#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#include <math.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <algorithm>
#include <string>
#include <queue>
#include <vector>

#include "log.h"
#include "metacube2.h"
#include "state.pb.h"
#include "stream.h"
#include "util.h"

using namespace std;

Stream::Stream(const string &url,
               size_t backlog_size,
               uint64_t prebuffering_bytes,
               Encoding encoding,
               Encoding src_encoding,
               unsigned hls_frag_duration,
               size_t hls_backlog_margin,
               const std::string &allow_origin)
	: url(url),
	  encoding(encoding),
	  src_encoding(src_encoding),
	  allow_origin(allow_origin),
	  data_fd(make_tempfile("")),
	  backlog_size(backlog_size),
	  prebuffering_bytes(prebuffering_bytes),
	  hls_frag_duration(hls_frag_duration),
	  hls_backlog_margin(hls_backlog_margin)
{
	if (data_fd == -1) {
		exit(1);
	}
}

Stream::~Stream()
{
	if (data_fd != -1) {
		safe_close(data_fd);
	}
}

Stream::Stream(const StreamProto &serialized, int data_fd)
	: url(serialized.url()),
	  unavailable(serialized.unavailable()),
	  http_header(serialized.http_header()),
	  stream_header(serialized.stream_header()),
	  encoding(Stream::STREAM_ENCODING_RAW),  // Will be changed later.
	  data_fd(data_fd),
	  backlog_size(serialized.backlog_size()),
	  bytes_received(serialized.bytes_received()),
	  first_fragment_index(serialized.first_fragment_index()),
	  discontinuity_counter(serialized.discontinuity_counter())
{
	if (data_fd == -1) {
		exit(1);
	}

	// Set the close-on-exec parameter back on the backlog fd.
	fcntl(data_fd, F_SETFD, FD_CLOEXEC);

	for (ssize_t point : serialized.suitable_starting_point()) {
		if (point == -1) {
			// Can happen when upgrading from before 1.1.3,
			// where this was an optional field with -1 signifying
			// "no such point".
			continue;
		}
		suitable_starting_points.push_back(point);
	}

	for (const FragmentStartProto &fragment : serialized.fragment()) {
		fragments.push_back(FragmentStart { size_t(fragment.byte_position()), fragment.pts(), fragment.begins_header() });
	}
}

StreamProto Stream::serialize()
{
	StreamProto serialized;
	serialized.set_unavailable(unavailable);
	serialized.set_http_header(http_header);
	serialized.set_stream_header(stream_header);
	serialized.add_data_fds(data_fd);
	serialized.set_backlog_size(backlog_size);
	serialized.set_bytes_received(bytes_received);
	for (size_t point : suitable_starting_points) {
		serialized.add_suitable_starting_point(point);
	}
	for (const FragmentStart &fragment : fragments) {
		FragmentStartProto *proto = serialized.add_fragment();
		proto->set_byte_position(fragment.byte_position);
		proto->set_pts(fragment.pts);
		proto->set_begins_header(fragment.begins_header);
	}
	serialized.set_first_fragment_index(first_fragment_index);
	serialized.set_discontinuity_counter(discontinuity_counter);

	// Unset the close-on-exec flag for the backlog fd.
	// (This can't leak into a child, since there's only one thread left.)
	fcntl(data_fd, F_SETFD, 0);

	serialized.set_url(url);
	data_fd = -1;
	return serialized;
}
	
void Stream::set_backlog_size(size_t new_size)
{
	if (backlog_size == new_size) {
		return;
	}

	string existing_data;
	if (!read_tempfile_and_close(data_fd, &existing_data)) {
		exit(1);
	}

	// Unwrap the data so it's no longer circular.
	if (bytes_received <= backlog_size) {
		existing_data.resize(bytes_received);
	} else {
		size_t pos = bytes_received % backlog_size;
		existing_data = existing_data.substr(pos, string::npos) +
			existing_data.substr(0, pos);
	}

	// See if we need to discard data.
	if (new_size < existing_data.size()) {
		size_t to_discard = existing_data.size() - new_size;
		existing_data = existing_data.substr(to_discard, string::npos);
	}

