# `MishkaCmsMigration.Targets.Helpers.LanguageUrls`
[🔗](https://github.com/mishka-group/mishka_cms_migration/blob/v0.0.1/lib/mishka_cms_migration/targets/__helpers/language_urls.ex#L5)

Whether the links an import writes may not match the site's addresses, for the targets that write
links (`MishkaCmsMigration.Targets.CmsLayout`).

A link is written as a fixed address in the way the run's site names the language in its
addresses at that moment (`MishkaCmsCore.Runtime.Languages.url/3`, the site's `site.language_urls`
setting). It does not follow the source's addresses when the source names the language in them,
nor the site when an admin later changes how it names it. `cause/2` tells when that can happen:

  * `"polylang"` or `"wpml"` — the source runs that language plugin
    (`MishkaCmsMigration.Sources.WordPress`'s `extra/1` keeps it as `"languages"`), so its
    addresses carry a language prefix, such as `/fa/about/`;
  * `"prefix_all"` — the site gives every language a prefix, so the links are written with
    `/en/…` and an unprefixed source address is not the address they point at.

A Run again writes such links again after an admin changes the site's `Language in addresses`:
`hash/2` is the item's hash with that mode added for an item that writes links, so the item is
no longer `"unchanged"`. Links are rewritten for the new mode, unless the record was changed in
the CMS since, which keeps it as it is. The menu's links stay fixed addresses: the core's
navigation (`MishkaCmsCore.Install.StarterContent.nav_links/1`) can draw a path in the page's own
language (`site_path/2`), but has no form for a link to one language's edition.

The plugin is named first when both hold; a site that does not prefix its first language, with a
source that runs no language plugin, has no cause.

`call/2` makes a target that writes links wait for an admin's decision on such a run, as
`"language_urls: <cause>"` (`MishkaCmsMigration.MigrationItem`'s Decide…): Write links for the
site's current mode (`"import"`) goes on, and Wait (`"keep"`) skips the item as
`"waits_for_language_urls"` until the admin has set up the site's languages, then decided.

# `call`

```elixir
@spec call(MishkaCmsMigration.Source.Item.t(), MishkaCmsMigration.Target.context()) ::
  :ok | {:skipped, String.t()} | {:undecided, String.t()}
```

`:ok` for an item whose links need no decision, or one an admin decided to write for the site's
current mode, `{:skipped, "waits_for_language_urls"}` for one an admin decided to wait with, and
`{:undecided, "language_urls: <cause>"}` while no admin has decided.

# `cause`

```elixir
@spec cause(String.t() | nil, String.t()) :: String.t() | nil
```

What makes links written now differ from the source's, or `nil`. `languages` is the source's
language plugin, `nil` for none.

# `hash`

```elixir
@spec hash(MishkaCmsMigration.Source.Item.t(), String.t()) :: String.t()
```

`MishkaCmsMigration.Source.Item.hash/1`, with the site's language address mode added for an item
that writes links: a menu, and a page or post whose content links to pages or posts of the
source. Links are written as fixed addresses in that mode, so when the site's `Language in
addresses` changes, such an item no longer matches what was recorded, and a Run again writes its
links again (unless an admin changed it in the CMS since, which keeps it). Any other item hashes
as it always did.

---

*Consult [api-reference.md](api-reference.md) for complete listing*