#!/usr/bin/env bash

set -o nounset

function usage() {
  cat <<EOF
Usage: $0 [-h] [-n] [-s style] [-a name]

Display an activity graph (like the contribution graph on GitHub) for the
current git repository and branch

Available options:

-h, --help      Print this help and exit
-n, --no-space  Remove spaces between week columns
-s, --style     Sets style of the graph: square (default), block, or plus
-a, --author    Select for an author (passed to git log)
EOF
}

# Parse options
space=" "
style=square
author=""
while [[ $# -gt 0 ]]; do
  case "$1" in
    -s|--style)
      style="$2"
      shift 2
      ;;
    -a|--author)
        author="$2"
        shift 2
        ;;
    -n|--no-space) space="" ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "Unexpected option ${1}" >&2
      usage
      exit 1
      ;;
  esac
  shift
done

# Style argument
case "${style}" in
square)
  char_full="■"
  char_void="${char_full}"
  ;;
block)
  char_full="█"
  char_void="${char_full}"
  ;;
plus)
  char_full="✚"
  char_void="•"
  ;;
*)
  echo "error: style '${style}' not recognized (square block plus)" >&2;
  exit 1;;
esac

# Use GNU date if available
if date --version >/dev/null 2>&1 ; then
  function _date { date "$@" ;}
elif gdate >/dev/null 2>&1 ; then
  function _date { gdate "$@" ;}
else
  echo "You need to install coreutils to run this script (command 'gdate' is not available).";
  exit 1;
fi

# Process commits per day
declare -A commits_per_day
commits_max=0
since=$(_date -d "$(_date -d '1 year ago + 1 day' +"%F -%u day")" +"%s")
while read -r commits_n commits_date; do
  (( commits_n > commits_max )) && commits_max=$commits_n
  date_diff=$(( ($(_date --date="${commits_date} 13:00 UTC" "+%s") - since) / (60*60*24) ))
  commits_per_day["${date_diff}"]=$commits_n
done <<< $(git log --author="${author}" --since="${since}" --date=short --pretty=format:'%ad'  | uniq -c)

# Print name of months
current_month=$(_date "+%b")
limit_columns=$(( 2 - ${#space} ))
weeks_in_month=$(( limit_columns + 1 ))
printf "\e[m    "
for week_n in $(seq 0 52); do
  month_week=$(_date -d "1 year ago + ${week_n} weeks" "+%b")
  if [[ "${current_month}" != "${month_week}" ]]; then
    current_month=$month_week
    weeks_in_month=0
    printf "%-3s%s" "${current_month:0:3}" "$space"
  elif [[ $weeks_in_month -gt $limit_columns ]]; then
    printf " %s" "$space"
  fi
  weeks_in_month=$(( weeks_in_month + 1 ))
done
printf "\n"

# Print activity
last_day=$(( ($(_date "+%s") - since) / (60*60*24) ))
name_of_days=("" "Mon" "" "Wed" "" "Fri" "" "")
for day_n in $(seq 0 6); do
  printf '\e[m%-4s' "${name_of_days[day_n]}"
  for week_n in $(seq 0 52); do
    key=$(( week_n * 7 + day_n ))
    if [[ -v commits_per_day["${key}"] ]]; then
      value=$(( ${commits_per_day["${key}"]}00 / commits_max))
      if (( value <= 25 )); then
        # Low activity
        printf "\x1b[38;5;22m%s%s" "$char_full" "$space"
      elif (( value <= 50 )); then
        # Mid-low activity
        printf "\x1b[38;5;28m%s%s" "$char_full" "$space"
      elif (( value <= 75 )); then
        # Mid-high activity
        printf "\x1b[38;5;34m%s%s" "$char_full" "$space"
      else
        # High activity
        printf "\x1b[38;5;40m%s%s" "$char_full" "$space"
      fi
    elif [ $key -lt $last_day ]; then
      # No activity
      printf "\x1b[38;5;250m%s%s" "$char_void" "$space"
    fi
  done
  printf "\n"
done
printf "\n"

# Print legend
printf "\e[m Less "
printf "\x1b[38;5;250m%s " "$char_void"
printf "\x1b[38;5;22m%s " "$char_full"
printf "\x1b[38;5;28m%s " "$char_full"
printf "\x1b[38;5;34m%s " "$char_full"
printf "\x1b[38;5;40m%s " "$char_full"
printf "\e[mMore"
printf "\n"