/*
 * Copyright (c) 2009-2010, Salvatore Sanfilippo <antirez at gmail dot com>
 * Copyright (c) 2010, Pieter Noordhuis <pcnoordhuis at gmail dot com>
 *
 * 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.
 *   * Neither the name of Redis 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 <string.h>
#include <assert.h>
#include "async.h"
#include "sds.h"
#include "util.h"

/* Forward declaration of function in hiredis.c */
void __redisAppendCommand(redisContext *c, char *cmd, size_t len);

static redisAsyncContext *redisAsyncInitialize(redisContext *c) {
    redisAsyncContext *ac = realloc(c,sizeof(redisAsyncContext));
    c = &(ac->c);

    /* The regular connect functions will always set the flag REDIS_CONNECTED.
     * For the async API, we want to wait until the first write event is
     * received up before setting this flag, so reset it here. */
    c->flags &= ~REDIS_CONNECTED;

    ac->err = 0;
    ac->errstr = NULL;
    ac->data = NULL;

    ac->ev.data = NULL;
    ac->ev.addRead = NULL;
    ac->ev.delRead = NULL;
    ac->ev.addWrite = NULL;
    ac->ev.delWrite = NULL;
    ac->ev.cleanup = NULL;

    ac->onConnect = NULL;
    ac->onDisconnect = NULL;

    ac->replies.head = NULL;
    ac->replies.tail = NULL;
    return ac;
}

/* We want the error field to be accessible directly instead of requiring
 * an indirection to the redisContext struct. */
static void __redisAsyncCopyError(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    ac->err = c->err;
    ac->errstr = c->errstr;
}

redisAsyncContext *redisAsyncConnect(const char *ip, int port) {
    redisContext *c = redisConnectNonBlock(ip,port);
    redisAsyncContext *ac = redisAsyncInitialize(c);
    __redisAsyncCopyError(ac);
    return ac;
}

redisAsyncContext *redisAsyncConnectUnix(const char *path) {
    redisContext *c = redisConnectUnixNonBlock(path);
    redisAsyncContext *ac = redisAsyncInitialize(c);
    __redisAsyncCopyError(ac);
    return ac;
}

int redisAsyncSetReplyObjectFunctions(redisAsyncContext *ac, redisReplyObjectFunctions *fn) {
    redisContext *c = &(ac->c);
    return redisSetReplyObjectFunctions(c,fn);
}

int redisAsyncSetConnectCallback(redisAsyncContext *ac, redisConnectCallback *fn) {
    if (ac->onConnect == NULL) {
        ac->onConnect = fn;

        /* The common way to detect an established connection is to wait for
         * the first write event to be fired. This assumes the related event
         * library functions are already set. */
        if (ac->ev.addWrite) ac->ev.addWrite(ac->ev.data);
        return REDIS_OK;
    }
    return REDIS_ERR;
}

int redisAsyncSetDisconnectCallback(redisAsyncContext *ac, redisDisconnectCallback *fn) {
    if (ac->onDisconnect == NULL) {
        ac->onDisconnect = fn;
        return REDIS_OK;
    }
    return REDIS_ERR;
}

/* Helper functions to push/shift callbacks */
static int __redisPushCallback(redisCallbackList *list, redisCallback *source) {
    redisCallback *cb;

    /* Copy callback from stack to heap */
    cb = malloc(sizeof(*cb));
    if (!cb) redisOOM();
    if (source != NULL) {
        memcpy(cb,source,sizeof(*cb));
        cb->next = NULL;
    }

    /* Store callback in list */
    if (list->head == NULL)
        list->head = cb;
    if (list->tail != NULL)
        list->tail->next = cb;
    list->tail = cb;
    return REDIS_OK;
}

static int __redisShiftCallback(redisCallbackList *list, redisCallback *target) {
    redisCallback *cb = list->head;
    if (cb != NULL) {
        list->head = cb->next;
        if (cb == list->tail)
            list->tail = NULL;

