/* SPDX-License-Identifier: GPL-3.0-or-later */
/* Copyright 2021 - 2022, Kim Kuparinen < kimi.h.kuparinen@gmail.com > */

/**
 * @file dispatch.c
 * Syscall dispatch.
 */

#include <apos/canary.h>
#include <apos/debug.h>
#include <apos/uapi.h>

/** Syscall number to syscall handler conversion. */
static const sys_t syscall_table[] = {
	/* noop */
	[SYS_NOOP] = sys_noop,

	/* debugging */
	[SYS_PUTCH] = sys_putch,

	/* mem */
	[SYS_REQ_MEM] = sys_req_mem,
	[SYS_REQ_PMEM] = sys_req_pmem,
	[SYS_REQ_FIXMEM] = sys_req_fixmem,
	[SYS_FREE_MEM] = sys_free_mem,

	/* timers */
	[SYS_TIMEBASE] = sys_timebase,
	[SYS_TICKS] = sys_ticks,
	[SYS_REQ_REL_TIMER] = sys_req_rel_timer,
	[SYS_REQ_ABS_TIMER] = sys_req_abs_timer,
	[SYS_FREE_TIMER] = sys_free_timer,

	/* ipc */
	[SYS_IPC_SERVER] = sys_ipc_server,
	[SYS_IPC_REQ] = sys_ipc_req,
	[SYS_IPC_FWD] = sys_ipc_fwd,
	[SYS_IPC_RESP] = sys_ipc_resp,

	/* proc */
	[SYS_CREATE] = sys_create,
	[SYS_FORK] = sys_fork,
	[SYS_EXEC] = sys_exec,
	[SYS_SWAP] = sys_swap,

	/* conf */
	[SYS_CONF_SET] = sys_conf_set,
	[SYS_CONF_GET] = sys_conf_get,

	[SYS_SET_CAP] = sys_set_cap,
	[SYS_GET_CAP] = sys_get_cap,
	[SYS_CLEAR_CAP] = sys_clear_cap,

	[SYS_POWEROFF] = sys_poweroff,
};

/**
 * Noop syscall handler.
 *
 * @return \ref OK and \c 0.
 */
SYSCALL_DEFINE0(noop)(){
	info("sys_noop\n");
	return (struct sys_ret){ OK, 0, 0, 0, 0, 0 };
}

/**
 * Putch syscall handler.
 *
 * @param a Character to put.
 * @return \ref OK and 0.
 */
SYSCALL_DEFINE1(putch)(sys_arg_t a){
	const char c[2] = {a, 0};
	MAYBE_UNUSED(c);
	dbg((const char *)&c);
	return (struct sys_ret){ OK, 0, 0, 0, 0, 0 };
}

struct sys_ret syscall_dispatch(sys_arg_t syscall, sys_arg_t a, sys_arg_t b,
                                sys_arg_t c, sys_arg_t d, sys_arg_t e)
{
	struct tcb *t = cur_tcb();

	size_t sc = syscall;
	if (sc >= ARRAY_SIZE(syscall_table)) {
		error("Syscall %zu outside allowed range [0 - %zu]\n", sc,
		      ARRAY_SIZE(syscall_table));
		return (struct sys_ret){ ERR_INVAL, 0, 0, 0, 0, 0 };
	}

	sys_t call = syscall_table[sc];
	if (!call) {
		error("Syscall %zu not legitimate value\n", sc);
		return (struct sys_ret){ ERR_INVAL, 0, 0, 0, 0, 0 };
	}

	struct sys_ret r = call(a, b, c, d, e);

	if (check_canary(t)) {
		bug("Syscall %zu overwrote stack canary\n", syscall);
		/** @todo should probably halt, as the system is likely in an
		 * unstable state. */
		return (struct sys_ret){ ERR_INT, 0, 0, 0, 0, 0 };
	}

	return r;
}