#!/usr/bin/env node

/**
* @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.
*/

'use strict';

// MODULES //

var proc = require( 'process' );
var resolve = require( 'path' ).resolve;
var readFileSync = require( '@stdlib/fs/read-file' ).sync;
var writeFileSync = require( '@stdlib/fs/write-file' ).sync;
var CLI = require( '@stdlib/cli/ctor' );
var stdout = require( '@stdlib/streams/node/stdout' );
var cwd = require( '@stdlib/process/cwd' );
var Uint8Array = require( '@stdlib/array/uint8' );
var Uint32Array = require( '@stdlib/array/uint32' );
var isUint8Array = require( '@stdlib/assert/is-uint8array' );
var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
var gcopy = require( '@stdlib/blas/base/gcopy' );
var array2buffer = require( '@stdlib/buffer/from-array' );
var randomStream = require( './../lib' );


// FUNCTIONS //

/**
* Callback invoked once a source stream ends.
*
* @private
*/
function onEnd() {
	// Append a trailing newline in accordance with standard POSIX behavior:
	console.log( '' ); // eslint-disable-line no-console
}

/**
* Attempts to load a PRNG state.
*
* @private
* @param {string} filepath - absolute path to file containing PRNG state
* @returns {(Uint32Array|Error)} PRNG state or an error
*/
function loadState( filepath ) {
	var state;
	var len;

	state = readFileSync( filepath );
	if ( state instanceof Error ) {
		return state;
	}
	len = state.length;

	// For older Node.js environments, convert the `Buffer` to a `Uint8Array`...
	if ( !isUint8Array( state ) ) {
		state = gcopy( len, state, 1, new Uint8Array( len ), 1 );
	}
	// Create a PRNG state array "view":
	len /= Uint32Array.BYTES_PER_ELEMENT;
	if ( !isInteger( len ) ) {
		return new RangeError( 'invalid option. `state` has an invalid length.' );
	}
	return new Uint32Array( state.buffer, state.byteOffset, len );
}


// MAIN //

/**
* Main execution sequence.
*
* @private
* @returns {void}
*/
function main() {
	var stream;
	var flags;
	var opts;
	var args;
	var cli;
	var err;
	var dir;
	var i;

	// Create a command-line interface:
	cli = new CLI({
		'pkg': require( './../package.json' ),
		'options': require( './../etc/cli_opts.json' ),
		'help': readFileSync( resolve( __dirname, '..', 'docs', 'usage.txt' ), {
			'encoding': 'utf8'
		})
	});

	// Get any provided command-line options:
	flags = cli.flags();
	if ( flags.help || flags.version ) {
		return;
	}

	// Get the current working directory:
	dir = cwd();

	// Get any provided command-line arguments:
	args = cli.args();
	if ( args.length < 1 ) {
		err = new Error( 'insufficient arguments. Must provide distribution parameters.' );
		return onError( err );
	}
	args[ 0 ] = parseFloat( args[ 0 ] );

	opts = {};
	if ( flags.iter ) {
		opts.iter = parseInt( flags.iter, 10 );
	}
	if ( flags.sep ) {
		opts.sep = flags.sep;
	}
	if ( flags.state ) {
		opts.state = loadState( resolve( dir, flags.state ) );
		if ( opts.state instanceof Error ) {
			return onError( opts.state );
		}
	} else if ( flags.seed ) {
		opts.seed = flags.seed.split( ',' );
		for ( i = 0; i < opts.seed.length; i++ ) {
			opts.seed[ i ] = parseInt( opts.seed[ i ], 10 );
		}
	}
	if ( flags.snapshot ) {
		proc.on( 'exit', onExit );
	}

	// Create a source stream and pipe to `stdout`:
	stream = randomStream( args[ 0 ], opts );
	stream.on( 'end', onEnd );

	stream.pipe( stdout );

	/**
	* Callback invoked upon exiting the process.
	*
	* @private
	* @param {integer} code - exit code
	*/
	function onExit( code ) {
		var state;
		var err;

		// Get the current PRNG state:
		state = stream.state;

		// Create a byte array "view":
		state = new Uint8Array( state.buffer, state.byteOffset, stream.byteLength ); // eslint-disable-line max-len

		// Convert the byte array to a `Buffer` (with support for older Node.js environments):
		state = array2buffer( state );

		// Attempt to write the state to file:
		err = writeFileSync( resolve( dir, flags.snapshot ), state );
		if ( err ) {
			onError( err, code || 1 );
		}
	}

	/**
	* Callback invoked upon encountering an error.
	*
	* @private
	* @param {Error} error - error
	* @param {integer} [code] - exit code
	*/
	function onError( error, code ) {
		cli.error( error, code || 1 );
	}
}

main();