/*
 * Tiny BASIC Interpreter and Compiler Project
 * Parser module
 *
 * Copyright (C) Damian Gareth Walker 2019
 * Created: 12-Aug-2019
 */


/* included headers */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "common.h"
#include "errors.h"
#include "options.h"
#include "token.h"
#include "tokeniser.h"
#include "parser.h"
#include "expression.h"


/*
 * Internal Function Declarations
 */


/* parse_expression() has a forward reference from parse_factor() */
static ExpressionNode *parse_expression (void);

/* parse_statement() has a forward reference from parse_if_statement() */
static StatementNode *parse_statement (void);


/*
 * Data Definitions
 */


/* private data */
typedef struct parser_data {
  int last_label; /* last line label encountered */
  int current_line; /* the last source line parsed */
  int end_of_file; /* end of file signal */
  Token *stored_token; /* token read ahead */
  TokenStream *stream; /* the input stream */
  ErrorHandler *errors; /* the parse error handler */
  LanguageOptions *options; /* the language options */
} ParserData;

/* convenience variables */
static Parser *this; /* the current parser being worked on */


/*
 * Private methods
 */


/*
 * Get next token to parse, from read-ahead buffer or tokeniser.
 */
static Token *get_token_to_parse () {

  /* local variables */
  Token *token; /* token to return */

  /* get the token one way or another */
  if (this->priv->stored_token) {
    token = this->priv->stored_token;
    this->priv->stored_token = NULL;
  } else
    token = this->priv->stream->next (this->priv->stream);

  /* store the line, check EOF and return the token */
  this->priv->current_line = token->get_line (token);
  if (token->get_class (token) == TOKEN_EOF)
    this->priv->end_of_file = !0;
  return token;
}

/*
 * Parse a factor
 * returns:
 *   FactorNode*   a new factor node holding the parsed data
 */
static FactorNode *parse_factor (void) {

  /* local variables */
  Token *token; /* token to read */
  FactorNode *factor = NULL; /* the factor we're building */
  ExpressionNode *expression = NULL; /* any parenthesised expression */
  int start_line; /* the line on which this factor occurs */

  /* initialise the factor and grab the next token */
  factor = factor_create ();
  token = get_token_to_parse ();
  start_line = token->get_line (token);

  /* interpret a sign */
  if (token->get_class (token) == TOKEN_PLUS
    || token->get_class (token) == TOKEN_MINUS) {
    factor->sign = (token->get_class (token) == TOKEN_PLUS)
      ? SIGN_POSITIVE
      : SIGN_NEGATIVE;
    token->destroy (token);
    token = get_token_to_parse ();
  }

  /* interpret a number */
  if (token->get_class (token) == TOKEN_NUMBER) {
    factor->class = FACTOR_VALUE;
    factor->data.value = atoi (token->get_content (token));
    if (factor->data.value < -32768 || factor->data.value > 32767)
      this->priv->errors->set_code
        (this->priv->errors, E_OVERFLOW, start_line, this->priv->last_label);
    token->destroy (token);
  }

  /* interpret a variable */
  else if (token->get_class (token) == TOKEN_VARIABLE) {
    factor->class = FACTOR_VARIABLE;
    factor->data.variable = (int) *token->get_content (token) & 0x1F;
    token->destroy (token);
  }

  /* interpret an parenthesised expression */
  else if (token->get_class (token) == TOKEN_LEFT_PARENTHESIS) {

    /* parse the parenthesised expression and complete the factor */
    token->destroy (token);
    expression = parse_expression ();
    if (expression) {
      token = get_token_to_parse ();
      if (token->get_class (token) == TOKEN_RIGHT_PARENTHESIS) {
        factor->class = FACTOR_EXPRESSION;
        factor->data.expression = expression;
      } else {
        this->priv->errors->set_code
          (this->priv->errors, E_MISSING_RIGHT_PARENTHESIS, start_line,
            this->priv->last_label);
        factor_destroy (factor);
        factor = NULL;
        expression_destroy (expression);
      }
      token->destroy (token);
    }

    /* clean up after invalid parenthesised expression */
    else {
      this->priv->errors->set_code (this->priv->errors, E_INVALID_EXPRESSION,
        token->get_line (token), this->priv->last_label);
      token->destroy (token);
      factor_destroy (factor);
      factor = NULL;
    }
  }

