# git-gui diff viewer
# Copyright (C) 2006, 2007 Shawn Pearce

proc clear_diff {} {
	global ui_diff current_diff_path current_diff_header
	global ui_index ui_workdir

	$ui_diff conf -state normal
	$ui_diff delete 0.0 end
	$ui_diff conf -state disabled

	set current_diff_path {}
	set current_diff_header {}

	$ui_index tag remove in_diff 0.0 end
	$ui_workdir tag remove in_diff 0.0 end
}

proc reshow_diff {} {
	global file_states file_lists
	global current_diff_path current_diff_side
	global ui_diff

	set p $current_diff_path
	if {$p eq {}} {
		# No diff is being shown.
	} elseif {$current_diff_side eq {}
		|| [catch {set s $file_states($p)}]
		|| [lsearch -sorted -exact $file_lists($current_diff_side) $p] == -1} {
		clear_diff
	} else {
		set save_pos [lindex [$ui_diff yview] 0]
		show_diff $p $current_diff_side {} $save_pos
	}
}

proc handle_empty_diff {} {
	global current_diff_path file_states file_lists

	set path $current_diff_path
	set s $file_states($path)
	if {[lindex $s 0] ne {_M}} return

	info_popup [mc "No differences detected.

%s has no changes.

The modification date of this file was updated by another application, but the content within the file was not changed.

A rescan will be automatically started to find other files which may have the same state." [short_path $path]]

	clear_diff
	display_file $path __
	rescan ui_ready 0
}

proc show_diff {path w {lno {}} {scroll_pos {}}} {
	global file_states file_lists
	global is_3way_diff diff_active repo_config
	global ui_diff ui_index ui_workdir
	global current_diff_path current_diff_side current_diff_header

	if {$diff_active || ![lock_index read]} return

	clear_diff
	if {$lno == {}} {
		set lno [lsearch -sorted -exact $file_lists($w) $path]
		if {$lno >= 0} {
			incr lno
		}
	}
	if {$lno >= 1} {
		$w tag add in_diff $lno.0 [expr {$lno + 1}].0
	}

	set s $file_states($path)
	set m [lindex $s 0]
	set is_3way_diff 0
	set diff_active 1
	set current_diff_path $path
	set current_diff_side $w
	set current_diff_header {}
	ui_status [mc "Loading diff of %s..." [escape_path $path]]

	# - Git won't give us the diff, there's nothing to compare to!
	#
	if {$m eq {_O}} {
		set max_sz [expr {128 * 1024}]
		set type unknown
		if {[catch {
				set type [file type $path]
				switch -- $type {
				directory {
					set type submodule
					set content {}
					set sz 0
				}
				link {
					set content [file readlink $path]
					set sz [string length $content]
				}
				file {
					set fd [open $path r]
					fconfigure $fd -eofchar {}
					set content [read $fd $max_sz]
					close $fd
					set sz [file size $path]
				}
				default {
					error "'$type' not supported"
				}
				}
			} err ]} {
			set diff_active 0
			unlock_index
			ui_status [mc "Unable to display %s" [escape_path $path]]
			error_popup [strcat [mc "Error loading file:"] "\n\n$err"]
			return
		}
		$ui_diff conf -state normal
		if {$type eq {submodule}} {
			$ui_diff insert end [append \
				"* " \
				[mc "Git Repository (subproject)"] \
				"\n"] d_@
		} elseif {![catch {set type [exec file $path]}]} {
			set n [string length $path]
			if {[string equal -length $n $path $type]} {
				set type [string range $type $n end]
				regsub {^:?\s*} $type {} type
			}
			$ui_diff insert end "* $type\n" d_@
		}
		if {[string first "\0" $content] != -1} {
			$ui_diff insert end \
				[mc "* Binary file (not showing content)."] \
				d_@
		} else {
			if {$sz > $max_sz} {
				$ui_diff insert end \
"* Untracked file is $sz bytes.
* Showing only first $max_sz bytes.
" d_@
			}
			$ui_diff insert end $content
			if {$sz > $max_sz} {
				$ui_diff insert end "
* Untracked file clipped here by [appname].
* To see the entire file, use an external editor.
" d_@
			}
		}
		$ui_diff conf -state disabled
		set diff_active 0
		unlock_index
		if {$scroll_pos ne {}} {
			update
			$ui_diff yview moveto $scroll_pos
		}
		ui_ready
		return
	}

	set cmd [list]
	if {$w eq $ui_index} {
		lappend cmd diff-index
		lappend cmd --cached
	} elseif {$w eq $ui_workdir} {
		if {[string index $m 0] eq {U}} {
			lappend cmd diff
		} else {
			lappend cmd diff-files
		}
	}

	lappend cmd -p
	lappend cmd --no-color
	if {$repo_config(gui.diffcontext) >= 1} {
		lappend cmd "-U$repo_config(gui.diffcontext)"
	}
	if {$w eq $ui_index} {
		lappend cmd [PARENT]
	}
	lappend cmd --
	lappend cmd $path

	if {[catch {set fd [eval git_read --nice $cmd]} err]} {
		set diff_active 0
		unlock_index
		ui_status [mc "Unable to display %s" [escape_path $path]]
		error_popup [strcat [mc "Error loading diff:"] "\n\n$err"]
		return
	}

	set ::current_diff_inheader 1
	fconfigure $fd \
		-blocking 0 \
		-encoding binary \
		-translation binary
	fileevent $fd readable [list read_diff $fd $scroll_pos]
}

proc read_diff {fd scroll_pos} {
	global ui_diff diff_active
	global is_3way_diff current_diff_header

