/*
 * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Hyra nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/proc.h>
#include <sys/exec.h>
#include <sys/mman.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/syscall.h>
#include <sys/atomic.h>
#include <sys/signal.h>
#include <sys/limits.h>
#include <sys/sched.h>
#include <vm/dynalloc.h>
#include <string.h>

#define pr_trace(fmt, ...) kprintf("spawn: " fmt, ##__VA_ARGS__)
#define pr_error(...) pr_trace(__VA_ARGS__)

static volatile size_t nthreads = 0;

struct spawn_args {
    char path[PATH_MAX];
};

static inline void
try_free_data(void *p)
{
    if (p != NULL) {
        dynfree(p);
    }
}

static void
spawn_thunk(void)
{
    const char *path;
    char pathbuf[PATH_MAX];
    struct proc *cur;
    struct execve_args execve_args;
    struct spawn_args *args;
    char *argv[] = { NULL, NULL };
    char *envp[] = { NULL };

    cur = this_td();
    args = cur->spawn_data;
    path = args->path;
    memcpy(pathbuf, path, strlen(path));

    argv[0] = (char *)pathbuf;
    execve_args.pathname = argv[0];
    execve_args.argv = argv;
    execve_args.envp = envp;

    path = NULL;
    dynfree(args);
    execve(cur, &execve_args);
    __builtin_unreachable();
}

/*
 * Spawn a new process
 *
 * @cur: Parent (current) process.
 * @func: Address of start code.
 * @p: Data to pass to new process (used for user procs)
 * @flags: Spawn flags.
 * @newprocp: If not NULL, will contain the new process.
 *
 * Returns the PID of the child on success, otherwise an
 * errno value that is less than zero.
 *
 * XXX: `p` is only used by sys_spawn and should be set
 *      to NULL if called in the kernel.
 */
pid_t
spawn(struct proc *cur, void(*func)(void), void *p, int flags, struct proc **newprocp)
{
    struct proc *newproc;
    struct mmap_lgdr *mlgdr;
    int error;

    newproc = dynalloc(sizeof(*newproc));
    if (newproc == NULL) {
        pr_error("could not alloc proc (-ENOMEM)\n");
        try_free_data(p);
        return -ENOMEM;
    }

    mlgdr = dynalloc(sizeof(*mlgdr));
    if (mlgdr == NULL) {
        dynfree(newproc);
        try_free_data(p);
        pr_error("could not alloc proc mlgdr (-ENOMEM)\n");
        return -ENOMEM;
    }

    memset(newproc, 0, sizeof(*newproc));
    error = md_spawn(newproc, cur, (uintptr_t)func);
    if (error < 0) {
        dynfree(newproc);
        dynfree(mlgdr);
        try_free_data(p);
        pr_error("error initializing proc\n");
        return error;
    }

    /* Set proc output if we can */
    if (newprocp != NULL) {
        *newprocp = newproc;
    }

    if (!ISSET(cur->flags, PROC_LEAFQ)) {
        TAILQ_INIT(&cur->leafq);
        cur->flags |= PROC_LEAFQ;
    }

    /* Add to parent leafq */
    TAILQ_INSERT_TAIL(&cur->leafq, newproc, leaf_link);
    atomic_inc_int(&cur->nleaves);
    newproc->parent = cur;
    newproc->spawn_data = p;

    /* Initialize the mmap ledger */
    mlgdr->nbytes = 0;
    RBT_INIT(lgdr_entries, &mlgdr->hd);
    newproc->mlgdr = mlgdr;

    newproc->pid = ++nthreads;
    signals_init(newproc);
    sched_enqueue_td(newproc);
    return newproc->pid;
}

/*
 * Get the child of a process by PID.
 *
 * @cur: Parent process.
 * @pid: Child PID.
 *
 * Returns NULL if no child was found.
 */
struct proc *
get_child(struct proc *cur, pid_t pid)
{
    struct proc *procp;

    TAILQ_FOREACH(procp, &cur->leafq, leaf_link) {
        if (procp->pid == pid) {
            return procp;
        }
    }

    return NULL;
}

/*
 * arg0: The file /path/to/executable
 * arg1: Optional flags (`flags')
 */
scret_t
sys_spawn(struct syscall_args *scargs)
{
    struct spawn_args *args;
    const char *u_path;
    struct proc *td;
    int flags, error;

    td = this_td();
    flags = scargs->arg1;
    u_path = (const char *)scargs->arg0;

    args = dynalloc(sizeof(*args));
    if (args == NULL) {
        return -ENOMEM;
    }

    error = copyinstr(u_path, args->path, sizeof(args->path));
    if (error < 0) {
        dynfree(args);
        return error;
    }

    return spawn(td, spawn_thunk, args, flags, NULL);
}