# frozen_string_literal: true
require 'diff/lcs/block'
# A Hunk is a group of Blocks which overlap because of the context surrounding
# each block. (So if we're not using context, every hunk will contain one
# block.) Used in the diff program (bin/ldiff).
class Diff::LCS::Hunk
# Create a hunk using references to both the old and new data, as well as the
# piece of data.
def initialize(data_old, data_new, piece, flag_context, file_length_difference)
# At first, a hunk will have just one Block in it
@blocks = [Diff::LCS::Block.new(piece)]
if String.method_defined?(:encoding)
@preferred_data_encoding = data_old.fetch(0, data_new.fetch(0, '')).encoding
end
@data_old = data_old
@data_new = data_new
before = after = file_length_difference
after += @blocks[0].diff_size
@file_length_difference = after # The caller must get this manually
@max_diff_size = @blocks.map { |e| e.diff_size }.max
# Save the start & end of each array. If the array doesn't exist (e.g.,
# we're only adding items in this block), then figure out the line
# number based on the line number of the other file and the current
# difference in file lengths.
if @blocks[0].remove.empty?
a1 = a2 = nil
else
a1 = @blocks[0].remove[0].position
a2 = @blocks[0].remove[-1].position
end
if @blocks[0].insert.empty?
b1 = b2 = nil
else
b1 = @blocks[0].insert[0].position
b2 = @blocks[0].insert[-1].position
end
@start_old = a1 || (b1 - before)
@start_new = b1 || (a1 + before)
@end_old = a2 || (b2 - after)
@end_new = b2 || (a2 + after)
self.flag_context = flag_context
end
attr_reader :blocks
attr_reader :start_old, :start_new
attr_reader :end_old, :end_new
attr_reader :file_length_difference
# Change the "start" and "end" fields to note that context should be added
# to this hunk.
attr_accessor :flag_context
undef :flag_context=
def flag_context=(context) #:nodoc: # rubocop:disable Lint/DuplicateMethods
return if context.nil? or context.zero?
add_start = context > @start_old ? @start_old : context
@start_old -= add_start
@start_new -= add_start
old_size = @data_old.size
add_end =
if (@end_old + context) > old_size
old_size - @end_old
else
context
end
add_end = @max_diff_size if add_end >= old_size
@end_old += add_end
@end_new += add_end
end
# Merges this hunk and the provided hunk together if they overlap. Returns
# a truthy value so that if there is no overlap, you can know the merge
# was skipped.
def merge(hunk)
return unless overlaps?(hunk)
@start_old = hunk.start_old
@start_new = hunk.start_new
blocks.unshift(*hunk.blocks)
end
alias unshift merge
# Determines whether there is an overlap between this hunk and the
# provided hunk. This will be true if the difference between the two hunks
# start or end positions is within one position of each other.
def overlaps?(hunk)
hunk and (((@start_old - hunk.end_old) <= 1) or
((@start_new - hunk.end_new) <= 1))
end
# Returns a diff string based on a format.
def diff(format)
case format
when :old
old_diff
when :unified
unified_diff
when :context
context_diff
when :ed
self
when :reverse_ed, :ed_finish
ed_diff(format)
else
fail "Unknown diff format #{format}."
end
end
# Note that an old diff can't have any context. Therefore, we know that
# there's only one block in the hunk.
def old_diff
warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1
op_act = { '+' => 'a', '-' => 'd', '!' => 'c' }
block = @blocks[0]
# Calculate item number range. Old diff range is just like a context
# diff range, except the ranges are on one line with the action between
# them.
s = encode("#{context_range(:old)}#{op_act[block.op]}#{context_range(:new)}\n")
# If removing anything, just print out all the remove lines in the hunk
# which is just all the remove lines in the block.
unless block.remove.empty?
@data_old[@start_old..@end_old].each { |e| s << encode('< ') + e + encode("\n") }
end
s << encode("---\n") if block.op == '!'
unless block.insert.empty?
