#pragma once
#include <variant>
#include <memory>
#include <vector>
#include <sstream>
#include <functional>
#include <cassert>
#include <iostream>
#include <iomanip>
#include <unordered_map>
#include <cstdlib>
#include <cmath>

namespace lispy {
	class cons;
	class function;

	struct empty {};
	struct cons_start{};
	struct cons_end{};

	struct atom {
		int value;
	};

	struct sp_coords {
		bool is_relative = false;
		size_t x, y;
	};

	struct sp_range {
		bool is_relative = false;
		size_t x, y;
		size_t width, height;
	};

	using lvalue = std::variant<int64_t, double, std::string, atom, empty, std::shared_ptr<cons>, sp_coords, sp_range, std::shared_ptr<function>>;

	using token = std::variant<cons_start, cons_end, lvalue>;

	struct context {
		std::unordered_map<std::string, int> atoms;
		int last_atom = 0;
		bool error_crash = false;
		bool print_parse_results = false;
		std::unordered_map<int, std::shared_ptr<function>> function_table;
		std::unordered_map<int, lvalue> variable_table;

		int get_atom(const std::string& key)
		{
			if(atoms.count(key)) {
				return atoms[key];
			} else {
				return atoms[key] = ++last_atom;
			}
		}
	};

	class cons {
	public:
		lvalue self = empty{};
		std::shared_ptr<cons> other{};

		cons()
		{
			self = empty{};
			other = std::shared_ptr<cons>{};
		}

		cons(lvalue first) 
		: self(first)
		, other()
		{ }

		cons(std::vector<lvalue> data)
		{ 
			if(data.size() == 0) {
				self = empty{};
				other = std::shared_ptr<cons>{};
			} else if(data.size() >= 1) {
				self = data[0];
				for(auto it = data.begin()+1; it != data.end(); ++it)
					this->append(*it);
			}
		}

		cons(const cons& oth) 
		: self(oth.self)
		, other(oth.other ? std::make_shared<cons>(*(oth.other)) : nullptr)
		{}
		void operator=(const cons& oth)
		{
			self = oth.self;
			if(oth.other) {
				other = std::make_shared<cons>(*oth.other);
			} else {
				other = std::shared_ptr<cons>{};
			}
		}

		cons(cons&& oth) 
		: self(oth.self)
		, other(oth.other ? std::move(std::make_shared<cons>(*(oth.other))) : std::shared_ptr<cons>{})
		{}

		void append(lvalue value)
		{
			if(!other) {
				other = std::make_shared<cons>(value);
			} else {
				other->append(value);
			}
		}
	};

	class function {
	public:
	 	virtual lvalue operator() (const std::shared_ptr<cons> arguments, lispy::context& ctx) = 0;
	 	virtual ~function(){};
	};

	inline char hexdigit(char v)
	{
		if(v >= '0' && v<='9') {
			return v - '0';
		} else if(v >= 'a' && v <= 'f') {
			return 10 + v - 'a';
		} else if(v >= 'A' && v <= 'F') {
			return 10 + v - 'A';
		}
		return -1;
	}

	inline std::string escape(std::string_view v)
	{
		auto it = v.begin();
		std::stringstream stream;
		stream<<'"';
		while(it != v.end())
		{
			switch(*it)
			{
				case '"':
				{
					stream << "\\\"";
				}
				break;
				case '\n':
				{
					stream << "\\n";
				}
				break;
				case '\t':
				{
					stream << "\\t";
				}
				break;
				case '\v':
				{
					stream << "\\v";
				}
				break;
				case '\a':
				{
					stream << "\\a";
				}
				break;
				default:
					stream << *it;
			}
			++it;
		}
		stream<<'"';
		return stream.str();
	}

