#!/usr/bin/env perl

# Copyright (c) 2025, R. W. Rodolico
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# compare_reports
# Compares old and new sysinfo reports for v3.7.1 compatibility rules.
#
# Revision History:
# 2026-10-11 Copilot v1.0.0 r? initial v3.8.0 compatibility comparator
# 2026-10-12 Copilot v1.0.1 r? segment-safe path handling for dotted keys

use warnings;
use strict;

use version;
our $VERSION = version->declare('v1.0.1');

use YAML::Tiny;

#######################################################
#
# usage()
#
# Prints usage and exits with error.
#
# Parameters:
#   none
#
# Returns:
#   none
#
# Side Effects:
#   terminates process with die
#
#######################################################
sub usage {
   die "Usage: compare_reports OLD.yaml NEW.yaml\n";
}

#######################################################
#
# loadReport( $path )
#
# Loads YAML report file while ignoring optional sysinfo
# comment preamble line.
#
# Parameters:
#   $path - report file path
#
# Returns:
#   hash reference report document
#
# Side Effects:
#   reads from filesystem
#
#######################################################
sub loadReport {
   my $path = shift;
   open my $fh, '<', $path or die "Could not read $path: $!\n";
   my @lines = <$fh>;
   close($fh);

   if (@lines && $lines[0] =~ /^#sysinfo:\s+/) {
      shift @lines;
   }

   my $yaml = YAML::Tiny->read_string(join('', @lines));
   die "Could not parse YAML from $path\n" unless $yaml && ref($yaml->[0]) eq 'HASH';
   return $yaml->[0];
}

#######################################################
#
# nodeType( $value )
#
# Returns normalized node type string for scalar, map,
# or list.
#
# Parameters:
#   $value - perl data value
#
# Returns:
#   scalar node type string
#
# Side Effects:
#   none
#
#######################################################
sub nodeType {
   my $value = shift;
   return 'map' if ref($value) eq 'HASH';
   return 'list' if ref($value) eq 'ARRAY';
   return 'scalar';
}

#######################################################
#
# pathKey( $segments )
#
# Builds an internal unique path key from path segments.
#
# Parameters:
#   $segments - array reference of path segments
#
# Returns:
#   scalar key string joined by tab
#
# Side Effects:
#   none
#
#######################################################
sub pathKey {
   my $segments = shift;
   return join("\t", @{$segments});
}

#######################################################
#
# pathDisplay( $segments )
#
# Converts path segments to display string.
#
# Parameters:
#   $segments - array reference of path segments
#
# Returns:
#   scalar display path joined by dot
#
# Side Effects:
#   none
#
#######################################################
sub pathDisplay {
   my $segments = shift;
   return join('.', @{$segments});
}

#######################################################
#
# flattenTypesAndValues( $node, $segments, $types, $values, $paths )
#
# Flattens nested report data into type/value maps keyed by
# internal segment-safe path keys.
#
# Parameters:
#   $node     - current node
#   $segments - array reference of current path segments
#   $types    - hash reference pathKey => type
#   $values   - hash reference pathKey => scalar value
#   $paths    - hash reference pathKey => segment array
#
# Returns:
#   none
#
# Side Effects:
#   populates hashes by reference
#
#######################################################
sub flattenTypesAndValues {
   my ($node, $segments, $types, $values, $paths) = @_;

   my $type = nodeType($node);
   if (@{$segments}) {
      my $key = pathKey($segments);
      $types->{$key} = $type;
      $paths->{$key} = [@{$segments}];
      if ($type eq 'scalar') {
         $values->{$key} = defined($node) ? "$node" : '';
      }
   }

   if ($type eq 'map') {
      foreach my $key (sort keys %{$node}) {
         my @childPath = (@{$segments}, $key);
         flattenTypesAndValues($node->{$key}, \@childPath, $types, $values, $paths);
      }
   } elsif ($type eq 'list') {
      for (my $i = 0; $i < @{$node}; $i++) {
         my @childPath = (@{$segments}, $i);
         flattenTypesAndValues($node->[$i], \@childPath, $types, $values, $paths);
      }
   }
}

