Add reverse date order to fetch-year script

Reviewed-on: #2

scripts/fetch-year.sh

@@ -1,14 +1,26 @@
 #!/usr/bin/env bash
-# Usage: ./scripts/fetch-year.sh YEAR
+# Usage: ./scripts/fetch-year.sh YEAR [--reverse]
 # Fetches sequentially; prints JSON responses to stdout and errors to stderr.
 set -euo pipefail
 
-if [[ $# -ne 1 ]]; then
-  echo "Usage: $0 YEAR" >&2
+reverse=false
+year=
+for arg in "$@"; do
+  case "$arg" in
+    --reverse) reverse=true ;;
+    *)
+      if [[ -n $year ]]; then
+        echo "Usage: $0 YEAR [--reverse]" >&2
+        exit 1
+      fi
+      year=$arg
+      ;;
+  esac
+done
+if [[ -z $year ]]; then
+  echo "Usage: $0 YEAR [--reverse]" >&2
   exit 1
 fi
-
-year=$1
 if [[ ! $year =~ ^[0-9]{4}$ || $year == 0000 ]]; then
   echo "YEAR must be a four-digit year from 0001 to 9999." >&2
   exit 1
@@ -66,8 +78,17 @@ fi
 
 # Generate dates without relying on platform-specific date command options.
 status=0
-for (( month = 1; month <= 12; month++ )); do
-  for (( day = 1; day <= days_in_month[month - 1]; day++ )); do
+for (( month_index = 0; month_index < 12; month_index++ )); do
+  month=$((month_index + 1))
+  if [[ $reverse == true ]]; then
+    month=$((12 - month_index))
+  fi
+  days=${days_in_month[month - 1]}
+  for (( day_index = 0; day_index < days; day_index++ )); do
+    day=$((day_index + 1))
+    if [[ $reverse == true ]]; then
+      day=$((days - day_index))
+    fi
     printf -v date '%s-%02d-%02d' "$year" "$month" "$day"
     if ! curl --fail --silent --show-error -X GET \
       "http://localhost:4101/api/price/day/$date" \