// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.

#include "rooms.h"

using namespace ircd::m;
using namespace ircd;

ircd::log::log
join_log
{
	"matrix.join"
};

resource::response
post__join(client &client,
           const resource::request &request,
           const room::id &room_id)
{
	const string_view &third_party_signed
	{
		unquote(request["third_party_signed"])
	};

	const string_view &server_name
	{
		unquote(request["server_name"])
	};

	const m::room room
	{
		room_id
	};

	m::join(room, request.user_id);

	return resource::response
	{
		client, json::members
		{
			{ "room_id", room_id }
		}
	};
}

event::id::buf
IRCD_MODULE_EXPORT
ircd::m::join(const room &room,
              const id::user &user_id)
{
	if(!exists(room))
	{
		const auto &room_id(room.room_id);
		return m::room::bootstrap(room_id, user_id, room_id.host()); //TODO: host
	}

	json::iov event;
	json::iov content;
	const json::iov::push push[]
	{
		{ event,    { "type",        "m.room.member"  }},
		{ event,    { "sender",      user_id          }},
		{ event,    { "state_key",   user_id          }},
		{ content,  { "membership",  "join"           }},
	};

	const m::user user{user_id};
	const m::user::profile profile{user};

	char displayname_buf[256];
	const string_view displayname
	{
		profile.get(displayname_buf, "displayname")
	};

	char avatar_url_buf[256];
	const string_view avatar_url
	{
		profile.get(avatar_url_buf, "avatar_url")
	};

	const json::iov::add _displayname
	{
		content, !empty(displayname),
		{
			"displayname", [&displayname]() -> json::value
			{
				return displayname;
			}
		}
	};

	const json::iov::add _avatar_url
	{
		content, !empty(avatar_url),
		{
			"avatar_url", [&avatar_url]() -> json::value
			{
				return avatar_url;
			}
		}
	};

	return commit(room, event, content);
}

event::id::buf
IRCD_MODULE_EXPORT
ircd::m::join(const m::room::alias &room_alias,
              const m::user::id &user_id)
{
	const room::id::buf room_id
	{
		m::room_id(room_alias)
	};

	if(!exists(room_id))
		return m::room::bootstrap(room_id, user_id, room_alias.host());

	const m::room room
	{
		room_id
	};

	return m::join(room, user_id);
}

//
// bootstrap
//

static event::id::buf
bootstrap_make_join(const string_view &host,
                    const m::room::id &,
                    const m::user::id &);

static std::tuple<json::object, unique_buffer<mutable_buffer>>
bootstrap_send_join(const string_view &host,
                    const m::room::id &,
                    const m::event::id &,
                    const json::object &event);

static void
bootstrap_eval_lazy_chain(const json::array &auth_chain);

static void
bootstrap_eval_auth_chain(const json::array &auth_chain);

static void
bootstrap_eval_state(const json::array &state);

static void
bootstrap_backfill(const string_view &host,
                   const m::room::id &,
                   const m::event::id &);

conf::item<seconds>
make_join_timeout
{
	{ "name",     "ircd.client.rooms.join.make_join.timeout" },
	{ "default",  15L                                        },
};

conf::item<seconds>
send_join_timeout
{
	{ "name",     "ircd.client.rooms.join.send_join.timeout" },
	{ "default",  90L  /* spinappse */                       },
};

conf::item<seconds>
backfill_timeout
{
	{ "name",     "ircd.client.rooms.join.backfill.timeout" },
	{ "default",  15L                                       },
};

conf::item<size_t>
backfill_limit
{
	{ "name",         "ircd.client.rooms.join.backfill.limit" },
	{ "default",      64L                                     },
	{ "description",

	R"(
	The number of events to request on initial backfill. Specapse may limit
	this to 50, but it also may not. Either way, a good choice is enough to
	fill a client's timeline quickly with a little headroom.
	)"}
};

conf::item<bool>
backfill_first
{
	{ "name",         "ircd.client.rooms.join.backfill.first" },
	{ "default",      true                                    },
	{ "description",

