//
// Copyright (c) 2008-2017 the Urho3D project.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#include "../Precompiled.h"

#include "../IO/File.h"
#include "../IO/FileSystem.h"
#include "../IO/FileWatcher.h"
#include "../IO/Log.h"

#ifdef _WIN32
#include <windows.h>
#elif __linux__
#include <sys/inotify.h>
extern "C"
{
// Need read/close for inotify
#include "unistd.h"
}
#elif defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
extern "C"
{
#include "../IO/MacFileWatcher.h"
}
#endif

namespace Atomic
{
#ifndef __APPLE__
static const unsigned BUFFERSIZE = 4096;
#endif

FileWatcher::FileWatcher(Context* context) :
    Object(context),
    fileSystem_(GetSubsystem<FileSystem>()),
    delay_(1.0f),
    watchSubDirs_(false)
{
#ifdef ATOMIC_FILEWATCHER
#ifdef __linux__
    watchHandle_ = inotify_init();
#elif defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
    supported_ = IsFileWatcherSupported();
#endif
#endif
}

FileWatcher::~FileWatcher()
{
    StopWatching();
#ifdef ATOMIC_FILEWATCHER
#ifdef __linux__
    close(watchHandle_);
#endif
#endif
}

bool FileWatcher::StartWatching(const String& pathName, bool watchSubDirs)
{
    if (!fileSystem_)
    {
        ATOMIC_LOGERROR("No FileSystem, can not start watching");
        return false;
    }

    // Stop any previous watching
    StopWatching();

#if defined(ATOMIC_FILEWATCHER) && defined(ATOMIC_THREADING)
#ifdef _WIN32
    String nativePath = GetNativePath(RemoveTrailingSlash(pathName));

    // ATOMIC BEGIN

    // Create a dummy file to make sure the path is writeable, otherwise we would hang at exit
    // This isn't terribly elegant, though avoids a cluser of Windows security API
    String dummyFileName = nativePath + "/" + "dummy.tmp";
    File file(context_, dummyFileName, FILE_WRITE);
    if (file.IsOpen())
    {
        file.Close();
        if (fileSystem_)
            fileSystem_->Delete(dummyFileName);
    }
    else
    {
        ATOMIC_LOGDEBUGF("FileWatcher::StartWatching - Ignoring non-writable path %s", nativePath.CString());
        return false;
    }

    // ATOMIC END

    dirHandle_ = (void*)CreateFileW(
        WString(nativePath).CString(),
        FILE_LIST_DIRECTORY,
        FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE,
        0,
        OPEN_EXISTING,
        FILE_FLAG_BACKUP_SEMANTICS,
        0);

    if (dirHandle_ != INVALID_HANDLE_VALUE)
    {
        path_ = AddTrailingSlash(pathName);
        watchSubDirs_ = watchSubDirs;
        Run();

        ATOMIC_LOGDEBUG("Started watching path " + pathName);
        return true;
    }
    else
    {
        ATOMIC_LOGERROR("Failed to start watching path " + pathName);
        return false;
    }
#elif defined(__linux__)
    int flags = IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_FROM | IN_MOVED_TO;
    int handle = inotify_add_watch(watchHandle_, pathName.CString(), (unsigned)flags);

    if (handle < 0)
    {
        ATOMIC_LOGERROR("Failed to start watching path " + pathName);
        return false;
    }
    else
    {
        // Store the root path here when reconstructed with inotify later
        dirHandle_[handle] = "";
        path_ = AddTrailingSlash(pathName);
        watchSubDirs_ = watchSubDirs;

        if (watchSubDirs_)
        {
            Vector<String> subDirs;
            fileSystem_->ScanDir(subDirs, pathName, "*", SCAN_DIRS, true);

            for (unsigned i = 0; i < subDirs.Size(); ++i)
            {
                String subDirFullPath = AddTrailingSlash(path_ + subDirs[i]);

                // Don't watch ./ or ../ sub-directories
                if (!subDirFullPath.EndsWith("./"))
                {
                    handle = inotify_add_watch(watchHandle_, subDirFullPath.CString(), (unsigned)flags);
                    if (handle < 0)
                        ATOMIC_LOGERROR("Failed to start watching subdirectory path " + subDirFullPath);
                    else
                    {
                        // Store sub-directory to reconstruct later from inotify
                        dirHandle_[handle] = AddTrailingSlash(subDirs[i]);
                    }
                }
            }
        }
        Run();

        ATOMIC_LOGDEBUG("Started watching path " + pathName);
        return true;
    }
#elif defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
    if (!supported_)
    {
        ATOMIC_LOGERROR("Individual file watching not supported by this OS version, can not start watching path " + pathName);
        return false;
    }

    watcher_ = CreateFileWatcher(pathName.CString(), watchSubDirs);
    if (watcher_)
    {
        path_ = AddTrailingSlash(pathName);
        watchSubDirs_ = watchSubDirs;
        Run();

