#!/usr/bin/env bash
#
# @license Apache-2.0
#
# Copyright (c) 2018 The Stdlib Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Script for compiling a C example.
#
# Usage: compile_c_example <filepath>
#
# Arguments:
#
#   filepath      Example file path.
#
#
# Environment Variables:
#
#   OS            Host operating system. Default: `linux`.
#   NODE          Command for running Node.js. Default: `node`.
#   NODE_PATH     Path for resolving node modules.
#   C_COMPILER    C compiler. Default: `gcc`.
#   BLAS          BLAS library to use.
#   BLAS_DIR      BLAS library path (if custom).
#   CEPHES        Cephes mathematical library path.
#   CEPHES_SRC    List of Cephes source files.
#   INCLUDE       Includes (e.g., `-I /foo/bar -I /a/b`).
#   SOURCE_FILES  Source file list.
#   LIBRARIES     Linked libraries (e.g., `-lopenblas -lpthreads`).
#   LIBPATH       Library paths (e.g., `-L /foo/bar -L /a/b`).
#


# VARIABLES #

# Set the example file path:
file_path="$1"

# Define the host operating system:
os="${OS}"
if [[ "${os}" = "Darwin" ]]; then
	os='mac'
elif [[ "${os}" = "WINNT" ]]; then
	os='win'
else
	os='linux'
fi

# Define the command for running Node.js:
node_cmd="${NODE}"
if [[ -z "${node_cmd}" ]]; then
	node_cmd='node'
fi

# Define the node path:
node_path="${NODE_PATH}"

# Define the path to a C compiler:
c_compiler="${C_COMPILER}"
if [[ -z "${c_compiler}" ]]; then
	c_compiler='gcc'
fi

# Define the BLAS library to use:
blas="${BLAS}"

# Define the BLAS directory:
blas_dir="${BLAS_DIR}"

# Define the path to the Cephes mathematical library:
cephes="${CEPHES}"

# List of Cephes source files:
cephes_src="${CEPHES_SRC}"

# Define a list of `include` directories (e.g., `-I /foo/bar -I /beep/boop/include`):
include="${INCLUDE}"

# Define a list of source files:
source_files="${SOURCE_FILES}"

# Define a list of libraries (e.g., `-lopenblas -lpthreads`):
libraries="${LIBRARIES}"

# Define a list of library paths (e.g., `-L /foo/bar -L /beep/boop`):
libpath="${LIBPATH}"


# FUNCTIONS #

# Defines an error handler.
#
# $1 - error status
on_error() {
	echo 'ERROR: An error was encountered during execution.' >&2
	cleanup
	exit "$1"
}

# Runs clean-up tasks.
cleanup() {
	echo '' >&2
}

# Prints a success message.
print_success() {
	echo 'Success!' >&2
}

# Prints usage information.
usage() {
	echo '' >&2
	echo 'Usage: compile_c_example <filepath>' >&2
	echo '' >&2
}

# Resolves a package path.
#
# $1 - source directory
resolve_pkg_path() {
	local pkg_path
	local script

	# Generate the script for resolving a package path:
	script='"'"var resolve = require('@stdlib/fs/resolve-parent-path').sync; var dirname = require('@stdlib/utils/dirname'); var opts = {'dir':'$1'}; var path = resolve('package.json', opts); console.log(dirname(path));"'"'

	# Resolve package path:
	pkg_path=$(eval NODE_PATH="${node_path}" "${node_cmd}" -e "${script}")

	echo "${pkg_path}"
}

# Resolves a package `manifest.json`.
#
# $1 - package path
resolve_pkg_manifest() {
	if [[ -e "$1/manifest.json" ]]; then
		return 0
	fi
	return 1
}

# Resolves `include` directories.
#
# $1 - package directory
resolve_includes() {
	local includes
	local script
	local opts

	# WARNING: the following assumes knowledge of the `manifest.json` options for BLAS packages. Were those options to change, the following would need to be updated.
	if [[ -n "${blas}" ]]; then
		opts="{'os':'${os}','blas':'${blas}','task':'examples'}"
	else
		opts="{'os':'${os}','task':'examples'}"
	fi
	# Generate the script for resolving `include` directories:
	script='"'"var path = require('path'); var arr = require('@stdlib/utils/library-manifest')(path.join('$1','manifest.json'),${opts},{'basedir':'$1','paths':'posix'}).include; var str = ''; for (var i = 0; i < arr.length; i++){var p = path.resolve('$1', arr[i]); str += '-I '+p+' ';}; console.log(str.substring(0, str.length-1));"'"'

	# Resolve `include` directories:
	includes=$(eval NODE_PATH="${node_path}" "${node_cmd}" -e "${script}")

	if [[ -n "${blas}" ]]; then
		if [[ -n "${blas_dir}" ]]; then
			echo "${includes} -I ${blas_dir}"
		else
			echo "${includes}"
		fi
	else
		echo "${includes}"
	fi
}

# Resolves source files.
#
# $1 - package directory
resolve_source_files() {
	local source_files
	local script
	local opts

	# WARNING: the following assumes knowledge of the `manifest.json` options for BLAS packages. Were those options to change, the following would need to be updated.
	if [[ -n "${blas}" ]]; then
		opts="{'os':'${os}','blas':'${blas}','task':'examples'}"
	else
		opts="{'os':'${os}','task':'examples'}"
	fi
	# Generate the script for resolving source files:
	script='"'"var path = require('path'); var arr = require('@stdlib/utils/library-manifest')(path.join('$1','manifest.json'),${opts},{'basedir':'$1','paths':'posix'}).src; var str = ''; for (var i = 0; i < arr.length; i++){var p = path.resolve('$1', arr[i]); str += p+' ';}; console.log(str.substring(0, str.length-1));"'"'

