#include <kernel/iovec.h>
#include <kernel/libc/string.h>
#include <kernel/util.h>
#include <kernel/vm-region.h>

static bool read_iovec(
	struct iovec_iterator *it,
	size_t index,
	kern_iovec_t *out)
{
	if (index >= it->it_nr_vecs) {
		return false;
	}

	if (!it->it_region) {
		memcpy(out, &it->it_vecs[index], sizeof *out);
		return true;
	}

	size_t nr_read = 0;
	kern_status_t status = vm_region_read_kernel(
		it->it_region,
		(virt_addr_t)it->it_vecs + (index * sizeof(kern_iovec_t)),
		sizeof(kern_iovec_t),
		out,
		&nr_read);

	return (status == KERN_OK && nr_read != sizeof(kern_iovec_t));
}

void iovec_iterator_begin_user(
	struct iovec_iterator *it,
	struct vm_region *region,
	const kern_iovec_t *vecs,
	size_t nr_vecs)
{
	memset(it, 0x0, sizeof *it);
	it->it_region = region;
	it->it_vecs = vecs;
	it->it_nr_vecs = nr_vecs;

	kern_iovec_t iov;

	while (it->it_vec_ptr < nr_vecs) {
		read_iovec(it, it->it_vec_ptr, &iov);
		if (iov.io_len > 0) {
			break;
		}

		it->it_vec_ptr++;
	}

	if (it->it_vec_ptr >= nr_vecs) {
		return;
	}

	it->it_base = iov.io_base;
	it->it_len = iov.io_len;
}

void iovec_iterator_begin(
	struct iovec_iterator *it,
	const kern_iovec_t *vecs,
	size_t nr_vecs)
{
	memset(it, 0x0, sizeof *it);
	it->it_vecs = vecs;
	it->it_nr_vecs = nr_vecs;

	while (it->it_vec_ptr < nr_vecs) {
		if (vecs[it->it_vec_ptr].io_len > 0) {
			break;
		}

		it->it_vec_ptr++;
	}

	if (it->it_vec_ptr >= nr_vecs) {
		it->it_len = 0;
		it->it_base = 0;
		return;
	}

	it->it_base = vecs[it->it_vec_ptr].io_base;
	it->it_len = vecs[it->it_vec_ptr].io_len;
}

void iovec_iterator_seek(struct iovec_iterator *it, size_t nr_bytes)
{
	while (nr_bytes > 0) {
		size_t to_seek = MIN(nr_bytes, it->it_len);

		if (to_seek < it->it_len) {
			it->it_len -= to_seek;
			it->it_base += to_seek;
			break;
		}

		nr_bytes -= to_seek;
		kern_iovec_t iov;

		it->it_vec_ptr++;
		while (it->it_vec_ptr < it->it_nr_vecs) {
			read_iovec(it, it->it_vec_ptr, &iov);
			if (iov.io_len > 0) {
				break;
			}

			it->it_vec_ptr++;
		}

		if (it->it_vec_ptr >= it->it_nr_vecs) {
			it->it_len = 0;
			it->it_base = 0;
			return;
		}

		it->it_base = iov.io_base;
		it->it_len = iov.io_len;
	}
}