module mbedtls

import io
import net
import sync
import time

const mbedtls_client_read_timeout_ms = $d('mbedtls_client_read_timeout_ms', 10_000)
const mbedtls_server_read_timeout_ms = $d('mbedtls_server_read_timeout_ms', 41_000)
const default_mbedtls_client_read_timeout = mbedtls_client_read_timeout_ms * time.millisecond
const default_mbedtls_server_read_timeout = mbedtls_server_read_timeout_ms * time.millisecond

fn init_rng(mut ctr_drbg C.mbedtls_ctr_drbg_context, mut entropy C.mbedtls_entropy_context) ! {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	C.mbedtls_ctr_drbg_init(&ctr_drbg)
	C.mbedtls_entropy_init(&entropy)
	ret := C.mbedtls_ctr_drbg_seed(&ctr_drbg, C.mbedtls_entropy_func, &entropy, 0, 0)
	if ret != 0 {
		C.mbedtls_ctr_drbg_free(&ctr_drbg)
		C.mbedtls_entropy_free(&entropy)
		return error_with_code('net.mbedtls init_rng, failed to seed ssl context: ${ret}', ret)
	}
	// C.mbedtls_debug_set_threshold(5)
}

fn free_rng(mut ctr_drbg C.mbedtls_ctr_drbg_context, mut entropy C.mbedtls_entropy_context) {
	C.mbedtls_ctr_drbg_free(&ctr_drbg)
	C.mbedtls_entropy_free(&entropy)
}

// SSLCerts represents a pair of CA and client certificates + key
pub struct SSLCerts {
pub mut:
	cacert      C.mbedtls_x509_crt
	client_cert C.mbedtls_x509_crt
	client_key  C.mbedtls_pk_context
}

// new_sslcerts initializes and returns a pair of SSL certificates and key
pub fn new_sslcerts() &SSLCerts {
	mut certs := SSLCerts{}
	C.mbedtls_x509_crt_init(&certs.cacert)
	C.mbedtls_x509_crt_init(&certs.client_cert)
	C.mbedtls_pk_init(&certs.client_key)
	return &certs
}

// new_sslcerts_in_memory creates a pair of SSL certificates, given their contents (not paths).
pub fn new_sslcerts_in_memory(verify string, cert string, cert_key string) !&SSLCerts {
	mut ctr_drbg := C.mbedtls_ctr_drbg_context{}
	mut entropy := C.mbedtls_entropy_context{}
	init_rng(mut ctr_drbg, mut entropy)!
	defer {
		free_rng(mut ctr_drbg, mut entropy)
	}
	return new_sslcerts_in_memory_with_rng(verify, cert, cert_key, &ctr_drbg)
}

fn new_sslcerts_in_memory_with_rng(verify string, cert string, cert_key string, rng &C.mbedtls_ctr_drbg_context) !&SSLCerts {
	mut certs := new_sslcerts()
	if verify != '' {
		ret := C.mbedtls_x509_crt_parse(&certs.cacert, verify.str, verify.len + 1)
		if ret != 0 {
			return error_with_code('net.mbedtls new_sslcerts_in_memory, mbedtls_x509_crt_parse error 1 ret: ${ret}',
				ret)
		}
	}
	if cert != '' {
		ret := C.mbedtls_x509_crt_parse(&certs.client_cert, cert.str, cert.len + 1)
		if ret != 0 {
			return error_with_code('net.mbedtls new_sslcerts_in_memory, mbedtls_x509_crt_parse error 2 ret: ${ret}',
				ret)
		}
	}
	if cert_key != '' {
		unsafe {
			ret := C.mbedtls_pk_parse_key(&certs.client_key, cert_key.str, cert_key.len + 1, 0, 0,
				C.mbedtls_ctr_drbg_random, rng)
			if ret != 0 {
				return error_with_code('net.mbedtls new_sslcerts_in_memory, mbedtls_pk_parse_key error ret: ${ret}',
					ret)
			}
		}
	}
	return certs
}

// new_sslcerts_from_file creates a new pair of SSL certificates, given their paths on the filesystem.
pub fn new_sslcerts_from_file(verify string, cert string, cert_key string) !&SSLCerts {
	mut ctr_drbg := C.mbedtls_ctr_drbg_context{}
	mut entropy := C.mbedtls_entropy_context{}
	init_rng(mut ctr_drbg, mut entropy)!
	defer {
		free_rng(mut ctr_drbg, mut entropy)
	}
	return new_sslcerts_from_file_with_rng(verify, cert, cert_key, &ctr_drbg)
}

fn new_sslcerts_from_file_with_rng(verify string, cert string, cert_key string, rng &C.mbedtls_ctr_drbg_context) !&SSLCerts {
	mut certs := new_sslcerts()
	if verify != '' {
		ret := C.mbedtls_x509_crt_parse_file(&certs.cacert, &char(verify.str))
		if ret != 0 {
			return error_with_code('net.mbedtls new_sslcerts_from_file, mbedtls_x509_crt_parse_file error 1 ret: ${ret}',
				ret)
		}
	}
	if cert != '' {
		ret := C.mbedtls_x509_crt_parse_file(&certs.client_cert, &char(cert.str))
		if ret != 0 {
			return error_with_code('net.mbedtls new_sslcerts_from_file, mbedtls_x509_crt_parse_file error 2 ret: ${ret}',
				ret)
		}
	}
	if cert_key != '' {
		unsafe {
			ret := C.mbedtls_pk_parse_keyfile(&certs.client_key, &char(cert_key.str), 0,
				C.mbedtls_ctr_drbg_random, rng)
			if ret != 0 {
				return error_with_code('net.mbedtls new_sslcerts_from_file, mbedtls_pk_parse_keyfile error ret: ${ret}',
					ret)
			}
		}
	}
	return certs
}