  /* deal with other errors */
  else {
    this->priv->errors->set_code
      (this->priv->errors, E_INVALID_EXPRESSION, token->get_line (token),
        this->priv->last_label);
    factor_destroy (factor);
    token->destroy (token);
    factor = NULL;
  }

  /* return the factor */
  return factor;
}

/*
 * Parse a term
 * globals:
 *   Token*      stored_token   the token read past the end of the term
 * returns:
 *   TermNode*   a new term node holding the parsed term
 */
static TermNode *parse_term (void) {

  /* local variables */
  TermNode *term = NULL; /* the term we're building */
  FactorNode *factor = NULL; /* factor detected */
  RightHandFactor
    *rhptr = NULL, /* previous right-hand factor */
    *rhfactor = NULL; /* right-hand factor detected */
  Token *token = NULL; /* token read while looking for operator */

  /* scan the first factor */
  if ((factor = parse_factor ())) {
    term = term_create ();
    term->factor = factor;
    term->next = NULL;

    /* look for subsequent factors */
    while ((token = get_token_to_parse ())
      && ! this->priv->errors->get_code (this->priv->errors)
      && (token->get_class (token) == TOKEN_MULTIPLY
      || token->get_class (token) == TOKEN_DIVIDE)) {

      /* parse the sign and the factor */
      rhfactor = rhfactor_create ();
      rhfactor->op = token->get_class (token) == TOKEN_MULTIPLY
          ? TERM_OPERATOR_MULTIPLY
          : TERM_OPERATOR_DIVIDE;
      if ((rhfactor->factor = parse_factor ())) {
        rhfactor->next = NULL;
        if (rhptr)
          rhptr->next = rhfactor;
        else
          term->next = rhfactor;
        rhptr = rhfactor;
      }

      /* set an error if we read an operator but not a factor */
      else {
        rhfactor_destroy (rhfactor);
        if (! this->priv->errors->get_code (this->priv->errors))
          this->priv->errors->set_code
            (this->priv->errors, E_INVALID_EXPRESSION, token->get_line (token),
              this->priv->last_label);
      }

      /* clean up token */
      token->destroy (token);
    }

    /* we've read past the end of the term; put the token back */
    this->priv->stored_token = token;
  }

  /* return the evaluated term, if any */
  return term;
}

/*
 * Parse an expression
 * returns:
 *   ExpressionNode*    the parsed expression
 */
static ExpressionNode *parse_expression (void) {

  /* local variables */
  ExpressionNode *expression = NULL; /* the expression we build */
  TermNode *term; /* term detected */
  RightHandTerm
    *rhterm = NULL, /* the right-hand term detected */
    *rhptr = NULL; /* pointer to the previous right-hand term */
  Token *token; /* token read when scanning for right-hand terms */

  /* scan the first term */
  if ((term = parse_term ())) {
    expression = expression_create ();
    expression->term = term;
    expression->next = NULL;

    /* look for subsequent terms */
    while ((token = get_token_to_parse ())
      && ! this->priv->errors->get_code (this->priv->errors)
      && (token->get_class (token) == TOKEN_PLUS
      || token->get_class (token) == TOKEN_MINUS)) {

      /* parse the sign and the factor */
      rhterm = rhterm_create ();
      rhterm->op = token->get_class (token) == TOKEN_PLUS
          ? EXPRESSION_OPERATOR_PLUS
          : EXPRESSION_OPERATOR_MINUS;
      if ((rhterm->term = parse_term ())) {
        rhterm->next = NULL;
        if (rhptr)
          rhptr->next = rhterm;
        else
          expression->next = rhterm;
        rhptr = rhterm;
      }

      /* set an error condition if we read a sign but not a factor */
      else {
        rhterm_destroy (rhterm);
        if (! this->priv->errors->get_code (this->priv->errors))
          this->priv->errors->set_code
            (this->priv->errors, E_INVALID_EXPRESSION, token->get_line (token),
              this->priv->last_label);
      }

      /* clean up token */
      token->destroy (token);
    }

    /* we've read past the end of the term; put the token back */
    this->priv->stored_token = token;
  }

  /* return the evaluated expression, if any */
  return expression;
}

/*
 * Calculate numeric line label according to language options.
 * This will be used if the line has no label specified.
 * returns:
 *   int                         numeric line label
 */
static int generate_default_label (void) {
  if (this->priv->options->get_line_numbers (this->priv->options)
    == LINE_NUMBERS_IMPLIED)
    return this->priv->last_label + 1;
  else
    return 0;
}

