/// @file arabic.c
///
/// Functions for Arabic language.
///
/// Arabic characters are categorized into following types:
///
/// Isolated    - iso-8859-6 form         char denoted with  a_*
/// Initial     - unicode form-B start    char denoted with  a_i_*
/// Medial      - unicode form-B middle   char denoted with  a_m_*
/// Final       - unicode form-B final    char denoted with  a_f_*
/// Stand-Alone - unicode form-B isolated char denoted with  a_s_* (NOT USED)

#include <stdbool.h>

#include "nvim/vim.h"
#include "nvim/ascii.h"
#include "nvim/arabic.h"

// Arabic ISO-10646-1 character set definition

// Arabic ISO-8859-6 (subset of 10646; 0600 - 06FF)
#define a_COMMA                         0x060C
#define a_SEMICOLON                     0x061B
#define a_QUESTION                      0x061F
#define a_HAMZA                         0x0621
#define a_ALEF_MADDA                    0x0622
#define a_ALEF_HAMZA_ABOVE              0x0623
#define a_WAW_HAMZA                     0x0624
#define a_ALEF_HAMZA_BELOW              0x0625
#define a_YEH_HAMZA                     0x0626
#define a_ALEF                          0x0627
#define a_BEH                           0x0628
#define a_TEH_MARBUTA                   0x0629
#define a_TEH                           0x062a
#define a_THEH                          0x062b
#define a_JEEM                          0x062c
#define a_HAH                           0x062d
#define a_KHAH                          0x062e
#define a_DAL                           0x062f
#define a_THAL                          0x0630
#define a_REH                           0x0631
#define a_ZAIN                          0x0632
#define a_SEEN                          0x0633
#define a_SHEEN                         0x0634
#define a_SAD                           0x0635
#define a_DAD                           0x0636
#define a_TAH                           0x0637
#define a_ZAH                           0x0638
#define a_AIN                           0x0639
#define a_GHAIN                         0x063a
#define a_TATWEEL                       0x0640
#define a_FEH                           0x0641
#define a_QAF                           0x0642
#define a_KAF                           0x0643
#define a_LAM                           0x0644
#define a_MEEM                          0x0645
#define a_NOON                          0x0646
#define a_HEH                           0x0647
#define a_WAW                           0x0648
#define a_ALEF_MAKSURA                  0x0649
#define a_YEH                           0x064a

#define a_FATHATAN                      0x064b
#define a_DAMMATAN                      0x064c
#define a_KASRATAN                      0x064d
#define a_FATHA                         0x064e
#define a_DAMMA                         0x064f
#define a_KASRA                         0x0650
#define a_SHADDA                        0x0651
#define a_SUKUN                         0x0652

#define a_MADDA_ABOVE                   0x0653
#define a_HAMZA_ABOVE                   0x0654
#define a_HAMZA_BELOW                   0x0655

#define a_ZERO                          0x0660
#define a_ONE                           0x0661
#define a_TWO                           0x0662
#define a_THREE                         0x0663
#define a_FOUR                          0x0664
#define a_FIVE                          0x0665
#define a_SIX                           0x0666
#define a_SEVEN                         0x0667
#define a_EIGHT                         0x0668
#define a_NINE                          0x0669
#define a_PERCENT                       0x066a
#define a_DECIMAL                       0x066b
#define a_THOUSANDS                     0x066c
#define a_STAR                          0x066d
#define a_MINI_ALEF                     0x0670
// Rest of 8859-6 does not relate to Arabic

// Arabic Presentation Form-B (subset of 10646; FE70 - FEFF)
//
//  s -> isolated
//  i -> initial
//  m -> medial
//  f -> final
#define a_s_FATHATAN                    0xfe70
#define a_m_TATWEEL_FATHATAN            0xfe71
#define a_s_DAMMATAN                    0xfe72

#define a_s_KASRATAN                    0xfe74

#define a_s_FATHA                       0xfe76
#define a_m_FATHA                       0xfe77
#define a_s_DAMMA                       0xfe78
#define a_m_DAMMA                       0xfe79
#define a_s_KASRA                       0xfe7a
#define a_m_KASRA                       0xfe7b
#define a_s_SHADDA                      0xfe7c
#define a_m_SHADDA                      0xfe7d
#define a_s_SUKUN                       0xfe7e
#define a_m_SUKUN                       0xfe7f

