/* Decode a Game Genie code into an M68000 address/data pair.
 * The Game Genie code is made of the characters
 * ABCDEFGHJKLMNPRSTVWXYZ0123456789 (notice the missing I, O, Q and U).
 * Where A = 00000, B = 00001, C = 00010, ... , on to 9 = 11111.
 * 
 * These come out to a very scrambled bit pattern like this:
 * (SCRA-MBLE is just an example)
 *
 *   S     C     R     A  -  M     B     L     E
 * 01111 00010 01110 00000 01011 00001 01010 00100
 * ijklm nopIJ KLMNO PABCD EFGHd efgha bcQRS TUVWX
 *
 * Our goal is to rearrange that to this:
 *
 * 0000 0101 1001 1100 0100 0100 : 1011 0000 0111 1000
 * ABCD EFGH IJKL MNOP QRST UVWX : abcd efgh ijkl mnop
 *
 * which in Hexadecimal is 059C44:B078. Simple, huh? ;)
 *
 * So, then, we dutifully change memory location 059C44 to B078!
 * (of course, that's handled by a different source file :)
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <windows.h>
#include "G_main.h"
#include "ggenie.h"
#include "mem_M68K.h"
#include "cpu_68k.h"
#include "rom.h"

struct GG_Code Liste_GG[256] = {{"\0", "\0", 0, 0, 0, 0}};
static char genie_chars[] = "AaBbCcDdEeFfGgHhJjKkLlMmNnPpRrSsTtVvWwXxYyZz0O1I2233445566778899";
char Patch_Dir[1024] = "\\";

/* genie_decode
 * This function converts a Game Genie code to an address:data pair.
 * The code is given as an 8-character string, like "BJX0SA1C". It need not
 * be null terminated, since only the first 8 characters are taken. It is
 * assumed that the code is already made of valid characters, i.e. there are no
 * Q's, U's, or symbols. If such a character is
 * encountered, the function will return with a warning on stderr.
 *
 * The resulting address:data pair is returned in the struct patch pointed to
 * by result. If an error results, both the address and data will be set to -1.
 */

static void genie_decode(const char* code, struct patch* result)
{
  int i = 0, n;
  char* x;

  for(; i < 8; ++i)
  {
    /* If strchr returns NULL, we were given a bad character */
    if(!(x = strchr(genie_chars, code[i])))
    {
      result->addr = -1; result->data = -1;
      return;
    }
    n = (x - genie_chars) >> 1;
    /* Now, based on which character this is, fit it into the result */
    switch(i)
    {
    case 0:
      /* ____ ____ ____ ____ ____ ____ : ____ ____ ABCD E___ */
      result->data |= n << 3;
      break;
    case 1:
      /* ____ ____ DE__ ____ ____ ____ : ____ ____ ____ _ABC */
      result->data |= n >> 2;
      result->addr |= (n & 3) << 14;
      break;
    case 2:
      /* ____ ____ __AB CDE_ ____ ____ : ____ ____ ____ ____ */
      result->addr |= n << 9;
      break;
    case 3:
      /* BCDE ____ ____ ___A ____ ____ : ____ ____ ____ ____ */
      result->addr |= (n & 0xF) << 20 | (n >> 4) << 8;
      break;
    case 4:
      /* ____ ABCD ____ ____ ____ ____ : ___E ____ ____ ____ */
      result->data |= (n & 1) << 12;
      result->addr |= (n >> 1) << 16;
      break;
    case 5:
      /* ____ ____ ____ ____ ____ ____ : E___ ABCD ____ ____ */
      result->data |= (n & 1) << 15 | (n >> 1) << 8;
      break;
    case 6:
      /* ____ ____ ____ ____ CDE_ ____ : _AB_ ____ ____ ____ */
      result->data |= (n >> 3) << 13;
      result->addr |= (n & 7) << 5;
      break;
    case 7:
      /* ____ ____ ____ ____ ___A BCDE : ____ ____ ____ ____ */
      result->addr |= n;
      break;
    }
    /* Go around again */
  }
  return;
}

/* "Decode" an address/data pair into a structure. This is for "012345:ABCD"
 * type codes. You're more likely to find Genie codes circulating around, but
 * there's a chance you could come on to one of these. Which is nice, since
 * they're MUCH easier to implement ;) Once again, the input should be depunc-
 * tuated already. */

static char hex_chars[] = "00112233445566778899AaBbCcDdEeFf";

static void hex_decode(const char *code, struct patch *result)
{
  char *x;
  int i;
  /* 6 digits for address */
  for(i = 0; i < 6; ++i)
    {
      if(!(x = strchr(hex_chars, code[i])))
      {
	result->addr = result->data = -1;
	return;
      }
      result->addr = (result->addr << 4) | ((x - hex_chars) >> 1);
    }
  /* 4 digits for data */
  for(i = 6; i < 10; ++i)
    {
      if(!(x = strchr(hex_chars, code[i])))
      {
	result->addr = result->data = -1;
	return;
      }
      result->data = (result->data << 4) | ((x - hex_chars) >> 1);
    }
}