	// Create a new, empty data file.
	data_fd = make_tempfile("");
	if (data_fd == -1) {
		exit(1);
	}
	backlog_size = new_size;

	// Now cheat a bit by rewinding, and adding all the old data back.
	bytes_received -= existing_data.size();
	DataElement data_element;
	data_element.data.iov_base = const_cast<char *>(existing_data.data());
	data_element.data.iov_len = existing_data.size();
	data_element.metacube_flags = 0;  // Ignored by add_data_raw().

	vector<DataElement> data_elements;
	data_elements.push_back(data_element);
	add_data_raw(data_elements);
	remove_obsolete_starting_points();
}

void Stream::set_header(const std::string &new_http_header, const std::string &new_stream_header)
{
	unavailable = false;
	http_header = new_http_header;
	if (new_stream_header == stream_header) {
		return;
	}

	// We cannot start at any of the older starting points anymore,
	// since they'd get the wrong header for the stream (not to mention
	// that a changed header probably means the stream restarted,
	// which means any client starting on the old one would probably
	// stop playing properly at the change point). Next block
	// should be a suitable starting point (if not, something is
	// pretty strange), so it will fill up again soon enough.
	suitable_starting_points.clear();

	// HLS, on the other hand, can deal with discontinuities and multiple
	// headers. At least in theory (client support varies wildly).
	if (!fragments.empty()) {
		// Commit the old header to the backlog, so that we can serve it
		// for all the old fragments for as long as they exist.
		if (!stream_header.empty()) {
			// End the current fragment and make a new one for the header.
			fragments.push_back(Stream::FragmentStart { bytes_received, 0.0, true });
			process_queued_data();
			Stream::DataElement elem;
			elem.data.iov_base = (char *)stream_header.data();
			elem.data.iov_len = stream_header.size();
			add_data_raw({ elem });
			remove_obsolete_starting_points();

			// The discontinuity counter will be increased when
			// this header goes out of the backlog.
		}
		clear_hls_playlist_cache();
	}
	stream_header = new_stream_header;
}

void Stream::put_client_to_sleep(Client *client)
{
	sleeping_clients.push_back(client);
}

// Return a new set of iovecs that contains only the first <bytes_wanted> bytes of <data>.
vector<iovec> collect_iovecs(const vector<Stream::DataElement> &data, size_t bytes_wanted)
{
	vector<iovec> ret;
	size_t max_iovecs = min<size_t>(data.size(), IOV_MAX);
	for (size_t i = 0; i < max_iovecs && bytes_wanted > 0; ++i) {
		if (data[i].data.iov_len <= bytes_wanted) {
			// Consume the entire iovec.
			ret.push_back(data[i].data);
			bytes_wanted -= data[i].data.iov_len;
		} else {
			// Take only parts of this iovec.
			iovec iov;
			iov.iov_base = data[i].data.iov_base;
			iov.iov_len = bytes_wanted;
			ret.push_back(iov);
			bytes_wanted = 0;
		}
	}
	return ret;
}

// Return a new set of iovecs that contains all of <data> except the first <bytes_wanted> bytes.
vector<Stream::DataElement> remove_iovecs(const vector<Stream::DataElement> &data, size_t bytes_wanted)
{
	vector<Stream::DataElement> ret;
	size_t i;
	for (i = 0; i < data.size() && bytes_wanted > 0; ++i) {
		if (data[i].data.iov_len <= bytes_wanted) {
			// Consume the entire iovec.
			bytes_wanted -= data[i].data.iov_len;
		} else {
			// Take only parts of this iovec.
			Stream::DataElement data_element;
			data_element.data.iov_base = reinterpret_cast<char *>(data[i].data.iov_base) + bytes_wanted;
			data_element.data.iov_len = data[i].data.iov_len - bytes_wanted;
			data_element.metacube_flags = METACUBE_FLAGS_NOT_SUITABLE_FOR_STREAM_START;
			data_element.pts = RationalPTS();
			ret.push_back(data_element);
			bytes_wanted = 0;
		}
	}