#define a_s_HAMZA                       0xfe80
#define a_s_ALEF_MADDA                  0xfe81
#define a_f_ALEF_MADDA                  0xfe82
#define a_s_ALEF_HAMZA_ABOVE            0xfe83
#define a_f_ALEF_HAMZA_ABOVE            0xfe84
#define a_s_WAW_HAMZA                   0xfe85
#define a_f_WAW_HAMZA                   0xfe86
#define a_s_ALEF_HAMZA_BELOW            0xfe87
#define a_f_ALEF_HAMZA_BELOW            0xfe88
#define a_s_YEH_HAMZA                   0xfe89
#define a_f_YEH_HAMZA                   0xfe8a
#define a_i_YEH_HAMZA                   0xfe8b
#define a_m_YEH_HAMZA                   0xfe8c
#define a_s_ALEF                        0xfe8d
#define a_f_ALEF                        0xfe8e
#define a_s_BEH                         0xfe8f
#define a_f_BEH                         0xfe90
#define a_i_BEH                         0xfe91
#define a_m_BEH                         0xfe92
#define a_s_TEH_MARBUTA                 0xfe93
#define a_f_TEH_MARBUTA                 0xfe94
#define a_s_TEH                         0xfe95
#define a_f_TEH                         0xfe96
#define a_i_TEH                         0xfe97
#define a_m_TEH                         0xfe98
#define a_s_THEH                        0xfe99
#define a_f_THEH                        0xfe9a
#define a_i_THEH                        0xfe9b
#define a_m_THEH                        0xfe9c
#define a_s_JEEM                        0xfe9d
#define a_f_JEEM                        0xfe9e
#define a_i_JEEM                        0xfe9f
#define a_m_JEEM                        0xfea0
#define a_s_HAH                         0xfea1
#define a_f_HAH                         0xfea2
#define a_i_HAH                         0xfea3
#define a_m_HAH                         0xfea4
#define a_s_KHAH                        0xfea5
#define a_f_KHAH                        0xfea6
#define a_i_KHAH                        0xfea7
#define a_m_KHAH                        0xfea8
#define a_s_DAL                         0xfea9
#define a_f_DAL                         0xfeaa
#define a_s_THAL                        0xfeab
#define a_f_THAL                        0xfeac
#define a_s_REH                         0xfead
#define a_f_REH                         0xfeae
#define a_s_ZAIN                        0xfeaf
#define a_f_ZAIN                        0xfeb0
#define a_s_SEEN                        0xfeb1
#define a_f_SEEN                        0xfeb2
#define a_i_SEEN                        0xfeb3
#define a_m_SEEN                        0xfeb4
#define a_s_SHEEN                       0xfeb5
#define a_f_SHEEN                       0xfeb6
#define a_i_SHEEN                       0xfeb7
#define a_m_SHEEN                       0xfeb8
#define a_s_SAD                         0xfeb9
#define a_f_SAD                         0xfeba
#define a_i_SAD                         0xfebb
#define a_m_SAD                         0xfebc
#define a_s_DAD                         0xfebd
#define a_f_DAD                         0xfebe
#define a_i_DAD                         0xfebf
#define a_m_DAD                         0xfec0
#define a_s_TAH                         0xfec1
#define a_f_TAH                         0xfec2
#define a_i_TAH                         0xfec3
#define a_m_TAH                         0xfec4
#define a_s_ZAH                         0xfec5
#define a_f_ZAH                         0xfec6
#define a_i_ZAH                         0xfec7
#define a_m_ZAH                         0xfec8
#define a_s_AIN                         0xfec9
#define a_f_AIN                         0xfeca
#define a_i_AIN                         0xfecb
#define a_m_AIN                         0xfecc
#define a_s_GHAIN                       0xfecd
#define a_f_GHAIN                       0xfece
#define a_i_GHAIN                       0xfecf
#define a_m_GHAIN                       0xfed0
#define a_s_FEH                         0xfed1
#define a_f_FEH                         0xfed2
#define a_i_FEH                         0xfed3
#define a_m_FEH                         0xfed4
#define a_s_QAF                         0xfed5
#define a_f_QAF                         0xfed6
#define a_i_QAF                         0xfed7
#define a_m_QAF                         0xfed8
#define a_s_KAF                         0xfed9
#define a_f_KAF                         0xfeda
#define a_i_KAF                         0xfedb
#define a_m_KAF                         0xfedc
#define a_s_LAM                         0xfedd
#define a_f_LAM                         0xfede
#define a_i_LAM                         0xfedf
#define a_m_LAM                         0xfee0
#define a_s_MEEM                        0xfee1
#define a_f_MEEM                        0xfee2
#define a_i_MEEM                        0xfee3
#define a_m_MEEM                        0xfee4
#define a_s_NOON                        0xfee5
#define a_f_NOON                        0xfee6
#define a_i_NOON                        0xfee7
#define a_m_NOON                        0xfee8
#define a_s_HEH                         0xfee9
#define a_f_HEH                         0xfeea
#define a_i_HEH                         0xfeeb
#define a_m_HEH                         0xfeec
#define a_s_WAW                         0xfeed
#define a_f_WAW                         0xfeee
#define a_s_ALEF_MAKSURA                0xfeef
#define a_f_ALEF_MAKSURA                0xfef0
#define a_s_YEH                         0xfef1
#define a_f_YEH                         0xfef2
#define a_i_YEH                         0xfef3
#define a_m_YEH                         0xfef4
#define a_s_LAM_ALEF_MADDA_ABOVE        0xfef5
#define a_f_LAM_ALEF_MADDA_ABOVE        0xfef6
#define a_s_LAM_ALEF_HAMZA_ABOVE        0xfef7
#define a_f_LAM_ALEF_HAMZA_ABOVE        0xfef8
#define a_s_LAM_ALEF_HAMZA_BELOW        0xfef9
#define a_f_LAM_ALEF_HAMZA_BELOW        0xfefa
#define a_s_LAM_ALEF                    0xfefb
#define a_f_LAM_ALEF                    0xfefc