#######################################################
#
# isAllowedDifference( $segments )
#
# Determines whether a scalar path is in the allowed
# difference list from Spec section 1.2.
#
# Parameters:
#   $segments - array reference of path segments
#
# Returns:
#   boolean true when difference is allowed
#
# Side Effects:
#   none
#
#######################################################
sub isAllowedDifference {
   my $segments = shift;

   return 1 if @{$segments} == 2 && $segments->[0] eq 'report' && ($segments->[1] eq 'date' || $segments->[1] eq 'version');
   return 1 if @{$segments} == 3 && $segments->[0] eq 'software' && $segments->[1] eq 'sysinfo-client' && $segments->[2] eq 'version';
   return 1 if @{$segments} == 2 && $segments->[0] eq 'system' && ($segments->[1] eq 'uptime' || $segments->[1] eq 'last_boot' || $segments->[1] eq 'Power Draw');
   return 1 if @{$segments} == 2 && $segments->[0] eq 'system' && $segments->[1] =~ /^Power Current \d+$/;
   return 1 if @{$segments} == 2 && $segments->[0] eq 'system' && $segments->[1] =~ /^Power Voltage \d+$/;
   return 1 if @{$segments} == 3 && $segments->[0] eq 'diskinfo' && ($segments->[2] eq 'used' || $segments->[2] eq 'size');
   return 1 if @{$segments} == 2 && $segments->[0] eq 'attributes' && $segments->[1] =~ / (uptime|writes|Sector Size)$/;
   return 1 if @{$segments} == 4 && $segments->[0] eq 'xen' && $segments->[1] eq 'virtual' && ($segments->[3] eq 'memory' || $segments->[3] eq 'numcpu');

   return 0;
}

usage() unless @ARGV == 2;
my ($oldPath, $newPath) = @ARGV;

my $old = loadReport($oldPath);
my $new = loadReport($newPath);

my (%oldTypes, %newTypes, %oldValues, %newValues, %oldPaths, %newPaths);
flattenTypesAndValues($old, [], \%oldTypes, \%oldValues, \%oldPaths);
flattenTypesAndValues($new, [], \%newTypes, \%newValues, \%newPaths);

my @missing;
my @typeChanges;
my @valueDiffs;

foreach my $pathKey (sort keys %oldTypes) {
   if (!exists $newTypes{$pathKey}) {
      push @missing, pathDisplay($oldPaths{$pathKey});
      next;
   }

   if ($newTypes{$pathKey} ne $oldTypes{$pathKey}) {
      my $display = pathDisplay($oldPaths{$pathKey});
      push @typeChanges, "$display old=$oldTypes{$pathKey} new=$newTypes{$pathKey}";
      next;
   }

   next unless $oldTypes{$pathKey} eq 'scalar';
   my $oldValue = exists $oldValues{$pathKey} ? $oldValues{$pathKey} : '';
   my $newValue = exists $newValues{$pathKey} ? $newValues{$pathKey} : '';
   next if $oldValue eq $newValue;
   next if isAllowedDifference($oldPaths{$pathKey});

   push @valueDiffs, pathDisplay($oldPaths{$pathKey});
}

print "Missing old key paths in NEW:\n";
print scalar(@missing) ? join("\n", map { "  $_" } @missing) . "\n" : "  (none)\n";

print "Type changes:\n";
print scalar(@typeChanges) ? join("\n", map { "  $_" } @typeChanges) . "\n" : "  (none)\n";

print "Value differences outside allowed list:\n";
print scalar(@valueDiffs) ? join("\n", map { "  $_" } @valueDiffs) . "\n" : "  (none)\n";

exit((@missing || @typeChanges) ? 1 : 0);