#include "Environment.h"
#include "Parser.h"

#include <stdexcept>

namespace NVL::Environment {
	Environment ENVIRONMENT;

	Variable::Variable() {}
	Variable::Variable(Type t) : type(t) {
		if (t != Type::Nil)
			throw std::runtime_error("Cannot create non-nil object with type alone");
	}
	Variable::Variable(const Number& v) : type(Type::Number), value(v), length(1) {}
	Variable::Variable(const std::string& v) : type(Type::String), value(v), length(1) {}
	Variable::Variable(const std::vector<Variable>& v) : type(Type::Array), value(v), length(v.size()) {}
	Variable::Variable(const std::function < Variable(std::vector<Variable>)>& v, int l) : type(Type::Procedure), value(v), length(l) {}

	bool Variable::operator==(const Variable& other) const {
		if (other.type != type)
			return false;
		switch (type) {
		case Type::Number:
			return std::get<Number>(other.value) == std::get<Number>(value);
		case Type::String:
			return std::get<std::string>(other.value) == std::get<std::string>(value);
		default:
			return false;
		}
	}

	void Environment::enter(const std::string& name, Variable p) {
		if (env.find(name) != env.end())
			throw std::runtime_error("Redefinition of symbol in environment");
		env[name] = p;
	}

	void Environment::set(const std::string& name, Variable p) {
		if (env.find(name) == env.end())
			throw std::runtime_error("Attempting to set undefined variable");
		env[name] = p;
	}

	Variable& Environment::get(const std::string& name) {
		return env.at(name);
	}

	bool Environment::exists(const std::string& name) {
		return env.find(name) != env.end();
	}

	Variable Eval(const Parse::Object& obj) {
		switch (obj.type) {
		case Parse::Type::Symbol:
			return std::get<std::string>(obj.value);
		case Parse::Type::Number:
			return Variable(std::get<Number>(obj.value));
		case Parse::Type::String:
			return Variable(std::get<std::string>(obj.value));
		case Parse::Type::Array:
		{
			std::vector<Variable> v{};
			for (const auto& x : std::get<std::vector<Parse::Object>>(obj.value))
				v.push_back(Eval(x));
			return Variable(v);
		}
		case Parse::Type::Subexpression:
		{
			return Apply(std::get<std::vector<Parse::Object>>(obj.value));
		}
		}
	}

	Variable Apply(const Parse::Command& c) {
		std::vector<Variable> args{};
		for (int i = 1; i < c.size(); i++)
			args.push_back(Eval(c[i]));
		return std::get<std::function<Variable(std::vector<Variable>)>>(ENVIRONMENT.get(std::get<std::string>(c[0].value)).value)(args);
	}

	void EvalScene(const Parse::Scene& s) {
		for (const auto& c : s.get())
			Apply(c);
	}
}