#define a_BYTE_ORDER_MARK               0xfeff


#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "arabic.c.generated.h"
#endif

// Returns true if c is an ISO-8859-6 shaped ARABIC letter (user entered).
static bool A_is_a(int cur_c)
{
  switch (cur_c) {
    case a_HAMZA:
    case a_ALEF_MADDA:
    case a_ALEF_HAMZA_ABOVE:
    case a_WAW_HAMZA:
    case a_ALEF_HAMZA_BELOW:
    case a_YEH_HAMZA:
    case a_ALEF:
    case a_BEH:
    case a_TEH_MARBUTA:
    case a_TEH:
    case a_THEH:
    case a_JEEM:
    case a_HAH:
    case a_KHAH:
    case a_DAL:
    case a_THAL:
    case a_REH:
    case a_ZAIN:
    case a_SEEN:
    case a_SHEEN:
    case a_SAD:
    case a_DAD:
    case a_TAH:
    case a_ZAH:
    case a_AIN:
    case a_GHAIN:
    case a_TATWEEL:
    case a_FEH:
    case a_QAF:
    case a_KAF:
    case a_LAM:
    case a_MEEM:
    case a_NOON:
    case a_HEH:
    case a_WAW:
    case a_ALEF_MAKSURA:
    case a_YEH:
      return true;
  }

  return false;
}

// Returns true if c is an Isolated Form-B ARABIC letter
static bool A_is_s(int cur_c)
{
  switch (cur_c) {
    case a_s_HAMZA:
    case a_s_ALEF_MADDA:
    case a_s_ALEF_HAMZA_ABOVE:
    case a_s_WAW_HAMZA:
    case a_s_ALEF_HAMZA_BELOW:
    case a_s_YEH_HAMZA:
    case a_s_ALEF:
    case a_s_BEH:
    case a_s_TEH_MARBUTA:
    case a_s_TEH:
    case a_s_THEH:
    case a_s_JEEM:
    case a_s_HAH:
    case a_s_KHAH:
    case a_s_DAL:
    case a_s_THAL:
    case a_s_REH:
    case a_s_ZAIN:
    case a_s_SEEN:
    case a_s_SHEEN:
    case a_s_SAD:
    case a_s_DAD:
    case a_s_TAH:
    case a_s_ZAH:
    case a_s_AIN:
    case a_s_GHAIN:
    case a_s_FEH:
    case a_s_QAF:
    case a_s_KAF:
    case a_s_LAM:
    case a_s_MEEM:
    case a_s_NOON:
    case a_s_HEH:
    case a_s_WAW:
    case a_s_ALEF_MAKSURA:
    case a_s_YEH:
      return true;
  }

  return false;
}

// Returns true if c is a Final shape of an ARABIC letter
static bool A_is_f(int cur_c)
{
  switch (cur_c) {
    case a_f_ALEF_MADDA:
    case a_f_ALEF_HAMZA_ABOVE:
    case a_f_WAW_HAMZA:
    case a_f_ALEF_HAMZA_BELOW:
    case a_f_YEH_HAMZA:
    case a_f_ALEF:
    case a_f_BEH:
    case a_f_TEH_MARBUTA:
    case a_f_TEH:
    case a_f_THEH:
    case a_f_JEEM:
    case a_f_HAH:
    case a_f_KHAH:
    case a_f_DAL:
    case a_f_THAL:
    case a_f_REH:
    case a_f_ZAIN:
    case a_f_SEEN:
    case a_f_SHEEN:
    case a_f_SAD:
    case a_f_DAD:
    case a_f_TAH:
    case a_f_ZAH:
    case a_f_AIN:
    case a_f_GHAIN:
    case a_f_FEH:
    case a_f_QAF:
    case a_f_KAF:
    case a_f_LAM:
    case a_f_MEEM:
    case a_f_NOON:
    case a_f_HEH:
    case a_f_WAW:
    case a_f_ALEF_MAKSURA:
    case a_f_YEH:
    case a_f_LAM_ALEF_MADDA_ABOVE:
    case a_f_LAM_ALEF_HAMZA_ABOVE:
    case a_f_LAM_ALEF_HAMZA_BELOW:
    case a_f_LAM_ALEF:
      return true;
  }
  return false;
}