	// Add the rest of the iovecs unchanged.
	ret.insert(ret.end(), data.begin() + i, data.end());
	return ret;
}

void Stream::add_data_raw(const vector<DataElement> &orig_data)
{
	vector<DataElement> data = orig_data;
	while (!data.empty()) {
		size_t pos = bytes_received % backlog_size;

		// Collect as many iovecs as we can before we hit the point
		// where the circular buffer wraps around.
		vector<iovec> to_write = collect_iovecs(data, backlog_size - pos);
		ssize_t ret;
		do {
			ret = pwritev(data_fd, to_write.data(), to_write.size(), pos);
		} while (ret == -1 && errno == EINTR);

		if (ret == -1) {
			log_perror("pwritev");
			// Dazed and confused, but trying to continue...
			return;
		}
		bytes_received += ret;

		// Remove the data that was actually written from the set of iovecs.
		data = remove_iovecs(data, ret);
	}
}

void Stream::remove_obsolete_starting_points()
{
	// We could do a binary search here (std::lower_bound), but it seems
	// overkill for removing what's probably only a few points.
	while (!suitable_starting_points.empty() &&
	       bytes_received - suitable_starting_points[0] > backlog_size) {
		suitable_starting_points.pop_front();
	}
	assert(backlog_size >= hls_backlog_margin);
	while (!fragments.empty() &&
	       bytes_received - fragments[0].byte_position > (backlog_size - hls_backlog_margin)) {
		if (fragments[0].begins_header) {
			++discontinuity_counter;
		} else {
			++first_fragment_index;
		}
		fragments.pop_front();
		clear_hls_playlist_cache();
	}
}

void Stream::add_data_deferred(const char *data, size_t bytes, uint16_t metacube_flags, const RationalPTS &pts)
{
	// For regular output, we don't want to send the client twice
	// (it's already sent out together with the HTTP header).
	// However, for Metacube output, we need to send it so that
	// the Cubemap instance in the other end has a chance to update it.
	// It may come twice in its stream, but Cubemap doesn't care.
	if (encoding == Stream::STREAM_ENCODING_RAW &&
	    (metacube_flags & METACUBE_FLAGS_HEADER) != 0) {
		return;
	}

	lock_guard<mutex> lock(queued_data_mutex);

	DataElement data_element;
	data_element.metacube_flags = metacube_flags;
	data_element.pts = pts;

	if (encoding == Stream::STREAM_ENCODING_METACUBE) {
		// Construct a PTS metadata block. (We'll avoid sending it out
		// if we don't have a valid PTS.)
		metacube2_pts_packet pts_packet;
		pts_packet.type = htobe64(METACUBE_METADATA_TYPE_NEXT_BLOCK_PTS);
		pts_packet.pts = htobe64(pts.pts);
		pts_packet.timebase_num = htobe64(pts.timebase_num);
		pts_packet.timebase_den = htobe64(pts.timebase_den);

		metacube2_block_header pts_hdr;
		memcpy(pts_hdr.sync, METACUBE2_SYNC, sizeof(pts_hdr.sync));
		pts_hdr.size = htonl(sizeof(pts_packet));
		pts_hdr.flags = htons(METACUBE_FLAGS_METADATA);
		pts_hdr.csum = htons(metacube2_compute_crc(&pts_hdr));

		// Add a Metacube block header before the data.
		metacube2_block_header hdr;
		memcpy(hdr.sync, METACUBE2_SYNC, sizeof(hdr.sync));
		hdr.size = htonl(bytes);
		hdr.flags = htons(metacube_flags);
		hdr.csum = htons(metacube2_compute_crc(&hdr));

		data_element.data.iov_len = bytes + sizeof(hdr);
		if (pts.timebase_num != 0) {
			data_element.data.iov_len += sizeof(pts_hdr) + sizeof(pts_packet);
		}
		data_element.data.iov_base = new char[data_element.data.iov_len];

