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/*
 * Copyright (c) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/** @addtogroup genericproc
 * @{
 */

/**
 * @file
 * @brief   Task management.
 */

#include <main/uinit.h>
#include <proc/thread.h>
#include <proc/task.h>
#include <proc/uarg.h>
#include <mm/as.h>
#include <mm/slab.h>
#include <atomic.h>
#include <synch/spinlock.h>
#include <synch/waitq.h>
#include <arch.h>
#include <panic.h>
#include <adt/avl.h>
#include <adt/btree.h>
#include <adt/list.h>
#include <ipc/ipc.h>
#include <ipc/ipcrsc.h>
#include <security/cap.h>
#include <memstr.h>
#include <print.h>
#include <lib/elf.h>
#include <errno.h>
#include <func.h>
#include <syscall/copy.h>

#ifndef LOADED_PROG_STACK_PAGES_NO
#define LOADED_PROG_STACK_PAGES_NO 1
#endif

/** Spinlock protecting the tasks_tree AVL tree. */
SPINLOCK_INITIALIZE(tasks_lock);

/** AVL tree of active tasks.
 *
 * The task is guaranteed to exist after it was found in the tasks_tree as
 * long as:
 * @li the tasks_lock is held,
 * @li the task's lock is held when task's lock is acquired before releasing
 *     tasks_lock or
 * @li the task's refcount is greater than 0
 *
 */
avltree_t tasks_tree;

static task_id_t task_counter = 0;

/**
 * Points to the binary image used as the program loader. All non-initial
 * tasks are created from this executable image.
 */
void *program_loader = NULL;


/** Initialize tasks
 *
 * Initialize kernel tasks support.
 *
 */
void task_init(void)
{
    TASK = NULL;
    avltree_create(&tasks_tree);
}

/*
 * The idea behind this walker is to remember a single task different from TASK.
 */
static bool task_done_walker(avltree_node_t *node, void *arg)
{
    task_t *t = avltree_get_instance(node, task_t, tasks_tree_node);
    task_t **tp = (task_t **) arg;

    if (t != TASK) { 
        *tp = t;
        return false;   /* stop walking */
    }

    return true;    /* continue the walk */
}

/** Kill all tasks except the current task.
 *
 */
void task_done(void)
{
    task_t *t;
    do { /* Repeat until there are any tasks except TASK */
        
        /* Messing with task structures, avoid deadlock */
        ipl_t ipl = interrupts_disable();
        spinlock_lock(&tasks_lock);
        
        t = NULL;
        avltree_walk(&tasks_tree, task_done_walker, &t);
        
        if (t != NULL) {
            task_id_t id = t->taskid;
            
            spinlock_unlock(&tasks_lock);
            interrupts_restore(ipl);
            
#ifdef CONFIG_DEBUG
            printf("Killing task %" PRIu64 "\n", id);
#endif          
            task_kill(id);
            thread_usleep(10000);
        } else {
            spinlock_unlock(&tasks_lock);
            interrupts_restore(ipl);
        }
        
    } while (t != NULL);
}

/** Create new task
 *
 * Create new task with no threads.
 *
 * @param as Task's address space.
 * @param name Symbolic name.
 *
 * @return New task's structure
 *
 */
task_t *task_create(as_t *as, char *name)
{
    ipl_t ipl;
    task_t *ta;
    int i;
    
    ta = (task_t *) malloc(sizeof(task_t), 0);

    task_create_arch(ta);

    spinlock_initialize(&ta->lock, "task_ta_lock");
    list_initialize(&ta->th_head);
    ta->as = as;
    ta->name = name;
    atomic_set(&ta->refcount, 0);
    atomic_set(&ta->lifecount, 0);
    ta->context = CONTEXT;

    ta->capabilities = 0;
    ta->cycles = 0;
    
    ipc_answerbox_init(&ta->answerbox, ta);
    for (i = 0; i < IPC_MAX_PHONES; i++)
        ipc_phone_init(&ta->phones[i]);
    if ((ipc_phone_0) && (context_check(ipc_phone_0->task->context,
        ta->context)))
        ipc_phone_connect(&ta->phones[0], ipc_phone_0);
    atomic_set(&ta->active_calls, 0);

    mutex_initialize(&ta->futexes_lock);
    btree_create(&ta->futexes);
    
    ipl = interrupts_disable();