// Change shape - from ISO-8859-6/Isolated to Form-B Isolated
static int chg_c_a2s(int cur_c)
{
  int tempc;

  switch (cur_c) {
    case a_HAMZA:
      tempc = a_s_HAMZA;
      break;

    case a_ALEF_MADDA:
      tempc = a_s_ALEF_MADDA;
      break;

    case a_ALEF_HAMZA_ABOVE:
      tempc = a_s_ALEF_HAMZA_ABOVE;
      break;

    case a_WAW_HAMZA:
      tempc = a_s_WAW_HAMZA;
      break;

    case a_ALEF_HAMZA_BELOW:
      tempc = a_s_ALEF_HAMZA_BELOW;
      break;

    case a_YEH_HAMZA:
      tempc = a_s_YEH_HAMZA;
      break;

    case a_ALEF:
      tempc = a_s_ALEF;
      break;

    case a_TEH_MARBUTA:
      tempc = a_s_TEH_MARBUTA;
      break;

    case a_DAL:
      tempc = a_s_DAL;
      break;

    case a_THAL:
      tempc = a_s_THAL;
      break;

    case a_REH:
      tempc = a_s_REH;
      break;

    case a_ZAIN:
      tempc = a_s_ZAIN;
      break;

    case a_TATWEEL: // exceptions
      tempc = cur_c;
      break;

    case a_WAW:
      tempc = a_s_WAW;
      break;

    case a_ALEF_MAKSURA:
      tempc = a_s_ALEF_MAKSURA;
      break;

    case a_BEH:
      tempc = a_s_BEH;
      break;

    case a_TEH:
      tempc = a_s_TEH;
      break;

    case a_THEH:
      tempc = a_s_THEH;
      break;

    case a_JEEM:
      tempc = a_s_JEEM;
      break;

    case a_HAH:
      tempc = a_s_HAH;
      break;

    case a_KHAH:
      tempc = a_s_KHAH;
      break;

    case a_SEEN:
      tempc = a_s_SEEN;
      break;

    case a_SHEEN:
      tempc = a_s_SHEEN;
      break;

    case a_SAD:
      tempc = a_s_SAD;
      break;

    case a_DAD:
      tempc = a_s_DAD;
      break;

    case a_TAH:
      tempc = a_s_TAH;
      break;

    case a_ZAH:
      tempc = a_s_ZAH;
      break;

    case a_AIN:
      tempc = a_s_AIN;
      break;

    case a_GHAIN:
      tempc = a_s_GHAIN;
      break;

    case a_FEH:
      tempc = a_s_FEH;
      break;

    case a_QAF:
      tempc = a_s_QAF;
      break;

    case a_KAF:
      tempc = a_s_KAF;
      break;

    case a_LAM:
      tempc = a_s_LAM;
      break;

    case a_MEEM:
      tempc = a_s_MEEM;
      break;

    case a_NOON:
      tempc = a_s_NOON;
      break;

    case a_HEH:
      tempc = a_s_HEH;
      break;

    case a_YEH:
      tempc = a_s_YEH;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from ISO-8859-6/Isolated to Initial
static int chg_c_a2i(int cur_c)
{
  int tempc;

  switch (cur_c) {
    case a_YEH_HAMZA:
      tempc = a_i_YEH_HAMZA;
      break;

    case a_HAMZA: // exceptions
      tempc = a_s_HAMZA;
      break;

    case a_ALEF_MADDA: // exceptions
      tempc = a_s_ALEF_MADDA;
      break;

    case a_ALEF_HAMZA_ABOVE: // exceptions
      tempc = a_s_ALEF_HAMZA_ABOVE;
      break;

    case a_WAW_HAMZA: // exceptions
      tempc = a_s_WAW_HAMZA;
      break;

    case a_ALEF_HAMZA_BELOW: // exceptions
      tempc = a_s_ALEF_HAMZA_BELOW;
      break;

    case a_ALEF: // exceptions
      tempc = a_s_ALEF;
      break;

    case a_TEH_MARBUTA: // exceptions
      tempc = a_s_TEH_MARBUTA;
      break;

    case a_DAL: // exceptions
      tempc = a_s_DAL;
      break;

    case a_THAL: // exceptions
      tempc = a_s_THAL;
      break;

    case a_REH: // exceptions
      tempc = a_s_REH;
      break;

    case a_ZAIN: // exceptions
      tempc = a_s_ZAIN;
      break;

    case a_TATWEEL: // exceptions
      tempc = cur_c;
      break;

    case a_WAW: // exceptions
      tempc = a_s_WAW;
      break;

    case a_ALEF_MAKSURA: // exceptions
      tempc = a_s_ALEF_MAKSURA;
      break;