	$ui_diff conf -state normal
	while {[gets $fd line] >= 0} {
		# -- Cleanup uninteresting diff header lines.
		#
		if {$::current_diff_inheader} {
			if {   [string match {diff --git *}      $line]
			    || [string match {diff --cc *}       $line]
			    || [string match {diff --combined *} $line]
			    || [string match {--- *}             $line]
			    || [string match {+++ *}             $line]} {
				append current_diff_header $line "\n"
				continue
			}
		}
		if {[string match {index *} $line]} continue
		if {$line eq {deleted file mode 120000}} {
			set line "deleted symlink"
		}
		set ::current_diff_inheader 0

		# -- Automatically detect if this is a 3 way diff.
		#
		if {[string match {@@@ *} $line]} {set is_3way_diff 1}

		if {[string match {mode *} $line]
			|| [string match {new file *} $line]
			|| [regexp {^(old|new) mode *} $line]
			|| [string match {deleted file *} $line]
			|| [string match {deleted symlink} $line]
			|| [string match {Binary files * and * differ} $line]
			|| $line eq {\ No newline at end of file}
			|| [regexp {^\* Unmerged path } $line]} {
			set tags {}
		} elseif {$is_3way_diff} {
			set op [string range $line 0 1]
			switch -- $op {
			{  } {set tags {}}
			{@@} {set tags d_@}
			{ +} {set tags d_s+}
			{ -} {set tags d_s-}
			{+ } {set tags d_+s}
			{- } {set tags d_-s}
			{--} {set tags d_--}
			{++} {
				if {[regexp {^\+\+([<>]{7} |={7})} $line _g op]} {
					set line [string replace $line 0 1 {  }]
					set tags d$op
				} else {
					set tags d_++
				}
			}
			default {
				puts "error: Unhandled 3 way diff marker: {$op}"
				set tags {}
			}
			}
		} else {
			set op [string index $line 0]
			switch -- $op {
			{ } {set tags {}}
			{@} {set tags d_@}
			{-} {set tags d_-}
			{+} {
				if {[regexp {^\+([<>]{7} |={7})} $line _g op]} {
					set line [string replace $line 0 0 { }]
					set tags d$op
				} else {
					set tags d_+
				}
			}
			default {
				puts "error: Unhandled 2 way diff marker: {$op}"
				set tags {}
			}
			}
		}
		$ui_diff insert end $line $tags
		if {[string index $line end] eq "\r"} {
			$ui_diff tag add d_cr {end - 2c}
		}
		$ui_diff insert end "\n" $tags
	}
	$ui_diff conf -state disabled

	if {[eof $fd]} {
		close $fd
		set diff_active 0
		unlock_index
		if {$scroll_pos ne {}} {
			update
			$ui_diff yview moveto $scroll_pos
		}
		ui_ready

		if {[$ui_diff index end] eq {2.0}} {
			handle_empty_diff
		}
	}
}

proc apply_hunk {x y} {
	global current_diff_path current_diff_header current_diff_side
	global ui_diff ui_index file_states

	if {$current_diff_path eq {} || $current_diff_header eq {}} return
	if {![lock_index apply_hunk]} return

	set apply_cmd {apply --cached --whitespace=nowarn}
	set mi [lindex $file_states($current_diff_path) 0]
	if {$current_diff_side eq $ui_index} {
		set failed_msg [mc "Failed to unstage selected hunk."]
		lappend apply_cmd --reverse
		if {[string index $mi 0] ne {M}} {
			unlock_index
			return
		}
	} else {
		set failed_msg [mc "Failed to stage selected hunk."]
		if {[string index $mi 1] ne {M}} {
			unlock_index
			return
		}
	}

	set s_lno [lindex [split [$ui_diff index @$x,$y] .] 0]
	set s_lno [$ui_diff search -backwards -regexp ^@@ $s_lno.0 0.0]
	if {$s_lno eq {}} {
		unlock_index
		return
	}

	set e_lno [$ui_diff search -forwards -regexp ^@@ "$s_lno + 1 lines" end]
	if {$e_lno eq {}} {
		set e_lno end
	}

	if {[catch {
		set p [eval git_write $apply_cmd]
		fconfigure $p -translation binary -encoding binary
		puts -nonewline $p $current_diff_header
		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
		close $p} err]} {
		error_popup [append $failed_msg "\n\n$err"]
		unlock_index
		return
	}

