/**
 * @file call.c
 * @author Ambroz Bizjak <ambrop7@gmail.com>
 * 
 * @section LICENSE
 * 
 * This file is part of BadVPN.
 * 
 * BadVPN is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 * 
 * BadVPN is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 * 
 * @section DESCRIPTION
 * 
 * Synopsis:
 *   callrefhere()
 * 
 * Description:
 *   Exposes variables and objects to call() statements as seen from this
 *   callrefhere() statement.
 * 
 * Synopsis:
 *   call(string template_name, list args)
 *   callhefhere::call(string template_name, list args)
 * 
 * Description:
 *   Module which allows using a single statement to represent multiple statements
 *   in a process template, allowing reuse of repetitive code.
 *   The created template process can access variables and objects as seen from the
 *   call statement via "_caller.variable".
 *   The second form also exposes variables and objects from the corresponding
 *   callrefhere() statement via "_ref.variable".
 * 
 * Variables:
 *   Exposes variables as seen from the end of the called process template.
 * 
 * Behavior in detail:
 *   - On initialization, creates a new process from the template named
 *     template_name, with arguments args.
 *   - When all the statements in the created process go UP, transitions UP.
 *   - When one of the statements is no longer UP, transitions DOWN. The
 *     created process remais paused until the call statement receives the
 *     clean signal, to wait for following statements to deinitialize.
 *   - On deinitialization, initiates termination of the created process and waits
 *     for all its statements to deinitialize.
 */

#include <stdlib.h>

#include <misc/string_begins_with.h>
#include <misc/offset.h>
#include <structure/LinkedList0.h>
#include <ncd/NCDModule.h>

#include <generated/blog_channel_ncd_call.h>

#define ModuleLog(i, ...) NCDModuleInst_Backend_Log((i), BLOG_CURRENT_CHANNEL, __VA_ARGS__)

#define STATE_WORKING 1
#define STATE_UP 2
#define STATE_WAITING 3
#define STATE_TERMINATING 4

struct callrefhere_instance {
    NCDModuleInst *i;
    LinkedList0 calls_list;
};

struct instance {
    NCDModuleInst *i;
    NCDModuleProcess process;
    int state;
    struct callrefhere_instance *crh;
    LinkedList0Node calls_list_node;
};

static void instance_free (struct instance *o);

static void process_handler_event (struct instance *o, int event)
{
    switch (event) {
        case NCDMODULEPROCESS_EVENT_UP: {
            ASSERT(o->state == STATE_WORKING)
            
            // signal up
            NCDModuleInst_Backend_Up(o->i);
            
            // set state up
            o->state = STATE_UP;
        } break;
        
        case NCDMODULEPROCESS_EVENT_DOWN: {
            ASSERT(o->state == STATE_UP)
            
            // signal down
            NCDModuleInst_Backend_Down(o->i);
            
            // set state waiting
            o->state = STATE_WAITING;
        } break;
        
        case NCDMODULEPROCESS_EVENT_TERMINATED: {
            ASSERT(o->state == STATE_TERMINATING)
            
            // die finally
            instance_free(o);
            return;
        } break;
        
        default: ASSERT(0);
    }
}

static int process_func_getspecialvar (struct instance *o, const char *name, NCDValue *out)
{
    size_t p;
    
    if (p = string_begins_with(name, "_caller.")) {
        return NCDModuleInst_Backend_GetVar(o->i, name + p, out);
    }
    
    if (o->crh && (p = string_begins_with(name, "_ref."))) {
        return NCDModuleInst_Backend_GetVar(o->crh->i, name + p, out);
    }
    
    return 0;
}

static NCDModuleInst * process_func_getspecialobj (struct instance *o, const char *name)
{
    size_t p;
    
    if (p = string_begins_with(name, "_caller.")) {
        return NCDModuleInst_Backend_GetObj(o->i, name + p);
    }
    
    if (o->crh && (p = string_begins_with(name, "_ref."))) {
        return NCDModuleInst_Backend_GetObj(o->crh->i, name + p);
    }
    
    return NULL;
}

static void callrefhere_func_new (NCDModuleInst *i)
{
    // allocate instance
    struct callrefhere_instance *o = malloc(sizeof(*o));
    if (!o) {
        ModuleLog(i, BLOG_ERROR, "failed to allocate instance");
        goto fail0;
    }
    NCDModuleInst_Backend_SetUser(i, o);
    
    // set arguments
    o->i = i;
    
    // init calls list
    LinkedList0_Init(&o->calls_list);
    
    // signal up
    NCDModuleInst_Backend_Up(o->i);
    return;
    
fail0:
    NCDModuleInst_Backend_SetError(i);
    NCDModuleInst_Backend_Dead(i);
}

static void callrefhere_func_die (void *vo)
{
    struct callrefhere_instance *o = vo;
    NCDModuleInst *i = o->i;
    
