/*
 * .============.
 * // M A K E / \
 * // C++ DEV / \
 * // E A S Y / \/ \
 * ++ ----------. \/\ .
 * \\ \ \ /\ /
 * \\ \ \ /
 * \\ \ \ /
 * -============'
 *
 * Copyright (c) 2023 Hevake and contributors, all rights reserved.
 *
 * This file is part of cpp-tbox (https://github.com/cpp-main/cpp-tbox)
 * Use of this source code is governed by MIT license that can be found
 * in the LICENSE file in the root of the source tree. All contributing
 * project authors may be found in the CONTRIBUTORS.md file in the root
 * of the source tree.
 */
#include "state_machine.h"

#include <vector>
#include <map>
#include <stdexcept>
#include <algorithm>

#include <tbox/base/log.h>
#include <tbox/base/assert.h>
#include <tbox/base/json.hpp>

namespace tbox {
namespace flow {

using namespace std;

class StateMachine::Impl {
 public:
 ~Impl();

 public:
 bool newState(StateID state_id,
 const ActionFunc &enter_action,
 const ActionFunc &exit_action,
 const std::string &lable);

 bool addRoute(StateID from_state_id,
 EventID event_id,
 StateID to_state_id,
 const GuardFunc &guard,
 const ActionFunc &action,
 const std::string &label);

 bool addEvent(StateID state_id,
 EventID event_id,
 const EventFunc &action);

 void setInitState(StateID init_state_id) { init_state_id_ = init_state_id; }

 bool setSubStateMachine(StateID state_id, StateMachine *wp_sub_sm);
 void setStateChangedCallback(const StateChangedCallback &cb);

 bool start();
 void stop();

 bool run(Event event);

 StateID currentState() const;
 StateID lastState() const;
 StateID nextState() const;

 bool isTerminated() const;

 void toJson(Json &js) const;

 private:
 struct Route {
 EventID event_id;
 StateID next_state_id;
 GuardFunc guard;
 ActionFunc action;
 std::string label;
 };

 struct State {
 StateID id;
 ActionFunc enter_action;
 ActionFunc exit_action;
 std::string label;
 StateMachine::Impl *sub_sm; //! 子状态机
 vector<Route> routes; //! 转换路由
 map<EventID, EventFunc> events; //! 内部事件
 EventFunc default_event;
 };

 State* findState(StateID state_id) const;

 StateID init_state_id_ = 1; //! 初始状态

 State *last_state_ = nullptr; //! 上一个状态指针
 State *curr_state_ = nullptr; //! 当前状态指针
 State *next_state_ = nullptr; //! 下一个状态指针
 map<StateID, State*> states_; //! 状态对象表

 StateChangedCallback state_changed_cb_;

 static State _term_state_; //! 默认终止状态对象

 int cb_level_ = 0;
};

StateMachine::StateMachine() : impl_(new Impl)
{ }

StateMachine::~StateMachine()
{
 delete impl_;
}

bool StateMachine::newState(StateID state_id, const ActionFunc &enter_action, const ActionFunc &exit_action, const std::string &label)
{
 return impl_->newState(state_id, enter_action, exit_action, label);
}

bool StateMachine::addRoute(StateID from_state_id, EventID event_id, StateID to_state_id,
 const GuardFunc &guard, const ActionFunc &action, const std::string &label)
{
 return impl_->addRoute(from_state_id, event_id, to_state_id, guard, action, label);
}

bool StateMachine::addEvent(StateID state_id, EventID event_id, const EventFunc &action)
{
 return impl_->addEvent(state_id, event_id, action);
}

void StateMachine::setInitState(StateID init_state_id)
{
 impl_->setInitState(init_state_id);
}

bool StateMachine::setSubStateMachine(StateID state_id, StateMachine *wp_sub_sm)
{
 return impl_->setSubStateMachine(state_id, wp_sub_sm);
}

void StateMachine::setStateChangedCallback(const StateChangedCallback &cb)
{
 impl_->setStateChangedCallback(cb);
}

bool StateMachine::start()
{
 return impl_->start();
}

void StateMachine::stop()
{
 impl_->stop();
}

bool StateMachine::restart()
{
 impl_->stop();
 return impl_->start();
}

bool StateMachine::run(Event event)
{
 return impl_->run(event);
}

StateMachine::StateID StateMachine::currentState() const
{
 return impl_->currentState();
}

