#!/usr/bin/env ruby
# Inspired by diff-so-fancy; wrapper around diff-highlight
# https://github.com/stevemao/diff-so-fancy
# [commit: 0ea7c129420c57ec0384a704325e27c41f8f450d,
#  last commit checked: 3adf0114da99643ec53a16253a3d6f42390e4c19 (2017-04-04)]
#TODO: use git-config
#TODO: work with 'git log -p --graph'

require "simplecolor"
SimpleColor.mix_in_string
begin
	require "shell_helpers"
rescue LoadError
end

module GitHelpers
	class GitDiff
		def self.output(gdiff, **opts)
			if gdiff.respond_to?(:each_line)
				enum=gdiff.each_line
			else
				enum=gdiff.each
			end
			self.new(enum, **opts).output
		end

		attr_reader :output
		include Enumerable
		NoNewLine="\\ No newline at end of file\n"

		def initialize(diff,**opts)
			@diff=diff #Assume diff is a line iterator ['gitdiff'.each_line]
			@current=0
			@mode=:unknown
			@opts=opts
			@opts[:color]=@opts.fetch(:color,true)
			#modes: 
			#- unknown (temp mode)
			#- commit
			#- meta
			#- submodule_header
			#- submodule
			#- diff_header
			#- hunk
			@colors={meta: [:bold]}
		end

		def output_line(l)
			@output << l.chomp+"\n"
		end
		def output_lines(lines)
			lines.each {|l| output_line l}
		end
		def output
			each {|l| puts l}
		end

		def next_mode(nmode)
			@next_mode=nmode
		end
		def update_mode
			@start_mode=false
			@next_mode && change_mode(@next_mode)
			@next_mode=nil
		end
		def change_mode(nmode)
			@start_mode=true
			send :"end_#{@mode}" unless @mode==:unknown
			@mode=nmode
			send :"new_#{@mode}" unless @mode==:unknown
		end

		def new_commit; @commit={}; end
		def end_commit; end
		def new_meta; end
		def end_meta; end
		def new_hunk; end
		def end_hunk; end
		def new_submodule_header; @submodule={}; end
		def end_submodule_header; end
		def new_submodule; end
		def end_submodule; end
		def new_diff_header; @file={mode: :modify} end
		def end_diff_header; end

		def detect_new_diff_header
			@line =~ /^diff\s/
		end
		def detect_end_diff_header
			@line =~ /^\+\+\+\s/
		end

		def detect_new_hunk
			@line.match(/^@@+\s.*\s@@/)
		end
		def detect_end_hunk
			@hunk[:lines_seen].each_with_index.all? { |v,i| v==@hunk[:lines][i].first }
		end

		def handle_meta
			handle_line
		end

		def parse_hunk_header
			m=@line.match(/^@@+\s(.*)\s@@\s*(.*)/)
			hunks=m[1]
			@hunk={lines: []}
			@hunk[:header]=m[2]
			filenumber=0
			hunks.split.each do |hunk|
				hunkmode=hunk[0]
				hunk=hunk[1..-1]
				line,length=hunk.split(',').map(&:to_i)
				#handle hunks of the form @@ -1 +0,0 @@
				length,line=line,length unless length
				case hunkmode
				when '-'
					filenumber+=1
					@hunk[:lines][filenumber]=[length,line]
				when '+'
					@hunk[:lines][0]=[length,line]
				end
			end
			@hunk[:n]=@hunk[:lines].length
			@hunk[:lines_seen]=Array.new(@hunk[:n],0)
		end

		def handle_hunk
			if @start_mode
				parse_hunk_header
			else
				#'The 'No new line at end of file' is sort of part of the hunk, but
				#is not considerer in the hunkheader
				unless @line == NoNewLine
					#we need to wait for a NoNewLine to be sure we are at the end of the hunk
					return reparse(:unknown) if detect_end_hunk
					linemodes=@line[0...@hunk[:n]-1]
					newline=true
					#the line is on the new file unless there is a '-' somewhere
					if linemodes=~/-/
						newline=false
					else
						@hunk[:lines_seen][0]+=1
					end
					(1...@hunk[:n]).each do |i|
						linemode=linemodes[i-1]
						case linemode
						when '-'
							@hunk[:lines_seen][i]+=1
						when ' '
							@hunk[:lines_seen][i]+=1 if newline
						end
					end
				end
			end
			handle_line
		end

		def get_file_name(file)
			#remove prefix (todo handle the no-prefix option)
			file.gsub(/^[abciow12]\//,'')
		end

		def detect_filename
			if m=@line.match(/^---\s(.*)/)
				@file[:old_name]=get_file_name(m[1])
				return true
			end
			if m=@line.match(/^\+\+\+\s(.*)/)
				@file[:name]=get_file_name(m[1])
				return true
			end
			false
		end

