/* Parser combinators for binary formats.
 * Copyright (C) 2012  Meredith L. Patterson, Dan "TQ" Hirsch
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#ifndef HAMMER_HAMMER__H
#define HAMMER_HAMMER__H
#include <glib.h>
#include <stdint.h>
#include "allocator.h"

#define BYTE_BIG_ENDIAN 0x1
#define BIT_BIG_ENDIAN 0x2
#define BIT_LITTLE_ENDIAN 0x0
#define BYTE_LITTLE_ENDIAN 0x0

typedef int bool;

typedef struct parse_state parse_state_t;

typedef enum token_type {
  TT_NONE,
  TT_BYTES,
  TT_SINT,
  TT_UINT,
  TT_SEQUENCE,
  TT_USER = 64,
  TT_ERR,
  TT_MAX
} token_type_t;

typedef struct counted_array {
  size_t capacity;
  size_t used;
  arena_t arena;
  void **elements;
} counted_array_t;

typedef struct parsed_token {
  token_type_t token_type;
  union {
    struct {
      const uint8_t *token;
      size_t len;
    } bytes;
    int64_t sint;
    uint64_t uint;
    double dbl;
    float flt;
    counted_array_t *seq; // a sequence of parsed_token_t's
    void *user;
  };
  size_t index;
  char bit_offset;
} parsed_token_t;

/**
 * The result of a successful parse.
 * If a parse fails, the parse result will be NULL.
 * If a parse is successful but there's nothing there (i.e., if end_p 
 * succeeds) then there's a parse result but its ast is NULL.
 */
typedef struct parse_result {
  const parsed_token_t *ast;
  arena_t arena;
} parse_result_t;

/**
 * Type of an action to apply to an AST, used in the action() parser. 
 * It can be any (user-defined) function that takes a parse_result_t*
 * and returns a parsed_token_t*. (This is so that the user doesn't 
 * have to worry about memory allocation; action() does that for you.)
 * Note that the tagged union in parsed_token_t* supports user-defined 
 * types, so you can create your own token types (corresponding to, 
 * say, structs) and stuff values for them into the void* in the 
 * tagged union in parsed_token_t. 
 */
typedef parsed_token_t* (*action_t)(parse_result_t *p);

/**
 * Type of a boolean attribute-checking function, used in the 
 * attr_bool() parser. It can be any (user-defined) function that takes
 * a parse_result_t* and returns true or false. 
 */
typedef bool (*predicate_t)(parse_result_t *p);

typedef struct parser {
  parse_result_t* (*fn)(void *env, parse_state_t *state);
  void *env;
} parser_t;

/**
 * Top-level function to call a parser that has been built over some
 * piece of input (of known size).
 */
parse_result_t* parse(const parser_t* parser, const uint8_t* input, size_t length);

/**
 * Given a string, returns a parser that parses that string value. 
 */
const parser_t* token(const uint8_t *str, const size_t len);

/**
 * Given a single character, returns a parser that parses that 
 * character. 
 */
const parser_t* ch(const uint8_t c);

/**
 * Given two single-character bounds, lower and upper, returns a parser
 * that parses a single character within the range [lower, upper] 
 * (inclusive). 
 */
const parser_t* range(const uint8_t lower, const uint8_t upper);

/**
 * Returns a parser that parses the specified number of bits. sign == 
 * true if signed, false if unsigned. 
 */
const parser_t* bits(size_t len, bool sign);

/**
 * Returns a parser that parses a signed 8-byte integer value. 
 */
const parser_t* int64();

/**
 * Returns a parser that parses a signed 4-byte integer value. 
 */
const parser_t* int32();

/**
 * Returns a parser that parses a signed 2-byte integer value. 
 */
const parser_t* int16();

/**
 * Returns a parser that parses a signed 1-byte integer value. 
 */
const parser_t* int8();

/**
 * Returns a parser that parses an unsigned 8-byte integer value. 
 */
const parser_t* uint64();

/**
 * Returns a parser that parses an unsigned 4-byte integer value. 
 */
const parser_t* uint32();

/**
 * Returns a parser that parses an unsigned 2-byte integer value. 
 */
const parser_t* uint16();

/**
 * Returns a parser that parses an unsigned 1-byte integer value. 
 */
const parser_t* uint8();

/**
 * Returns a parser that parses a double-precision floating-point 
 * value. 
 */
const parser_t* float64();

/**
 * Returns a parser that parses a single-precision floating-point 
 * value. 
 */
const parser_t* float32();

/**
 * Given another parser, p, returns a parser that skips any whitespace 
 * and then applies p. 
 */
const parser_t* whitespace(const parser_t* p);

/**
 * Given another parser, p, and a function f, returns a parser that 
 * applies p, then applies f to everything in the AST of p's result. 
 */
const parser_t* action(const parser_t* p, const action_t a);

/**
 * Parse a single character *NOT* in the given charset. 
 */
const parser_t* not_in(const uint8_t *charset, int length);

/**
 * A no-argument parser that succeeds if there is no more input to 
 * parse. 
 */
const parser_t* end_p();

/**
 * This parser always fails. 
 */
const parser_t* nothing_p();

