#!/usr/bin/ruby
#--
#-------------------------------------------------------------------------------
#++
#
# = Introduction
#
#  A script to reverse a specified change. This script re-adds files that
#  have been deleted; deletes files that were added; and reverses the edits
#  made within a single specified changelist.
#
# = What this script tries to do
#
#  This script runs the necessary Perforce commands to reverse the effects of
#  a change. Files that were added in the bad change will be deleted; files
#  deleted in the bad change will be re-added; and the edits in the bad
#  change will be backed out.
#
#  The script places all files it opens in a new pending changelist created
#  explicitly for this purpose.
#
#  If the change being backed out is old, the script will attempt to remerge
#  the subsequent changes with the revision prior to the bad change. It may
#  or may not succeed. If it doesn't, you will have some work to do. Note
#  that the older the change being backed out is, the higher the probability
#  of failure. 
#
# = What this script does NOT try to do
#
#  1. The script does not submit anything to the depot.
#
#  2. The script does not attempt to resolve merge conflicts
#
#  3. The script does not currently rebranch branched files that we deleted in
#     the bad change. This may work in a future version.
#
#  4. The script does not try to handle filetype changes.
#
#  5. The script doesn't handle symlinks well (and is unlikely to)
#
# = Usage
#
#   reversechange.rb [ -v <debuglevel> ] -c <changelist> 
#
# = Author
#
#  Tony Smith <tony@perforce.com> or <tony@smee.org>
#  Copyright (c) 2004 Perforce Software Inc.
#
# = License
#
#  Copyright (c) 1997-2008, Perforce Software, Inc.  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 PERFORCE SOFTWARE, INC. 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.
#  
# = Version
#
#  $Id: //guest/tony_smith/perforce/P4Rubylib/scripts/reversechange.rb#2 $
#
#--
#-------------------------------------------------------------------------------
#++

require "getoptlong"
require "P4"


#
# A class to handle the reversal of a change. This is in a class to allow
# others to derive from it and add/replace bits of it to suit.
#
class Reverser
    def initialize( p4, verbose=0 )
	@p4 	   = p4
	@conflicts = 0
	@verbose   = verbose
	@changelist = 0
    end

    attr_reader 	:p4

    @@CONF_MSG = "\n"							     +
    "Warning: Some conflicts remain. To complete this process you should:\n" + 
    "\n"								     +
    "  1. Use 'p4 resolve' or your GUI merge tool to complete the merge\n"   +
    "  2. Use 'p4 diff' to review the changes\n"			     +
    "  3. Use 'p4 submit -c %d' to submit your changelist\n"		     +
    "\n"

    @@OK_MSG = "\n"							     +
    "Success: All merges completed without conflicts. To complete this\n"    +
    "process you should:\n"						     +
    "\n"								     +
    "  1. Use 'p4 diff' to review the changes\n"			     +
    "  2. Use 'p4 submit -c %d' to submit your changelist\n"		     +
    "\n"


    #
    # Main interface - back out the specified change
    #
    def reverse( change )

	# Reset counter
	@conflicts = 0

	p4.exception_level = 1	# Ignore file(s) up-to-date warning
	p4.run_sync
	p4.exception_level = 2	# Now we want all warnings

	spec = p4.run_describe( change ).shift
	@changelist = mkchangelist( change )

	files 	= spec[ "depotFile" 	]
	revs	= spec[ "rev"		]
	actions	= spec[ "action" 	]
	types	= spec[ "type" 		]

	i = 0
	while( files[ i ] )
	    df = files[ i ]
	    ac = actions[ i ]
	    ty = types[ i ]
	    re = revs[ i ]

	    if( ac == "add" || ac == "branch" )
		reverse_add( df, re, ty )
	    elsif( ac == "delete" )
		reverse_delete( df, re, ty )
	    elsif( ac == "edit" || ac == "integrate" )
		reverse_edit( df, re, ty )
	    end
	    i += 1
	end

	if( @conflicts > 0 )
	    conflicts_warning()
	else
	    success_message()
	end
    end

    #########
    protected
    #########

    #
    # Create a new pending changelist
    #
    def mkchangelist( oldchange )
	spec = p4.fetch_change
	spec[ "Files" ] = Array.new
	spec[ "Jobs"  ] = Array.new
	spec[ "Description" ] = "Change to back out change ##{oldchange}"
	out = p4.save_change( spec ).shift
	if( out =~ /Change (\d+) created./ )
	    return $1
	end
	raise( RuntimeError,"Failed to create a pending changelist!\n\t#{out}" )
    end

