#include "block-cache/copier.h"

#include <stdexcept>

using namespace bcache;
using namespace boost;
using namespace std;

//----------------------------------------------------------------

copier::copier(io_engine &engine,
	       string const &src, string const &dest,
	       sector_t block_size, size_t mem)
	: pool_(block_size * 512, mem, PAGE_SIZE),
	  block_size_(block_size),
	  engine_(engine),
	  src_handle_(engine_.open_file(src, io_engine::M_READ_ONLY)),
	  dest_handle_(engine_.open_file(dest, io_engine::M_READ_WRITE)),
	  genkey_count_(0)
{
}

copier::~copier()
{
	engine_.close_file(src_handle_);
	engine_.close_file(dest_handle_);
}

void
copier::issue(copy_op const &op)
{
	void *data;

	while (!(data = pool_.alloc())) {
		wait_();

		// data may still not be present because the wait_ could
		// have completed a read and issued the corresponding
		// write.
	}

	copy_job job(op, data);
	job.op.read_complete = job.op.write_complete = false;
	unsigned key = genkey(); // used as context for the io_engine

	auto r = engine_.issue_io(src_handle_,
				  io_engine::D_READ,
				  to_sector(op.src_b),
				  to_sector(op.src_e),
				  data,
				  key);

	if (r)
		jobs_.insert(make_pair(key, job));

	else
		complete(job);
}

unsigned
copier::nr_pending() const
{
	return jobs_.size() + complete_.size();
}

boost::optional<copy_op>
copier::wait()
{
	if (complete_.empty())
		wait_();

	return wait_complete();
}

boost::optional<copy_op>
copier::wait(unsigned &micro)
{
	if (complete_.empty())
		wait_(micro);
	return wait_complete();
}

bool
copier::pending() const
{
	return !jobs_.empty();
}

boost::optional<copy_op>
copier::wait_complete()
{
	if (complete_.empty()) {
		return optional<copy_op>();

	} else {
		auto op = complete_.front();
		complete_.pop_front();
		return optional<copy_op>(op);
	}
}

void
copier::wait_(unsigned &micro)
{
	optional<io_engine::wait_result> mp;

	if (!pending())
		return;


	bool completed = false;
	while (pending() && !completed) {
		mp = engine_.wait(micro);
		if (mp)
			completed = wait_successful(*mp);

		if (!micro)
			break;
	}
}

void
copier::wait_()
{
	bool completed = false;

	while (pending() && !completed) {
		auto mp = engine_.wait();
		if (mp)
			completed = wait_successful(*mp);
	}
}

bool
copier::wait_successful(io_engine::wait_result const &p)
{
	auto it = jobs_.find(p.second);
	if (it == jobs_.end())
		throw runtime_error("Internal error.  Lost track of copy job.");

	copy_job &j = it->second;
	if (!p.first) {
		// IO was unsuccessful
		complete(j);
		jobs_.erase(it);
		return true;
	}

	// IO was successful
	if (!j.op.read_complete) {
		j.op.read_complete = true;
		if (!engine_.issue_io(dest_handle_,
				      io_engine::D_WRITE,
				      to_sector(j.op.dest_b),
				      to_sector(j.op.dest_b + (j.op.src_e - j.op.src_b)),
				      j.data,
				      it->first)) {
			complete(j);
			jobs_.erase(it);
			return true;
		}
		return false;

	} else {
		j.op.write_complete = true;
		complete(j);
		jobs_.erase(it);
		return true;
	}
}

void
copier::complete(copy_job const &j)
{
	pool_.free(j.data);
	complete_.push_back(j.op);
}

sector_t
copier::to_sector(block_address b) const
{
	return b * block_size_;
}

unsigned
copier::genkey()
{
	return genkey_count_++;
}

//----------------------------------------------------------------