#!/bin/bash

name="debom"
version="1.0"
read -r -d '' help_message <<-EOF
	Remove BOM from a target file
	Usage: debom TARGET [OPTIONS]
	Options:
	 -b, --backup          output a backup file, editing TARGET in-place
	 -d, --dump            print to STDOUT
	 -f, --force           overwrite without asking
	 -h, --help            print this message
	 -n FILE, --name FILE  set output filename (Default: TARGET.new, or
	                         TARGET.bak in backup mode)
	 -q, --quiet           suppress error messages and prompts
	 -v, --verbose         show additional messages
	 -V, --version         print version number and exit
EOF

source /usr/local/lib/mylib.bash

positional=()
quiet=0
verbose=0
backup=0
dump=0
force=0
output_fn=""
while [[ $# -gt 0 ]]; do
  case "$1" in

  -b|--backup)
    debug_msg "Setting backup option to 1 (was ${backup})"
    backup=1
    shift
    ;;

  -d|--dump)
    debug_msg "Setting dump option to 1 (was ${dump})"
    dump=1
    shift
    ;;

  -f|--force)
    debug_msg "Setting force option to 1 (was ${force})"
    force=1
    shift
    ;;

  -h|--help)
    help_msg
    shift
    ;;

  -n|--name)
    debug_msg "Setting output filename to ${2} (was ${output_fn})"
    output_fn="$2"
    shift; shift
    ;;

  -q|--quiet)
    debug_msg "Setting quiet option to 1 (was ${quiet})"
    quiet=1
    shift
    ;;

  -v|--verbose)
    debug_msg "Setting verbose option to 1 (was ${verbose})"
    verbose=1
    shift
    ;;

  -V|--version)
    version_msg
    ;;

  *)
    debug_msg "Argument '${1}' added to positional array"
    positional+=("$1")
    shift
    ;;
  esac
done

# error if no filenames given
if [[ ${#positional[@]} -eq 0 ]]; then
  debug_msg "No input filename was given"
  usage_msg
fi
original_fn="${positional[0]}"

# output filename
if [[ "$dump" -eq 1 ]]; then
  debug_msg "Output is STDOUT"
elif [[ -z "$output_fn" ]]; then
  if [[ "$backup" -eq 1 ]]; then
    debug_msg "No output filename was given, so defaulting to 'TARGET.bak'"
    output_fn="${original_fn}.bak"
  else
    debug_msg "No output filename was given, so defaulting to 'TARGET.new'"
    output_fn="${original_fn}.new"
  fi
else
  debug_msg "Output filename given as '${output_fn}'"
fi

# check if files exist
debug_msg "Beginning file existence checks"
if [[ ! -f "$original_fn" ]]; then
  debug_msg "Input file does not exist"
  error_msg "No such file '${original_fn}'"
elif [[ "$dump" -eq 0 && "$force" -eq 0 && -f "$output_fn" ]]; then
  debug_msg "Output file exists; prompting for permission to overwrite"
  if ! prompt_overwrite "${output_fn}"; then
    debug_msg "Could not obtain permission to overwrite output file"
    exit 1
  fi
fi
debug_msg "Finished file existence checks"

# backup routine
if [[ "$dump" -eq 0 && "$backup" -eq 1 ]]; then
  debug_msg "Beginning backup routine"
  backup_fn="${output_fn}"
  if ! /usr/local/bin/mkbak "${original_fn}" --force --name "${backup_fn}"; then
    error_msg "Error occured while executing backup"
    exit 1
  fi
  output_fn=${original_fn}
  original_fn=${backup_fn}
  debug_msg "Finished backup routine"
fi

# main routine
debug_msg "Beginning main routine"
code=0
if [[ "$dump" -eq 1 ]]; then
  if ! /usr/bin/sed '1s/^\xEF\xBB\xBF//' < "${original_fn}"; then
    code=1
  fi
else
  if ! /usr/bin/sed '1s/^\xEF\xBB\xBF//' < "${original_fn}" > "${output_fn}"; then
    code=1
  fi
fi
debug_msg "Finished main routine"

# return stored code
exit "$code"