/* THIS is the function you call from the MegaDrive or whatever. This figures
 * out whether it's a genie or hex code, depunctuates it, and calls the proper
 * decoder. */
void decode(const char* code, struct patch* result)
{
  int len = strlen(code), i, j;
  char code_to_pass[16], *x;
  const char *ad, *da;
  int adl, dal;

  /* Initialize the result */
  result->addr = result->data = 0;
  
  /* If it's 9 chars long and the 5th is a hyphen, we have a Game Genie
   * code. */

    if(len == 9 && code[4] == '-')
    {
      /* Remove the hyphen and pass to genie_decode */
      code_to_pass[0] = code[0];
      code_to_pass[1] = code[1];
      code_to_pass[2] = code[2];
      code_to_pass[3] = code[3];
      code_to_pass[4] = code[5];
      code_to_pass[5] = code[6];
      code_to_pass[6] = code[7];
      code_to_pass[7] = code[8];
      code_to_pass[8] = '\0';
      genie_decode(code_to_pass, result);
      return;
    }

  /* Otherwise, we assume it's a hex code.
   * Find the colon so we know where address ends and data starts. If there's
   * no colon, then we haven't a code at all! */
  if(!(x = strchr(code, ':'))) goto bad_code;
  ad = code; da = x + 1; adl = x - code; dal = len - adl - 1;

  /* If a section is empty or too long, toss it */
  if(adl == 0 || adl > 6 || dal == 0 || dal > 4) goto bad_code;

  /* Pad the address with zeros, then fill it with the value */
  for(i = 0; i < (6 - adl); ++i) code_to_pass[i] = '0';
  for(j = 0; i < 6; ++i, ++j) code_to_pass[i] = ad[j];

  /* Do the same for data */
  for(i = 6; i < (10 - dal); ++i) code_to_pass[i] = '0';
  for(j = 0; i < 10; ++i, ++j) code_to_pass[i] = da[j];

  code_to_pass[10] = '\0';

  /* Decode and goodbye */
  hex_decode(code_to_pass, result);
  return;

bad_code:

  /* AGH! Invalid code! */
  result->data = result->addr = -1;
  return;
}


void Patch_Codes(void)
{
	int i;

	for(i = 0; i < 256; i ++)
	{
		if ((Liste_GG[i].code[0] != 0) && (Liste_GG[i].addr != 0xFFFFFFFF) && (Liste_GG[i].active))
		{
			if (Liste_GG[i].addr < Rom_Size)
			{
				Rom_Data[Liste_GG[i].addr] = Liste_GG[i].data & 0xFF;
				Rom_Data[Liste_GG[i].addr + 1] = (Liste_GG[i].data & 0xFF00) >> 8;
			}
			else M68K_WW(Liste_GG[i].addr, Liste_GG[i].data);
		}
	}

	return;
}


int check_code(char *Code, unsigned int ind)
{
	if ((strlen(Code) > 11) || (strlen(Code) < 8))
	{
	return(0);
	}

	if (strlen(Code) == 8)
	{
		Liste_GG[ind].code[0] = Code[0];
		Liste_GG[ind].code[1] = Code[1];
		Liste_GG[ind].code[2] = Code[2];
		Liste_GG[ind].code[3] = Code[3];
		Liste_GG[ind].code[4] = '-';
		Liste_GG[ind].code[5] = Code[4];
		Liste_GG[ind].code[6] = Code[5];
		Liste_GG[ind].code[7] = Code[6];
		Liste_GG[ind].code[8] = Code[7];
		Liste_GG[ind].code[9] = 0;
	}
	else if (strlen(Code) == 10)
	{
		Liste_GG[ind].code[0] = Code[0];
		Liste_GG[ind].code[1] = Code[1];
		Liste_GG[ind].code[2] = Code[2];
		Liste_GG[ind].code[3] = Code[3];
		Liste_GG[ind].code[4] = Code[4];
		Liste_GG[ind].code[5] = Code[5];
		Liste_GG[ind].code[6] = ':';
		Liste_GG[ind].code[7] = Code[6];
		Liste_GG[ind].code[8] = Code[7];
		Liste_GG[ind].code[9] = Code[8];
		Liste_GG[ind].code[10] = Code[9];
		Liste_GG[ind].code[11] = 0;
	}
	else strcpy(Liste_GG[ind].code, Code);

	return(1);
}


int Load_Patch_File(void)
{
	HANDLE Patch_File;
	unsigned char *Patch_String;
	char Name[2048], Code[16], Comment[256], c;
	unsigned int i_code, i_comment, Ind_GG;
	unsigned long Lenght, Bytes_Read, i;
	enum etat_sec {DEB_LIGNE, CODE, BLANC, COMMENT, ERR} etat = DEB_LIGNE;