		def detect_perm
			if m=@line.match(/^old mode\s+(.*)/)
				@file[:old_perm]=m[1]
				return true
			end
			if m=@line.match(/^new mode\s+(.*)/)
				@file[:new_perm]=m[1]
				return true
			end
			false
		end

		def detect_index
			if m=@line.match(/^index\s+(.*)\.\.(.*)/)
				@file[:oldhash]=m[1].split(',')
				@file[:hash],perm=m[2].split
				@file[:perm]||=perm
				return true
			end
			false
		end

		def detect_delete
			if m=@line.match(/^deleted file mode\s+(.*)/)
				@file[:old_perm]=m[1]
				@file[:mode]=:delete
				return true
			end
			false
		end

		def detect_newfile
			if m=@line.match(/^new file mode\s+(.*)/)
				@file[:new_perm]=m[1]
				@file[:mode]=:new
				return true
			end
			false
		end

		def detect_rename_copy
			if m=@line.match(/^similarity index\s+(.*)/)
				@file[:similarity]=m[1]
				return true
			end
			if m=@line.match(/^dissimilarity index\s+(.*)/)
				@file[:mode]=:rewrite
				@file[:dissimilarity]=m[1]
				return true
			end
			#if we have a rename with 100% similarity, there won't be any hunks so
			#we need to detect the filenames there
			if m=@line.match(/^(?:rename|copy) from\s+(.*)/)
				@file[:old_name]=m[1]
			end
			if m=@line.match(/^(?:rename|copy) to\s+(.*)/)
				@file[:name]=m[1]
			end
			if m=@line.match(/^rename\s+(.*)/)
				@file[:mode]=:rename
				return true
			end
			if m=@line.match(/^copy\s+(.*)/)
				@file[:mode]=:copy
				return true
			end
			false
		end

		def detect_diff_header
			if @start_mode
				if m=@line.chomp.match(/^diff\s--git\s(.*)\s(.*)/)
					@file[:old_name]=get_file_name(m[1])
					@file[:name]=get_file_name(m[2])
				elsif
					m=@line.match(/^diff\s--(?:cc|combined)\s(.*)/)
					@file[:name]=get_file_name(m[1])
				end
				true
			end
		end

		def handle_diff_header
			if detect_diff_header
			elsif detect_filename
			elsif detect_perm
			elsif detect_index
			elsif detect_delete
			elsif detect_newfile
			elsif detect_rename_copy
			else
				return reparse(:unknown)
			end
			next_mode(:unknown) if detect_end_diff_header
			handle_line
		end

		def detect_new_submodule_header
			if m=@line.chomp.match(/^Submodule\s(.*)\s(.*)/)
				subname=m[1];
				return not(@submodule && @submodule[:name]==subname)
			end
			false
		end

		def handle_submodule_header
			if m=@line.chomp.match(/^Submodule\s(\S*)\s(.*)/)
				subname=m[1]
				if @submodule[:name]
					#we may be dealing with a new submodule
					#require 'pry'; binding.pry
					return reparse(:submodule_header) if subname != @submodule[:name]
				else
					@submodule[:name]=m[1]
				end
				subinfo=m[2]
				if subinfo == "contains untracked content"
					@submodule[:untracked]=true
				elsif subinfo == "contains modified content"
					@submodule[:modified]=true
				else
					(@submodule[:info]||="") << subinfo
					next_mode(:submodule) if subinfo =~ /^.......\.\.\.?........*:$/
				end
				handle_line
			else
				return reparse(:unknown)
			end
		end

		def submodule_line
			@line=~/^  [><] /
		end

		def handle_submodule
			#we have lines indicating new commits
			#they always end by a new line except when followed by another submodule
			return reparse(:unknown) if !submodule_line
			handle_line
		end

		def detect_new_commit
			@line=~/^commit\b/
		end

		def handle_commit
			if m=@line.match(/^(\w+):\s(.*)/)
				@commit[m[1]]=m[2]
				handle_line
			else
				@start_mode ? handle_line : reparse(:unknown)
			end
		end

		def reparse(nmode)
			change_mode(nmode)
			parse_line
		end

		def handle_line
		end


		def parse_line
			case @mode
			when :unknown, :meta
				if detect_new_hunk
					return reparse(:hunk)
				elsif detect_new_diff_header
					return reparse(:diff_header)
				elsif detect_new_submodule_header
					return reparse(:submodule_header)
				elsif detect_new_commit
					return reparse(:commit)
				else
					change_mode(:meta) if @mode==:unknown
					handle_meta
				end
			when :commit
				handle_commit
			when :submodule_header
				handle_submodule_header
			when :submodule
				handle_submodule
			when :diff_header
				handle_diff_header
				#=> mode=unknown if we detect we are not a diff header anymore
			when :hunk
				handle_hunk
				#=> mode=unknown at end of hunk
			end
		end