	R"(
	During the room join bootstrap process, this controls whether backfilling
	recent timeline events occurs before processing the room state. If true,
	user experience may be improved because their client's timeline is
	immediately populated with recent messages. Otherwise, the backfill will be
	delayed until after all state events have been processed first. Setting
	this to false is safer, as some clients may be confused by timeline events
	which are missing related state events. Note that fundamental state events
	for the room are still processed first regardless of this setting. Also
	known as the Hackfill optimization.
	)"}
};

conf::item<bool>
lazychain_enable
{
	{ "name",         "ircd.client.rooms.join.lazychain.enable" },
	{ "default",      false                                     },
	{ "description",

	R"(
	During the room join bootstrap process, this controls whether the
	auth_chain in the response is only selectively processed. This is a
	safe optimization that allows the bootstrap to progress to the next
	phase. The skipped events are eventually processed during the state
	evaluation phase.
	)"}
};

event::id::buf
IRCD_MODULE_EXPORT
ircd::m::room::bootstrap(const m::room::id &room_id,
                         const m::user::id &user_id,
                         const string_view &host)
{
	log::debug
	{
		join_log, "join bootstrap starting in %s for %s to '%s'",
		string_view{room_id},
		string_view{user_id},
		host
	};

	const auto event_id
	{
		bootstrap_make_join(host, room_id, user_id)
	};

	assert(event_id);
	bootstrap(event_id, host); // asynchronous; returns quickly
	return event_id;
}

void
IRCD_MODULE_EXPORT
ircd::m::room::bootstrap(const m::event::id &event_id,
                         const string_view &host)
try
{
	const m::event::fetch event{event_id};
	assert(event.source);
	context
	{
		"roomjoin", 128_KiB,
		context::POST | context::DETACH,
		[host(std::string(host)), event(std::string(event.source))]
		{
			bootstrap(m::event{event}, host);
		}
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "join bootstrap for %s to %s :%s",
		string_view{event_id},
		string(host),
		e.what()
	};
}

void
IRCD_MODULE_EXPORT
ircd::m::room::bootstrap(const m::event &event,
                         const string_view &host)
try
{
	const m::event::id &event_id
	{
		event.event_id
	};

	const m::room::id &room_id
	{
		at<"room_id"_>(event)
	};

	const m::user::id &user_id
	{
		at<"sender"_>(event)
	};

	const m::room room
	{
		room_id, event_id
	};

	log::info
	{
		join_log, "join bootstrap sending in %s for %s at %s to '%s'",
		string_view{room_id},
		string_view{user_id},
		string_view{event_id},
		host
	};

	assert(event.source);
	const auto &[response, buf]
	{
		bootstrap_send_join(host, room_id, event_id, event.source)
	};

	const json::array &auth_chain
	{
		response["auth_chain"]
	};

	const json::array &state
	{
		response["state"]
	};

	log::info
	{
		join_log, "join bootstrap joined to %s for %s at %s to '%s' state:%zu auth_chain:%zu",
		string_view{room_id},
		string_view{user_id},
		string_view{event_id},
		host,
		state.size(),
		auth_chain.size(),
	};

	if(lazychain_enable)
		bootstrap_eval_lazy_chain(auth_chain);
	else
		bootstrap_eval_auth_chain(auth_chain);

	if(backfill_first)
	{
		bootstrap_backfill(host, room_id, event_id);
		bootstrap_eval_state(state);
	} else {
		bootstrap_eval_state(state);
		bootstrap_backfill(host, room_id, event_id);
	}