/**
 * Given a null-terminated list of parsers, apply each parser in order.
 * The parse succeeds only if all parsers succeed. 
 */
const parser_t* sequence(const parser_t* p, ...) __attribute__((sentinel));

/**
 * Given an array of parsers, p_array, apply each parser in order. The 
 * first parser to succeed is the result; if no parsers succeed, the 
 * parse fails. 
 */
const parser_t* choice(const parser_t* p, ...) __attribute__((sentinel));

/**
 * Given two parsers, p1 and p2, this parser succeeds in the following 
 * cases: 
 * - if p1 succeeds and p2 fails
 * - if both succeed but p1's result is as long as or shorter than p2's
 */
const parser_t* butnot(const parser_t* p1, const parser_t* p2);

/**
 * Given two parsers, p1 and p2, this parser succeeds in the following 
 * cases:
 * - if p1 succeeds and p2 fails
 * - if both succeed but p2's result is shorter than p1's
 */
const parser_t* difference(const parser_t* p1, const parser_t* p2);

/**
 * Given two parsers, p1 and p2, this parser succeeds if *either* p1 or
 * p2 succeed, but not if they both do.
 */
const parser_t* xor(const parser_t* p1, const parser_t* p2);

/**
 * Given a parser, p, this parser succeeds for zero or more repetitions
 * of p. 
 */
const parser_t* many(const parser_t* p);

/**
 * Given a parser, p, this parser succeeds for one or more repetitions 
 * of p. 
 */
const parser_t* many1(const parser_t* p);

/**
 * Given a parser, p, this parser succeeds for exactly N repetitions 
 * of p. 
 */
const parser_t* repeat_n(const parser_t* p, const size_t n);

/**
 * Given a parser, p, this parser succeeds with the value p parsed or 
 * with an empty result. 
 */
const parser_t* optional(const parser_t* p);

/**
 * Given a parser, p, this parser succeeds if p succeeds, but doesn't 
 * include p's result in the result. 
 */
const parser_t* ignore(const parser_t* p);

/**
 * Given a parser, p, and a parser for a separator, sep, this parser 
 * matches a (possibly empty) list of things that p can parse, 
 * separated by sep.
 * For example, if p is repeat1(range('0','9')) and sep is ch(','), 
 * sepBy(p, sep) will match a comma-separated list of integers. 
 */
const parser_t* sepBy(const parser_t* p, const parser_t* sep);

/**
 * Given a parser, p, and a parser for a separator, sep, this parser matches a list of things that p can parse, separated by sep. Unlike sepBy, this ensures that the result has at least one element.
 * For example, if p is repeat1(range('0','9')) and sep is ch(','), sepBy1(p, sep) will match a comma-separated list of integers. 
 */
const parser_t* sepBy1(const parser_t* p, const parser_t* sep);

/**
 * This parser always returns a zero length match, i.e., empty string. 
 */
const parser_t* epsilon_p();

/**
 * This parser attaches a predicate function, which returns true or 
 * false, to a parser. The function is evaluated over the parser's 
 * result. 
 * The parse only succeeds if the attribute function returns true. 
 */
const parser_t* attr_bool(const parser_t* p, predicate_t pred);

/**
 * The 'and' parser is a predicate. It asserts that a conditional 
 * syntax is satisfied, but consumes no input. 
 * This is useful for lookahead. As an example:
 *
 * Suppose you already have a parser, hex_p, that parses numbers in 
 * hexadecimal format (including the leading '0x'). Then
 *   sequence(and(token((const uint8_t*)"0x", 2)), hex_p)
 * checks to see whether there is a leading "0x", *does not* consume 
 * the "0x", and then applies hex_p to parse the hex-formatted number.
 *
 * 'and' succeeds if p succeeds, and fails if p fails. Like 'ignore', 
 * 'and' does not attach a result to the AST.
 */
const parser_t* and(const parser_t* p);

/**
 * The 'not' parser is a predicate. It asserts that a conditional 
 * syntax is *not* satisfied, and consumes no input.
 * As a somewhat contrived example:
 * 
 * Since 'choice' applies its arguments in order, the following parser:
 *   sequence(ch('a'), choice(ch('+'), token((const uint8_t*)"++"), NULL), ch('b'), NULL)
 * will not parse "a++b", because once choice() has succeeded, it will 
 * not backtrack and try other alternatives if a later parser in the 
 * sequence fails. 
 * Instead, you can force the use of the second alternative by turning 
 * the ch('+') alternative into a sequence with not:
 *   sequence(ch('a'), choice(sequence(ch('+'), not(ch('+')), NULL), token((const uint8_t*)"++")), ch('b'), NULL)
 * If the input string is "a+b", the first alternative is applied; if 
 * the input string is "a++b", the second alternative is applied.
 */
const parser_t* not(const parser_t* p);

/**
 * Create a parser that just calls out to another, as yet unknown, 
 * parser.
 * Note that the inner parser gets bound later, with bind_indirect.
 * This can be used to create recursive parsers.
 */
parser_t *indirect();

/**
 * Set the inner parser of an indirect. See comments on indirect for 
 * details.
 */
void bind_indirect(parser_t* indirect, parser_t* inner);

#endif // #ifndef HAMMER_HAMMER__H