    /*
     * Increment address space reference count.
     */
    atomic_inc(&as->refcount);

    spinlock_lock(&tasks_lock);
    ta->taskid = ++task_counter;
    avltree_node_initialize(&ta->tasks_tree_node);
    ta->tasks_tree_node.key = ta->taskid; 
    avltree_insert(&tasks_tree, &ta->tasks_tree_node);
    spinlock_unlock(&tasks_lock);
    interrupts_restore(ipl);

    return ta;
}

/** Destroy task.
 *
 * @param t Task to be destroyed.
 */
void task_destroy(task_t *t)
{
    /*
     * Remove the task from the task B+tree.
     */
    spinlock_lock(&tasks_lock);
    avltree_delete(&tasks_tree, &t->tasks_tree_node);
    spinlock_unlock(&tasks_lock);

    /*
     * Perform architecture specific task destruction.
     */
    task_destroy_arch(t);

    /*
     * Free up dynamically allocated state.
     */
    btree_destroy(&t->futexes);

    /*
     * Drop our reference to the address space.
     */
    if (atomic_predec(&t->as->refcount) == 0) 
        as_destroy(t->as);
    
    free(t);
    TASK = NULL;
}

/** Create new task with 1 thread and run it
 *
 * @param as Address space containing a binary program image.
 * @param entry_addr Program entry-point address in program address space.
 * @param name Program name.
 *
 * @return Task of the running program or NULL on error.
 */
task_t *task_create_from_as(as_t *as, uintptr_t entry_addr, char *name
    thread_t **thr)
{
    as_area_t *a;
    thread_t *t;
    task_t *task;
    uspace_arg_t *kernel_uarg;

    kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
    kernel_uarg->uspace_entry = (void *) entry_addr;
    kernel_uarg->uspace_stack = (void *) USTACK_ADDRESS;
    kernel_uarg->uspace_thread_function = NULL;
    kernel_uarg->uspace_thread_arg = NULL;
    kernel_uarg->uspace_uarg = NULL;
    
    task = task_create(as, name);
    ASSERT(task);

    /*
     * Create the data as_area.
     */
    a = as_area_create(as, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE,
        LOADED_PROG_STACK_PAGES_NO * PAGE_SIZE, USTACK_ADDRESS,
        AS_AREA_ATTR_NONE, &anon_backend, NULL);

    /*
     * Create the main thread.
     */
    t = thread_create(uinit, kernel_uarg, task, THREAD_FLAG_USPACE,
        "uinit", false);
    ASSERT(t);

    *thr = t;
    
    return task;
}

/** Parse an executable image in the physical memory.
 *
 * If the image belongs to a program loader, it is registered as such,
 * (and *task is set to NULL). Otherwise a task is created from the
 * executable image. The task is returned in *task.
 *
 * @param program_addr Address of program executable image.
 * @param name Program name. 
 * @param task Where to store the pointer to the newly created task.
 *
 * @return EOK on success or negative error code.
 */
int task_parse_initial(void *program_addr, char *name, thread_t **t)
{
    as_t *as;
    unsigned int rc;
    task_t *task;

    as = as_create(0);
    ASSERT(as);

    rc = elf_load((elf_header_t *) program_addr, as, 0);
    if (rc != EE_OK) {
        as_destroy(as);
        *task = NULL;
        if (rc != EE_LOADER)
            return ENOTSUP;
        
        /* Register image as the program loader */
        ASSERT(program_loader == NULL);
        program_loader = program_addr;
        return EOK;
    }

    task = task_create_from_as(as, ((elf_header_t *) program_addr)->e_entry,
        name, t);

    return EOK;
}

/** Create a task from the program loader image.
 *
 * @param name Program name. 
 * @param t Buffer for storing pointer to the newly created task.
 *
 * @return Task of the running program or NULL on error.
 */
int task_create_from_loader(char *name, task_t **t)
{
    as_t *as;
    unsigned int rc;
    void *loader;

    as = as_create(0);
    ASSERT(as);

    loader = program_loader;
    if (!loader) return ENOENT;

    rc = elf_load((elf_header_t *) program_loader, as, ELD_F_LOADER);
    if (rc != EE_OK) {
        as_destroy(as);
        return ENOENT;
    }

    *t = task_create_from_as(
        as, ((elf_header_t *) program_loader)->e_entry, name);  

    return EOK;
}

/** Make task ready.
 *
 * Switch task's thread to the ready state.
 *
 * @param ta Task to make ready.
 */
void task_ready(task_t *t)
{
    thread_t *th;

    th = list_get_instance(t->th_head.next, thread_t, th_link);
    thread_ready(th);
}

