/* See COPYRIGHT for copyright information. */

#include <inc/x86.h>
#include <inc/error.h>
#include <inc/string.h>
#include <inc/assert.h>

#include <kern/env.h>
#include <kern/pmap.h>
#include <kern/trap.h>
#include <kern/syscall.h>
#include <kern/console.h>
#include <kern/sched.h>

// Print a string to the system console.
// The string is exactly 'len' characters long.
// Destroys the environment on memory errors.
static void
sys_cputs(const char *s, size_t len)
{
    // Check that the user has permission to read memory [s, s+len).
    // Destroy the environment if not.

    // LAB 3: Your code here.
    user_mem_assert(curenv,(void *)s,len, PTE_U); // kontrola pamate, ci moze user citat z pamate s, s+len
    // Print the string supplied by the user.
    cprintf("%.*s", len, s);
}

// Read a character from the system console without blocking.
// Returns the character, or 0 if there is no input waiting.
static int
sys_cgetc(void)
{
    return cons_getc();
}

// Returns the current environment's envid.
static envid_t
sys_getenvid(void)
{
    return curenv->env_id;
}

// Destroy a given environment (possibly the currently running environment).
//
// Returns 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist,
//      or the caller doesn't have permission to change envid.
static int
sys_env_destroy(envid_t envid)
{
    int r;
    struct Env *e;

    if ((r = envid2env(envid, &e, 1)) < 0)
        return r;
    if (e == curenv)
        cprintf("[%08x] exiting gracefully\n", curenv->env_id);
    else
        cprintf("[%08x] destroying %08x\n", curenv->env_id, e->env_id);
    env_destroy(e);
    return 0;
}

// Deschedule current environment and pick a different one to run.
static void
sys_yield(void)
{
    sched_yield();
}

// Allocate a new environment.
// Returns envid of new environment, or < 0 on error.  Errors are:
//  -E_NO_FREE_ENV if no free environment is available.
//  -E_NO_MEM on memory exhaustion.
static envid_t
sys_exofork(void)
{
    // Create the new environment with env_alloc(), from kern/env.c.
    // It should be left as env_alloc created it, except that
    // status is set to ENV_NOT_RUNNABLE, and the register set is copied
    // from the current environment -- but tweaked so sys_exofork
    // will appear to return 0.

    // LAB 4: Your code here.
    struct Env *e;
    if(env_alloc(&e, curenv->env_id) < 0){
        return -E_NO_FREE_ENV;
    }

    e->env_status = ENV_NOT_RUNNABLE;
    e->env_tf = curenv->env_tf;
    e->env_tf.tf_regs.reg_eax = 0;

    return e->env_id;
    //panic("sys_exofork not implemented");
}

// Set envid's env_status to status, which must be ENV_RUNNABLE
// or ENV_NOT_RUNNABLE.
//
// Returns 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist,
//      or the caller doesn't have permission to change envid.
//  -E_INVAL if status is not a valid status for an environment.
static int
sys_env_set_status(envid_t envid, int status)
{
    // Hint: Use the 'envid2env' function from kern/env.c to translate an
    // envid to a struct Env.
    // You should set envid2env's third argument to 1, which will
    // check whether the current environment has permission to set
    // envid's status.

    // LAB 4: Your code here.
    struct Env *e;

    if(envid2env(envid, &e, 1) < 0){            //if environment envid doesn't currently exist or the caller doesn't have permission to change envid.
        return -E_BAD_ENV;
    }

    if(status != ENV_RUNNABLE && status != ENV_NOT_RUNNABLE){       //if status is not a valid status for an environment
        return -E_INVAL;
    }

    e->env_status = status;
    return 0;
    //panic("sys_env_set_status not implemented");
}

// Set the page fault upcall for 'envid' by modifying the corresponding struct
// Env's 'env_pgfault_upcall' field.  When 'envid' causes a page fault, the
// kernel will push a fault record onto the exception stack, then branch to
// 'func'.
//
// Returns 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist,
//      or the caller doesn't have permission to change envid.
static int
sys_env_set_pgfault_upcall(envid_t envid, void *func)
{
    // LAB 4: Your code here.
    //int ret;
    struct Env * env;

  //
    if (envid2env(envid, &env, 1) )
        return -E_BAD_ENV;
    env->env_pgfault_upcall = func;
    return 0;
    //panic("sys_env_set_pgfault_upcall not implemented");
}

// Allocate a page of memory and map it at 'va' with permission
// 'perm' in the address space of 'envid'.
// The page's contents are set to 0.
// If a page is already mapped at 'va', that page is unmapped as a
// side effect.
//
// perm -- PTE_U | PTE_P must be set, PTE_AVAIL | PTE_W may or may not be set,
//         but no other bits may be set.  See PTE_SYSCALL in inc/mmu.h.
//
// Return 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist,
//      or the caller doesn't have permission to change envid.Fs
//  -E_INVAL if va >= UTOP, or va is not page-aligned.
//  -E_INVAL if perm is inappropriate (see above).
//  -E_NO_MEM if there's no memory to allocate the new page,
//      or to allocate any necessary page tables.
static int
sys_page_alloc(envid_t envid, void *va, int perm)
{
    // Hint: This function is a wrapper around page_alloc() and
    //   page_insert() from kern/pmap.c.
    //   Most of the new code you write should be to check the
    //   parameters for correctness.
    //   If page_insert() fails, remember to free the page you
    //   allocated!