	inline void print_visitor(std::ostream& stream, const lvalue& value, const context& ctx) {
		std::visit([&](auto arg) {
            using T = std::decay_t<decltype(arg)>;
            if constexpr (std::is_same_v<T, int64_t>) {
                stream << arg;
			} else if constexpr (std::is_same_v<T, double>) {
                stream << arg;
			} else if constexpr (std::is_same_v<T, empty>) {
                stream << "()";
			} else if constexpr (std::is_same_v<T, std::shared_ptr<function>>) {
                stream << "#func"<<&*arg;
			} else if constexpr (std::is_same_v<T, std::string>) {
                stream << escape(arg);
            } else if constexpr (std::is_same_v<T, std::shared_ptr<cons>>) {
				stream << "(";
				bool is_first = true;
				cons p = *arg;
				do{
					
					if(!is_first)
					{
						p = *p.other;
					}
					print_visitor(stream, p.self, ctx);
					if(p.other)
					{
						stream << " ";
					}
					is_first = false;
				} while(p.other);
				stream << ")";
			}
            else if constexpr (std::is_same_v<T, sp_coords>){
				stream << (arg.is_relative ? "$[" : "@[") << arg.x << "," << arg.y << "]";
			} else if constexpr (std::is_same_v<T, sp_range>){
				stream << (arg.is_relative ? "$[" : "@[") << arg.x << "," << arg.y << "," << arg.width << "," << arg.height << "]";
			} else if constexpr (std::is_same_v<T, atom>) {
				for(auto& v : ctx.atoms)
				{
					if(v.second == arg.value)
					{
						stream << v.first;
						return;
					}
				}
				assert(false);
			} else {
                std::cerr << typeid(T).name() << " detected in print_visitor ?" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
        }, value);
	}

	inline void print_types_visitor(std::ostream& stream, const lvalue& value, const context& ctx) {
		std::visit([&](auto arg) {
            using T = std::decay_t<decltype(arg)>;
            if constexpr (std::is_same_v<T, int64_t>) {
                stream << "integer";
			} else if constexpr (std::is_same_v<T, double>) {
                stream << "double";
			} else if constexpr (std::is_same_v<T, empty>) {
                stream << "nil";
			} else if constexpr (std::is_same_v<T, std::shared_ptr<function>>) {
                stream << "function";
			} else if constexpr (std::is_same_v<T, std::string>) {
                stream << "string";
            } else if constexpr (std::is_same_v<T, std::shared_ptr<cons>>){
				stream << "(";
				bool is_first = true;
				cons p = *arg;
				do{
					
					if(!is_first)
					{
						p = *p.other;
					}
					print_types_visitor(stream, p.self, ctx);
					if(p.other)
					{
						stream << " ";
					}
					is_first = false;
				} while(p.other);
				stream << ")";
			} else if constexpr (std::is_same_v<T, sp_coords>){
                stream << "coords";
			} else if constexpr (std::is_same_v<T, sp_range>){
                stream << "range";
			} else if constexpr (std::is_same_v<T, atom>) {
                stream << "atom";
			} else {
                std::cerr << typeid(T).name() << " detected in print_types_visitor ?" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
        }, value);
	}

	inline std::pair<lvalue, std::string_view> parse_string(std::string_view data)
	{
		auto it = data.begin();
		assert(*it == '\"');
		++it;
		std::stringstream value(std::string(data.begin(), data.end()));
		std::string ret;
		value >> std::quoted(ret);
		return std::make_pair<lvalue, std::string_view>(ret, std::string_view{data.begin(), (size_t)value.rdbuf()->in_avail()});
	}

	inline std::pair<lvalue, std::string_view> parse_atom(std::string_view data, context& ctx)
	{
		assert(!iswspace(data[0]));
		size_t idx = 1;
		while(!iswspace(data[idx]))
		{
			idx++;
		}
		atom v;
		v.value = ctx.get_atom(std::string(data.begin(), data.begin()+idx));
		return std::make_pair(lvalue{v}, std::string_view{data.begin(), idx});
	}

