################################################################################
# Copyright (C) 2014-2017 by GFZ Potsdam
#
# Classes to access an SDS structure to be used by the Dataselect-WS
#
# Author:  Javier Quinteros
# Email:   javier@gfz-potsdam.de
################################################################################

from __future__ import absolute_import, division, print_function

import datetime
import os

import seiscomp.logging
import seiscomp.mseedlite


if hasattr(datetime.timedelta, "total_seconds"):
    def _total_seconds(td):
        return td.total_seconds()
else:
    def _total_seconds(td):
        return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) // 10**6


class SDS(object):
    def __init__(self, sdsRoot):
        if isinstance(sdsRoot, list):
            self.sdsRoot = sdsRoot

        else:
            self.sdsRoot = [sdsRoot]

    def __getMSName(self, reqDate, net, sta, loc, cha):
        for root in self.sdsRoot:
            yield '%s/%d/%s/%s/%s.D/%s.%s.%s.%s.D.%d.%s' % \
                (root, reqDate.year, net, sta, cha, net, sta, loc, cha,
                 reqDate.year, reqDate.strftime('%j'))

    @staticmethod
    def __time2recno(msFile, reclen, timeStart, recStart, timeEnd, recEnd, searchTime):
        if searchTime <= timeStart:
            msFile.seek(recStart * reclen)
            rec = seiscomp.mseedlite.Record(msFile)
            return (recStart, rec.end_time)

        if searchTime >= timeEnd:
            msFile.seek(recEnd * reclen)
            rec = seiscomp.mseedlite.Record(msFile)
            return (recEnd, rec.end_time)

        t1 = timeStart
        r1 = recStart
        t2 = timeEnd
        r2 = recEnd
        rn = int(r1 + (r2 - r1) * _total_seconds(searchTime - t1) /
                 _total_seconds(t2 - t1))

        if rn < recStart:
            rn = recStart

        if rn > recEnd:
            rn = recEnd

        while True:
            msFile.seek(rn * reclen)
            rec = seiscomp.mseedlite.Record(msFile)

            if rec.begin_time < searchTime:
                r1 = rn
                t1 = rec.begin_time

                if t1 == t2:
                    break

                rn = int(r1 + (r2 - r1) * _total_seconds(searchTime -
                                                         t1) / _total_seconds(t2 - t1))

                if rn < recStart:
                    rn = recStart

                if rn > recEnd:
                    rn = recEnd

                if rn == r1:
                    break

            else:
                r2 = rn
                t2 = rec.begin_time

                if t1 == t2:
                    break

                rn = int(r2 - (r2 - r1) * _total_seconds(t2 -
                                                         searchTime) / _total_seconds(t2 - t1))

                if rn < recStart:
                    rn = recStart

                if rn > recEnd:
                    rn = recEnd

                if rn == r2:
                    break

        return (rn, rec.end_time)

    def __getWaveform(self, startt, endt, msFile, bufferSize):
        if startt >= endt:
            return

        rec = seiscomp.mseedlite.Record(msFile)
        reclen = rec.size
        recStart = 0
        timeStart = rec.begin_time

        if rec.begin_time >= endt:
            return

        msFile.seek(-reclen, 2)
        rec = seiscomp.mseedlite.Record(msFile)
        recEnd = msFile.tell() // reclen - 1
        timeEnd = rec.begin_time

        if rec.end_time <= startt:
            return

        if timeStart >= timeEnd:
            seiscomp.logging.error("%s: overlap detected (start=%s, end=%s)" % (
                msFile.name, timeStart, timeEnd))
            return

        (lower, _) = self.__time2recno(
            msFile, reclen, timeStart, recStart, timeEnd, recEnd, startt)
        (upper, _) = self.__time2recno(
            msFile, reclen, startt, lower, timeEnd, recEnd, endt)

        if upper < lower:
            seiscomp.logging.error("%s: overlap detected (lower=%d, upper=%d)" % (
                msFile.name, lower, upper))
            upper = lower

        msFile.seek(lower * reclen)
        remaining = (upper - lower + 1) * reclen
        check = True

        if bufferSize % reclen:
            bufferSize += reclen - bufferSize % reclen

        while remaining > 0:
            size = min(remaining, bufferSize)
            data = msFile.read(size)
            remaining -= size
            offset = 0

            if not data:
                return

            if check:
                while offset < len(data):
                    rec = seiscomp.mseedlite.Record(data[offset:offset+reclen])

                    if rec.begin_time >= endt:
                        return

                    if rec.end_time > startt:
                        break

                    offset += reclen

                check = False

            if offset < len(data):
                yield data[offset:] if offset else data

        while True:
            data = msFile.read(reclen)

            if not data:
                return

            rec = seiscomp.mseedlite.Record(data)

            if rec.begin_time >= endt:
                return

            yield data

    def __getDayRaw(self, day, startt, endt, net, sta, loc, cha, bufferSize):
        # Take into account the case of empty location
        if loc == '--':
            loc = ''

        for dataFile in self.__getMSName(day, net, sta, loc, cha):
            if not os.path.exists(dataFile):
                continue

            try:
                with open(dataFile, 'rb') as msFile:
                    for buf in self.__getWaveform(startt, endt, msFile, bufferSize):
                        yield buf

            except seiscomp.mseedlite.MSeedError as e:
                seiscomp.logging.error("%s: %s" % (dataFile, str(e)))

    def getRawBytes(self, startt, endt, net, sta, loc, cha, bufferSize):
        day = datetime.datetime(startt.year, startt.month,
                                startt.day) - datetime.timedelta(days=1)
        endDay = datetime.datetime(endt.year, endt.month, endt.day)

        while day <= endDay:
            for buf in self.__getDayRaw(day, startt, endt, net, sta, loc, cha, bufferSize):
                yield buf

            day += datetime.timedelta(days=1)