/* 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 <stdio.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 HParseState_ HParseState;

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

typedef struct HCountedArray_ {
  size_t capacity;
  size_t used;
  HArena * arena;
  struct HParsedToken_ **elements;
} HCountedArray;

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

/**
 * 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 HParseResult_ {
  const HParsedToken *ast;
  long long bit_length;
  HArena * arena;
} HParseResult;

/**
 * TODO: document me.
 * Relevant functions: h_bit_writer_new, h_bit_writer_put, h_bit_writer_get_buffer, h_bit_writer_free
 */
typedef struct HBitWriter_ HBitWriter;

/**
 * Type of an action to apply to an AST, used in the action() parser. 
 * It can be any (user-defined) function that takes a HParseResult*
 * and returns a HParsedToken*. (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 HParsedToken* 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 HParsedToken. 
 */
typedef const HParsedToken* (*HAction)(const HParseResult *p);

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

typedef struct HParserVtable_ {
  HParseResult* (*parse)(void *env, HParseState *state);
} HParserVtable;

typedef struct HParser_ {
  const HParserVtable *vtable;
  void *env;
} HParser;

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

/**
 * Given a string, returns a parser that parses that string value. 
 * 
 * Result token type: TT_BYTES
 */
const HParser* h_token(const uint8_t *str, const size_t len);

/**
 * Given a single character, returns a parser that parses that 
 * character. 
 * 
 * Result token type: TT_UINT
 */
const HParser* h_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). 
 * 
 * Result token type: TT_UINT
 */
const HParser* h_ch_range(const uint8_t lower, const uint8_t upper);

/**
 * Given an integer parser, p, and two integer bounds, lower and upper,
 * returns a parser that parses an integral value within the range 
 * [lower, upper] (inclusive).
 */
const HParser* h_int_range(const HParser *p, const int64_t lower, const int64_t upper);

/**
 * Returns a parser that parses the specified number of bits. sign == 
 * true if signed, false if unsigned. 
 *
 * Result token type: TT_SINT if sign == true, TT_UINT if sign == false
 */
const HParser* h_bits(size_t len, bool sign);

/**
 * Returns a parser that parses a signed 8-byte integer value. 
 *
 * Result token type: TT_SINT
 */
const HParser* h_int64();

/**
 * Returns a parser that parses a signed 4-byte integer value. 
 *
 * Result token type: TT_SINT
 */
const HParser* h_int32();

/**
 * Returns a parser that parses a signed 2-byte integer value. 
 *
 * Result token type: TT_SINT
 */
const HParser* h_int16();

/**
 * Returns a parser that parses a signed 1-byte integer value. 
 *
 * Result token type: TT_SINT
 */
const HParser* h_int8();

/**
 * Returns a parser that parses an unsigned 8-byte integer value. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_uint64();

/**
 * Returns a parser that parses an unsigned 4-byte integer value. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_uint32();

/**
 * Returns a parser that parses an unsigned 2-byte integer value. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_uint16();

/**
 * Returns a parser that parses an unsigned 1-byte integer value. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_uint8();

/**
 * Given another parser, p, returns a parser that skips any whitespace 
 * and then applies p. 
 *
 * Result token type: p's result type
 */
const HParser* h_whitespace(const HParser* p);

/**
 * Given two parsers, p and q, returns a parser that parses them in
 * sequence but only returns p's result.
 *
 * Result token type: p's result type
 */
const HParser* h_left(const HParser* p, const HParser* q);

/**
 * Given two parsers, p and q, returns a parser that parses them in
 * sequence but only returns q's result.
 *
 * Result token type: q's result type
 */
const HParser* h_right(const HParser* p, const HParser* q);

/**
 * Given three parsers, p, x, and q, returns a parser that parses them in
 * sequence but only returns x's result.
 *
 * Result token type: x's result type
 */
const HParser* h_middle(const HParser* p, const HParser* x, const HParser* q);

/**
 * 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. 
 *
 * Result token type: any
 */
const HParser* h_action(const HParser* p, const HAction a);

/**
 * Parse a single character in the given charset. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_in(const uint8_t *charset, size_t length);

/**
 * Parse a single character *NOT* in the given charset. 
 *
 * Result token type: TT_UINT
 */
const HParser* h_not_in(const uint8_t *charset, size_t length);

/**
 * A no-argument parser that succeeds if there is no more input to 
 * parse. 
 *
 * Result token type: None. The HParseResult exists but its AST is NULL.
 */
const HParser* h_end_p();

/**
 * This parser always fails. 
 *
 * Result token type: NULL. Always.
 */
const HParser* h_nothing_p();

