#include "parser.hpp"
#include <cstdlib>

using namespace stela;

static inline auto in_range(char ch, char begin, char end) -> bool
{
    return ch >= begin && ch <= end;
}

static inline auto whitespace_char(char ch) -> bool
{
    return ch == ' ' or ch == '\t' or ch == '\n';
}

static inline auto id_start_char(char ch) -> bool
{
    return in_range(ch, 'a', 'z') or in_range(ch, 'A', 'Z') or ch == '_';
}

static inline auto id_char(char ch) -> bool
{
    return in_range(ch, 'a', 'z') or in_range(ch, 'A', 'Z')
        or in_range(ch, '0', '1') or ch == '_';
}

auto Lexer::next() -> Token
{
    auto pos = this->pos();
    if (done()) {
        return token(TokenType::Eof, pos);
    }
    char ch = current();
    if (whitespace_char(ch)) {
        step();
        return next();
    }
    if (id_start_char(ch)) {
        std::string value;
        value.push_back(ch);
        step();
        while (not done() and id_char(current())) {
            value.push_back(current());
            step();
        }
        if (this->keyword_map.contains(value)) {
            return token(this->keyword_map[value], pos);
        }
        size_t id = this->symbol_values.size();
        this->symbol_values.push_back(value);
        return Token { TokenType::Id, pos, id };
    }
    if (in_range(ch, '1', '9')) {
        std::string value;
        value.push_back(ch);
        step();
        while (not done() and in_range(ch, '0', '9')) {
            value.push_back(current());
            step();
        }
        int64_t int_value = std::strtoll(value.c_str(), nullptr, 10);
        size_t id = this->symbol_values.size();
        this->int_values.push_back(int_value);
        return Token { TokenType::Id, pos, id };
    }
    if (ch == '0') {
        step();
        int64_t int_value = 0;
        size_t id = this->symbol_values.size();
        this->int_values.push_back(int_value);
        return Token { TokenType::Id, pos, id };
    }
    if (ch == '"') {
        // TODO string
    }
    if (ch == '#') {
        while (not done() and current() != '\n') {
            step();
        }
        return next();
    }
    if (ch == '/') {
        step();
        if (current() == '/') {
            while (not done() and current() != '\n') {
                step();
            }
            return next();
        }
        return error_token(pos, "'/' not implemented");
    }
    if (ch == '-') {
        step();
        if (not done() and current() == '>') {
            step();
            return token(TokenType::MinusLt, pos);
        }
        return token(TokenType::Minus, pos);
    }
    if (ch == ':') {
        step();
        if (current() == ':') {
            step();
            return token(TokenType::ColonColon, pos);
        }
        return token(TokenType::Colon, pos);
    }
    switch (ch) {
        case '(':
            return single_token(TokenType::LParen, pos);
        case ')':
            return single_token(TokenType::RParen, pos);
        case '{':
            return single_token(TokenType::LBrace, pos);
        case '}':
            return single_token(TokenType::RBrace, pos);
        case '[':
            return single_token(TokenType::LBracket, pos);
        case ']':
            return single_token(TokenType::RBracket, pos);
        case '.':
            return single_token(TokenType::Dot, pos);
        case ',':
            return single_token(TokenType::Comma, pos);
        case ';':
            return single_token(TokenType::Semicolon, pos);
    }
    step();
    return error_token(pos, "unrecognized character");
}

auto Lexer::populate_keyword_map()
{
    this->keyword_map["error"] = TokenType::Error;
    this->keyword_map["eof"] = TokenType::Eof;
    this->keyword_map["if"] = TokenType::If;
    this->keyword_map["else"] = TokenType::Else;
    this->keyword_map["return"] = TokenType::Return;
    this->keyword_map["public"] = TokenType::Public;
    this->keyword_map["private"] = TokenType::Private;
    this->keyword_map["class"] = TokenType::Class;
    this->keyword_map["derivable"] = TokenType::Derivable;
    this->keyword_map["derives"] = TokenType::Derives;
    this->keyword_map["enumeration"] = TokenType::Enumeration;
    this->keyword_map["associate"] = TokenType::Associate;
    this->keyword_map["attribute"] = TokenType::Attribute;
    this->keyword_map["operation"] = TokenType::Operation;
    this->keyword_map["state_machine"] = TokenType::StateMachine;
    this->keyword_map["transition"] = TokenType::Transition;
    this->keyword_map["initial"] = TokenType::Initial;
    this->keyword_map["final"] = TokenType::Final;
    this->keyword_map["entry"] = TokenType::Entry;
    this->keyword_map["exit"] = TokenType::Exit;
}