// cleanup frees the SSL certificates
pub fn (mut c SSLCerts) cleanup() {
	C.mbedtls_x509_crt_free(&c.cacert)
	C.mbedtls_x509_crt_free(&c.client_cert)
	C.mbedtls_pk_free(&c.client_key)
}

// SSLConn is the current connection
pub struct SSLConn {
pub:
	config SSLConnectConfig
pub mut:
	server_fd    C.mbedtls_net_context
	ssl          C.mbedtls_ssl_context
	conf         C.mbedtls_ssl_config
	certs        &SSLCerts = unsafe { nil }
	ctr_drbg     C.mbedtls_ctr_drbg_context
	entropy      C.mbedtls_entropy_context
	handle       int
	duration     time.Duration
	opened       bool
	ip           string
	read_timeout time.Duration

	owns_socket bool
	// alpn_list is a NUL-terminated C array of pointers to the protocol
	// strings in config.alpn_protocols. mbedtls stores this pointer without
	// copying, so it must outlive the SSL config; it is freed in shutdown().
	alpn_list &&char = unsafe { nil }
	// last_write_sent reports the most recent write_ptr's progress for retry
	// decisions: 0 = provably nothing was sent (safe to replay), or -1 = the
	// count is indeterminate because a failed/retryable write may have already
	// flushed a record to the peer (TLS cannot prove zero). On full success it
	// equals the bytes written.
	last_write_sent int
}

// SSLListener listens on a TCP port and accepts connection secured with TLS
pub struct SSLListener {
	saddr  string
	config SSLConnectConfig
mut:
	server_fd C.mbedtls_net_context
	ssl       C.mbedtls_ssl_context
	conf      C.mbedtls_ssl_config
	certs     &SSLCerts = unsafe { nil }
	ctr_drbg  C.mbedtls_ctr_drbg_context
	entropy   C.mbedtls_entropy_context
	rng_mutex &sync.Mutex = sync.new_mutex()
	opened    bool
	// alpn_list is a NUL-terminated C array of pointers to the protocol
	// strings in config.alpn_protocols, advertised by accepted connections.
	// It must outlive the SSL config and is freed in shutdown().
	alpn_list &&char = unsafe { nil }
	// handle		int
	// duration	time.Duration
}

// create a new SSLListener binding to `saddr`
pub fn new_ssl_listener(saddr string, config SSLConnectConfig) !&SSLListener {
	mut listener := &SSLListener{
		saddr:  saddr
		config: config
	}
	listener.init()!
	listener.opened = true
	return listener
}

// finish the listener and clean up resources
pub fn (mut l SSLListener) shutdown() ! {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	if unsafe { l.certs != nil } {
		l.certs.cleanup()
	}
	C.mbedtls_ssl_free(&l.ssl)
	C.mbedtls_ssl_config_free(&l.conf)
	free_rng(mut l.ctr_drbg, mut l.entropy)
	if l.alpn_list != unsafe { nil } {
		unsafe {
			C.free(l.alpn_list)
			l.alpn_list = nil
		}
	}
	if l.opened {
		C.mbedtls_net_free(&l.server_fd)
	}
}

// internal function to init and bind the listener
fn (mut l SSLListener) init() ! {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}

	lhost, lport := net.split_address(l.saddr)!
	if l.config.cert == '' || l.config.cert_key == '' {
		return error('net.mbedtls SSLListener.init, no certificate or key provided')
	}
	if l.config.validate && l.config.verify == '' {
		return error('net.mbedtls SSLListener.init, no root CA provided')
	}
	C.mbedtls_net_init(&l.server_fd)
	C.mbedtls_ssl_init(&l.ssl)
	C.mbedtls_ssl_config_init(&l.conf)
	init_rng(mut l.ctr_drbg, mut l.entropy)!
	l.certs = &SSLCerts{}
	C.mbedtls_x509_crt_init(&l.certs.client_cert)
	C.mbedtls_pk_init(&l.certs.client_key)

	unsafe {
		C.mbedtls_ssl_conf_rng(&l.conf, tls_listener_rng, l)
	}

	mut ret := 0

	if l.config.in_memory_verification {
		l.certs = new_sslcerts_in_memory_with_rng(l.config.verify, l.config.cert,
			l.config.cert_key, &l.ctr_drbg) or {
			return error('net.mbedtls SSLListener.init, cert failure 1, err: ${err}')
		}
	} else {
		l.certs = new_sslcerts_from_file_with_rng(l.config.verify, l.config.cert,
			l.config.cert_key, &l.ctr_drbg) or {
			return error('net.mbedtls SSLListener.init, cert failure 2, err: ${err}')
		}
	}

