#!/bin/bash
set -u
shopt -s extglob

abort() {
  printf "%s\n" "$@"
  exit 1
}

strip_s() {
  local s
  for s in "$@"; do
    s=${s## }
    echo "${s%% }"
  done
}

dir_children() {
  local p
  for p in "$@"; do
    [[ -d $p ]] || continue
    find "$p" -mindepth 1 -maxdepth 1
  done
}

# Set up temp dir
tmpdir=/tmp/uninstall.$$
mkdir -p "$tmpdir" || abort "Unable to create temp dir '$tmpdir'"
trap '
  rm -fr "$tmpdir"
  # Invalidate sudo timestamp before exiting
  /usr/bin/sudo -k
' EXIT

# Default options
opt_force=""
opt_quiet=""
opt_dry_run=""
opt_skip_cache_and_logs=""

# global status to indicate whether there is anything wrong.
failed=false

un=$(uname)
case "$un" in
  Linux)
    ostype=linux
    homebrew_prefix_default=/home/linuxbrew/.linuxbrew
  ;;
  Darwin)
    ostype=macos
    homebrew_prefix_default=/usr/local
    realpath() {
      cd "$(dirname "$1")" && echo "$(pwd -P)/$(basename "$1")"
    }
  ;;
  *)
    abort "Unsupported system type '$un'"
  ;;
esac

# string formatters
if [[ -t 1 ]]; then
  tty_escape() { printf "\033[%sm" "$1"; }
else
  tty_escape() { :; }
fi
tty_mkbold() { tty_escape "1;${1:-39}"; }
tty_blue=$(tty_mkbold 34)
tty_red=$(tty_mkbold 31)
tty_bold=$(tty_mkbold 39)
tty_reset=$(tty_escape 0)

have_sudo_access() {
  local -a args
  if [[ -n "${SUDO_ASKPASS-}" ]]; then
    args=("-A")
  fi

  if [[ -z "${HAVE_SUDO_ACCESS-}" ]]; then
    if [[ -n "${args[*]-}" ]]; then
      /usr/bin/sudo "${args[@]}" -l mkdir &>/dev/null
    else
      /usr/bin/sudo -l mkdir &>/dev/null
    fi
    HAVE_SUDO_ACCESS="$?"
  fi

  if [[ -z "${HOMEBREW_ON_LINUX-}" ]] && [[ "$HAVE_SUDO_ACCESS" -ne 0 ]]; then
    abort "Need sudo access on macOS (e.g. the user $USER to be an Administrator)!"
  fi

  return "$HAVE_SUDO_ACCESS"
}

shell_join() {
  local arg
  printf "%s" "$1"
  shift
  for arg in "$@"; do
    printf " "
    printf "%s" "${arg// /\ }"
  done
}

resolved_pathname() { realpath "$1"; }

pretty_print_pathnames() {
  local p
  for p in "$@"; do
    if [[ -h $p ]]; then
      printf '%s -> %s\n' "$p" "$(resolved_pathname "$p")"
    elif [[ -d $p ]]; then
      echo "$p/"
    else
      echo "$p"
    fi
  done
}

chomp() {
  printf "%s" "${1/"$'\n'"/}"
}

ohai() {
  printf "${tty_blue}==>${tty_bold} %s${tty_reset}\n" "$(shell_join "$@")"
}

warn() {
  printf "${tty_red}Warning${tty_reset}: %s\n" "$(chomp "$1")"
}

execute() {
  if ! "$@"; then
    abort "$(printf "Failed during: %s" "$(shell_join "$@")")"
  fi
}

execute_sudo() {
  local -a args=("$@")
  if [[ -n "${SUDO_ASKPASS-}" ]]; then
    args=("-A" "${args[@]}")
  fi
  if have_sudo_access; then
    ohai "/usr/bin/sudo" "${args[@]}"
    system "/usr/bin/sudo" "${args[@]}"
  else
    ohai "${args[@]}"
    system "${args[@]}"
  fi
}

system() {
  if ! "$@"; then
    warn "Failed during: $(shell_join "$@")"
    failed=true
  fi
}

