/*
 * Copyright (C) 2013, 2014 Ludwig Knüpfer
 * Copyright (C) 2025 carl-tud
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */

/**
 * @defgroup cpu_native_stdio  STDIO for native
 * @ingroup  sys_stdio
 * @brief    Standard input/output backend for native
 * @{
 *
 * This will hook up RIOT's stdio to the host's stdio fds. It is the default
 * stdio implementation of the board `native`.
 *
 * @see @ref cpu_native

 * @}
 */

/**
 * @addtogroup cpu_native
 * @{
 */

/**
 * @file
 * @brief  Native CPU internal symbols
 * @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
 * @author carl-tud
 */
#ifndef NATIVE_INTERNAL_H
#define NATIVE_INTERNAL_H

#include "util/ucontext.h"
#include <stdio.h>
#include <stdint.h>
#include <poll.h>

#include <stdbool.h>
#include <netdb.h>
#include <ifaddrs.h>
#include <time.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/uio.h>
#include <dirent.h>

#include "cpu_conf.h"
#include "thread.h"
#include "sched.h"

#ifdef __cplusplus
extern "C" {
#endif

#include "syscalls.h"

/* MARK: - Internal native CPU API */
/**
 * @name Internal native CPU API
 * @{
 */

/**
 * @brief Prototype for native's internal callbacks
 */
typedef void (*_native_callback_t)(void);

/**
 * @brief Initializes native CPU
 */
void native_cpu_init(void);
/** @} */

/* MARK: - Native Signal Handling */
/**
 * @name Native Signal Handling
 * @{
 */

/**
 * @brief A boolean variable indicating whether interrupts are currently permissible
 * @private
 */
extern volatile bool _native_interrupts_enabled;

/**
 * @brief Pipe yielding signals
 * @private
 *
 * The internal signal handler writes into the write end of this pipe
 */
extern int _signal_pipe_fd[2];

/**
 * @brief Number of currently pending signals
 * @private
 */
extern volatile int _native_pending_signals;

/**
 * @brief Registers signal handlers for the native CPU
 */
void native_interrupt_init(void);

/**
 * @brief Register interrupt handler handler for interrupt signal
 *
 * @param sig Signal number
 * @param handler Signal action function
 *
 * @returns 0 on success, negative number otherwise.
 */
int native_register_interrupt(int sig, _native_callback_t handler);

/**
 * @brief Unregister interrupt handler for interrupt signal
 *
 * @param sig Signal number
 *
 * @returns 0 on success, negative number otherwise.
 */
int native_unregister_interrupt(int sig);

/**
 * @brief Calls signal handlers for pending signal, then exits ISR context and performs context switch
 * @pre Intended to be called from **ISR context**
 * @private
 *
 * The context switch back to userspace is performed using @ref `cpu_switch_context_exit`.
 *
 * @note While it would have been possible to separate this method's functionality into two functions, `setcontext` requires us to have a single function.
 */
void _native_call_sig_handlers_and_switch(void);

/**
 * @brief Switches to ISR context, then enables IRQ and returns to userspace
 *
 * @note This function is implemented in assembly.
 */
extern void _native_sig_leave_tramp(void);
/** @} */


/* MARK: - System Calls */
/**
 * @name System Calls
 *
 * We wrap system calls and syscall-invoking library calls to ensure **no context switches occur during a system call**.
 * @{
 */
/**
 * @brief Number of currently pending system calls
 * @private
 */
extern volatile int _native_pending_syscalls;

/**
 * @brief Increment spending system call counter
 */
static inline void _native_pending_syscalls_up(void) {
    _native_pending_syscalls += 1;
}

/**
 * @brief Decrements pending system call counter
 */
static inline void _native_pending_syscalls_down(void) {
    _native_pending_syscalls -= 1;
}

/**
 * @brief Executes post-syscall logic
 * @private
 *
 * Decrements internal pending syscall counter.
 *
 * If there are other pending system calls and when not already in an ISR context, this function switches to the ISR context and
 * calls signals handlers. This is done through @ref `_native_call_sig_handlers_and_switch`. Returns to userspace
 * thereafter.
 */
void _native_syscall_leave(void);

/**
 * @brief Executes pre-syscall logic
 * @private
 *
 * Increments internal pending syscall counter.
 */
void _native_syscall_enter(void);

/**
 * @brief Registers system calls.
 *
 * Wraps syscall functions from the standard library.
 */
void _native_init_syscalls(void);
/** @} */

/* MARK: - Native Context Switching */
/**
 * @name Native Context Switching
 * @{
 */

/**
 * @brief Points to instruction in userspace where RIOT left off and switched to ISR context
 */
extern volatile uintptr_t _native_user_fptr;

/**
 * @brief A boolean variable indicating whether program execution currently takes place in an ISR context
 */
extern volatile int _native_in_isr;

/**
 * @brief Stack used in ISR context
 */
extern char _isr_stack[THREAD_STACKSIZE_DEFAULT];

/**
 * @brief ISR context
 */
extern ucontext_t *_native_isr_context;

/**
 * @brief Resets internal `in_ISR` barrier switch and resumes execution on the currently scheduled thread
 * @pre Intended to be executed in userspace
 * @private
 *
 * @note This function is implemented in assembly to preserve registers. See `native.S`
 */
extern void _native_isr_leave(void);

/**
 * @brief Makes ISR context so that execution continues at `func` when the context is applied
 *
 * @param func Function executed when `_native_isr_context` is applied
 */
static inline void _native_isr_context_make(void (*func)(void)) {
    _native_isr_context->uc_stack.ss_sp = _isr_stack;
    _native_isr_context->uc_stack.ss_size = sizeof(_isr_stack);
    _native_isr_context->uc_stack.ss_flags = 0;

    /* Create the ISR context, will execute _isr_schedule_and_switch */
    makecontext(_native_isr_context, func, 0);
}

/**
 * @brief Retrieves user context
 * @returns `ucontext_t`
 */
static inline ucontext_t* _native_user_context(void) {
    /* Use intermediate cast to uintptr_t to silence -Wcast-align.
     * stacks are manually word aligned in thread_static_init() */
    return (ucontext_t *)(uintptr_t)thread_get_active()->sp;
}
/** @} */

/* MARK: - Native Process State */
/**
 * @name Native Process State
 * @{
 */
/**
 * @brief Program name
 * @private
 */
extern const char *_progname;

/**
 * @brief Program argument values
 * @private
 */
extern char **_native_argv;

/**
 * @brief Process Identifier
 * @private
 */
extern pid_t _native_pid;

/**
 * @brief Process Identifier / CPUID ???
 * @private
 */
extern pid_t _native_id;

/**
 * @brief Random number generator seed value
 * @private
 */
extern unsigned int _native_rng_seed;

/**
 * @brief Random number generator mode
 * @private
 *
 * - `0`: Use `/dev/random`
 * - `1`: Use `random(3)`
 */
extern int _native_rng_mode;
/** @} */

/* MARK: - Native Read/Write Methods */
/**
 * @name Native Read/Write Methods
 * @{
 */
/**
 * @brief Reads file, populates given buffer
 */
ssize_t _native_read(int fd, void *buf, size_t count);

/**
 * @brief Writes given data into file
 */
ssize_t _native_write(int fd, const void *buf, size_t count);

/**
 * @brief Performs a vectored write operation
 */
ssize_t _native_writev(int fildes, const struct iovec *iov, int iovcnt);
/** @} */

#ifdef __cplusplus
}
#endif

#endif /* NATIVE_INTERNAL_H */
/** @} */