/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is nsMemoryCacheDevice.cpp, released February 22, 2001.
 * 
 * The Initial Developer of the Original Code is Netscape Communications
 * Corporation.  Portions created by Netscape are
 * Copyright (C) 2001 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s): 
 *    Gordon Sheridan, <gordon@netscape.com>
 *    Patrick C. Beard <beard@netscape.com>
 *    Brian Ryner <bryner@netscape.com>
 */

#include "nsMemoryCacheDevice.h"
#include "nsCacheService.h"
#include "nsICacheService.h"
#include "nsIStorageStream.h"
#include "nsICacheVisitor.h"
#include "nsCRT.h"

// The memory cache implements the "LRU-SP" caching algorithm described in
// "LRU-SP: A Size-Adjusted and Popularity-Aware LRU Replacement Algorithm
// for Web Caching" by Kai Cheng and Yahiko Kambayashi.

// We keep ceil(log2(mHardLimit+1)) LRU queues.  The queues hold exponentially
// increasing ranges of floor(log2((size/nref))) values for entries.

const char *gMemoryDeviceID      = "memory";


nsMemoryCacheDevice::nsMemoryCacheDevice()
    : mInitialized(PR_FALSE),
      mEvictionList(nsnull),
      mEvictionThreshold(40 * 1024),
      mHardLimit(4 * 1024 * 1024),  // set default memory limit, in case prefs aren't available
      mTotalSize(0),
      mInactiveSize(0),
      mEntryCount(0),
      mMaxEntryCount(0),
      mQueueCount(0)
{
    // mEvictionList is created lazily to avoid re-creating it if the
    // capacity is set immediately.
}


nsMemoryCacheDevice::~nsMemoryCacheDevice()
{    
    Shutdown();
}


nsresult
nsMemoryCacheDevice::Init()
{
    if (mInitialized)  return NS_ERROR_ALREADY_INITIALIZED;

    nsresult  rv = mMemCacheEntries.Init();
    
    // set some default memory limits, in case prefs aren't available
    mSoftLimit = (mHardLimit * 9) / 10;

    mInitialized = NS_SUCCEEDED(rv);
    return rv;
}


nsresult
nsMemoryCacheDevice::Shutdown()
{
    NS_ASSERTION(mInitialized, "### attempting to shutdown while not initialized.\n");
    NS_ENSURE_TRUE(mInitialized, NS_ERROR_NOT_INITIALIZED);
    
    mMemCacheEntries.Shutdown();

    // evict all entries
    nsCacheEntry * entry, * next;

    for (int i = mQueueCount - 1; i >= 0; --i) {
        entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
        while (entry != &mEvictionList[i]) {
            NS_ASSERTION(entry->IsInUse() == PR_FALSE, "### shutting down with active entries.\n");
            next = (nsCacheEntry *)PR_NEXT_LINK(entry);
            PR_REMOVE_AND_INIT_LINK(entry);
        
            // update statistics
            PRInt32 memoryRecovered = (PRInt32)entry->Size();
            mTotalSize    -= memoryRecovered;
            mInactiveSize -= memoryRecovered;
            --mEntryCount;

            delete entry;
            entry = next;
        }
    }

/*
 * we're not factoring in changes to meta data yet...    
 *  NS_ASSERTION(mTotalSize == 0, "### mem cache leaking entries?\n");
 */
    NS_ASSERTION(mInactiveSize == 0, "### mem cache leaking entries?\n");
    NS_ASSERTION(mEntryCount == 0, "### mem cache leaking entries?\n");
    
    mInitialized = PR_FALSE;

    delete[] mEvictionList;
    mEvictionList = nsnull;

    return NS_OK;
}


const char *
nsMemoryCacheDevice::GetDeviceID()
{
    return gMemoryDeviceID;
}


nsCacheEntry *
nsMemoryCacheDevice::FindEntry(nsCString * key)
{
    nsCacheEntry * entry = mMemCacheEntries.GetEntry(key);
    if (!entry)  return nsnull;