	SetCurrentDirectory(Gens_Path);

	for(i = 0; i < 256; i++)
	{
		Liste_GG[i].code[0] = 0;
		Liste_GG[i].name[0] = 0;
		Liste_GG[i].active = 0;
		Liste_GG[i].addr = 0xFFFFFFFF;
		Liste_GG[i].data = 0;
		Liste_GG[i].restore = 0xFFFFFFFF;
	}
	
	strcpy(Name, Patch_Dir);
	strcat(Name, Rom_Name);
	strcat(Name, ".pat");
	
	Patch_File = CreateFile(Name, GENERIC_READ, FILE_SHARE_READ, 
		NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

	if (Patch_File == INVALID_HANDLE_VALUE) return(0);
	
	Lenght = GetFileSize(Patch_File, &Bytes_Read); 
 
	Patch_String = (unsigned char *) malloc(Lenght);

	if (!Patch_String)
	{
		CloseHandle(Patch_File);
		return(0);
	}

	if (ReadFile(Patch_File, Patch_String, Lenght, &Bytes_Read, NULL))
	{
		i = 0;
		Ind_GG = 0;

		while ((i < Bytes_Read) && (Ind_GG < 256))
		{
			c = Patch_String[i++];
		
			switch(etat)
			{
				case DEB_LIGNE:
					switch(c)
					{
						case '\n':
						case '\t':
						case ' ':
						case 13:
							break;
	
						default:
							etat = CODE;
							i_code = 0;
							Code[i_code++] = c;
							break;
					}
					break;
	
				case CODE:
					switch(c)
					{
						case '\n':
						case 13:
							Code[i_code] = 0;
							if (check_code(Code, Ind_GG)) Ind_GG++;
							etat = DEB_LIGNE;
							break;

						case '\t':
						case ' ':
							Code[i_code] = 0;
							if (check_code(Code, Ind_GG)) etat = BLANC;
							else etat = ERR;
							break;

	
						default:
							if (i_code < 14) Code[i_code++] = c;
							break;
					}
					break;
	
				case BLANC:
					switch(c)
					{
						case '\n':
							etat = DEB_LIGNE;
							Ind_GG++;
							break;

						case '\t':
						case ' ':
							break;

						default:
							i_comment = 0;
							Comment[i_comment++] = c;
							etat = COMMENT;
							break;
					}
					break;

					
				case COMMENT:
					switch(c)
					{
						case 13:
							break;

						case '\n':
							Comment[i_comment] = 0;
							strcpy(Liste_GG[Ind_GG].name, Comment);
							Ind_GG++;
							etat = DEB_LIGNE;
							break;

						default:
							if (i_comment < 240) Comment[i_comment++] = c;
							break;
					}
					break;

				case ERR:
					switch(c)
					{
						case '\n':
							etat = DEB_LIGNE;
							break;

						default:
							break;
					}
					break;
			}
		}

		switch(etat)
		{
			case CODE:
				Code[i_code] = 0;
				if (check_code(Code, Ind_GG)) Ind_GG++;
				break;
					
			case COMMENT:
				Comment[i_comment] = 0;
				strcpy(Liste_GG[Ind_GG].name, Comment);
				Ind_GG++;
				break;
		}
	}

	CloseHandle(Patch_File);
	free(Patch_String);

	return(1);
}


int Save_Patch_File(void)
{
	FILE *Patch_File;
	char Name[2048];
	int i;

	SetCurrentDirectory(Gens_Path);

	if (Liste_GG[0].code[0] == 0) return 0;

	strcpy(Name, Patch_Dir);
	strcat(Name, Rom_Name);
	strcat(Name, ".pat");
	
	Patch_File = fopen(Name, "w");

	if (Patch_File == NULL) return 0;

	for(i = 0; i < 256; i++)
	{
		if (Liste_GG[i].code[0] != 0)
			fprintf(Patch_File, "%s\t%s\n", Liste_GG[i].code, Liste_GG[i].name);
	}

	fclose(Patch_File);

	return(1);
}
