#include "Parser.hpp"
#include "lib/Node.hpp"

namespace wg
{
  /*explicit*/ Parser::Parser()
  {
  }

  /*virtual*/ Parser::~Parser()
  {
  }

  std::shared_ptr<Node> Parser::parse(std::vector<std::shared_ptr<Node>>
                                      const& tokens)
  {
    m_cursor = 0;
    m_tokens = tokens;

    return parse_prog();
  }

  Loc Parser::loc() const
  {
    if (m_cursor >= m_tokens.size())
      {
        return m_tokens.back()->loc();
      }

    return m_tokens[m_cursor]->loc();
  }

  std::shared_ptr<Node> Parser::consume(NodeType type)
  {
    if (m_cursor >= m_tokens.size())
      {
        std::stringstream ss;
        ss << "type mismatch, expected '"
           << (NodeTypeStr[type] + strlen("NODE_"))
           << "', got nothing.";

        loc().error<syntax_error>(ss);
      }

    auto current = m_tokens[m_cursor];

    if (current->type() != type)
      {
        std::stringstream ss;
        ss << "type mismatch, expected '"
           << (NodeTypeStr[type] + strlen("NODE_"))
           << "', got '"
           << (NodeTypeStr[current->type()] + strlen("NODE_"))
           << "'";

        loc().error<syntax_error>(ss);
      }
    else
      {
        return consume();
      }

    return nullptr;
  }

  std::shared_ptr<Node> Parser::consume()
  {
    WG_ASSERT(m_cursor < m_tokens.size(), "cannot consume");
    auto node = m_tokens[m_cursor];
    m_cursor++;
    return node;
  }

  bool Parser::type_is(NodeType type, int lookahead)
  {
    if (m_cursor + lookahead >= m_tokens.size())
      {
        return false;
      }

    return m_tokens[m_cursor + lookahead]->type() == type;
  }

  bool Parser::type_isnt(NodeType type, int lookahead)
  {
    return !type_is(type, lookahead);
  }

  std::shared_ptr<Node> Parser::make_node(NodeType type) const
  {
    return std::make_shared<Node>(type, "", loc());
  }

  std::shared_ptr<Node> Parser::parse_prog()
  {
    auto node = std::make_shared<Node>(NODE_PROG, "", Loc {});


    while (m_cursor < m_tokens.size())
      {
        node->add_child(parse_instr());
      }

    return node;
  }

  std::shared_ptr<Node> Parser::parse_instr()
  {
    if (type_is(NODE_HASH))
      {
        return parse_dir();
      }

    if (type_is(NODE_FUN))
      {
        return parse_fundecl();
      }

    if (type_is(NODE_RETURN))
      {
        auto node = consume();
        node->add_child(parse_expr());
        consume(NODE_SEMICOLON);
        return node;
      }

    if (type_is(NODE_EXTERN))
      {
        auto node = parse_extern();
        consume(NODE_SEMICOLON);
        return node;
      }

    auto expr = parse_expr();
    consume(NODE_SEMICOLON);
    return expr;
  }

  std::shared_ptr<Node> Parser::parse_extern()
  {
    auto node = consume(NODE_EXTERN);
    consume(NODE_FUN);
    node->add_child(consume(NODE_IDENT));

    consume(NODE_OPAR);
    node->add_child(parse_params());
    consume(NODE_CPAR);

    node->add_child(parse_ret());

    return node;
  }

  std::shared_ptr<Node> Parser::parse_fundecl()
  {
    auto node = make_node(NODE_FUNDECL);
    consume(NODE_FUN);
    node->add_child(consume(NODE_IDENT));
    consume(NODE_OPAR);
    node->add_child(parse_params());
    consume(NODE_CPAR);

    node->add_child(parse_ret());

    node->add_child(parse_block());

    return node;
  }

  std::shared_ptr<Node> Parser::parse_params()
  {
    auto node = make_node(NODE_PARAMS);

    if (type_is(NODE_CPAR))
      {
        return node;
      }

    node->add_child(consume(NODE_IDENT));

