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

#include <stdexcept>

namespace NVL::Environment {
	Environment ENVIRONMENT;
	Variable::Variable() : type(Type::Nil), length(0) { }
	Variable::Variable(Type t) : type(t), length(0) {
		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 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, u32 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<String>(other.value) == std::get<String>(value);
		default:
			return false;
		}
	}

	void Environment::enter(const String& name, Variable p) {
		if (!env.emplace(name, p).second)
			throw std::runtime_error("Redefinition of symbol in environment");
	}

	void Environment::enter(std::initializer_list<std::pair<String, Variable>> p) {
		for (auto& i : p)
			enter(i.first, i.second);
	}

	void Environment::set(const 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 String& name) {
		return env.at(name);
	}

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

	Variable Eval(const Parse::Object& obj) {
		switch (obj.type) {
		case Parse::Type::Symbol:
			return ENVIRONMENT.get(std::get<String>(obj.value));
		case Parse::Type::Number:
			return Variable(std::get<Number>(obj.value));
		case Parse::Type::String:
			return Variable(std::get<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{};

		Variable f = Eval(c[0]);
		u32 i = 1;
		while (i < c.size()) {
			args.push_back(Eval(c[i++]));
		}
		if (f.length != -1 && f.length != i - 1) throw std::runtime_error("Function arity mismatch");
		return std::get<std::function<Variable(std::vector<Variable>)>>(f.value)(args);
	}

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

	// Check MatchMarkup for more information
	MarkupString UnpackMarkupVariable(const std::vector<Variable>& v) {		
		MarkupString ms{};
		for (const Variable& segment : v) {
			const auto& pair =  std::get<std::vector<Variable>>(segment.value);
			const String s = std::get<String>(pair[0].value); 

			std::vector<std::pair<String, std::vector<String>>> efs;
			for (const Variable& combination : std::get<std::vector<Variable>>(pair[1].value)) {
				if (combination.type == Type::String) {
					const String ef = std::get<String>(combination.value);
					efs.push_back({ ef, {} });
				}
				else if (combination.type == Type::Array) {
					const std::vector<Variable>& ef_t = std::get<std::vector<Variable>>(combination.value);
					const String& ef = std::get<String>(ef_t[0].value);
					const std::vector<Variable>& args = std::get<std::vector<Variable>>(ef_t[1].value);
					std::vector<String> ss{};
					for (const auto& s : args) { ss.push_back(std::get<String>(s.value)); }
					efs.push_back({ ef, ss });
				}
			}
			ms.segments.push_back({ s, efs });
		}
		return ms;
	}

	size_t MarkupString::length() const { // you do realize this memoization fails if we change the var
		if (mem_length == -1) {
			size_t r = 0;
			for (const auto& s : segments)
				r += s.str.length();
			return r;
		}
		else
			return mem_length;
	}

	MarkupString MarkupString::substr(size_t i) const {
		size_t r = 0;
		MarkupString res;
		for (const auto& s : segments) {
			size_t last_r = r;
			r += s.str.length();
			if (r <= i)
				res.segments.push_back(s);
			else {
				auto copy = s;
				copy.str = copy.str.substr(0, i - last_r);
				res.segments.push_back(copy);
				break;
			}
		}
		return res;
	}
}