#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# GR-GSM based transceiver
# Follow graph implementation
#
# (C) 2016-2019 by Vadim Yanitskiy <axilirator@gmail.com>
# (C) 2017      by Piotr Krysik <ptrkrysik@gmail.com>
#
# All Rights Reserved
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

import pmt
import time
import grgsm
import random

from math import pi

from gnuradio import eng_notation
from gnuradio import digital
from gnuradio import blocks
from gnuradio import uhd
from gnuradio import gr

from gnuradio import filter
from gnuradio.filter import firdes

from dict_toggle_sign import dict_toggle_sign

class RadioInterface(gr.top_block):
	# PHY specific variables
	rx_freq = None
	tx_freq = None
	osr = 4

	# Application state flags
	trx_started = False

	# GSM timings (in microseconds [uS])
	# One timeslot duration is 576.9 μs = 15/26 ms,
	# or 156.25 symbol periods (a symbol period is 48/13 μs)
	GSM_SYM_PERIOD_uS = 48.0 / 13.0
	GSM_TS_PERIOD_uS = GSM_SYM_PERIOD_uS * 156.25
	GSM_UL_DL_SHIFT_uS = -(GSM_TS_PERIOD_uS * 3)

	GSM_SYM_RATE = (1.0 / GSM_SYM_PERIOD_uS) * 1e6
	SAMPLE_RATE = GSM_SYM_RATE * osr

	# FIXME: shall be measured (automatically?) for
	# particular device and particular clock rate.
	# The current value is measured for USRP B2X0 at 26e6.
	delay_correction = (285.616 + 2 * GSM_SYM_PERIOD_uS) * 1e-6

	# Dummy freq. value that is used during initialization
	# basically, the DL freq. of ARFCN 0
	DUMMY_FREQ = 935e6

	def __init__(self, phy_args, phy_sample_rate,
			phy_rx_gain, phy_tx_gain, phy_ppm,
			phy_rx_antenna, phy_tx_antenna,
			phy_freq_offset, trx_bind_addr,
			trx_remote_addr, trx_base_port):

		print("[i] Init Radio interface (L:%s:%u <-> R:%s:%u)"
			% (trx_bind_addr, trx_base_port + 2,
				trx_remote_addr, trx_base_port + 102))

		# PHY specific variables
		self.sample_rate = phy_sample_rate
		self.rx_gain = phy_rx_gain
		self.tx_gain = phy_tx_gain
		self.ppm = phy_ppm
		self.freq_offset = phy_freq_offset

		gr.top_block.__init__(self, "GR-GSM TRX")

		# TRX Burst Interface
		self.trx_burst_if = grgsm.trx_burst_if(
			trx_bind_addr, trx_remote_addr,
			str(trx_base_port))

		# RX path definition
		self.phy_src = uhd.usrp_source(phy_args,
			uhd.stream_args(cpu_format="fc32",
				channels=range(1)))

		self.phy_src.set_clock_rate(26e6, uhd.ALL_MBOARDS)
		self.phy_src.set_antenna(phy_rx_antenna, 0)
		self.phy_src.set_samp_rate(phy_sample_rate)
		self.phy_src.set_bandwidth(650e3, 0)
		self.phy_src.set_gain(phy_rx_gain)

		self.msg_to_tag_src = grgsm.msg_to_tag()

		self.rotator_src = grgsm.controlled_rotator_cc(0.0)

		self.lpf = filter.fir_filter_ccf(1, firdes.low_pass(
			1, phy_sample_rate, 125e3, 5e3, firdes.WIN_HAMMING, 6.76))

		self.gsm_receiver = grgsm.receiver(self.osr, ([0]), ([]))

		self.ts_filter = grgsm.burst_timeslot_filter(0)
		self.ts_filter.set_policy(grgsm.FILTER_POLICY_DROP_ALL)

		# Connections
		self.connect(
			(self.phy_src, 0),
			(self.msg_to_tag_src, 0))

		self.connect(
			(self.msg_to_tag_src, 0),
			(self.rotator_src, 0))

		self.connect(
			(self.rotator_src, 0),
			(self.lpf, 0))

		self.connect(
			(self.lpf, 0),
			(self.gsm_receiver, 0))

		self.msg_connect(
			(self.gsm_receiver, 'C0'),
			(self.ts_filter, 'in'))

		self.msg_connect(
			(self.ts_filter, 'out'),
			(self.trx_burst_if, 'bursts'))


