#!/bin/sh
#
# Original code copyright (c) 2007 Andy Parkins
# Atompub modifications copyright (c) 2007 Travis Vachon
# An example hook script to mail out commit update information.  This hook posts to an atompub 
# collection listing new revisions to the repository introduced by the change being reported.  The
# rule is that (for branch updates) each commit will appear on one entry and one entry
# only.
#
# To install this hook:
#
#  chmod a+x post-receive-atom
#  cd /path/to/your/repository.git
#  ln -sf /path/to/this/script/post-receive-atom hooks/post-receive
#
# This hook script assumes it is enabled on the central repository of a project, with
# all users pushing only to it and not between each other.  It will still work if you
# don't operate in that style, but it would become possible for posts to be created
# someone other than the person doing the push.
#
# Config
# ------
# hooks.atomcollection
#   This is the edit link of the atompub collection to post to.
# hooks.username
#   This is the username to send as credentials when posting to the atompub collection.
# hooks.password
#   This is the password to send as credentials when posting to the atompub collection.
#
# ---------------------------- Functions

#
# Top level entry generation function.  This decides what type of update
# this is and calls the appropriate body-generation routine after outputting
# the common header
#
# Note this function doesn't actually generate any entry output, that is taken
# care of by the functions it calls:
#  - generate_content_header
#  - generate_create_XXXX_content
#  - generate_create_XXXX_summary
#  - generate_update_XXXX_content
#  - generate_update_XXXX_summary
#  - generate_delete_XXXX_content
#  - generate_delete_XXXX_summary
#  - generate_content_footer
#
generate_entry()
{
	# --- Arguments
	oldrev=$(git rev-parse $1)
	newrev=$(git rev-parse $2)
	refname="$3"

	# --- Interpret
	# 0000->1234 (create)
	# 1234->2345 (update)
	# 2345->0000 (delete)
	if expr "$oldrev" : '0*$' >/dev/null
	then
		change_type="create"
	else
		if expr "$newrev" : '0*$' >/dev/null
		then
			change_type="delete"
		else
			change_type="update"
		fi
	fi

	# --- Get the revision types
	newrev_type=$(git cat-file -t $newrev 2> /dev/null)
	oldrev_type=$(git cat-file -t "$oldrev" 2> /dev/null)
	case "$change_type" in
	create|update)
		rev="$newrev"
		rev_type="$newrev_type"
		;;
	delete)
		rev="$oldrev"
		rev_type="$oldrev_type"
		;;
	esac

	# The revision type tells us what type the commit is, combined with
	# the location of the ref we can decide between
	#  - working branch
	#  - tracking branch
	#  - unannoted tag
	#  - annotated tag
	case "$refname","$rev_type" in
		refs/tags/*,commit)
			# un-annotated tag
			refname_type="tag"
			short_refname=${refname##refs/tags/}
			;;
		refs/tags/*,tag)
			# annotated tag
			refname_type="annotated tag"
			short_refname=${refname##refs/tags/}
			;;
		refs/heads/*,commit)
			# branch
			refname_type="branch"
			short_refname=${refname##refs/heads/}
			;;
		refs/remotes/*,commit)
			# tracking branch
			refname_type="tracking branch"
			short_refname=${refname##refs/remotes/}
			echo >&2 "*** Push-update of tracking branch, $refname"
			echo >&2 "***  - no entry generated."
			exit 0
			;;
		*)
			# Anything else (is there anything else?)
			echo >&2 "*** Unknown type of update to $refname ($rev_type)"
			echo >&2 "***  - no entry generated"
			exit 1
			;;
	esac

