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: 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

  # Module constants
  @member_search_limit 10
  @default_similarity_threshold 0.2

  # Use constants from Mv.Constants for member fields
  # This ensures consistency across the codebase
  @member_fields Mv.Constants.member_fields()

  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 @member_fields

      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 @member_fields

      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) || ""

        # Use default similarity threshold if not provided
        # Lower value leads to more results but also more unspecific results
        threshold =
          Ash.Query.get_argument(query, :similarity_threshold) || @default_similarity_threshold

        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

    # Action to find members available for linking to a user account
    # Returns only unlinked members (user_id == nil), limited to 10 results
    #
    # Filtering behavior:
    # - If search_query provided: fuzzy search on names and email
    # - If no search_query: return all unlinked members (up to limit)
    # - user_email should be handled by caller with filter_by_email_match/2
    read :available_for_linking do
      argument :user_email, :string, allow_nil?: true
      argument :search_query, :string, allow_nil?: true

      prepare fn query, _ctx ->
        user_email = Ash.Query.get_argument(query, :user_email)
        search_query = Ash.Query.get_argument(query, :search_query)

        query
        |> Ash.Query.filter(is_nil(user))
        |> apply_linking_filters(user_email, search_query)
        |> Ash.Query.limit(@member_search_limit)
      end
    end
  end

  @doc """
  Filters members list based on email match priority.

  Priority logic:
  1. If email matches a member: return ONLY that member (highest priority)
  2. If email doesn't match: return all members (for display in dropdown)

  This is used with :available_for_linking action to implement email-priority behavior:
  - user_email matches → Only this member
  - user_email does NOT match + NO search_query → All unlinked members
  - user_email does NOT match + search_query provided → search_query filtered members

  ## Parameters
    - `members` - List of Member structs (from :available_for_linking action)
    - `user_email` - Email string to match against member emails

  ## Returns
    - List of Member structs (either single email match or all members)

  ## Examples

      iex> members = [%Member{email: "test@example.com"}, %Member{email: "other@example.com"}]
      iex> filter_by_email_match(members, "test@example.com")
      [%Member{email: "test@example.com"}]

      iex> filter_by_email_match(members, "nomatch@example.com")
      [%Member{email: "test@example.com"}, %Member{email: "other@example.com"}]
  """
  @spec filter_by_email_match([t()], String.t()) :: [t()]
  def filter_by_email_match(members, user_email)
      when is_list(members) and is_binary(user_email) do
    email_match = Enum.find(members, &(&1.email == user_email))

    if email_match do
      # Email match found - return only this member (highest priority)
      [email_match]
    else
      # No email match - return all members unchanged
      members
    end
  end

  @spec filter_by_email_match(any(), any()) :: any()
  def filter_by_email_match(members, _user_email), do: members

  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

    # 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 :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

  @doc """
  Checks if a member field should be shown in the overview.

  Reads the visibility configuration from Settings resource. If a field is not
  configured in settings, it defaults to `true` (visible).

  ## Parameters
    - `field` - Atom representing the member field name (e.g., `:email`, `:street`)

  ## Returns
    - `true` if the field should be shown in overview (default)
    - `false` if the field is configured as hidden in settings

  ## Examples

      iex> Member.show_in_overview?(:email)
      true

      iex> Member.show_in_overview?(:street)
      true  # or false if configured in settings

  """
  @spec show_in_overview?(atom()) :: boolean()
  def show_in_overview?(field) when is_atom(field) do
    case Mv.Membership.get_settings() do
      {:ok, settings} ->
        visibility_config = settings.member_field_visibility || %{}
        # Normalize map keys to atoms (JSONB may return string keys)
        normalized_config = normalize_visibility_config(visibility_config)