        ATOMIC_LOGDEBUG("Started watching path " + pathName);
        return true;
    }
    else
    {
        ATOMIC_LOGERROR("Failed to start watching path " + pathName);
        return false;
    }
#else
    ATOMIC_LOGERROR("FileWatcher not implemented, can not start watching path " + pathName);
    return false;
#endif
#else
    ATOMIC_LOGDEBUG("FileWatcher feature not enabled");
    return false;
#endif
}

void FileWatcher::StopWatching()
{
    if (handle_)
    {
        shouldRun_ = false;

        // Create and delete a dummy file to make sure the watcher loop terminates
        // This is only required on Windows platform
        // TODO: Remove this temp write approach as it depends on user write privilege
#ifdef _WIN32
        String dummyFileName = path_ + "dummy.tmp";
        File file(context_, dummyFileName, FILE_WRITE);
        file.Close();
        if (fileSystem_)
            fileSystem_->Delete(dummyFileName);
#endif

#if defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
        // Our implementation of file watcher requires the thread to be stopped first before closing the watcher
        Stop();
#endif

#ifdef _WIN32
        CloseHandle((HANDLE)dirHandle_);
#elif defined(__linux__)
        for (HashMap<int, String>::Iterator i = dirHandle_.Begin(); i != dirHandle_.End(); ++i)
            inotify_rm_watch(watchHandle_, i->first_);
        dirHandle_.Clear();
#elif defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
        CloseFileWatcher(watcher_);
#endif

#ifndef __APPLE__
        Stop();
#endif

        ATOMIC_LOGDEBUG("Stopped watching path " + path_);
        path_.Clear();
    }
}

void FileWatcher::SetDelay(float interval)
{
    delay_ = Max(interval, 0.0f);
}

void FileWatcher::ThreadFunction()
{
#ifdef ATOMIC_FILEWATCHER
#ifdef _WIN32
    unsigned char buffer[BUFFERSIZE];
    DWORD bytesFilled = 0;

    while (shouldRun_)
    {
        if (ReadDirectoryChangesW((HANDLE)dirHandle_,
            buffer,
            BUFFERSIZE,
            watchSubDirs_,
            FILE_NOTIFY_CHANGE_FILE_NAME |
            FILE_NOTIFY_CHANGE_LAST_WRITE,
            &bytesFilled,
            0,
            0))
        {
            unsigned offset = 0;

            while (offset < bytesFilled)
            {
                FILE_NOTIFY_INFORMATION* record = (FILE_NOTIFY_INFORMATION*)&buffer[offset];

                if (record->Action == FILE_ACTION_MODIFIED || record->Action == FILE_ACTION_RENAMED_NEW_NAME)
                {
                    String fileName;
                    const wchar_t* src = record->FileName;
                    const wchar_t* end = src + record->FileNameLength / 2;
                    while (src < end)
                        fileName.AppendUTF8(String::DecodeUTF16(src));

                    fileName = GetInternalPath(fileName);
                    AddChange(fileName);
                }

                if (!record->NextEntryOffset)
                    break;
                else
                    offset += record->NextEntryOffset;
            }
        }
    }
#elif defined(__linux__)
    unsigned char buffer[BUFFERSIZE];

    while (shouldRun_)
    {
        int i = 0;
        int length = (int)read(watchHandle_, buffer, sizeof(buffer));

        if (length < 0)
            return;

        while (i < length)
        {
            inotify_event* event = (inotify_event*)&buffer[i];

            if (event->len > 0)
            {
                if (event->mask & IN_MODIFY || event->mask & IN_MOVE)
                {
                    String fileName;
                    fileName = dirHandle_[event->wd] + event->name;
                    AddChange(fileName);
                }
            }

            i += sizeof(inotify_event) + event->len;
        }
    }
#elif defined(__APPLE__) && !defined(IOS) && !defined(TVOS)
    while (shouldRun_)
    {
        Time::Sleep(100);

        String changes = ReadFileWatcher(watcher_);
        if (!changes.Empty())
        {
            Vector<String> fileNames = changes.Split(1);
            for (unsigned i = 0; i < fileNames.Size(); ++i)
                AddChange(fileNames[i]);
        }
    }
#endif
#endif
}

void FileWatcher::AddChange(const String& fileName)
{
    MutexLock lock(changesMutex_);

    // Reset the timer associated with the filename. Will be notified once timer exceeds the delay
    changes_[fileName].Reset();
}

bool FileWatcher::GetNextChange(String& dest)
{
    MutexLock lock(changesMutex_);

    unsigned delayMsec = (unsigned)(delay_ * 1000.0f);

    if (changes_.Empty())
        return false;
    else
    {
        for (HashMap<String, Timer>::Iterator i = changes_.Begin(); i != changes_.End(); ++i)
        {
            if (i->second_.GetMSec(false) >= delayMsec)
            {
                dest = i->first_;
                changes_.Erase(i);
                return true;
            }
        }

        return false;
    }
}

}