{%- macro files_switch(
      source_files,
      config,
      lookup=none,
      default_files_switch=["id", "os_family"],
      indent_width=6,
      use_subpath=false,
      json=false
    ) %}
{#-
    Renders a list of `salt://` URI for the `source` parameter of a `file.managed`
    state function. This helps with applying the Template Override and
    Files Switch (TOFS) pattern.

    Based on `libtofs.jinja`, but homogenized with how `libmapstack` works:

    * Instead of calling `config.get` for configuration parameters to this macro,
      the configuration is passed in by the caller. This allows setting
      the values together with the other parameters for `libmapstack.jinja`
      instead of (unexpectedly) relying on pillar/grains/opts only.

    * Like the `parameters` for `libmapstack`, the name of the switch is prepended
      to its value. Hence for a Debian minion named `db` with `["id", "os_family"]`, the
      paths would be:
        - <path_prefix>/files/id/db (instead of `<path_prefix>/files/db`)
        - <path_prefix>/files/os_family/Debian (instead of `<path_prefix>/files/Debian`)
        - <path_prefix>/files/default

    source_files
        Ordered list of files to check for.

    config
        Externally merged configuration dict, usually the imported value of `map.jinja`.

    lookup
        Key under `tofs:source_files` to prepend to the list of source files.

    default_files_switch
        If `tofs:files_switch` is unset, this is the ordered list of
        parameters to `config.get` to use as selector switch of the directories under
        `<path_prefix>/files`.

    indent_width
        Indentation of the result value to conform to YAML.

    use_subpath
        Lookup the source file recursively from the including
        state's directory up to `tplroot`. Defaults to false.
#}
{%-   set tplroot = tpldir.split("/")[0] %}
{%-   set path_prefix = config | traverse("tofs:path_prefix", tplroot) %}
{%-   set files_dir = config | traverse("tofs:dirs:files", "files") %}
{%-   set files_switch_list = config | traverse("tofs:files_switch", default_files_switch) %}
{#-   Lookup source_files (v2), files (v1), or fallback to an empty list #}
{%-   set src_files = config | traverse("tofs:source_files:" ~ lookup, config | traverse("tofs:files:" ~ lookup, [])) %}
{#-   Append the default source_files #}
{%-   set src_files = src_files + source_files %}
{#-   Only add to [""] when supporting older TOFS implementations #}
{%-   set path_prefix_exts = [""] %}
{%-   if use_subpath and tplroot != tpldir %}
{#-     Walk directory tree to find {{ files_dir }} #}
{%-     set subpath_parts = tpldir.lstrip(tplroot).lstrip("/").split("/") %}
{%-     for path in subpath_parts %}
{%-       set subpath = subpath_parts[0 : loop.index] | join("/") %}
{%-       do path_prefix_exts.append("/" ~ subpath) %}
{%-     endfor %}
{%-   endif %}
{%-   for path_prefix_ext in path_prefix_exts | reverse %}
{%-     set path_prefix_inc_ext = path_prefix ~ path_prefix_ext %}
{#-     For older TOFS implementation, use `files_switch` from the config #}
{#-     Use the default, new method otherwise #}
{%-     set fsl = config | traverse(path_prefix_ext | replace("/", ":") ~ ":files_switch", files_switch_list) %}
{#-     Append an empty value to evaluate as `default` in the loop below #}
{%-     if "" not in fsl %}
{%-       set fsl = fsl + [""] %}
{%-     endif %}
{%-     for fs in fsl %}
{%-       for src_file in src_files %}
{%-         if fs %}
{%-           set fs_dirs = salt["config.get"](fs, fs) %}
{%-         else %}
{%-           set fs_dirs = config | traverse("tofs:dirs:default", "default") %}
{%-         endif %}
{#-         Force the `config.get` lookup result as a list where necessary #}
{#-         since we need to also handle grains that are lists #}
{%-         if fs_dirs is string %}
{%-           set fs_dirs = [fs_dirs] %}
{%-         endif %}
{%-         for fs_dir in fs_dirs %}
{#-           strip empty elements by using a select #}
{%-           set url = (
                [
                  "- salt:/",
                  path_prefix_inc_ext.strip("/"),
                  files_dir.strip("/"),
                  fs,
                  fs_dir.strip("/"),
                  src_file.strip("/"),
                ]
                | select
                | join("/")
              ) %}
{{ url | indent(indent_width, true) }}
{%-         endfor %}
{%-       endfor %}
{%-     endfor %}
{%-   endfor %}
{%- endmacro %}