@data_new[@start_new..@end_new].each { |e| s << encode('> ') + e + encode("\n") }
end
s
end
private :old_diff
def unified_diff
# Calculate item number range.
s = encode("@@ -#{unified_range(:old)} +#{unified_range(:new)} @@\n")
# Outlist starts containing the hunk of the old file. Removing an item
# just means putting a '-' in front of it. Inserting an item requires
# getting it from the new file and splicing it in. We splice in
# +num_added+ items. Remove blocks use +num_added+ because splicing
# changed the length of outlist.
#
# We remove +num_removed+ items. Insert blocks use +num_removed+
# because their item numbers -- corresponding to positions in the NEW
# file -- don't take removed items into account.
lo, hi, num_added, num_removed = @start_old, @end_old, 0, 0
outlist = @data_old[lo..hi].map { |e| e.insert(0, encode(' ')) }
@blocks.each do |block|
block.remove.each do |item|
op = item.action.to_s # -
offset = item.position - lo + num_added
outlist[offset][0, 1] = encode(op)
num_removed += 1
end
block.insert.each do |item|
op = item.action.to_s # +
offset = item.position - @start_new + num_removed
outlist[offset, 0] = encode(op) + @data_new[item.position]
num_added += 1
end
end
s << outlist.join(encode("\n"))
end
private :unified_diff
def context_diff
s = encode("***************\n")
s << encode("*** #{context_range(:old)} ****\n")
r = context_range(:new)
# Print out file 1 part for each block in context diff format if there
# are any blocks that remove items
lo, hi = @start_old, @end_old
removes = @blocks.reject { |e| e.remove.empty? }
if removes
outlist = @data_old[lo..hi].map { |e| e.insert(0, encode(' ')) }
removes.each do |block|
block.remove.each do |item|
outlist[item.position - lo].insert(0, encode(block.op)) # - or !
end
end
s << outlist.join("\n")
end
s << encode("\n--- #{r} ----\n")
lo, hi = @start_new, @end_new
inserts = @blocks.reject { |e| e.insert.empty? }
if inserts
outlist = @data_new[lo..hi].collect { |e| e.insert(0, encode(' ')) }
inserts.each do |block|
block.insert.each do |item|
outlist[item.position - lo].insert(0, encode(block.op)) # - or !
end
end
s << outlist.join("\n")
end
s
end
private :context_diff
def ed_diff(format)
op_act = { '+' => 'a', '-' => 'd', '!' => 'c' }
warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1
s =
if format == :reverse_ed
encode("#{op_act[@blocks[0].op]}#{context_range(:old)}\n")
else
encode("#{context_range(:old, ' ')}#{op_act[@blocks[0].op]}\n")
end
unless @blocks[0].insert.empty?
@data_new[@start_new..@end_new].each do |e| s << e + encode("\n") end
s << encode(".\n")
end
s
end
private :ed_diff
# Generate a range of item numbers to print. Only print 1 number if the
# range has only one item in it. Otherwise, it's 'start,end'
def context_range(mode, op = ',') # rubocop:disable Naming/UncommunicativeMethodParamName
case mode
when :old
s, e = (@start_old + 1), (@end_old + 1)
when :new
s, e = (@start_new + 1), (@end_new + 1)
end
s < e ? "#{s}#{op}#{e}" : e.to_s
end
private :context_range
# Generate a range of item numbers to print for unified diff. Print number
# where block starts, followed by number of lines in the block
# (don't print number of lines if it's 1)
def unified_range(mode)
case mode
when :old
s, e = (@start_old + 1), (@end_old + 1)
when :new
s, e = (@start_new + 1), (@end_new + 1)
end
length = e - s + 1
first = length < 2 ? e : s # "strange, but correct"
length == 1 ? first.to_s : "#{first},#{length}"
end
private :unified_range
if String.method_defined?(:encoding)
def encode(literal, target_encoding = @preferred_data_encoding)
literal.encode target_encoding
end
def encode_as(string, *args)
args.map { |arg| arg.encode(string.encoding) }
end
else
def encode(literal, _target_encoding = nil)
literal
end
def encode_as(_string, *args)
args
end
end
private :encode
private :encode_as
end