    case a_BEH:
      tempc = a_i_BEH;
      break;

    case a_TEH:
      tempc = a_i_TEH;
      break;

    case a_THEH:
      tempc = a_i_THEH;
      break;

    case a_JEEM:
      tempc = a_i_JEEM;
      break;

    case a_HAH:
      tempc = a_i_HAH;
      break;

    case a_KHAH:
      tempc = a_i_KHAH;
      break;

    case a_SEEN:
      tempc = a_i_SEEN;
      break;

    case a_SHEEN:
      tempc = a_i_SHEEN;
      break;

    case a_SAD:
      tempc = a_i_SAD;
      break;

    case a_DAD:
      tempc = a_i_DAD;
      break;

    case a_TAH:
      tempc = a_i_TAH;
      break;

    case a_ZAH:
      tempc = a_i_ZAH;
      break;

    case a_AIN:
      tempc = a_i_AIN;
      break;

    case a_GHAIN:
      tempc = a_i_GHAIN;
      break;

    case a_FEH:
      tempc = a_i_FEH;
      break;

    case a_QAF:
      tempc = a_i_QAF;
      break;

    case a_KAF:
      tempc = a_i_KAF;
      break;

    case a_LAM:
      tempc = a_i_LAM;
      break;

    case a_MEEM:
      tempc = a_i_MEEM;
      break;

    case a_NOON:
      tempc = a_i_NOON;
      break;

    case a_HEH:
      tempc = a_i_HEH;
      break;

    case a_YEH:
      tempc = a_i_YEH;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from ISO-8859-6/Isolated to Medial
static int chg_c_a2m(int cur_c)
{
  int tempc;

  switch (cur_c) {
    case a_HAMZA: // exception
      tempc = a_s_HAMZA;
      break;

    case a_ALEF_MADDA: // exception
      tempc = a_f_ALEF_MADDA;
      break;

    case a_ALEF_HAMZA_ABOVE: // exception
      tempc = a_f_ALEF_HAMZA_ABOVE;
      break;

    case a_WAW_HAMZA: // exception
      tempc = a_f_WAW_HAMZA;
      break;

    case a_ALEF_HAMZA_BELOW: // exception
      tempc = a_f_ALEF_HAMZA_BELOW;
      break;

    case a_YEH_HAMZA:
      tempc = a_m_YEH_HAMZA;
      break;

    case a_ALEF: // exception
      tempc = a_f_ALEF;
      break;

    case a_BEH:
      tempc = a_m_BEH;
      break;

    case a_TEH_MARBUTA: // exception
      tempc = a_f_TEH_MARBUTA;
      break;

    case a_TEH:
      tempc = a_m_TEH;
      break;

    case a_THEH:
      tempc = a_m_THEH;
      break;

    case a_JEEM:
      tempc = a_m_JEEM;
      break;

    case a_HAH:
      tempc = a_m_HAH;
      break;

    case a_KHAH:
      tempc = a_m_KHAH;
      break;

    case a_DAL: // exception
      tempc = a_f_DAL;
      break;

    case a_THAL: // exception
      tempc = a_f_THAL;
      break;

    case a_REH: // exception
      tempc = a_f_REH;
      break;

    case a_ZAIN: // exception
      tempc = a_f_ZAIN;
      break;

    case a_SEEN:
      tempc = a_m_SEEN;
      break;

    case a_SHEEN:
      tempc = a_m_SHEEN;
      break;

    case a_SAD:
      tempc = a_m_SAD;
      break;

    case a_DAD:
      tempc = a_m_DAD;
      break;

    case a_TAH:
      tempc = a_m_TAH;
      break;

    case a_ZAH:
      tempc = a_m_ZAH;
      break;

    case a_AIN:
      tempc = a_m_AIN;
      break;

    case a_GHAIN:
      tempc = a_m_GHAIN;
      break;

    case a_TATWEEL: // exception
      tempc = cur_c;
      break;

    case a_FEH:
      tempc = a_m_FEH;
      break;

    case a_QAF:
      tempc = a_m_QAF;
      break;

    case a_KAF:
      tempc = a_m_KAF;
      break;

    case a_LAM:
      tempc = a_m_LAM;
      break;

    case a_MEEM:
      tempc = a_m_MEEM;
      break;

    case a_NOON:
      tempc = a_m_NOON;
      break;

    case a_HEH:
      tempc = a_m_HEH;
      break;

    case a_WAW: // exception
      tempc = a_f_WAW;
      break;

    case a_ALEF_MAKSURA: // exception
      tempc = a_f_ALEF_MAKSURA;
      break;

    case a_YEH:
      tempc = a_m_YEH;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from ISO-8859-6/Isolated to final
static int chg_c_a2f(int cur_c)
{
  int tempc;

