#include "runtime/lexer.h"
#include "tree_sitter/parser.h"
#include "runtime/tree.h"

static int advance(TSLexer *lexer) {
  if (lexer->position_in_chunk + 1 < lexer->chunk_size) {
    lexer->position_in_chunk++;
    return 1;
  }

  static const char *empty_chunk = "";
  if (lexer->chunk == empty_chunk)
    return 0;

  lexer->chunk_start += lexer->chunk_size;
  lexer->chunk = lexer->input.read_fn(lexer->input.data, &lexer->chunk_size);
  lexer->position_in_chunk = 0;
  if (lexer->chunk_size == 0)
    lexer->chunk = empty_chunk;

  return 1;
}

static TSTree *accept(TSLexer *lexer, TSSymbol symbol, int is_hidden) {
  size_t current_position = ts_lexer_position(lexer);
  size_t size = current_position - lexer->token_start_position;
  size_t padding = lexer->token_start_position - lexer->token_end_position;
  lexer->token_end_position = current_position;
  return (symbol == ts_builtin_sym_error)
             ? ts_tree_make_error(size, padding, ts_lexer_lookahead_char(lexer))
             : ts_tree_make_leaf(symbol, size, padding, is_hidden);
}

/*
 *  The `advance` and `accept` methods are stored as fields on the Lexer so
 *  that generated parsers can call them without needing to be linked against
 *  this library.
 */
TSLexer ts_lexer_make() {
  TSLexer result = (TSLexer) { .debug = 0,
                               .advance_fn = advance,
                               .accept_fn = accept, };
  ts_lexer_reset(&result);
  return result;
}

void ts_lexer_reset(TSLexer *lexer) {
  lexer->chunk = NULL;
  lexer->chunk_start = 0;
  lexer->chunk_size = 0;
  lexer->position_in_chunk = 0;
  lexer->token_start_position = 0;
  lexer->token_end_position = 0;
}