	# Entry parameters
	# The committer will be obtained from the latest existing rev; so
	# for a deletion it will be the oldrev, for the others, then newrev
	committer=$(git show --pretty=full -s $rev | sed -ne "s/^Commit: //p" |
		sed -ne 's/\(.*\) </"\1" </p')
	# The entry subject will contain the best description of the ref
	# that we can build from the parameters
	describe=$(git describe $rev 2>/dev/null)
	if [ -z "$describe" ]; then
		describe=$rev
	fi
	generate_entry_header
	title=$(git log --pretty=oneline --abbrev-commit -n 1 $newrev)
	author=post-receive-atom
	cat <<-EOF
	<id>$oldrev..$newrev</id>
	<title>$title</title>
	<author><name>$author</name></author>
	EOF

	# Call the correct body generation function
	fn_name=general
	case "$refname_type" in
	"tracking branch"|branch)
		fn_name=branch
		;;
	"annotated tag")
		fn_name=atag
		;;
	esac
	echo "<summary type='text'>"
	generate_${change_type}_${fn_name}_summary | html_replace
	echo "</summary>"

	echo "<content type='html'>"
	echo "<pre>" | html_replace
	generate_${change_type}_${fn_name}_content | html_replace
	echo "</pre>" | html_replace
        echo "</content>"

	generate_entry_footer
}

html_replace(){
    sed s/\&/\\\&amp\;/g | sed s/\</\\\&lt\;/g
}

generate_entry_header()
{
    cat <<-EOF
<?xml version='1.0' encoding='utf-8'?>
<entry xmlns:app="http://www.w3.org/2007/app">
	EOF
}

generate_entry_footer()
{
    cat <<-EOF 
</entry>
	EOF
}

generate_content_header()
{
	# --- Entry (all stdout will be the entry)
	# Generate header
	cat <<-EOF
	This is an automated post from the git hooks/post-receive script. It was
	generated because a ref change was pushed to the repository containing
	the project "$projectdesc".

	The $refname_type, $short_refname has been ${change_type}d
	EOF
}

generate_content_footer()
{
	cat <<-EOF


	hooks/post-receive
	--
	$projectdesc
	EOF
}

# --------------- Branches

#
# Called for the creation of a branch
#
generate_create_branch_summary()
{
    # This is a new branch and so oldrev is not valid
    echo "        at  $newrev ($newrev_type)"
}

generate_create_branch_content()
{
	echo $LOGBEGIN
	# This shows all log entries that are not already covered by
	# another ref - i.e. commits that are now accessible from this
	# ref that were previously not accessible (see generate_update_branch_content
	# for the explanation of this command)
	git rev-parse --not --branches | grep -v $(git rev-parse $refname) |
	git rev-list --pretty --stdin $newrev
	echo $LOGEND
}

#
# Called for the change of a pre-existing branch
#
generate_update_branch_summary()
{
	# Consider this:
	#   1 --- 2 --- O --- X --- 3 --- 4 --- N
	#
	# O is $oldrev for $refname
	# N is $newrev for $refname
	# X is a revision pointed to by some other ref, for which we may
	#   assume that an entry has already been generated.
	# In this case we want to issue an entry containing only revisions
	# 3, 4, and N.  Given (almost) by
	#
	#  git-rev-list N ^O --not --all
	#
	# The reason for the "almost", is that the "--not --all" will take
	# precedence over the "N", and effectively will translate to
	#
	#  git-rev-list N ^O ^X ^N
	#
	# So, we need to build up the list more carefully.  git-rev-parse will
	# generate a list of revs that may be fed into git-rev-list.  We can get
	# it to make the "--not --all" part and then filter out the "^N" with:
	#
	#  git-rev-parse --not --all | grep -v N
	#
	# Then, using the --stdin switch to git-rev-list we have effectively
	# manufactured
	#
	#  git-rev-list N ^O ^X
	#
	# This leaves a problem when someone else updates the repository
	# while this script is running.  Their new value of the ref we're working
	# on would be included in the "--not --all" output; and as our $newrev
	# would be an ancestor of that commit, it would exclude all of our
	# commits.  What we really want is to exclude the current value of
	# $refname from the --not list, rather than N itself.  So:
	#
	#  git-rev-parse --not --all | grep -v $(git-rev-parse $refname)
	#
	# Get's us to something pretty safe (apart from the small time between
	# refname being read, and git-rev-parse running - for that, I give up)
	#
	#
	# Next problem, consider this:
	#   * --- B --- * --- O ($oldrev)
	#          \
	#           * --- X --- * --- N ($newrev)
	#
	# That is to say, there is no guarantee that oldrev is a strict subset of
	# newrev (it would have required a --force, but that's allowed).  So, we
	# can't simply say rev-list $oldrev..$newrev.  Instead we find the common
	# base of the two revs and list from there.
	#
	# As above, we need to take into account the presence of X; if another
	# branch is already in the repository and points at some of the revisions
	# that we are about to output - we don't want them.  The solution is as
	# before: git-rev-parse output filtered.
	#
	# Finally, tags:
	#   1 --- 2 --- O --- T --- 3 --- 4 --- N
	#
	# Tags pushed into the repository generate nice shortlog entries that
	# summarise the commits between them and the previous tag.  However,
	# those entries don't include the full commit messages that we output
	# for a branch update.  Therefore we still want to output revisions
	# that have been output on a tag entry.
	#
	# Luckily, git-rev-parse includes just the tool.  Instead of using "--all"
	# we use "--branches"; this has the added benefit that "remotes/" will
	# be ignored as well.

