#include <xvfs-core.h>
#include <string.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <tcl.h>

#if defined(XVFS_MODE_FLEXIBLE) || defined(XVFS_MODE_SERVER)
#define XVFS_INTERNAL_SERVER_MAGIC "\xD4\xF3\x05\x96\x25\xCF\xAF\xFE"
#define XVFS_INTERNAL_SERVER_MAGIC_LEN 8

struct xvfs_tclfs_server_info {
	char magic[XVFS_INTERNAL_SERVER_MAGIC_LEN];
	int (*registerProc)(Tcl_Interp *interp, struct Xvfs_FSInfo *fsInfo);
};
#endif /* XVFS_MODE_FLEXIBLE || XVFS_MODE_SERVER */

#if defined(XVFS_MODE_SERVER) || defined(XVFS_MODE_STANDALONE) || defined(XVFS_MODE_FLEXIBLE)
#define XVFS_ROOT_MOUNTPOINT "//xvfs:/"

struct xvfs_tclfs_instance_info {
	struct Xvfs_FSInfo *fsInfo;
	Tcl_Obj            *mountpoint;
};

/*
 * Internal Core Utilities
 */
static const char *xvfs_relativePath(Tcl_Obj *path, struct xvfs_tclfs_instance_info *info) {
	const char *pathStr, *rootStr;
	int pathLen, rootLen;

	pathStr = Tcl_GetStringFromObj(path, &pathLen);
	rootStr = Tcl_GetStringFromObj(info->mountpoint, &rootLen);

	if (pathLen < rootLen) {
		return(NULL);
	}

	if (memcmp(pathStr, rootStr, rootLen) != 0) {
		return(NULL);
	}

	if (pathLen == rootLen) {
		return("");
	}

	/* XXX:TODO: Should this use the native OS path separator ? */
	if (pathStr[rootLen] != '/') {
		return(NULL);
	}

	return(pathStr + rootLen + 1);
}

#if 0
/*
 * Currently unused
 */
static const char *xvfs_perror(int xvfs_error) {
	if (xvfs_error >= 0) {
		return("Not an error");
	}

	switch (xvfs_error) {
		case XVFS_RV_ERR_ENOENT:
			return("No such file or directory");
		case XVFS_RV_ERR_EINVAL:
			return("Invalid argument");
		case XVFS_RV_ERR_EISDIR:
			return("Is a directory");
		case XVFS_RV_ERR_ENOTDIR:
			return("Not a directory");
		case XVFS_RV_ERR_EFAULT:
			return("Bad address");
		default:
			return("Unknown error");
	}
}
#endif

static int xvfs_errorToErrno(int xvfs_error) {
	if (xvfs_error >= 0) {
		return(0);
	}

	switch (xvfs_error) {
		case XVFS_RV_ERR_ENOENT:
			return(ENOENT);
		case XVFS_RV_ERR_EINVAL:
			return(EINVAL);
		case XVFS_RV_ERR_EISDIR:
			return(EISDIR);
		case XVFS_RV_ERR_ENOTDIR:
			return(ENOTDIR);
		case XVFS_RV_ERR_EFAULT:
			return(EFAULT);
		default:
			return(ERANGE);
	}
}

/*
 * Xvfs Memory Channel
 */
struct xvfs_tclfs_channel_id {
	Tcl_Channel channel;
	struct xvfs_tclfs_instance_info *fsInstanceInfo;
	Tcl_Obj *path;
	Tcl_WideInt currentOffset;
	Tcl_WideInt fileSize;
};
static Tcl_ChannelType xvfs_tclfs_channelType;

static Tcl_Channel xvfs_tclfs_openChannel(Tcl_Obj *path, struct xvfs_tclfs_instance_info *instanceInfo) {
	struct xvfs_tclfs_channel_id *channelInstanceData;
	Tcl_Channel channel;
	Tcl_StatBuf fileInfo;
	int statRet;

	statRet = instanceInfo->fsInfo->getStatProc(Tcl_GetString(path), &fileInfo);
	if (statRet < 0) {
		return(NULL);
	}

	channelInstanceData = (struct xvfs_tclfs_channel_id *) Tcl_Alloc(sizeof(*channelInstanceData));
	channelInstanceData->currentOffset = 0;
	channelInstanceData->channel = NULL;

	channelInstanceData->fsInstanceInfo = instanceInfo;
	channelInstanceData->path = path;
	channelInstanceData->fileSize = fileInfo.st_size;
	Tcl_IncrRefCount(path);

	channel = Tcl_CreateChannel(&xvfs_tclfs_channelType, Tcl_GetString(path), channelInstanceData, TCL_READABLE);
	if (!channel) {
		Tcl_DecrRefCount(path);
		Tcl_Free((char *) channelInstanceData);

		return(NULL);
	}

	channelInstanceData->channel = channel;

	return(channel);
}

static int xvfs_tclfs_closeChannel(ClientData channelInstanceData_p, Tcl_Interp *interp) {
	struct xvfs_tclfs_channel_id *channelInstanceData;

	channelInstanceData = (struct xvfs_tclfs_channel_id *) channelInstanceData_p;

