from nullptr.models import *
from os.path import isfile, dirname, isdir
import os
from os.path import basename
import json
from .util import *
from time import time
import pickle
from struct import unpack, pack
from functools import partial
from io import BytesIO

class StorePickler(pickle.Pickler):
  def persistent_id(self, obj):
    return "STORE" if type(obj) == Store else None

class StoreUnpickler(pickle.Unpickler):
  def __init__(self, stream, store):
    self.store = store
    super().__init__(stream)
    
  def persistent_load(self, pers_id):
    if pers_id == "STORE":
      return self.store
    raise pickle.UnpicklingError("I don know the persid!")
     
        
class ChunkHeader:
  def __init__(self):
    self.offset = 0
    self.in_use = True
    self.size = 0
    self.used = 0
    
  @classmethod
  def parse(cls, fil):
    offset = fil.tell()
    d = fil.read(16)
    if len(d) < 16:
      return None
    o = cls()
    o.offset = offset
    d, o.used = unpack('<QQ', d)
    o.size =   d & 0x7fffffffffffffff
    o.in_use = d & 0x8000000000000000 != 0
    # print(o)
    return o
  
  def write(self, f):
    d = self.size
    if self.in_use:
      d |= 1 << 63
    d = pack('<QQ', d, self.used)
    f.write(d)
  
  def __repr__(self):
    return f'chunk {self.in_use} {self.size} {self.used}'
    
class Store:
  def __init__(self, data_file):
    self.init_models()
    self.fil = open_file(data_file)
    self.data = {m: {} for m in self.models}
    self.system_members = {}
    self.dirty_objects = set()
    self.cleanup_interval = 600
    self.last_cleanup = 0
    self.slack = 0.1
    self.slack_min = 64
    self.slack_max = 1024
    self.load()
  
  def init_models(self):
    self.models = all_subclasses(Base)
    self.extensions = {c.ext(): c for c in self.models}
    self.model_names = {c.__name__: c for c in self.models}
    
  def dirty(self, obj):
    self.dirty_objects.add(obj)
  
  def dump_object(self, obj):
    buf = BytesIO()
    p = StorePickler(buf)
    p.dump(obj)
    return buf.getvalue()
  
  def load_object(self, data, offset):
    buf = BytesIO(data)
    p = StoreUnpickler(buf, self)
    obj = p.load()
    obj.file_offset = offset
    obj.disable_dirty = False
    self.hold(obj)
    
  def load(self):
    cnt = 0
    start_time = time()
    total = 0
    free = 0
    self.fil.seek(0)
    offset = 0
    while (hdr := ChunkHeader.parse(self.fil)):
      # print(hdr)
      total += hdr.size
      if not hdr.in_use: 
        self.fil.seek(hdr.size, 1)
        free += hdr.size
        continue
      data = self.fil.read(hdr.used)
      self.load_object(data, offset)
      self.fil.seek(hdr.size - hdr.used, 1)
      offset = self.fil.tell()
      cnt += 1
      
    dur = time() - start_time
    print(f'Loaded {cnt} objects in {dur:.2f} seconds')
    print(f'Fragmented space: {free} / {total} bytes')
  
  def allocate_chunk(self, sz):
    used = sz
    slack = sz * self.slack
    slack = min(slack, self.slack_max)
    slack = max(slack, self.slack_min)
    sz += int(slack)
    self.fil.seek(0, 2)
    offset = self.fil.tell()
    h = ChunkHeader()
    h.size = sz
    h.used = used
    h.offset = self.fil.tell()
    h.write(self.fil)
    return offset, h
    
  def purge(self, obj):
    if obj.file_offset is None:
      return
    self.fil.seek(obj.file_offset)
    hdr = ChunkHeader.parse(self.fil)
    hdr.in_use = False
    self.fil.seek(obj.file_offset)
    hdr.write(self.fil)
    obj.file_offset = None
    
