#!/bin/bash

# This script because we support $GIT, $HOMEBREW_SVN, etc., Xcode-only and
# no Xcode/CLT configurations. Order is careful to be what the user would want.

set +o posix

quiet_safe_cd() {
  cd "$1" >/dev/null || { echo "Error: failed to cd to $1" >&2; exit 1; }
}

realpath() {
  local path="$1"
  local dir
  local base
  local dest

  dir="$(quiet_safe_cd "${path%/*}/" && pwd -P)"
  base="${path##*/}"
  path="$dir/$base"

  while [[ -L "$path" ]]
  do
    dest="$(readlink "$path")"
    if [[ "$dest" = "/"* ]]
    then
      path="$dest"
    else
      path="$dir/$dest"
    fi
    dir="$(quiet_safe_cd "${path%/*}/" && pwd -P)"
    base="${path##*/}"
    path="$dir/$base"
  done

  echo "$path"
}

executable() {
  local file="$1"
  [[ -f "$file" && -x "$file" ]]
}

lowercase() {
  echo "$1" | tr "[:upper:]" "[:lower:]"
}

safe_exec() {
  local arg0="$1"
  if ! executable "$arg0"
  then
    return
  fi
  # prevent fork-bombs
  if [[ "$(lowercase "$arg0")" = "$SCM_FILE" || "$(realpath "$arg0")" = "$SCM_REAL" ]]
  then
    return
  fi
  if [[ "$HOMEBREW" = "print-path" ]]
  then
    echo "$arg0"
    exit
  fi
  exec "$@"
}

SCM_FILE="${0##*/}"
SCM_REAL="$(realpath "$0")"
SCM_DIR="$(quiet_safe_cd "${SCM_REAL%/*}/" && pwd -P)"

if [[ "$1" = --homebrew=* ]]
then
  HOMEBREW="${1:11}"
  shift
fi

case "$(lowercase "$SCM_FILE")" in
  git)
    [[ -n "$HOMEBREW_GIT" ]] && safe_exec "$(which "$HOMEBREW_GIT")" "$@"
    [[ -n "$GIT" ]] && safe_exec "$(which "$GIT")" "$@"
    ;;
  svn)
    [[ -n "$HOMEBREW_SVN" ]] && safe_exec "$(which "$HOMEBREW_SVN")" "$@"
    ;;
esac

brew_version="$(quiet_safe_cd "$SCM_DIR/../../../../bin" && pwd -P)/$SCM_FILE"
safe_exec "$brew_version" "$@"

IFS=$'\n'
for path in $(/usr/bin/which -a "$SCM_FILE" 2>/dev/null)
do
  if [[ "$path" != "/usr/bin/$SCM_FILE" ]]
  then
    safe_exec "$path" "$@"
  fi
done

if executable "/usr/bin/xcode-select"
then
  # xcode-select will return empty on no Xcode/CLT configuration.
  #   /usr/bin/<tool> will be a popup stub under such configuration.
  # xcrun hangs if xcode-select is set to "/"
  xcode_path="$(/usr/bin/xcode-select -print-path 2>/dev/null)"
  [[ -n "$xcode_path" ]] || popup_stub=1
  if [[ -z "$popup_stub" && "$xcode_path" != "/" ]]
  then
    path="$(/usr/bin/xcrun -find "$SCM_FILE" 2>/dev/null)"
    safe_exec "$path" "$@"
  fi
fi

path="/Applications/Xcode.app/Contents/Developer/usr/bin/$SCM_FILE"
safe_exec "$path" "$@"

path="/usr/bin/$SCM_FILE"
[[ -z "$popup_stub" ]] && safe_exec "$path" "$@"

echo "You must: brew install $SCM_FILE" >&2
exit 1