#!/usr/bin/env perl

#   Licensed to the Apache Software Foundation (ASF) under one
#   or more contributor license agreements.  See the NOTICE file
#   distributed with this work for additional information
#   regarding copyright ownership.  The ASF licenses this file
#   to you under the Apache License, Version 2.0 (the
#   "License"); you may not use this file except in compliance
#   with the License.  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

# Script to decode via header
#
# @File traffic_via.pl
# @Author Meera Mosale Nataraja
#
# Usage: Use it in 2 ways
# 1. Pass Via Header with -s option \n";
#    traffic_via [-s viaheader]";
#           or
# 2. Pipe curl output
#    curl -v -H "X-Debug: Via" http://ats_server:port 2>&1| ./traffic_via.pl
#

use strict;
use warnings;
use Data::Dumper qw(Dumper);
use Getopt::Long;

my $via_header;
my $help;

#Proxy request header flags and titles
my @proxy_header_array = (
    {
        "Request headers received from client", {
            'I' => "IMS",
            'C' => "cookie",
            'E' => "error in request",
            'S' => "simple request (not conditional)",
            'N' => "no-cache",
            ' ' => "unknown",
        },
    }, {
        "Result of Traffic Server cache lookup for URL", {
            'A' => "in cache, not acceptable (a cache \"MISS\")",
            'H' => "in cache, fresh (a cache \"HIT\")",
            'S' => "in cache, stale (a cache \"MISS\")",
            'R' => "in cache, fresh Ram hit (a cache \"HIT\")",
            'M' => "miss (a cache \"MISS\")",
            ' ' => "no cache lookup",
        },
    }, {
        "Response information received from origin server", {
            'E' => "error in response",
            ' ' => "no server connection needed",
            'S' => "connection opened successfully",
            'N' => "not-modified",
        }
    }, {
        "Result of document write-to-cache:", {
            'U' => "updated old cache copy",
            'D' => "cached copy deleted",
            'W' => "written into cache (new copy)",
            ' ' => "no cache write performed",
        },
    }, {
        "Proxy operation result", {
            'R' => "origin server revalidated",
            ' ' => "unknown",
            'S' => "served or connection opened successfully",
            'N' => "not-modified",
        },
    }, {
        "Error codes (if any)", {
            'A' => "authorization failure",
            'H' => "header syntax unacceptable",
            'C' => "connection to server failed",
            'T' => "connection timed out",
            'S' => "server related error",
            'D' => "dns failure",
            'N' => "no error",
            'F' => "request forbidden",
            'L' => "loop detected",
        },
    }, {
        "Tunnel info", {
            ' ' => "no tunneling",
            'U' => "tunneling because of url (url suggests dynamic content)",
            'M' => "tunneling due to a method (e.g. CONNECT)",
            'O' => "tunneling because cache is turned off",
            'F' => "tunneling due to a header field (such as presence of If-Range header)",
            'N' => "tunneling due to no forward",
        },
    }, {
        "Cache Type", {
            ' ' => "unknown",
            'I' => "icp",
            'C' => "cache",
        },
    }, {
        "Cache Lookup Result", {
            ' ' => "cache miss or no cache lookup",
            'S' => "cache hit, but expired",
            'U' => "cache hit, but client forces revalidate (e.g. Pragma: no-cache)",
            'D' => "cache hit, but method forces revalidated (e.g. ftp, not anonymous)",
            'I' => "conditional miss (client sent conditional, fresh in cache, returned 412)",
            'H' => "cache hit",
            'M' => "cache miss (url not in cache)",
            'C' => "cache miss (url not in cache)",
            'N' => "conditional hit (client sent conditional, doc fresh in cache, returned 304)",
        },
    }, {
        "Parent proxy connection status", {
            ' ' => "no parent proxy or unknown",
            'S' => "connection opened successfully",
            'F' => "connection open failed",
        },

    }, {
        "Origin server connection status", {
            ' ' => "no server connection needed",
            'S' => "connection opened successfully",
            'F' => "connection open failed",
        },
    },
);

##Print script usage
sub usage()
{
    print "\nPass Via Header with -s option \n";
    print "Usage: traffic_via [-s viaheader]";
    print "\n        or          \n";
    print "\nPipe curl command output to this program";
    print "\nEg: curl xxxx | traffic_via\n";
    print "\n-h for help\n";
    exit;
}

#Subroutine to decode via header
sub decode_via_header($)
{
    my ($header) = @_;
    my $hdrLength;
    my $newHeader;