	if l.config.validate {
		C.mbedtls_ssl_conf_authmode(&l.conf, C.MBEDTLS_SSL_VERIFY_REQUIRED)
	}

	mut bind_ip := unsafe { nil }
	if lhost != '' {
		bind_ip = voidptr(lhost.str)
	}
	bind_port := lport.str()

	ret = C.mbedtls_net_bind(&l.server_fd, bind_ip, voidptr(bind_port.str), C.MBEDTLS_NET_PROTO_TCP)

	if ret != 0 {
		return error_with_code("net.mbedtls SSLListener.init, mbedtls_net_bind can't bind to ${l.saddr} error ret: ${ret}",
			ret)
	}

	ret = C.mbedtls_ssl_config_defaults(&l.conf, C.MBEDTLS_SSL_IS_SERVER,
		C.MBEDTLS_SSL_TRANSPORT_STREAM, C.MBEDTLS_SSL_PRESET_DEFAULT)
	if ret != 0 {
		return error_with_code("net.mbedtls SSLListener.init, mbedtls_ssl_config_defaults can't set config defaults ret: ${ret}",
			ret)
	}
	listener_read_timeout := ssl_listener_read_timeout(l.config)
	$if trace_mbedtls_timeouts ? {
		dump(listener_read_timeout)
	}
	C.mbedtls_ssl_conf_read_timeout(&l.conf, ssl_read_timeout_ms(listener_read_timeout))

	C.mbedtls_ssl_conf_ca_chain(&l.conf, &l.certs.cacert, unsafe { nil })
	ret = C.mbedtls_ssl_conf_own_cert(&l.conf, &l.certs.client_cert, &l.certs.client_key)
	if ret != 0 {
		return error_with_code("net.mbedtls SSLListener.init, mbedtls_ssl_conf_own_cert can't load certificate ret: ${ret}",
			ret)
	}

	// Advertise ALPN protocols for accepted connections to select from.
	// See the matching client-side logic in SSLConn.init for lifetime notes.
	if l.config.alpn_protocols.len > 0 {
		n := l.config.alpn_protocols.len
		l.alpn_list = unsafe { &&char(C.malloc(isize((n + 1) * int(sizeof(voidptr))))) }
		if l.alpn_list == unsafe { nil } {
			return error('net.mbedtls SSLListener.init, failed to allocate ALPN list')
		}
		unsafe {
			for i, proto in l.config.alpn_protocols {
				l.alpn_list[i] = &char(proto.str)
			}
			l.alpn_list[n] = &char(0)
		}
		ret = C.mbedtls_ssl_conf_alpn_protocols(&l.conf, voidptr(l.alpn_list))
		if ret != 0 {
			return error_with_code('net.mbedtls SSLListener.init, mbedtls_ssl_conf_alpn_protocols failed ret: ${ret}',
				ret)
		}
	}

	ret = C.mbedtls_ssl_setup(&l.ssl, &l.conf)
	if ret != 0 {
		return error_with_code("net.mbedtls SSLListener.init, mbedtls_ssl_setup can't setup ssl ret: ${ret}",
			ret)
	}

	if get_cert_callback := l.config.get_certificate {
		l.init_sni(get_cert_callback)
	}
}

fn tls_listener_rng(p_rng voidptr, output &u8, output_len usize) int {
	mut listener := unsafe { &SSLListener(p_rng) }
	listener.rng_mutex.lock()
	defer {
		listener.rng_mutex.unlock()
	}
	return C.mbedtls_ctr_drbg_random(&listener.ctr_drbg, output, output_len)
}

// setup SNI callback
fn (mut l SSLListener) init_sni(get_cert_callback fn (mut SSLListener, string) !&SSLCerts) {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	C.mbedtls_ssl_conf_sni(&l.conf, fn [get_cert_callback, mut l] (p_info voidptr, ssl &C.mbedtls_ssl_context, name &u8, lng usize) int {
		host := unsafe { name.vstring_literal_with_len(int(lng)) }
		if certs := get_cert_callback(mut l, host) {
			return C.mbedtls_ssl_set_hs_own_cert(ssl, &certs.client_cert, &certs.client_key)
		} else {
			return -1
		}
	}, &l.conf)
}

// accepts a new connection and returns a SSLConn of the connected client
pub fn (mut l SSLListener) accept() !&SSLConn {
	mut conn := l.accept_tcp_connection()!

