<?php
/**
 * Parses an Index hint.
 */
declare(strict_types=1);

namespace PhpMyAdmin\SqlParser\Components;

use PhpMyAdmin\SqlParser\Component;
use PhpMyAdmin\SqlParser\Parser;
use PhpMyAdmin\SqlParser\Token;
use PhpMyAdmin\SqlParser\TokensList;
use function implode;
use function is_array;

/**
 * Parses an Index hint.
 */
class IndexHint extends Component
{
    /**
     * The type of hint (USE/FORCE/IGNORE)
     *
     * @var string
     */
    public $type;

    /**
     * What the hint is for (INDEX/KEY)
     *
     * @var string
     */
    public $indexOrKey;

    /**
     * The clause for which this hint is (JOIN/ORDER BY/GROUP BY)
     *
     * @var string
     */
    public $for;

    /**
     * List of indexes in this hint
     *
     * @var array
     */
    public $indexes = [];

    /**
     * @param string $type       the type of hint (USE/FORCE/IGNORE)
     * @param string $indexOrKey What the hint is for (INDEX/KEY)
     * @param string $for        the clause for which this hint is (JOIN/ORDER BY/GROUP BY)
     * @param array  $indexes    List of indexes in this hint
     */
    public function __construct(string $type = null, string $indexOrKey = null, string $for = null, array $indexes = [])
    {
        $this->type = $type;
        $this->indexOrKey = $indexOrKey;
        $this->for = $for;
        $this->indexes = $indexes;
    }

    /**
     * @param Parser     $parser  the parser that serves as context
     * @param TokensList $list    the list of tokens that are being parsed
     * @param array      $options parameters for parsing
     *
     * @return IndexHint|Component[]
     */
    public static function parse(Parser $parser, TokensList $list, array $options = [])
    {
        $ret = [];
        $expr = new static();
        $expr->type = $options['type'] ?? null;
        /**
         * The state of the parser.
         *
         * Below are the states of the parser.
         *      0 ----------------- [ USE/IGNORE/FORCE ]-----------------> 1
         *      1 -------------------- [ INDEX/KEY ] --------------------> 2
         *      2 ----------------------- [ FOR ] -----------------------> 3
         *      2 -------------------- [ expr_list ] --------------------> 0
         *      3 -------------- [ JOIN/GROUP BY/ORDER BY ] -------------> 4
         *      4 -------------------- [ expr_list ] --------------------> 0
         *
         * @var int
         */
        $state = 0;

        // By design, the parser will parse first token after the keyword. So, the keyword
        // must be analyzed too, in order to determine the type of this index hint.
        if ($list->idx > 0) {
            --$list->idx;
        }

        for (; $list->idx < $list->count; ++$list->idx) {
            /**
             * Token parsed at this moment.
             *
             * @var Token
             */
            $token = $list->tokens[$list->idx];

            // End of statement.
            if ($token->type === Token::TYPE_DELIMITER) {
                break;
            }

            // Skipping whitespaces and comments.
            if (($token->type === Token::TYPE_WHITESPACE) || ($token->type === Token::TYPE_COMMENT)) {
                continue;
            }

            switch ($state) {
                case 0:
                    if ($token->type === Token::TYPE_KEYWORD) {
                        if ($token->keyword === 'USE' || $token->keyword === 'IGNORE' || $token->keyword === 'FORCE') {
                            $expr->type = $token->keyword;
                            $state = 1;
                        } else {
                            break 2;
                        }
                    }

                    break;
                case 1:
                    if ($token->type === Token::TYPE_KEYWORD) {
                        if ($token->keyword === 'INDEX' || $token->keyword === 'KEY') {
                            $expr->indexOrKey = $token->keyword;
                        } else {
                            $parser->error('Unexpected keyword.', $token);
                        }

                        $state = 2;
                    } else {
                        // we expect the token to be a keyword
                        $parser->error('Unexpected token.', $token);
                    }

                    break;
                case 2:
                    if ($token->type === Token::TYPE_KEYWORD && $token->keyword === 'FOR') {
                        $state = 3;
                    } else {
                        $expr->indexes = ExpressionArray::parse($parser, $list);
                        $state = 0;
                        $ret[] = $expr;
                        $expr = new static();
                    }

                    break;
                case 3:
                    if ($token->type === Token::TYPE_KEYWORD) {
                        if ($token->keyword === 'JOIN'
                            || $token->keyword === 'GROUP BY'
                            || $token->keyword === 'ORDER BY'
                        ) {
                            $expr->for = $token->keyword;
                        } else {
                            $parser->error('Unexpected keyword.', $token);
                        }

                        $state = 4;
                    } else {
                        // we expect the token to be a keyword
                        $parser->error('Unexpected token.', $token);
                    }

                    break;
                case 4:
                    $expr->indexes = ExpressionArray::parse($parser, $list);
                    $state = 0;
                    $ret[] = $expr;
                    $expr = new static();
                    break;
            }
        }

        --$list->idx;

        return $ret;
    }

    /**
     * @param IndexHint|IndexHint[] $component the component to be built
     * @param array                 $options   parameters for building
     *
     * @return string
     */
    public static function build($component, array $options = [])
    {
        if (is_array($component)) {
            return implode(' ', $component);
        }

        $ret = $component->type . ' ' . $component->indexOrKey . ' ';
        if ($component->for !== null) {
            $ret .= 'FOR ' . $component->for . ' ';
        }

        return $ret . ExpressionArray::build($component->indexes);
    }
}