    // LAB 4: Your code here.
    struct Env *e;

    int ret = envid2env(envid, &e, 1);

    if (ret) return ret;
    if (va >= (void*)UTOP) return -E_INVAL;

    if((perm & PTE_U & PTE_P) && ((perm | PTE_SYSCALL) != PTE_SYSCALL) )
        return(-E_INVAL);

    struct PageInfo *pg = page_alloc(1);
    if (!pg)
        return -E_NO_MEM;

    //pg->pp_ref++;
    ret = page_insert(e->env_pgdir, pg, va, perm);

    if (ret)
    {
        page_free(pg);
        return ret;
    }
    return 0;
    //panic("sys_page_alloc not implemented");
}

// Map the page of memory at 'srcva' in srcenvid's address space
// at 'dstva' in envid's address space with permission 'perm'.
// Perm has the same restrictions as in sys_page_alloc, except
// that it also must not grant write access to a read-only
// page.
//
// Return 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if srcenvid and/or envid doesn't currently exist,
//      or the caller doesn't have permission to change one of them.
//  -E_INVAL if srcva >= UTOP or srcva is not page-aligned,
//      or dstva >= UTOP or dstva is not page-aligned.
//  -E_INVAL is srcva is not mapped in srcenvid's address space.
//  -E_INVAL if perm is inappropriate (see sys_page_alloc).
//  -E_INVAL if (perm & PTE_W), but srcva is read-only in srcenvid's
//      address space.
//  -E_NO_MEM if there's no memory to allocate any necessary page tables.
static int
sys_page_map(envid_t srcenvid, void *srcva,
         envid_t envid, void *dstva, int perm)
{

    // Hint: This function is a wrapper around page_lookup() and
    //   page_insert() from kern/pmap.c.
    //   Again, most of the new code you write should be to check the
    //   parameters for correctness.
    //   Use the third argument to page_lookup() to
    //   check the current permissions on the page.

    // LAB 4: Your code here.

    struct Env *src;
    struct Env *dest;
    if(envid2env(srcenvid,&src,true) || envid2env(envid,&dest,true))
        return(-E_BAD_ENV);
    if(((uintptr_t)srcva >= UTOP) || PGOFF(srcva) || (((uintptr_t)dstva >= UTOP)) || PGOFF(dstva))
        return (-E_INVAL);
    pte_t *pp;
    struct PageInfo *p=page_lookup(src->env_pgdir,srcva,&pp);
    if(p == NULL)
        return(-E_INVAL);

    if((perm & PTE_U & PTE_P) && ((perm | PTE_SYSCALL) != PTE_SYSCALL) )
        return(-E_INVAL);

    if((!(*pp & PTE_W)) && (perm & PTE_W))
        return (-E_INVAL);

    if(page_insert(dest->env_pgdir,p,dstva,perm))
        return(-E_NO_MEM);
    return 0;

    //panic("sys_page_map not implemented");
}

// Unmap the page of memory at 'va' in the address space of 'envid'.
// If no page is mapped, the function silently succeeds.
//
// Return 0 on success, < 0 on error.  Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist,
//      or the caller doesn't have permission to change envid.
//  -E_INVAL if va >= UTOP, or va is not page-aligned.
static int
sys_page_unmap(envid_t envid, void *va)
{
    // Hint: This function is a wrapper around page_remove().

    // LAB 4: Your code here.
    if (va>=(void*)UTOP || ROUNDDOWN(va,PGSIZE)!=va) //ak virtualna adresa je väcsia alebo rovna od UTOP alebo nie je zarovnana stranka tak vrati error
        return -E_INVAL;
    struct Env *e;
    if ((int)envid2env(envid, &e, 1))
        return -E_BAD_ENV;  //ak enviroment neexistuje alebo nemá oprávnenie tak vráti error
    page_remove(e->env_pgdir, va);  //vymaže stránku
    return 0;
    //panic("sys_page_unmap not implemented");
}