	C.mbedtls_ssl_init(&conn.ssl)
	C.mbedtls_ssl_config_init(&conn.conf)
	ret := C.mbedtls_ssl_setup(&conn.ssl, &l.conf)
	if ret != 0 {
		conn.shutdown() or {}
		return error_with_code('net.mbedtls SSLListener.accept, mbedtls_ssl_setup SSL setup failed ret: ${ret}',
			ret)
	}

	C.mbedtls_ssl_set_bio(&conn.ssl, &conn.server_fd, C.mbedtls_net_send, C.mbedtls_net_recv,
		C.mbedtls_net_recv_timeout)
	conn.server_handshake(net.infinite_timeout)!
	return conn
}

fn (mut l SSLListener) accept_tcp_connection() !&SSLConn {
	mut conn := &SSLConn{
		config:       l.config
		duration:     ssl_listener_read_timeout(l.config)
		read_timeout: ssl_listener_read_timeout(l.config)
		opened:       true
	}
	ip := [16]u8{}
	iplen := usize(0)

	ret := C.mbedtls_net_accept(&l.server_fd, &conn.server_fd, &ip, 16, &iplen)
	if ret != 0 {
		return error_with_code("net.mbedtls SSLListener.accept, mbedtls_net_accept can't accept connection ret: ${ret}",
			ret)
	}
	conn.handle = conn.server_fd.fd
	conn.owns_socket = true
	if iplen == 4 {
		conn.ip = '${ip[0]}.${ip[1]}.${ip[2]}.${ip[3]}'
	}
	return conn
}

// do_handshake_loop drives the non-blocking TLS server handshake to completion
// (or `deadline`). It never calls shutdown: on any error it just returns, leaving
// cleanup to the caller. server_handshake wraps it for the synchronous accept
// path (self-shutdown on error); the threaded server path (complete_handshake)
// lets its worker defer own the single shutdown instead.
fn (mut conn SSLConn) do_handshake_loop(deadline time.Time) ! {
	mut ret := C.mbedtls_ssl_handshake(&conn.ssl)
	for ret != 0 {
		match ret {
			C.MBEDTLS_ERR_SSL_WANT_READ {
				conn.wait_for_read(ssl_remaining_timeout(deadline))!
			}
			C.MBEDTLS_ERR_SSL_WANT_WRITE {
				conn.wait_for_write(ssl_remaining_timeout(deadline))!
			}
			else {
				return error_with_code('net.mbedtls SSLListener.accept, mbedtls_ssl_handshake failed 1; handshake ret: ${ret}',
					ret)
			}
		}

		ret = C.mbedtls_ssl_handshake(&conn.ssl)
	}
}

fn (mut conn SSLConn) server_handshake(timeout time.Duration) ! {
	deadline := ssl_timeout_deadline(timeout)
	conn.do_handshake_loop(deadline) or {
		conn.shutdown() or {
			$if trace_ssl ? {
				eprintln('${@METHOD} shutdown ---> res: ${err}')
			}
		}
		return err
	}
}

// accept_with_timeout waits up to `timeout` for a new client before accepting it.
pub fn (mut l SSLListener) accept_with_timeout(timeout time.Duration) !&SSLConn {
	return l.accept_with_timeouts(timeout, timeout)
}

// accept_raw_with_timeout waits up to `accept_timeout` for a new client, accepts
// the raw TCP connection and sets up its (non-blocking) SSL context, but does NOT
// perform the TLS handshake. The returned conn is non-blocking with a non-blocking
// bio; the caller must run conn.complete_handshake to finish negotiation. This lets
// the threaded server accept on one thread and handshake on a worker thread.
pub fn (mut l SSLListener) accept_raw_with_timeout(accept_timeout time.Duration) !&SSLConn {
	wait_for(l.server_fd.fd, .read, accept_timeout)!
	mut conn := l.accept_tcp_connection()!

	C.mbedtls_ssl_init(&conn.ssl)
	C.mbedtls_ssl_config_init(&conn.conf)
	net.set_blocking(conn.handle, false) or {
		conn.shutdown() or {}
		return err
	}
	ret := C.mbedtls_ssl_setup(&conn.ssl, &l.conf)
	if ret != 0 {
		conn.shutdown() or {}
		return error_with_code('net.mbedtls SSLListener.accept, mbedtls_ssl_setup SSL setup failed ret: ${ret}',
			ret)
	}

	C.v_mbedtls_ssl_set_bio_nonblocking(&conn.ssl, &conn.server_fd)
	return conn
}

// complete_handshake finishes the TLS server handshake on a conn returned by
// accept_raw_with_timeout, waiting up to `timeout`, then restores blocking mode
// and the blocking bio. It never calls shutdown: on any error it returns and the
// caller owns cleanup (so the conn is shut down exactly once, by the caller).
pub fn (mut conn SSLConn) complete_handshake(timeout time.Duration) ! {
	deadline := ssl_timeout_deadline(timeout)
	conn.do_handshake_loop(deadline)!
	net.set_blocking(conn.handle, true)!
	C.mbedtls_ssl_set_bio(&conn.ssl, &conn.server_fd, C.mbedtls_net_send, C.mbedtls_net_recv,
		C.mbedtls_net_recv_timeout)
}

// accept_with_timeouts waits up to `accept_timeout` for a new client, then
// waits up to `handshake_timeout` for the TLS server handshake to complete.
pub fn (mut l SSLListener) accept_with_timeouts(accept_timeout time.Duration, handshake_timeout time.Duration) !&SSLConn {
	mut conn := l.accept_raw_with_timeout(accept_timeout)!
	conn.complete_handshake(handshake_timeout) or {
		conn.shutdown() or {}
		return err
	}
	return conn
}

