#!/bin/bash

# ==============================================================================
#          *** BackFLiP (a.k.a  BACKporting Fun with LInaro People) ***
#
# Usage: backflip rev_number
# ==============================================================================

# ==============================================================================
# Configuration
# ==============================================================================
VERSION=4.9
REF_BRANCH=linaro-${VERSION}-branch

DATE=`date +%Y-%m-%d`
NAME=`git config user.name`
FNAME=`echo ${NAME} | cut -d ' ' -f 1`
EMAIL=`git config user.email`
EDITOR="${EDITOR:-vim}"
STACKED=false
CMPTOOL="meld"

# Arguments
while getopts "b:r:v:" options
do
  case $options in
    r ) REF_BRANCH=$OPTARG
    ;;
    b ) DEV_BRANCH=$OPTARG
	STACKED=true
    ;;
    v ) VERSION=$OPTARG
	REF_BRANCH=linaro-${VERSION}-branch
    ;;
  esac
done
shift $(($OPTIND - 1))

REV=$1
if [ -z ${DEV_BRANCH+x} ]; then
  DEV_BRANCH=${REF_BRANCH}
fi

# Style 
NC='\e[0m'
red='\e[0;31m'
blue='\e[1;34m'
green='\e[0;32m'
bold='\e[1m'
lines=`perl -E 'say "-" x 80'`

# ==============================================================================
# Functions
# ==============================================================================
print_step() {
  echo -e "${blue}${lines}\n${red}** ${1}\n${blue}${lines}${NC}\n"
}

print_info() {
  echo -e "${blue}** ${NC}${1}"
}

die() {
  echo -e "${red}${bold}ERROR: ${NC}${bold}${1}${NC}"
  exit 1
}

open_shell() {
  PROMPT_COMMAND="echo -n -e '${bold}[${red}BackFLiP${NC}${bold}]${NC} '" bash
}

# arg1 : a sentence
# arg2 : a variable
# print arg1 and gather user input in arg2
ask() {
  echo -n -e "${blue}** ${NC}${1} ${NC}"
  eval "read ${2}"
}

# arg1 : svn rev number
# arg2 : ChangeLog file
# Create ChangeLog entry for arg1 in arg2.arg1.frag
forge_entry() {
  echo -e $DATE"  "$NAME"  <"$EMAIL">\n\n\tBackport from trunk r"$1"." >> $2.$1.frag
  git show --format=oneline ${SHA1} -- $2 \
    | grep ^+ \
    | sed -e '1d' -e 's:^+::' \
    | awk '$1 ~ /^2.*$/ {print "\t"$0}  $1 !~ /^2.*$/ {print $0}' >> $2.$1.frag
  print_info "${bold}Forged ChangeLog entry:${NC}"
  cat $2.$1.frag
  ask "${bold}Edit ChangeLog entry [N/y] ?" user_edit
  if [ "$user_edit" == "y" ]; then
    "$EDITOR" $2.$1.frag
  fi
}

# arg1 : backported revision sha1
compare() {
  git show $1 > $REV.orig
  git diff --cached > $REV.linaro
  print_info "Generated diff files: ${bold}$REV.orig $REV.linaro${NC}"
  "$CMPTOOL" $REV.orig $REV.linaro
  ask "${bold}Do you need a Shell [N/y] ?" user_shell
  if [ "$user_shell" == "y" ]; then
     open_shell
  fi
  rm $REV.orig $REV.linaro
}

