/***
    Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: Watcher.Linux.cpp
    Date: 2022-4-10
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "Watcher.Linux.hpp"
#include <sys/inotify.h>

#include <Source/Loop/LSHandle.hpp>

namespace Aurora::IO::FS
{
    struct LinuxWatcherHandle : public Loop::LSHandle
    {
        LinuxWatcherHandle(int handle) : Loop::LSHandle(AuUInt(handle))
        {}

        virtual Loop::ELoopSource GetType() override;
    };

    Loop::ELoopSource LinuxWatcherHandle::GetType()
    {
        return Loop::ELoopSource::eSourceFileWatcher;
    }

    LinuxWatcher::~LinuxWatcher()
    {
        Deinit();
    }

    bool LinuxWatcher::AddWatch(const WatchRequest &request)
    {
        AuCtorCode_t code;
        bool bIsDirectory {};
        AuUInt32 mask {};
        UnixCachedPath cached;

        auto &file = request.watch;

        AU_LOCK_GUARD(this->spinlock_);

        if (this->inotifyHandle_ == -1)
        {
            SysPushErrorUninitialized();
            return false;
        }

        AuString translated;
        if (!AuIOFS::NormalizePath(translated, file.path))
        {
            SysPushErrorIO();
            translated = file.path;
        }

        // Create the NT path in the midst of path normalization
        cached.strNormalizedPath = AuTryConstruct<AuString>(code, translated);
        if (!code)
        {
            SysPushErrorMem();
            return false;
        }

        cached.strTheCakeIsALie = AuTryConstruct<AuString>(code, file.path);
        if (!code)
        {
            SysPushErrorMem();
            return false;
        }

        cached.userData = file.userData;

        if (AuIOFS::DirExists(translated))
        {
            bIsDirectory = true;
        }

        mask |= IN_ATTRIB;

        if (bIsDirectory)
        {
            mask |=  IN_MOVE_SELF;

            if (AuExists(request.events, EWatchEvent::eFileCreate))
            {
                mask |=  IN_CREATE | IN_MOVED_TO /*may as well. easter egg.*/;
            }

            if (AuExists(request.events, EWatchEvent::eFileDelete))
            {
                mask |= IN_DELETE | IN_MOVED_FROM;
            }
        }

        if (AuExists(request.events, EWatchEvent::eFileModify) || !bIsDirectory)
        {
            mask |= IN_MODIFY;
        }

        //if (AuExists(request.events, EWatchEvent::eSelfDelete))
        {
            mask |= IN_DELETE_SELF | IN_MOVE_SELF;
        }

        int ret = inotify_add_watch(this->inotifyHandle_, cached.strNormalizedPath.c_str(), mask);
        if (ret == -1)
        {
            // TODO: push error
            return false;
        }

        cached.watcherWd = ret;
        cached.bIsDir = bIsDirectory;

        if (!AuTryInsert(this->paths_, cached))
        {
            SysPushErrorMem();
            auto ree = inotify_rm_watch(this->inotifyHandle_, ret);
            if (ree == -1)
            {
                SysPushErrorGeneric();
            }
            return false;
        }

        return true;
    }

    bool LinuxWatcher::RemoveByName(const AuString &path)
    {
        AU_LOCK_GUARD(this->spinlock_);
        AuString strNormalized;

        if (!AuIOFS::NormalizePath(strNormalized, path))
        {
            return false;
        }

        return AuRemoveIf(this->paths_, [&](const UnixCachedPath &object) -> bool
        {
            if ((strNormalized == object.strNormalizedPath) || 
                (strNormalized.empty() && object.strNormalizedPath == path))
            {

                auto ree = inotify_rm_watch(this->inotifyHandle_, object.watcherWd);
                if (ree == -1)
                {
                    SysPushErrorGeneric();
                }

                return true;
            }
            
            return false;
        });
    }

    bool LinuxWatcher::RemoveByPrivateContext(const AuSPtr<UserWatchData> &file)
    {
        AU_LOCK_GUARD(this->spinlock_);

        return AuRemoveIf(this->paths_, [&](const UnixCachedPath &object) -> bool
        {
            if (file != object.userData)
            {
                return false;
            }

            auto ree = inotify_rm_watch(this->inotifyHandle_, object.watcherWd);
            if (ree == -1)
            {
                SysPushErrorGeneric();
            }

            return true;
        });
    }

    AuSPtr<Loop::ILoopSource> LinuxWatcher::AsLoopSource()
    {
        AU_LOCK_GUARD(this->spinlock_);
        return this->loopSource_;
    }

    AuList<WatchEvent>       LinuxWatcher::QueryUpdates()
    {
        AU_LOCK_GUARD(this->spinlock_);

        bool bSuccess {};
        AuList<WatchEvent> ret;

        if (this->inotifyHandle_ == -1)
        {
            SysPushErrorUninitialized();
            return ret;
        }

        while (true)
        {
            char buffer[4096];
            
            int length = read(this->inotifyHandle_, &buffer, sizeof(buffer));
            int index {};

            if (length <= -1)
            {
                if (errno == EAGAIN || errno == EWOULDBLOCK)
                {
                    return ret;
                }
                else
                {
                    SysPushErrorGeneric();
                    return ret;
                }
            }

            while (index < length)
            {
                WatchEvent event;
                auto & header = *(inotify_event *)(buffer + index);
                index += sizeof(struct inotify_event) + header.len; 

