#!/bin/sh

copyright='Daniel Scharrer'

die() {
	printf '%s\n' "$1"
	exit 1
}

if [ -z "$1" ] || [ ! -d "$1" ]
	then repo="$(git rev-parse --show-toplevel)"
	else repo="$1" ; shift
fi
[ -d "$repo/.git" ] || die "$1 is not a git repository"

if [ -z "$1" ]
	then last_tag="$(git --git-dir="$repo/.git" rev-list --tags --max-count=1)"
	else last_tag="$1"
fi
[ -z "$last_tag" ] && die "Could not determine last tag"
last_tag_name="$(git --git-dir="$repo/.git" describe --tags "$last_tag")"
printf 'Updating files modified since %s\n' "$last_tag_name"

files="$(git --git-dir="$repo/.git" diff --name-only "$last_tag" HEAD | tr '\n' ' ')"
eval "set -- LICENSE COPYING $files"

for file ; do
	path="$repo/$file"
	[ -f "$path" ] || continue # File was deleted
	
	case "$file" in
		*.yml|.*)
			# Never try to update the copyright year for these files
			continue ;;
	esac
	
	c="$(grep -P "(^|[^a-zA-Z0-9_])Copyright( \\([cC]\\))? (\\d{4}\\-)?\\d{4} $copyright" "$file")"
	
	if [ -z "$c" ] ; then
		case "$file" in
			cmake/*.cpp|*CMakeLists.txt|*.md|*.1|*.in|LICENSE.*)
				# These files don't have to contain copyright information
				;;
			*.*|scripts/*)
				c="$(grep -P "(^|[^a-zA-Z0-9_])Copyright( \([cC]\))?[ \:].*public domain" "$file")"
				[ -z "$c" ] && printf 'No copyright info found in %s, skipping\n' "$file" ;;
		esac
		continue
	fi
	
	if [ "$(printf '%s\n' "$c" | wc -l)" -gt 1 ] ; then
		printf 'Multiple copyright lines found in %s, skipping\n' "$file"
		continue
	fi
	
	s='\(^.*Copyright\( ([cC])\)\? \([0-9]\{4\}\-\)\?\)\([0-9]\{4\}\)\( '"$copyright"'.*$\)'
	old_year="$(printf '%s\n' "$c" | sed "s/$s/\\4/")"
	if [ -z "$old_year" ] || printf '%s\n' "$old_year" | grep -P '[^0-9]' > /dev/null ; then
		printf 'Could not determine new copyright year for %s, skipping\n' "$file"
		continue
	fi
	
	case "$file" in
		COPYING|LICENSE)
			new_year="$(git --git-dir="$repo/.git" log -1 --format=%cd --date=short)" ;;
		*)
			new_year="$(git --git-dir="$repo/.git" log -1 --format=%cd --date=short -- "$path")"
	esac
	new_year="${new_year%%-*}"
	if [ -z "$new_year" ] || printf '%s\n' "$new_year" | grep -P '[^0-9]' > /dev/null ; then
		printf 'Could not determine new copyright year for %s, skipping\n' "$file"
		continue
	fi
	
	[ "$new_year" = "$old_year" ] && continue
	
	if [ ! "$new_year" -gt "$old_year" ] ; then
		printf 'Copyright downgrade in %s: %s→%s, skipping\n' "$file" "$old_year" "$new_year"
		continue
	fi
	
	first_year="$(printf '%s\n' "$c" | sed "s/$s/\\3/")"
	if [ -z "$first_year" ] ; then
		replacement="$old_year-$new_year"
		old="$old_year"
		new="$old_year-$new_year"
	else
		replacement="$new_year"
		old="$first_year$old_year"
		new="$first_year$new_year"
	fi
	
	printf '%s: %s → %s\n' "$file" "$old" "$new"
	sed -i "s/$s/\\1$replacement\\5/" "$path"
	
done