####################################################################### script

homebrew_prefix_candidates=()

usage() {
  cat <<EOS
Homebrew Uninstaller
Usage: $0 [options]
    -p, --path=PATH  Sets Homebrew prefix. Defaults to /usr/local.
        --skip-cache-and-logs
                     Skips removal of HOMEBREW_CACHE and HOMEBREW_LOGS.
    -f, --force      Uninstall without prompting.
    -q, --quiet      Suppress all output.
    -d, --dry-run    Simulate uninstall but don't remove anything.
    -h, --help       Display this message.
EOS
  exit "${1:-0}"
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    -p*) homebrew_prefix_candidates+=("${1#-p}");;
    --path=*) homebrew_prefix_candidates+=("${1#--path=}");;
    --skip-cache-and-logs) opt_skip_cache_and_logs=1;;
    -f|--force) opt_force=1;;
    -q|--quiet) opt_quiet=1;;
    -d|--dry-run) opt_dry_run=1;;
    -h|--help) usage;;
    *) warn "Unrecognized option: '$1'"; usage 1;;
  esac
  shift
done

if [[ ${#homebrew_prefix_candidates[@]} -eq 0 ]]; then # Attempt to locate Homebrew unless `--path` is passed
  prefix=$(brew --prefix)
  [[ -n $prefix ]] && homebrew_prefix_candidates+=("$prefix")
  prefix=$(command -v brew) || prefix=""
  [[ -n $prefix ]] && homebrew_prefix_candidates+=("$(dirname "$(dirname "$(strip_s "$prefix")")")")
  homebrew_prefix_candidates+=("$homebrew_prefix_default") # Homebrew default path
  homebrew_prefix_candidates+=("$HOME/.linuxbrew") # Linuxbrew default path
fi

HOMEBREW_PREFIX=$(for p in "${homebrew_prefix_candidates[@]}"; do
  [[ -d $p ]] || continue
  [[ $p == "$homebrew_prefix_default" && -d $p/Homebrew/.git ]] && echo "$p" && break
  [[ -d $p/.git || -x $p/bin/brew ]] && echo "$p" && break
done)
[[ -n $HOMEBREW_PREFIX ]] || abort "Failed to locate Homebrew!"

if [[ -d $HOMEBREW_PREFIX/.git ]]; then
  HOMEBREW_REPOSITORY=$(dirname "$(realpath "$HOMEBREW_PREFIX/.git")")
elif [[ -x $HOMEBREW_PREFIX/bin/brew ]]; then
  HOMEBREW_REPOSITORY=$(dirname "$(dirname "$(realpath "$HOMEBREW_PREFIX/bin/brew")")")
else
  abort "Failed to locate Homebrew!"
fi

if [[ -d $HOMEBREW_PREFIX/Cellar ]]; then
  HOMEBREW_CELLAR=$HOMEBREW_PREFIX/Cellar
else
  HOMEBREW_CELLAR=$HOMEBREW_REPOSITORY/Cellar
fi

if [[ -s $HOMEBREW_REPOSITORY/.gitignore ]]; then
  gitignore=$(<"$HOMEBREW_REPOSITORY/.gitignore")
else
  gitignore=$(curl -fsSL https://raw.githubusercontent.com/Homebrew/brew/master/.gitignore)
fi
[[ -n $gitignore ]] || abort "Failed to fetch Homebrew .gitignore!"

{
  while read -r l; do
    [[ $l == \!* ]] || continue
    l=${l#\!}
    l=${l#/}
    [[ $l == @(bin|share|share/doc) ]] && echo "REJECT: $l" >&2 && continue
    echo "$HOMEBREW_REPOSITORY/$l"
  done <<<"$gitignore"

  if [[ $HOMEBREW_PREFIX != "$HOMEBREW_REPOSITORY" ]]; then
    echo "$HOMEBREW_REPOSITORY"
    for p in \
      bin/brew \
      etc/bash_completion.d/brew \
      share/doc/homebrew \
      share/man/man1/brew.1 \
      share/man/man1/brew-cask.1 \
      share/zsh/site-functions/_brew \
      share/zsh/site-functions/_brew_cask \
      var/homebrew \
    ; do
      echo "$HOMEBREW_PREFIX/$p"
    done
  else
    echo "$HOMEBREW_REPOSITORY/.git"
  fi
  echo "$HOMEBREW_CELLAR"
  echo "$HOMEBREW_PREFIX/Caskroom"

  [[ -n $opt_skip_cache_and_logs ]] || cat <<-EOS
	$HOME/Library/Caches/Homebrew
	$HOME/Library/Logs/Homebrew
	/Library/Caches/Homebrew
	$HOME/.cache/Homebrew
	${HOMEBREW_CACHE:-}
	${HOMEBREW_LOGS:-}
	EOS

  if [[ $ostype == macos ]]; then
    dir_children "/Applications" "$HOME/Applications" | while read -r p2; do
      [[ $(resolved_pathname "$p2") == $HOMEBREW_CELLAR/* ]] && echo "$p2"
    done
  fi
} | while read -r l; do
  [[ -e $l ]] && echo "$l"
done | sort -u > "$tmpdir/homebrew_files"
homebrew_files=()
while read -r l; do
  homebrew_files+=("$l")
done < "$tmpdir/homebrew_files"

if [[ -z $opt_quiet ]]; then
  dry_str=${opt_dry_run:+would}
  warn "This script ${dry_str:-will} remove:"
  pretty_print_pathnames "${homebrew_files[@]}"
fi

if [[ -t 0 && -z $opt_force && -z $opt_dry_run ]]; then
  read -rp "Are you sure you want to uninstall Homebrew? This will remove your installed packages! [y/N] "
  [[ $REPLY == [yY]* ]] || abort
fi