    if (type_is(NODE_TYPE))
      {
        node->add_child(consume());
      }

    while (type_is(NODE_COMMA))
      {
        consume();

        node->add_child(consume(NODE_IDENT));

        if (type_is(NODE_TYPE))
          {
            node->add_child(consume());
          }
      }

    return node;
  }

  std::shared_ptr<Node> Parser::parse_ret()
  {
    auto node = make_node(NODE_RET);

    if (type_is(NODE_TYPE))
      {
        node->add_child(consume());
      }

    return node;
  }

  std::shared_ptr<Node> Parser::parse_block()
  {
    auto node = make_node(NODE_BLOCK);
    consume(NODE_OBRACE);

    while (type_isnt(NODE_CBRACE))
      {
        node->add_child(parse_instr());
      }

    consume(NODE_CBRACE);

    return node;
  }

  std::shared_ptr<Node> Parser::parse_dir()
  {
    auto node = make_node(NODE_DIR);
    consume(NODE_HASH);
    node->add_child(consume(NODE_IDENT));
    node->add_child(parse_expr());

    if (type_is(NODE_AS))
      {
        consume();
        node->add_child(consume(NODE_IDENT));
      }

    return node;
  }

  std::shared_ptr<Node> Parser::parse_expr()
  {
    return parse_addsub();
  }

  std::shared_ptr<Node> Parser::parse_addsub()
  {
    auto lhs = parse_muldivmod();

    while (type_is(NODE_ADD)
           || type_is(NODE_SUB))
      {
        auto node = consume();
        node->add_child(lhs);
        node->add_child(parse_muldivmod());
        lhs = node;
      }

    return lhs;
  }

  std::shared_ptr<Node> Parser::parse_muldivmod()
  {
    auto lhs = parse_literal();

    while (type_is(NODE_MUL)
           || type_is(NODE_DIV)
           || type_is(NODE_MOD))
      {
        auto node = consume();
        node->add_child(lhs);
        node->add_child(parse_literal());
        lhs = node;
      }

    return lhs;
  }

  std::shared_ptr<Node> Parser::parse_literal()
  {
    if (type_is(NODE_IDENT)
        && type_is(NODE_OPAR, 1))
      {
        return parse_call();
      }

    if (type_is(NODE_IDENT)
        && type_is(NODE_DOT, 1))
      {
        return parse_ns();
      }

    if (type_is(NODE_INT)
        || type_is(NODE_IDENT))
      {
        return consume();
      }

    // Groups
    if (type_is(NODE_OPAR))
      {
        consume(NODE_OPAR);

        auto expr = parse_expr();

        consume(NODE_CPAR);

        return expr;
      }

    loc().error<syntax_error>(std::string()
                              + "unknown literal '"
                              + (NodeTypeStr[m_tokens[m_cursor]->type()]
                                 + strlen("NODE_"))
                              + "'");
    return nullptr;
  }

  std::shared_ptr<Node> Parser::parse_call()
  {
    auto node = make_node(NODE_CALL);
    node->add_child(consume(NODE_IDENT));

    consume(NODE_OPAR);
    node->add_child(parse_args());
    consume(NODE_CPAR);

    return node;
  }

  std::shared_ptr<Node> Parser::parse_args()
  {
    auto node = make_node(NODE_ARGS);

    if (type_is(NODE_CPAR))
      {
        return node;
      }

    node->add_child(parse_expr());

    while (type_is(NODE_COMMA))
      {
        consume();
        node->add_child(parse_expr());
      }

    return node;
  }

  std::shared_ptr<Node> Parser::parse_ns()
  {
    auto node = make_node(NODE_NS);
    node->add_child(consume(NODE_IDENT));

    while (type_is(NODE_DOT))
      {
        consume();

        if (type_is(NODE_IDENT)
            && type_is(NODE_OPAR, 1))
          {
            node->add_child(parse_call());
          }
        else
          {
            node->add_child(consume(NODE_IDENT));
          }
      }

    return node;
  }
}