<?php

declare(strict_types=1);

/**
 * SPDX-FileCopyrightText: Sebastian Krupinski <krupinski01@gmail.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

namespace KTXM\ProviderImap\Service\Cache;

use DateTimeImmutable;
use DateTimeZone;
use KTXF\Resource\Filter\FilterComparisonOperator;
use KTXF\Resource\Filter\FilterConjunctionOperator;
use KTXF\Resource\Filter\IFilter;
use KTXF\Resource\Sort\ISort;
use MongoDB\BSON\Regex;

/**
 * Translates entity list filters and sorts into meta store queries.
 *
 * Mirrors LiveMailService's IMAP SEARCH / SORT translation so a cached list matches a
 * live one: conditions are combined left to right with their conjunction, strings
 * match as case-insensitive substrings, dates compare whole (UTC) days on `received`,
 * sizes compare `size`. Conditions the cache cannot answer (body text, full text)
 * make the whole filter a server filter.
 */
class MessageQueryBuilder
{
    /** Attributes that need the message body, which the meta store does not hold */
    private const SERVER_ATTRIBUTES = ['body', '*', 'all'];

    /** Address fields: matched on address and display label */
    private const ADDRESS_ATTRIBUTES = ['from', 'to', 'cc', 'bcc'];

    /** Sorts on text fields use a case-insensitive collation */
    private const TEXT_SORTS = ['subject', 'from', 'to'];

    /**
     * Whether the filter has to be evaluated by the server (IMAP SEARCH).
     */
    public function needsServer(?IFilter $filter): bool
    {
        foreach ($filter?->conditions() ?? [] as $condition) {
            if (in_array($condition['attribute'] ?? '', self::SERVER_ATTRIBUTES, true)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Meta store filter for a list filter; [] matches everything.
     *
     * Only valid when needsServer() is false.
     */
    public function filter(?IFilter $filter): array
    {
        $expression = null;

        foreach ($filter?->conditions() ?? [] as $condition) {
            $operand = $this->operand($condition);
            if ($operand === null) {
                continue;
            }

            if ($expression === null) {
                $expression = $operand;
                continue;
            }

            $expression = (($condition['conjunction'] ?? FilterConjunctionOperator::AND) === FilterConjunctionOperator::OR)
                ? ['$or' => [$expression, $operand]]
                : ['$and' => [$expression, $operand]];
        }

        return $expression ?? [];
    }

    /**
     * Meta store sort for a list sort; always ends with uid so pages are stable.
     *
     * @return array{sort: array<string, int>, collation: ?array} collation is set when a text field is sorted
     */
    public function sort(?ISort $sort): array
    {
        $order = [];
        $text = false;

        foreach ($sort?->conditions() ?? [] as $condition) {
            $attribute = $condition['attribute'] ?? '';
            $field = match ($attribute) {
                'from' => 'from.address',
                'to' => 'to.0.address',
                'subject' => 'subject',
                'received' => 'received',
                'sent' => 'sent',
                'size' => 'size',
                default => null,
            };
            if ($field === null) {
                continue;
            }

            $order[$field] = ($condition['direction'] ?? true) ? 1 : -1;
            $text = $text || in_array($attribute, self::TEXT_SORTS, true);
        }

        $order['uid'] ??= 1;

        return ['sort' => $order, 'collation' => $text ? ['locale' => 'en', 'strength' => 2] : null];
    }

    /**
     * @param array{attribute:string, value:mixed, comparator?:FilterComparisonOperator, conjunction?:FilterConjunctionOperator|null} $condition
     */
    private function operand(array $condition): ?array
    {
        $attribute = $condition['attribute'] ?? '';
        $value = $condition['value'] ?? null;
        $comparator = $condition['comparator'] ?? FilterComparisonOperator::EQ;

        return match (true) {
            $attribute === 'subject', in_array($attribute, self::ADDRESS_ATTRIBUTES, true) => $this->stringOperand($attribute, $value, $comparator),
            $attribute === 'before', $attribute === 'after' => $this->dateOperand($attribute, $value, $comparator),
            $attribute === 'min', $attribute === 'max' => $this->sizeOperand($attribute, $value, $comparator),
            default => null,
        };
    }

