import struct
import os
import random
from math import *

class BPhysWriter:
    # BPHYS_DATA_* from DNA_object_force.h
    column_words = (1,3,3,4,3,1,3,5)
    column_formats = ("i", "fff", "fff", "ffff", "fff", "f", "fff", "fffff")

    def __init__(self, f, flags):
        f.write(b"BPHYSICS")
        self.f = f
        self.count=0
        flavor=1
        f.write(struct.pack("iii", flavor, self.count, flags))

        self.format = ""
        for i in range(len(BPhysWriter.column_words)):
            if 0 != (flags & (1<<i)):
                self.format += BPhysWriter.column_formats[i]


    def store(self, *elements):
        i=self.count
        f = self.f
        self.count+=1
        f.seek(12)
        f.write(struct.pack("i", self.count))

        f.seek(0,2)
        f.write(struct.pack(self.format, *elements))


# http://blender.stackexchange.com/questions/15577/how-to-extract-convert-data-from-blender-cache-files-bphys-into-a-human-readabl

class CacheRowReader:
    # BPHYS_DATA_* from DNA_object_force.h
    column_words = (1,3,3,4,3,1,3,5)
    column_formats = ("i", "fff", "fff", "ffff", "fff", "f", "fff", "fffff")

    def __init__(self, flavor, count, data_type_flags):
        self.count = count
        self.flavor = flavor
        self.data_type_flags = data_type_flags

        rec_len=0
        unpack_format = ""
        for i in range(len(CacheRowReader.column_words)):
            if 0 != (data_type_flags&(1<<i)):
                rec_len += 4 * CacheRowReader.column_words[i]
                unpack_format += CacheRowReader.column_formats[i]

        self.rec_len = rec_len
        self.unpack_format = unpack_format

    @classmethod
    def parse(cls, f):

        magic = f.read(8)
        if magic != b'BPHYSICS':
            raise Exception("not a blender physics cache")

        flavor = f.read(12)
        (flavor,count,data_type_flags) = struct.unpack("iii", flavor)

        #print( "%d\t%d\t%d"%(flavor,count,data_type_flags))

        return CacheRowReader(flavor, count, data_type_flags)

    def read_row(self, f):
        """
        :param f: a file opened with "rb" (binary) mode
        :return:
        """
        raw = f.read(self.rec_len)

        if raw is None or len(raw)==0:
            return None
        if len(raw) != self.rec_len:
            raise Exception("short read (%d<%d)"%( len(raw), self.rec_len))

        columns = struct.unpack(self.unpack_format, raw)

        rval = dict()
        cursor =0
        # a lot of these clauses are untested.  Feel free to leave me a comment on the stackexchange answer.
        if 0 != (self.data_type_flags&1):
            rval['index'] = columns[cursor]
            cursor +=1
        if 0 != self.data_type_flags&2:
            rval['location'] = columns[cursor:cursor+3]
            rval['smoke_low'] = rval['location']
            cursor +=3
        if 0 != self.data_type_flags&4:
            rval['velocity'] = columns[cursor:cursor+3]
            rval['smoke_high'] = rval['velocity']
            cursor +=3
        if 0 != self.data_type_flags&8:
            rval['dynamicpaint'] = rval['rotation'] = columns[cursor:cursor+4]
            cursor +=4
        if 0 != self.data_type_flags&0x10:
            rval['xconst'] = rval['avelocity'] = columns[cursor:cursor+3]
            cursor +=3
        if 0 != self.data_type_flags&0x20:
            rval['size'] = columns[cursor]
            cursor +=1
        if 0 != self.data_type_flags&0x40:
            rval['times'] = columns[cursor:cursor+3]
            cursor +=3
        if 0 != self.data_type_flags&0x80:
            rval['boids'] = columns[cursor:cursor+5]
            cursor +=5

        return rval

#
#
#

def mission1():
    cache_pattern = "blendcache_particle-loop/synth_%06d_00.bphys"

    create_particle_cache(cache_pattern, 1, 250)

ncols=40
nrows = ncols
particleCount = ncols*nrows

def locationForParticle(pnum, frame):

    u = pnum%ncols
    v = floor(pnum/ncols)
    x = (u/ncols -0.5)*8
    y = (v/nrows -0.5)*8

    r = sqrt(x*x+y*y)
    loopPeriodFrames = 250
    phase1 = 2*pi * frame/loopPeriodFrames
    z = 0.2*cos(r*5+phase1*5)

    return x,y,z

def create_particle_cache(cache_pattern, frame_start, frame_end):

    fpattern = cache_pattern

    with open(fpattern % 0, "wb") as out:
        phys = BPhysWriter(out, 0x40)
        # XXX blender 2.80 does not fully respect this file
        # and will rewrite the particle timings if
        # you use Alt-A to play long enough to reach the end and start a second play cycle.

        life = 9999
        for i in range(particleCount):
            tm = i / (10 * particleCount)
            phys.store(tm, tm + life, life)

    for frame in range(frame_start, frame_end + 1):
        fname = fpattern % frame
        with open(fname, "wb") as out:
            phys = BPhysWriter(out, 3)
            good_count = 0
            for idx in range(particleCount):
                x, y, z = locationForParticle(idx, frame)
                if (frame == frame_start):
                    print(idx, x, y, z)
                phys.store(idx, x, y, z)
            print("wrote %s"%fname)


def set_pad(list, idx, val):
    """list[idx] = val
    even if list is short, we'll pad it with None-s until we can fit the value in the correct slot"""
    while len(list) < idx:
        list.append(None)
    list.insert(idx, val)


#
#
#

mission1()