		# TX Path Definition
		self.phy_sink = uhd.usrp_sink(phy_args,
			uhd.stream_args(cpu_format="fc32",
				channels=range(1)), "packet_len")

		self.phy_sink.set_clock_rate(26e6, uhd.ALL_MBOARDS)
		self.phy_sink.set_antenna(phy_tx_antenna, 0)
		self.phy_sink.set_samp_rate(phy_sample_rate)
		self.phy_sink.set_gain(self.tx_gain)

		self.tx_time_setter = grgsm.txtime_setter(
			0xffffffff, 0, 0, 0, 0, 0,
			self.delay_correction + self.GSM_UL_DL_SHIFT_uS * 1e-6)

		self.tx_burst_proc = grgsm.preprocess_tx_burst()

		self.pdu_to_tagged_stream = blocks.pdu_to_tagged_stream(
			blocks.byte_t, 'packet_len')

		self.gmsk_mod = grgsm.gsm_gmsk_mod(
			BT = 0.3, pulse_duration = 4, sps = self.osr)

		self.burst_shaper = digital.burst_shaper_cc(
			(firdes.window(firdes.WIN_HANN, 16, 0)),
			0, 20, False, "packet_len")

		self.msg_to_tag_sink = grgsm.msg_to_tag()

		self.rotator_sink = grgsm.controlled_rotator_cc(0.0)

		# Connections
		self.msg_connect(
			(self.trx_burst_if, 'bursts'),
			(self.tx_time_setter, 'bursts_in'))

		self.msg_connect(
			(self.tx_time_setter, 'bursts_out'),
			(self.tx_burst_proc, 'bursts_in'))

		self.msg_connect(
			(self.tx_burst_proc, 'bursts_out'),
			(self.pdu_to_tagged_stream, 'pdus'))

		self.connect(
			(self.pdu_to_tagged_stream, 0),
			(self.gmsk_mod, 0))

		self.connect(
			(self.gmsk_mod, 0),
			(self.burst_shaper, 0))

		self.connect(
			(self.burst_shaper, 0),
			(self.msg_to_tag_sink, 0))

		self.connect(
			(self.msg_to_tag_sink, 0),
			(self.rotator_sink, 0))

		self.connect(
			(self.rotator_sink, 0),
			(self.phy_sink, 0))


		# RX & TX synchronization
		self.bt_filter = grgsm.burst_type_filter([3])
		self.burst_to_fn_time = grgsm.burst_to_fn_time()

		# Connections
		self.msg_connect(
			(self.gsm_receiver, 'C0'),
			(self.bt_filter, 'bursts_in'))

		self.msg_connect(
			(self.bt_filter, 'bursts_out'),
			(self.burst_to_fn_time, 'bursts_in'))

		self.msg_connect(
			(self.burst_to_fn_time, 'fn_time_out'),
			(self.tx_time_setter, 'fn_time'))


		# AFC (Automatic Frequency Correction)
		# NOTE: dummy frequency is used during init
		self.gsm_clck_ctrl = grgsm.clock_offset_control(
			self.DUMMY_FREQ, phy_sample_rate, osr = self.osr)

		self.dict_toggle_sign = dict_toggle_sign()

		# Connections
		self.msg_connect(
			(self.gsm_receiver, 'measurements'),
			(self.gsm_clck_ctrl, 'measurements'))

		self.msg_connect(
			(self.gsm_clck_ctrl, 'ctrl'),
			(self.msg_to_tag_src, 'msg'))

		self.msg_connect(
			(self.gsm_clck_ctrl, 'ctrl'),
			(self.dict_toggle_sign, 'dict_in'))

		self.msg_connect(
			(self.dict_toggle_sign, 'dict_out'),
			(self.msg_to_tag_sink, 'msg'))


		# Some UHD devices (such as UmTRX) do start the clock
		# not from 0, so it's required to reset it manually.
		# Resetting UHD source will also affect the sink.
		self.phy_src.set_time_now(uhd.time_spec(0.0))

	def shutdown(self):
		print("[i] Shutdown Radio interface")
		self.stop()
		self.wait()

	def calc_phase_inc(self, fc):
		return self.ppm / 1.0e6 * 2 * pi * fc / self.sample_rate

	def set_rx_freq(self, fc):
		fc += self.freq_offset
		print("[#] Shifting RX freq. to %s (offset is %s)"
			% (eng_notation.num_to_str(fc),
				eng_notation.num_to_str(self.freq_offset)))
		self.phy_src.set_center_freq(fc, 0)
		self.rotator_src.set_phase_inc(self.calc_phase_inc(fc))
		self.rx_freq = fc

	def set_tx_freq(self, fc):
		fc += self.freq_offset
		print("[#] Shifting TX freq. to %s (offset is %s)"
			% (eng_notation.num_to_str(fc),
				eng_notation.num_to_str(self.freq_offset)))
		self.phy_sink.set_center_freq(fc, 0)
		self.rotator_sink.set_phase_inc(-self.calc_phase_inc(fc))
		self.tx_freq = fc

	def set_rx_gain(self, gain):
		self.phy_src.set_gain(gain, 0)
		self.rx_gain = gain

	def set_tx_gain(self, gain):
		self.phy_sink.set_gain(gain, 0)
		self.tx_gain = gain

	def set_ta(self, ta):
		print("[i] Setting TA value %d" % ta)
		advance_time_sec = ta * self.GSM_SYM_PERIOD_uS * 1e-6
		self.tx_time_setter.set_timing_advance(advance_time_sec)

	def measure(self, freq):
		# HACK: generate a random low RSSI value
		return random.randint(-120, -100)