#include "parser.h"
#include "assert.h"
#include "printf.h"
#include "malloc.h"

struct token peek(struct token_reader * reader)
{
  if (reader->have_token) {
    return reader->token;
  } else {
    reader->token = lexer_next_token(&reader->lexer_state);
    reader->have_token = true;
    return reader->token;
  }
}

struct token consume(struct token_reader * reader)
{
  struct token token = peek(reader);
  reader->have_token = false;
  return token;
}

bool match_type(struct token_reader * reader, enum token_type token_type)
{
  struct token token = peek(reader);
  if (token.type == token_type) {
    consume(reader);
    return true;
  } else {
    return false;
  }
}

struct token expect_type(struct token_reader * reader, enum token_type token_type)
{
  struct token token = consume(reader);
  if (!(token.type == token_type)) {
    printf("token.type=%d token_type=%d\n", token.type, token_type);
    fail(token.type == token_type);
  }
  return token;
}

struct expression * parse_expression(struct token_reader * reader)
{
  struct expression * expr = malloct(struct expression);
  struct token token = expect_type(reader, TOKEN_CONSTANT);
  expr->constant = token;
  return expr;
}

struct statement_return * parse_statement_return(struct token_reader * reader)
{
  struct expression * expr = parse_expression(reader);
  struct statement_return * stmt = malloct(struct statement_return);
  stmt->expression = expr;
  return stmt;
}

struct statement_if_else * parse_statement_if_else(struct token_reader * reader)
{
  struct statement_if_else * stmt = malloct(struct statement_if_else);
  expect_type(reader, TOKEN_LPAREN);
  struct expression * expr = parse_expression(reader);
  expect_type(reader, TOKEN_RPAREN);
  struct statement * statement_if = parse_statement(reader);
  struct statement * statement_else = match_type(reader, TOKEN_ELSE) ? parse_statement(reader) : nullptr;
  stmt->expression = expr;
  stmt->statement_if = statement_if;
  stmt->statement_else = statement_else;
  return stmt;
}

struct statement * parse_statement(struct token_reader * reader)
{
  struct statement * stmt = malloct(struct statement);
  if (match_type(reader, TOKEN_IF)) {
    stmt->type = STATEMENT_IF_ELSE;
    stmt->statement_if_else = parse_statement_if_else(reader);
  } else if (match_type(reader, TOKEN_RETURN)) {
    stmt->type = STATEMENT_RETURN;
    stmt->statement_return = parse_statement_return(reader);
  } else {
    printf("token_type=%d\n", peek(reader).type);
    fail("expected statement");
  }

  return stmt;
}