<?php


/*
 * QueryParser.php
 * Copyright (c) 2025 https://github.com/Sobuno
 *
 * This file is part of Firefly III (https://github.com/firefly-iii).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see https://www.gnu.org/licenses/.
 */

declare(strict_types=1);

namespace FireflyIII\Support\Search\QueryParser;

use Illuminate\Support\Facades\Log;

/**
 * Single-pass parser that processes query strings into structured nodes.
 * Scans each character once (O(n)) to build field searches, quoted strings,
 * prohibited terms and nested subqueries without backtracking.
 */
class QueryParser implements QueryParserInterface
{
    private string $query;
    private int    $position = 0;

    public function parse(string $query): NodeGroup
    {
        Log::debug(sprintf('Parsing query in QueryParser: "%s"', $query));
        $this->query    = $query;
        $this->position = 0;

        return $this->buildNodeGroup(false);
    }

    private function buildNodeGroup(bool $isSubquery, bool $prohibited = false): NodeGroup
    {
        $nodes      = [];
        $nodeResult = $this->buildNextNode($isSubquery);

        while (null !== $nodeResult->node) {
            $nodes[]    = $nodeResult->node;
            if ($nodeResult->isSubqueryEnd) {
                break;
            }
            $nodeResult = $this->buildNextNode($isSubquery);
        }

        return new NodeGroup($nodes, $prohibited);
    }

    private function buildNextNode(bool $isSubquery): NodeResult
    {
        $tokenUnderConstruction = '';
        $inQuotes               = false;
        $fieldName              = '';
        $prohibited             = false;

        while ($this->position < strlen($this->query)) {
            $char = $this->query[$this->position];
            // Log::debug(sprintf('Char #%d: %s', $this->position, $char));

            // If we're in a quoted string, we treat all characters except another quote as ordinary characters
            if ($inQuotes) {
                if ('"' !== $char) {
                    $tokenUnderConstruction .= $char;
                    ++$this->position;

                    continue;
                }
                // char is "
                ++$this->position;

                return new NodeResult(
                    $this->createNode($tokenUnderConstruction, $fieldName, $prohibited),
                    false
                );
            }

            switch ($char) {
                case '-':
                    if ('' === $tokenUnderConstruction) {
                        // A minus sign at the beginning of a token indicates prohibition
                        // Log::debug('Indicate prohibition');
                        $prohibited = true;
                    }
                    if ('' !== $tokenUnderConstruction) {
                        // In any other location, it's just a normal character
                        $tokenUnderConstruction .= $char;
                    }

                    break;

                case '"':
                    if ('' === $tokenUnderConstruction) {
                        // A quote sign at the beginning of a token indicates the start of a quoted string
                        $inQuotes = true;
                    }
                    if ('' !== $tokenUnderConstruction) {
                        // In any other location, it's just a normal character
                        $tokenUnderConstruction .= $char;
                    }

                    break;

                case '(':
                    if ('' === $tokenUnderConstruction) {
                        // A left parentheses at the beginning of a token indicates the start of a subquery
                        ++$this->position;

                        return new NodeResult(
                            $this->buildNodeGroup(true, $prohibited),
                            false
                        );
                    }
                    // In any other location, it's just a normal character
                    $tokenUnderConstruction .= $char;

                    break;

                case ')':
                    // A right parentheses while in a subquery means the subquery ended,
                    // thus also signaling the end of any node currently being built
                    if ($isSubquery) {
                        ++$this->position;

                        return new NodeResult(
                            '' !== $tokenUnderConstruction
                                ? $this->createNode($tokenUnderConstruction, $fieldName, $prohibited)
                                : null,
                            true
                        );
                    }
                    // In any other location, it's just a normal character
                    $tokenUnderConstruction .= $char;

                    break;


                case ':':
                    $skipNext = false;
                    if ('' === $tokenUnderConstruction) { // @phpstan-ignore-line
                        // In any other location, it's just a normal character
                        $tokenUnderConstruction .= $char;
                        $skipNext = true;
                    }
                    if ('' !== $tokenUnderConstruction && !$skipNext) {
                        Log::debug(sprintf('Turns out that "%s" is a field name. Reset the token.', $tokenUnderConstruction));
                        // If we meet a colon with a left-hand side string, we know we're in a field and are about to set up the value
                        $fieldName              = $tokenUnderConstruction;
                        $tokenUnderConstruction = '';
                    }


                    break;

                case ' ':
                    // A space indicates the end of a token construction if non-empty, otherwise it's just ignored
                    if ('' !== $tokenUnderConstruction) {
                        ++$this->position;

                        return new NodeResult(
                            $this->createNode($tokenUnderConstruction, $fieldName, $prohibited),
                            false
                        );
                    }

                    break;

                default:
                    $tokenUnderConstruction .= $char;
            }

            ++$this->position;
        }

        $finalNode              = '' !== $tokenUnderConstruction || '' !== $fieldName
            ? $this->createNode($tokenUnderConstruction, $fieldName, $prohibited)
            : null;

        return new NodeResult($finalNode, true);
    }

    private function createNode(string $token, string $fieldName, bool $prohibited): Node
    {
        if ('' !== $fieldName) {
            Log::debug(sprintf('Create FieldNode %s:%s (%s)', $fieldName, $token, var_export($prohibited, true)));
            $token = ltrim($token, ':"');
            $token = rtrim($token, '"');

            return new FieldNode(trim($fieldName), trim($token), $prohibited);
        }
        Log::debug(sprintf('Create StringNode "%s" (%s)', $token, var_export($prohibited, true)));

        return new StringNode(trim($token), $prohibited);
    }
}