#!/usr/bin/env bash
set -euo pipefail

HABITS_FILE="${HABITS_FILE:-$HOME/.local/share/os/habits.md}"

usage() {
  cat <<'EOF'
Usage: habits <command>

Commands:
  open       Open the habits file in $EDITOR
  new        Add a new day to the habits file
  left  Print today's habits that are not done yet
EOF
}

ensure_file() {
  mkdir -p "$(dirname "$HABITS_FILE")"
  touch "$HABITS_FILE"
}

open_habits() {
  ensure_file
  "${EDITOR:-vi}" "$HABITS_FILE"
}

new_day() {
  ensure_file

  local date
  date="$(date +%F)"

  if grep -q "^# $date$" "$HABITS_FILE"; then
    echo "A habits entry for $date already exists: $HABITS_FILE" >&2
    exit 1
  fi

  local tmp
  tmp="$(mktemp)"

  {
    printf '# %s\n\n' "$date"
    printf '## Habits\n\n'
    while IFS= read -r habit; do
      [ -n "$habit" ] && printf -- '- [ ] %s\n' "$habit"
    done <<< "$HABITS"
    printf '\n## Metrics \n\n'
    while IFS= read -r metric; do
      [ -n "$metric" ] && printf -- '- %s\n' "$metric" ":"
    done <<< "$METRICS"
    printf '\n'
    cat "$HABITS_FILE"
  } > "$tmp"

  mv "$tmp" "$HABITS_FILE"
  echo "Added $date to $HABITS_FILE"
}

remaining_habits() {
  ensure_file

  local date
  date="$(date +%F)"

  awk -v date="$date" '
    $0 == "# " date { in_day = 1; next }
    in_day && /^# / { exit }
    in_day && /^## Habits[[:space:]]*$/ { in_habits = 1; next }
    in_day && in_habits && /^## / { exit }
    in_day && in_habits && /^- \[ \] / {
      sub(/^- \[ \] /, "")
      print
    }
  ' "$HABITS_FILE"
}

case "${1:-}" in
  open)
    open_habits
    ;;
  new)
    new_day
    ;;
  left)
    remaining_habits
    ;;
  -h|--help|help)
    usage
    ;;
  *)
    usage >&2
    exit 1
    ;;
esac