[[ -n $opt_quiet ]] || ohai "Removing Homebrew installation..."
paths=()
for p in Frameworks bin etc include lib opt sbin share var; do
  p=$HOMEBREW_PREFIX/$p
  [[ -e $p ]] && paths+=("$p")
done
if [[ ${#paths[@]} -gt 0 ]]; then
  if [[ $ostype == macos ]]; then
    args=(-E "${paths[@]}" -regex '.*/info/([^.][^/]*\.info|dir)')
  else
    args=("${paths[@]}" -regextype posix-extended -regex '.*/info/([^.][^/]*\.info|dir)')
  fi
  if [[ -n $opt_dry_run ]]; then
    args+=(-print)
    echo "Would delete:"
  else
    args+=(-exec /bin/bash -c)
    args+=("/usr/bin/install-info --delete --quiet {} \"\$(dirname {})/dir\"")
    args+=(';')
  fi
  system /usr/bin/find "${args[@]}"
  args=("${paths[@]}" -type l -lname '*/Cellar/*')
  if [[ -n $opt_dry_run ]]; then
    args+=(-print)
  else
    args+=(-exec unlink '{}' ';')
  fi
  [[ -n $opt_dry_run ]] && echo "Would delete:"
  system /usr/bin/find "${args[@]}"
fi

for file in "${homebrew_files[@]}"; do
  if [[ -n $opt_dry_run ]]; then
    echo "Would delete ${file}"
  else
    if ! err=$(rm -fr "$file" 2>&1); then
      warn "Failed to delete ${file}"
      echo "$err"
    fi
  fi
done

sudo() {
  ohai "/usr/bin/sudo" "$@"
  system /usr/bin/sudo "$@"
}

[[ -n $opt_quiet ]] || ohai "Removing empty directories..."
paths=()
for p in bin etc include lib opt sbin share var \
         Caskroom Cellar Homebrew Frameworks; do
  p=$HOMEBREW_PREFIX/$p
  [[ -e $p ]] && paths+=("$p")
done
if [[ ${#paths[@]} -gt 0 ]]; then
  if [[ $ostype == macos ]]; then
    args=("${paths[@]}" -name .DS_Store)
    if [[ -n $opt_dry_run ]]; then
      args+=(-print)
      echo "Would delete:"
    else
      args+=(-delete)
    fi
    execute_sudo /usr/bin/find "${args[@]}"
  fi
  args=("${paths[@]}" -depth -type d -empty)
  if [[ -n $opt_dry_run ]]; then
    args+=(-print)
    echo "Would remove directories:"
  else
    args+=(-exec rmdir '{}' ';')
  fi
  execute_sudo /usr/bin/find "${args[@]}"
fi

[[ -n $opt_dry_run ]] && exit
if [[ $HOMEBREW_PREFIX != "$homebrew_prefix_default" && -e $HOMEBREW_PREFIX ]]; then
   execute_sudo rmdir "$HOMEBREW_PREFIX"
fi
if [[ $HOMEBREW_PREFIX != "$HOMEBREW_REPOSITORY" && -e $HOMEBREW_REPOSITORY ]]; then
   execute_sudo rmdir "$HOMEBREW_REPOSITORY"
fi

if [[ -z $opt_quiet ]]; then
  if [[ $failed == true ]]; then
    warn "Homebrew partially uninstalled (but there were steps that failed)!"
    echo "To finish uninstalling rerun this script with \`sudo\`."
  else
    ohai "Homebrew uninstalled!"
  fi
fi

dir_children "$HOMEBREW_REPOSITORY" "$HOMEBREW_PREFIX" \
  | sort -u > "$tmpdir/residual_files"

if [[ -s $tmpdir/residual_files && -z $opt_quiet ]]; then
  echo "The following possible Homebrew files were not deleted:"
  while read -r f; do
    pretty_print_pathnames "$f"
  done <"$tmpdir/residual_files"
  echo -e "You may wish to remove them yourself.\n"
fi

[[ $failed != true ]]