  // NOTE: these encodings need to be accounted for
  //
  // a_f_ALEF_MADDA;
  // a_f_ALEF_HAMZA_ABOVE;
  // a_f_ALEF_HAMZA_BELOW;
  // a_f_LAM_ALEF_MADDA_ABOVE;
  // a_f_LAM_ALEF_HAMZA_ABOVE;
  // a_f_LAM_ALEF_HAMZA_BELOW;

  switch (cur_c) {
    case a_HAMZA: // exception
      tempc = a_s_HAMZA;
      break;

    case a_ALEF_MADDA:
      tempc = a_f_ALEF_MADDA;
      break;

    case a_ALEF_HAMZA_ABOVE:
      tempc = a_f_ALEF_HAMZA_ABOVE;
      break;

    case a_WAW_HAMZA:
      tempc = a_f_WAW_HAMZA;
      break;

    case a_ALEF_HAMZA_BELOW:
      tempc = a_f_ALEF_HAMZA_BELOW;
      break;

    case a_YEH_HAMZA:
      tempc = a_f_YEH_HAMZA;
      break;

    case a_ALEF:
      tempc = a_f_ALEF;
      break;

    case a_BEH:
      tempc = a_f_BEH;
      break;

    case a_TEH_MARBUTA:
      tempc = a_f_TEH_MARBUTA;
      break;

    case a_TEH:
      tempc = a_f_TEH;
      break;

    case a_THEH:
      tempc = a_f_THEH;
      break;

    case a_JEEM:
      tempc = a_f_JEEM;
      break;

    case a_HAH:
      tempc = a_f_HAH;
      break;

    case a_KHAH:
      tempc = a_f_KHAH;
      break;

    case a_DAL:
      tempc = a_f_DAL;
      break;

    case a_THAL:
      tempc = a_f_THAL;
      break;

    case a_REH:
      tempc = a_f_REH;
      break;

    case a_ZAIN:
      tempc = a_f_ZAIN;
      break;

    case a_SEEN:
      tempc = a_f_SEEN;
      break;

    case a_SHEEN:
      tempc = a_f_SHEEN;
      break;

    case a_SAD:
      tempc = a_f_SAD;
      break;

    case a_DAD:
      tempc = a_f_DAD;
      break;

    case a_TAH:
      tempc = a_f_TAH;
      break;

    case a_ZAH:
      tempc = a_f_ZAH;
      break;

    case a_AIN:
      tempc = a_f_AIN;
      break;

    case a_GHAIN:
      tempc = a_f_GHAIN;
      break;

    case a_TATWEEL: // exception
      tempc = cur_c;
      break;

    case a_FEH:
      tempc = a_f_FEH;
      break;

    case a_QAF:
      tempc = a_f_QAF;
      break;

    case a_KAF:
      tempc = a_f_KAF;
      break;

    case a_LAM:
      tempc = a_f_LAM;
      break;

    case a_MEEM:
      tempc = a_f_MEEM;
      break;

    case a_NOON:
      tempc = a_f_NOON;
      break;

    case a_HEH:
      tempc = a_f_HEH;
      break;

    case a_WAW:
      tempc = a_f_WAW;
      break;

    case a_ALEF_MAKSURA:
      tempc = a_f_ALEF_MAKSURA;
      break;

    case a_YEH:
      tempc = a_f_YEH;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from Initial to Medial
static int chg_c_i2m(int cur_c)
{
  int tempc;

  switch (cur_c) {
    case a_i_YEH_HAMZA:
      tempc = a_m_YEH_HAMZA;
      break;

    case a_i_BEH:
      tempc = a_m_BEH;
      break;

    case a_i_TEH:
      tempc = a_m_TEH;
      break;

    case a_i_THEH:
      tempc = a_m_THEH;
      break;

    case a_i_JEEM:
      tempc = a_m_JEEM;
      break;

    case a_i_HAH:
      tempc = a_m_HAH;
      break;

    case a_i_KHAH:
      tempc = a_m_KHAH;
      break;

    case a_i_SEEN:
      tempc = a_m_SEEN;
      break;

    case a_i_SHEEN:
      tempc = a_m_SHEEN;
      break;

    case a_i_SAD:
      tempc = a_m_SAD;
      break;

    case a_i_DAD:
      tempc = a_m_DAD;
      break;

    case a_i_TAH:
      tempc = a_m_TAH;
      break;

    case a_i_ZAH:
      tempc = a_m_ZAH;
      break;

    case a_i_AIN:
      tempc = a_m_AIN;
      break;

    case a_i_GHAIN:
      tempc = a_m_GHAIN;
      break;

    case a_i_FEH:
      tempc = a_m_FEH;
      break;

    case a_i_QAF:
      tempc = a_m_QAF;
      break;

    case a_i_KAF:
      tempc = a_m_KAF;
      break;

    case a_i_LAM:
      tempc = a_m_LAM;
      break;