		def prepare_new_line(line)
			@orig_line=line
			@line=@orig_line.uncolor
			update_mode
		end

		def parse
			Enumerator.new do |y|
				@output=y
				@diff.each do |line|
					prepare_new_line(line)
					parse_line
					yield if block_given?
				end
				change_mode(:unknown) #to trigger the last end_* hook
			end
		end

		def each(&b)
			parse.each(&b)
		end
	end

	class GitDiffDebug < GitDiff
		def initialize(*args,&b)
			super
			@cols=`tput cols`.to_i
		end

		def center(msg)
			msg.center(@cols,'─')
		end

		def handle_line
			super
			output_line "#{@mode}: #{@orig_line}"
			#p @hunk if @mode==:hunk
		end

		%i(commit meta diff_header hunk submodule_header submodule).each do |meth|
			define_method(:"new_#{meth}") do |*a,&b|
				super(*a,&b)
				output_line(center("New #{meth}"))
			end
			define_method(:"end_#{meth}") do |*a,&b|
				super(*a,&b)
				output_line(center("End #{meth}"))
			end
		end
	end

	#stolen from diff-highlight git contrib script
	class GitDiffHighlight < GitDiff
		def new_hunk
			super
			@accumulator=[[],[]]
		end
		def end_hunk
			super
			show_hunk
		end

		def highlight_pair(old,new)
			oldc=SimpleColor.color_entities(old).each_with_index
			newc=SimpleColor.color_entities(new).each_with_index
			seen_pm=false
			#find common prefix
			loop do
				a=oldc.grep {|c| ! SimpleColor.color?(c)}
				b=newc.grep {|c| ! SimpleColor.color?(c)}
				if !seen_pm and a=="-" and b=="+"
					seen_pm=true
				elsif a==b
				else
					last
				end
			#rescue StopIteration
			end
		end

		def show_hunk
			old,new=@accumulator
			if old.length != new.length
				output_lines(old+new)
			else
				newhunk=[]
				(0...old.length).each do |i|
					oldi,newi=highlight_pair(old[i],new[i])
					output_line oldi
					newhunk << newi
				end
				output_lines(newhunk)
			end
		end

		def handle_line
			if @mode == :hunk && @hunk[:n]==2
				linemode=@line[0]
				case linemode
				when "-"
					@accumulator[0] << @orig_line
				when "+"
					@accumulator[1] << @orig_line
				else
					show_hunk
					@accumulator=[[],[]]
					output_line @orig_line
				end
			else
				output_line @orig_line
			end
		end
	end

	class GitFancyDiff < GitDiff

		def initialize(*args,**kw,&b)
			super
			#when run inside a pager I get one more column so the line overflow
			#I don't know why
			cols=`tput cols`.to_i
			cols==0 && cols=80 #if TERM is not defined `tput cols` returns ''
			@cols=cols-1
		end

		def hline
			'─'*@cols
		end
		def hhline
			#'⬛'*@cols
			#"━"*@cols
			"═"*@cols
		end

		def short_perm_mode(m, prefix: '+')
			case m
			when "040000"
				prefix+"d" #directory
			when "100644"
				"" #file
			when "100755"
				prefix+"x" #executable
			when "120000"
				prefix+"l" #symlink
			when "160000"
				prefix+"g" #gitlink
			end
		end
		def perm_mode(m, prefix: ' ')
			case m
			when "040000"
				prefix+"directory"
			when "100644"
				"" #file
			when "100755"
				prefix+"executable"
			when "120000"
				prefix+"symlink"
			when "160000"
				prefix+"gitlink"
			end
		end

		def diff_header_summary
			r=case @file[:mode]
				when :modify
					"modified: #{@file[:name]}"
				when :rewrite
					"rewrote: #{@file[:name]} (dissimilarity: #{@file[:dissimilarity]})"
				when :new
					"added#{perm_mode(@file[:new_perm])}: #{@file[:name]}"
				when :delete
					"deleted#{perm_mode(@file[:old_perm])}: #{@file[:old_name]}"
				when :rename
					"renamed: #{@file[:old_name]} to #{@file[:name]} (similarity: #{@file[:similarity]})"
				when :copy
					"copied: #{@file[:old_name]} to #{@file[:name]} (similarity: #{@file[:similarity]})"
				end
			r<<" [#{short_perm_mode(@file[:old_perm],prefix:'-')}#{short_perm_mode(@file[:new_perm])}]" if @file[:old_perm] && @file[:new_perm]
			r
		end