/** Syscall for reading task ID from userspace.
 *
 * @param uspace_task_id Userspace address of 8-byte buffer where to store
 * current task ID.
 *
 * @return 0 on success or an error code from @ref errno.h.
 */
unative_t sys_task_get_id(task_id_t *uspace_task_id)
{
    /*
     * No need to acquire lock on TASK because taskid
     * remains constant for the lifespan of the task.
     */
    return (unative_t) copy_to_uspace(uspace_task_id, &TASK->taskid,
        sizeof(TASK->taskid));
}

/** Syscall for creating a new task from userspace.
 *
 * Creates a new task from the program loader image, connects a phone
 * to it and stores the phone id into the provided buffer.
 *
 * @param uspace_phone_id Userspace address where to store the phone id.
 *
 * @return 0 on success or an error code from @ref errno.h.
 */
unative_t sys_task_spawn_loader(int *uspace_phone_id)
{
    task_t *t;
    int fake_id;
    int rc;
    int phone_id;

    fake_id = 0;

    /* Before we even try creating the task, see if we can write the id */
    rc = (unative_t) copy_to_uspace(uspace_phone_id, &fake_id,
        sizeof(fake_id));
    if (rc != 0)
        return rc;

    phone_id = phone_alloc();
    if (phone_id < 0)
        return ELIMIT;

    rc = task_create_from_loader("loader", &t);
    if (rc != 0)
        return rc;

    phone_connect(phone_id, &t->answerbox);

    /* No need to aquire lock before task_ready() */
    rc = (unative_t) copy_to_uspace(uspace_phone_id, &phone_id,
        sizeof(phone_id));
    if (rc != 0) {
        /* Ooops */
        ipc_phone_hangup(&TASK->phones[phone_id]);
        task_kill(t->taskid);
        return rc;
    }

    task_ready(t);

    return EOK;
}

unative_t sys_task_spawn(void *image, size_t size)
{
    void *kimage = malloc(size, 0);
    if (kimage == NULL)
        return ENOMEM;
    
    int rc = copy_from_uspace(kimage, image, size);
    if (rc != EOK)
        return rc;
    
    uspace_arg_t *kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
    if (kernel_uarg == NULL) {
        free(kimage);
        return ENOMEM;
    }
    
    kernel_uarg->uspace_entry =
        (void *) ((elf_header_t *) kimage)->e_entry;
    kernel_uarg->uspace_stack = (void *) USTACK_ADDRESS;
    kernel_uarg->uspace_thread_function = NULL;
    kernel_uarg->uspace_thread_arg = NULL;
    kernel_uarg->uspace_uarg = NULL;
    
    as_t *as = as_create(0);
    if (as == NULL) {
        free(kernel_uarg);
        free(kimage);
        return ENOMEM;
    }
    
    unsigned int erc = elf_load((elf_header_t *) kimage, as);
    if (erc != EE_OK) {
        as_destroy(as);
        free(kernel_uarg);
        free(kimage);
        return ENOENT;
    }
    
    as_area_t *area = as_area_create(as,
        AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE,
        LOADED_PROG_STACK_PAGES_NO * PAGE_SIZE, USTACK_ADDRESS,
        AS_AREA_ATTR_NONE, &anon_backend, NULL);
    if (area == NULL) {
        as_destroy(as);
        free(kernel_uarg);
        free(kimage);
        return ENOMEM;
    }
    
    task_t *task = task_create(as, "app");
    if (task == NULL) {
        as_destroy(as);
        free(kernel_uarg);
        free(kimage);
        return ENOENT;
    }
    
    // FIXME: control the capabilities
    cap_set(task, cap_get(TASK));
    
    thread_t *thread = thread_create(uinit, kernel_uarg, task,
        THREAD_FLAG_USPACE, "user", false);
    if (thread == NULL) {
        task_destroy(task);
        as_destroy(as);
        free(kernel_uarg);
        free(kimage);
        return ENOENT;
    }
    
    thread_ready(thread);
    
    return EOK;
}

/** Find task structure corresponding to task ID.
 *
 * The tasks_lock must be already held by the caller of this function
 * and interrupts must be disabled.
 *
 * @param id Task ID.
 *
 * @return Task structure address or NULL if there is no such task ID.
 */
task_t *task_find_by_id(task_id_t id)
{
    avltree_node_t *node;
    
    node = avltree_search(&tasks_tree, (avltree_key_t) id);

    if (node)
        return avltree_get_instance(node, task_t, tasks_tree_node); 
    return NULL;
}