@[params]
pub struct SSLConnectConfig {
pub:
	verify   string // the path to a rootca.pem file, containing trusted CA certificate(s)
	cert     string // the path to a cert.pem file, containing client certificate(s) for the request
	cert_key string // the path to a key.pem file, containing private keys for the client certificate(s)
	validate bool   // set this to true, if you want to stop requests, when their certificates are found to be invalid

	in_memory_verification bool // if true, verify, cert, and cert_key are read from memory, not from a file

	get_certificate ?fn (mut SSLListener, string) !&SSLCerts

	read_timeout time.Duration = default_mbedtls_client_read_timeout // the SSL client read timeout

	alpn_protocols []string // the list of ALPN protocols to advertise, e.g. ['h2', 'http/1.1']; empty means no ALPN extension is sent
}

fn ssl_read_timeout_ms(timeout time.Duration) u32 {
	if timeout <= 0 || timeout == net.infinite_timeout {
		return 0
	}
	timeout_ms := timeout.milliseconds()
	if timeout_ms > i64(max_u32) {
		return max_u32
	}
	return u32(timeout_ms)
}

fn ssl_listener_read_timeout(config SSLConnectConfig) time.Duration {
	if config.read_timeout == default_mbedtls_client_read_timeout {
		return default_mbedtls_server_read_timeout
	}
	return config.read_timeout
}

fn ssl_timeout_deadline(timeout time.Duration) time.Time {
	if timeout <= 0 || timeout == net.infinite_timeout {
		return time.unix(0)
	}
	return time.now().add(timeout)
}

fn ssl_remaining_timeout(deadline time.Time) time.Duration {
	if deadline.unix() == 0 {
		return net.infinite_timeout
	}
	remaining := deadline - time.now()
	if remaining <= 0 {
		return time.nanosecond
	}
	return remaining
}

// read_timeout returns the current SSL read timeout.
pub fn (s &SSLConn) read_timeout() time.Duration {
	return s.read_timeout
}

// set_read_timeout sets the SSL read timeout for subsequent operations.
pub fn (mut s SSLConn) set_read_timeout(timeout time.Duration) {
	s.read_timeout = timeout
	s.duration = timeout
	C.mbedtls_ssl_conf_read_timeout(&s.conf, ssl_read_timeout_ms(timeout))
}

// new_ssl_conn returns a new SSLConn with the given config.
pub fn new_ssl_conn(config SSLConnectConfig) !&SSLConn {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	mut conn := &SSLConn{
		config:       config
		duration:     config.read_timeout
		read_timeout: config.read_timeout
	}
	conn.init()!
	return conn
}

// Select operation
enum Select {
	read
	write
	except
}

// close terminates the ssl connection and does cleanup
pub fn (mut s SSLConn) close() ! {
	s.shutdown()!
}

// shutdown terminates the ssl connection and does cleanup
pub fn (mut s SSLConn) shutdown() ! {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	if !s.opened {
		return error('net.mbedtls SSLConn.shutdown, connection was not open')
	}
	// Mark closed before freeing so a second shutdown (e.g. a worker defer racing
	// close_idle) is a harmless no-op rather than a double-free of the mbedtls
	// contexts below.
	s.opened = false
	if unsafe { s.certs != nil } {
		C.mbedtls_x509_crt_free(&s.certs.cacert)
		C.mbedtls_x509_crt_free(&s.certs.client_cert)
		C.mbedtls_pk_free(&s.certs.client_key)
	}
	C.mbedtls_ssl_free(&s.ssl)
	C.mbedtls_ssl_config_free(&s.conf)
	free_rng(mut s.ctr_drbg, mut s.entropy)
	if s.alpn_list != unsafe { nil } {
		unsafe {
			C.free(s.alpn_list)
			s.alpn_list = nil
		}
	}
	if s.owns_socket {
		net.shutdown(s.handle)
		net.close(s.handle)!
	}
}

// negotiated_alpn returns the ALPN protocol selected during the TLS
// handshake (e.g. 'h2' or 'http/1.1'), or an empty string if no protocol
// was negotiated.
pub fn (s &SSLConn) negotiated_alpn() string {
	// mbedtls_ssl_get_alpn_protocol returns a `const char *`; cast away const
	// for V, since we only read from it (and copy it below).
	p := &char(C.mbedtls_ssl_get_alpn_protocol(&s.ssl))
	if p == unsafe { nil } {
		return ''
	}
	return unsafe { cstring_to_vstring(p) }
}

// connect to server using mbedtls
fn (mut s SSLConn) init() ! {
	$if trace_ssl ? {
		eprintln(@METHOD)
	}
	C.mbedtls_net_init(&s.server_fd)
	C.mbedtls_ssl_init(&s.ssl)
	C.mbedtls_ssl_config_init(&s.conf)
	init_rng(mut s.ctr_drbg, mut s.entropy)!
	mut ret := 0
	ret = C.mbedtls_ssl_config_defaults(&s.conf, C.MBEDTLS_SSL_IS_CLIENT,
		C.MBEDTLS_SSL_TRANSPORT_STREAM, C.MBEDTLS_SSL_PRESET_DEFAULT)
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.init, mbedtls_ssl_config_defaults failed to set SSL configuration ret: ${ret}',
			ret)
	}
	$if trace_mbedtls_timeouts ? {
		dump(s.read_timeout)
	}
	s.set_read_timeout(s.read_timeout)

	unsafe {
		C.mbedtls_ssl_conf_rng(&s.conf, C.mbedtls_ctr_drbg_random, &s.ctr_drbg)
	}