/*
 * Validate a line label according to the language options
 * params:
 *   int               label     the numeric label to verify.
 * returns:
 *   int                         !0 if the number is valid, 0 if invalid
 */
static int validate_line_label (int label) {

  /* line labels should be non-negative and within the set limit */
  if (label < 0
    || label > this->priv->options->get_line_limit (this->priv->options))
    return 0;

  /* line labels should be non-zero unless they're optional */
  if (label == 0
    && this->priv->options->get_line_numbers (this->priv->options)
      != LINE_NUMBERS_OPTIONAL)
    return 0;

  /* line labels should be ascending unless they're optional */
  if (label <= this->priv->last_label
    && this->priv->options->get_line_numbers (this->priv->options)
      != LINE_NUMBERS_OPTIONAL)
    return 0;

  /* if all the above tests passed, the line label is valid */
  return 1;
}

/*
 * Parse a LET statement
 * returns:
 *   StatementNode*          The statement assembled
 */
static StatementNode *parse_let_statement (void) {

  /* local variables */
  Token *token; /* tokens read as part of LET statement */
  int line; /* line containing the LET token */
  StatementNode *statement; /* the new statement */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_LET;
  statement->statement.letn = statement_create_let ();
  line = this->priv->stream->get_line (this->priv->stream);

  /* see what variable we're assigning */
  token = get_token_to_parse ();
  if (token->get_class (token) != TOKEN_VARIABLE) {
    this->priv->errors->set_code
      (this->priv->errors, E_INVALID_VARIABLE, line, this->priv->last_label);
    statement_destroy (statement);
    token->destroy (token);
    return NULL;
  }
  statement->statement.letn->variable = *token->get_content (token) & 0x1f;

  /* get the "=" */
  token->destroy (token);
  token = get_token_to_parse ();
  if (token->get_class (token) != TOKEN_EQUAL) {
    this->priv->errors->set_code
      (this->priv->errors, E_INVALID_ASSIGNMENT, line, this->priv->last_label);
    statement_destroy (statement);
    token->destroy (token);
    return NULL;
  }
  token->destroy (token);

  /* get the expression */
  statement->statement.letn->expression = parse_expression ();
  if (! statement->statement.letn->expression) {
    this->priv->errors->set_code
      (this->priv->errors, E_INVALID_EXPRESSION, line, this->priv->last_label);
    statement_destroy (statement);
    return NULL;
  }

  /* return the statement */
  return statement;
}

/*
 * Parse an IF statement
 * returns:
 *   StatementNode*          The statement to assemble.
 */
static StatementNode *parse_if_statement (void) {

  /* local variables */
  Token *token; /* tokens read as part of the statement */
  StatementNode *statement; /* the IF statement */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_IF;
  statement->statement.ifn = statement_create_if ();

  /* parse the first expression */
  statement->statement.ifn->left = parse_expression ();

  /* parse the operator */
  if (! this->priv->errors->get_code (this->priv->errors)) {
    token = get_token_to_parse ();
    switch (token->get_class (token)) {
    case TOKEN_EQUAL:
      statement->statement.ifn->op = RELOP_EQUAL;
      break;
    case TOKEN_UNEQUAL:
      statement->statement.ifn->op = RELOP_UNEQUAL;
      break;
    case TOKEN_LESSTHAN:
      statement->statement.ifn->op = RELOP_LESSTHAN;
      break;
    case TOKEN_LESSOREQUAL:
      statement->statement.ifn->op = RELOP_LESSOREQUAL;
      break;
    case TOKEN_GREATERTHAN:
      statement->statement.ifn->op = RELOP_GREATERTHAN;
      break;
    case TOKEN_GREATEROREQUAL:
      statement->statement.ifn->op = RELOP_GREATEROREQUAL;
      break;
    default:
      this->priv->errors->set_code
        (this->priv->errors, E_INVALID_OPERATOR, token->get_line (token),
        this->priv->last_label);
    }
    token->destroy (token);
  }

  /* parse the second expression */
  if (! this->priv->errors->get_code (this->priv->errors))
    statement->statement.ifn->right = parse_expression ();

  /* parse the THEN */
  if (! this->priv->errors->get_code (this->priv->errors)) {
    token = get_token_to_parse ();
    if (token->get_class (token) != TOKEN_THEN)
      this->priv->errors->set_code
        (this->priv->errors, E_THEN_EXPECTED, token->get_line (token), 
        this->priv->last_label);
    token->destroy (token);
  }