	inline std::pair<lvalue, std::string_view> parse_number(std::string_view data)
	{
		char* end_f;
		char* end_d;
		double try_f = strtod (data.data(), &end_f);
		int err_f = errno;
		int64_t try_d = strtoll(data.data(), &end_d, 10);
		int err_d = errno;

		if(err_d == ERANGE)
		{
			return std::make_pair(lvalue{(double)try_f}, std::string_view{data.begin(), (size_t)(end_f-data.data())});
		}

		if(try_f != std::trunc(try_f))
		{
			return std::make_pair(lvalue{(double)try_f}, std::string_view{data.begin(), (size_t)(end_f-data.data())});
		}

		return std::make_pair(lvalue{int64_t(try_d)}, std::string_view{data.begin(), (size_t)(end_f-data.data())});
	}

	inline std::pair<size_t,sp_coords> get_coords_from_id(const std::string_view id) {
		size_t x = 0;
		size_t y = 0;
		auto c = id.begin();
		while(*c >= 'A' && *c <= 'Z')
		{
			x += *c-'A'+1;
			x *= 26;
			c++;
		}
		x /= 26;
		while(*c >= '0' && *c <= '9') 
		{
			y += *c-'0';
			y *= 10;
			c++;
		}
		y /= 10;
		sp_coords ret;
		ret.x = x;
		ret.y = y;
		return std::make_pair((size_t)(c-id.begin()) ,ret);
	}

	inline std::pair<lvalue, std::string_view> parse_selector(std::string_view data)
	{
		auto it = data.begin();
		auto is_rel = *it == '$';
		++it;
		auto a = get_coords_from_id(std::string_view{it, data.size()-1});
		a.second.is_relative = is_rel;
		it += a.first;
		if(*it == ':')
		{
			auto b = get_coords_from_id(std::string_view{++it, data.size()-1});
			it += b.first;
			sp_range ret;
			a.second.is_relative = is_rel;
			ret.x = a.second.x;
			ret.y = a.second.y;
			ret.width = b.second.x;
			ret.height = b.second.y;
			return std::make_pair(lvalue{ret}, std::string_view{data.begin(), (size_t)(it - data.begin())});
		} else {
			return std::make_pair(lvalue{a.second}, std::string_view{data.begin(), (size_t)(it - data.begin())});
		}
	}

	inline size_t find_matching(const std::basic_string_view<token>& data, const size_t idx)
	{
		size_t try_idx = idx;
		int mass = 1;

		do{
			try_idx++;
			std::visit([&](auto arg) {
				using T = std::decay_t<decltype(arg)>;
				if constexpr (std::is_same_v<T, cons_start>) {
					++mass;
				} else if constexpr (std::is_same_v<T, cons_end>) {
					--mass;
				} else {}
			}, data[try_idx]);
		} while(mass != 0 && try_idx < data.size());

		if(try_idx<data.size())
		{
			return try_idx;
		}
		return idx;
	}

	inline std::pair<size_t, lvalue> parse(const std::basic_string_view<token>& data, context& ctx)
	{
		auto ret = std::make_shared<cons>();
		size_t sz = 0;

		if(data.size() == 0)
		{
			return std::make_pair(0,(lvalue)empty{});
		}

		size_t skip = 0;

		size_t idx = 0;

		while(idx < data.size())
		{
			if(skip)
			{
				skip--;
				++idx;
				continue;
			}

			std::visit([&](const auto& arg) {
				using T = std::decay_t<decltype(arg)>;
				if constexpr (std::is_same_v<T, cons_start>) {
					auto matching = find_matching(data, idx);
					auto res = parse(std::basic_string_view<token>{data.begin()+idx+1, matching-idx-1}, ctx);
					ret->append(res.second);
					skip = matching - idx;
					++sz;
				} else if constexpr (std::is_same_v<T, cons_end>) {
					std::cerr << typeid(T).name() << " mismatched parenthesis" << std::endl;
				} else if constexpr (std::is_same_v<T, lvalue>) {
					ret->append(arg);
					++sz;
				} else {
					std::cerr << typeid(T).name() << " cat in the parser ?" << std::endl;
					if(ctx.error_crash)
					{
						std::exit(-1);
					}
				}
			}, data[idx]);
			++idx;
		}
		return std::make_pair(sz, (lvalue)(std::make_shared<cons>(*ret->other)));
	}