	// Advertise ALPN protocols (e.g. ['h2', 'http/1.1']) when requested.
	// mbedtls expects a NUL-terminated array of NUL-terminated C strings, and
	// keeps the pointer without copying, so both the array and the backing
	// strings must outlive the config. The strings live in s.config; the array
	// is allocated here and freed in shutdown().
	if s.config.alpn_protocols.len > 0 {
		n := s.config.alpn_protocols.len
		s.alpn_list = unsafe { &&char(C.malloc(isize((n + 1) * int(sizeof(voidptr))))) }
		if s.alpn_list == unsafe { nil } {
			return error('net.mbedtls SSLConn.init, failed to allocate ALPN list')
		}
		unsafe {
			for i, proto in s.config.alpn_protocols {
				s.alpn_list[i] = &char(proto.str)
			}
			s.alpn_list[n] = &char(0)
		}
		ret = C.mbedtls_ssl_conf_alpn_protocols(&s.conf, voidptr(s.alpn_list))
		if ret != 0 {
			return error_with_code('net.mbedtls SSLConn.init, mbedtls_ssl_conf_alpn_protocols failed ret: ${ret}',
				ret)
		}
	}
	if s.config.verify != '' || s.config.cert != '' || s.config.cert_key != '' {
		s.certs = &SSLCerts{}
		C.mbedtls_x509_crt_init(&s.certs.cacert)
		C.mbedtls_x509_crt_init(&s.certs.client_cert)
		C.mbedtls_pk_init(&s.certs.client_key)
	}

	if s.config.in_memory_verification {
		if s.config.verify != '' {
			ret = C.mbedtls_x509_crt_parse(&s.certs.cacert, s.config.verify.str,

				s.config.verify.len + 1)
		}
		if s.config.cert != '' {
			ret = C.mbedtls_x509_crt_parse(&s.certs.client_cert, s.config.cert.str,

				s.config.cert.len + 1)
		}
		if s.config.cert_key != '' {
			unsafe {
				ret = C.mbedtls_pk_parse_key(&s.certs.client_key, s.config.cert_key.str,

					s.config.cert_key.len + 1, 0, 0, C.mbedtls_ctr_drbg_random, &s.ctr_drbg)
			}
		}
	} else {
		if s.config.verify != '' {
			ret = C.mbedtls_x509_crt_parse_file(&s.certs.cacert, &char(s.config.verify.str))
		}
		if s.config.cert != '' {
			ret = C.mbedtls_x509_crt_parse_file(&s.certs.client_cert, &char(s.config.cert.str))
		}
		if s.config.cert_key != '' {
			unsafe {
				ret = C.mbedtls_pk_parse_keyfile(&s.certs.client_key, &char(s.config.cert_key.str),
					0, C.mbedtls_ctr_drbg_random, &s.ctr_drbg)
			}
		}
	}
	if ret < 0 {
		return error_with_code('net.mbedtls SSLConn.init, failed to set certificates, ret: ${ret}',
			ret)
	}

	if unsafe { s.certs != nil } {
		C.mbedtls_ssl_conf_ca_chain(&s.conf, &s.certs.cacert, 0)
		C.mbedtls_ssl_conf_own_cert(&s.conf, &s.certs.client_cert, &s.certs.client_key)
	}

	if s.config.validate {
		C.mbedtls_ssl_conf_authmode(&s.conf, C.MBEDTLS_SSL_VERIFY_REQUIRED)
	} else {
		C.mbedtls_ssl_conf_authmode(&s.conf, C.MBEDTLS_SSL_VERIFY_OPTIONAL)
	}

	ret = C.mbedtls_ssl_setup(&s.ssl, &s.conf)
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.init, mbedtls_ssl_setup failed to setup SSL connection ret: ${ret}',
			ret)
	}
}

// connect sets up an ssl connection on an existing TCP connection
pub fn (mut s SSLConn) connect(mut tcp_conn net.TcpConn, hostname string) ! {
	$if trace_ssl ? {
		eprintln('${@METHOD} hostname: ${hostname}')
	}
	if s.opened {
		return error('net.mbedtls SSLConn.connect, ssl connection was already open')
	}
	s.handle = tcp_conn.sock.handle
	s.set_read_timeout(tcp_conn.read_timeout())
	mut ret := C.mbedtls_ssl_set_hostname(&s.ssl, &char(hostname.str))
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.connect, mbedtls_ssl_set_hostname failed to set hostname',
			ret)
	}
	s.server_fd.fd = s.handle
	C.mbedtls_ssl_set_bio(&s.ssl, &s.server_fd, C.mbedtls_net_send, C.mbedtls_net_recv,
		C.mbedtls_net_recv_timeout)
	ret = C.mbedtls_ssl_handshake(&s.ssl)
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.connect, mbedtls_ssl_handshake failed 2; ret: ${ret}',
			ret)
	}
	s.opened = true
}

