/* gbmch.c */

/*
 *  Copyright (C) 1989-2021  Alan R. Baldwin
 *
 *  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, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  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, see <http://www.gnu.org/licenses/>.
 *
 *
 * Alan R. Baldwin
 * 721 Berkeley St.
 * Kent, Ohio  44240
 */

/*
 * Extensions: P. Felber
 */

/* Gameboy mods by Roger Ivie (ivie at cc dot usu dot edu); see gb.h for more info 
 */

#include "asxxxx.h"
#include "gb.h"

char    *cpu    = "GameBoy Z80-like CPU";
char    *dsft   = "asm";

char    imtab[3] = { 0x46, 0x56, 0x5E };

/*
 * Opcode Cycle Definitions
 */
#define OPCY_SDP        ((char) (0xFF))
#define OPCY_ERR        ((char) (0xFE))

/*      OPCY_NONE       ((char) (0x80)) */
/*      OPCY_MASK       ((char) (0x7F)) */

#define UN      ((char) (OPCY_NONE | 0x00))
#define P2      ((char) (OPCY_NONE | 0x01))

/*
 * Process a machine op.
 */
VOID
machine(mp)
struct mne *mp;
{
        int op, t1, t2;
        struct expr e1, e2;
        int rf, v1, v2;
	int d,c,i,th,tl,oops; /* for dealing with .tile */

        clrexpr(&e1);
        clrexpr(&e2);
        op = (int) mp->m_valu;
        rf = mp->m_type;
        switch (rf) {

        case S_INH1:
                outab(op);
                break;

        case S_RET:
                if (more()) {
                        if ((v1 = admode(CND)) != 0) {
                                outab(op | (v1<<3));
                        } else {
                                qerr();
                        }
                } else {
                        outab(0xC9);
                }
                break;

        case S_PUSH:
                if (admode(R16X)) {
                        outab(op+0x30);
                        break;
                } else
                if ((v1 = admode(R16)) != 0 && (v1 &= 0xFF) != SP) {
                        outab(op | (v1<<4));
                        break;
                }
                aerr();
                break;

        case S_RST:
                v1 = (int) absexpr();
                if (v1 & ~0x38) {
                        aerr();
                        v1 = 0;
                }
                outab(op|v1);
                break;

        case S_IM:
                expr(&e1, 0);
                abscheck(&e1);
                if (e1.e_addr > 2) {
                        aerr();
                        e1.e_addr = 0;
                }
                outab(op);
                outab(imtab[(int) e1.e_addr]);
                break;

        case S_BIT:
                expr(&e1, 0);
                t1 = 0;
                v1 = (int) e1.e_addr;
                if (v1 > 7) {
                        ++t1;
                        v1 &= 0x07;
                }
                op |= (v1<<3);
                comma(1);
                addr(&e2);
                abscheck(&e1);
                if (genop(0xCB, op, &e2, 0) || t1)
                        aerr();
                break;

        case S_RL:
                t1 = 0;
                t2 = addr(&e2);
                if (more()) {
                        if ((t2 != S_R8) || (e2.e_addr != A))
                                ++t1;
                        comma(1);
                        clrexpr(&e2);
                        t2 = addr(&e2);
                }
                if (genop(0xCB, op, &e2, 0) || t1)
                        aerr();
                break;

        case S_AND:
        case S_SUB:
                t1 = 0;
                t2 = addr(&e2);
                if (more()) {
                        if ((t2 != S_R8) || (e2.e_addr != A))
                                ++t1;
                        comma(1);
                        clrexpr(&e2);
                        t2 = addr(&e2);
                }
                if (genop(0, op, &e2, 1) || t1)
                        aerr();
                break;

        case S_ADC:
        case S_SBC:
                t1 = addr(&e1);
                t2 = 0;
                if (more()) {
                        comma(1);
                        t2 = addr(&e2);
                }
                if (t2 == 0) {
                        if (genop(0, op, &e1, 1))
                                aerr();
                        break;
                }
                if ((t1 == S_R8) && (e1.e_addr == A)) {
                        if (genop(0, op, &e2, 1))
                                aerr();
                        break;
                }
                aerr();
                break;