		char *ptr = reinterpret_cast<char *>(data_element.data.iov_base);
		if (pts.timebase_num != 0) {
			memcpy(ptr, &pts_hdr, sizeof(pts_hdr));
			ptr += sizeof(pts_hdr);
			memcpy(ptr, &pts_packet, sizeof(pts_packet));
			ptr += sizeof(pts_packet);
		}

		memcpy(ptr, &hdr, sizeof(hdr));
		ptr += sizeof(hdr);
		memcpy(ptr, data, bytes);

		queued_data.push_back(data_element);
	} else if (encoding == Stream::STREAM_ENCODING_RAW) {
		// Just add the data itself.
		data_element.data.iov_base = new char[bytes];
		memcpy(data_element.data.iov_base, data, bytes);
		data_element.data.iov_len = bytes;

		queued_data.push_back(data_element);
	} else {
		assert(false);
	}
}

void Stream::process_queued_data()
{
	vector<DataElement> queued_data_copy;

	// Hold the lock for as short as possible, since add_data_raw() can possibly
	// write to disk, which might disturb the input thread.
	{
		lock_guard<mutex> lock(queued_data_mutex);
		if (queued_data.empty()) {
			return;
		}

		swap(queued_data, queued_data_copy);
	}

	// Add suitable starting points for the stream, if the queued data
	// contains such starting points. Note that we drop starting points
	// if they're less than 10 kB apart, so that we don't get a huge
	// amount of them for e.g. each and every MPEG-TS 188-byte cell.
	// The 10 kB value is somewhat arbitrary, but at least it should make
	// the RAM cost of saving the position ~0.1% (or less) of the actual
	// data, and 10 kB is a very fine granularity in most streams.
	static const int minimum_start_point_distance = 10240;
	size_t byte_position = bytes_received;
	bool need_hls_clear = false;
	for (const DataElement &elem : queued_data_copy) {
		if ((elem.metacube_flags & METACUBE_FLAGS_NOT_SUITABLE_FOR_STREAM_START) == 0) {
			size_t num_points = suitable_starting_points.size();
			if (num_points >= 2 &&
			    suitable_starting_points[num_points - 1] - suitable_starting_points[num_points - 2] < minimum_start_point_distance) {
				// p[n-1] - p[n-2] < 10 kB, so drop p[n-1].
				suitable_starting_points.pop_back();
			}
			suitable_starting_points.push_back(byte_position);

			if (elem.pts.timebase_num != 0) {
				need_hls_clear |= add_fragment_boundary(byte_position, elem.pts);
			}
		}
		byte_position += elem.data.iov_len;
	}
	if (need_hls_clear) {
		clear_hls_playlist_cache();
	}

	add_data_raw(queued_data_copy);
	remove_obsolete_starting_points();
	for (const DataElement &elem : queued_data_copy) {
		char *data = reinterpret_cast<char *>(elem.data.iov_base);
		delete[] data;
	}

	// We have more data, so wake up all clients.
	if (to_process.empty()) {
		swap(sleeping_clients, to_process);
	} else {
		to_process.insert(to_process.end(), sleeping_clients.begin(), sleeping_clients.end());
		sleeping_clients.clear();
	}
}

bool Stream::add_fragment_boundary(size_t byte_position, const RationalPTS &pts)
{
	double pts_double = double(pts.pts) * pts.timebase_den / pts.timebase_num;

	if (fragments.size() <= 1 ||
	    fragments[fragments.size() - 1].begins_header ||
	    fragments[fragments.size() - 2].begins_header) {
		// Just starting up, so try to establish the first in-progress fragment.
		fragments.push_back(FragmentStart{ byte_position, pts_double, false });
		return false;
	}

