defmodule Mv.Membership.Member do
  @moduledoc """
  Ash resource representing a club member.

  ## Overview
  Members are the core entity in the membership management system. Each member
  can have:
  - Personal information (name, email, phone, address)
  - Optional link to a User account (1:1 relationship)
  - Dynamic custom field values via CustomField system
  - Full-text searchable profile

  ## Email Synchronization
  When a member is linked to a user account, emails are automatically synchronized
  bidirectionally. User.email is the source of truth on initial link.
  See `Mv.EmailSync` for details.

  ## Relationships
  - `has_many :custom_field_values` - Dynamic custom fields
  - `has_one :user` - Optional authentication account link

  ## Validations
  - Required: first_name, last_name, email
  - Email format validation (using EctoCommons.EmailValidator)
  - Phone number format: international format with 6-20 digits
  - Postal code format: exactly 5 digits (German format)
  - Date validations: birth_date and join_date not in future, exit_date after join_date
  - Email uniqueness: prevents conflicts with unlinked users

  ## Full-Text Search
  Members have a `search_vector` attribute (tsvector) that is automatically
  updated via database trigger. Search includes name, email, notes, and contact fields.
  """
  use Ash.Resource,
    domain: Mv.Membership,
    data_layer: AshPostgres.DataLayer

  require Ash.Query
  import Ash.Expr

  postgres do
    table "members"
    repo Mv.Repo
  end

  actions do
    defaults [:read, :destroy]

    create :create_member do
      primary? true
      # Custom field values can be created along with member
      argument :custom_field_values, {:array, :map}
      # Allow user to be passed as argument for relationship management
      # user_id is NOT in accept list to prevent direct foreign key manipulation
      argument :user, :map, allow_nil?: true

      accept [
        :first_name,
        :last_name,
        :email,
        :birth_date,
        :paid,
        :phone_number,
        :join_date,
        :exit_date,
        :notes,
        :city,
        :street,
        :house_number,
        :postal_code
      ]

      change manage_relationship(:custom_field_values, type: :create)

      # Manage the user relationship during member creation
      change manage_relationship(:user, :user,
               # Look up existing user and relate to it
               on_lookup: :relate,
               # Error if user doesn't exist in database
               on_no_match: :error,
               # Error if user is already linked to another member (prevents "stealing")
               on_match: :error,
               # If no user provided, that's fine (optional relationship)
               on_missing: :ignore
             )

      # Sync user email to member when linking (User → Member)
      # Only runs when user relationship is being changed
      change Mv.EmailSync.Changes.SyncUserEmailToMember do
        where [changing(:user)]
      end
    end

    update :update_member do
      primary? true
      # Required because custom validation function cannot be done atomically
      require_atomic? false
      # Custom field values can be updated or created along with member
      argument :custom_field_values, {:array, :map}
      # Allow user to be passed as argument for relationship management
      # user_id is NOT in accept list to prevent direct foreign key manipulation
      argument :user, :map, allow_nil?: true

      accept [
        :first_name,
        :last_name,
        :email,
        :birth_date,
        :paid,
        :phone_number,
        :join_date,
        :exit_date,
        :notes,
        :city,
        :street,
        :house_number,
        :postal_code
      ]

      change manage_relationship(:custom_field_values, on_match: :update, on_no_match: :create)

      # Manage the user relationship during member update
      change manage_relationship(:user, :user,
               # Look up existing user and relate to it
               on_lookup: :relate,
               # Error if user doesn't exist in database
               on_no_match: :error,
               # Error if user is already linked to another member (prevents "stealing")
               on_match: :error,
               # If no user provided, remove existing relationship (allows user removal)
               on_missing: :unrelate
             )

      # Sync member email to user when email changes (Member → User)
      # Only runs when email is being changed
      change Mv.EmailSync.Changes.SyncMemberEmailToUser do
        where [changing(:email)]
      end

      # Sync user email to member when linking (User → Member)
      # Only runs when user relationship is being changed
      change Mv.EmailSync.Changes.SyncUserEmailToMember do
        where [changing(:user)]
      end
    end

    # Action to handle fuzzy search on specific fields
    read :search do
      argument :query, :string, allow_nil?: true
      argument :similarity_threshold, :float, allow_nil?: true

      prepare fn query, _ctx ->
        q = Ash.Query.get_argument(query, :query) || ""

        # 0.2 as similarity threshold (recommended) - lower value can lead to more results but also to more unspecific results
        threshold = Ash.Query.get_argument(query, :similarity_threshold) || 0.2

        if is_binary(q) and String.trim(q) != "" do
          q2 = String.trim(q)
          pat = "%" <> q2 <> "%"

          # FTS as main filter and fuzzy search just for first name, last name and strees
          query
          |> Ash.Query.filter(
            expr(
              # Substring on numeric-like fields (best effort, supports middle substrings)
              fragment("search_vector @@ websearch_to_tsquery('simple', ?)", ^q2) or
                fragment("search_vector @@ plainto_tsquery('simple', ?)", ^q2) or
                contains(postal_code, ^q2) or
                contains(house_number, ^q2) or
                contains(phone_number, ^q2) or
                contains(email, ^q2) or
                contains(city, ^q2) or ilike(city, ^pat) or
                fragment("? % first_name", ^q2) or
                fragment("? % last_name", ^q2) or
                fragment("? % street", ^q2) or
                fragment("word_similarity(?, first_name) > ?", ^q2, ^threshold) or
                fragment("word_similarity(?, last_name) > ?", ^q2, ^threshold) or
                fragment("word_similarity(?, street) > ?", ^q2, ^threshold) or
                fragment("similarity(first_name, ?) > ?", ^q2, ^threshold) or
                fragment("similarity(last_name, ?) > ?", ^q2, ^threshold) or
                fragment("similarity(street, ?) > ?", ^q2, ^threshold)
            )
          )
        else
          query
        end
      end
    end
  end

  validations do
    # Required fields are covered by allow_nil? false

    # First name and last name must not be empty
    validate present(:first_name)
    validate present(:last_name)
    validate present(:email)