    #
    # Reverse the effects of an add/branch - i.e. delete the file
    #
    def reverse_add( df, re, ty )
	message( 1, "\n[Reverse Add] #{df}##{re}..." )
	message( 2, "\tOpening head revision for delete..." )
	p4.run_delete( "-c", @changelist, df )
    end

    #
    # Reverse the effects of a delete - i.e. add the file. Could be cleverer
    # about deletes that result from integrations.
    #
    def reverse_delete( df, re, ty )
	message( 1, "\n[Reverse Delete] #{df}##{re}..." )
	prev = re.to_i - 1

	message( 2, "\tSyncing back to revision #{prev}..." )
	p4.run_sync( df + "##{prev}" )

	message( 2, "\tRe-adding file using revision ##{prev}..." )
	p4.run_add( "-c", @changelist, "-t", ty, df )
    end

    #
    # Reverse the effects of an edit operation. Since this change may
    # not be the most recent change to a file, we need to do a little
    # tap-dancing to get the reversal right. In a nutshell we:
    #
    # 1. Sync to the revision prior to the edit
    # 2. Open the file for edit at that revision
    # 3. Sync to the edited revision to schedule a resolve
    # 4. Use "p4 resolve -ay" to ignore the bad change
    # 5. Sync to the head revision
    # 6. Use "p4 resolve -am" to merge in subsequent changes if any
    #
    def reverse_edit( df, re, ty )
	message( 1, "\n[Reverse Edit] #{df}##{re}..." )
	prev = re.to_i - 1
	
	fs = p4.run_fstat( df ).shift
	if( fs[ "headAction" ] == "delete" )
	    message( 1, "\tNOT reversing edit - deleted at head revision." )
	    return
	end

	message( 2, "\tSyncing back to revision ##{prev}..." )
	p4.run_sync( df + "##{prev}" )
	
	message( 2, "\tOpening revision ##{prev} for edit..." ) 
	p4.run_edit( "-c", @changelist, df )
	
	message( 2, "\tSyncing to revision ##{re}..." ) 
	p4.run_sync( df + "##{re}" )
	
	message( 2, "\tIgnoring revision ##{re} in merge..." ) 
	p4.run_resolve( "-ay", df )
	
	begin
	    message( 2, "\tSyncing to head revision..." ) 
	    p4.run_sync( df )
	
	    message( 2,"\tAttempting to merge changes after revision ##{re}...")
	    attempt_merge( df )
	rescue P4Exception
	    if( p4.warnings[ 0 ] !~ /file.s. up-to-date/ )
		raise
	    end
	end
    end

    #
    # Attempt an automatic merge and keep a count of the number of files
    # with conflicts
    #
    def attempt_merge( df )
	out = p4.run_resolve( "-am", df )[-1]
	# Really only interested in the last line.
	if( out =~ /resolve skipped/ )
	    message( 2, "\tConflicts remain..." )
	    @conflicts += 1
	else
	    message( 2, "\tMerge succeeded..." )
	end
    end

    #
    # Warn the user there are still pending resolves that need to be done
    # manually
    #
    def conflicts_warning
	$stderr.puts( @@CONF_MSG % @changelist )
    end

    #
    # Write out the success message for the user on stdout.
    #
    def success_message
	puts( @@OK_MSG % @changelist )
    end

    #
    # Method to report output to the user - may be overridden by subclasses
    #
    def message( level, string )
	puts( string ) if @verbose >= level
    end
end


#
# Display usage information and exit
#
def croakusage
    puts( "Usage: reversechange.rb [-v <level> ] -c <change>" )
    exit( 0 )
end


#--
#-------------------------------------------------------------------------------
#		START OF MAIN SCRIPT
#-------------------------------------------------------------------------------
#++

changelist 	= nil
verbose		= 0

opts = GetoptLong.new(  [ "-c", 	GetoptLong::REQUIRED_ARGUMENT	],
			[ "-v", 	GetoptLong::REQUIRED_ARGUMENT   ] 
		     )

opts.each do
    |opt,arg|
    if( opt == "-c" )
	changelist = arg
    elsif( opt == "-v" )
	verbose = arg.to_i
    end
end

# Providing a changelist is mandatory
if( ! changelist )
    croakusage
end

begin
    p4 = P4.new
    p4.connect
    p4.debug = 1 if( verbose >= 3 )

    reverser = Reverser.new( p4, verbose )
    reverser.reverse( changelist )

rescue P4Exception
    if( p4.errors.length > 0 )
	$stderr.puts( "Perforce error(s) during script execution:" )
	p4.errors.each { |e| $stderr.puts( e ) }
    elsif( p4.warnings.length > 0 )
	$stderr.puts( "Perforce warning(s) during script execution:" )
	p4.warnings.each { |w| $stderr.puts( w ) }
    end
    exit( 1 )
end