#include "scanner.hh"
#include "token.hh"
#include "error_handler.hh"
#include "object.hh"
#include <vector>

extern ErrorHandler error_handler;

std::vector<Token> Scanner::scan_tokens() {
  while (!is_at_end()) {
    start = current;
    scan_token();
  }

  tokens.push_back(Token(TokenType::EOFILE, "", Object{}, line));
  return tokens;
}

bool Scanner::is_at_end() {
  return current >= code.size();
}

void Scanner::scan_token() {
  char c = advance();
  switch (c) {
    case '(': add_token(TokenType::LEFT_PAREN); break;
    case ')': add_token(TokenType::RIGHT_PAREN); break;
    case '{': add_token(TokenType::LEFT_BRACE); break;
    case '}': add_token(TokenType::RIGHT_BRACE); break;
    case ',': add_token(TokenType::COMMA); break;
    case '.': add_token(TokenType::DOT); break;
    case '-': add_token(TokenType::MINUS); break;
    case '+': add_token(TokenType::PLUS); break;
    case ';': add_token(TokenType::SEMICOLON); break;
    case '*': add_token(TokenType::STAR); break;
    case '!':
      add_token(match('=') ? TokenType::BANG_EQUAL : TokenType::BANG);
      break;
    case '=':
      add_token(match('=') ? TokenType::EQUAL_EQUAL : TokenType::EQUAL);
      break;
    case '<':
      add_token(match('=') ? TokenType::LESS_EQUAL : TokenType::LESS);
      break;
    case '>':
      add_token(match('=') ? TokenType::GREATER_EQUAL : TokenType::GREATER);
      break;
    case '/':
      if (match('/')) {
        while (peek() != '\n' && !is_at_end()) {
          advance();
        }
      } else {
        add_token(TokenType::SLASH);
      }

      break;
    case ' ':
    case '\r':
    case '\t':
      break;
    case '\n':
      ++line;
      break;
    case '"':
      string();
      break;
    default:
      error_handler.error(line, "Unexpected character.");
      break;
  }
}

char Scanner::advance() {
  return code.at(current++);
}

bool Scanner::match(char expected) {
  if (is_at_end() || peek() != expected) {
    return false;
  }

  current++;
  return true;
}

char Scanner::peek() {
  if (is_at_end()) {
    return '\0';
  }

  return code.at(current);
}

void Scanner::add_token(TokenType type) {
  add_token(type, Object{});
}

void Scanner::add_token(TokenType type, Object literal) {
  std::string text = code.substr(start, current - start);
  tokens.push_back(Token(type, text, literal, line));
}

void Scanner::string() {
  while (peek() != '"' && !is_at_end()) {
    if (peek() == '\n') line++;
    advance();
  }

  if (is_at_end()) {
    error_handler.error(line, "Unterminated string.");
    return;
  }

  // The closing ".
  advance();

  // Trim the surrounding quotes.
  std::string value = code.substr(start + 1, current - 1);
  add_token(TokenType::STRING, Object(StringObjectType::LITERAL, value));
}