Download the Tandler "Regenwasserbewirtschaftung" calculation engine

Fetches the Windows executable from the corresponding GitHub Release of the companion KWB-R/kwb.raindrop.binaries repository and caches it under a per-version sub-directory of the user cache. Subsequent calls are no-ops once the file is present.

Usage

download_engine(
  version = default_engine_version(),
  cache_dir = tools::R_user_dir("kwb.raindrop", "cache"),
  force = FALSE
)

Arguments

version: character(1) Engine release version, matching the part after engine- in the KWB-R/kwb.raindrop.binaries Release tag. Defaults to the package's pinned version.
cache_dir: character(1) Directory where engine binaries are cached. A sub-directory named after version is used so multiple versions can coexist. Defaults to tools::R_user_dir("kwb.raindrop", "cache").
force: logical(1) If TRUE, re-download even if the executable already exists in the cache. Default: FALSE.

Value

character(1) — absolute path to the cached .exe.

Details

Releases in KWB-R/kwb.raindrop.binaries follow the tag scheme engine-<version> and contain a single asset named Regenwasserbewirtschaftung.exe (the version is encoded in the tag, not in the filename, so multiple engine versions can coexist side-by-side in the cache).

The executable is a Windows binary; on non-Windows platforms the file is still downloaded but cannot be executed directly. The function does not validate the download with a checksum — pin a specific version to guarantee reproducibility.

Examples

if (FALSE) { # \dontrun{
exe <- download_engine()
exe <- download_engine("2026-02-24")
} # }