	# Resolve files:
	source_files=$(eval NODE_PATH="${node_path}" "${node_cmd}" -e "${script}")

	echo "${source_files}"
}

# Resolves libraries.
#
# $1 - package directory
resolve_libraries() {
	local libraries
	local script
	local opts

	# WARNING: the following assumes knowledge of the `manifest.json` options for BLAS packages. Were those options to change, the following would need to be updated.
	if [[ -n "${blas}" ]]; then
		opts="{'os':'${os}','blas':'${blas}','task':'examples'}"
	else
		opts="{'os':'${os}','task':'examples'}"
	fi
	# Generate the script for resolving libraries:
	script='"'"var path = require('path'); var arr = require('@stdlib/utils/library-manifest')(path.join('$1','manifest.json'),${opts},{'basedir':'$1','paths':'posix'}).libraries; var str = ''; for (var i = 0; i < arr.length; i++){str += arr[i]+' ';}; console.log(str.substring(0, str.length-1));"'"'

	# Resolve libraries:
	libraries=$(eval NODE_PATH="${node_path}" "${node_cmd}" -e "${script}")

	echo "${libraries}"
}

# Resolves library paths.
#
# $1 - package directory
resolve_libpaths() {
	local libpath
	local script
	local opts

	# WARNING: the following assumes knowledge of the `manifest.json` options for BLAS packages. Were those options to change, the following would need to be updated.
	if [[ -n "${blas}" ]]; then
		opts="{'os':'${os}','blas':'${blas}','task':'examples'}"
	else
		opts="{'os':'${os}','task':'examples'}"
	fi
	# Generate the script for resolving library paths:
	script='"'"var path = require('path'); var arr = require('@stdlib/utils/library-manifest')(path.join('$1','manifest.json'),${opts},{'basedir':'$1','paths':'posix'}).libpath; var str = ''; for (var i = 0; i < arr.length; i++){var p = path.resolve('$1', arr[i]); str += '-L '+p+' ';}; console.log(str.substring(0, str.length-1));"'"'

	# Resolve library paths:
	libpath=$(eval NODE_PATH="${node_path}" "${node_cmd}" -e "${script}")

	if [[ -n "${blas}" ]]; then
		if [[ -n "${blas_dir}" ]]; then
			echo "${libpath} -L ${blas_dir}"
		else
			echo "${libpath}"
		fi
	else
		echo "${libpath}"
	fi
}

# Compiles example.
#
# $1 - source directory
compile() {
	cd "$1" && C_COMPILER="${c_compiler}" INCLUDE="${include}" SOURCE_FILES="${source_files}" LIBRARIES="${libraries}" LIBPATH="${libpath}" CEPHES="${cephes}" CEPHES_SRC="${cephes_src}" make 2>&1
	if [[ "$?" -ne 0 ]]; then
		echo 'Error when attempting to compile example.' >&2
		return 1
	fi
	echo 'Successfully compiled example.' >&2
	return 0
}


# MAIN #

# Main execution sequence.
main() {
	local pkg_path
	local manifest
	local src_dir

	echo 'Resolving package path...' >&2
	pkg_path=$(resolve_pkg_path "${src_dir}")
	if [[ "$?" -ne 0 ]]; then
		on_error 1
	fi
	echo "Package path: ${pkg_path}" >&2

	echo 'Resolving package manifest...' >&2
	manifest=$(resolve_pkg_manifest "${pkg_path}")
	if [[ "$?" -eq 0 ]]; then
		echo 'Successfully resolved package manifest.' >&2
		if [[ -z "${include}" ]]; then
			echo 'Resolving include directories...' >&2
			include=$(resolve_includes "${pkg_path}")
			if [[ "$?" -ne 0 ]]; then
				on_error 1
			fi
		fi
		if [[ -z "${source_files}" ]]; then
			echo 'Resolving source files...' >&2
			source_files=$(resolve_source_files "${pkg_path}")
			if [[ "$?" -ne 0 ]]; then
				on_error 1
			fi
		fi
		if [[ -z "${libraries}" ]]; then
			echo 'Resolving libraries...' >&2
			libraries=$(resolve_libraries "${pkg_path}")
			if [[ "$?" -ne 0 ]]; then
				on_error 1
			fi
		fi
		if [[ -z "${libpath}" ]]; then
			echo 'Resolving library paths...' >&2
			libpath=$(resolve_libpaths "${pkg_path}")
			if [[ "$?" -ne 0 ]]; then
				on_error 1
			fi
		fi
	else
		echo 'Unable to resolve package manifest.' >&2
	fi
	echo 'Compiling example...' >&2
	src_dir=$(dirname "${file_path}")
	compile "${src_dir}"
	if [[ "$?" -ne 0 ]]; then
		on_error 1
	fi
	print_success
	cleanup
	exit 0
}

# Handle arguments...
if [[ "$#" -eq 0 ]]; then
	usage
	exit 0
elif [[ "$#" -gt 1 ]]; then
	echo 'ERROR: unrecognized arguments. Must provide a file path.' >&2
	exit 1
fi

# Run main:
main