// SPDX-FileCopyrightText: 2008-2011 pancake <pancake@nopcode.org>
// SPDX-License-Identifier: LGPL-3.0-only

#include "bfvm.h"

static ut8 bfvm_op(BfvmCPU *c) {
	// XXX: this is slow :(
	ut8 buf[4] = { 0 };
	if (c && c->iob.read_at && !c->iob.read_at(c->iob.io, c->eip, buf, 4)) {
		return 0xff;
	}
	return buf[0];
}

RZ_API int bfvm_in_trap(BfvmCPU *c) {
	switch (bfvm_op(c)) {
	case 0x00:
	case 0xcc:
	case 0xff:
		return 1;
	}
	return 0;
}

RZ_API void bfvm_reset(BfvmCPU *c) {
	memset(c->mem, '\0', c->size);
	memset(c->input_buf, '\0', c->input_size);
	memset(c->screen_buf, '\0', c->screen_size);
	c->base = BFVM_DATA_ADDR;
	c->input = BFVM_INPUT_ADDR;
	c->input_idx = 0;
	c->screen = BFVM_SCREEN_ADDR;
	c->screen_idx = 0;
	c->eip = 0; // TODO look forward nops
	c->ptr = 0;
	c->esp = c->base;
}

RZ_API int bfvm_init(BfvmCPU *c, ut32 size, int circular) {
	memset(c, '\0', sizeof(BfvmCPU));

	/* data */
	c->mem = (ut8 *)malloc(size);
	if (!c->mem) {
		return 0;
	}
	memset(c->mem, '\0', size);

	/* setup */
	c->circular = circular;
	c->size = size;

	// TODO: use RzBuffer or so here.. this is spagueti
	/* screen */
	c->screen = BFVM_SCREEN_ADDR;
	c->screen_size = BFVM_SCREEN_SIZE;
	c->screen_buf = (ut8 *)malloc(c->screen_size);
	memset(c->screen_buf, '\0', c->screen_size);

	/* input */
	c->input_size = BFVM_INPUT_SIZE;
	c->input_buf = (ut8 *)malloc(c->input_size);
	bfvm_reset(c);
	return 1;
}

RZ_API BfvmCPU *bfvm_new(RzIOBind *iob) {
	BfvmCPU *c = RZ_NEW0(BfvmCPU);
	bfvm_init(c, 4096, 1);
	memcpy(&c->iob, iob, sizeof(c->iob));
	return c;
}

RZ_API BfvmCPU *bfvm_free(BfvmCPU *c) {
	free(c->mem);
	c->mem = 0;
	free(c->screen_buf);
	c->screen_buf = 0;
	free(c);
	return NULL;
}

RZ_API ut8 *bfvm_get_ptr_at(BfvmCPU *c, ut64 at) {
	if (at >= c->base) {
		at -= c->base;
	} else if (at >= c->size) {
		at = c->circular ? 0 : c->size - 1;
	}
	return c->mem + at;
}

RZ_API ut8 *bfvm_get_ptr(BfvmCPU *c) {
	// return bfvm_cpu.mem;
	return bfvm_get_ptr_at(c, c->ptr);
}

RZ_API ut8 bfvm_get(BfvmCPU *c) {
	ut8 *ptr = bfvm_get_ptr(c);
	return ptr ? *ptr : 0;
}

RZ_API void bfvm_inc(BfvmCPU *c) {
	ut8 *mem = bfvm_get_ptr(c);
	if (mem != NULL) {
		mem[0]++;
	}
}

RZ_API void bfvm_dec(BfvmCPU *c) {
	ut8 *mem = bfvm_get_ptr(c);
	if (mem != NULL) {
		mem[0]--;
	}
}

RZ_API int bfvm_reg_set(BfvmCPU *c, const char *str) {
	char *ptr = strchr(str, ' ');
	if (!ptr) {
		return 0;
	}
	if (strstr(str, "eip")) {
		c->eip = rz_num_math(NULL, ptr + 1);
	} else if (strstr(str, "esp")) {
		c->esp = rz_num_math(NULL, ptr + 1);
	} else if (strstr(str, "ptr")) {
		c->ptr = rz_num_math(NULL, ptr + 1);
	}
	return 1;
}

/* screen and input */
RZ_API void bfvm_peek(BfvmCPU *c) {
	int idx = c->input_idx;
	ut8 *ptr = bfvm_get_ptr(c);

	if (idx >= c->input_size) {
		idx = 0;
	}

	if (ptr) {
		*ptr = c->input_buf[idx];
		c->input_idx = idx + 1;
	}
}

RZ_API void bfvm_poke(BfvmCPU *c) {
	int idx = c->screen_idx;
	c->screen_buf[idx] = bfvm_get(c);
	c->screen_idx = idx + 1;
}

RZ_API int bfvm_trace_op(BfvmCPU *c, ut8 op) {
	ut8 g;
	switch (op) {
	case '\0':
		eprintf(" ; trap (%02x)\n", op);
		// fallthrough
	case '.':
	case ',':
	case '+':
	case '-':
	case '>':
	case '<':
		eprintf("%c", op);
		break;
	case '[':
	case ']':
		g = bfvm_get(c);
		eprintf("%c  ; [ptr] = %d\n", op, g);
		if (g != 0) {
			eprintf("[");
		}
		break;
	}
	return 0;
}