        case S_ADD:
                t1 = addr(&e1);
                t2 = 0;
                if (more()) {
                        comma(1);
                        t2 = addr(&e2);
                }
                if (t2 == 0) {
                        if (genop(0, op, &e1, 1))
                                aerr();
                        break;
                }
                if ((t1 == S_R8) && (e1.e_addr == A)) {
                        if (genop(0, op, &e2, 1))
                                aerr();
                        break;
                }
                if ((t1 == S_R16) && (t2 == S_R16)) {
                        op = 0x09;
                        v1 = (int) e1.e_addr;
                        v2 = (int) e2.e_addr;
                        if ((v1 == HL) && (v2 <= SP)) {
                                outab(op | (v2 << 4));
                                break;
                        }
                }
                /*
                 * 0xE8 : ADD SP,#n
                 */
                if ((t1 == S_R16) && (e1.e_addr == SP) && (t2 == S_IMMED)) {
                        outab(0xE8);
                        outrb(&e2,0);
                        break;
                }
                aerr();
                break;

        case S_LD:
                t1 = addr(&e1);
                comma(1);
                t2 = addr(&e2);

                if (t1 == S_R8) {
                        v1 = (int) (e1.e_addr<<3);
                        if (genop(0, op | v1, &e2, 0) == 0)
                                break;
                        if (t2 == S_IMMED) {
                                outab(v1 | 0x06);
                                outrb(&e2,0);
                                break;
                        }
                }

                v1 = (int) e1.e_addr;
                v2 = (int) e2.e_addr;

                if ((t1 == S_R16) && (t2 == S_IMMED)) {
                        outab(0x01 | (v1<<4));
                        outrw(&e2, 0);
                        break;
                }
                if ((t2 == S_R8) && (t1 == S_IDHL)) {
                        outab(0x70|v2);
                        if (t1 != S_IDHL)
                                outrb(&e1, 0);
                        break;
                }
                if ((t2 == S_IMMED) && (t1 == S_IDHL)) {
                        outab(0x36);
                        if (t1 != S_IDHL)
                                outrb(&e1, 0);
                        outrb(&e2, 0);
                        break;
                }
                if ((t1 == S_R16) && (v1 == SP)) {
                        if ((t2 == S_R16) && (v2 == HL)) {
                                outab(0xF9);
                                break;
                        }
                }
                if ((t1 == S_R8) && (v1 == A)) {
                        if ((t2 == S_IDBC) || (t2 == S_IDDE)) {
                                outab(0x0A | ((t2-S_INDR)<<4));
                                break;
                        }
                }
                if ((t2 == S_R8) && (v2 == A)) {
                        if ((t1 == S_IDBC) || (t1 == S_IDDE)) {
                                outab(0x02 | ((t1-S_INDR)<<4));
                                break;
                        }
                }
                /*
                 * 0x08 : LD (nn),SP
                 */
                if ((t1 == S_INDM) && (t2 == S_R16) && (v2 == SP)) {
                        outab(0x08);
                        outrw(&e1, 0);
                        break;
                }
                /*
                 * 0xEA : LD (nn),A
                 * 0xFA : LD A,(nn)
                 */
                if ((t1 == S_INDM) && (t2 == S_R8) && (v2 == A)) {
                        outab(0xEA);
                        outrw(&e1, 0);
                        break;
                }
                if ((t2 == S_INDM) && (t1 == S_R8) && (v1 == A)) {
                        outab(0xFA);
                        outrw(&e2, 0);
                        break;
                }
                /*
                 * 0x32 : LD (HL-),A
                 * 0x3A : LD A,(HL-)
                 */
                if ((t1 == S_R8) && (v1 == A) && (t2 == S_IDHLD)) {
                        outab(0x3A);
                        break;
                }
                if ((t2 == S_R8) && (v2 == A) && (t1 == S_IDHLD)) {
                        outab(0x32);
                        break;
                }
                /*
                 * 0x22 : LD (HL+),A
                 * 0x2A : LD A,(HL+)
                 */
                if ((t1 == S_R8) && (v1 == A) && (t2 == S_IDHLI)) {
                        outab(0x2A);
                        break;
                }
                if ((t2 == S_R8) && (v2 == A) && (t1 == S_IDHLI)) {
                        outab(0x22);
                        break;
                }
                aerr();
                break;

        case S_STOP:    /* 0x10 */
                /*
                 * 0x10 : STOP
                 */
                outab(op);
                outab(0x00);
                break;