    private function stringOperand(string $attribute, mixed $value, FilterComparisonOperator $comparator): ?array
    {
        $values = is_array($value) ? array_values($value) : [$value];
        $values = array_values(array_filter(array_map(
            static fn (mixed $item): string => trim((string) $item),
            $values,
        ), static fn (string $item): bool => $item !== ''));

        if ($values === []) {
            return null;
        }

        $matches = array_map(fn (string $item): array => $this->stringMatch($attribute, $item), $values);

        return match ($comparator) {
            FilterComparisonOperator::EQ, FilterComparisonOperator::LIKE, FilterComparisonOperator::IN
                => count($matches) === 1 ? $matches[0] : ['$or' => $matches],
            FilterComparisonOperator::NEQ, FilterComparisonOperator::NLIKE, FilterComparisonOperator::NIN
                => ['$nor' => $matches],
            default => null,
        };
    }

    private function stringMatch(string $attribute, string $value): array
    {
        $regex = new Regex(preg_quote($value, '/'), 'i');

        if ($attribute === 'subject') {
            return ['subject' => $regex];
        }

        return ['$or' => [[$attribute . '.address' => $regex], [$attribute . '.label' => $regex]]];
    }

    private function dateOperand(string $attribute, mixed $value, FilterComparisonOperator $comparator): ?array
    {
        $day = $this->day($value);
        if ($day === null) {
            return null;
        }

        $start = $day->format('Y-m-d\TH:i:s\Z');
        $end = $day->modify('+1 day')->format('Y-m-d\TH:i:s\Z');
        $on = ['received' => ['$gte' => $start, '$lt' => $end]];

        return match ($comparator) {
            FilterComparisonOperator::EQ => $on,
            FilterComparisonOperator::NEQ => ['$nor' => [$on]],
            FilterComparisonOperator::LT, FilterComparisonOperator::LTE => $attribute === 'before' ? ['received' => ['$lt' => $start]] : null,
            FilterComparisonOperator::GT, FilterComparisonOperator::GTE => $attribute === 'after' ? ['received' => ['$gte' => $start]] : null,
            default => null,
        };
    }

    private function sizeOperand(string $attribute, mixed $value, FilterComparisonOperator $comparator): ?array
    {
        if (!is_int($value) && !is_numeric($value)) {
            return null;
        }

        $size = max(0, (int) $value);

        return match ($attribute) {
            'min' => match ($comparator) {
                FilterComparisonOperator::EQ, FilterComparisonOperator::GTE => ['size' => ['$gte' => $size]],
                FilterComparisonOperator::GT => ['size' => ['$gt' => $size]],
                FilterComparisonOperator::LT => ['size' => ['$lt' => $size]],
                FilterComparisonOperator::LTE => ['size' => ['$lte' => $size]],
                FilterComparisonOperator::NEQ => ['size' => ['$ne' => $size]],
                default => null,
            },
            'max' => match ($comparator) {
                FilterComparisonOperator::EQ, FilterComparisonOperator::LTE => ['size' => ['$lte' => $size]],
                FilterComparisonOperator::LT => ['size' => ['$lt' => $size]],
                FilterComparisonOperator::GT => ['size' => ['$gt' => $size]],
                FilterComparisonOperator::GTE => ['size' => ['$gte' => $size]],
                FilterComparisonOperator::NEQ => ['size' => ['$ne' => $size]],
                default => null,
            },
            default => null,
        };
    }

    /**
     * Start of the (UTC) day a filter value falls on.
     */
    private function day(mixed $value): ?DateTimeImmutable
    {
        if ($value === null || $value === '') {
            return null;
        }

        try {
            $date = $value instanceof DateTimeImmutable ? $value : new DateTimeImmutable(trim((string) $value));
        } catch (\Exception) {
            return null;
        }

        return new DateTimeImmutable($date->format('Y-m-d'), new DateTimeZone('UTC'));
    }
}