# *****************************************************************************
#
# 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.,
# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# Module authors:
#   Markus Zolliker <markus.zolliker@psi.ch>
#
# *****************************************************************************

"""sensirion flow sensor,

onnected via an Arduio Nano on a serial connection
shared with the trinamic hepump valve motor
"""

import math
from frappy.core import Parameter, Readable, IntRange, FloatRange, BoolType, BytesIO, HasIO
from frappy.errors import ProgrammingError


class FlowSensor(HasIO, Readable):
    value = Parameter(unit='ln/min')
    stddev = Parameter('std dev.', FloatRange(unit='ln/min'))
    nsamples = Parameter('number of samples for averaging', IntRange(1,1024), default=160)
    offset = Parameter('offset correction', FloatRange(unit='ln/min'), readonly=False, default=0)
    scale = Parameter('scale factor', FloatRange(), readonly=False, default=2.3)
    saved = Parameter('is the current value saved?', BoolType(), readonly=False)
    pollinterval = Parameter(default=0.2)

    ioClass = BytesIO
    _saved = None

    def command(self, cmd, nvalues=1):
        if len(cmd) == 1:  # its a query
            command = f'{cmd}\n'
        else:
            if len(cmd) > 7:
                raise ProgrammingError('number does not fit into 6 characters')
            command = f'{cmd[0]}{cmd[1:].ljust(6)}\n'
        reply = self.io.communicate(command.encode('ascii'), max(1, nvalues * 9))
        if nvalues == 1:
            return float(reply)
        if nvalues:
            return tuple(float(s) for s in reply.split())
        return None

    def doPoll(self):
        flow, stddev = self.command('?', nvalues=2)
        stddev = stddev / math.sqrt(self.nsamples)
        if (flow, stddev) != (self.value, self.stddev):
            self.value, self.stddev = flow, stddev
        # TODO: treat status (e.g. when reading 0 always)

    def read_value(self):
        self.doPoll()
        return self.value

    def read_nsamples(self):
        return self.command('n')

    def write_nsamples(self, nsamples):
        return self.command(f'n{nsamples}')

    def read_offset(self):
        return self.command('o')

    def write_offset(self, offset):
        return self.command(f'o{offset:.2f}')

    def read_scale(self):
        return self.command('g')

    def write_scale(self, scale):
        return self.command(f'g{scale:.4f}')

    def read_saved(self):
        if self._saved is None:
            self._saved = self.read_scale(), self.read_offset()
            return True
        return self._saved == (self.scale, self.offset)

    def write_saved(self, target):
        if target:
            self.command('s', nvalues=0)