#!/usr/bin/env bash
# Remove all but the latest N versions of files matching given prefixes
# Usage: prune-files -k 3 thisfileprefix [thatfileprefix]

set -euo pipefail

prune-files() {
  local -a PREFIXES
  local KEEP_INT=1 # default number of files to keep
  local DRY_RUN=false

  printHelpAndExit() {
    cat <<-'EOF'
			USAGE:
			  prune-files -k 3 thisfileprefix [thatfileprefix]

			OPTIONS:
			  -k, --keep NUMBER
			    Keep NUMBER of the latest files that match each file prefix (Default: 1)
			  -n, --dry-run
			    Show what would be removed without actually deleting files
			  -h, --help
			    Print this help dialog and exit
		EOF
    [[ -z "$1" ]] && exit 0 || exit "$1"
  }

  parseInput() {
    local _input
    if _input=$(getopt -o hk:n -l help,keep:,dry-run -- "$@"); then
      eval set -- "$_input"
      while true; do
        case "$1" in
          -k|--keep) shift; KEEP_INT="$1" ;;
          -n|--dry-run) DRY_RUN=true ;;
          -h|--help) printHelpAndExit 0 ;;
          --) shift; break ;;
        esac
        shift
      done
    else
      echo "[ERROR] Incorrect option(s) provided" >&2
      printHelpAndExit 1
    fi
    
    if [[ $# -eq 0 ]]; then
      echo "[ERROR] At least one file prefix must be provided" >&2
      printHelpAndExit 1
    fi
    
    if ! [[ "$KEEP_INT" =~ ^[0-9]+$ ]] || [[ "$KEEP_INT" -lt 1 ]]; then
      echo "[ERROR] --keep must be a positive integer" >&2
      exit 1
    fi
    
    PREFIXES=("$@")
  }

  findAndRemove() {
    local prefix file count

    for prefix in "${PREFIXES[@]}"; do
      count=0
      echo "[INFO] Processing files with prefix: $prefix"
      
      # List files matching the prefix sorted by modification time (latest first),
      # then remove all except the first KEEP_INT files.
      while IFS= read -r file; do
        if [[ "$DRY_RUN" == true ]]; then
          echo "[DRY-RUN] Would remove: $file"
        else
          echo "[INFO] Removing: $file"
          if ! rm -- "$file"; then
            echo "[ERROR] Failed to remove: $file" >&2
          fi
        fi
        ((count++))
      done < <(
        find . -maxdepth 1 -type f -name "${prefix}*" -printf '%T@ %p\n' 2>/dev/null | \
        sort -rn | \
        awk -v keep="$KEEP_INT" 'NR > keep {print $2}'
      )
      
      if [[ $count -eq 0 ]]; then
        echo "[INFO] No files to remove for prefix: $prefix"
      else
        echo "[INFO] Processed $count file(s) for prefix: $prefix"
      fi
    done
  }

  main() {
    parseInput "$@"
    findAndRemove
  }

  main "$@"
}

# Allow script to be safely sourced
if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
  prune-files "$@"
  exit $?
fi