	// After we just received and processed all of this state with only a
	// recent backfill our system doesn't know if state events which are
	// unreferenced are simply referenced by events we just don't have. They
	// will all be added to the room::head and each future event we transmit
	// to the room will drain that list little by little. But the cost of all
	// these references is too high. We take the easy route here and simply
	// clear the head of every event except our own join event.
	const size_t num_reset
	{
		m::room::head::reset(room)
	};

	log::info
	{
		join_log, "join bootstrap joined to %s for %s at %s reset:%zu complete",
		string_view{room_id},
		string_view{user_id},
		string_view{event_id},
		num_reset,
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "join bootstrap for %s to %s :%s",
		string_view{event.event_id},
		string(host),
		e.what()
	};
}

void
bootstrap_backfill(const string_view &host,
                   const m::room::id &room_id,
                   const m::event::id &event_id)
try
{
	const unique_buffer<mutable_buffer> buf
	{
		16_KiB // headers in and out
	};

	m::v1::backfill::opts opts{host};
	opts.dynamic = true;
	opts.event_id = event_id;
	opts.limit = size_t(backfill_limit);
	m::v1::backfill request
	{
		room_id, buf, std::move(opts)
	};

	request.wait(seconds(backfill_timeout));

	const auto code
	{
		request.get()
	};

	const json::object &response
	{
		request.in.content
	};

	const json::array &pdus
	{
		response["pdus"]
	};

	log::info
	{
		join_log, "join bootstrap processing backfill for %s from %s at %s events:%zu",
		string_view{room_id},
		host,
		string_view{event_id},
		pdus.size(),
	};

	m::vm::opts vmopts;
	vmopts.nothrows = -1;
	vmopts.fetch_state_check = false;
	vmopts.fetch_prev_check = false;
	vmopts.infolog_accept = false;
	m::vm::eval
	{
		pdus, vmopts
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "join bootstrap %s backfill @ %s from %s :%s",
		string_view{room_id},
		string_view{event_id},
		string(host),
		e.what(),
	};
}

void
bootstrap_eval_state(const json::array &state)
try
{
	m::vm::opts opts;
	opts.nothrows = -1;
	opts.fetch_prev_check = false;
	opts.fetch_state_check = false;
	opts.infolog_accept = false;
	m::vm::eval
	{
		state, opts
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "join bootstrap eval state :%s", e.what(),
	};
}

void
bootstrap_eval_auth_chain(const json::array &auth_chain)
try
{
	m::vm::opts opts;
	opts.infolog_accept = true;
	opts.fetch = false;
	m::vm::eval
	{
		auth_chain, opts
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "join bootstrap eval auth_chain :%s", e.what(),
	};

	throw;
}

void
bootstrap_eval_lazy_chain(const json::array &auth_chain)
{
	m::vm::opts opts;
	opts.infolog_accept = true;
	opts.fetch = false;

	// Parse and sort the auth_chain first so we don't have to keep scanning
	// the JSON to do the various operations that follow.
	std::vector<m::event> events(begin(auth_chain), end(auth_chain));
	std::sort(begin(events), end(events));

	// When we selectively evaluate the auth_chain below we may need to feed
	// the vm certain member events first to avoid complications; this
	// subroutine will find them.
	const auto find_member{[&events]
	(const m::user::id &user_id, const int64_t &depth)
	{
		const auto it(std::find_if(rbegin(events), rend(events), [&user_id, &depth]
		(const m::event &event)
		{
			return json::get<"depth"_>(event) < depth &&
			       json::get<"type"_>(event) == "m.room.member" &&
			       json::get<"state_key"_>(event) == user_id;
		}));

		if(unlikely(it == rend(events)))
			throw m::NOT_FOUND
			{
				"No m.room.member event for %s found in auth chain.",
				string_view{user_id}
			};

		return *it;
	}};

	for(const auto &event : events)
	{
		// Skip all events which aren't power events. We don't need them
		// here yet. They can wait until state evaluation later.
		if(!m::event::auth::is_power_event(event))
			continue;