	Tcl_DecrRefCount(channelInstanceData->path);
	Tcl_Free((char *) channelInstanceData);

	return(0);
}

static int xvfs_tclfs_readChannel(ClientData channelInstanceData_p, char *buf, int bufSize, int *errorCodePtr) {
	struct xvfs_tclfs_channel_id *channelInstanceData;
	const unsigned char *data;
	Tcl_WideInt offset, length;
	char *path;

	channelInstanceData = (struct xvfs_tclfs_channel_id *) channelInstanceData_p;

	path = Tcl_GetString(channelInstanceData->path);
	offset = channelInstanceData->currentOffset;
	length = bufSize;

	data = channelInstanceData->fsInstanceInfo->fsInfo->getDataProc(path, offset, &length);

	if (length < 0) {
		*errorCodePtr = xvfs_errorToErrno(length);

		return(-1);
	}

	memcpy(buf, data, length);

	channelInstanceData->currentOffset += length;

	return(length);
}

static void xvfs_tclfs_watchChannel(ClientData channelInstanceData_p, int mask) {
	if ((mask & TCL_READABLE) != TCL_READABLE) {
		return;
	}

/* XXX:TODO: fprintf(stderr, "Incomplete watch called, mask = %i\n", mask); */
	return;
}

static int xvfs_tclfs_seekChannel(ClientData channelInstanceData_p, long offset, int mode, int *errorCodePtr) {
	struct xvfs_tclfs_channel_id *channelInstanceData;
	Tcl_WideInt newOffset, fileSize;

	channelInstanceData = (struct xvfs_tclfs_channel_id *) channelInstanceData_p;

	newOffset = channelInstanceData->currentOffset;
	fileSize = channelInstanceData->fileSize;

	switch (mode) {
		case SEEK_CUR:
			newOffset += offset;
			break;
		case SEEK_SET:
			newOffset = offset;
			break;
		case SEEK_END:
			newOffset = fileSize + offset;
			break;
		default:
			*errorCodePtr = xvfs_errorToErrno(XVFS_RV_ERR_EINVAL);

			return(-1);
	}

	/*
	 * We allow users to seek right up to the end of the buffer, but
	 * no further, this way if they want to seek backwards from there
	 * it is possible to do so.
	 */
	if (newOffset < 0 || newOffset > fileSize) {
		*errorCodePtr = xvfs_errorToErrno(XVFS_RV_ERR_EINVAL);

		return(-1);
	}

	channelInstanceData->currentOffset = newOffset;

	return(channelInstanceData->currentOffset);
}

static void xvfs_tclfs_prepareChannelType(void) {
	xvfs_tclfs_channelType.typeName = "xvfs";
	xvfs_tclfs_channelType.version = TCL_CHANNEL_VERSION_2;
	xvfs_tclfs_channelType.closeProc = xvfs_tclfs_closeChannel;
	xvfs_tclfs_channelType.inputProc = xvfs_tclfs_readChannel;
	xvfs_tclfs_channelType.outputProc = NULL;
	xvfs_tclfs_channelType.watchProc = xvfs_tclfs_watchChannel;
	xvfs_tclfs_channelType.getHandleProc = NULL;
	xvfs_tclfs_channelType.seekProc = xvfs_tclfs_seekChannel;
	xvfs_tclfs_channelType.setOptionProc = NULL;
	xvfs_tclfs_channelType.getOptionProc = NULL;
	xvfs_tclfs_channelType.close2Proc = NULL;
	xvfs_tclfs_channelType.blockModeProc = NULL;
	xvfs_tclfs_channelType.flushProc = NULL;
	xvfs_tclfs_channelType.handlerProc = NULL;
	xvfs_tclfs_channelType.wideSeekProc = NULL;
	xvfs_tclfs_channelType.threadActionProc = NULL;
	xvfs_tclfs_channelType.truncateProc = NULL;
}