  /* parse the conditional statement */
  if (! this->priv->errors->get_code (this->priv->errors))
    statement->statement.ifn->statement = parse_statement ();

  /* destroy the half-made statement if errors occurred */
  if (this->priv->errors->get_code (this->priv->errors)) {
    statement_destroy (statement);
    statement = NULL;
  }

  /* return the statement */
  return statement;
}

/*
 * Parse a GOTO statement
 * returns:
 *   StatementNode*   the parsed GOTO statement
 */
static StatementNode *parse_goto_statement (void) {

  /* local variables */
  StatementNode *statement; /* the IF statement */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_GOTO;
  statement->statement.goton = statement_create_goto ();

  /* parse the line label expression */
  if (! (statement->statement.goton->label = parse_expression ())) {
    statement_destroy (statement);
    statement = NULL;
  }

  /* return the new statement */
  return statement;
}

/*
 * Parse a GOSUB statement
 * returns:
 *   StatementNode*   the parsed GOSUB statement
 */
static StatementNode *parse_gosub_statement (void) {

  /* local variables */
  StatementNode *statement; /* the IF statement */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_GOSUB;
  statement->statement.gosubn = statement_create_gosub ();

  /* parse the line label expression */
  if (! (statement->statement.gosubn->label = parse_expression ())) {
    statement_destroy (statement);
    statement = NULL;
  }

  /* return the new statement */
  return statement;
}

/*
 * Parse an RETURN statement
 * returns:
 *   StatementNode*          The statement assembled
 */
static StatementNode *parse_return_statement (void) {
  StatementNode *statement; /* the RETURN */
  statement = statement_create ();
  statement->class = STATEMENT_RETURN;
  return statement;
}

/*
 * Parse an END statement
 * returns:
 *   StatementNode*          The statement assembled
 */
static StatementNode *parse_end_statement (void) {
  StatementNode *statement = NULL; /* the END */
  statement = statement_create ();
  statement->class = STATEMENT_END;
  return statement;
}

/*
 * Parse a PRINT statement
 * returns:
 *   StatementNode*          The statement assembled
 */
static StatementNode *parse_print_statement (void) {

  /* local variables */
  Token *token = NULL; /* tokens read as part of the statement */
  StatementNode *statement; /* the statement we're building */
  int line; /* line containing the PRINT token */
  OutputNode
    *nextoutput = NULL, /* the next output node we're parsing */
    *lastoutput = NULL; /* the last output node we parsed */
  ExpressionNode *expression; /* a parsed expression */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_PRINT;
  statement->statement.printn = statement_create_print ();
  line = this->priv->stream->get_line (this->priv->stream);

  /* main loop for parsing the output list */
  do {

    /* discard a previous comma, and read the next output value */
    if (token)
      token->destroy (token);
    token = get_token_to_parse ();

    /* process a premature end of line */
    if (token->get_class (token) == TOKEN_EOF
      || token->get_class (token) == TOKEN_EOL) {
      this->priv->errors->set_code
        (this->priv->errors, E_INVALID_PRINT_OUTPUT, line,
        this->priv->last_label);
      statement_destroy (statement);
      statement = NULL;
      token->destroy (token);
    }

    /* process a literal string */
    else if (token->get_class (token) == TOKEN_STRING) {
      nextoutput = malloc (sizeof (OutputNode));
      nextoutput->class = OUTPUT_STRING;
      nextoutput->output.string = malloc
	(1 + strlen (token->get_content (token)));
      strcpy (nextoutput->output.string, token->get_content (token));
      nextoutput->next = NULL;
      token->destroy (token);
    }

    /* attempt to process an expression */
    else {
      this->priv->stored_token = token;
      if ((expression = parse_expression ())) {
        nextoutput = malloc (sizeof (OutputNode));
        nextoutput->class = OUTPUT_EXPRESSION;
        nextoutput->output.expression = expression;
        nextoutput->next = NULL;
      } else {
        this->priv->errors->set_code
          (this->priv->errors, E_INVALID_PRINT_OUTPUT, token->get_line (token),
             this->priv->last_label);
        statement_destroy (statement);
        statement = NULL;
      }
    }

