#!/usr/bin/env bash

case "$0" in
  ( *egrep* ) grep="egrep" ;;
  ( *fgrep* ) grep="fgrep" ;;
  ( * )       grep="grep"  ;;
esac

if [[ "$#" = "0" || "$1" = "-h" || "$1" = "--help" ]]; then
  cat <<-EOF
	usage:
	  $0 [grep-args] <pattern> [<.ext> ...] [<file-or-dir> ...]
	Will use "grep" to search recursively through the given files or
	directories, which defaults to ".".

	Ignores ".git" ".svn" "CVS" directories by default.  Use
	"--ignore=x,y,z" to set the ignore list, "--ignore=+x,y,z" to
	add to the list, and "--ignore=-x,y,z" to remove from it.

	If an extension is given (a ".[^/]+" argument, possibly with
	(quoted) globs), then only files of these extension will be
	grepped.  (Use "./.foo" for a path that begins with a a ".".)
	If named as something with "egrep" or "fgrep", will use these
	for searching.
EOF
  exit
fi

grep_opts=($GREP_OPTIONS)
unset GREP_OPTIONS
pattern=""
find_opts=()
ignore=",.git,.svn,CVS,"

do_ignore() {
  if [[ "$1" = "+"* ]]; then ignore+="${1#+},"
  elif [[ "$1" = "-"* ]]; then
    for i in ${1//,/ }; do ignore="${ignore//,$i,/,}"; done
  else ignore=",$1,"
  fi
}

while getopts "VEFGPe:f:ivwxycLlm:oqsbHhnTuZA:B:C:aD:d:IrRUz-:" name; do
  if [[ "$name" = "?" ]]; then exit 1
  elif [[ "$name" = "-" ]]; then
    if [[ "$OPTARG" = "ignore" ]]; then do_ignore "$2"; shift
    elif [[ "$OPTARG" = "ignore="* ]]; then do_ignore "${OPTARG#ignore=}"
    else echo "unknown long option: $OPTARG" 1>&2; exit 1
    fi
  elif [[ "$name" = "e" ]]; then       pattern="$OPTARG"
  elif [[ "${OPTARG+x}" = "x" ]]; then grep_opts+=("-$name" "$OPTARG")
  else                                 grep_opts+=("-$name")
  fi
done

shift $(( OPTIND - 1 ))

if [[ -z "$pattern" ]]; then
  if [[ "$#" = "0" ]]; then echo "$0: missing pattern" 1>&2; exit 1
  else pattern="$1"; shift
  fi
fi

fst=1
for i in ${ignore//,/ }; do
  if [[ -z "$i" ]]; then continue; fi
  if (( fst )); then find_opts+=("("); else find_opts+=("-o"); fi
  find_opts+=("-name" "$i"); fst=0
done
if (( !fst )); then find_opts+=(")"); fi

find_opts+=("-prune" "-o")

find_opts+=("-type" "f")
# add extensions to look for if specified
fst=1; rx="^[.][^/]+"
while [[ "$1" =~ $rx ]]; do
  if (( fst )); then find_opts+=("("); else find_opts+=("-o"); fi
  find_opts+=("-name" "*$1"); shift; fst=0
done
if (( !fst )); then find_opts+=(")"); fi

# If there is a single null argument from an emacs `grep', drop it
if [[ "$#" = "1" && "$TERM" = "emacs-grep" ]]; then
  if [[ "$1" = "/dev/null" ]]; then shift; fi
fi

# use "." if there are no arguments
if [[ "$#" = "0" ]]; then set "."; fi

# check that all of the rest are existing paths
for i; do
  if [[ ! -e "$i" ]]; then echo "$0: missing path: $i" 1>&2; exit 1; fi
done

# if not a single path or if a directory, add -H to show file names
# (before other flags so it can be can overriden)
if [[ "$#" != "1" || -d "$1" ]]; then grep_opts=("-H" "${grep_opts[@]}"); fi

# print paths with NUL separators, drop "./" if the only place is "."
if [[ "x$*" = "x." ]]; then find_opts+=("-printf" '%P\0')
else                        find_opts+=("-print0")
fi

# See also the values of emacs vars:
#   grep-find-ignored-directories, grep-find-ignored-files
find "$@" "${find_opts[@]}" \
| sort -z \
| xargs -0 "$grep" "${grep_opts[@]}" -e "$pattern" -- 2>&1 \
| sed 's/\(.\{1999\}\).*/\1.../' # <- trim huge lines