        # Get value from normalized config, default to true
        Map.get(normalized_config, field, true)

      {:error, _} ->
        # If settings can't be loaded, default to visible
        true
    end
  end

  def show_in_overview?(_), do: true

  # Normalizes visibility config map keys from strings to atoms.
  # JSONB in PostgreSQL converts atom keys to string keys when storing.
  defp normalize_visibility_config(config) when is_map(config) do
    Enum.reduce(config, %{}, fn
      {key, value}, acc when is_atom(key) ->
        Map.put(acc, key, value)

      {key, value}, acc when is_binary(key) ->
        try do
          atom_key = String.to_existing_atom(key)
          Map.put(acc, atom_key, value)
        rescue
          ArgumentError ->
            acc
        end

      _, acc ->
        acc
    end)
  end

  defp normalize_visibility_config(_), do: %{}

  @doc """
  Performs fuzzy search on members using PostgreSQL trigram similarity.

  Wraps the `:search` action with convenient opts-based argument passing.
  Searches across first_name, last_name, email, and other text fields using
  full-text search combined with trigram similarity.

  ## Parameters
    - `query` - Ash.Query.t() to apply search to
    - `opts` - Keyword list or map with search options:
      - `:query` or `"query"` - Search string
      - `:fields` or `"fields"` - Optional field restrictions

  ## Returns
    - Modified Ash.Query.t() with search filters applied

  ## Examples

      iex> Member |> fuzzy_search(%{query: "Greta"}) |> Ash.read!()
      [%Member{first_name: "Greta", ...}]

      iex> Member |> fuzzy_search(%{query: "gre"}) |> Ash.read!()  # typo-tolerant
      [%Member{first_name: "Greta", ...}]

  """
  @spec fuzzy_search(Ash.Query.t(), keyword() | map()) :: Ash.Query.t()
  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

  # Private helper to apply filters for :available_for_linking action
  # user_email: may be nil/empty when creating new user, or populated when editing
  # search_query: optional search term for fuzzy matching
  #
  # Logic: (email == user_email) OR (fuzzy_search on search_query)
  # - Empty user_email ("") → email == "" is always false → only fuzzy search matches
  # - This allows a single filter expression instead of duplicating fuzzy search logic
  #
  # Cyclomatic complexity is unavoidable here: PostgreSQL fuzzy search requires
  # multiple OR conditions for good search quality (FTS + trigram similarity + substring)
  # credo:disable-for-next-line Credo.Check.Refactor.CyclomaticComplexity
  defp apply_linking_filters(query, user_email, search_query) do
    has_search = search_query && String.trim(search_query) != ""
    # Use empty string instead of nil to simplify filter logic
    trimmed_email = if user_email, do: String.trim(user_email), else: ""

    if has_search do
      # Search query provided: return email-match OR fuzzy-search candidates
      trimmed_search = String.trim(search_query)

      query
      |> Ash.Query.filter(
        expr(
          # Email match candidate (for filter_by_email_match priority)
          # If email is "", this is always false and fuzzy search takes over
          # Fuzzy search candidates
          email == ^trimmed_email or
            fragment("search_vector @@ websearch_to_tsquery('simple', ?)", ^trimmed_search) or
            fragment("search_vector @@ plainto_tsquery('simple', ?)", ^trimmed_search) or
            fragment("? % first_name", ^trimmed_search) or
            fragment("? % last_name", ^trimmed_search) or
            fragment("word_similarity(?, first_name) > 0.2", ^trimmed_search) or
            fragment(
              "word_similarity(?, last_name) > ?",
              ^trimmed_search,
              ^@default_similarity_threshold
            ) or
            fragment(
              "similarity(first_name, ?) > ?",
              ^trimmed_search,
              ^@default_similarity_threshold
            ) or
            fragment(
              "similarity(last_name, ?) > ?",
              ^trimmed_search,
              ^@default_similarity_threshold
            ) or
            contains(email, ^trimmed_search)
        )
      )
    else
      # No search query: return all unlinked (filter_by_email_match will prioritize email if provided)
      query
    end
  end
end