<?php

declare(strict_types=1);

namespace Pdp;

use SplFileObject;
use SplTempFileObject;
use Stringable;

use function array_key_exists;
use function array_pop;
use function explode;
use function in_array;
use function preg_match;
use function substr;

final class Rules implements PublicSuffixList
{
    private const ICANN_DOMAINS = 'ICANN_DOMAINS';
    private const PRIVATE_DOMAINS = 'PRIVATE_DOMAINS';
    private const UNKNOWN_DOMAINS = 'UNKNOWN_DOMAINS';
    private const DOMAIN_RULE_MARKER = '?';
    private const REGEX_PSL_SECTION = ',^// ===(?<point>BEGIN|END) (?<type>ICANN|PRIVATE) DOMAINS===,';
    private const PSL_SECTION = [
        'ICANN' => [
            'BEGIN' => self::ICANN_DOMAINS,
            'END' => '',
        ],
        'PRIVATE' => [
            'BEGIN' => self::PRIVATE_DOMAINS,
            'END' => '',
        ],
    ];

    /**
     * @param array{ICANN_DOMAINS: array<array>, PRIVATE_DOMAINS: array<array>} $rules
     */
    private function __construct(private readonly array $rules)
    {
    }

    /**
     * Returns a new instance from a file path.
     *
     * @param null|resource $context
     *
     * @throws UnableToLoadResource If the rules can not be loaded from the path
     * @throws UnableToLoadPublicSuffixList If the rules contain in the resource are invalid
     */
    public static function fromPath(string $path, $context = null): self
    {
        return self::fromString(Stream::getContentAsString($path, $context));
    }

    /**
     * Returns a new instance from a string.
     *
     * @throws UnableToLoadPublicSuffixList If the rules contain in the resource are invalid
     */
    public static function fromString(Stringable|string $content): self
    {
        return new self(self::parse((string) $content));
    }

    /**
     * Convert the Public Suffix List into an associative, multidimensional array.
     *
     * @return array{ICANN_DOMAINS: array<array>, PRIVATE_DOMAINS: array<array>}
     */
    private static function parse(string $content): array
    {
        $rules = [self::ICANN_DOMAINS => [], self::PRIVATE_DOMAINS => []];
        $section = '';
        $file = new SplTempFileObject();
        $file->fwrite($content);
        $file->setFlags(SplFileObject::DROP_NEW_LINE | SplFileObject::READ_AHEAD | SplFileObject::SKIP_EMPTY);
        /** @var string $line */
        foreach ($file as $line) {
            $section = self::getSection($section, $line);
            if (in_array($section, [self::PRIVATE_DOMAINS, self::ICANN_DOMAINS], true) && !str_contains($line, '//')) {
                $rules[$section] = self::addRule($rules[$section], explode('.', $line));
            }
        }

        return $rules;
    }

    /**
     * Returns the section type for a given line.
     */
    private static function getSection(string $section, string $line): string
    {
        if (1 === preg_match(self::REGEX_PSL_SECTION, $line, $matches)) {
            return self::PSL_SECTION[$matches['type']][$matches['point']];
        }

        return $section;
    }

    /**
     * Recursive method to build the array representation of the Public Suffix List.
     *
     * This method is based heavily on the code found in generateEffectiveTLDs.php
     *
     * @see https://github.com/usrflo/registered-domain-libs/blob/master/generateEffectiveTLDs.php
     * A copy of the Apache License, Version 2.0, is provided with this distribution
     *
     * @param array<array> $list Initially an empty array, this eventually becomes the array representation of a
     *                           Public Suffix List section
     * @param array<string> $ruleParts One line (rule) from the Public Suffix List exploded on '.', or the remaining
     *                                 portion of that array during recursion
     *
     * @throws UnableToLoadPublicSuffixList if the domain name can not be converted using IDN to ASCII algorithm
     *
     * @return array<array>
     */
    private static function addRule(array $list, array $ruleParts): array
    {
        // Adheres to canonicalization rule from the "Formal Algorithm" section
        // of https://publicsuffix.org/list/
        // "The domain and all rules must be canonicalized in the normal way
        // for hostnames - lower-case, Punycode (RFC 3492)."
        try {
            /** @var string $line */
            $line = array_pop($ruleParts);
            $rule = Idna::toAscii($line, Idna::IDNA2008_ASCII)->result();
        } catch (CannotProcessHost $exception) {
            throw UnableToLoadPublicSuffixList::dueToInvalidRule($line ?? null, $exception);
        }