        /* Copy callback from heap to stack */
        if (target != NULL)
            memcpy(target,cb,sizeof(*cb));
        free(cb);
        return REDIS_OK;
    }
    return REDIS_ERR;
}

/* Helper function to free the context. */
static void __redisAsyncFree(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    redisCallback cb;

    /* Execute pending callbacks with NULL reply. */
    while (__redisShiftCallback(&ac->replies,&cb) == REDIS_OK) {
        if (cb.fn != NULL) {
            c->flags |= REDIS_IN_CALLBACK;
            cb.fn(ac,NULL,cb.privdata);
            c->flags &= ~REDIS_IN_CALLBACK;
        }
    }

    /* Signal event lib to clean up */
    if (ac->ev.cleanup) ac->ev.cleanup(ac->ev.data);

    /* Execute disconnect callback. When redisAsyncFree() initiated destroying
     * this context, the status will always be REDIS_OK. */
    if (ac->onDisconnect && (c->flags & REDIS_CONNECTED)) {
        if (c->flags & REDIS_FREEING) {
            ac->onDisconnect(ac,REDIS_OK);
        } else {
            ac->onDisconnect(ac,(ac->err == 0) ? REDIS_OK : REDIS_ERR);
        }
    }

    /* Cleanup self */
    redisFree(c);
}

/* Free the async context. When this function is called from a callback,
 * control needs to be returned to redisProcessCallbacks() before actual
 * free'ing. To do so, a flag is set on the context which is picked up by
 * redisProcessCallbacks(). Otherwise, the context is immediately free'd. */
void redisAsyncFree(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    c->flags |= REDIS_FREEING;
    if (!(c->flags & REDIS_IN_CALLBACK))
        __redisAsyncFree(ac);
}

/* Helper function to make the disconnect happen and clean up. */
static void __redisAsyncDisconnect(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);

    /* Make sure error is accessible if there is any */
    __redisAsyncCopyError(ac);

    if (ac->err == 0) {
        /* For clean disconnects, there should be no pending callbacks. */
        assert(__redisShiftCallback(&ac->replies,NULL) == REDIS_ERR);
    } else {
        /* Disconnection is caused by an error, make sure that pending
         * callbacks cannot call new commands. */
        c->flags |= REDIS_DISCONNECTING;
    }

    /* For non-clean disconnects, __redisAsyncFree() will execute pending
     * callbacks with a NULL-reply. */
    __redisAsyncFree(ac);
}

/* Tries to do a clean disconnect from Redis, meaning it stops new commands
 * from being issued, but tries to flush the output buffer and execute
 * callbacks for all remaining replies. When this function is called from a
 * callback, there might be more replies and we can safely defer disconnecting
 * to redisProcessCallbacks(). Otherwise, we can only disconnect immediately
 * when there are no pending callbacks. */
void redisAsyncDisconnect(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    c->flags |= REDIS_DISCONNECTING;
    if (!(c->flags & REDIS_IN_CALLBACK) && ac->replies.head == NULL)
        __redisAsyncDisconnect(ac);
}

void redisProcessCallbacks(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    redisCallback cb;
    void *reply = NULL;
    int status;

    while((status = redisGetReply(c,&reply)) == REDIS_OK) {
        if (reply == NULL) {
            /* When the connection is being disconnected and there are
             * no more replies, this is the cue to really disconnect. */
            if (c->flags & REDIS_DISCONNECTING && sdslen(c->obuf) == 0) {
                __redisAsyncDisconnect(ac);
                return;
            }

            /* When the connection is not being disconnected, simply stop
             * trying to get replies and wait for the next loop tick. */
            break;
        }

        /* Even if the context is subscribed, pending regular callbacks will
         * get a reply before pub/sub messages arrive. */
        if (__redisShiftCallback(&ac->replies,&cb) != REDIS_OK) {
            /* No more regular callbacks, the context *must* be subscribed. */
            assert(c->flags & REDIS_SUBSCRIBED);