    /* add this output item to the statement and look for another */
    if (! this->priv->errors->get_code (this->priv->errors)) {
      if (lastoutput)
        lastoutput->next = nextoutput;
      else
        statement->statement.printn->first = nextoutput;
      lastoutput = nextoutput;
      token = get_token_to_parse ();
    }

  /* continue the loop until the statement appears to be finished */
  } while (! this->priv->errors->get_code (this->priv->errors)
    && token->get_class (token) == TOKEN_COMMA);

  /* push back the last token and return the assembled statement */
  if (! this->priv->errors->get_code (this->priv->errors))
    this->priv->stored_token = token;
  return statement;
}

/*
 * Parse an INPUT statement
 * returns:
 *   StatementNode*          The statement assembled
 */
static StatementNode *parse_input_statement (void) {

  /* local variables */
  Token *token = NULL; /* tokens read as part of the statement */
  StatementNode *statement; /* the statement we're building */
  int line; /* line containing the INPUT token */
  VariableListNode
    *nextvar = NULL, /* the next variable node we're parsing */
    *lastvar = NULL; /* the last variable node we parsed */

  /* initialise the statement */
  statement = statement_create ();
  statement->class = STATEMENT_INPUT;
  statement->statement.inputn = statement_create_input ();
  line = this->priv->stream->get_line (this->priv->stream);

  /* main loop for parsing the variable list */
  do {

    /* discard a previous comma, and seek the next variable */
    if (token) token->destroy (token);
    token = get_token_to_parse ();

    /* process a premature end of line */
    if (token->get_class (token) == TOKEN_EOF
      || token->get_line (token) != line) {
      this->priv->errors->set_code
        (this->priv->errors, E_INVALID_VARIABLE, line, this->priv->last_label);
      statement_destroy (statement);
      statement = NULL;
    }

    /* attempt to process an variable name */
    else if (token->get_class (token) != TOKEN_VARIABLE) {
      this->priv->errors->set_code
        (this->priv->errors, E_INVALID_VARIABLE, token->get_line (token),
	this->priv->last_label);
      statement_destroy (statement);
      statement = NULL;
    } else {
      nextvar = malloc (sizeof (VariableListNode));
      nextvar->variable = *token->get_content (token) & 0x1f;
      nextvar->next = NULL;
      token->destroy (token);
    }

    /* add this variable to the statement and look for another */
    if (! this->priv->errors->get_code (this->priv->errors)) {
      if (lastvar)
        lastvar->next = nextvar;
      else
        statement->statement.inputn->first = nextvar;
      lastvar = nextvar;
      token = get_token_to_parse ();
    }
  } while (! this->priv->errors->get_code (this->priv->errors)
    && token->get_class (token) == TOKEN_COMMA);

  /* return the assembled statement */
  this->priv->stored_token = token;
  return statement;
}

/*
 * Parse a statement from the source file
 * returns:
 *   StatementNode*   a fully-assembled statement, hopefully.
 */
static StatementNode *parse_statement () {

  /* local variables */
  Token *token; /* token read */
  StatementNode *statement = NULL; /* the new statement */

  /* get the next token */
  token = get_token_to_parse ();

  /* check for command */
  switch (token->get_class (token)) {
    case TOKEN_EOL:
      this->priv->stored_token = token;
      statement = NULL;
      break;
    case TOKEN_LET:
      token->destroy (token);
      statement = parse_let_statement ();
      break;
    case TOKEN_IF:
      token->destroy (token);
      statement = parse_if_statement ();
      break;
    case TOKEN_GOTO:
      token->destroy (token);
      statement = parse_goto_statement ();
      break;
    case TOKEN_GOSUB:
      token->destroy (token);
      statement = parse_gosub_statement ();
      break;
    case TOKEN_RETURN:
      token->destroy (token);
      statement = parse_return_statement ();
      break;
    case TOKEN_END:
      token->destroy (token);
      statement = parse_end_statement ();
      break;
    case TOKEN_PRINT:
      token->destroy (token);
      statement = parse_print_statement ();
      break;
    case TOKEN_INPUT:
      token->destroy (token);
      statement = parse_input_statement ();
      break;
    default:
      this->priv->errors->set_code
        (this->priv->errors, E_UNRECOGNISED_COMMAND, token->get_line (token),
        this->priv->last_label);
      token->destroy (token);
  }