	# List all of the revisions that were removed by this update, in a fast forward
	# update, this list will be empty, because rev-list O ^N is empty.  For a non
	# fast forward, O ^N is the list of removed revisions
	git diff-tree --stat --summary --find-copies-harder $oldrev..$newrev
}
generate_update_branch_content()
{
	rev=""
	for rev in $(git rev-list $oldrev..$newrev)
	do
	  git show "$rev" | sed s/\</\\\&lt\;/ | sed s/\>/\\\&gt\;/
	done
}

#
# Called for the deletion of a branch
#
generate_delete_branch_summary()
{
    echo "       was  $oldrev"
    echo ""
}
generate_delete_branch_content()
{
    echo $LOGEND
    git show -s --pretty=oneline $oldrev
    echo $LOGEND
}

# --------------- Annotated tags

#
# Called for the creation of an annotated tag
#
generate_create_atag_summary()
{
    echo "        at  $newrev ($newrev_type)"
}
generate_create_atag_content()
{
    generate_atag_content
}

#
# Called for the update of an annotated tag (this is probably a rare event
# and may not even be allowed)
#
generate_update_atag_content()
{
    echo "        to  $newrev ($newrev_type)"
    echo "      from  $oldrev (which is now obsolete)"
}
generate_update_atag_content()
{
    generate_atag_content
}

#
# Called when an annotated tag is created or changed
#
generate_atag_summary()
{
	# Use git-for-each-ref to pull out the individual fields from the tag
	eval $(git for-each-ref --shell --format='
	tagobject=%(*objectname)
	tagtype=%(*objecttype)
	tagger=%(taggername)
	tagged=%(taggerdate)' $refname
	)

	echo "   tagging  $tagobject ($tagtype)"
	case "$tagtype" in
	commit)
		# If the tagged object is a commit, then we assume this is a
		# release, and so we calculate which tag this tag is replacing
		prevtag=$(git describe --abbrev=0 $newrev^ 2>/dev/null)

		if [ -n "$prevtag" ]; then
			echo "  replaces  $prevtag"
		fi
		;;
	*)
		echo "    length  $(git cat-file -s $tagobject) bytes"
		;;
	esac
	echo " tagged by  $tagger"
	echo "        on  $tagged"

	echo ""
}
generate_atag_content()
{
    echo $LOGBEGIN

	# Show the content of the tag message; this might contain a change log
	# or release notes so is worth displaying.
	git cat-file tag $newrev | sed -e '1,/^$/d'

	echo ""
	case "$tagtype" in
	commit)
		# Only commit tags make sense to have rev-list operations performed
		# on them
		if [ -n "$prevtag" ]; then
			# Show changes since the previous release
			git rev-list --pretty=short "$prevtag..$newrev" | git shortlog
		else
			# No previous tag, show all the changes since time began
			git rev-list --pretty=short $newrev | git shortlog
		fi
		;;
	*)
		# XXX: Is there anything useful we can do for non-commit objects?
		;;
	esac

	echo $LOGEND
}

#
# Called for the deletion of an annotated tag
#
generate_delete_atag_summary()
{
    echo "       was  $oldrev"
    echo ""
}
generate_delete_atag_content()
{
    echo $LOGEND
    git show -s --pretty=oneline $oldrev
    echo $LOGEND
}

