#define MODULE "exec"

#include "assert.h"
#include "errno.h"
#include "interrupts/Interrupts.h"
#include "memory/MemoryManager.h"
#include "memory/PMM.h"
#include "std/stdlib.h"
#include "std/string.h"
#include "sys/elf/ELFLoader.h"
#include "thread/Scheduler.h"

void sys_exec(Context* context, const char* pathname)
{
    if (!pathname)
    {
        context->rax = -EFAULT;
        return;
    }

    kinfoln("exec(): executing %s", pathname);

    VFS::Node* program = VFS::resolve_path(pathname);
    if (!program)
    {
        context->rax = -ENOENT;
        return;
    }

    if (program->type == VFS_DIRECTORY)
    {
        context->rax = -EISDIR;
        return;
    }

    long memusage;
    if ((memusage = ELFLoader::check_elf_image(program)) < 0)
    {
        context->rax = -ENOEXEC;
        return;
    }

    uint64_t allocated_stack = (uint64_t)MemoryManager::get_pages(TASK_PAGES_IN_STACK, MAP_READ_WRITE | MAP_USER);
    if (!allocated_stack)
    {
        context->rax = -ENOMEM;
        return;
    }

    if ((uint64_t)memusage > PMM::get_free())
    {
        MemoryManager::release_pages((void*)allocated_stack, TASK_PAGES_IN_STACK);
        context->rax = -ENOMEM;
        return;
    }

    Interrupts::disable();
    ASSERT(!Interrupts::are_enabled()); // This part is pretty sensitive.

    Task* task = Scheduler::current_task();
    ASSERT(task);

    // At this point, pretty much nothing can fail.

    ELFLoader::release_elf_image(Scheduler::current_task()->image);

    ELFImage* image = ELFLoader::load_elf_from_vfs(program);
    ASSERT(image); // If check_elf_image succeeded, load_elf_from_vfs MUST succeed, unless something has gone terribly
                   // wrong.

    MemoryManager::release_pages((void*)task->allocated_stack, TASK_PAGES_IN_STACK);

    task->allocated_stack = allocated_stack;

    Scheduler::reset_task(task, image);

    set_context_from_task(*task, context);

    return;
}