	$ui_diff conf -state normal
	$ui_diff delete $s_lno $e_lno
	$ui_diff conf -state disabled

	if {[$ui_diff get 1.0 end] eq "\n"} {
		set o _
	} else {
		set o ?
	}

	if {$current_diff_side eq $ui_index} {
		set mi ${o}M
	} elseif {[string index $mi 0] eq {_}} {
		set mi M$o
	} else {
		set mi ?$o
	}
	unlock_index
	display_file $current_diff_path $mi
	if {$o eq {_}} {
		clear_diff
	} else {
		set current_diff_path $current_diff_path
	}
}

proc apply_line {x y} {
	global current_diff_path current_diff_header current_diff_side
	global ui_diff ui_index file_states

	if {$current_diff_path eq {} || $current_diff_header eq {}} return
	if {![lock_index apply_hunk]} return

	set apply_cmd {apply --cached --whitespace=nowarn}
	set mi [lindex $file_states($current_diff_path) 0]
	if {$current_diff_side eq $ui_index} {
		set failed_msg [mc "Failed to unstage selected line."]
		set to_context {+}
		lappend apply_cmd --reverse
		if {[string index $mi 0] ne {M}} {
			unlock_index
			return
		}
	} else {
		set failed_msg [mc "Failed to stage selected line."]
		set to_context {-}
		if {[string index $mi 1] ne {M}} {
			unlock_index
			return
		}
	}

	set the_l [$ui_diff index @$x,$y]

	# operate only on change lines
	set c1 [$ui_diff get "$the_l linestart"]
	if {$c1 ne {+} && $c1 ne {-}} {
		unlock_index
		return
	}
	set sign $c1

	set i_l [$ui_diff search -backwards -regexp ^@@ $the_l 0.0]
	if {$i_l eq {}} {
		unlock_index
		return
	}
	# $i_l is now at the beginning of a line

	# pick start line number from hunk header
	set hh [$ui_diff get $i_l "$i_l + 1 lines"]
	set hh [lindex [split $hh ,] 0]
	set hln [lindex [split $hh -] 1]

	# There is a special situation to take care of. Consider this hunk:
	#
	#    @@ -10,4 +10,4 @@
	#     context before
	#    -old 1
	#    -old 2
	#    +new 1
	#    +new 2
	#     context after
	#
	# We used to keep the context lines in the order they appear in the
	# hunk. But then it is not possible to correctly stage only
	# "-old 1" and "+new 1" - it would result in this staged text:
	#
	#    context before
	#    old 2
	#    new 1
	#    context after
	#
	# (By symmetry it is not possible to *un*stage "old 2" and "new 2".)
	#
	# We resolve the problem by introducing an asymmetry, namely, when
	# a "+" line is *staged*, it is moved in front of the context lines
	# that are generated from the "-" lines that are immediately before
	# the "+" block. That is, we construct this patch:
	#
	#    @@ -10,4 +10,5 @@
	#     context before
	#    +new 1
	#     old 1
	#     old 2
	#     context after
	#
	# But we do *not* treat "-" lines that are *un*staged in a special
	# way.
	#
	# With this asymmetry it is possible to stage the change
	# "old 1" -> "new 1" directly, and to stage the change
	# "old 2" -> "new 2" by first staging the entire hunk and
	# then unstaging the change "old 1" -> "new 1".

	# This is non-empty if and only if we are _staging_ changes;
	# then it accumulates the consecutive "-" lines (after converting
	# them to context lines) in order to be moved after the "+" change
	# line.
	set pre_context {}

	set n 0
	set i_l [$ui_diff index "$i_l + 1 lines"]
	set patch {}
	while {[$ui_diff compare $i_l < "end - 1 chars"] &&
	       [$ui_diff get $i_l "$i_l + 2 chars"] ne {@@}} {
		set next_l [$ui_diff index "$i_l + 1 lines"]
		set c1 [$ui_diff get $i_l]
		if {[$ui_diff compare $i_l <= $the_l] &&
		    [$ui_diff compare $the_l < $next_l]} {
			# the line to stage/unstage
			set ln [$ui_diff get $i_l $next_l]
			if {$c1 eq {-}} {
				set n [expr $n+1]
				set patch "$patch$pre_context$ln"
			} else {
				set patch "$patch$ln$pre_context"
			}
			set pre_context {}
		} elseif {$c1 ne {-} && $c1 ne {+}} {
			# context line
			set ln [$ui_diff get $i_l $next_l]
			set patch "$patch$pre_context$ln"
			set n [expr $n+1]
			set pre_context {}
		} elseif {$c1 eq $to_context} {
			# turn change line into context line
			set ln [$ui_diff get "$i_l + 1 chars" $next_l]
			if {$c1 eq {-}} {
				set pre_context "$pre_context $ln"
			} else {
				set patch "$patch $ln"
			}
			set n [expr $n+1]
		}
		set i_l $next_l
	}
	set patch "@@ -$hln,$n +$hln,[eval expr $n $sign 1] @@\n$patch"

	if {[catch {
		set p [eval git_write $apply_cmd]
		fconfigure $p -translation binary -encoding binary
		puts -nonewline $p $current_diff_header
		puts -nonewline $p $patch
		close $p} err]} {
		error_popup [append $failed_msg "\n\n$err"]
	}

	unlock_index
}