#!/usr/bin/env bash

# Provides the get_retrofit_dates helper for identifying missing market-data archives on a remote host.

get_retrofit_dates() {
  local host=${1:-}
  local root_dir=${2:-}
  local filename_glob=${3:-}
  local day_count=${4:-}

  if [[ -z "$host" || -z "$root_dir" || -z "$filename_glob" || -z "$day_count" ]]; then
    echo "usage: get_retrofit_dates <host> <root_dir> <filename_glob> <day_count>" >&2
    return 1
  fi

  if ! [[ "$day_count" =~ ^[0-9]+$ ]] || (( day_count <= 0 )); then
    echo "get_retrofit_dates: <day_count> must be a positive integer" >&2
    return 1
  fi

  local -a target_dates=()
  declare -A month_dirs=()

  if ! date -d "1 day ago" +%Y%m%d >/dev/null 2>&1; then
    echo "get_retrofit_dates: requires GNU date arithmetic" >&2
    return 1
  fi

  local offset date
  for (( offset = 1; offset <= day_count; offset++ )); do
    date=$(date -d "$offset day ago" +%Y%m%d)
    target_dates+=("$date")
    month_dirs["${date:0:4}/${date:4:2}"]=1
  done

  declare -A existing_dates=()

  local dir remote_path remote_cmd remote_output entry
  for dir in "${!month_dirs[@]}"; do
    remote_path="$root_dir/$dir"
    printf -v remote_cmd "cd %q 2>/dev/null && LC_ALL=C ls -1" "$remote_path"
    remote_output=$(ssh "$host" "$remote_cmd" 2>/dev/null || true)

    if [[ -n "$remote_output" ]]; then
      while IFS= read -r entry; do
        [[ -z "$entry" ]] && continue
        [[ $entry == $filename_glob ]] || continue
        if [[ "$entry" =~ ^([0-9]{8}) ]]; then
          existing_dates["${BASH_REMATCH[1]}"]=1
        fi
      done <<<"$remote_output"
    fi
  done

  local -a missing_dates=()
  local idx
  for (( idx = ${#target_dates[@]} - 1; idx >= 0; idx-- )); do
    local dt=${target_dates[$idx]}
    [[ -n "${existing_dates[$dt]:-}" ]] || missing_dates+=("$dt")
  done

  printf '%s\n' "${missing_dates[@]}"
}