/** Get accounting data of given task.
 *
 * Note that task lock of 't' must be already held and
 * interrupts must be already disabled.
 *
 * @param t Pointer to thread.
 *
 */
uint64_t task_get_accounting(task_t *t)
{
    /* Accumulated value of task */
    uint64_t ret = t->cycles;
    
    /* Current values of threads */
    link_t *cur;
    for (cur = t->th_head.next; cur != &t->th_head; cur = cur->next) {
        thread_t *thr = list_get_instance(cur, thread_t, th_link);
        
        spinlock_lock(&thr->lock);
        /* Process only counted threads */
        if (!thr->uncounted) {
            if (thr == THREAD) {
                /* Update accounting of current thread */
                thread_update_accounting();
            } 
            ret += thr->cycles;
        }
        spinlock_unlock(&thr->lock);
    }
    
    return ret;
}

/** Kill task.
 *
 * This function is idempotent.
 * It signals all the task's threads to bail it out.
 *
 * @param id ID of the task to be killed.
 *
 * @return 0 on success or an error code from errno.h
 */
int task_kill(task_id_t id)
{
    ipl_t ipl;
    task_t *ta;
    link_t *cur;

    if (id == 1)
        return EPERM;
    
    ipl = interrupts_disable();
    spinlock_lock(&tasks_lock);
    if (!(ta = task_find_by_id(id))) {
        spinlock_unlock(&tasks_lock);
        interrupts_restore(ipl);
        return ENOENT;
    }
    spinlock_unlock(&tasks_lock);
    
    /*
     * Interrupt all threads except ktaskclnp.
     */
    spinlock_lock(&ta->lock);
    for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
        thread_t *thr;
        bool sleeping = false;
        
        thr = list_get_instance(cur, thread_t, th_link);
            
        spinlock_lock(&thr->lock);
        thr->interrupted = true;
        if (thr->state == Sleeping)
            sleeping = true;
        spinlock_unlock(&thr->lock);
        
        if (sleeping)
            waitq_interrupt_sleep(thr);
    }
    spinlock_unlock(&ta->lock);
    interrupts_restore(ipl);
    
    return 0;
}

static bool task_print_walker(avltree_node_t *node, void *arg)
{
    task_t *t = avltree_get_instance(node, task_t, tasks_tree_node);
    int j;
        
    spinlock_lock(&t->lock);
            
    uint64_t cycles;
    char suffix;
    order(task_get_accounting(t), &cycles, &suffix);

#ifdef __32_BITS__  
    printf("%-6" PRIu64 " %-10s %-3" PRIu32 " %10p %10p %9" PRIu64 "%c %7ld %6ld",
        t->taskid, t->name, t->context, t, t->as, cycles, suffix,
        atomic_get(&t->refcount), atomic_get(&t->active_calls));
#endif

#ifdef __64_BITS__
    printf("%-6" PRIu64 " %-10s %-3" PRIu32 " %18p %18p %9" PRIu64 "%c %7ld %6ld",
        t->taskid, t->name, t->context, t, t->as, cycles, suffix,
        atomic_get(&t->refcount), atomic_get(&t->active_calls));
#endif

    for (j = 0; j < IPC_MAX_PHONES; j++) {
        if (t->phones[j].callee)
            printf(" %d:%p", j, t->phones[j].callee);
    }
    printf("\n");
            
    spinlock_unlock(&t->lock);
    return true;
}

/** Print task list */
void task_print_list(void)
{
    ipl_t ipl;
    
    /* Messing with task structures, avoid deadlock */
    ipl = interrupts_disable();
    spinlock_lock(&tasks_lock);

#ifdef __32_BITS__  
    printf("taskid name       ctx address    as         "
        "cycles     threads calls  callee\n");
    printf("------ ---------- --- ---------- ---------- "
        "---------- ------- ------ ------>\n");
#endif

#ifdef __64_BITS__
    printf("taskid name       ctx address            as                 "
        "cycles     threads calls  callee\n");
    printf("------ ---------- --- ------------------ ------------------ "
        "---------- ------- ------ ------>\n");
#endif

    avltree_walk(&tasks_tree, task_print_walker, NULL);

    spinlock_unlock(&tasks_lock);
    interrupts_restore(ipl);
}

/** @}
 */