#!/bin/sh
# Tcl ignores the next line -*- tcl -*- \
exec wish "$0" -- "${1+$@}"

# Copyright (C) 2005 Paul Mackerras.  All rights reserved.
# This program is free software; it may be used, copied, modified
# and distributed under the terms of the GNU General Public Licence,
# either version 2, or (at your option) any later version.

set datemode 0
set boldnames 0
set revtreeargs {}

foreach arg $argv {
    switch -regexp -- $arg {
        "^$" { }
        "^-d" { set datemode 1 }
        "^-b" { set boldnames 1 }
        "^-.*" {
            puts stderr "unrecognized option $arg"
            exit 1
        }
        default {
            lappend revtreeargs $arg
        }
    }
}

proc getcommits {rargs} {
    global commits parents cdate nparents children nchildren
    if {$rargs == {}} {
        set rargs HEAD
    }
    set commits {}
    foreach c [split [eval exec git-rev-tree $rargs] "\n"] {
        set i 0
        set cid {}
        foreach f $c {
            if {$i == 0} {
                set d $f
            } else {
                set id [lindex [split $f :] 0]
                if {![info exists nchildren($id)]} {
                    set children($id) {}
                    set nchildren($id) 0
                }
                if {$i == 1} {
                    set cid $id
                    lappend commits $id
                    set parents($id) {}
                    set cdate($id) $d
                    set nparents($id) 0
                } else {
                    lappend parents($cid) $id
                    incr nparents($cid)
                    incr nchildren($id)
                    lappend children($id) $cid
                }
            }
            incr i
        }
    }
}

proc readcommit {id} {
    global commitinfo
    set inhdr 1
    set comment {}
    set headline {}
    set auname {}
    set audate {}
    set comname {}
    set comdate {}
    foreach line [split [exec git-cat-file commit $id] "\n"] {
        if {$inhdr} {
            if {$line == {}} {
                set inhdr 0
            } else {
                set tag [lindex $line 0]
                if {$tag == "author"} {
                    set x [expr {[llength $line] - 2}]
                    set audate [lindex $line $x]
                    set auname [lrange $line 1 [expr {$x - 1}]]
                } elseif {$tag == "committer"} {
                    set x [expr {[llength $line] - 2}]
                    set comdate [lindex $line $x]
                    set comname [lrange $line 1 [expr {$x - 1}]]
                }
            }
        } else {
            if {$comment == {}} {
                set headline $line
            } else {
                append comment "\n"
            }
            append comment $line
        }
    }
    if {$audate != {}} {
        set audate [clock format $audate -format "%Y-%m-%d %H:%M:%S"]
    }
    if {$comdate != {}} {
        set comdate [clock format $comdate -format "%Y-%m-%d %H:%M:%S"]
    }
    set commitinfo($id) [list $comment $auname $audate $comname $comdate]
    return [list $headline $auname $audate]
}

proc makewindow {} {
    global canv linespc charspc ctext
    frame .clist
    set canv .clist.canv
    canvas $canv -height [expr 30 * $linespc + 4] -width [expr 90 * $charspc] \
        -bg white -relief sunk -bd 1 \
        -yscrollincr $linespc -yscrollcommand ".clist.csb set"
    scrollbar .clist.csb -command "$canv yview" -highlightthickness 0
    pack .clist.csb -side right -fill y
    pack $canv -side bottom -fill both -expand 1
    pack .clist -side top -fill both -expand 1
    set ctext .ctext
    text $ctext -bg white
    pack $ctext -side top -fill x -expand 1

    bind $canv <1> {selcanvline %x %y}
    bind $canv <B1-Motion> {selcanvline %x %y}
    bind $canv <ButtonRelease-4> "$canv yview scroll -5 u"
    bind $canv <ButtonRelease-5> "$canv yview scroll 5 u"
    bind $canv <2> "$canv scan mark 0 %y"
    bind $canv <B2-Motion> "$canv scan dragto 0 %y"
    bind . <Key-Prior> "$canv yview scroll -1 p"
    bind . <Key-Next> "$canv yview scroll 1 p"
    bind . <Key-Delete> "$canv yview scroll -1 p"
    bind . <Key-BackSpace> "$canv yview scroll -1 p"
    bind . <Key-space> "$canv yview scroll 1 p"
    bind . <Key-Up> "$canv yview scroll -1 u"
    bind . <Key-Down> "$canv yview scroll 1 u"
    bind . Q "set stopped 1; destroy ."
}