  def store(self, obj):
    data = self.dump_object(obj)
    osize = len(data)
    # is there an existing chunk for this obj?
    if obj.file_offset is not None:
      # read chunk hdr
      self.fil.seek(obj.file_offset)
      hdr = ChunkHeader.parse(self.fil)
      csize = hdr.size
      # if the chunk is too small
      if csize < osize:
        # free the chunk
        hdr.in_use = False
        # force a new chunk
        obj.file_offset = None
      else:
        # if it is big enough, update the used field
        hdr.used = osize
      self.fil.seek(hdr.offset)
      hdr.write(self.fil)
        
    if obj.file_offset is None:
      obj.file_offset, hdr = self.allocate_chunk(osize)
    # print(type(obj).__name__, hdr)
    self.fil.write(data)
    slack = b'\x00' * (hdr.size - hdr.used)
    self.fil.write(slack)
    
  def hold(self, obj):
    typ = type(obj)
    symbol = obj.symbol
    obj.store = self
    self.data[typ][symbol] = obj
    if hasattr(obj, 'system') and obj.system != None:
      system_str = obj.system.symbol
      if system_str not in self.system_members:
        self.system_members[system_str] = set()
      self.system_members[system_str].add(obj)
  
  def create(self, typ, symbol):
    obj = typ(symbol, self)
    self.hold(obj)
    self.dirty(obj)
    return obj
    
  def get(self, typ, symbol, create=False):
    if type(typ) == str and typ in self.model_names:
      typ = self.model_names[typ]
    symbol = symbol.upper()
    if typ not in self.data:
      return None
    if symbol not in self.data[typ]:
      if create:
        return self.create(typ, symbol)
      else:
        return None
    return self.data[typ][symbol]
  
  def getter(self, typ, create=False):
    if type(typ) == str and typ in self.model_names:
      typ = self.model_names[typ]
    return partial(self.get, typ, create=create)
  
  def update(self, typ, data, symbol=None):
    if type(typ) == str and typ in self.model_names:
      typ = self.model_names[typ] 
    if symbol is None:
      symbol = mg(data, typ.identifier)
    obj = self.get(typ, symbol, True)
    obj.update(data)
    return obj
  
  def update_list(self, typ, lst):
    return [self.update(typ, d) for d in lst]
    
  def all(self, typ):
    if type(typ) == str and typ in self.model_names:
      typ = self.model_names[typ]
    
    for m in self.data[typ].values():
      if m.is_expired():
        self.dirty(m)
        continue
      yield m
  
  def all_members(self, system, typ=None):
    if type(typ) == str and typ in self.model_names:
      typ = self.model_names[typ]
    
    if type(system) == System:
      system = system.symbol
    
    if system not in self.system_members:
      return 
    
    garbage = set()
    for m in self.system_members[system]:
      if m.is_expired():
        self.dirty(m)
        garbage.add(m)
        continue
      if typ is None or type(m) == typ:
        yield m
    
    for m in garbage:
      self.system_members[system].remove(m)
      
  def cleanup(self):
    if time() < self.last_cleanup + self.cleanup_interval:
      return
    self.last_cleanup = time()
    start_time = time()
    expired = list()
    for t in self.data:
      for o in self.all(t):
        if o.is_expired():
          expired.append(o)
    for o in expired:
      self.purge(obj)
      
      del self.data[type(o)][o.symbol]
    dur = time() - start_time
    print(f'cleaned {len(expired)} in {dur:.03f} seconds')
      
  def flush(self):
    self.cleanup()
    it = 0
    start_time = time()
    for obj in self.dirty_objects:
      it += 1
      if obj.is_expired():
        self.purge(obj)
      else:
        self.store(obj)
    self.fil.flush()
    self.dirty_objects = set()
    dur = time() - start_time
    # print(f'flush done {it} items {dur:.2f}')
  
  def defrag(self):
    nm = self.fil.name
    self.fil.close()
    os.rename(nm, nm + '.bak')
    self.fil = open(nm, 'ab+')
    for t in self.data:
      for o in self.all(t):
        o.file_offset = None
        self.store(o)