            /* TODO: find the right callback for pub/sub message. */
        }

        if (cb.fn != NULL) {
            c->flags |= REDIS_IN_CALLBACK;
            cb.fn(ac,reply,cb.privdata);
            c->flags &= ~REDIS_IN_CALLBACK;
            c->fn->freeObject(reply);

            /* Proceed with free'ing when redisAsyncFree() was called. */
            if (c->flags & REDIS_FREEING) {
                __redisAsyncFree(ac);
                return;
            }
        } else {
            /* No callback for this reply. This can either be a NULL callback,
             * or there were no callbacks to begin with. Either way, don't
             * abort with an error, but simply ignore it because the client
             * doesn't know what the server will spit out over the wire. */
            c->fn->freeObject(reply);
        }
    }

    /* Disconnect when there was an error reading the reply */
    if (status != REDIS_OK)
        __redisAsyncDisconnect(ac);
}

/* This function should be called when the socket is readable.
 * It processes all replies that can be read and executes their callbacks.
 */
void redisAsyncHandleRead(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);

    if (redisBufferRead(c) == REDIS_ERR) {
        __redisAsyncDisconnect(ac);
    } else {
        /* Always re-schedule reads */
        if (ac->ev.addRead) ac->ev.addRead(ac->ev.data);
        redisProcessCallbacks(ac);
    }
}

void redisAsyncHandleWrite(redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    int done = 0;

    if (redisBufferWrite(c,&done) == REDIS_ERR) {
        __redisAsyncDisconnect(ac);
    } else {
        /* Continue writing when not done, stop writing otherwise */
        if (!done) {
            if (ac->ev.addWrite) ac->ev.addWrite(ac->ev.data);
        } else {
            if (ac->ev.delWrite) ac->ev.delWrite(ac->ev.data);
        }

        /* Always schedule reads after writes */
        if (ac->ev.addRead) ac->ev.addRead(ac->ev.data);

        /* Fire onConnect when this is the first write event. */
        if (!(c->flags & REDIS_CONNECTED)) {
            c->flags |= REDIS_CONNECTED;
            if (ac->onConnect) ac->onConnect(ac);
        }
    }
}

/* Helper function for the redisAsyncCommand* family of functions.
 *
 * Write a formatted command to the output buffer and register the provided
 * callback function with the context.
 */
static int __redisAsyncCommand(redisAsyncContext *ac, redisCallbackFn *fn, void *privdata, char *cmd, size_t len) {
    redisContext *c = &(ac->c);
    redisCallback cb;

    /* Don't accept new commands when the connection is about to be closed. */
    if (c->flags & (REDIS_DISCONNECTING | REDIS_FREEING)) return REDIS_ERR;
    __redisAppendCommand(c,cmd,len);

    /* Store callback */
    cb.fn = fn;
    cb.privdata = privdata;
    __redisPushCallback(&ac->replies,&cb);

    /* Always schedule a write when the write buffer is non-empty */
    if (ac->ev.addWrite) ac->ev.addWrite(ac->ev.data);

    return REDIS_OK;
}

int redisvAsyncCommand(redisAsyncContext *ac, redisCallbackFn *fn, void *privdata, const char *format, va_list ap) {
    char *cmd;
    int len;
    int status;
    len = redisvFormatCommand(&cmd,format,ap);
    status = __redisAsyncCommand(ac,fn,privdata,cmd,len);
    free(cmd);
    return status;
}

int redisAsyncCommand(redisAsyncContext *ac, redisCallbackFn *fn, void *privdata, const char *format, ...) {
    va_list ap;
    int status;
    va_start(ap,format);
    status = redisvAsyncCommand(ac,fn,privdata,format,ap);
    va_end(ap);
    return status;
}

int redisAsyncCommandArgv(redisAsyncContext *ac, redisCallbackFn *fn, void *privdata, int argc, const char **argv, const size_t *argvlen) {
    char *cmd;
    int len;
    int status;
    len = redisFormatCommandArgv(&cmd,argc,argv,argvlen);
    status = __redisAsyncCommand(ac,fn,privdata,cmd,len);
    free(cmd);
    return status;
}