    // disconnect calls
    while (!LinkedList0_IsEmpty(&o->calls_list)) {
        struct instance *inst = UPPER_OBJECT(LinkedList0_GetFirst(&o->calls_list), struct instance, calls_list_node);
        ASSERT(inst->crh == o)
        LinkedList0_Remove(&o->calls_list, &inst->calls_list_node);
        inst->crh = NULL;
    }
    
    // free instance
    free(o);
    
    NCDModuleInst_Backend_Dead(i);
}

static void func_new (NCDModuleInst *i)
{
    // allocate instance
    struct instance *o = malloc(sizeof(*o));
    if (!o) {
        ModuleLog(i, BLOG_ERROR, "failed to allocate instance");
        goto fail0;
    }
    NCDModuleInst_Backend_SetUser(i, o);
    
    // init arguments
    o->i = i;
    
    // check arguments
    NCDValue *template_name_arg;
    NCDValue *args_arg;
    if (!NCDValue_ListRead(o->i->args, 2, &template_name_arg, &args_arg)) {
        ModuleLog(o->i, BLOG_ERROR, "wrong arity");
        goto fail1;
    }
    if (NCDValue_Type(template_name_arg) != NCDVALUE_STRING || NCDValue_Type(args_arg) != NCDVALUE_LIST) {
        ModuleLog(o->i, BLOG_ERROR, "wrong type");
        goto fail1;
    }
    
    // copy arguments
    NCDValue args;
    if (!NCDValue_InitCopy(&args, args_arg)) {
        ModuleLog(o->i, BLOG_ERROR, "NCDValue_InitCopy failed");
        goto fail1;
    }
    
    // create process
    if (!NCDModuleProcess_Init(&o->process, o->i, NCDValue_StringValue(template_name_arg), args, o, (NCDModuleProcess_handler_event)process_handler_event)) {
        ModuleLog(o->i, BLOG_ERROR, "NCDModuleProcess_Init failed");
        NCDValue_Free(&args);
        goto fail1;
    }
    
    // set special functions
    NCDModuleProcess_SetSpecialFuncs(&o->process,
                                     (NCDModuleProcess_func_getspecialvar)process_func_getspecialvar,
                                     (NCDModuleProcess_func_getspecialobj)process_func_getspecialobj);
    
    // set callrefhere
    o->crh = (o->i->method_object ? o->i->method_object->inst_user : NULL);
    
    // add to callrefhere's calls list
    if (o->crh) {
        LinkedList0_Prepend(&o->crh->calls_list, &o->calls_list_node);
    }
    
    // set state working
    o->state = STATE_WORKING;
    return;
    
fail1:
    free(o);
fail0:
    NCDModuleInst_Backend_SetError(i);
    NCDModuleInst_Backend_Dead(i);
}

void instance_free (struct instance *o)
{
    NCDModuleInst *i = o->i;
    
    // remove from callrefhere's calls list
    if (o->crh) {
        LinkedList0_Remove(&o->crh->calls_list, &o->calls_list_node);
    }
    
    // free process
    NCDModuleProcess_Free(&o->process);
    
    // free instance
    free(o);
    
    NCDModuleInst_Backend_Dead(i);
}

static void func_die (void *vo)
{
    struct instance *o = vo;
    ASSERT(o->state != STATE_TERMINATING)
    
    // request process to terminate
    NCDModuleProcess_Terminate(&o->process);
    
    // set state terminating
    o->state = STATE_TERMINATING;
}

static void func_clean (void *vo)
{
    struct instance *o = vo;
    if (o->state != STATE_WAITING) {
        return;
    }
    
    // allow process to continue
    NCDModuleProcess_Continue(&o->process);
    
    // set state working
    o->state = STATE_WORKING;
}

static int func_getvar (void *vo, const char *name, NCDValue *out)
{
    struct instance *o = vo;
    ASSERT(o->state == STATE_UP)
    
    return NCDModuleProcess_GetVar(&o->process, name, out);
}

static NCDModuleInst * func_getobj (void *vo, const char *name)
{
    struct instance *o = vo;
    ASSERT(o->state == STATE_UP)
    
    return NCDModuleProcess_GetObj(&o->process, name);
}

static const struct NCDModule modules[] = {
    {
        .type = "callrefhere",
        .func_new = callrefhere_func_new,
        .func_die = callrefhere_func_die
    }, {
        .type = "call",
        .func_new = func_new,
        .func_die = func_die,
        .func_clean = func_clean,
        .func_getvar = func_getvar,
        .func_getobj = func_getobj
    }, {
        .type = "callrefhere::call",
        .func_new = func_new,
        .func_die = func_die,
        .func_clean = func_clean,
        .func_getvar = func_getvar,
        .func_getobj = func_getobj
    }, {
        .type = NULL
    }
};

const struct NCDModuleGroup ncdmodule_call = {
    .modules = modules
};