#include "bf_compiler.h"

#include <stdio.h>
#include <string.h>
#include <unistd.h>

static void fwrite_str(char *str, FILE *f)
{
	fwrite(str, strlen(str), 1, f);
}

static void fwrite_str_line(char *str, FILE *f)
{
	fwrite_str(str, f);
	fwrite_str("\n", f);
}

static int bf_compiler_compile_nasm(struct bf_compiler *compiler, const char *output_filename, const char *program, size_t program_len)
{
	int rc = -1;
	FILE *f = NULL;

	if (compiler->cell_size != 8) {
		return -1;
	}

	// TODO: Write to temp directory
	f = fopen("tmp.asm", "w");
	if (!f) {
		goto err;
	}

	fwrite_str_line("section .bss", f);
	char data_define[128] = { 0 };
	snprintf(data_define, sizeof(data_define), "data resb %d", compiler->data_len);
	fwrite_str_line(data_define, f);

	fwrite_str_line("section .text", f);
	fwrite_str_line("global _start", f);
	fwrite_str_line("_start:", f);

	fwrite_str_line("mov bl, 0", f);

	uint32_t loop_stack[128] = { 0 };
	uint32_t loop_stack_len = 0;

	uint32_t last_loop_index = 0;
	for (int i = 0; i < program_len; i++) {
		char inst = program[i];

		if (inst == '>') {
			fwrite_str_line("; >", f);
			fwrite_str_line("inc bl", f);
		} else if (inst == '<') {
			fwrite_str_line("; <", f);
			fwrite_str_line("dec bl", f);
		} else if (inst == '+') {
			fwrite_str_line("; +", f);
			fwrite_str_line("inc byte [data + rbx]", f);
		} else if (inst == '-') {
			fwrite_str_line("; -", f);
			fwrite_str_line("dec byte [data + rbx]", f);
		} else if (inst == '.') {
			fwrite_str_line("; .", f);
			// sys_write
			fwrite_str_line("mov rax, 1", f); // Syscall id
			fwrite_str_line("mov rdi, 1", f); // fd
			fwrite_str_line("lea rsi, byte [data + rbx]", f); // buff
			fwrite_str_line("mov rdx, 1", f); // count
			fwrite_str_line("syscall", f);
		} else if (inst == ',') {
			fwrite_str_line("; ,", f);
			// sys_read
			fwrite_str_line("mov rax, 0", f); // Syscall id
			fwrite_str_line("mov rdi, 0", f); // fd
			fwrite_str_line("lea rsi, byte [data + rbx]", f); // buff
			fwrite_str_line("mov rdx, 1", f); // count
			fwrite_str_line("syscall", f);
		} else if (inst == '[') {
			fwrite_str_line("; [", f);

			uint32_t loop_index = last_loop_index;
			last_loop_index++;

			loop_stack[loop_stack_len++] = loop_index;

			char start_label[128] = { 0 };
			snprintf(start_label, sizeof(start_label), "S%d_start:", loop_index);
			fwrite_str_line(start_label, f);

			fwrite_str_line("cmp byte [data + rbx], 0", f);

			char jump_inst[128] = { 0 };
			snprintf(jump_inst, sizeof(jump_inst), "jz S%d_end", loop_index);
			fwrite_str_line(jump_inst, f);
		} else if (inst == ']') {
			fwrite_str_line("; ]", f);
			uint32_t loop_index = loop_stack[--loop_stack_len];

			char jump_to_start[128] = { 0 };
			snprintf(jump_to_start, sizeof(jump_to_start), "jmp S%d_start", loop_index);
			fwrite_str_line(jump_to_start, f);

			char end_label[128] = { 0 };
			snprintf(end_label, sizeof(end_label), "S%d_end:", loop_index);
			fwrite_str_line(end_label, f);
		}
	}

	fwrite_str_line("; exit(0)", f);
	fwrite_str_line("mov rax, 60", f);
	fwrite_str_line("mov rdi, 0", f);
	fwrite_str_line("syscall", f);

	fclose(f);
	f = NULL;

	// TODO: Use exec instead of system
	// TODO: Don't hardcode the platform
	system("nasm -felf64 tmp.asm -o tmp.o");

	char ld_command[256] = { 0 };
	snprintf(ld_command, sizeof(ld_command), "ld tmp.o -o %s", output_filename);
	system(ld_command);
	rc = 0;
err:
	if (f) fclose(f);
	return rc;
}