#if 0
                printf("watcher event: %i %i %i\n", index, header.wd, header.mask);
#endif
                if (!AuTryResize(event.file, header.len))
                {
                    SysPushErrorMem("Out of memory -> can't consume body. Will misalign stream... Deinitializing...");
                    Deinit();
                    return ret;
                }

                AuMemcpy(event.file.data(), header.name, header.len);
                bool bFound {}, bCrinkled{}, bIsDir{};

                for (auto & path : this->paths_)
                {
                    if (path.watcherWd != header.wd)
                    {
                        continue;
                    }
                    
                    event.watch = WatchedFile {path.userData, path.strTheCakeIsALie};
                    bCrinkled = path.strNormalizedPath == event.file;
                    bFound = true;
                    bIsDir = path.bIsDir;
                    break;
                }

                if (!bFound)
                {
                    SysPushErrorGeneric("Couldn't find inotify wd for event");
                    continue;
                }

                if (event.file.empty())
                {
                    event.file = event.watch.path; // TODO: alloc
                }

                event.event = EWatchEvent::eEnumInvalid;

                if (header.mask & (IN_CREATE | IN_MOVED_TO))
                {
                    if (event.event != EWatchEvent::eEnumInvalid)
                    {
                        AuTryInsert(ret, AuConstReference(event));
                    }
                    event.event = EWatchEvent::eFileCreate;
                }
                else if (header.mask & (IN_DELETE | IN_MOVED_FROM))
                {
                    if (event.event != EWatchEvent::eEnumInvalid)
                    {
                        AuTryInsert(ret, AuConstReference(event));
                    }
                    event.event = EWatchEvent::eFileDelete;
                }
                else if (header.mask & (IN_DELETE_SELF | IN_MOVE_SELF))
                {
                    if (event.event != EWatchEvent::eEnumInvalid)
                    {
                        AuTryInsert(ret, AuConstReference(event));
                    }
                    event.event = EWatchEvent::eSelfDelete;
                }
                else if (header.mask & (IN_MODIFY))
                {
                    if (event.event != EWatchEvent::eEnumInvalid)
                    {
                        AuTryInsert(ret, AuConstReference(event));
                    }
                    event.event = EWatchEvent::eFileModify;
                }

                if (event.file.empty() || (bCrinkled) || (header.mask & IN_MOVE_SELF))
                {
                    if (event.event != EWatchEvent::eEnumInvalid)
                    {
                        AuTryInsert(ret, AuConstReference(event));
                    }

                    if (header.mask & IN_ISDIR)
                    {
                        event.event = EWatchEvent::eSelfModify;
                    }
                    else
                    {
                        event.event = EWatchEvent::eFileModify;
                    }
                }

                if (event.event != EWatchEvent::eEnumInvalid)
                {
                    AuTryInsert(ret, AuConstReference(event));
                }

                if (bIsDir)
                {
                    // The following helps us match the results of the NT impl
                    if ((event.event == EWatchEvent::eFileCreate) ||
                        (event.event == EWatchEvent::eFileDelete)||
                        (event.event == EWatchEvent::eFileModify))
                    {
                        event.event = EWatchEvent::eSelfModify;
                        event.file = event.watch.path; // TODO: alloc
                        AuTryInsert(ret, event);
                    }
                }
            }
        }
        return ret;
    }

    bool LinuxWatcher::Init()
    {
        this->inotifyHandle_ = ::inotify_init1(IN_NONBLOCK);
        if (this->inotifyHandle_ == -1)
        {
            return false;
        }

        this->loopSource_ = AuMakeShared<LinuxWatcherHandle>(this->inotifyHandle_);
        return bool(this->loopSource_);
    }

    void LinuxWatcher::Deinit()
    {
        auto paths = AuExchange(this->paths_, {});
        for (auto handle : paths)
        {
            if (handle.watcherWd != -1)
            {
                auto ree = inotify_rm_watch(this->inotifyHandle_, handle.watcherWd);
                if (ree == -1)
                {
                    SysPushErrorGeneric();
                }
            }
        }

        if ((this->inotifyHandle_ != 0) &&
            (this->inotifyHandle_ != -1))
        {
            ::close(AuExchange(this->inotifyHandle_, -1));
        }
    }

    AUKN_SYM IWatcher *NewWatcherNew()
    {
        auto watcher = _new LinuxWatcher();
        if (!watcher)
        {
            return {};
        }

        if (!watcher->Init())
        {
            delete watcher;
            return {};
        }

        return watcher;
    }

    AUKN_SYM void NewWatcherRelease(IWatcher *watcher)
    {
        AuSafeDelete<LinuxWatcher *>(watcher);
    }
}