/**
 * Given a null-terminated list of parsers, apply each parser in order.
 * The parse succeeds only if all parsers succeed. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_sequence(const HParser* 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. 
 *
 * Result token type: The type of the first successful parser's result.
 */
const HParser* h_choice(const HParser* 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 longer than p2's
 *
 * Result token type: p1's result type.
 */
const HParser* h_butnot(const HParser* p1, const HParser* 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
 *
 * Result token type: p1's result type.
 */
const HParser* h_difference(const HParser* p1, const HParser* p2);

/**
 * Given two parsers, p1 and p2, this parser succeeds if *either* p1 or
 * p2 succeed, but not if they both do.
 *
 * Result token type: The type of the result of whichever parser succeeded.
 */
const HParser* h_xor(const HParser* p1, const HParser* p2);

/**
 * Given a parser, p, this parser succeeds for zero or more repetitions
 * of p. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_many(const HParser* p);

/**
 * Given a parser, p, this parser succeeds for one or more repetitions 
 * of p. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_many1(const HParser* p);

/**
 * Given a parser, p, this parser succeeds for exactly N repetitions 
 * of p. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_repeat_n(const HParser* p, const size_t n);

/**
 * Given a parser, p, this parser succeeds with the value p parsed or 
 * with an empty result. 
 *
 * Result token type: If p succeeded, the type of its result; if not, TT_NONE.
 */
const HParser* h_optional(const HParser* p);

/**
 * Given a parser, p, this parser succeeds if p succeeds, but doesn't 
 * include p's result in the result. 
 *
 * Result token type: None. The HParseResult exists but its AST is NULL.
 */
const HParser* h_ignore(const HParser* 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. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_sepBy(const HParser* p, const HParser* 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. 
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_sepBy1(const HParser* p, const HParser* sep);

/**
 * This parser always returns a zero length match, i.e., empty string. 
 *
 * Result token type: None. The HParseResult exists but its AST is NULL.
 */
const HParser* h_epsilon_p();

/**
 * This parser applies its first argument to read an unsigned integer
 * value, then applies its second argument that many times. length 
 * should parse an unsigned integer value; this is checked at runtime.
 * Specifically, the token_type of the returned token must be TT_UINT.
 * In future we might relax this to include TT_USER but don't count on it.
 *
 * Result token type: TT_SEQUENCE
 */
const HParser* h_length_value(const HParser* length, const HParser* value);

/**
 * 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. 
 *
 * attr_bool will check whether p's result exists and whether p's 
 * result AST exists; you do not need to check for this in your 
 * predicate function.
 * 
 * Result token type: p's result type if pred succeeded, NULL otherwise.
 */
const HParser* h_attr_bool(const HParser* p, HPredicate pred);

/**
 * The 'and' parser asserts that a conditional syntax is satisfied, 
 * but doesn't consume that conditional syntax. 
 * 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. 
 *
 * Result token type: None. The HParseResult exists but its AST is NULL.
 */
const HParser* h_and(const HParser* p);

/**
 * The 'not' parser asserts that a conditional syntax is *not* 
 * satisfied, but doesn't consume that conditional syntax.
 * 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.
 * 
 * Result token type: None. The HParseResult exists but its AST is NULL.
 */
const HParser* h_not(const HParser* 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.
 *
 * Result token type: the type of whatever parser is bound to it with
 * bind_indirect().
 */
HParser *h_indirect();

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

/**
 * Free the memory allocated to an HParseResult when it is no longer needed.
 */
void h_parse_result_free(HParseResult *result);

// Some debugging aids
/**
 * Format token into a compact unambiguous form. Useful for parser test cases.
 * Caller is responsible for freeing the result.
 */
char* h_write_result_unamb(const HParsedToken* tok);
/**
 * Format token to the given output stream. Indent starting at
 * [indent] spaces, with [delta] spaces between levels.
 */
void h_pprint(FILE* stream, const HParsedToken* tok, int indent, int delta);

/**
 * TODO: Document me
 */
HBitWriter *h_bit_writer_new(void);

/**
 * TODO: Document me
 */
void h_bit_writer_put(HBitWriter* w, unsigned long long data, size_t nbits);

/**
 * TODO: Document me
 * Must not free [w] until you're done with the result.
 * [len] is in bytes.
 */
const uint8_t *h_bit_writer_get_buffer(HBitWriter* w, size_t *len);

/**
 * TODO: Document me
 */
void h_bit_writer_free(HBitWriter* w);

#endif // #ifndef HAMMER_HAMMER__H