package Urupam::Validation;

use Mojo::Base -base;
use Mojo::URL;
use Mojo::UserAgent;
use Mojo::Promise;
use Urupam::Utils qw(sanitize_url);

my $MAX_URL_LENGTH  = 2048;
my $CONNECT_TIMEOUT = 10;
my $REQUEST_TIMEOUT = 10;
my $MAX_REDIRECTS   = 3;

my $DNS_ERROR_PATTERN =
qr/Name or service not known|getaddrinfo failed|Could not resolve|DNS|hostname|Name resolution|nodename nor servname provided/i;
my $SSL_ERROR_PATTERN        = qr/SSL|certificate|TLS|verification failed/i;
my $CONNECTION_ERROR_PATTERN = qr/Connection refused|Can't connect|timeout/i;

my $PRIVATE_IP_PATTERN =
  qr/^(127\.|192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[01])\.)/;

my @BLOCKED_DOMAINS = qw(
  localhost 127.0.0.1 0.0.0.0 ::1
);

has ua => sub {
    my $self = shift;
    Mojo::UserAgent->new(
        connect_timeout => $self->connect_timeout,
        request_timeout => $self->request_timeout,
        max_redirects   => $self->max_redirects,
        insecure        => 0
    );
};

has connect_timeout => sub { $CONNECT_TIMEOUT };
has request_timeout => sub { $REQUEST_TIMEOUT };
has max_redirects   => sub { $MAX_REDIRECTS };

sub _parse_url {
    my ( $self, $url ) = @_;
    return undef unless defined $url;
    my $parsed;
    eval { $parsed = Mojo::URL->new($url); 1 } or return undef;
    return $parsed;
}

sub _classify_error {
    my ( $self, $err_str ) = @_;

    return 'ssl'        if $err_str =~ $SSL_ERROR_PATTERN;
    return 'dns'        if $err_str =~ $DNS_ERROR_PATTERN;
    return 'connection' if $err_str =~ $CONNECTION_ERROR_PATTERN;
    return 'unknown';
}

sub _format_error_message {
    my ( $self, $error_type, $err_str ) = @_;

    return "SSL certificate error: $err_str" if $error_type eq 'ssl';
    return "DNS resolution failed: $err_str" if $error_type eq 'dns';
    return "Cannot reach URL: $err_str"      if $error_type eq 'connection';
    return "URL validation failed: $err_str";
}

sub is_valid_url_length {
    my ( $self, $url ) = @_;
    return 0 unless defined $url && length($url) > 0;
    return length($url) <= $MAX_URL_LENGTH;
}

sub _is_valid_ipv4 {
    my ( $self, $ip ) = @_;
    return 0 unless defined $ip;
    return 0 unless $ip =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/;
    my ( $a, $b, $c, $d ) = ( $1, $2, $3, $4 );
    return
         $a >= 0
      && $a <= 255
      && $b >= 0
      && $b <= 255
      && $c >= 0
      && $c <= 255
      && $d >= 0
      && $d <= 255;
}

sub _is_private_ipv4 {
    my ( $self, $ip ) = @_;
    return 0 unless $self->_is_valid_ipv4($ip);
    return $ip =~ $PRIVATE_IP_PATTERN;
}

sub _is_private_ipv6 {
    my ( $self, $ip ) = @_;
    $ip = lc($ip);
    $ip =~ s/^\[|\]$//g;
    return
         $ip eq '::1'
      || $ip eq '::'
      || $ip =~ /^::ffff:(127\.|192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[01])\.)/;
}

sub is_blocked_url {
    my ( $self, $url ) = @_;
    return 0 unless defined $url;

    my $parsed = $self->_parse_url($url);
    return 0 unless $parsed;

    my $host = lc( $parsed->host // '' );

    for my $blocked (@BLOCKED_DOMAINS) {
        return 1 if $host eq $blocked;
    }

    if ( $self->_is_private_ipv4($host) ) {
        return 1;
    }

    if ( $self->_is_private_ipv6($host) ) {
        return 1;
    }

    return 0;
}

sub check_url_reachable {
    my ( $self, $url ) = @_;

    return Mojo::Promise->reject('URL is required')
      unless defined $url && length($url) > 0;

    return $self->ua->head_p($url)->then(
        sub {
            my $tx   = shift;
            my $code = $tx->result->code;

            return 1 if $code >= 200 && $code < 400;
            return Mojo::Promise->reject("URL returned $code error")
              if $code >= 400;
            return Mojo::Promise->reject(
                "URL returned unexpected status: $code");
        }
    )->catch(
        sub {
            my $err        = shift;
            my $err_str    = "$err";
            my $error_type = $self->_classify_error($err_str);
            return Mojo::Promise->reject(
                $self->_format_error_message( $error_type, $err_str ) );
        }
    );
}

sub check_ssl_certificate {
    my ( $self, $url ) = @_;

    return Mojo::Promise->reject('URL is required')
      unless defined $url && length($url) > 0;

    my $parsed = $self->_parse_url($url);
    return Mojo::Promise->resolve(1)
      unless $parsed && $parsed->scheme && $parsed->scheme eq 'https';

    return $self->ua->head_p($url)->then( sub { return 1; } )->catch(
        sub {
            my $err        = shift;
            my $err_str    = "$err";
            my $error_type = $self->_classify_error($err_str);

            if ( $error_type eq 'ssl' ) {
                return Mojo::Promise->reject(
                    "Invalid SSL certificate: $err_str");
            }

            return Mojo::Promise->reject(
                $self->_format_error_message( $error_type, $err_str ) );
        }
    );
}

sub validate_short_code {
    my ( $self, $code ) = @_;
    return defined $code && length($code) > 0 && $code =~ /^[0-9a-zA-Z\-_]+$/;
}

sub validate_url_with_checks {
    my ( $self, $url ) = @_;

    return Mojo::Promise->reject('URL is required')
      unless defined $url && length($url) > 0;

    my $sanitized = sanitize_url($url);
    return Mojo::Promise->reject('Invalid URL format')
      unless defined $sanitized;

    my $parsed = $self->_parse_url($sanitized);
    return Mojo::Promise->reject('Invalid URL format') unless $parsed;
    return Mojo::Promise->reject('Invalid URL format')
      unless $parsed->scheme && $parsed->scheme =~ /^https?$/i;
    return Mojo::Promise->reject('Invalid URL format') unless $parsed->host;

    return Mojo::Promise->reject(
        "URL exceeds maximum length of $MAX_URL_LENGTH characters")
      unless $self->is_valid_url_length($sanitized);
    return Mojo::Promise->reject(
        'This URL cannot be shortened (blocked domain or local address)')
      if $self->is_blocked_url($sanitized);

    my $ssl_check =
        $parsed->scheme eq 'https'
      ? $self->check_ssl_certificate($sanitized)
      : Mojo::Promise->resolve(1);

    return $ssl_check->then(
        sub { return $self->check_url_reachable($sanitized); } )
      ->then( sub { return $sanitized; } );
}

1;