    # Email uniqueness check for all actions that change the email attribute
    # Validates that member email is not already used by another (unlinked) user
    validate Mv.Membership.Member.Validations.EmailNotUsedByOtherUser

    # Prevent linking to a user that already has a member
    # This validation prevents "stealing" users from other members by checking
    # if the target user is already linked to a different member
    # This is necessary because manage_relationship's on_match: :error only checks
    # if the user is already linked to THIS specific member, not ANY member
    validate fn changeset, _context ->
      user_arg = Ash.Changeset.get_argument(changeset, :user)

      if user_arg && user_arg[:id] do
        user_id = user_arg[:id]
        current_member_id = changeset.data.id

        # Check the current state of the user in the database
        case Ash.get(Mv.Accounts.User, user_id) do
          # User is free to be linked
          {:ok, %{member_id: nil}} ->
            :ok

          # User already linked to this member (update scenario)
          {:ok, %{member_id: ^current_member_id}} ->
            :ok

          {:ok, %{member_id: _other_member_id}} ->
            # User is linked to a different member - prevent "stealing"
            {:error, field: :user, message: "User is already linked to another member"}

          {:error, _} ->
            {:error, field: :user, message: "User not found"}
        end
      else
        :ok
      end
    end

    # Birth date not in the future
    validate compare(:birth_date, less_than_or_equal_to: &Date.utc_today/0),
      where: [present(:birth_date)],
      message: "cannot be in the future"

    # Join date not in the future
    validate compare(:join_date, less_than_or_equal_to: &Date.utc_today/0),
      where: [present(:join_date)],
      message: "cannot be in the future"

    # Exit date not before join date
    validate compare(:exit_date, greater_than: :join_date),
      where: [present([:join_date, :exit_date])],
      message: "cannot be before join date"

    # Phone number format (only if set)
    validate match(:phone_number, ~r/^\+?[0-9\- ]{6,20}$/),
      where: [present(:phone_number)],
      message: "is not a valid phone number"

    # Postal code format (only if set)
    validate match(:postal_code, ~r/^\d{5}$/),
      where: [present(:postal_code)],
      message: "must consist of 5 digits"

    # Email validation with EctoCommons.EmailValidator
    validate fn changeset, _ ->
      email = Ash.Changeset.get_attribute(changeset, :email)

      changeset2 =
        {%{}, %{email: :string}}
        |> Ecto.Changeset.cast(%{email: email}, [:email])
        |> EctoCommons.EmailValidator.validate_email(:email, checks: [:html_input, :pow])

      if changeset2.valid? do
        :ok
      else
        {:error, field: :email, message: "is not a valid email"}
      end
    end
  end

  attributes do
    uuid_v7_primary_key :id

    attribute :first_name, :string do
      allow_nil? false
      constraints min_length: 1
    end

    attribute :last_name, :string do
      allow_nil? false
      constraints min_length: 1
    end

    # IMPORTANT: Email Synchronization
    # When member and user are linked, emails are automatically synced bidirectionally.
    # User.email is the source of truth - when a link is established, member.email
    # is overridden to match user.email. Subsequent changes to either email will
    # sync to the other resource.
    # See: Mv.EmailSync.Changes.SyncUserEmailToMember
    #      Mv.EmailSync.Changes.SyncMemberEmailToUser
    attribute :email, :string do
      allow_nil? false
      constraints min_length: 5, max_length: 254
    end

    attribute :birth_date, :date do
      allow_nil? true
    end

    attribute :paid, :boolean do
      allow_nil? true
    end

    attribute :phone_number, :string do
      allow_nil? true
    end

    attribute :join_date, :date do
      allow_nil? true
    end

    attribute :exit_date, :date do
      allow_nil? true
    end

    attribute :notes, :string do
      allow_nil? true
    end

    attribute :city, :string do
      allow_nil? true
    end

    attribute :street, :string do
      allow_nil? true
    end

    attribute :house_number, :string do
      allow_nil? true
    end

    attribute :postal_code, :string do
      allow_nil? true
    end

    attribute :search_vector, AshPostgres.Tsvector,
      writable?: false,
      public?: false,
      select_by_default?: false
  end

  relationships do
    has_many :custom_field_values, Mv.Membership.CustomFieldValue
    # 1:1 relationship - Member can optionally have one User
    # This references the User's member_id attribute
    # The relationship is optional (allow_nil? true by default)
    has_one :user, Mv.Accounts.User
  end

  # Define identities for upsert operations
  identities do
    identity :unique_email, [:email]
  end

  # Fuzzy Search function that can be called by live view and calls search action
  def fuzzy_search(query, opts) do
    q = (opts[:query] || opts["query"] || "") |> to_string()

    if String.trim(q) == "" do
      query
    else
      args =
        case opts[:fields] || opts["fields"] do
          nil -> %{query: q}
          fields -> %{query: q, fields: fields}
        end

      Ash.Query.for_read(query, :search, args)
    end
  end
end