  /* return the statement */
  return statement;
}

/*
 * Parse a line from the source file.
 * returns:
 *   StatementNode           a fully-assembled statement, hopefully.
 */
static ProgramLineNode *parse_program_line (void) {

  /* local variables */
  Token *token; /* token read */
  ProgramLineNode *program_line; /* program line read */
  int label_encountered = 0; /* 1 if this line has an explicit label */

  /* initialise the program line and get the first token */
  program_line = program_line_create ();
  program_line->label = generate_default_label ();
  token = get_token_to_parse ();

  /* deal with end of file */
  if (token->get_class (token) == TOKEN_EOF) {
    token->destroy (token);
    program_line_destroy (program_line);
    return NULL;
  }

  /* deal with line label, if supplied */
  if (token->get_class (token) == TOKEN_NUMBER) {
    program_line->label = atoi (token->get_content (token));
    label_encountered = 1;
    token->destroy (token);
  } else
    this->priv->stored_token = token;

  /* validate the supplied or implied line label */
  if (! validate_line_label (program_line->label)) {
    this->priv->errors->set_code
      (this->priv->errors, E_INVALID_LINE_NUMBER, this->priv->current_line,
      program_line->label);
    program_line_destroy (program_line);
    return NULL;
  }
  if (label_encountered)
    this->priv->last_label = program_line->label;

  /* check for a statement and an EOL */
  program_line->statement = parse_statement ();
  if (! this->priv->errors->get_code (this->priv->errors)) {
    token = get_token_to_parse ();
    if (token->get_class (token) != TOKEN_EOL
      && token->get_class (token) != TOKEN_EOF)
      this->priv->errors->set_code
        (this->priv->errors, E_UNEXPECTED_PARAMETER, this->priv->current_line,
        this->priv->last_label);
    token->destroy (token);
  }
  if (program_line->statement)
    this->priv->last_label = program_line->label;

  /* return the program line */
  return program_line;
}


/*
 * Public Methods
 */


/*
 * Parse the whole program
 * params:
 *   Parser*   parser   The parser to use
 * returns:
 *   ProgramNode*       The parsed program
 */
static ProgramNode *parse (Parser *parser) {

  /* local varables */
  ProgramNode *program; /* the stored program */
  ProgramLineNode
    *previous = NULL, /* the previous line */
    *current; /* the current line */

  /* initialise the program */
  this = parser;
  program = malloc (sizeof (ProgramNode));
  program->first = NULL;

  /* read lines until reaching an error or end of input */
  while ((current = parse_program_line ())
    && ! this->priv->errors->get_code (this->priv->errors)) {
    if (previous)
      previous->next = current;
    else
      program->first = current;
    previous = current;
  }

  /* return the program */
  return program;
}

/*
 * Return the current source line we're parsing
 * params:
 *   Parser*   The parser to use
 * returns:
 *   int       the line returned
 */
static int get_line (Parser *parser) {
  return parser->priv->current_line;
}

/*
 * Return the label of the source line we're parsing
 * params:
 *   Parser*   parser   The parser to use
 * returns:
 *   int                the label returned
 */
static int get_label (Parser *parser) {
  return parser->priv->last_label;
}

/*
 * Destroy this parser object
 * params:
 *   Parser*   parser   the doomed parser
 */
void destroy (Parser *parser) {
  if (parser) {
    if (parser->priv) {
      if (parser->priv->stream)
        parser->priv->stream->destroy (parser->priv->stream);
    }
    free (parser->priv);
  }
  free (parser);
}


/*
 * Constructors
 */


/*
 * Constructor
 * params:
 *   ErrorHandler*      errors    the error handler to use
 *   LanguageOptions*   options   the language options to use
 *   FILE*              input     the input file
 * returns:
 *   Parser*                      the new parser
 */
Parser *new_Parser (ErrorHandler *errors, LanguageOptions *options,
  FILE *input) {

  /* allocate memory */
  this = malloc (sizeof (Parser));
  this->priv = malloc (sizeof (ParserData));
  this->priv->stream = new_TokenStream (input);

  /* initialise methods */
  this->parse = parse;
  this->get_line = get_line;
  this->get_label = get_label;
  this->destroy = destroy;

  /* initialise properties */
  this->priv->last_label = 0;
  this->priv->current_line = 0;
  this->priv->end_of_file = 0;
  this->priv->stored_token = NULL;
  this->priv->errors = errors;
  this->priv->options = options;

  /* return the new object */
  return this;
}