		def meta_colorize(l)
			if @opts[:color]
				l.color(*@colors[:meta])
			else
				l
			end
		end

		def new_diff_header
			super
			output_line meta_colorize(hline)
		end

		def end_diff_header
			super
			output_line meta_colorize(diff_header_summary)
			output_line meta_colorize(hline)
		end

		def submodule_header_summary
			r="Submodule #{@submodule[:name]}"
			extra=[@submodule[:modified] && "modified", @submodule[:untracked] && "untracked"].compact.join("+")
			r<<" [#{extra}]" unless extra.empty?
			r << " #{@submodule[:info]}" if @submodule[:info]
			r
		end

		def new_submodule_header
			super
			output_line meta_colorize(hline)
		end

		def end_submodule_header
			super
			output_line meta_colorize(submodule_header_summary)
			output_line meta_colorize(hline)
		end

		def nonewline_clean
				@mode==:hunk && @file && (@file[:perm]=="120000" or @file[:old_perm]=="120000" or @file[:new_perm]=="120000") && @line==NoNewLine
		end

		def new_commit
			super
			output_line meta_colorize(hhline)
		end
		def end_commit
			super
			output_line meta_colorize(hhline)
		end

		def clean_hunk_col
			if @opts[:color] && @mode==:hunk && !@start_mode && @hunk[:n]==2
				bcolor,ecolor,line=SimpleColor.current_colors(@orig_line)
				m=line.scrub.match(/^([+-])?(.*)/)
				mode=m[1]
				cline=m[2]
				if mode && cline !~ /[^[:space:]]/ #detect blank line
					output_line SimpleColor.color(bcolor.to_s + (cline.empty? ? " ": cline)+ecolor.to_s,:inverse)
				else
					cline.sub!(/^\s/,'') unless mode #strip one blank character
					output_line bcolor.to_s+cline+ecolor.to_s
				end
				true
			end
		end

		def hunk_header
			if @mode==:hunk && @start_mode
				if @hunk[:lines][0][1] && @hunk[:lines][0][1] != 0
					header="#{@file[:name]}:#{@hunk[:lines][0][1]}"
					output_line @orig_line.sub(/(@@+\s)(.*)(\s@@+)/,"\\1#{header}\\3")
				end
				true
			end
		end

		def binary_file_differ
			@file and (@file[:mode]==:new && @line =~ %r{^Binary files /dev/null and ./#{@file[:name]} differ$} or
							 	 @file[:mode]==:delete && @line =~ %r{^Binary files ./#{@file[:old_name]} and /dev/null differ$})
		end

		def handle_line
			super
			#:diff_header and submodule_header are handled at end_*
			case @mode
			when :meta
				if binary_file_differ
				else output_line @orig_line
				end
			when :hunk
				if hunk_header
				elsif nonewline_clean
				elsif clean_hunk_col
				else output_line @orig_line
				end
			when :submodule,:commit
				output_line @orig_line
			end
		end
	end
end

if __FILE__ == $0
	require 'optparse'

	@opts={pager: true, diff_highlight: true, color: true, debug: false}
	optparse = OptionParser.new do |opt|
		opt.banner = "fancy git diff"
		opt.on("--[no-]pager", "launch the pager [true]") do |v|
			@opts[:pager]=v
		end
		opt.on("--[no-]highlight", "run the diff through diff-highlight [true]") do |v|
			@opts[:diff_highlight]=v
		end
		opt.on("--[no-]color", "color output [true]") do |v|
			@opts[:color]=v
		end
		opt.on("--raw", "Only parse diff headers") do |v|
			@opts[:color]=false
			@opts[:pager]=false
			@opts[:diff_highlight]=false
		end
		opt.on("--[no-]debug", "Debug mode") do |v|
			@opts[:debug]=v
		end
	end
	optparse.parse!
	@opts[:pager]=false unless Module.const_defined?('ShellHelpers')
	@opts[:pager] && ShellHelpers.run_pager #("--pattern '^(Date|added|deleted|modified): '")

	diff_highlight=ENV['DIFF_HIGHLIGHT']||"#{File.dirname(__FILE__)}/contrib/diff-highlight/diff-highlight"

	args=ARGF
	if @opts[:debug]
		GitHelpers::GitDiffDebug.new(args,**@opts).output
	elsif @opts[:diff_highlight]
		IO.popen(diff_highlight,'r+') do |f|
			Thread.new do
				args.each_line do |l|
					f.write(l)
				end
				f.close_write
			end
			GitHelpers::GitFancyDiff.new(f,**@opts).output
		end
	else
		#diff=GitDiffHighlight.new(args,**@opts).parse
		GitHelpers::GitFancyDiff.new(args,**@opts).output
	end
end