    // move entry to the tail of an eviction list
    PR_REMOVE_AND_INIT_LINK(entry);
    EnsureEvictionLists();
    PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, 0)]);
    
    mInactiveSize -= entry->Size();

    return entry;
}


nsresult
nsMemoryCacheDevice::DeactivateEntry(nsCacheEntry * entry)
{
    if (entry->IsDoomed()) {
#if debug
        // XXX verify we've removed it from mMemCacheEntries & eviction list
#endif
        // update statistics
        mTotalSize    -= entry->Size();
        --mEntryCount;

        delete entry;
        return NS_OK;
    }

    nsCacheEntry * ourEntry = mMemCacheEntries.GetEntry(entry->Key());
    NS_ASSERTION(ourEntry, "DeactivateEntry called for an entry we don't have!");
    NS_ASSERTION(entry == ourEntry, "entry doesn't match ourEntry");
    if (ourEntry != entry)
        return NS_ERROR_INVALID_POINTER;

    mInactiveSize += entry->Size();
    EvictEntriesIfNecessary();

    return NS_OK;
}


nsresult
nsMemoryCacheDevice::BindEntry(nsCacheEntry * entry)
{
	if (!entry->IsDoomed()) {
 	    NS_ASSERTION(PR_CLIST_IS_EMPTY(entry),"entry is already on a list!");
	
		// append entry to the eviction list
        EnsureEvictionLists();
        PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, 0)]);

        // add entry to hashtable of mem cache entries
        nsresult  rv = mMemCacheEntries.AddEntry(entry);
        if (NS_FAILED(rv)) {
            PR_REMOVE_AND_INIT_LINK(entry);
            return rv;
        }
	}

    // add size of entry to memory totals
    ++mEntryCount;
    if (mMaxEntryCount < mEntryCount) mMaxEntryCount = mEntryCount;

    mTotalSize += entry->Size();
    EvictEntriesIfNecessary();
    
    return NS_OK;
}


void
nsMemoryCacheDevice::DoomEntry(nsCacheEntry * entry)
{
    // XXX debug code to verify we have entry
    mMemCacheEntries.RemoveEntry(entry);

    // remove entry from our eviction list
    PR_REMOVE_AND_INIT_LINK(entry);
}


nsresult
nsMemoryCacheDevice::OpenInputStreamForEntry( nsCacheEntry *    entry,
                                              nsCacheAccessMode mode,
                                              PRUint32          offset,
                                              nsIInputStream ** result)
{
    NS_ENSURE_ARG_POINTER(entry);
    NS_ENSURE_ARG_POINTER(result);

    nsCOMPtr<nsISupports> data;
    nsCOMPtr<nsIStorageStream> storage;

    nsresult rv = entry->GetData(getter_AddRefs(data));
    if (NS_FAILED(rv))
        return rv;

    if (data) {
        storage = do_QueryInterface(data, &rv);
        if (NS_FAILED(rv))
            return rv;
    }
    else {
        rv = NS_NewStorageStream(4096, PRUint32(-1), getter_AddRefs(storage));
        if (NS_FAILED(rv))
            return rv;
        entry->SetData(storage);
    }

    return storage->NewInputStream(offset, result);
}

nsresult
nsMemoryCacheDevice::OpenOutputStreamForEntry( nsCacheEntry *     entry,
                                               nsCacheAccessMode  mode,
                                               PRUint32           offset,
                                               nsIOutputStream ** result)
{
    NS_ENSURE_ARG_POINTER(entry);
    NS_ENSURE_ARG_POINTER(result);

    nsCOMPtr<nsISupports> data;
    nsCOMPtr<nsIStorageStream> storage;

    nsresult rv = entry->GetData(getter_AddRefs(data));
    if (NS_FAILED(rv))
        return rv;

    if (data) {
        storage = do_QueryInterface(data, &rv);
        if (NS_FAILED(rv))
            return rv;
    }
    else {
        rv = NS_NewStorageStream(4096, PRUint32(-1), getter_AddRefs(storage));
        if (NS_FAILED(rv))
            return rv;
        entry->SetData(storage);
    }

    return storage->GetOutputStream(offset, result);
}


nsresult
nsMemoryCacheDevice::GetFileForEntry( nsCacheEntry *    entry,
                                      nsIFile **        result )
{
    return NS_ERROR_NOT_IMPLEMENTED;
}


nsresult
nsMemoryCacheDevice::OnDataSizeChange( nsCacheEntry * entry, PRInt32 deltaSize)
{
    if (entry->IsStreamData()) {
        // we have the right to refuse or pre-evict
        PRUint32  newSize = entry->DataSize() + deltaSize;
        if ((PRInt32) newSize > mSoftLimit) {
            nsresult rv = nsCacheService::DoomEntry(entry);
            NS_ASSERTION(NS_SUCCEEDED(rv),"DoomEntry() failed.");
            return NS_ERROR_ABORT;
        }
    }