#define T if (c->trace)
/* debug */
RZ_API int bfvm_step(BfvmCPU *c, int over) {
	ut8 op2, op = bfvm_op(c);

	do {
		T bfvm_trace_op(c, op);
		switch (op) {
		case '\0':
			/* trap */
			return 1;
		case '.':
			// bfvm_get_ptr (c);
			bfvm_poke(c);
			break;
		case ',':
			bfvm_peek(c);
			/* TODO read */
			break;
		case '+':
			bfvm_inc(c);
			break;
		case '-':
			bfvm_dec(c);
			break;
		case '>':
			c->ptr++;
			break;
		case '<':
			c->ptr--;
			break;
		case '[':
			break;
		case ']':
			if (bfvm_get(c) != 0) {
				do {
					/* control underflow */
					if (c->eip < (c->eip - 1)) {
						c->eip = 0;
						break;
					}
					c->eip--;
				} while (bfvm_op(c) != '[');
			}
			break;
		default:
			break;
		}
		c->eip++;
		op2 = bfvm_op(c);
	} while (over && op == op2);

	return 0;
}

RZ_API int bfvm_contsc(BfvmCPU *c) {
	c->breaked = 0;
	while (!c->breaked) {
		bfvm_step(c, 0);
		if (bfvm_in_trap(c)) {
			eprintf("Trap instruction at 0x%08" PFMT64x "\n", c->eip);
			break;
		}
		switch (bfvm_op(c)) {
		case ',':
			eprintf("contsc: read from input trap\n");
			c->breaked = 1;
			continue;
		case '.':
			eprintf("contsc: print to screen trap\n");
			c->breaked = 1;
			continue;
		}
	}
	return 0;
}

RZ_API int bfvm_cont(BfvmCPU *c, ut64 until) {
	c->breaked = 0;
	while (!c->breaked && c->eip != until) {
		bfvm_step(c, 0);
		if (bfvm_in_trap(c)) {
			eprintf("Trap instruction at 0x%" PFMT64x "\n", c->eip);
			break;
		}
	}
	return 0;
}

RZ_API int bfvm_trace(BfvmCPU *c, ut64 until) {
	c->trace = 1;
	bfvm_cont(c, until);
	c->trace = 0;
	return 0;
}

RZ_API void bfvm_show_regs(BfvmCPU *c, int rad) {
	if (rad) {
		eprintf("fs regs\n");
		eprintf("f eip @ 0x%08" PFMT64x "\n", (ut64)c->eip);
		eprintf("f esp @ 0x%08" PFMT64x "\n", (ut64)c->esp);
		eprintf("f ptr @ 0x%08" PFMT64x "\n", (ut64)c->ptr + c->base);
		eprintf("fs *\n");
	} else {
		ut8 ch = bfvm_get(c);
		eprintf("  eip  0x%08" PFMT64x "     esp  0x%08" PFMT64x "\n",
			(ut64)c->eip, (ut64)c->esp);
		eprintf("  ptr  0x%08x     [ptr]  %d = 0x%02x '%c'\n",
			(ut32)c->ptr, ch, ch, IS_PRINTABLE(ch) ? ch : ' ');
	}
}

RZ_API void bfvm_maps(BfvmCPU *c, int rad) {
	if (rad) {
		eprintf("fs sections\n");
		eprintf("e cmd.vprompt=px@screen\n");
		eprintf("f section_code @ 0x%08" PFMT64x "\n", (ut64)BFVM_CODE_ADDR);
		eprintf("f section_code_end @ 0x%08" PFMT64x "\n", (ut64)BFVM_CODE_ADDR + BFVM_CODE_SIZE);
		eprintf("f section_data @ 0x%08" PFMT64x "\n", (ut64)c->base);
		eprintf("f section_data_end @ 0x%08" PFMT64x "\n", (ut64)c->base + c->size);
		eprintf("f screen @ 0x%08" PFMT64x "\n", (ut64)c->screen);
		eprintf("f section_screen @ 0x%08" PFMT64x "\n", (ut64)c->screen);
		eprintf("f section_screen_end @ 0x%08" PFMT64x "\n", (ut64)c->screen + c->screen_size);
		eprintf("f input @ 0x%08" PFMT64x "\n", (ut64)c->input);
		eprintf("f section_input @ 0x%08" PFMT64x "\n", (ut64)c->input);
		eprintf("f section_input_end @ 0x%08" PFMT64x "\n", (ut64)c->input + c->input_size);
		eprintf("fs *\n");
	} else {
		eprintf("0x%08" PFMT64x " - 0x%08" PFMT64x " rwxu 0x%08" PFMT64x " .code\n",
			(ut64)0, (ut64)c->size, (ut64)c->size);
		eprintf("0x%08" PFMT64x " - 0x%08" PFMT64x " rw-- 0x%08" PFMT64x " .data\n",
			(ut64)c->base, (ut64)(c->base + c->size), (ut64)c->size);
		eprintf("0x%08" PFMT64x " - 0x%08" PFMT64x " rw-- 0x%08" PFMT64x " .screen\n",
			(ut64)c->screen, (ut64)(c->screen + c->screen_size), (ut64)c->screen_size);
		eprintf("0x%08" PFMT64x " - 0x%08" PFMT64x " rw-- 0x%08" PFMT64x " .input\n",
			(ut64)c->input, (ut64)(c->input + c->input_size), (ut64)c->input_size);
	}
}