# Copyright 2012 Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
# * Neither the name of Google Inc. nor the names of its contributors
#   may be used to endorse or promote products derived from this software
#   without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# \file lib.subr
# Common initialization and functions for shell scripts.


set -e


# Directory where the running script lives.
Lib_DirName="$(dirname ${0})"


# Base name of the running script.
Lib_ProgName="${0##*/}"


# Path to the temporary directory for this execution.
Lib_TempDir=


# List of cleanup functions to execute on exit.
_Lib_Cleanup_Hooks=


# Catch unexpected exits and perform the required cleanups.  In particular,
# ensure that the temporary directory in Lib_TempDir, if any, is removed.
trap 'lib_cleanup ; exit 2' HUP INT QUIT TERM


# Prints an informational message.
#
# \param ... The message to print.  Can be provided as multiple words and, in
#     that case, they are joined together by a single whitespace.
lib_info() {
    echo "${Lib_ProgName}: I: $*" 1>&2
}


# Prints a runtime error and exits.
#
# \param ... The message to print.  Can be provided as multiple words and, in
#     that case, they are joined together by a single whitespace.
lib_error() {
    echo "${Lib_ProgName}: E: $*" 1>&2
    exit 1
}


# Prints a runtime warning.
#
# \param ... The message to print.  Can be provided as multiple words and, in
#     that case, they are joined together by a single whitespace.
lib_warning() {
    echo "${Lib_ProgName}: W: $*" 1>&2
}


# Prints an usage error and exits.
#
# \param ... The message to print.  Can be provided as multiple words and, in
#     that case, they are joined together by a single whitespace.
lib_usage_error() {
    echo "${Lib_ProgName}: E: $*" 1>&2
    usage "${Lib_ProgName}" 1>&2
    exit 1
}


# Executes the registered cleanup hooks.
lib_cleanup() {
    local hook
    for hook in ${_Lib_Cleanup_Hooks}; do
        "${hook}"
    done
}


# Installs a new cleanup hook.
#
# \param ... The names of the cleanup functions to register.
lib_register_cleanup() {
    _Lib_Cleanup_Hooks="${_Lib_Cleanup_Hooks} ${*}"
}


# Creates a temporary directory for this execution.
#
# The temporary directory is unique to this script and execution.  A cleanup
# hook is installed to delete such directory whenever lib_cleanup is called or
# when the program abruptly exits.
#
# \post Lib_TempDir is set to the path of the created temporary directory.
lib_init_tempdir() {
    Lib_TempDir=$(mktemp -d -t "${_Lib_ProgName}.XXXXXX")
    lib_register_cleanup "lib_clean_tempdir"
}


# Cleanup hook to delete the temporary directory.
#
# This operation is idempotent.
lib_clean_tempdir() {
    if [ -n "${Lib_TempDir}" ]; then
        rm -rf "${Lib_TempDir}"
        Lib_TempDir=
    fi
}