127 lines
3.2 KiB
Elixir
127 lines
3.2 KiB
Elixir
defmodule Mv.Membership.MemberGroup do
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@moduledoc """
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Ash resource representing the join table for the many-to-many relationship
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between Members and Groups.
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## Overview
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MemberGroup is a join table that links members to groups. It enables the
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many-to-many relationship where:
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- A member can belong to multiple groups
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- A group can contain multiple members
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## Attributes
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- `member_id` - Foreign key to Member (required)
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- `group_id` - Foreign key to Group (required)
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## Relationships
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- `belongs_to :member` - Relationship to Member
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- `belongs_to :group` - Relationship to Group
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## Constraints
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- Unique constraint on `(member_id, group_id)` - prevents duplicate memberships
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- CASCADE delete: Removing member removes all group associations
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- CASCADE delete: Removing group removes all member associations
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## Examples
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# Add member to group
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MemberGroup.create!(%{member_id: member.id, group_id: group.id})
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# Remove member from group
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member_group = MemberGroup.get_by_member_and_group!(member.id, group.id)
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MemberGroup.destroy!(member_group)
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"""
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use Ash.Resource,
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domain: Mv.Membership,
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data_layer: AshPostgres.DataLayer
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require Ash.Query
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postgres do
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table "member_groups"
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repo Mv.Repo
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end
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actions do
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defaults [:read, :destroy]
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create :create do
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accept [:member_id, :group_id]
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end
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end
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validations do
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validate present(:member_id)
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validate present(:group_id)
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# Prevent duplicate associations
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validate fn changeset, _context ->
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member_id = Ash.Changeset.get_attribute(changeset, :member_id)
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group_id = Ash.Changeset.get_attribute(changeset, :group_id)
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current_id = Ash.Changeset.get_attribute(changeset, :id)
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if member_id && group_id do
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check_duplicate_association(member_id, group_id, current_id)
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else
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:ok
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end
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end
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end
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attributes do
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uuid_v7_primary_key :id
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attribute :member_id, :uuid do
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allow_nil? false
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end
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attribute :group_id, :uuid do
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allow_nil? false
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end
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timestamps()
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end
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relationships do
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belongs_to :member, Mv.Membership.Member do
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allow_nil? false
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end
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belongs_to :group, Mv.Membership.Group do
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allow_nil? false
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end
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end
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identities do
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identity :unique_member_group, [:member_id, :group_id]
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end
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# Private helper function to check for duplicate associations
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defp check_duplicate_association(member_id, group_id, exclude_id) do
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alias Mv.Helpers
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alias Mv.Helpers.SystemActor
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query =
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Mv.Membership.MemberGroup
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|> Ash.Query.filter(member_id == ^member_id and group_id == ^group_id)
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|> maybe_exclude_id(exclude_id)
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system_actor = SystemActor.get_system_actor()
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opts = Helpers.ash_actor_opts(system_actor)
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case Ash.read(query, opts) do
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{:ok, []} ->
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:ok
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{:ok, _} ->
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{:error, field: :member_id, message: "Member is already in this group", value: member_id}
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{:error, _reason} ->
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# Fail-open: if query fails, allow operation to proceed
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# Database constraint will catch duplicates anyway
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:ok
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end
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end
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defp maybe_exclude_id(query, nil), do: query
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defp maybe_exclude_id(query, id), do: Ash.Query.filter(query, id != ^id)
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end
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