#! /usr/bin/env bash

# Check copyright notices in the COPYRIGHT and LICENSE files and issue a
# warning if they don't include the current year.
#
# Specifically, look first for COPYRIGHT and then LICENSE in the root
# directory and all subdirectories in a project.
#
# Then in each file look for the first line matching the:
#
# ^Copyright (\([cC]\))? ...
#
# Regex, where "..."  matches various year lists/ranges (e.g., "2010", "2010,
# 2011", "2010-2011", and their combinations; see the pattern below for
# details). Specifically, we don't consider Copyright notices that:
#
#   - don't start at the very beginning of a line (indented, etc)
#   - contain something other than years prior to the last year (names, etc)
#   - wrap over multiple lines (long year list, etc)
#
# Note also that the current year is obtained in the UTC timezone.
#
trap 'exit 1' ERR
set -o errtrace # Trap in functions.

function info () { echo "$*" 1>&2; }
function error () { info "$*"; exit 1; }

# Recursively collect the COPYRIGHT and LICENSE files, skipping the LICENSE
# files in directories that contain the COPYRIGHT file.
#
# @@ Note that for now we assume that there are no spaces in the project file
#    and directory names.
#
files=()

fs=($(find . \( -type f -o -type l \) -name COPYRIGHT))

for f in "${fs[@]}"; do
  files+=("$f")
done

fs=($(find . \( -type f -o -type l \) -name LICENSE))

for f in "${fs[@]}"; do
  d="$(dirname "$f")"

  if [ ! -f "$d/COPYRIGHT" ]; then
    files+=("$f")
  fi
done

# Grep for the Copyright notice in the collected files and issue the warning
# if it is present and is outdated.
#
# @@ We should probably skip the COPYRIGHT/LICENSE files whose parent
#    directories don't (recursively) contain staged files (think of projects
#    with multiple packages, bundled third-party code, etc). Note that we can
#    obtain the staged file list with the `git diff --name-only --cached`
#    command.
#
current_year="$(date -u +'%Y')"

for f in "${files[@]}"; do
  year="$(sed -n -re 's%^Copyright( +\([cC]\))?[ 0-9,-]*[ ,-]([0-9]{4}).*$%\2%p' "$f" | head -n 1)"

  if [ -n "$year" -a "$year" != "$current_year" ]; then
    info "WARNING: last copyright year in '${f#./}' is $year"
  fi
done