    case a_i_MEEM:
      tempc = a_m_MEEM;
      break;

    case a_i_NOON:
      tempc = a_m_NOON;
      break;

    case a_i_HEH:
      tempc = a_m_HEH;
      break;

    case a_i_YEH:
      tempc = a_m_YEH;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from Final to Medial
static int chg_c_f2m(int cur_c)
{
  int tempc;

  switch (cur_c) {
    // NOTE: these encodings are multi-positional, no ?
    // case a_f_ALEF_MADDA:
    // case a_f_ALEF_HAMZA_ABOVE:
    // case a_f_ALEF_HAMZA_BELOW:
    case a_f_YEH_HAMZA:
      tempc = a_m_YEH_HAMZA;
      break;

    case a_f_WAW_HAMZA: // exceptions
    case a_f_ALEF:
    case a_f_TEH_MARBUTA:
    case a_f_DAL:
    case a_f_THAL:
    case a_f_REH:
    case a_f_ZAIN:
    case a_f_WAW:
    case a_f_ALEF_MAKSURA:
      tempc = cur_c;
      break;

    case a_f_BEH:
      tempc = a_m_BEH;
      break;

    case a_f_TEH:
      tempc = a_m_TEH;
      break;

    case a_f_THEH:
      tempc = a_m_THEH;
      break;

    case a_f_JEEM:
      tempc = a_m_JEEM;
      break;

    case a_f_HAH:
      tempc = a_m_HAH;
      break;

    case a_f_KHAH:
      tempc = a_m_KHAH;
      break;

    case a_f_SEEN:
      tempc = a_m_SEEN;
      break;

    case a_f_SHEEN:
      tempc = a_m_SHEEN;
      break;

    case a_f_SAD:
      tempc = a_m_SAD;
      break;

    case a_f_DAD:
      tempc = a_m_DAD;
      break;

    case a_f_TAH:
      tempc = a_m_TAH;
      break;

    case a_f_ZAH:
      tempc = a_m_ZAH;
      break;

    case a_f_AIN:
      tempc = a_m_AIN;
      break;

    case a_f_GHAIN:
      tempc = a_m_GHAIN;
      break;

    case a_f_FEH:
      tempc = a_m_FEH;
      break;

    case a_f_QAF:
      tempc = a_m_QAF;
      break;

    case a_f_KAF:
      tempc = a_m_KAF;
      break;

    case a_f_LAM:
      tempc = a_m_LAM;
      break;

    case a_f_MEEM:
      tempc = a_m_MEEM;
      break;

    case a_f_NOON:
      tempc = a_m_NOON;
      break;

    case a_f_HEH:
      tempc = a_m_HEH;
      break;

    case a_f_YEH:
      tempc = a_m_YEH;
      break;

    // NOTE: these encodings are multi-positional, no ?
    //   case a_f_LAM_ALEF_MADDA_ABOVE:
    //   case a_f_LAM_ALEF_HAMZA_ABOVE:
    //   case a_f_LAM_ALEF_HAMZA_BELOW:
    //   case a_f_LAM_ALEF:
    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from Combination (2 char) to an Isolated.
static int chg_c_laa2i(int hid_c)
{
  int tempc;

  switch (hid_c) {
    case a_ALEF_MADDA:
      tempc = a_s_LAM_ALEF_MADDA_ABOVE;
      break;

    case a_ALEF_HAMZA_ABOVE:
      tempc = a_s_LAM_ALEF_HAMZA_ABOVE;
      break;

    case a_ALEF_HAMZA_BELOW:
      tempc = a_s_LAM_ALEF_HAMZA_BELOW;
      break;

    case a_ALEF:
      tempc = a_s_LAM_ALEF;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Change shape - from Combination-Isolated to Final.
static int chg_c_laa2f(int hid_c)
{
  int tempc;

  switch (hid_c) {
    case a_ALEF_MADDA:
      tempc = a_f_LAM_ALEF_MADDA_ABOVE;
      break;

    case a_ALEF_HAMZA_ABOVE:
      tempc = a_f_LAM_ALEF_HAMZA_ABOVE;
      break;

    case a_ALEF_HAMZA_BELOW:
      tempc = a_f_LAM_ALEF_HAMZA_BELOW;
      break;

    case a_ALEF:
      tempc = a_f_LAM_ALEF;
      break;

    default:
      tempc = 0;
  }

  return tempc;
}

// Do "half-shaping" on character "c". Return zero if no shaping.
static int half_shape(int c)
{
  if (A_is_a(c)) {
    return chg_c_a2i(c);
  }

  if (A_is_valid(c) && A_is_f(c)) {
    return chg_c_f2m(c);
  }
  return 0;
}

// Do Arabic shaping on character "c".  Returns the shaped character.
// out:    "ccp" points to the first byte of the character to be shaped.
// in/out: "c1p" points to the first composing char for "c".
// in:     "prev_c"  is the previous character (not shaped)
// in:     "prev_c1" is the first composing char for the previous char
//  	     (not shaped)
// in:     "next_c"  is the next character (not shaped).
int arabic_shape(int c, int *ccp, int *c1p, int prev_c, int prev_c1,
                 int next_c)
{
  // Deal only with Arabic character, pass back all others
  if (!A_is_ok(c)) {
    return c;
  }