// dial opens an ssl connection on hostname:port
pub fn (mut s SSLConn) dial(hostname string, port int) ! {
	$if trace_ssl ? {
		eprintln('${@METHOD} hostname: ${hostname} | port: ${port}')
	}
	if s.opened {
		return error('net.mbedtls SSLConn.dial, the ssl connection was already open')
	}
	mut connected := false
	defer {
		if !connected {
			if unsafe { s.certs != nil } {
				C.mbedtls_x509_crt_free(&s.certs.cacert)
				C.mbedtls_x509_crt_free(&s.certs.client_cert)
				C.mbedtls_pk_free(&s.certs.client_key)
				s.certs = unsafe { nil }
			}
			C.mbedtls_net_free(&s.server_fd)
			C.mbedtls_ssl_free(&s.ssl)
			C.mbedtls_ssl_config_free(&s.conf)
			free_rng(mut s.ctr_drbg, mut s.entropy)
			s.handle = 0
			s.owns_socket = false
		}
	}
	s.owns_socket = true

	mut ret := C.mbedtls_ssl_set_hostname(&s.ssl, &char(hostname.str))
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.dial, failed to set hostname', ret)
	}

	port_str := port.str()
	ret = C.mbedtls_net_connect(&s.server_fd, &char(hostname.str), &char(port_str.str),
		C.MBEDTLS_NET_PROTO_TCP)
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.dial, failed to connect to host', ret)
	}
	C.mbedtls_ssl_set_bio(&s.ssl, &s.server_fd, C.mbedtls_net_send, C.mbedtls_net_recv,
		C.mbedtls_net_recv_timeout)
	s.handle = s.server_fd.fd
	ret = C.mbedtls_ssl_handshake(&s.ssl)
	if ret != 0 {
		return error_with_code('net.mbedtls SSLConn.dial, mbedtls_ssl_handshake failed 3; ret: ${ret}',
			ret)
	}
	s.opened = true
	connected = true
}

// addr retrieves the local ip address and port number for this connection
pub fn (s &SSLConn) addr() !net.Addr {
	return net.addr_from_socket_handle(s.handle)
}

// peer_addr retrieves the ip address and port number used by the peer
pub fn (s &SSLConn) peer_addr() !net.Addr {
	return net.peer_addr_from_socket_handle(s.handle)
}

// socket_read_into_ptr reads `len` bytes into `buf`
pub fn (mut s SSLConn) socket_read_into_ptr(buf_ptr &u8, len int) !int {
	mut res := 0
	$if trace_ssl ? {
		defer(fn) {
			if len > 0 {
				eprintln('${@METHOD} res: ${res}: buf_ptr: ${voidptr(buf_ptr):x}, len: ${len}, hex: ${unsafe { buf_ptr.vbytes(len).hex() }} data: `${unsafe { buf_ptr.vstring_with_len(len) }}`')
			}
		}
	}

	deadline := ssl_timeout_deadline(s.duration)
	// s.wait_for_read(deadline - time.now())!
	for {
		res = C.mbedtls_ssl_read(&s.ssl, buf_ptr, len)
		if res > 0 {
			return res
		} else if res == 0 {
			$if trace_ssl ? {
				eprintln('${@METHOD} ---> res: io.Eof')
			}
			return io.Eof{}
		} else {
			match res {
				C.MBEDTLS_ERR_SSL_WANT_READ {
					s.wait_for_read(ssl_remaining_timeout(deadline)) or {
						$if trace_ssl ? {
							eprintln('${@METHOD} ---> res: ${err}, C.MBEDTLS_ERR_SSL_WANT_READ')
						}
						return err
					}
				}
				C.MBEDTLS_ERR_SSL_WANT_WRITE {
					s.wait_for_write(ssl_remaining_timeout(deadline)) or {
						$if trace_ssl ? {
							eprintln('${@METHOD} ---> res: ${err}, C.MBEDTLS_ERR_SSL_WANT_WRITE')
						}
						return err
					}
				}
				C.MBEDTLS_ERR_SSL_RECEIVED_NEW_SESSION_TICKET {
					// TLS 1.3 servers can deliver tickets asynchronously while the
					// connection is otherwise healthy. Keep reading application data.
					continue
				}
				C.MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY {
					$if trace_ssl ? {
						eprintln('${@METHOD} ---> res: 0 C.MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY')
					}
					return 0
				}
				C.MBEDTLS_ERR_SSL_TIMEOUT {
					$if trace_ssl ? {
						eprintln('${@METHOD} ---> res: C.MBEDTLS_ERR_SSL_TIMEOUT')
					}
					return error_with_code('net.mbedtls SSLConn.socket_read_into_ptr, did not receive any data within ${s.read_timeout.milliseconds()}ms. Use conn.set_read_timeout(...) to increase the timeout',
						res)
				}
				else {
					$if trace_ssl ? {
						eprintln('${@METHOD} ---> res: could not read using SSL')
					}
					return error_with_code('net.mbedtls SSLConn.socket_read_into_ptr, could not read using SSL',
						res)
				}
			}
		}
	}
	// Dead code, just to satisfy the compiler:
	return error('net.mbedtls SSLConn.socket_read_into_ptr, unknown error')
}