/*
 * Internal Tcl_Filesystem functions, with the appropriate instance info
 */
static int xvfs_tclfs_pathInFilesystem(Tcl_Obj *path, ClientData *dataPtr, struct xvfs_tclfs_instance_info *instanceInfo) {
	const char *relativePath;

	relativePath = xvfs_relativePath(path, instanceInfo);
	if (!relativePath) {
		return(-1);
	}

	return(TCL_OK);
}

static int xvfs_tclfs_stat(Tcl_Obj *path, Tcl_StatBuf *statBuf, struct xvfs_tclfs_instance_info *instanceInfo) {
	const char *pathStr;
	int retval;

	pathStr = xvfs_relativePath(path, instanceInfo);

	retval = instanceInfo->fsInfo->getStatProc(pathStr, statBuf);
	if (retval < 0) {
		retval = -1;
	}

	return(retval);
}

static Tcl_Obj *xvfs_tclfs_listVolumes(struct xvfs_tclfs_instance_info *instanceInfo) {
	return(NULL);
}

static Tcl_Channel xvfs_tclfs_openFileChannel(Tcl_Interp *interp, Tcl_Obj *path, int mode, int permissions, struct xvfs_tclfs_instance_info *instanceInfo) {
	const char *pathStr;

	pathStr = xvfs_relativePath(path, instanceInfo);

	if (mode & O_WRONLY) {
		return(NULL);
	}

	return(xvfs_tclfs_openChannel(Tcl_NewStringObj(pathStr, -1), instanceInfo));
}
#endif /* XVFS_MODE_SERVER || XVFS_MODE_STANDALONE || XVFS_MODE_FLEIXBLE */

#if defined(XVFS_MODE_STANDALONE) || defined(XVFS_MODE_FLEXIBLE)
/*
 * Tcl_Filesystem handlers for the standalone implementation
 */
static struct xvfs_tclfs_instance_info xvfs_tclfs_standalone_info;
static int xvfs_tclfs_standalone_pathInFilesystem(Tcl_Obj *path, ClientData *dataPtr) {
	return(xvfs_tclfs_pathInFilesystem(path, dataPtr, &xvfs_tclfs_standalone_info));
}

static int xvfs_tclfs_standalone_stat(Tcl_Obj *path, Tcl_StatBuf *statBuf) {
	return(xvfs_tclfs_stat(path, statBuf, &xvfs_tclfs_standalone_info));
}

static Tcl_Obj *xvfs_tclfs_standalone_listVolumes(void) {
	return(xvfs_tclfs_listVolumes(&xvfs_tclfs_standalone_info));
}

static Tcl_Channel xvfs_tclfs_standalone_openFileChannel(Tcl_Interp *interp, Tcl_Obj *path, int mode, int permissions) {
	return(xvfs_tclfs_openFileChannel(interp, path, mode, permissions, &xvfs_tclfs_standalone_info));
}

/*
 * There are three (3) modes of operation for Xvfs_Register:
 *    1. standalone -- We register our own Tcl_Filesystem
 *                     and handle requests under `//xvfs:/<fsName>`
 *    2. client -- A single Tcl_Filesystem is registered for the
 *                 interp to handle requests under `//xvfs:/` which
 *                 then dispatches to the appropriate registered
 *                 handler
 *    3. flexible -- Attempts to find a core Xvfs instance for the
 *                   process at runtime, if found do #2, otherwise
 *                   fallback to #1
 *
 */
static Tcl_Filesystem xvfs_tclfs_standalone_fs;
static int xvfs_standalone_register(Tcl_Interp *interp, struct Xvfs_FSInfo *fsInfo) {
	int tcl_ret;
	static int registered = 0;

	/*
	 * Ensure this instance is not already registered
	 */
	if (registered) {
		return(TCL_OK);
	}
	registered = 1;

	/*
	 * In standalone mode, we only support the same protocol we are
	 * compiling for.
	 */
	if (fsInfo->protocolVersion != XVFS_PROTOCOL_VERSION) {
		if (interp) {
			Tcl_SetResult(interp, "Protocol mismatch", NULL);
		}
		return(TCL_ERROR);
	}