        case S_LDA:     /* 0xE8 */
                /*
                 * 0xE8 : LDA SP,#n(SP)
                 * 0xF8 : LDA HL,#n(SP)
                 */
                t1 = addr(&e1);
                comma(1);
                t2 = addr(&e2);
                if ((t1 == S_R16) && (e1.e_addr == SP) && (t2 == S_INDR+SP)) {
                        outab(0xE8);
                        outrb(&e2,0);
                        break;
                }
                if ((t1 == S_R16) && (e1.e_addr == HL) && (t2 == S_INDR+SP)) {
                        outab(0xF8);
                        outrb(&e2,0);
                        break;
                }
                aerr();
                break;

        case S_LDHL:    /* 0xF8 */
                /*
                 * 0xF8 : LDHL SP,#n
                 */
                t1 = addr(&e1);
                comma(1);
                t2 = addr(&e2);
                if ((t1 == S_R16) && (e1.e_addr == SP) && (t2 == S_IMMED)) {
                        outab(0xF8);
                        outrb(&e2,0);
                        break;
                }
                aerr();
                break;

        case S_DEC:
        case S_INC:
                t1 = addr(&e1);
                v1 = (int) e1.e_addr;
                if (t1 == S_R8) {
                        outab(op|(v1<<3));
                        break;
                }
                if (t1 == S_IDHL) {
                        outab(op|0x30);
                        break;
                }
                if (t1 == S_R16) {
                        if (rf == S_INC) {
                                outab(0x03|(v1<<4));
                                break;
                        }
                        if (rf == S_DEC) {
                                outab(0x0B|(v1<<4));
                                break;
                        }
                }
                aerr();
                break;

        case S_JR:
                if ((v1 = admode(CND)) != 0 ) {
                        if ((v1 &= 0xFF) <= 0x03) {
                                op += (v1+1)<<3;
                        } else {
                                aerr();
                        }
                        comma(1);
                }
                expr(&e2, 0);
                outab(op);
                if (mchpcr(&e2)) {
                        v2 = (int) (e2.e_addr - dot.s_addr - 1);
                        if (pass == 2 && ((v2 < -128) || (v2 > 127)))
                                aerr();
                        outab(v2);
                } else {
                        outrb(&e2, R_PCR);
                }
                if (e2.e_mode != S_USER)
                        rerr();
                break;

        case S_CALL:
                if ((v1 = admode(CND)) != 0) {
                        op |= (v1&0xFF)<<3;
                        comma(1);
                } else {
                        op = 0xCD;
                }
                expr(&e1, 0);
                outab(op);
                outrw(&e1, 0);
                break;

        case S_JP:
                if ((v1 = admode(CND)) != 0) {
                        op |= (v1&0xFF)<<3;
                        comma(1);
                        expr(&e1, 0);
                        outab(op);
                        outrw(&e1, 0);
                        break;
                }
                t1 = addr(&e1);
                if (t1 == S_USER) {
                        outab(0xC3);
                        outrw(&e1, 0);
                        break;
                }
                if ((e1.e_addr == 0) && (t1 == S_IDHL)) {
                        outab(0xE9);
                        break;
                }
                aerr();
                break;

        case S_LDH:
                /*
                 * 0xE0 : LDH (n),A = LD ($FF00+n),A
                 * 0xE2 : LDH (C),A = LD ($FF00+C),A
                 * 0xF0 : LDH A,(n) = LD A,($FF00+n)
                 * 0xF2 : LDH A,(C) = LD A,($FF00+C)
                 */

                t1 = addr(&e1);
                comma(1);
                t2 = addr(&e2);
                v1 = (int) e1.e_addr;
                v2 = (int) e2.e_addr;

                if ((t1 == S_R8) && (v1 == A) && (t2 == S_INDM)) {
                        outab(0xF0);
                        outrb(&e2, 0);
                        break;
                }
                if ((t2 == S_R8) && (v2 == A) && (t1 == S_INDM)) {
                        outab(0xE0);
                        outrb(&e1, 0);
                        break;
                }
                if ((t1 == S_R8) && (v1 == A) && (t2 == S_IDC)) {
                        outab(0xF2);
                        break;
                }
                if ((t2 == S_R8) && (v2 == A) && (t1 == S_IDC)) {
                        outab(0xE2);
                        break;
                }
                aerr();
                break;

	case S_TILE:
                /* Ported from ASXXXX 5.40 */
		/* The .tile pseudo-op. It generates two bytes from
		 * an 8-character ASCII string to represent a line of
		 * pixels in a Gameboy character.
		 */