		// Find the member event for the sender of this power event so the
		// system is aware of their identity first; this isn't done for the
		// create event because the vm expects that first regardless.
		if(json::get<"type"_>(event) != "m.room.create")
		{
			const auto &member_event
			{
				find_member(at<"sender"_>(event), at<"depth"_>(event))
			};

			m::vm::eval
			{
				member_event, opts
			};
		}

		m::vm::eval
		{
			event, opts
		};
	}
}

std::tuple<json::object, unique_buffer<mutable_buffer>>
bootstrap_send_join(const string_view &host,
                    const m::room::id &room_id,
                    const m::event::id &event_id,
                    const json::object &event)
try
{
	const unique_buffer<mutable_buffer> buf
	{
		16_KiB // headers in and out
	};

	m::v1::send_join::opts opts{host};
	opts.dynamic = true;
	m::v1::send_join send_join
	{
		room_id, event_id, event, buf, std::move(opts)
	};

	send_join.wait(seconds(send_join_timeout));

	const auto send_join_code
	{
		send_join.get()
	};

	const json::array &send_join_response
	{
		send_join
	};

	const uint more_send_join_code
	{
		send_join_response.at<uint>(0)
	};

	const json::object &send_join_response_data
	{
		send_join_response[1]
	};

	assert(!!send_join.in.dynamic);
	return
	{
		send_join_response_data,
		std::move(send_join.in.dynamic)
	};
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "Bootstrap %s @ %s send_join to %s :%s",
		string_view{room_id},
		string_view{event_id},
		string(host),
		e.what(),
	};

	throw;
}

event::id::buf
bootstrap_make_join(const string_view &host,
                    const m::room::id &room_id,
                    const m::user::id &user_id)
try
{
	const unique_buffer<mutable_buffer> buf
	{
		16_KiB // headers in and out
	};

	m::v1::make_join::opts opts{host};
	m::v1::make_join request
	{
		room_id, user_id, buf, std::move(opts)
	};

	request.wait(seconds(make_join_timeout));
	const auto code
	{
		request.get()
	};

	const json::object &response
	{
		request.in.content
	};

	const json::string &room_version
	{
		response.get("room_version", "1")
	};

	const json::object &proto
	{
		response.at("event")
	};

	const json::array &auth_events
	{
		proto.get("auth_events")
    };

	const json::array &prev_events
	{
		proto.get("prev_events")
    };

	json::iov event;
	json::iov content;
	const json::iov::push push[]
	{
		{ event,    { "type",          "m.room.member"           }},
		{ event,    { "sender",        user_id                   }},
		{ event,    { "state_key",     user_id                   }},
		{ content,  { "membership",    "join"                    }},
		{ event,    { "prev_events",   prev_events               }},
		{ event,    { "auth_events",   auth_events               }},
		{ event,    { "prev_state",    "[]"                      }},
		{ event,    { "depth",         proto.get<long>("depth")  }},
		{ event,    { "room_id",       room_id                   }},
	};

	const m::user user{user_id};
	const m::user::profile profile{user};

	char displayname_buf[256];
	const string_view displayname
	{
		profile.get(displayname_buf, "displayname")
	};

	char avatar_url_buf[256];
	const string_view avatar_url
	{
		profile.get(avatar_url_buf, "avatar_url")
	};

	const json::iov::add _displayname
	{
		content, !empty(displayname),
		{
			"displayname", [&displayname]() -> json::value
			{
				return displayname;
			}
		}
	};

	const json::iov::add _avatar_url
	{
		content, !empty(avatar_url),
		{
			"avatar_url", [&avatar_url]() -> json::value
			{
				return avatar_url;
			}
		}
	};

	m::vm::copts vmopts;
	vmopts.infolog_accept = true;
	vmopts.fetch = false;
	vmopts.eval = false;
	vmopts.room_version = room_version;
	const m::event::id::buf ret{vm::eval
	{
		event, content, vmopts
	}};

	if(unlikely(!ret))
		throw m::UNAVAILABLE
		{
			"Unknown error"
		};

	return ret;
}
catch(const std::exception &e)
{
	log::error
	{
		join_log, "Bootstrap %s for %s make_join to %s :%s",
		string_view{room_id},
		string_view{user_id},
		string(host),
		e.what(),
	};

	throw;
}