	inline std::vector<token> lex(const std::string_view data, context& ctx)
	{
		std::vector<token> ret;

		auto it = data.begin();
		bool is_done = false;
		do{
			if (it == data.end()) {
				is_done = true;
			} else if(isdigit(*it) || (*it == '-' && isdigit(*(it+1)))) {
				auto value = parse_number(std::string_view{it, (size_t)(data.end() - it)});
				ret.push_back(value.first);
				it += value.second.size();
			} else if(*it == '\"') {
				auto value = parse_string(std::string_view{it, (size_t)(data.end() - it)});
				ret.push_back(value.first);
				size_t forward_jump = std::string_view{it, (size_t)(data.end() - it)}.size()-value.second.size();
				it += forward_jump;
			} else if (*it == '(') {
				ret.push_back(cons_start{});
				++it;
			} else if (*it == ')') {
				ret.push_back(cons_end{});
				++it;
			} else if (iswspace(*it)) {
				++it;
			} else if (*it == '$' || *it == '@') {
				auto value = parse_selector(std::string_view{it, (size_t)(data.end() - it)});
				ret.push_back(value.first);
				it += value.second.size()+1;
			} else {
				auto value = parse_atom(std::string_view{it, (size_t)(data.end() - it)}, ctx);
				ret.push_back(value.first);
				it += value.second.size();
			}
		}while(!is_done);

		return ret;
	}

	inline lvalue eval(lvalue& data, context& ctx)
	{
		lvalue ret = empty{};
		std::visit([&](auto& arg) {
			using T = std::decay_t<decltype(arg)>;
			if constexpr (std::is_same_v<T, std::shared_ptr<cons>>) {
				auto it = arg;
				auto evaluated = std::make_shared<cons>();
				auto iterated = evaluated;

				do{
					iterated->self = eval(it->self, ctx);
					if(it->other)
					{
						iterated->other = std::make_shared<cons>();
						iterated = iterated->other;
					}
					it = it->other;
				} while(it);
				std::visit([&](auto arg) {
					using T = std::decay_t<decltype(arg)>;
					if constexpr (std::is_same_v<T, std::shared_ptr<function>>) {
						ret = (*arg)(evaluated->other, ctx);
					} else {
						ret = evaluated;
					}
				}, evaluated->self);
			} else if constexpr (std::is_same_v<T, atom>) {
				if(ctx.function_table.count(arg.value))
				{
					ret = ctx.function_table[arg.value];
				} else if (ctx.variable_table.count(arg.value)) {
					ret = ctx.variable_table[arg.value];
				} else {
					ret = arg;
				}
			} else {
				ret = arg;
			}
		}, data);
		return ret;
	}

	inline lvalue eval(const std::string_view& data, context& ctx)
	{
		auto n = lex(data, ctx);
		auto p = parse(std::basic_string_view<token>(n.data(), n.size()), ctx);
		if(ctx.print_parse_results)
		{
			print_types_visitor(std::cerr, p.second, ctx);
			std::cerr << std::endl;
			print_visitor(std::cerr, p.second, ctx);
			std::cerr << std::endl;
		}
		return eval(p.second, ctx);
	}
}

namespace lispy_math {

	int64_t next_as_int(std::shared_ptr<lispy::cons>& arguments, lispy::context& ctx) {
		int64_t ret = 0;
		if(!arguments)
		{
			std::cerr << "no argument provided, number expected" << std::endl;
			if(ctx.error_crash)
			{
				std::exit(-1);
			}
			return ret;
		}
		std::visit([&](auto arg) {
			using T = std::decay_t<decltype(arg)>;
			if constexpr (std::is_same_v<T, int64_t>) {
				ret = arg;
			} else if constexpr (std::is_same_v<T, double>) {
				ret = arg;
			} else {
				std::cerr << "bad argument provided, number expected" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
		}, arguments->self);
		arguments = arguments->other;
		return ret;
	}