proc truncatetofit {str width font} {
    if {[font measure $font $str] <= $width} {
        return $str
    }
    set best 0
    set bad [string length $str]
    set tmp $str
    while {$best < $bad - 1} {
        set try [expr {int(($best + $bad) / 2)}]
        set tmp "[string range $str 0 [expr $try-1]]..."
        if {[font measure $font $tmp] <= $width} {
            set best $try
        } else {
            set bad $try
        }
    }
    return $tmp
}

proc drawgraph {start} {
    global parents children nparents nchildren commits
    global canv mainfont namefont canvx0 canvy0 linespc namex datex
    global datemode cdate
    global lineid linehtag linentag linedtag

    set colors {green red blue magenta darkgrey brown orange}
    set ncolors [llength $colors]
    set nextcolor 0
    set colormap($start) [lindex $colors 0]
    foreach id $commits {
        set ncleft($id) $nchildren($id)
    }
    set todo [list $start]
    set level 0
    set canvy $canvy0
    set linestarty(0) $canvy
    set nullentry -1
    set lineno -1
    while 1 {
        incr lineno
        set nlines [llength $todo]
        set id [lindex $todo $level]
        set lineid($lineno) $id
        foreach p $parents($id) {
            incr ncleft($p) -1
        }
        set cinfo [readcommit $id]
        set x [expr $canvx0 + $level * $linespc]
        set y2 [expr $canvy + $linespc]
        if {$linestarty($level) < $canvy} {
            set t [$canv create line $x $linestarty($level) $x $canvy \
                       -width 2 -fill $colormap($id)]
            $canv lower $t
            set linestarty($level) $canvy
        }
        set t [$canv create oval [expr $x - 4] [expr $canvy - 4] \
                   [expr $x + 3] [expr $canvy + 3] \
                   -fill blue -outline black -width 1]
        $canv raise $t
        set xt [expr $canvx0 + $nlines * $linespc]
        set headline [lindex $cinfo 0]
        set name [lindex $cinfo 1]
        set date [lindex $cinfo 2]
        set headline [truncatetofit $headline [expr $namex-$xt-$linespc] \
                         $mainfont]
        set linehtag($lineno) [$canv create text $xt $canvy -anchor w \
                                   -text $headline -font $mainfont ]
        set name [truncatetofit $name [expr $datex-$namex-$linespc] $namefont]
        set linentag($lineno) [$canv create text $namex $canvy -anchor w \
                                   -text $name -font $namefont]
        set linedtag($lineno) [$canv create text $datex $canvy -anchor w \
                                 -text $date -font $mainfont]
        if {!$datemode && $nparents($id) == 1} {
            set p [lindex $parents($id) 0]
            if {$ncleft($p) == 0 && [lsearch -exact $todo $p] < 0} {
                set todo [lreplace $todo $level $level $p]
                set colormap($p) $colormap($id)
                set canvy $y2
                $canv conf -scrollregion [list 0 0 0 $canvy]
                update
                continue
            }
        }

        set oldtodo $todo
        set oldlevel $level
        set lines {}
        for {set i 0} {$i < $nlines} {incr i} {
            if {[lindex $todo $i] == {}} continue
            set oldstarty($i) $linestarty($i)
            if {$i != $level} {
                lappend lines [list $i [lindex $todo $i]]
            }
        }
        unset linestarty
        if {$nullentry >= 0} {
            set todo [lreplace $todo $nullentry $nullentry]
            if {$nullentry < $level} {
                incr level -1
            }
        }

        set badcolors [list $colormap($id)]
        foreach p $parents($id) {
            if {[info exists colormap($p)]} {
                lappend badcolors $colormap($p)
            }
        }
        set todo [lreplace $todo $level $level]
        if {$nullentry > $level} {
            incr nullentry -1
        }
        set i $level
        foreach p $parents($id) {
            set k [lsearch -exact $todo $p]
            if {$k < 0} {
                set todo [linsert $todo $i $p]
                if {$nullentry >= $i} {
                    incr nullentry
                }
                if {$nparents($id) == 1 && $nparents($p) == 1
                    && $nchildren($p) == 1} {
                    set colormap($p) $colormap($id)
                } else {
                    for {set j 0} {$j <= $ncolors} {incr j} {
                        if {[incr nextcolor] >= $ncolors} {
                            set nextcolor 0
                        }
                        set c [lindex $colors $nextcolor]
                        # make sure the incoming and outgoing colors differ
                        if {[lsearch -exact $badcolors $c] < 0} break
                    }
                    set colormap($p) $c
                    lappend badcolors $c
                }
            }
            lappend lines [list $oldlevel $p]
        }

