147 lines
4 KiB
Elixir
147 lines
4 KiB
Elixir
defmodule Mv.Membership.Changes.GenerateSlug do
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@moduledoc """
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Ash Change that automatically generates a URL-friendly slug from the `name` attribute.
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## Behavior
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- **On Create**: Generates a slug from the name attribute using slugify
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- **On Update**: Slug remains unchanged (immutable after creation)
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- **Slug Generation**: Uses the `slugify` library to convert name to slug
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- Converts to lowercase
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- Replaces spaces with hyphens
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- Removes special characters
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- Handles UTF-8 characters (e.g., ä → a, ß → ss)
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- Trims leading/trailing hyphens
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- Truncates to max 100 characters
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## Usage
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Works for any resource with `name` and `slug` attributes.
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Used by CustomField and Group resources.
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create :create do
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accept [:name, :description]
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change Mv.Membership.Changes.GenerateSlug
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validate string_length(:slug, min: 1)
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end
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## Examples
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# Create with automatic slug generation
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CustomField.create!(%{name: "Mobile Phone"})
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# => %CustomField{name: "Mobile Phone", slug: "mobile-phone"}
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Group.create!(%{name: "Test Group"})
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# => %Group{name: "Test Group", slug: "test-group"}
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# German umlauts are converted
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CustomField.create!(%{name: "Café Müller"})
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# => %CustomField{name: "Café Müller", slug: "cafe-muller"}
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# Slug is immutable on update
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custom_field = CustomField.create!(%{name: "Original"})
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CustomField.update!(custom_field, %{name: "New Name"})
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# => %CustomField{name: "New Name", slug: "original"} # slug unchanged!
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## Implementation Note
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This change only runs on `:create` actions. The slug is immutable by design,
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as changing slugs would break external references (e.g., CSV imports/exports, URL routes).
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"""
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use Ash.Resource.Change
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@doc """
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Generates a slug from the changeset's `name` attribute.
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Only runs on create actions. Returns the changeset unchanged if:
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- The action is not :create
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- The name is not being changed
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- The name is nil or empty
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## Parameters
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- `changeset` - The Ash changeset
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- `_opts` - Options passed to the change (unused)
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- `_context` - Ash context map (unused)
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## Returns
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The changeset with the `:slug` attribute set to the generated slug.
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"""
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@impl true
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def change(changeset, _opts, _context) do
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# Only generate slug on create, not on update (immutability)
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if changeset.action_type == :create do
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case Ash.Changeset.get_attribute(changeset, :name) do
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nil ->
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changeset
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name when is_binary(name) ->
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slug = generate_slug(name)
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Ash.Changeset.force_change_attribute(changeset, :slug, slug)
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_ ->
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changeset
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end
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else
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# On update, don't touch the slug (immutable)
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changeset
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end
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end
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@doc """
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Generates a URL-friendly slug from a given string.
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Uses the `slugify` library to create a clean, lowercase slug with:
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- Spaces replaced by hyphens
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- Special characters removed
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- UTF-8 characters transliterated (ä → a, ß → ss, etc.)
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- Multiple consecutive hyphens reduced to single hyphen
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- Leading/trailing hyphens removed
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- Maximum length of 100 characters
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## Parameters
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- `name` - The string to convert to a slug
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## Returns
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A URL-friendly slug string, or empty string if input is invalid.
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## Examples
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iex> generate_slug("Mobile Phone")
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"mobile-phone"
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iex> generate_slug("Café Müller")
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"cafe-muller"
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iex> generate_slug("TEST NAME")
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"test-name"
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iex> generate_slug("E-Mail & Address!")
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"e-mail-address"
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iex> generate_slug("Multiple Spaces")
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"multiple-spaces"
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iex> generate_slug("-Test-")
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"test"
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iex> generate_slug("Straße")
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"strasse"
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"""
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@spec generate_slug(String.t()) :: String.t()
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def generate_slug(name) when is_binary(name) do
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slug = Slug.slugify(name)
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case slug do
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nil -> ""
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"" -> ""
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slug when is_binary(slug) -> String.slice(slug, 0, 100)
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end
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end
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def generate_slug(_), do: ""
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end
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