#! /bin/sh

VERBOSE=false
MARKDOWN=false

while [ $# -gt 0 ]; do
    case "$1" in
    --verbose)
	VERBOSE=true
	;;
    --markdown)
	MARKDOWN=true
	;;
    -*)
	echo "Usage: $0 [--verbose] [--markdown] <last-tag>" >&2
	exit 1
	;;
    *)
	if [ -n "$PREV_TAG" ]; then
	    echo "Usage: $0 [--verbose] [--markdown] <last-tag>" >&2
	    exit 1
	fi
	PREV_TAG="$1"
	;;
    esac
    shift
done

if [ -z "$PREV_TAG" ]; then
    echo "Usage: $0 [--verbose] [--markdown] <last-tag>" >&2
    exit 1
fi

if [ -z "$(git tag -l "$PREV_TAG")" ]; then
    echo "Error: couldn't find tag '$PREV_TAG'!" >&2
    exit 1
fi

# Avoid ambiguity with branch names like v26.04.
if git show-ref --tags --quiet --verify "refs/tags/$PREV_TAG"; then
    PREV_TAG="refs/tags/$PREV_TAG"
fi

git log "$PREV_TAG".. --format="%an|%ae" | sort | uniq -c | sort -rn > /tmp/authors.$$
sed -n 's/.*[Nn]amed by //p' < CHANGELOG.md | sed 's/(.*)//' | tr -dc '[:alnum:][:space:]' > /tmp/namers.$$
git log "$PREV_TAG" --format="%an|%ae" | sort -u > /tmp/prev-authors.$$
# Include aliases
printf "Alex Myers\nShahanaFarooqui\nMatt Whitlock\nSangbida Chaudhuri\n" >> /tmp/namers.$$

display_tag=${PREV_TAG#refs/tags/}
if $MARKDOWN; then
    MARKDOWN_OUT=/tmp/markdown.$$
    HAS_NEWCOMMITTERS=false
    : > "$MARKDOWN_OUT"
fi

NAMER=""
BACKUP_NAMER=""
TOTAL=0
while read LINE; do
    COUNT=$(echo "$LINE" | sed -r "s/[^0-9].*//")
    TOTAL=$((TOTAL + COUNT))
    LINE=${LINE#*[1234567890] }
    NAME=${LINE%%|*}
    EMAIL=${LINE#*|}
    NOTES=""
    if [ "$(grep -ci -- "$NAME\|$EMAIL" /tmp/prev-authors.$$)" = 0 ]; then
	NOTES="$NOTES""NEW COMMITTER "
    fi
    # ZmnSCPxj gave himself a surname!
    if [ "${NAME%% *}" = ZmnSCPxj ]; then
	NAME=ZmnSCPxj
    fi
    if ! grep -qi -- "$NAME" /tmp/namers.$$; then
	if [ -z "$NAMER" ]; then
	    NAMER="$NAME"
	    NOTES="$NOTES""*NEXT NAMER* "
	elif [ -z "$BACKUP_NAMER" ]; then
	    BACKUP_NAMER="$NAME"
	    NOTES="$NOTES""*BACKUP NAMER* "
	fi
    fi
    if $MARKDOWN; then
	case "$EMAIL" in
	*@users.noreply.github.com)
	    HANDLE=$(echo "$EMAIL" | sed -n 's/.*+\([^@]*\)@users.noreply.github.com/\1/p')
	    if [ -z "$HANDLE" ]; then
		HANDLE=$(echo "$EMAIL" | sed 's/@users.noreply.github.com//')
	    fi
	    DISPLAY="@$HANDLE"
	    ;;
	*)
	    DISPLAY="$NAME"
	    ;;
	esac
	if echo "$NOTES" | grep -q "NEW COMMITTER"; then
	    echo "- $DISPLAY ($COUNT commits, *)" >> "$MARKDOWN_OUT"
	    HAS_NEWCOMMITTERS=true
	else
	    echo "- $DISPLAY ($COUNT commits)" >> "$MARKDOWN_OUT"
	fi
    elif [ -n "$NOTES" ] || $VERBOSE; then
	echo " - $COUNT $NAME $EMAIL $NOTES"
    fi
done < /tmp/authors.$$

DAYS=$(( ( $(date +%s) - $(git log "$PREV_TAG" --format=%at | head -n1) ) / (3600*24) ))

AUTHORS=$(wc -l < /tmp/authors.$$ | tr -d ' ')
if $MARKDOWN; then
    echo "## Since **$display_tag** we've had $TOTAL commits in $DAYS days by $AUTHORS authors"
    echo
    echo "### Contributors (ordered from most to fewest commits)"
    echo
    cat "$MARKDOWN_OUT"
    if $HAS_NEWCOMMITTERS; then
	echo
	echo "* Special thanks to our first-time contributors"
    fi
    rm "$MARKDOWN_OUT"
else
    echo "$TOTAL commits in $DAYS days by $AUTHORS authors"
fi
rm /tmp/authors.$$ /tmp/namers.$$ /tmp/prev-authors.$$