// NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE
//
// This is NOT the original regular expression code as written by Henry
// Spencer.  This code has been modified specifically for use with Vim, and
// should not be used apart from compiling Vim.  If you want a good regular
// expression library, get the original code.
//
// NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE

#pragma once

#include <stdbool.h>
#include <stdint.h>

#include "nvim/pos_defs.h"
#include "nvim/types_defs.h"

/// Used for "magic_overruled".
typedef enum {
  OPTION_MAGIC_NOT_SET,  ///< p_magic not overruled
  OPTION_MAGIC_ON,       ///< magic on inside regexp
  OPTION_MAGIC_OFF,      ///< magic off inside regexp
} optmagic_T;

/// Magicness of a pattern, used by regexp code.
/// The order and values matter:
///  magic <= MAGIC_OFF includes MAGIC_NONE
///  magic >= MAGIC_ON  includes MAGIC_ALL
typedef enum {
  MAGIC_NONE = 1,  ///< "\V" very unmagic
  MAGIC_OFF = 2,   ///< "\M" or 'magic' off
  MAGIC_ON = 3,    ///< "\m" or 'magic'
  MAGIC_ALL = 4,   ///< "\v" very magic
} magic_T;

/// The number of sub-matches is limited to 10.
/// The first one (index 0) is the whole match, referenced with "\0".
/// The second one (index 1) is the first sub-match, referenced with "\1".
/// This goes up to the tenth (index 9), referenced with "\9".
enum { NSUBEXP = 10, };

/// In the NFA engine: how many braces are allowed.
/// TODO(RE): Use dynamic memory allocation instead of static, like here
enum { NFA_MAX_BRACES = 20, };

/// In the NFA engine: how many states are allowed.
enum {
  NFA_MAX_STATES = 100000,
  NFA_TOO_EXPENSIVE = -1,
};

/// Which regexp engine to use? Needed for vim_regcomp().
/// Must match with 'regexpengine'.
enum {
  AUTOMATIC_ENGINE    = 0,
  BACKTRACKING_ENGINE = 1,
  NFA_ENGINE          = 2,
};

typedef struct regengine regengine_T;
typedef struct regprog regprog_T;
typedef struct reg_extmatch reg_extmatch_T;

/// Structure to be used for multi-line matching.
/// Sub-match "no" starts in line "startpos[no].lnum" column "startpos[no].col"
/// and ends in line "endpos[no].lnum" just before column "endpos[no].col".
/// The line numbers are relative to the first line, thus startpos[0].lnum is
/// always 0.
/// When there is no match, the line number is -1.
typedef struct {
  regprog_T *regprog;
  lpos_T startpos[NSUBEXP];
  lpos_T endpos[NSUBEXP];

  colnr_T rmm_matchcol;  ///< match start without "\zs"
  int rmm_ic;
  colnr_T rmm_maxcol;  ///< when not zero: maximum column
} regmmatch_T;

#include "nvim/buffer_defs.h"

/// Structure returned by vim_regcomp() to pass on to vim_regexec().
/// This is the general structure. For the actual matcher, two specific
/// structures are used. See code below.
struct regprog {
  regengine_T *engine;
  unsigned regflags;
  unsigned re_engine;  ///< Automatic, backtracking or NFA engine.
  unsigned re_flags;   ///< Second argument for vim_regcomp().
  bool re_in_use;      ///< prog is being executed
};

/// Structure used by the back track matcher.
/// These fields are only to be used in regexp.c!
/// See regexp.c for an explanation.
typedef struct {
  // These four members implement regprog_T.
  regengine_T *engine;
  unsigned regflags;
  unsigned re_engine;
  unsigned re_flags;
  bool re_in_use;

  int regstart;
  uint8_t reganch;
  uint8_t *regmust;
  int regmlen;
  uint8_t reghasz;
  uint8_t program[];
} bt_regprog_T;

/// Structure representing a NFA state.
/// An NFA state may have no outgoing edge, when it is a NFA_MATCH state.
typedef struct nfa_state nfa_state_T;
struct nfa_state {
  int c;
  nfa_state_T *out;
  nfa_state_T *out1;
  int id;
  int lastlist[2];  ///< 0: normal, 1: recursive
  int val;
};

/// Structure used by the NFA matcher.
typedef struct {
  // These four members implement regprog_T.
  regengine_T *engine;
  unsigned regflags;
  unsigned re_engine;
  unsigned re_flags;
  bool re_in_use;

  nfa_state_T *start;   ///< points into state[]

  int reganch;          ///< pattern starts with ^
  int regstart;         ///< char at start of pattern
  uint8_t *match_text;  ///< plain text to match with

  int has_zend;         ///< pattern contains \ze
  int has_backref;      ///< pattern contains \1 .. \9
  int reghasz;
  char *pattern;
  int nsubexp;          ///< number of ()
  int nstate;
  nfa_state_T state[];
} nfa_regprog_T;

/// Structure to be used for single-line matching.
/// Sub-match "no" starts at "startp[no]" and ends just before "endp[no]".
/// When there is no match, the pointer is NULL.
typedef struct {
  regprog_T *regprog;
  char *startp[NSUBEXP];
  char *endp[NSUBEXP];

  colnr_T rm_matchcol;  ///< match start without "\zs"
  bool rm_ic;
} regmatch_T;

/// Structure used to store external references: "\z\(\)" to "\z\1".
/// Use a reference count to avoid the need to copy this around.  When it goes
/// from 1 to zero the matches need to be freed.
struct reg_extmatch {
  int16_t refcnt;
  uint8_t *matches[NSUBEXP];
};

struct regengine {
  /// bt_regcomp or nfa_regcomp
  regprog_T *(*regcomp)(uint8_t *, int);
  /// bt_regfree or nfa_regfree
  void (*regfree)(regprog_T *);
  /// bt_regexec_nl or nfa_regexec_nl
  int (*regexec_nl)(regmatch_T *, uint8_t *, colnr_T, bool);
  /// bt_regexec_mult or nfa_regexec_mult
  int (*regexec_multi)(regmmatch_T *, win_T *, buf_T *, linenr_T, colnr_T, proftime_T *, int *);
  // uint8_t *expr;
};

/// Flags used by vim_regsub() and vim_regsub_both()
enum {
  REGSUB_COPY      = 1,
  REGSUB_MAGIC     = 2,
  REGSUB_BACKSLASH = 4,
};