StateMachine::StateID StateMachine::lastState() const
{
 return impl_->lastState();
}

StateMachine::StateID StateMachine::nextState() const
{
 return impl_->nextState();
}

bool StateMachine::isTerminated() const
{
 return impl_->isTerminated();
}

void StateMachine::toJson(Json &js) const
{
 return impl_->toJson(js);
}

///////////////////////

StateMachine::Impl::State StateMachine::Impl::_term_state_ = { 0, nullptr, nullptr, "Term", nullptr, { } };

StateMachine::Impl::~Impl()
{
 TBOX_ASSERT(cb_level_ == 0);

 for (auto &item : states_)
 delete item.second;

 states_.clear();
}

bool StateMachine::Impl::newState(StateID state_id,
 const ActionFunc &enter_action,
 const ActionFunc &exit_action,
 const std::string &label)
{
 //! 已存在的状态不能再创建了
 if (states_.find(state_id) != states_.end()) {
 LogWarn("state %u exist", state_id);
 return false;
 }

 auto new_state = new State { state_id, enter_action, exit_action, label, nullptr, { } };
 states_[state_id] = new_state;

 return true;
}

bool StateMachine::Impl::addRoute(StateID from_state_id,
 EventID event_id,
 StateID to_state_id,
 const GuardFunc &guard,
 const ActionFunc &action,
 const std::string &label)
{
 //! 要求 from_state_id 必须是已存在的状态
 auto from_state = findState(from_state_id);
 if (from_state == nullptr) {
 LogWarn("from_state %d not exist", from_state_id);
 return false;
 }

 //! 如果 to_state_id 为是终止状态,那么这个状态必须是已存在的
 if (to_state_id != 0 && findState(to_state_id) == nullptr) {
 LogWarn("to_state %d not exist", to_state_id);
 return false;
 }

 from_state->routes.emplace_back(Route{ event_id, to_state_id, guard, action, label });
 return true;
}

bool StateMachine::Impl::addEvent(StateID state_id,
 EventID event_id,
 const EventFunc &action)
{
 if (action == nullptr) {
 LogWarn("action is nullptr", state_id);
 return false;
 }

 //! 要求 state_id 必须是已存在的状态
 auto state = findState(state_id);
 if (state == nullptr) {
 LogWarn("state %d not exist", state_id);
 return false;
 }

 if (event_id != 0)
 state->events[event_id] = action;
 else
 state->default_event = action;

 return true;
}

bool StateMachine::Impl::setSubStateMachine(StateID state_id, StateMachine *wp_sub_sm)
{
 auto state = findState(state_id);
 if (state == nullptr) {
 LogWarn("state:%u not exist", state_id);
 return false;
 }

 state->sub_sm = wp_sub_sm->impl_;
 return true;
}

void StateMachine::Impl::setStateChangedCallback(const StateChangedCallback &cb)
{
 state_changed_cb_ = cb;
}

bool StateMachine::Impl::start()
{
 if (curr_state_ != nullptr) {
 LogWarn("it's already started");
 return false;
 }

 if (cb_level_ != 0) {
 LogWarn("recursion invoke");
 return false;
 }

 auto init_state = findState(init_state_id_);
 if (init_state == nullptr) {
 LogWarn("init state %u not exist", init_state_id_);
 return false;
 }

 curr_state_ = init_state;

 ++cb_level_;
 if (init_state->enter_action)
 init_state->enter_action(Event());
 --cb_level_;

 //! 如果有子状态机,在启动子状态机
 if (curr_state_->sub_sm != nullptr)
 curr_state_->sub_sm->start();

 return true;
}

void StateMachine::Impl::stop()
{
 if (curr_state_ == nullptr)
 return;

 if (cb_level_ != 0) {
 LogWarn("recursion invoke");
 return;
 }

 ++cb_level_;
 if (curr_state_->exit_action)
 curr_state_->exit_action(Event());
 --cb_level_;

 curr_state_ = nullptr;
}

bool StateMachine::Impl::run(Event event)
{
 if (curr_state_ == nullptr) {
 LogWarn("need start first");
 return false;
 }

 if (cb_level_ != 0) {
 LogWarn("recursion invoke");
 return false;
 }

 //! 如果有子状态机,则给子状态机处理
 if (curr_state_->sub_sm != nullptr) {
 bool ret = curr_state_->sub_sm->run(event);
 if (!curr_state_->sub_sm->isTerminated())
 return ret;
 curr_state_->sub_sm->stop();
 }