        # choose which one to do next time around
        set todol [llength $todo]
        set level -1
        set latest {}
        for {set k $todol} {[incr k -1] >= 0} {} {
            set p [lindex $todo $k]
            if {$p == {}} continue
            if {$ncleft($p) == 0} {
                if {$datemode} {
                    if {$latest == {} || $cdate($p) > $latest} {
                        set level $k
                        set latest $cdate($p)
                    }
                } else {
                    set level $k
                    break
                }
            }
        }
        if {$level < 0} {
            if {$todo != {}} {
                puts "ERROR: none of the pending commits can be done yet:"
                foreach p $todo {
                    puts "  $p"
                }
            }
            break
        }

        # If we are reducing, put in a null entry
        if {$todol < $nlines} {
            if {$nullentry >= 0} {
                set i $nullentry
                while {$i < $todol
                       && [lindex $oldtodo $i] == [lindex $todo $i]} {
                    incr i
                }
            } else {
                set i $oldlevel
                if {$level >= $i} {
                    incr i
                }
            }
            if {$i >= $todol} {
                set nullentry -1
            } else {
                set nullentry $i
                set todo [linsert $todo $nullentry {}]
                if {$level >= $i} {
                    incr level
                }
            }
        } else {
            set nullentry -1
        }

        foreach l $lines {
            set i [lindex $l 0]
            set dst [lindex $l 1]
            set j [lsearch -exact $todo $dst]
            if {$i == $j} {
                set linestarty($i) $oldstarty($i)
                continue
            }
            set xi [expr {$canvx0 + $i * $linespc}]
            set xj [expr {$canvx0 + $j * $linespc}]
            set coords {}
            if {$oldstarty($i) < $canvy} {
                lappend coords $xi $oldstarty($i)
            }
            lappend coords $xi $canvy
            if {$j < $i - 1} {
                lappend coords [expr $xj + $linespc] $canvy
            } elseif {$j > $i + 1} {
                lappend coords [expr $xj - $linespc] $canvy
            }
            lappend coords $xj $y2
            set t [$canv create line $coords -width 2 -fill $colormap($dst)]
            $canv lower $t
            if {![info exists linestarty($j)]} {
                set linestarty($j) $y2
            }
        }
        set canvy $y2
        $canv conf -scrollregion [list 0 0 0 $canvy]
        update
    }
}

proc selcanvline {x y} {
    global canv canvy0 ctext linespc selectedline
    global lineid linehtag linentag linedtag commitinfo
    set ymax [lindex [$canv cget -scrollregion] 3]
    set yfrac [lindex [$canv yview] 0]
    set y [expr {$y + $yfrac * $ymax}]
    set l [expr {int(($y - $canvy0) / $linespc + 0.5)}]
    if {$l < 0} {
        set l 0
    }
    if {[info exists selectedline] && $selectedline == $l} return
    if {![info exists lineid($l)] || ![info exists linehtag($l)]} return
    $canv select clear
    $canv select from $linehtag($l) 0
    $canv select to $linehtag($l) end
    set id $lineid($l)
    $ctext delete 0.0 end
    set info $commitinfo($id)
    $ctext insert end "Author: [lindex $info 1]  \t[lindex $info 2]\n"
    $ctext insert end "Committer: [lindex $info 3]  \t[lindex $info 4]\n"
    $ctext insert end "\n"
    $ctext insert end [lindex $info 0]
}

getcommits $revtreeargs

set mainfont {Helvetica 9}
set namefont $mainfont
if {$boldnames} {
    lappend namefont bold
}
set linespc [font metrics $mainfont -linespace]
set charspc [font measure $mainfont "m"]

set canvy0 [expr 3 + 0.5 * $linespc]
set canvx0 [expr 3 + 0.5 * $linespc]
set namex [expr 45 * $charspc]
set datex [expr 75 * $charspc]

makewindow

set start {}
foreach id $commits {
    if {$nchildren($id) == 0} {
        set start $id
        break
    }
}
if {$start != {}} {
    drawgraph $start
}