#include <u.h>
#include <libc.h>
#include "6502.h"

void asprintf(char** targ, char* msg, ...) {
	*targ = malloc(512);
	va_list va;
	va_start(va, msg);
	vsnprint(*targ, 511, msg, va);
	va_end(va);
}

char* disasm(byte* x) {
	switch(*x) {
		case 0x00: return strdup("BRK"); break;
		case 0x08: return strdup("PHP"); break;
		case 0x18: return strdup("CLC"); break;
		case 0x20: {
			char* buf;
			asprintf(&buf, "JSR $%.2x", x[1] | (x[2] << 8));
			return buf;
		}
		case 0x28: return strdup("PLP"); break;
		case 0x38: return strdup("SEC"); break;
		case 0x40: return strdup("RTI"); break;
		case 0x48: return strdup("PHA"); break;
		case 0x4C: {
			char* buf;
			asprintf(&buf, "JMP $%.2x", x[1] | (x[2] << 8));
			return buf;
		}
		case 0x58: return strdup("CLI"); break;
		case 0x60: return strdup("RTS"); break;
		case 0x6C: {
			char* buf;
			asprintf(&buf, "JMP ($%.2x)", x[1] | (x[2] << 8));
			return buf;
		}
		case 0x68: return strdup("PLA"); break;
		case 0x78: return strdup("SEI"); break;
		case 0x88: return strdup("DEY"); break;
		case 0x8A: return strdup("TXA"); break;
		case 0x98: return strdup("TYA"); break;
		case 0x9A: return strdup("TXS"); break;
		case 0xA8: return strdup("TAY"); break;
		case 0xAA: return strdup("TAX"); break;
		case 0xB8: return strdup("CLV"); break;
		case 0xBA: return strdup("TSX"); break;
		case 0xC8: return strdup("INY"); break;
		case 0xCA: return strdup("DEX"); break;
		case 0xD8: return strdup("CLD"); break;
		case 0xE8: return strdup("INX"); break;
		case 0xEA: return strdup("NOP"); break;
		case 0xF8: return strdup("SED"); break;
	}
	byte a = *x >> 5;
	byte b = (*x >> 2) & 7;
	byte c = *x & 3;
	if(c == 0) {
		if(b != 4) {
			char * os[] = {"", "BIT", "JMP", "JMP", "STY", "LDY", "CPY", "CPX"};
			char* buf;
			switch(b) {
				case 0: asprintf(&buf, "%s #$%x", os[a], x[1]); break;
				case 1: asprintf(&buf, "%s $%x", os[a], x[1]); break;
				case 3: asprintf(&buf, "%s $%x", os[a], x[1] | (x[2] << 8)); break;
				case 5: asprintf(&buf, "%s $%x, X", os[a], x[1]); break;
				case 7: asprintf(&buf, "%s $%x, X", os[a], x[1] | (x[2] << 8)); break;
			}
			return buf;
		}
	 	char * os[] = {"BPL", "BMI", "BVC", "BVS", "BCC", "BCS", "BNE", "BEQ"};
		char* buf;
		asprintf(&buf, "%s $%x", os[a], x[1]);
		return buf;
	}
	if(c == 1) {
	 	char * os[] = {"ORA", "AND", "EOR", "ADC", "STA", "LDA", "CMP", "SBC"};
		char* buf;
		switch(b) {
			case 0: asprintf(&buf, "%s ($%x, X)", os[a], x[1]); break;
			case 1: asprintf(&buf, "%s $%x", os[a], x[1]); break;
			case 2: asprintf(&buf, "%s #$%x", os[a], x[1]); break;
			case 3: asprintf(&buf, "%s $%x", os[a], x[1] | (x[2] << 8)); break;
			case 4: asprintf(&buf, "%s ($%x, Y)", os[a], x[1]); break;
			case 5: asprintf(&buf, "%s $%x, X", os[a], x[1]); break;
			case 6: asprintf(&buf, "%s ($%x, Y)", os[a], x[1] | (x[2] << 8)); break;
			case 7: asprintf(&buf, "%s ($%x, X)", os[a], x[1] | (x[2] << 8)); break;
		}
		return buf;
	}
	if(c == 2) {
	 	char * os[] = {"ASL", "ROL", "LSR", "ROR", "STX", "LDX", "DEC", "INC"};
		char* buf;
		switch(b) {
			case 0: asprintf(&buf, "%s #$%x", os[a], x[1]); break;
			case 1: asprintf(&buf, "%s $%x", os[a], x[1]); break;
			case 2: asprintf(&buf, "%s A", os[a]); break;
			case 3: asprintf(&buf, "%s $%x", os[a], x[1] | (x[2] << 8)); break;
			case 5: asprintf(&buf, "%s $%x, X", os[a], x[1]); break;
			case 7: asprintf(&buf, "%s $%x, X", os[a], x[1] | (x[2] << 8)); break;
		}
		return buf;
	}
	return strdup("???");
}