// Try to send 'value' to the target env 'envid'.
// If srcva < UTOP, then also send page currently mapped at 'srcva',
// so that receiver gets a duplicate mapping of the same page.
//
// The send fails with a return value of -E_IPC_NOT_RECV if the
// target is not blocked, waiting for an IPC.
//
// The send also can fail for the other reasons listed below.
//
// Otherwise, the send succeeds, and the target's ipc fields are
// updated as follows:
//    env_ipc_recving is set to 0 to block future sends;
//    env_ipc_from is set to the sending envid;
//    env_ipc_value is set to the 'value' parameter;
//    env_ipc_perm is set to 'perm' if a page was transferred, 0 otherwise.
// The target environment is marked runnable again, returning 0
// from the paused sys_ipc_recv system call.  (Hint: does the
// sys_ipc_recv function ever actually return?)
//
// If the sender wants to send a page but the receiver isn't asking for one,
// then no page mapping is transferred, but no error occurs.
// The ipc only happens when no errors occur.
//
// Returns 0 on success, < 0 on error.
// Errors are:
//  -E_BAD_ENV if environment envid doesn't currently exist.
//      (No need to check permissions.)
//  -E_IPC_NOT_RECV if envid is not currently blocked in sys_ipc_recv,
//      or another environment managed to send first.
//  -E_INVAL if srcva < UTOP but srcva is not page-aligned.
//  -E_INVAL if srcva < UTOP and perm is inappropriate
//      (see sys_page_alloc).
//  -E_INVAL if srcva < UTOP but srcva is not mapped in the caller's
//      address space.
//  -E_INVAL if (perm & PTE_W), but srcva is read-only in the
//      current environment's address space.
//  -E_NO_MEM if there's not enough memory to map srcva in envid's
//      address space.
static int
sys_ipc_try_send(envid_t envid, uint32_t value, void *srcva, unsigned perm)
{
    // LAB 4: Your code here.
    struct Env *env;
    if (envid2env (envid, &env, 0) < 0) {
        return -E_BAD_ENV; //error 1
    }

    if (!env->env_ipc_recving) {
        return -E_IPC_NOT_RECV; //error 2
    }

    if (srcva < (void *)UTOP)
    {

        pte_t* pte;
        struct PageInfo* page = page_lookup(curenv->env_pgdir, srcva, &pte);

        if(!page) {
            return -E_INVAL;
        }

        if((perm & PTE_W) && !(*pte & PTE_W)) {
            return -E_INVAL;
        }

        if(env->env_ipc_dstva < (void *) UTOP) {

            if(page_insert(env->env_pgdir, page, env->env_ipc_dstva, perm)) {
                return -E_NO_MEM;
            }
        }
        env->env_ipc_perm = perm;
    }
    else
    {
        env->env_ipc_perm = 0;
    }


    env->env_ipc_recving = 0;
    env->env_ipc_from = curenv->env_id;
    env->env_ipc_value = value;
    env->env_status = ENV_RUNNABLE;
    env->env_tf.tf_regs.reg_eax = 0;

    return 0;
}

// Block until a value is ready.  Record that you want to receive
// using the env_ipc_recving and env_ipc_dstva fields of struct Env,
// mark yourself not runnable, and then give up the CPU.
//
// If 'dstva' is < UTOP, then you are willing to receive a page of data.
// 'dstva' is the virtual address at which the sent page should be mapped.
//
// This function only returns on error, but the system call will eventually
// return 0 on success.
// Return < 0 on error.  Errors are:
//  -E_INVAL if dstva < UTOP but dstva is not page-aligned.
static int
sys_ipc_recv(void *dstva)
{
    // LAB 4: Your code here.
    if(((size_t)dstva < UTOP) && ((size_t)dstva % PGSIZE != 0))
        return -E_INVAL;

    curenv->env_ipc_recving = true; // in struct Env - inc/env.h
    curenv->env_ipc_dstva = dstva;
    curenv->env_status = ENV_NOT_RUNNABLE;
    sched_yield();

    return 0;
}

// Dispatches to the correct kernel function, passing the arguments.
int32_t
syscall(uint32_t syscallno, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)
{
    // Call the function corresponding to the 'syscallno' parameter.
    // Return any appropriate return value.
    // LAB 3: Your code here.

    switch (syscallno) { //presmerovanie systemoveho volania na handler
        case SYS_cputs:
            sys_cputs((char *)a1,(size_t)a2);
            return 0;
        case SYS_cgetc:
            return(sys_cgetc());
        case SYS_env_destroy:
            return(sys_env_destroy((envid_t)a1));
        case SYS_getenvid:
            return(sys_getenvid());
        case SYS_yield:
            sys_yield();
            return(0);
        case SYS_exofork:
            return sys_exofork();
        case SYS_page_alloc:
            return sys_page_alloc(a1, (void*)a2, a3);
        case SYS_page_map:
            return sys_page_map(a1, (void*)a2, a3, (void*)a4, a5);
        case SYS_page_unmap:
            return sys_page_unmap(a1, (void*)a2);
        case SYS_env_set_status:
            return sys_env_set_status(a1, a2);
        case SYS_env_set_pgfault_upcall:
            return sys_env_set_pgfault_upcall(a1, (void*)a2);
        case SYS_ipc_recv:
            return sys_ipc_recv((void*)a1);
        case SYS_ipc_try_send:
            return sys_ipc_try_send(a1, a2, (void*)a3, a4);
    default:
        return -E_INVAL;
    }
}