  // half-shape current and previous character
  int shape_c = half_shape(prev_c);

  // Save away current character
  int curr_c = c;

  int curr_laa = A_firstc_laa(c, *c1p);
  int prev_laa = A_firstc_laa(prev_c, prev_c1);

  if (curr_laa) {
    if (A_is_valid(prev_c) && !A_is_f(shape_c) && !A_is_s(shape_c) &&
        !prev_laa) {
      curr_c = chg_c_laa2f(curr_laa);
    } else {
      curr_c = chg_c_laa2i(curr_laa);
    }

    // Remove the composing character
    *c1p = 0;
  } else if (!A_is_valid(prev_c) && A_is_valid(next_c)) {
    curr_c = chg_c_a2i(c);
  } else if (!shape_c || A_is_f(shape_c) || A_is_s(shape_c) || prev_laa) {
    curr_c = A_is_valid(next_c) ? chg_c_a2i(c) : chg_c_a2s(c);
  } else if (A_is_valid(next_c)) {
    curr_c = A_is_iso(c) ? chg_c_a2m(c) : chg_c_i2m(c);
  } else if (A_is_valid(prev_c)) {
    curr_c = chg_c_a2f(c);
  } else {
    curr_c = chg_c_a2s(c);
  }

  // Sanity check -- curr_c should, in the future, never be 0.
  // We should, in the future, insert a fatal error here.
  if (curr_c == NUL) {
    curr_c = c;
  }

  if ((curr_c != c) && (ccp != NULL)) {
    char_u buf[MB_MAXBYTES + 1];

    // Update the first byte of the character
    (*mb_char2bytes)(curr_c, buf);
    *ccp = buf[0];
  }

  // Return the shaped character
  return curr_c;
}

/// Check whether we are dealing with Arabic combining characters.
/// Note: these are NOT really composing characters!
///
/// @param one First character.
/// @param two Character just after "one".
bool arabic_combine(int one, int two)
{
  if (one == a_LAM) {
    return arabic_maycombine(two);
  }
  return false;
}

/// Check whether we are dealing with a character that could be regarded as an
/// Arabic combining character, need to check the character before this.
bool arabic_maycombine(int two)
{
  if (p_arshape && !p_tbidi) {
    return two == a_ALEF_MADDA
      || two == a_ALEF_HAMZA_ABOVE
      || two == a_ALEF_HAMZA_BELOW
      || two == a_ALEF;
  }
  return false;
}

// A_firstc_laa returns first character of LAA combination if it ex.ists
// in: "c" base character
// in: "c1" first composing character
static int A_firstc_laa(int c, int c1)
{
  if ((c1 != NUL) && (c == a_LAM) && !A_is_harakat(c1)) {
    return c1;
  }
  return 0;
}

// A_is_harakat returns true if 'c' is an Arabic Harakat character.
//     (harakat/tanween)
static bool A_is_harakat(int c)
{
  return c >= a_FATHATAN && c <= a_SUKUN;
}

// A_is_iso returns true if 'c' is an Arabic ISO-8859-6 character.
//     (alphabet/number/punctuation)
static bool A_is_iso(int c)
{
  return (c >= a_HAMZA && c <= a_GHAIN) ||
         (c >= a_TATWEEL && c <= a_HAMZA_BELOW) ||
         c == a_MINI_ALEF;
}

// A_is_formb returns true if 'c' is an Arabic 10646-1 FormB character.
//     (alphabet/number/punctuation)
static bool A_is_formb(int c)
{
  return (c >= a_s_FATHATAN && c <= a_s_DAMMATAN) ||
         c == a_s_KASRATAN ||
         (c >= a_s_FATHA && c <= a_f_LAM_ALEF) ||
         c == a_BYTE_ORDER_MARK;
}

// A_is_ok returns true if 'c' is an Arabic 10646 (8859-6 or Form-B).
static bool A_is_ok(int c)
{
  return A_is_iso(c) || A_is_formb(c);
}

// A_is_valid returns true if 'c' is an Arabic 10646 (8859-6 or Form-B),
// with some exceptions/exclusions.
static bool A_is_valid(int c)
{
  return A_is_ok(c) && !A_is_special(c);
}

// A_is_special returns true if 'c' is not a special Arabic character.
// Specials don't adhere to most of the rules.
static bool A_is_special(int c)
{
  return c == a_HAMZA || c == a_s_HAMZA;
}