	double next_as_floating(std::shared_ptr<lispy::cons>& arguments, lispy::context& ctx) {
		double ret = 0;
		if(!arguments)
		{
			std::cerr << "no argument provided, number expected" << std::endl;
			if(ctx.error_crash)
			{
				std::exit(-1);
			}
			return ret;
		}
		std::visit([&](auto arg) {
			using T = std::decay_t<decltype(arg)>;
			if constexpr (std::is_same_v<T, int64_t>) {
				ret = arg;
			} else if constexpr (std::is_same_v<T, double>) {
				ret = arg;
			} else {
				std::cerr << "bad argument provided, number expected" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
		}, arguments->self);
		arguments = arguments->other;
		return ret;
	}

	namespace integer_functions {
		class plus : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			int64_t a = next_as_int(p, ctx);
			int64_t b = next_as_int(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a+b;
		}};
		class minus : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			int64_t a = next_as_int(p, ctx);

			if(!p) {
				return -a;
			}

			int64_t b = next_as_int(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 1 or 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a-b;
		}};
		class product : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			int64_t a = next_as_int(p, ctx);
			int64_t b = next_as_int(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a*b;
		}};
		class divide : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			int64_t a = next_as_int(p, ctx);
			int64_t b = next_as_int(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a/b;
		}};
		class remainder : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			int64_t a = next_as_int(p, ctx);
			int64_t b = next_as_int(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a%b;
		}};
	};

	namespace float_functions {
		class plus : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			double a = next_as_floating(p, ctx);
			double b = next_as_floating(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a+b;
		}};
		class minus : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			double a = next_as_floating(p, ctx);

			if(!p) {
				return -a;
			}

			double b = next_as_floating(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 1 or 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a-b;
		}};
		class product : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			double a = next_as_floating(p, ctx);
			double b = next_as_floating(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a*b;
		}};
		class divide : lispy::function {virtual lispy::lvalue operator() (const std::shared_ptr<lispy::cons> arguments, lispy::context& ctx) {
			auto p = arguments;
			double a = next_as_floating(p, ctx);
			double b = next_as_floating(p, ctx);

			if(p) 
			{
				std::cerr << "expected arity of 2 but more arguments provided" << std::endl;
				if(ctx.error_crash)
				{
					std::exit(-1);
				}
			}
			return a/b;
		}};
	};
		
	inline void add_integer_functions(lispy::context& ctx) {
		using func_ptr = std::shared_ptr<lispy::function>;

		ctx.function_table[ctx.get_atom("+")] = func_ptr{(lispy::function*)new integer_functions::plus()};
		ctx.function_table[ctx.get_atom("-")] = func_ptr{(lispy::function*)new integer_functions::minus()};
		ctx.function_table[ctx.get_atom("*")] = func_ptr{(lispy::function*)new integer_functions::product()};
		ctx.function_table[ctx.get_atom("/")] = func_ptr{(lispy::function*)new integer_functions::divide()};
		ctx.function_table[ctx.get_atom("%")] = func_ptr{(lispy::function*)new integer_functions::remainder()};
	}
		
	inline void add_floatingp_functions(lispy::context& ctx) {
		using func_ptr = std::shared_ptr<lispy::function>;

		ctx.function_table[ctx.get_atom("+.")] = func_ptr{(lispy::function*)new float_functions::plus()};
		ctx.function_table[ctx.get_atom("-.")] = func_ptr{(lispy::function*)new float_functions::minus()};
		ctx.function_table[ctx.get_atom("*.")] = func_ptr{(lispy::function*)new float_functions::product()};
		ctx.function_table[ctx.get_atom("/.")] = func_ptr{(lispy::function*)new float_functions::divide()};
	}
}