	xvfs_tclfs_standalone_fs.typeName                   = "xvfs";
	xvfs_tclfs_standalone_fs.structureLength            = sizeof(xvfs_tclfs_standalone_fs);
	xvfs_tclfs_standalone_fs.version                    = TCL_FILESYSTEM_VERSION_1;
	xvfs_tclfs_standalone_fs.pathInFilesystemProc       = xvfs_tclfs_standalone_pathInFilesystem;
	xvfs_tclfs_standalone_fs.dupInternalRepProc         = NULL;
	xvfs_tclfs_standalone_fs.freeInternalRepProc        = NULL;
	xvfs_tclfs_standalone_fs.internalToNormalizedProc   = NULL;
	xvfs_tclfs_standalone_fs.createInternalRepProc      = NULL;
	xvfs_tclfs_standalone_fs.normalizePathProc          = NULL;
	xvfs_tclfs_standalone_fs.filesystemPathTypeProc     = NULL;
	xvfs_tclfs_standalone_fs.filesystemSeparatorProc    = NULL;
	xvfs_tclfs_standalone_fs.statProc                   = xvfs_tclfs_standalone_stat;
	xvfs_tclfs_standalone_fs.accessProc                 = NULL;
	xvfs_tclfs_standalone_fs.openFileChannelProc        = xvfs_tclfs_standalone_openFileChannel;
	xvfs_tclfs_standalone_fs.matchInDirectoryProc       = NULL; /* XXX:TODO */
	xvfs_tclfs_standalone_fs.utimeProc                  = NULL;
	xvfs_tclfs_standalone_fs.linkProc                   = NULL;
	xvfs_tclfs_standalone_fs.listVolumesProc            = xvfs_tclfs_standalone_listVolumes;
	xvfs_tclfs_standalone_fs.fileAttrStringsProc        = NULL;
	xvfs_tclfs_standalone_fs.fileAttrsGetProc           = NULL;
	xvfs_tclfs_standalone_fs.fileAttrsSetProc           = NULL;
	xvfs_tclfs_standalone_fs.createDirectoryProc        = NULL;
	xvfs_tclfs_standalone_fs.removeDirectoryProc        = NULL;
	xvfs_tclfs_standalone_fs.deleteFileProc             = NULL;
	xvfs_tclfs_standalone_fs.copyFileProc               = NULL;
	xvfs_tclfs_standalone_fs.renameFileProc             = NULL;
	xvfs_tclfs_standalone_fs.copyDirectoryProc          = NULL;
	xvfs_tclfs_standalone_fs.lstatProc                  = NULL;
	xvfs_tclfs_standalone_fs.loadFileProc               = NULL;
	xvfs_tclfs_standalone_fs.getCwdProc                 = NULL;
	xvfs_tclfs_standalone_fs.chdirProc                  = NULL;

	xvfs_tclfs_standalone_info.fsInfo = fsInfo;
	xvfs_tclfs_standalone_info.mountpoint = Tcl_NewObj();
	Tcl_AppendStringsToObj(xvfs_tclfs_standalone_info.mountpoint, XVFS_ROOT_MOUNTPOINT, fsInfo->name, NULL);

	tcl_ret = Tcl_FSRegister(NULL, &xvfs_tclfs_standalone_fs);
	if (tcl_ret != TCL_OK) {
		if (interp) {
			Tcl_SetResult(interp, "Tcl_FSRegister() failed", NULL);
		}

		return(tcl_ret);
	}

	xvfs_tclfs_prepareChannelType();

	return(TCL_OK);
}
#endif /* XVFS_MODE_STANDALONE || XVFS_MODE_FLEXIBLE */

#if defined(XVFS_MODE_FLEXIBLE)
static int xvfs_flexible_register(Tcl_Interp *interp, struct Xvfs_FSInfo *fsInfo) {
	ClientData fsHandlerDataRaw;
	struct xvfs_tclfs_server_info *fsHandlerData;
	const Tcl_Filesystem *fsHandler;
	int (*xvfs_register)(Tcl_Interp *interp, struct Xvfs_FSInfo *fsInfo);
	Tcl_Obj *rootPathObj;

	xvfs_register = &xvfs_standalone_register;

	rootPathObj = Tcl_NewStringObj(XVFS_ROOT_MOUNTPOINT, -1);
	if (!rootPathObj) {
		return(xvfs_register(interp, fsInfo));
	}

	Tcl_IncrRefCount(rootPathObj);
	fsHandler = Tcl_FSGetFileSystemForPath(rootPathObj);
	Tcl_DecrRefCount(rootPathObj);

	if (!fsHandler) {
		return(xvfs_register(interp, fsInfo));
	}

	fsHandlerDataRaw = Tcl_FSData(fsHandler);
	if (!fsHandlerDataRaw) {
		return(xvfs_register(interp, fsInfo));
	}

	fsHandlerData = (struct xvfs_tclfs_server_info *) fsHandlerDataRaw;

	/*
	 * XXX:TODO: What is the chance that the handler for //xvfs:/ hold
	 * client data smaller than XVFS_INTERNAL_SERVER_MAGIC_LEN ?
	 */
	if (memcmp(fsHandlerData->magic, XVFS_INTERNAL_SERVER_MAGIC, sizeof(fsHandlerData->magic)) == 0) {
		xvfs_register = fsHandlerData->registerProc;
	}

	return(xvfs_register(interp, fsInfo));
}
#endif /* XVFS_MODE_FLEXIBLE */

#if defined(XVFS_MODE_SERVER)
int Xvfs_Register(Tcl_Interp *interp, struct Xvfs_FSInfo *fsInfo) {
	return(TCL_ERROR);
}
#endif /* XVFS_MODE_SERVER */