#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdbool.h>

#include "dis.h"
#include "dis_syn.h"

/*
 * Another World script disassembler
 *   Only DOS version are supported
 */

#define MSG_USAGE "usage: disasm [-a | -i | -u] [-p] OBJECT OUTFILE\n"
#define MSG_OPENERR "can't open file %s.\n"
#define MSG_WRITEERR "can't create file %s.\n"
#define MSG_INVALIDOP "invalid opcode 0x%X\n"
#define MSG_INVALIDJMP "invalid jump opcode %u\n"

char *input, *output;

FILE *fp;

uint8_t *code;
uint16_t codesize;
uint16_t pc, adr;

struct labelinfo label[MAX_LABEL];
int labelnum;
bool printcode;
bool printadr;

void (*printlabel)(int);
void (*printopcode)(uint16_t, uint16_t, uint16_t, uint16_t, uint16_t, int);

static uint8_t ubyte() {
	return code[pc++];
}

static uint16_t uword() {
	return (ubyte() << 8) | ubyte();
}

static int addlabel(uint16_t adr, int type) {
	for(int i = 0; i < labelnum; i++) {
		if(label[i].adr == adr)
			return i;
	}
	
	label[labelnum].adr = adr;
	label[labelnum].type = type;
	++labelnum;
	return labelnum - 1;
}

static void fndlabel() {
	for(int i = 0; i < labelnum; i++) {
		if(label[i].adr == pc) {
			printlabel(i);
			return;
		}
	}
	
	printlabel(-1);
}

static void step() {
	adr = pc;

	if(printcode)
		fndlabel();

	uint8_t op = ubyte();
	uint16_t x = -1, y = -1, z = -1, w = -1;
	int label = -666;
	
	if(op & 0x80) { /* spr */
		w = (((op << 8) | ubyte()) << 1) & 0x7FFF;
		x = ubyte();
		y = ubyte();
	} else if(op & 0x40) { /* spr */
		w = (uword() << 1) & 0x7FFF;
		
		x = ubyte();
		if((op & 48) == 0)
			x = (x << 8) | ubyte();
		else if((op & 48) == 48)
			x = x + 256;
		
		y = ubyte();
		if((op & 12) == 0)
			y = (y << 8) | ubyte();
		
		if((op & 3) == 1 || (op & 3) == 2)
			z = ubyte();
		else
			z = 64;
	} else {
		switch(op) {
		case 0x0: /* seti */
			x = ubyte();
			y = uword();
			break;
		case 0x1: /* set */
			x = ubyte();
			y = ubyte();
			break;
		case 0x2: /* add */
			x = ubyte();
			y = ubyte();
			break;
		case 0x3: /* addi */
			x = ubyte();
			y = uword();
			break;
		case 0x4: /* jsr */
			x = uword();
			label = addlabel(x, LT_CALL);
			break;
		case 0x5: /* return */
			break;
		case 0x6: /* break */
			break;
		case 0x7: /* jmp */
			x = uword();
			label = addlabel(x, LT_JUMP);
			break;
		case 0x8: /* setvec */
			x = ubyte();
			y = uword();
			label = addlabel(y, LT_VEC);
			break;
		case 0x9: /* dbra */
			x = ubyte();
			y = uword();
			label = addlabel(y, LT_JUMP);
			break;
		case 0xA: /* si */
			w = ubyte();
			x = ubyte();
			
			if(w & 0x80)
				y = ubyte();
			else if(w & 0x40)
				y = uword();
			else
				y = ubyte();
			
			if((w & 7) > 5) {
				printf(MSG_INVALIDJMP, w & 0x7);
				exit(1);
			}
			
			z = uword();
			label = addlabel(z, LT_JUMP);
			break;
		case 0xB: /* fade */
			x = uword() >> 8;
			break;
		case 0xC: /* vec */
			x = ubyte();
			y = ubyte();		
			z = ubyte();
			break;
		case 0xD: /* setws */
			x = ubyte();
			break;
		case 0xE: /* clr */
			x = ubyte();
			y = ubyte();
			break;
		case 0xF: /* copy */
			x = ubyte();
			y = ubyte();
			break;
		case 0x10: /* show */
			x = ubyte();
			break;
		case 0x11: /* bigend */
			break;
		case 0x12: /* text */
			z = uword();
			x = ubyte();
			y = ubyte();
			w = ubyte();
			break;
		case 0x13: /* sub */
			x = ubyte();
			y = ubyte();
			break;
		case 0x14: /* andi */
			x = ubyte();
			y = uword();
			break;
		case 0x15: /* ori */
			x = ubyte();
			y = uword();
			break;
		case 0x16: /* lsl */
			x = ubyte();
			y = uword();
			break;
		case 0x17: /* lsr */
			x = ubyte();
			y = uword();
			break;
		case 0x18: /* play */
			z = uword();
			x = ubyte();
			y = ubyte();
			w = ubyte();
			break;
		case 0x19: /* load */
			x = uword();
			break;
		case 0x1A: /* song */
			x = uword();
			y = uword();
			z = ubyte();
			break;
		default:
			printf(MSG_INVALIDOP, op);
			exit(1);
		}
	}
	
	if(printcode)
		printopcode(op, x, y, z, w, label);
}

static void readarg(int argc, char **argv) {
	if(argc < 3)
		goto error;
	
	printadr = false;
	printlabel = aw_printlabel;
	printopcode = aw_printopcode;
	
	int i = 1;
	while((i < argc) && (argv[i][0] == '-')) {
		if(strcmp("-a", argv[i]) == 0) {
			printlabel = aw_printlabel;
			printopcode = aw_printopcode;
		} else if(strcmp("-i", argv[i]) == 0) {
			printlabel = intel_printlabel;
			printopcode = intel_printopcode;
		} else if(strcmp("-u", argv[i]) == 0) {
			printlabel = att_printlabel;
			printopcode = att_printopcode;
		} else if(strcmp("-p", argv[i]) == 0) {
			printadr = true;
		} else {
			goto error;
		}
		
		++i;
	}
	
	if((argc - i) != 2)
		goto error;
		
	input = argv[i];
	output = argv[i + 1];
	return;
	
error:
	printf(MSG_USAGE);
	exit(1);	
}

int main(int argc, char **argv) {
	readarg(argc, argv);
		
	if((fp = fopen(input, "r")) == NULL) {
		printf(MSG_OPENERR, input);
		exit(1);
	}
	
	fseek(fp, 0, SEEK_END);
	codesize = ftell(fp);
	fseek(fp, 0, SEEK_SET);
	
	code = malloc(codesize);
	fread(code, codesize, 1, fp);
	fclose(fp);
	
	if((fp = fopen(output, "w")) == NULL) {
		printf(MSG_WRITEERR, output);
		exit(1);
	}
	
	labelnum = 0;
	
	pc = 0;
	printcode = false;
	while(pc < codesize)
		step(); /* read labels */
	
	pc = 0;
	printcode = true;
	while(pc < codesize)
		step(); /* print code */
	
	fclose(fp);
	free(code);
	
	return 0;
}