 StateID next_state_id = -1;
 ActionFunc route_action;

 //! 检查事件,并执行
 ++cb_level_;
 auto event_iter = curr_state_->events.find(event.id);
 if (event_iter != curr_state_->events.end())
 next_state_id = event_iter->second(event);
 else if (curr_state_->default_event)
 next_state_id = curr_state_->default_event(event);
 --cb_level_;

 if (next_state_id < 0) {
 //! 找出可行的路径
 ++cb_level_;
 auto route_iter = std::find_if(curr_state_->routes.begin(), curr_state_->routes.end(),
 [event] (const Route &item) -> bool {
 if (item.event_id != 0 && item.event_id != event.id)
 return false;
 if (item.guard != nullptr && !item.guard(event))
 return false;
 return true;
 }
 );
 --cb_level_;

 //! 如果没有跳转则直接退出
 if (route_iter == curr_state_->routes.end())
 return false;

 //! 以下是有跳转的情况
 next_state_id = route_iter->next_state_id;
 route_action = route_iter->action;
 }

 next_state_ = findState(next_state_id);
 if (next_state_ == nullptr) {
 if (next_state_id == 0) {
 next_state_ = &_term_state_;
 } else {
 LogErr("Should not happen");
 return false;
 }
 }

 ++cb_level_;
 if (curr_state_->exit_action)
 curr_state_->exit_action(event);

 last_state_ = curr_state_;
 curr_state_ = nullptr;

 if (route_action)
 route_action(event);

 curr_state_ = next_state_;
 next_state_ = nullptr;

 if (curr_state_->enter_action)
 curr_state_->enter_action(event);

 if (state_changed_cb_)
 state_changed_cb_(last_state_->id, curr_state_->id, event);

 //! 如果新的状态有子状态机,则启动子状态机并将事件交给子状态机处理
 if (curr_state_->sub_sm != nullptr) {
 curr_state_->sub_sm->start();
 curr_state_->sub_sm->run(event);
 }
 --cb_level_;

 return true;
}

StateMachine::StateID StateMachine::Impl::currentState() const
{
 if (curr_state_ != nullptr)
 return curr_state_->id;
 return -1;
}

StateMachine::StateID StateMachine::Impl::lastState() const
{
 if (last_state_ != nullptr)
 return last_state_->id;
 return -1;
}

StateMachine::StateID StateMachine::Impl::nextState() const
{
 if (next_state_ != nullptr)
 return next_state_->id;
 return -1;
}

bool StateMachine::Impl::isTerminated() const
{
 if (curr_state_ == nullptr) {
 LogWarn("need start first");
 return false;
 }

 return curr_state_->id == 0;
}

StateMachine::Impl::State* StateMachine::Impl::findState(StateID state_id) const
{
 try {
 return states_.at(state_id);
 } catch (const out_of_range &e) {
 return nullptr;
 }
}

void StateMachine::Impl::toJson(Json &js) const
{
 js["init_state"] = init_state_id_;
 js["term_state"] = 0;
 if (curr_state_ != nullptr)
 js["curr_state"] = curr_state_->id;

 auto &js_state_array = js["states"];
 for (auto &item : states_) {
 auto state = item.second;
 Json js_state;
 js_state["id"] = state->id;
 js_state["label"] = state->label;

 if (state->sub_sm != nullptr)
 state->sub_sm->toJson(js_state["sub_sm"]);

 auto &js_route_array = js_state["routes"];
 for (auto &route : state->routes) {
 Json js_route;
 js_route["event_id"] = route.event_id;
 js_route["next_state_id"] = route.next_state_id;
 js_route["label"] = route.label;
 js_route_array.push_back(std::move(js_route));
 }

 auto &js_event_array = js_state["events"];
 for (auto &item : state->events)
 js_event_array.push_back(item.first);

 js_state_array.push_back(std::move(js_state));
 }
}

}
}