        $isDomain = true;
        if (str_starts_with($rule, '!')) {
            $rule = substr($rule, 1);
            $isDomain = false;
        }

        if (isset($list[$rule]) && [] === $list[$rule]) {
            $list[$rule] = [self::DOMAIN_RULE_MARKER => ''];
        }

        if (!isset($list[$rule])) {
            $list[$rule] = $isDomain ? [] : ['!' => ''];
        }

        if ($isDomain && [] !== $ruleParts) {
            $list[$rule] = self::addRule($list[$rule], $ruleParts);
        }

        return $list;
    }

    /**
     * @param array{rules:array{ICANN_DOMAINS: array<array>, PRIVATE_DOMAINS: array<array>}} $properties
     */
    public static function __set_state(array $properties): self
    {
        return new self($properties['rules']);
    }

    public function resolve(DomainNameProvider|Host|Stringable|string|int|null $host): ResolvedDomainName
    {
        try {
            return $this->getCookieDomain($host);
        } catch (UnableToResolveDomain $exception) {
            return ResolvedDomain::fromUnknown($exception->domain());
        } catch (SyntaxError) {
            return ResolvedDomain::fromUnknown(Domain::fromIDNA2008(null));
        }
    }

    public function getCookieDomain(DomainNameProvider|Host|Stringable|string|int|null $host): ResolvedDomainName
    {
        $domain = $this->validateDomain($host);
        [$suffixLength, $section] = $this->resolveSuffix($domain->withoutRootLabel(), self::UNKNOWN_DOMAINS);

        return match (true) {
            self::ICANN_DOMAINS === $section => ResolvedDomain::fromICANN($domain, $suffixLength),
            self::PRIVATE_DOMAINS === $section => ResolvedDomain::fromPrivate($domain, $suffixLength),
            default => ResolvedDomain::fromUnknown($domain, $suffixLength),
        };
    }

    public function getICANNDomain(DomainNameProvider|Host|Stringable|string|int|null $host): ResolvedDomainName
    {
        $domain = $this->validateDomain($host);
        [$suffixLength, $section] = $this->resolveSuffix($domain, self::ICANN_DOMAINS);
        if (self::ICANN_DOMAINS !== $section) {
            throw UnableToResolveDomain::dueToMissingSuffix($domain, 'ICANN');
        }

        return ResolvedDomain::fromICANN($domain, $suffixLength);
    }

    public function getPrivateDomain(DomainNameProvider|Host|Stringable|string|int|null $host): ResolvedDomainName
    {
        $domain = $this->validateDomain($host);
        [$suffixLength, $section] = $this->resolveSuffix($domain, self::PRIVATE_DOMAINS);
        if (self::PRIVATE_DOMAINS !== $section) {
            throw UnableToResolveDomain::dueToMissingSuffix($domain, 'private');
        }

        return ResolvedDomain::fromPrivate($domain, $suffixLength);
    }

    /**
     * Assert the domain is valid and is resolvable.
     *
     * @throws SyntaxError If the domain is invalid
     * @throws UnableToResolveDomain If the domain can not be resolved
     */
    private function validateDomain(DomainNameProvider|Host|Stringable|string|int|null $domain): DomainName
    {
        if ($domain instanceof DomainNameProvider) {
            $domain = $domain->domain();
        }

        if (!$domain instanceof DomainName) {
            $domain = Domain::fromIDNA2008($domain);
        }

        return $domain;
    }

    /**
     * Returns the length and the section of the resolved effective top level domain.
     *
     * @param Rules::UNKNOWN_DOMAINS|Rules::ICANN_DOMAINS|Rules::PRIVATE_DOMAINS $section
     *
     * @return array{0: int, 1:Rules::UNKNOWN_DOMAINS|Rules::ICANN_DOMAINS|Rules::PRIVATE_DOMAINS}
     */
    private function resolveSuffix(DomainName $domain, string $section): array
    {
        $icannSuffixLength = $this->getPublicSuffixLengthFromSection($domain, self::ICANN_DOMAINS);
        if (1 > $icannSuffixLength) {
            return [1, self::UNKNOWN_DOMAINS];
        }

        if (self::ICANN_DOMAINS === $section) {
            return [$icannSuffixLength, self::ICANN_DOMAINS];
        }

        $privateSuffixLength = $this->getPublicSuffixLengthFromSection($domain, self::PRIVATE_DOMAINS);
        if ($privateSuffixLength > $icannSuffixLength) {
            return [$privateSuffixLength, self::PRIVATE_DOMAINS];
        }

        return [$icannSuffixLength, self::ICANN_DOMAINS];
    }

    /**
     * Returns the public suffix label count for a domain name according to a PSL section.
     */
    private function getPublicSuffixLengthFromSection(DomainName $domain, string $section): int
    {
        $rules = $this->rules[$section];
        $labelCount = 0;
        foreach ($domain->toAscii() as $label) {
            //match exception rule
            if (isset($rules[$label]['!'])) {
                return $labelCount;
            }

            //match wildcard rule
            if (array_key_exists('*', $rules)) {
                ++$labelCount;

                return $labelCount;
            }

            //no match found
            if (!array_key_exists($label, $rules)) {
                if (self::PRIVATE_DOMAINS !== $section) {
                    return $labelCount;
                }

                // Suffix MATCHES default domain
                if (array_key_exists(self::DOMAIN_RULE_MARKER, $rules)) {
                    return $labelCount;
                }

                // Suffix MUST be fully matched else no suffix is found for private domain
                if (self::hasRemainingRules($rules)) {
                    return 0;
                }

                return $labelCount;
            }

            ++$labelCount;
            /** @var array<array-key, mixed> $rules */
            $rules = $rules[$label];
        }

        return $labelCount;
    }

    private static function hasRemainingRules(array $rules): bool
    {
        foreach ($rules as $rule) {
            if ([] !== $rule) {
                return true;
            }
        }

        return false;
    }
}