// read reads data from the ssl connection into `buffer`
pub fn (mut s SSLConn) read(mut buffer []u8) !int {
	$if trace_ssl ? {
		eprintln('${@METHOD} buffer.len: ${buffer.len}')
	}
	return s.socket_read_into_ptr(&u8(buffer.data), buffer.len)
}

// write_ptr writes `len` bytes from `bytes` to the ssl connection
pub fn (mut s SSLConn) write_ptr(bytes &u8, len int) !int {
	mut total_sent := 0
	$if trace_ssl ? {
		defer(fn) {
			eprintln('${@METHOD} total_sent: ${total_sent}, bytes: ${voidptr(bytes):x}, len: ${len}, hex: ${unsafe { bytes.vbytes(len).hex() }}, data:-=-=-=-\n${unsafe { bytes.vstring_with_len(len) }}\n-=-=-=-')
		}
	}

	s.last_write_sent = 0
	deadline := ssl_timeout_deadline(s.duration)
	unsafe {
		mut ptr_base := bytes
		for total_sent < len {
			ptr := ptr_base + total_sent
			remaining := len - total_sent
			mut sent := C.mbedtls_ssl_write(&s.ssl, ptr, remaining)
			if sent <= 0 {
				// The write did not fully complete; a retryable error can leave a
				// record partially flushed, so the sent count is no longer
				// provable. Mark it indeterminate (a later full success below
				// resets it to the exact length).
				s.last_write_sent = -1
				match sent {
					C.MBEDTLS_ERR_SSL_WANT_READ {
						s.wait_for_read(ssl_remaining_timeout(deadline))!
						continue
					}
					C.MBEDTLS_ERR_SSL_WANT_WRITE {
						s.wait_for_write(ssl_remaining_timeout(deadline))!
						continue
					}
					else {
						$if trace_ssl ? {
							eprintln('${@METHOD} ---> res: could not write SSL, sent: ${sent}')
						}
						return error_with_code('net.mbedtls SSLConn.write_ptr, could not write using SSL',
							sent)
					}
				}
			}
			total_sent += sent
			s.last_write_sent = total_sent
		}
	}
	return total_sent
}

// write writes data from `bytes` to the ssl connection
pub fn (mut s SSLConn) write(bytes []u8) !int {
	return s.write_ptr(&u8(bytes.data), bytes.len)
}

// write_string writes a string to the ssl connection
pub fn (mut s SSLConn) write_string(str string) !int {
	$if trace_ssl ? {
		eprintln('${@METHOD} str: ${str}')
	}
	return s.write_ptr(str.str, str.len)
}

// Select waits for an io operation (specified by parameter `test`) to be available
fn select(handle int, test Select, timeout time.Duration) !bool {
	$if trace_ssl ? {
		eprintln('${@METHOD} handle: ${handle}, timeout: ${timeout}')
	}
	set := C.fd_set{}
	C.FD_ZERO(&set)
	C.FD_SET(handle, &set)

	is_infinite := timeout <= 0 || timeout == net.infinite_timeout
	deadline := ssl_timeout_deadline(timeout)
	mut remaining_time := if is_infinite { i64(0) } else { timeout.milliseconds() }
	for is_infinite || remaining_time > 0 {
		seconds := remaining_time / 1000
		microseconds := (remaining_time % 1000) * 1000

		tt := C.timeval{
			tv_sec:  u64(seconds)
			tv_usec: u64(microseconds)
		}
		timeval_timeout := if is_infinite { &C.timeval(unsafe { nil }) } else { &tt }

		mut res := -1
		match test {
			.read {
				res = net.socket_error(C.select(handle + 1, &set, C.NULL, C.NULL, timeval_timeout))!
			}
			.write {
				res = net.socket_error(C.select(handle + 1, C.NULL, &set, C.NULL, timeval_timeout))!
			}
			.except {
				res = net.socket_error(C.select(handle + 1, C.NULL, C.NULL, &set, timeval_timeout))!
			}
		}

		if res < 0 {
			if C.errno == C.EINTR {
				// errno is 4, Spurious wakeup from signal, keep waiting
				if !is_infinite {
					remaining_time = ssl_remaining_timeout(deadline).milliseconds()
				}
				continue
			}
			cerr := C.errno
			return error_with_code('net.mbedtls select, failed, res: ${res}', cerr)
		} else if res == 0 {
			return net.err_timed_out
		}

		res = C.FD_ISSET(handle, &set)
		$if trace_ssl ? {
			eprintln('${@METHOD} ---> res: ${res}')
		}
		return res != 0
	}

	return net.err_timed_out
}

// wait_for wraps the common wait code
fn wait_for(handle int, what Select, timeout time.Duration) ! {
	ready := select(handle, what, timeout)!
	if ready {
		return
	}

	return net.err_timed_out
}

// wait_for_write waits for a write io operation to be available
fn (mut s SSLConn) wait_for_write(timeout time.Duration) ! {
	return wait_for(s.handle, .write, timeout)
}

// wait_for_read waits for a read io operation to be available
fn (mut s SSLConn) wait_for_read(timeout time.Duration) ! {
	return wait_for(s.handle, .read, timeout)
}