    // adjust our totals
    mTotalSize    += deltaSize;
    
    if (!entry->IsDoomed()) {
        // move entry to the tail of the appropriate eviction list
        PR_REMOVE_AND_INIT_LINK(entry);
        EnsureEvictionLists();
        PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, deltaSize)]);
    }

    EvictEntriesIfNecessary();

    return NS_OK;
}


void
nsMemoryCacheDevice::AdjustMemoryLimits(PRInt32  softLimit, PRInt32  hardLimit)
{
    mSoftLimit = softLimit;
    mHardLimit = hardLimit;

    // First, evict entries that won't fit into the new cache size.
    EvictEntriesIfNecessary();

    // Create the eviction list array at the new size and then insert
    // all of the entries into it.
    PRInt32 oldQueueCount = mQueueCount;
    PRCList* oldEvictionList = mEvictionList;
    CreateEvictionLists();
    
    for (PRInt32 i = PR_MIN(oldQueueCount, mQueueCount) - 1; i >= 0; --i) {
        nsCacheEntry* entry = (nsCacheEntry*) PR_LIST_HEAD(&oldEvictionList[i]);
        while (entry != &oldEvictionList[i]) {
            nsCacheEntry* next = (nsCacheEntry*) PR_NEXT_LINK(entry);
            PR_APPEND_LINK(entry, &mEvictionList[i]);
            entry = next;
        }
    }

    delete[] oldEvictionList;
}


void
nsMemoryCacheDevice::EvictEntry(nsCacheEntry * entry)
{
    // remove entry from our hashtable
    mMemCacheEntries.RemoveEntry(entry);
    
    // remove entry from the eviction list
    PR_REMOVE_AND_INIT_LINK(entry);
    
    // update statistics
    PRInt32 memoryRecovered = (PRInt32)entry->Size();
    mTotalSize    -= memoryRecovered;
    mInactiveSize -= memoryRecovered;
    --mEntryCount;

    delete entry;
}


void
nsMemoryCacheDevice::EvictEntriesIfNecessary(void)
{
    nsCacheEntry * entry, * next;

    if ((mTotalSize < mHardLimit) && (mInactiveSize < mSoftLimit))
        return;

    for (int i = mQueueCount - 1; i >= 0; --i) {
        entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
        while (entry != &mEvictionList[i]) {
            if (entry->IsInUse()) {
                entry = (nsCacheEntry *)PR_NEXT_LINK(entry);
                continue;
            }

            next = (nsCacheEntry *)PR_NEXT_LINK(entry);
            EvictEntry(entry);
            entry = next;

            if ((mTotalSize < mHardLimit) && (mInactiveSize < mSoftLimit))
                return;
        }
    }
}


int
nsMemoryCacheDevice::EvictionList(nsCacheEntry * entry, PRInt32  deltaSize)
{
    PRInt32  size = deltaSize + (PRInt32)entry->Size();

    // favor items which never expire by putting them in the lowest-index queue
    if (entry->ExpirationTime() == NO_EXPIRATION_TIME)
        return 0;

    // compute which eviction queue this entry should go into, based on
    // floor(log2(size/nref))
    return PR_FloorLog2(size / (entry->FetchCount() + 1));
}


nsresult
nsMemoryCacheDevice::Visit(nsICacheVisitor * visitor)
{
    nsMemoryCacheDeviceInfo * deviceInfo = new nsMemoryCacheDeviceInfo(this);
    nsCOMPtr<nsICacheDeviceInfo> deviceRef(deviceInfo);
    if (!deviceInfo) return NS_ERROR_OUT_OF_MEMORY;

