#include <cassert>
#include <cstdio>

#include "mm.hh"
#include "phys_mm.hh"
#include "pagecache.hh"

PageCache::PageCache(int maxPages) : maxPages_(maxPages), curPages_(0) {
}

PageCache::~PageCache() {
  for(auto& devEntry : allocs_) { // For each known device
    for(auto& allocEntry : devEntry.second) {
      freeAlloc(allocEntry);
    }
  }
}

PageCache::Handle PageCache::readAllocate(IBlockDevice& dev, unsigned pos, unsigned count) {
  ScopedLock<Mutex> lock(mutex_);

  _allocInfo *alloc = searchAlloc(&dev, pos, count);
  if(!alloc) {
    _allocInfo newAlloc;
    buildAlloc(newAlloc, count);
 
    newAlloc.dev = &dev;
    newAlloc.start = pos;
 
    try {
      dev.read(newAlloc.start, newAlloc.virtMem, newAlloc.len);
      allocs_[&dev].push_back(newAlloc);
      alloc = &allocs_[&dev].back();
    } catch(...) {
      freeAlloc(newAlloc);
      throw;
    }
    curPages_ += count;
  }

  return Handle(alloc, (pos - alloc->start));
}

PageCache::Handle PageCache::writeAllocate(IBlockDevice& dev, unsigned pos, unsigned count) {
  ScopedLock<Mutex> lock(mutex_);

  _allocInfo *alloc = searchAlloc(&dev, pos, count);
  if(!alloc) {
    _allocInfo newAlloc;
    buildAlloc(newAlloc, count);
 
    newAlloc.dev = &dev;
    newAlloc.start = pos;
 
    try {
      allocs_[&dev].push_back(newAlloc);
      alloc = &allocs_[&dev].back();
    } catch(...) {
      freeAlloc(newAlloc);
      throw;
    }
    curPages_ += count;
  }

  return Handle(alloc, (pos - alloc->start));
}

void PageCache::eject(int lengthHint) {
  ScopedLock<Mutex> lock(mutex_);
  _eject(lengthHint);
}


void PageCache::freeAlloc(_allocInfo& alloc) {
  assert(!alloc.refs);
  if(alloc.dirty && alloc.dev)
    alloc.dev->write(alloc.start, alloc.virtMem, alloc.len);
  
  if(alloc.virtMem) {
    cortexa8::unmap_pages((uintptr_t)alloc.virtMem, alloc.len);
    mm::virtfree_pc((uintptr_t)alloc.virtMem);
  }
  if(alloc.physMem)
    phys_mm::free(alloc.physMem);
}

void PageCache::buildAlloc(_allocInfo& alloc, unsigned len) {
  if((maxPages_ > 0) && (curPages_ + len > (unsigned)maxPages_)) {
    _eject(curPages_+len-maxPages_);
    if(curPages_ + len > (unsigned)maxPages_)
      throw ex::bad_alloc{};
  }

  alloc.dirty = false;
  alloc.len = len;
  alloc.dev = nullptr;
  alloc.physMem = 0;
  alloc.virtMem = nullptr;
  alloc.refs = 0;

  bool retry = true;
  while(true) {
    try {
      if(!alloc.physMem)
	alloc.physMem = phys_mm::alloc(len);
      if(!alloc.virtMem)
	alloc.virtMem = (char*)mm::virtalloc_pc(len);
      cortexa8::map_pages((uintptr_t)alloc.virtMem, alloc.physMem, len);
      break;
    } catch(ex::bad_alloc &ex) {
      if(retry) {
	_eject(len);
	retry = false;
      } else {
	freeAlloc(alloc);
	throw;
      }
    }
  }
}
  
PageCache::_allocInfo* PageCache::searchAlloc(IBlockDevice* dev, unsigned start, unsigned len) {
  auto it = allocs_.find(dev);
  if(it == allocs_.end())
    return nullptr;

  for(auto& allocEntry : it->second) {
    if((allocEntry.start <= start) &&
       ((allocEntry.start + allocEntry.len) >= (start + len)))
      return &allocEntry;
  }

  return nullptr;
}

void PageCache::_eject(int lengthHint) {
  printf("NYI: PageCache::_eject\n");
}



PageCache::Handle::Handle(_allocInfo* alloc, int ofs) : alloc_(alloc), ofs_(ofs) {
  ++alloc_->refs;
}

PageCache::Handle::Handle(Handle const& copy) : alloc_(copy.alloc_), ofs_(copy.ofs_) {
  ++alloc_->refs;
}

PageCache::Handle& PageCache::Handle::operator=(Handle const& copy) {
  if(alloc_)
    --alloc_->refs;
  
  alloc_ = copy.alloc_;
  ofs_ = copy.ofs_;

  if(alloc_)
    ++alloc_->refs;

  return *this;
}


PageCache::Handle::~Handle() {
  --alloc_->refs;
}