		/* Like .ASCII, the first character after .TILE is used
		 * as the string delimiter. Get it.
		 */

		if ((d = getnb()) == '^') {
		  d = get();
		}
		if(d == '\0' ) {
		  //xerr('q', "TILE is a chunk of 8 characters."); 
                  qerr();
		}

		/* .tile deals with chunks of 8 characters. We need to
		 * generate an error if we get fewer than 8 characters in
		 * chunk, so we have a modulo-8 counter to keep track of
		 * how many characters we've processed. We also need to
		 * generate an error if we see a character we don't 
		 * recognize; this can be done either with a goto
		 * or an 'oops' flag. Although I normally lean towards
		 * goto implementations, since I didn't design _all_
		 * of this code that would be ugly; so we need to
		 * initialize the oops flag. We also need to initialize
		 * the variables we'll be using to collect the bits.
		 */

		i = 0;
		c = get(); /* Prime the pump */
		th = 0;
		tl = 0;
		oops = 0;

		/* Process characters until we find one we don't
		 * understand, encounter the delimiter, or run into
		 * the end of line.
		 */

		while( ( oops == 0 ) && ( c != d ) && ( c != 0 ) ) {

		  th = th << 1;
		  tl = tl << 1;

		  switch( c ) {
		    case ' ':
		    case '0':
		      break;
		    case '.':
		    case '1':
		      tl++; 
		      break;
		    case '+':
		    case '2':
		      th++; 
		      break;
		    case '*':
		    case '3':
		      th++; 
		      tl++; 
		      break;
		    default:  
		      oops = 1;
		      break;
		  }

		  c = get();
		  i++;

		  /* Spit out the tile data.
		   */

		  if( i == 8 ) {
		    outab( tl );
		    outab( th );
		    i = 0;
		    tl = 0;
		    th = 0;
		  }
		}

		/* Figure out whether we left the while loop early. If so,
		 * complain.
		 */

		if( i != 0 ) {
		  //xerr('a', "Invalid character or terminated without 8 characters.");
                  aerr();
		  break;
		}

		/* Make sure we have the delimiter next. This should
		 * already have been fetched by the end of the while().
		 * What this primarily buys us that the check for
		 * the modulo-8 counter does not is detecting a string
		 * which ended with an end-of-line rather than a
		 * delimiter.
		 */

		if( c != d ) {
		  //xerr('q', "Missing TILE terminator.");
                  qerr();
		  break;
		}

		break;
        default:
                err('o');
                break;
        }
}

/*
 * general addressing evaluation
 * return(0) if general addressing mode output, else
 * return(esp->e_mode)
 */
int
genop(pop, op, esp, f)
int pop, op;
struct expr *esp;
int f;
{
        int t1;
        if ((t1 = esp->e_mode) == S_R8) {
                if (pop)
                        outab(pop);
                outab(op|esp->e_addr);
                return(0);
        }
        if (t1 == S_IDHL) {
                if (pop)
                        outab(pop);
                outab(op|0x06);
                return(0);
        }
        if ((t1 == S_IMMED) && (f)) {
                if (pop)
                        outab(pop);
                outab(op|0x46);
                outrb(esp,0);
                return(0);
        }
        return(t1);
}

/*
 * Branch/Jump PCR Mode Check
 */
int
mchpcr(esp)
struct expr *esp;
{
        if (esp->e_base.e_ap == dot.s_area) {
                return(1);
        }
        if (esp->e_flag==0 && esp->e_base.e_ap==NULL) {
                /*
                 * Absolute Destination
                 *
                 * Use the global symbol '.__.ABS.'
                 * of value zero and force the assembler
                 * to use this absolute constant as the
                 * base value for the relocation.
                 */
                esp->e_flag = 1;
                esp->e_base.e_sp = &sym[1];
        }
        return(0);
}

/*
 * Machine dependent initialization
 */
VOID
minit()
{
        /*
         * Byte Order
         */
        hilo = 0;

        /*
         * Address Space
         */
        exprmasks(3);
}