# --------------- General references

#
# Called when any other type of reference is created (most likely a
# non-annotated tag)
#
generate_create_general_summary()
{
    echo "        at  $newrev ($newrev_type)"
}
generate_create_general_content()
{
    generate_general_content
}

#
# Called when any other type of reference is updated (most likely a
# non-annotated tag)
#
generate_update_general_summary()
{
    echo "        to  $newrev ($newrev_type)"
    echo "      from  $oldrev"
}
generate_update_general_content()
{
    generate_general_content
}

#
# Called for creation or update of any other type of reference
#
generate_general_summary()
{
	# Unannotated tags are more about marking a point than releasing a version;
	# therefore we don't do the shortlog summary that we do for annotated tags
	# above - we simply show that the point has been marked, and print the log
	# message for the marked point for reference purposes
	#
	# Note this section also catches any other reference type (although there
	# aren't any) and deals with them in the same way.
    echo ""
}
generate_general_content()
{
	if [ "$newrev_type" = "commit" ]; then
		echo $LOGBEGIN
		git show --no-color --root -s $newrev
		echo $LOGEND
	else
		# What can we do here?  The tag marks an object that is not a commit,
		# so there is no log for us to display.  It's probably not wise to
		# output git-cat-file as it could be a binary blob.  We'll just say how
		# big it is
		echo "$newrev is a $newrev_type, and is $(git cat-file -s $newrev) bytes long."
	fi
}

#
# Called for the deletion of any other type of reference
#
generate_delete_general_summary()
{
	echo "       was  $oldrev"
	echo ""
}
generate_delete_general_content()
{
	echo $LOGEND
	git show -s --pretty=oneline $oldrev
	echo $LOGEND
}

# ---------------------------- main()

# --- Constants
LOGBEGIN="- Log -----------------------------------------------------------------"
LOGEND="-----------------------------------------------------------------------"

# --- Config
# Set GIT_DIR either from the working directory, or from the environment
# variable.
GIT_DIR=$(git rev-parse --git-dir 2>/dev/null)
if [ -z "$GIT_DIR" ]; then
	echo >&2 "fatal: post-receive: GIT_DIR not set"
	exit 1
fi

projectdesc=$(sed -ne '1p' "$GIT_DIR/description")
# Check if the description is unchanged from it's default, and shorten it to a
# more manageable length if it is
if expr "$projectdesc" : "Unnamed repository.*$" >/dev/null
then
	projectdesc="UNNAMED PROJECT"
fi

#recipients=$(git repo-config hooks.mailinglist)
#announcerecipients=$(git repo-config hooks.announcelist)
#envelopesender=$(git-repo-config hooks.envelopesender)
editlink=$(git repo-config hooks.atomcollection)
username=$(git repo-config hooks.atomusername)
password=$(git repo-config hooks.atompassword)

# --- Main loop
# Allow dual mode: run from the command line just like the update hook, or if
# no arguments are given then run as a hook script
if [ -n "$1" -a -n "$2" -a -n "$3" ]; then
	# Output to the terminal in command line mode - if someone wanted to
	# resend an entry; they could redirect the output to curl themselves
	PAGER= generate_entry $2 $3 $1
else
	while read oldrev newrev refname
	do
	  generate_entry $oldrev $newrev $refname |
	  curl -X POST -u $username:$password -H "Content-Type: application/atom+xml;type=entry" $editlink --data-binary @-
	done
fi