# ==============================================================================
# Checking Configuration
# ==============================================================================
if ! git remote -v 2>&1 | grep "ssh.*git.*\.linaro\.org" > /dev/null ; then
  die "You're not in the right directory !"
fi
if [ ! -e .gitreview ]; then
  print_info "Gerrit configuration (.gitreview) is missing, creating it."
  cat <<- EOF > .gitreview
[gerrit]
host=review.linaro.org
port=29418
project=toolchain/gcc
EOF
fi
if ! which $CMPTOOL > /dev/null ; then
  print_info "Default comparison tool is missing"
  ask "Enter tool name: " CMPTOOL
fi

echo -e "${blue}${lines}"
print_info "Backport will de done on top of branch: ${bold}$DEV_BRANCH${NC}"
print_info "Reference branch used for review is: ${bold}$REF_BRANCH${NC}"
print_info "To change GCC version in a Linaro branch use ${bold}-v${NC}"
print_info "example: ${bold}backflip -v 4.8${NC}"
print_info "To change reference branch use ${bold}-r${NC}"
print_info "example: ${bold}backflip -r master${NC}"

# ==============================================================================
print_step "Finding SHA1"
# ==============================================================================
SHA1=`git log --format=format:"%H" --grep=trunk@${REV} master`
print_info "${NC}SVN rev ${bold}${1}${NC} SHA1: ${bold}${SHA1}${NC}"
ask "${bold}View the commit [N/y] ?" user_view
if [ "$user_view" == "y" ]; then
   git show $SHA1
fi

# ==============================================================================
print_step "Cherry-picking Revision"
# ==============================================================================
git checkout $DEV_BRANCH
git cherry-pick -n $SHA1

# ==============================================================================
print_step "Handling ChangeLogs Conflicts"
# ==============================================================================
CHLOGS=`git diff-tree --no-commit-id --name-only -r ${SHA1} | grep ChangeLog`
for i in $CHLOGS; do
  print_info "${green}$i"
  # Revert ChangeLog corruption
  git reset -q HEAD $i
  git checkout $i
  # Create ChangeLog entry
  forge_entry $1 $i
done

# ==============================================================================
print_step "Status Checking"
# ==============================================================================
git status
ask "${bold}Open a Shell [N/y] ?" user_shell
if [ "$user_shell" == "y" ]; then
   open_shell
fi

# ==============================================================================
print_step "Verification"
# ==============================================================================
compare $SHA1

# ==============================================================================
print_step "Branch/Commit/Push/Review"
# ==============================================================================
if $STACKED; then
  bname=${DEV_BRANCH}-${1}
else
  bname=${FNAME}-${VERSION}-backport-${1}
fi
ask "${bold}Create backport branch [Y/n] ?" user_bc
if [ "$user_bc" != "n" ]; then
  ask "${bold}Change name (${blue}${bname}${NC}${bold}) [N/y] ?" user_bname
  if [ "$user_bname" == "y" ]; then
    ask "${bold}Enter name :" bname
  fi
  git checkout -b ${bname} ${DEV_BRANCH}

  ask "${bold}Commit backport [Y/n] ?" user_commit
  if [ "$user_commit" != "n" ]; then
    if $STACKED; then
      git commit --amend
    else
      git commit
    fi

    echo
    print_info "If you want to stack another backport on top of this one"
    print_info "you can stop here, and invoke backflip with command:"
    print_info "${bold}backflip -b ${bname} REV_NUMBER${NC}"
    print_info "The next steps are only needed for review and validation.\n"

    ask "${bold}Create patch [Y/n] ?" user_patch
    if [ "$user_patch" != "n" ]; then
      git format-patch -o ../ --suffix=.${bname}.patch -1
    fi

    ask "${bold}Request review (amend commit) [Y/n] ?" user_review
    if [ "$user_review" != "n" ]; then
      git review $REF_BRANCH
      git checkout $DEV_BRANCH
    fi
  fi
fi

# ==============================================================================
ask "${bold}Abort and Cleanup [N/y] ?" user_abort
# ==============================================================================
if [ "$user_abort" == "y" ]; then
  git reset --hard
  git checkout ${DEV_BRANCH}
  if [ "$user_bc" != "n" ]; then
    git branch -D ${bname}
    if [ "$user_push" != "n" ]; then
      git push origin :${bname}
    fi
  fi
  exit 0
fi