_requests' => __(
                'The number of requests to write a key block to the cache.'
            ),
            'Key_writes' => __(
                'The number of physical writes of a key block to disk.'
            ),
            'Key_write_ratio_%' => __(
                'Percentage of physical writes compared'
                . ' to write requests (calculated value)'
            ),
            'Last_query_cost' => __(
                'The total cost of the last compiled query as computed by the query'
                . ' optimizer. Useful for comparing the cost of different query'
                . ' plans for the same query. The default value of 0 means that'
                . ' no query has been compiled yet.'
            ),
            'Max_used_connections' => __(
                'The maximum number of connections that have been in use'
                . ' simultaneously since the server started.'
            ),
            'Not_flushed_delayed_rows' => __(
                'The number of rows waiting to be written in INSERT DELAYED queues.'
            ),
            'Opened_tables' => __(
                'The number of tables that have been opened. If opened tables is'
                . ' big, your table cache value is probably too small.'
            ),
            'Open_files' => __(
                'The number of files that are open.'
            ),
            'Open_streams' => __(
                'The number of streams that are open (used mainly for logging).'
            ),
            'Open_tables' => __(
                'The number of tables that are open.'
            ),
            'Qcache_free_blocks' => __(
                'The number of free memory blocks in query cache. High numbers can'
                . ' indicate fragmentation issues, which may be solved by issuing'
                . ' a FLUSH QUERY CACHE statement.'
            ),
            'Qcache_free_memory' => __(
                'The amount of free memory for query cache.'
            ),
            'Qcache_hits' => __(
                'The number of cache hits.'
            ),
            'Qcache_inserts' => __(
                'The number of queries added to the cache.'
            ),
            'Qcache_lowmem_prunes' => __(
                'The number of queries that have been removed from the cache to'
                . ' free up memory for caching new queries. This information can'
                . ' help you tune the query cache size. The query cache uses a'
                . ' least recently used (LRU) strategy to decide which queries'
                . ' to remove from the cache.'
            ),
            'Qcache_not_cached' => __(
                'The number of non-cached queries (not cachable, or not cached'
                . ' due to the query_cache_type setting).'
            ),
            'Qcache_queries_in_cache' => __(
                'The number of queries registered in the cache.'
            ),
            'Qcache_total_blocks' => __(
                'The total number of blocks in the query cache.'
            ),
            'Rpl_status' => __(
                'The status of failsafe replication (not yet implemented).'
            ),
            'Select_full_join' => __(
                'The number of joins that do not use indexes. If this value is'
                . ' not 0, you should carefully check the indexes of your tables.'
            ),
            'Select_full_range_join' => __(
                'The number of joins that used a range search on a reference table.'
            ),
            'Select_range_check' => __(
                'The number of joins without keys that check for key usage after'
                . ' each row. (If this is not 0, you should carefully check the'
                . ' indexes of your tables.)'
            ),
            'Select_range' => __(
                'The number of joins that used ranges on the first table. (It\'s'
                . ' normally not critical even if this is big.)'
            ),
            'Select_scan' => __(
                'The number of joins that did a full scan of the first table.'
            ),
            'Slave_open_temp_tables' => __(
                'The number of temporary tables currently'
                . ' open by the slave SQL thread.'
            ),
            'Slave_retried_transactions' => __(
                'Total (since startup) number of times the replication slave SQL'
                . ' thread has retried transactions.'
            ),
            'Slave_running' => __(
                'This is ON if this server is a slave that is connected to a master.'
            ),
            'Slow_launch_threads' => __(
                'The number of threads that have taken more than slow_launch_time'
                . ' seconds to create.'
            ),
            'Slow_queries' => __(
                'The number of queries that have taken more than long_query_time'
                . ' seconds.'
            ),
            'Sort_merge_passes' => __(
                'The number of merge passes the sort algorithm has had to do.'
                . ' If this value is large, you should consider increasing the'
                . ' value of the sort_buffer_size system variable.'
            ),
            'Sort_range' => __(
                'The number of sorts that were done with ranges.'
            ),
            'Sort_rows' => __(
                'The number of sorted rows.'
            ),
            'Sort_scan' => __(
                'The number of sorts that were done by scanning the table.'
            ),
            'Table_locks_immediate' => __(
                'The number of times that a table lock was acquired immediately.'
            ),
            'Table_locks_waited' => __(
                'The number of times that a table lock could not be acquired'
                . ' immediately and a wait was needed. If this is high, and you have'
                . ' performance problems, you should first optimize your queries,'
                . ' and then either split your table or tables or use replication.'
            ),
            'Threads_cached' => __(
                'The number of threads in the thread cache. The cache hit rate can'
                . ' be calculated as Threads_created/Connections. If this value is'
                . ' red you should raise your thread_cache_size.'
            ),
            'Threads_connected' => __(
                'The number of currently open connections.'
            ),
            'Threads_created' => __(
                'The number of threads created to handle connections. If'
                . ' Threads_created is big, you may want to increase the'
                . ' thread_cache_size value. (Normally this doesn\'t give a notable'
                . ' performance improvement if you have a good thread'
                . ' implementation.)'
            ),
            'Threads_cache_hitrate_%' => __(
                'Thread cache hit rate (calculated value)'
            ),
            'Threads_running' => __(
                'The number of threads that are not sleeping.'
            ),
        ];
    }
}