    #Check via header syntax
    if ($header =~ /([a-zA-Z: ]+)/) {
        #Get via header length
        $hdrLength = length($header);

        # Valid Via header length is 22 or 6.
        # When Via header length is 22, it will have both proxy request header result and operational results.
        if ($hdrLength == 22) {
            #Split via header: proxy result and operational result
            $newHeader = join('', split(':', $header));
        } elsif ($hdrLength == 6) {
            $newHeader = $header;
        } elsif ($hdrLength == 5) {
            # When Via header length is 5, it might be missing last field. Fill it and decode header.
            $newHeader = $header . " ";
        } else {
            # Invalid header size, come out.
            print "\nInvalid VIA header. VIA header length should be 6 or 22 characters\n";
            return;
        }

        convert_header_to_array($newHeader);
    }

}

sub convert_header_to_array($)
{
    my ($viaHeader) = @_;
    my @ResultArray;
    #Convert string header into character array
    while ($viaHeader =~ /(.)/g) {
        #Only capital letters indicate flags
        if ($1 !~ m/[a-z;]+/) {
            push(@ResultArray, $1);
        }
    }
    print "Via Header Details:\n";
    for (my $arrayIndex = 0; $arrayIndex < scalar(@ResultArray); $arrayIndex++) {
        get_via_header_flags(\@proxy_header_array, $arrayIndex, $ResultArray[$arrayIndex]);
    }
}

my %valid_keys = ('main' => {
                    'u' => 1,
                    'c' => 1,
                    's' => 1,
                    'f' => 1,
                    'p' => 1,
                    'e' => 1,
                    },
                  'detail' => {
                    't' => 1,
                    'c' => 1,
                    'p' => 1,
                    's' => 1,
                  }
);

sub valid_char ($$)
{
    my($char, $hash) = @_;

    return exists $hash->{$char}
}

sub validate_keys($)
{
    my($viaHeader) = @_;
    my($main, $detail) = split(/[:;]/, $viaHeader);
    my $running_main = 1;
    my $return_value_valid = 1;

    foreach my $group ($main, $detail) {
        next if !defined $group;

        while ($group =~ /([a-z])/g) {
            my $char = $1;

            my $valid = 0;
            if ($running_main) {
                $valid = valid_char($char, $valid_keys{main});
            } else {
                $valid = valid_char($char, $valid_keys{detail});
            }
            if (! $valid) {
                print "traffic_via: Invalid VIA header character: $char\n";
                $return_value_valid = 0;
            }
        }
        $running_main = 0;
    }
    return $return_value_valid;
}

#Get values from header arrays
sub get_via_header_flags($$$)
{
    my ($arrayName, $inputIndex, $flag) = @_;

    my %flagValues;
    my @flagKeys;
    my %flags;
    my @keys;

    my @array = @$arrayName;

    %flagValues = %{$array[$inputIndex]};
    @flagKeys   = keys(%flagValues);

    foreach my $keyEntry (@flagKeys) {
        printf("%-55s", $keyEntry);
        %flags = %{$flagValues{$keyEntry}};
        @keys  = keys(%flags);
        foreach my $key (@keys) {
            if ($key =~ /$flag/) {
                #print $flags{$key};
                printf(":%s", $flags{$key});
                print "\n";
            }
        }
    }
}

# main
{
    if (@ARGV == 0) {
        #if passed through standard input
        my @userinput = <STDIN>;

        for my $element (@userinput) {
            #Pattern matching for Via
            if ($element =~ /Via:\s+\[([^\]]+)\]/i || $element =~ /\[([^\]]+)\]/ ) {
                #Search and grep via header
                my $via_string = $1;
                chomp($via_string);
                print "Via header is [$via_string], Length is ", length($via_string), "\n";
                last unless validate_keys($via_string);
                decode_via_header($via_string);
            }
        }
    } else {
        usage()
        if (
            !GetOptions(
                's=s'    => \$via_header,
                'help|?' => \$help
            )
            or defined $help
        );

        if (defined $via_header) {
            if ($via_header =~ /Via:\s+\[([^\]]+)\]/i || $via_header =~ /\[([^\]]+)\]/ || $via_header =~ /(.+)/) {
                #if passed through commandline dashed argument
                my $via_string = $1;
                print "Via header is [$via_string], Length is ", length($via_string), "\n";
                last unless validate_keys($via_string);
                decode_via_header($via_string);
            }
        }

    }
}