#[===[
# vcpkg_host_path_list

Modify a host path list variable (PATH, INCLUDE, LIBPATH, etc.)

```cmake
vcpkg_host_path_list(PREPEND <list-var> [<path>...])
vcpkg_host_path_list(APPEND <list-var> [<path>...])
vcpkg_host_path_list(SET <list-var> [<path>...])
```

`<list-var>` may be either a regular variable name, or `ENV{variable-name}`,
in which case `vcpkg_host_path_list` will modify the environment.

`vcpkg_host_path_list` adds all of the paths passed to it to `<list-var>`;
`PREPEND` puts them before the existing list, so that they are searched first;
`APPEND` places them after the existing list,
so they would be searched after the paths which are already in the variable,
and `SET` replaces the value of the existing list.

For all of `APPEND`, `PREPEND`, and `SET`,
the paths are added (and thus searched) in the order received.

If no paths are passed to `APPEND` or `PREPEND`, nothing will be done;
for `SET`, the variable will be set to the empty string.
#]===]

function(z_vcpkg_translate_to_host_path_list out_var lst)
    if(NOT DEFINED arg_UNPARSED_ARGUMENTS)
        set("${out_var}" "" PARENT_SCOPE)
    else()
        if("${VCPKG_HOST_PATH_SEPARATOR}" STREQUAL ";")
            set("${out_var}" "${lst}" PARENT_SCOPE)

            string(FIND "${lst}" [[\;]] index_of_host_path_separator)
        else()
            vcpkg_list(JOIN lst "${VCPKG_HOST_PATH_SEPARATOR}" arguments)
            set("${out_var}" "${arguments}" PARENT_SCOPE)

            string(FIND "${lst}" "${VCPKG_HOST_PATH_SEPARATOR}" index_of_host_path_separator)
        endif()
        if(NOT "${index_of_host_path_separator}" EQUAL "-1")
            message(FATAL_ERROR "Host path separator (${VCPKG_HOST_PATH_SEPARATOR}) in path; this is unsupported.")
        endif()
    endif()
endfunction()

function(vcpkg_host_path_list)
    if("${ARGC}" LESS "2")
        message(FATAL_ERROR "vcpkg_host_path_list requires at least two arguments.")
    endif()

    if("${ARGV1}" MATCHES "^ARGV([0-9]*)$|^ARG[CN]$|^CMAKE_CURRENT_FUNCTION|^CMAKE_MATCH_")
        message(FATAL_ERROR "vcpkg_host_path_list does not support the list_var being ${ARGV1}.
    Please use a different variable name.")
    endif()

    if("${ARGV1}" MATCHES [[^ENV\{(.*)\}$]])
        set(list "$ENV{${CMAKE_MATCH_1}}")
        set(env_var ON)
    elseif("${ARGV1}" MATCHES [[^([A-Z]+)\{.*\}$]])
        message(FATAL_ERROR "vcpkg_host_path_list does not support ${CMAKE_MATCH_1} variables;
    only ENV{} and regular variables are supported.")
    else()
        set(list "${${ARGV1}}")
        set(env_var OFF)
    endif()
    set(operation "${ARGV0}")
    set(list_var "${ARGV1}")

    cmake_parse_arguments(PARSE_ARGV 2 arg "" "" "")
    z_vcpkg_translate_to_host_path_list(arguments "${arg_UNPARSED_ARGUMENTS}")

    if("${operation}" STREQUAL "SET")
        set(list "${arguments}")
    elseif("${operation}" MATCHES "^(APPEND|PREPEND)$")
        if("${arguments}" STREQUAL "")
            # do nothing
        elseif("${list}" STREQUAL "")
            set(list "${arguments}")
        elseif(arg_PREPEND)
            set(list "${arguments}${VCPKG_HOST_PATH_SEPARATOR}${list}")
        else()
            set(list "${list}${VCPKG_HOST_PATH_SEPARATOR}${arguments}")
        endif()
    else()
        message(FATAL_ERROR "Operation ${operation} not recognized.")
    endif()

    if(env_var)
        set("${list_var}" "${list}")
    else()
        set("${list_var}" "${list}" PARENT_SCOPE)
    endif()
endfunction()