    PRBool keepGoing;
    nsresult rv = visitor->VisitDevice(gMemoryDeviceID, deviceInfo, &keepGoing);
    if (NS_FAILED(rv)) return rv;

    if (!keepGoing)
        return NS_OK;

    nsCacheEntry *              entry;
    nsCOMPtr<nsICacheEntryInfo> entryRef;

    for (int i = mQueueCount - 1; i >= 0; --i) {
        entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
        while (entry != &mEvictionList[i]) {
            nsCacheEntryInfo * entryInfo = new nsCacheEntryInfo(entry);
            if (!entryInfo) return NS_ERROR_OUT_OF_MEMORY;
            entryRef = entryInfo;

            rv = visitor->VisitEntry(gMemoryDeviceID, entryInfo, &keepGoing);
            entryInfo->DetachEntry();
            if (NS_FAILED(rv)) return rv;
            if (!keepGoing) break;

            entry = (nsCacheEntry *)PR_NEXT_LINK(entry);
        }
    }
    return NS_OK;
}


nsresult
nsMemoryCacheDevice::EvictEntries(const char * clientID)
{
    nsCacheEntry * entry;
    PRUint32 prefixLength = (clientID ? strlen(clientID) : 0);

    for (int i = mQueueCount - 1; i >= 0; --i) {
        PRCList * elem = PR_LIST_HEAD(&mEvictionList[i]);
        while (elem != &mEvictionList[i]) {
            entry = (nsCacheEntry *)elem;
            elem = PR_NEXT_LINK(elem);
            
            const char * key = entry->Key()->get();
            if (clientID && nsCRT::strncmp(clientID, key, prefixLength) != 0)
                continue;
            
            if (entry->IsInUse()) {
                nsresult rv = nsCacheService::DoomEntry(entry);
                if (NS_FAILED(rv)) return rv;
            } else {
                EvictEntry(entry);
            }
        }
    }
    return NS_OK;
}


void
nsMemoryCacheDevice::SetCapacity(PRInt32  capacity)
{
    PRInt32 hardLimit = capacity * 1024;  // convert k into bytes
    PRInt32 softLimit = (hardLimit * 9) / 10;
    AdjustMemoryLimits(softLimit, hardLimit);
}

inline void
nsMemoryCacheDevice::EnsureEvictionLists()
{
    if (!mEvictionList)
        CreateEvictionLists();
}

void
nsMemoryCacheDevice::CreateEvictionLists()
{
    // Create log2 (mHardLimit + 1) LRU queues

    mQueueCount = PR_CeilingLog2(mHardLimit + 1);
    mEvictionList = new PRCList[mQueueCount];
    for (int i = 0; i < mQueueCount; ++i)
        PR_INIT_CLIST(&mEvictionList[i]);
}

/******************************************************************************
 * nsMemoryCacheDeviceInfo - for implementing about:cache
 *****************************************************************************/


NS_IMPL_ISUPPORTS1(nsMemoryCacheDeviceInfo, nsICacheDeviceInfo);


NS_IMETHODIMP
nsMemoryCacheDeviceInfo::GetDescription(char ** result)
{
    NS_ENSURE_ARG_POINTER(result);
    *result = nsCRT::strdup("Memory cache device");
    if (!*result) return NS_ERROR_OUT_OF_MEMORY;
    return NS_OK;
}


NS_IMETHODIMP
nsMemoryCacheDeviceInfo::GetUsageReport(char ** result)
{
    NS_ENSURE_ARG_POINTER(result);
    *result = nsCRT::strdup("Memory cache usage report:");
    if (!*result) return NS_ERROR_OUT_OF_MEMORY;
    return NS_OK;
}


NS_IMETHODIMP
nsMemoryCacheDeviceInfo::GetEntryCount(PRUint32 * result)
{
    NS_ENSURE_ARG_POINTER(result);
    // XXX compare calculated count vs. mEntryCount
    *result = (PRUint32)mDevice->mEntryCount;
    return NS_OK;
}


NS_IMETHODIMP
nsMemoryCacheDeviceInfo::GetTotalSize(PRUint32 * result)
{
    NS_ENSURE_ARG_POINTER(result);
    *result = (PRUint32)mDevice->mTotalSize;
    return NS_OK;
}


NS_IMETHODIMP
nsMemoryCacheDeviceInfo::GetMaximumSize(PRUint32 * result)
{
    NS_ENSURE_ARG_POINTER(result);
    *result = (PRUint32)mDevice->mHardLimit;
    return NS_OK;
}