	// Keep extending the in-progress fragment as long as we do not
	// exceed the target duration by more than half a second
	// (RFC 8216 4.3.3.1) and we get closer to the target by doing so.
	// Note that in particular, this means we'll always extend
	// as long as we don't exceed the target duration.
	double current_duration = pts_double - fragments[fragments.size() - 1].pts;
	double candidate_duration = pts_double - fragments[fragments.size() - 2].pts;
	if (lrintf(candidate_duration) <= hls_frag_duration &&
	    fabs(candidate_duration - hls_frag_duration) < fabs(current_duration - hls_frag_duration)) {
		fragments.back() = FragmentStart{ byte_position, pts_double, false };
		return false;
	} else {
		// Extending the in-progress fragment would make it too long,
		// so finalize it and start a new in-progress fragment.
		fragments.push_back(FragmentStart{ byte_position, pts_double, false });
		return true;
	}
}

void Stream::clear_hls_playlist_cache()
{
	hls_playlist_http10.reset();
	hls_playlist_http11_close.reset();
	hls_playlist_http11_persistent.reset();
}

shared_ptr<const string> Stream::generate_hls_playlist(bool http_11, bool close_after_response)
{
	char buf[256];
	snprintf(buf, sizeof(buf),
		"#EXTM3U\r\n"
		"#EXT-X-VERSION:7\r\n"
		"#EXT-X-TARGETDURATION:%u\r\n"
		"#EXT-X-MEDIA-SEQUENCE:%" PRIu64 "\r\n"
		"#EXT-X-DISCONTINUITY-SEQUENCE:%" PRIu64 "\r\n",
		hls_frag_duration,
		first_fragment_index,
		discontinuity_counter);

	string playlist = buf;

	if (fragments.size() >= 3) {
		bool printed_header_for_this_group = false;
		bool printed_first_header = false;
		for (size_t i = 0; i < fragments.size() - 2; ++i) {
			char buf[256];

			if (fragments[i].begins_header) {
				// End of this group. (We've already printed the header
				// as part of the previous group.)
				printed_header_for_this_group = false;
				continue;
			}
			if (!printed_header_for_this_group) {
				// Look forward until we find the header for this group (if any).
				for (size_t j = i + 1; j < fragments.size() - 1; ++j) {
					if (fragments[j].begins_header) {
						if (printed_first_header) {
							playlist += "#EXT-X-DISCONTINUITY\r\n";
						}
						snprintf(buf, sizeof(buf),
							"#EXT-X-MAP:URI=\"%s?frag=%" PRIu64 "-%" PRIu64 "\"\r\n",
							url.c_str(), fragments[j].byte_position,
							fragments[j + 1].byte_position);
						playlist += buf;
						printed_first_header = true;
						printed_header_for_this_group = true;
						break;
					}
				}

				if (!printed_header_for_this_group && !stream_header.empty()) {
					if (printed_first_header) {
						playlist += "#EXT-X-DISCONTINUITY\r\n";
					}
					snprintf(buf, sizeof(buf), "#EXT-X-MAP:URI=\"%s?frag=header\"\r\n", url.c_str());
					playlist += buf;
				}

				// Even if we didn't find anything, we don't want to search again for each fragment.
				printed_first_header = true;
				printed_header_for_this_group = true;
			}

			if (fragments[i + 1].begins_header) {
				// Since we only have start pts for each block and not duration,
				// we have no idea how long this fragment is; the encoder restarted
				// before it got to output the next pts. However, it's likely
				// to be very short, so instead of trying to guess, we just skip it.
				continue;
			}

			snprintf(buf, sizeof(buf), "#EXTINF:%f,\r\n%s?frag=%" PRIu64 "-%" PRIu64 "\r\n",
				fragments[i + 1].pts - fragments[i].pts,
				url.c_str(),
				fragments[i].byte_position,
				fragments[i + 1].byte_position);
			playlist += buf;
		}
	}

	string response;
	if (http_11) {
		response = "HTTP/1.1 200 OK\r\n";
		if (close_after_response) {
			response.append("Connection: close\r\n");
		}
	} else {
		assert(close_after_response);
		response = "HTTP/1.0 200 OK\r\n";
	}
	snprintf(buf, sizeof(buf), "Content-Length: %zu\r\n", playlist.size());
	response.append(buf);
	response.append("Content-Type: application/x-mpegURL\r\n");
	if (!allow_origin.empty()) {
		response.append("Access-Control-Allow-Origin: ");
		response.append(allow_origin);
		response.append("\r\n");
	}
	response.append("\r\n");
	response.append(move(playlist));

	return shared_ptr<const string>(new string(move(response)));
}