#!/bin/sh
# From Gerrit Code Review 2.5-1-g3dd020f
#
# Part of Gerrit Code Review (http://code.google.com/p/gerrit/)
#
# Copyright (C) 2009 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

CHANGE_ID_AFTER="Bug|Issue"
MSG="$1"

# Check for, and add if missing, a unique Change-Id
#
add_ChangeId() {
    clean_message=`sed -e '
        /^diff --git a\/.*/{
            s///
            q
        }
        /^Signed-off-by:/d
        /^#/d
    ' "$MSG" | git stripspace`
    if test -z "$clean_message"
    then
        return
    fi

    # Does Change-Id: already exist? if so, exit (no change).
    if grep -i '^Change-Id:' "$MSG" >/dev/null
    then
        return
    fi

    id=`_gen_ChangeId`
    T="$MSG.tmp.$$"
    AWK=awk
    if [ -x /usr/xpg4/bin/awk ]; then
        # Solaris AWK is just too broken
        AWK=/usr/xpg4/bin/awk
    fi

    # How this works:
    # - parse the commit message as (textLine+ blankLine*)*
    # - assume textLine+ to be a footer until proven otherwise
    # - exception: the first block is not footer (as it is the title)
    # - read textLine+ into a variable
    # - then count blankLines
    # - once the next textLine appears, print textLine+ blankLine* as these
    #   aren't footer
    # - in END, the last textLine+ block is available for footer parsing
    $AWK '
    BEGIN {
        # while we start with the assumption that textLine+
        # is a footer, the first block is not.
        isFooter = 0
        footerComment = 0
        blankLines = 0
    }

    # Skip lines starting with "#" without any spaces before it.
    /^#/ { next }

    # Skip the line starting with the diff command and everything after it,
    # up to the end of the file, assuming it is only patch data.
    # If more than one line before the diff was empty, strip all but one.
    /^diff --git a/ {
        blankLines = 0
        while (getline) { }
        next
    }

    # Count blank lines outside footer comments
    /^$/ && (footerComment == 0) {
        blankLines++
        next
    }

    # Catch footer comment
    /^\[[a-zA-Z0-9-]+:/ && (isFooter == 1) {
        footerComment = 1
    }

    /]$/ && (footerComment == 1) {
        footerComment = 2
    }

    # We have a non-blank line after blank lines. Handle this.
    (blankLines > 0) {
        print lines
        for (i = 0; i < blankLines; i++) {
            print ""
        }

        lines = ""
        blankLines = 0
        isFooter = 1
        footerComment = 0
    }

    # Detect that the current block is not the footer
    (footerComment == 0) && (!/^\[?[a-zA-Z0-9-]+:/ || /^[a-zA-Z0-9-]+:\/\//) {
        isFooter = 0
    }

    {
        # We need this information about the current last comment line
        if (footerComment == 2) {
            footerComment = 0
        }
        if (lines != "") {
            lines = lines "\n";
        }
        lines = lines $0
    }

    # Footer handling:
    # If the last block is considered a footer, splice in the Change-Id at the
    # right place.
    # Look for the right place to inject Change-Id by considering
    # CHANGE_ID_AFTER. Keys listed in it (case insensitive) come first,
    # then Change-Id, then everything else (eg. Signed-off-by:).
    #
    # Otherwise just print the last block, a new line and the Change-Id as a
    # block of its own.
    END {
        unprinted = 1
        if (isFooter == 0) {
            print lines "\n"
            lines = ""
        }
        changeIdAfter = "^(" tolower("'"$CHANGE_ID_AFTER"'") "):"
        numlines = split(lines, footer, "\n")
        for (line = 1; line <= numlines; line++) {
            if (unprinted && match(tolower(footer[line]), changeIdAfter) != 1) {
                unprinted = 0
                print "Change-Id: I'"$id"'"
            }
            print footer[line]
        }
        if (unprinted) {
            print "Change-Id: I'"$id"'"
        }
    }' "$MSG" > $T && mv $T "$MSG" || rm -f $T
}
_gen_ChangeIdInput() {
    echo "tree `git write-tree`"
    if parent=`git rev-parse "HEAD^0" 2>/dev/null`
    then
        echo "parent $parent"
    fi
    echo "author `git var GIT_AUTHOR_IDENT`"
    echo "committer `git var GIT_COMMITTER_IDENT`"
    echo
    printf '%s' "$clean_message"
}
_gen_ChangeId() {
    _gen_ChangeIdInput |
    git hash-object -t commit --stdin
}


add_ChangeId