/**************************************************************/
/*  tpax: a topological pax implementation                    */
/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
/*  Released under GPLv2 and GPLv3; see COPYING.TPAX.         */
/**************************************************************/

#include <stdint.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>

#include <tpax/tpax.h>
#include "tpax_driver_impl.h"
#include "tpax_errinfo_impl.h"
#include "tpax_readlink_impl.h"

static int tpax_free_unit_ctx_impl(struct tpax_unit_ctx_impl * ctx, int ret)
{
	if (ctx) {
		if (ctx->pathbuf)
			free(ctx->pathbuf);

		free(ctx);
	}

	return ret;
}

int tpax_lib_get_unit_ctx(
	const struct tpax_driver_ctx *	dctx,
	int				fdat,
	const char *			path,
	struct tpax_unit_ctx **		pctx)
{
	int				ret;
	struct tpax_unit_ctx_impl *	ctx;
	size_t                          pathlen;

	if (!dctx)
		return TPAX_CUSTOM_ERROR(
			dctx,TPAX_ERR_NULL_CONTEXT);

	else if (!(ctx = calloc(1,sizeof(*ctx))))
		return TPAX_BUFFER_ERROR(dctx);

	tpax_driver_set_ectx(
		dctx,0,path);

	if (dctx->cctx->drvflags & TPAX_DRIVER_EXEC_MODE_WRITE_COPY) {
		ret = fstatat(
			fdat,path,&ctx->st,
			AT_SYMLINK_NOFOLLOW);

		if (ret < 0) {
			free(ctx);
			return TPAX_SYSTEM_ERROR(dctx);
		}
	}

	if (S_ISLNK(ctx->st.st_mode)) {
		if (tpax_readlinkat(
				fdat,path,ctx->linkbuf,
				sizeof(ctx->linkbuf)) < 0) {
			free(ctx);
			return TPAX_SYSTEM_ERROR(dctx);
		}
	}

	if (dctx->cctx->drvflags & TPAX_DRIVER_PURE_PATH_OUTPUT) {
		if (!(pathlen = strlen(path)))
			return TPAX_CUSTOM_ERROR(
				dctx,
				TPAX_ERR_FORBIDDEN_PATH);

		if (!(ctx->pathbuf = calloc(1,++pathlen)))
			return TPAX_BUFFER_ERROR(dctx);

		ret = tpax_util_path_copy(
			ctx->pathbuf,path,pathlen,
			dctx->cctx->drvflags,
			&pathlen);

		if (ret < 0)
			return TPAX_CUSTOM_ERROR(
				dctx,
				TPAX_ERR_FLOW_ERROR);

		ctx->path    = ctx->pathbuf;
		ctx->patharg = path;
	} else {
		ctx->path    = path;
		ctx->patharg = path;
		ctx->pathbuf = 0;
	}

	ctx->link	= ctx->linkbuf[0] ? ctx->linkbuf : 0;

	ctx->uctx.path	= &ctx->path;
	ctx->uctx.link	= &ctx->link;
	ctx->uctx.st	= &ctx->st;

	*pctx = &ctx->uctx;

	return 0;
}

void tpax_lib_free_unit_ctx(struct tpax_unit_ctx * ctx)
{
	struct tpax_unit_ctx_impl *	ictx;
	uintptr_t			addr;

	if (ctx) {
		addr = (uintptr_t)ctx - offsetof(struct tpax_unit_ctx_impl,uctx);
		ictx = (struct tpax_unit_ctx_impl *)addr;
		tpax_free_unit_ctx_impl(ictx,0);
	}
}