// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"
#include "AssetData.h"
#include "FileCache.h"

class FReimportFeedbackContext;
class IAssetRegistry;
class UFactory;

/** Class responsible for watching a specific content directory for changes */
class FContentDirectoryMonitor
{
public:
    /**
     * Constructor.
     * @param InDirectory			Content directory path to monitor. Assumed to be absolute.
     * @param InMatchRules			Rules to select what will apply to this folder
     * @param InMountedContentPath	(optional) Mounted content path (eg /Engine/, /Game/) to which InDirectory maps.
     */
    FContentDirectoryMonitor(const FString& InDirectory, const DirectoryWatcher::FMatchRules& InMatchRules, const FString& InMountedContentPath = FString());

    /** Tick this monitor's cache to give it a chance to finish scanning for files */
    void Tick();

    /** Start processing any outstanding changes this monitor is aware of */
    int32 StartProcessing();

    /** Extract the files we need to import from our outstanding changes (happens first)*/
    void ProcessAdditions(const DirectoryWatcher::FTimeLimit& TimeLimit, TArray<UPackage*>& OutPackagesToSave, const TMap<FString, TArray<UFactory*>>& InFactoriesByExtension, FReimportFeedbackContext& Context);

    /** Process the outstanding changes that we have cached */
    void ProcessModifications(const DirectoryWatcher::FTimeLimit& TimeLimit, TArray<UPackage*>& OutPackagesToSave, FReimportFeedbackContext& Context);

    /** Returns the number of source files deleted in outstanding changes. */
    int32 GetDeletedFilesNum() const { return DeletedFiles.Num(); }

    /** Extract the assets we need to delete from our outstanding changes (happens last) */
    void ExtractAssetsToDelete(TArray<FAssetData>& OutAssetsToDelete);

    /** Abort the current processing operation */
    void Abort();

    /** Report an external change to the manager, such that a subsequent equal change reported by the os be ignored */
    void IgnoreNewFile(const FString& Filename);
    void IgnoreFileModification(const FString& Filename);
    void IgnoreMovedFile(const FString& SrcFilename, const FString& DstFilename);
    void IgnoreDeletedFile(const FString& Filename);

    /** Destroy this monitor including its cache */
    void Destroy();

    /** Get the directory that this monitor applies to */
    const FString& GetDirectory() const { return Cache.GetDirectory(); }

    /** Get the content mount point that this monitor applies to */
    const FString& GetMountPoint() const { return MountedContentPath; }

public:
    /** Get the number of outstanding changes that we potentially have to process (when not already processing) */
    int32 GetNumUnprocessedChanges() const;

    /** Iterate the current set of unprocessed file system changes */
    void IterateUnprocessedChanges(TFunctionRef<bool(const DirectoryWatcher::FUpdateCacheTransaction&, const FDateTime&)>) const;

private:
    /** Import a new asset into the specified package path, from the specified file */
    void ImportAsset(const FString& PackagePath, const FString& Filename, TArray<UPackage*>& OutPackagesToSave, const TMap<FString, TArray<UFactory*>>& InFactoriesByExtension, FReimportFeedbackContext& Context);

    /** Reimport a specific asset */
    void ReimportAsset(UObject* InAsset, const FString& FullFilename, TArray<UPackage*>& OutPackagesToSave, FReimportFeedbackContext& Context);

    /** Set the specified asset to import from the specified file, then attempt to reimport it */
    void ReimportAssetWithNewSource(UObject* InAsset, const FString& FullFilename, TArray<UPackage*>& OutPackagesToSave, FReimportFeedbackContext& Context);

    /** Check whether we should consider a change for the specified transaction */
    bool ShouldConsiderChange(const DirectoryWatcher::FUpdateCacheTransaction& Transaction) const;

private:
    /** The file cache that monitors and reflects the content directory. */
    DirectoryWatcher::FFileCache Cache;

    /** The mounted content path for this monitor (eg /Game/) */
    FString MountedContentPath;

    /** A list of file system changes that are due to be processed */
    TArray<DirectoryWatcher::FUpdateCacheTransaction> AddedFiles, ModifiedFiles, DeletedFiles;

    /** The last time we attempted to save the cache file */
    double LastSaveTime;

    /** Cached asset registry ptr */
    IAssetRegistry* Registry;

    /** The interval between potential re-saves of the cache file */
    static const int32 ResaveIntervalS = 60;
};