#! /bin/sh

PATCH=`which patch 2>/dev/null`
FGREP1="^--- "
FGREP2="^+++ "
PREDIR="`pwd`"
if [ x"`echo "$1" | grep "^/"`" = x ]
then
    WHOLEPATCH="`pwd`/$1"
else
    WHOLEPATCH="$1"
fi

if [ ! -f $WHOLEPATCH ]
then
    echo "Patch \"$1\" doesn't exist."
    exit
fi

if [ x"$PATCH" = x ]
then
    echo "You need to install \"patch\" prior to patching anything."
    exit
fi

if [ x"$1" = x ]
then
    echo "Usage: \"$0 foo.patch\""
    exit
fi

if [ x"`grep "$FGREP1" "$WHOLEPATCH" | awk '{print $2}'`" = x ]
then
    echo "No valid patch file, you need to "
fi

fcount1=`grep "$FGREP1" "$WHOLEPATCH" | awk '{print $2}' | wc -l`
fcount2=`grep "$FGREP2" "$WHOLEPATCH" | awk '{print $2}' | wc -l`

if [ $fcount1 -ne $fcount2 ]
then
    echo "Different number of Files: add($fcount2) vs. sub($fcount1). Broken file?"
    exit
fi

echo "Trying to find correct path and arguments..."

cdr=1

hits=0
maxhits=0
lastfiles=$fcount1
value=0
godown=0
actdown=0
maxcutglobaldirs=`pwd | sed 's/[^\/]//g' | wc -c`
j=0
down=0

while [ $j -lt $maxcutglobaldirs ]
do
    fcurnum=`grep "$FGREP1" "$WHOLEPATCH" | awk '{print $2}' | cut -d/ -f$cdr- | grep -v "^$" | wc -l`
    if [ $fcurnum -lt $fcount1 ]
    then
        #too many dirs cut, lost some files
        down=1
    fi

    hits=0

    i=1
    while [ $i -lt $fcurnum ]
    do
        filename1=`grep "$FGREP1" "$WHOLEPATCH" | awk '{print $2}' | cut -d/ -f$cdr- | grep -v "^$" | head -n $i | tail -n 1`
        filename2=`grep "$FGREP2" "$WHOLEPATCH" | awk '{print $2}' | cut -d/ -f$cdr- | grep -v "^$" | head -n $i | tail -n 1`

        if [ -f $PREDIR/$filename1 -o -f $PREDIR/$filename2 ]
        then
            hits=$(($hits+1))
        fi

        i=$(($i+1))
    done

    if [ $hits -gt $maxhits ]
    then
        maxhits=$hits
        value=$(($cdr-1))
        actdown=$godown
    fi

    cdr=$(($cdr+1))

    if [ $down -eq 1 ]
    then
        down=0
        if [ $maxhits -eq $fcount1 ]
        then
            break
        fi
        godown=$(($godown+1))
        PREDIR=`echo $PREDIR | cut -d/ -f1-$(($maxcutglobaldirs-$godown))`
        j=$(($j+1))
        cdr=0
    fi
done

change="cd ./"

i=0
while [ $i -lt $actdown ]
do
    change="$change../"
    i=$(($i+1))
done

$change

if [ x"`$PATCH -f --dry-run -Np$value -i "$WHOLEPATCH" | grep "ignored\|ERROR"`" != x ]
then
    echo "Found problems with applying "$WHOLEPATCH" from this location."
    exit
fi

if [ $maxhits -eq 0 ]
then
    echo "Found no files at all."
    exit
fi


if [ $maxhits -lt $fcount1 ]
then
    #echo "I didn't found all files, which should be patched."
    #echo "Just got $maxhits hits out of $fcount1 proposed"
    if [ $actdown -gt 0 ]
    then
        echo "You may run:"
        echo "\"($change; patch --dry-run -Np$value -i "$WHOLEPATCH")\""
    else
        echo "You may run:"
        echo "\"patch --dry-run -Np$value -i $1\""
    fi
    echo "and in case you got no errors, just omit \"--dry-run\"."
else
    if [ $actdown -gt 0 ]
    then
        echo "You need to run \"($change; patch -Np$value -i "$WHOLEPATCH")\""
    else
        echo "You need to run \"patch -Np$value -i $1\""
    fi
fi