# frozen_string_literal: true

# Shared value validation and frozen editor-owned configuration objects.
module Vamp
  MAX_FRAME = 4 * 1024 * 1024

  # Validates a boundary value and returns a UTF-8 copy.
  # @param value [Object]
  # @param label [String]
  # @return [String]
  def self.string!(value, label)
    raise TypeError, "#{label} must be a String" unless value.is_a?(String)

    copy = value.dup.force_encoding(Encoding::UTF_8)
    raise ArgumentError, "#{label} must be valid UTF-8" unless copy.valid_encoding?

    copy
  end

  # Recursively validates JSON values and normalizes hash keys to strings.
  # @param value [Object]
  # @return [Hash{String => Object}, Array<Object>, String, Integer, Float, Boolean, nil]
  def self.json_value!(value)
    case value
    when Hash
      json_hash(value)
    when Array
      value.map { |item| json_value!(item) }
    else
      json_scalar(value)
    end
  end

  # Freezes the supplied value and every nested hash/array member in place.
  # @param value [Object]
  # @return [Object] the same value
  def self.deep_freeze(value)
    case value
    when Hash
      value.each do |key, item|
        deep_freeze(key)
        deep_freeze(item)
      end
    when Array
      value.each { |item| deep_freeze(item) }
    end
    value.freeze
  end

  # @!override Vamp::Action#name
  #   @return [String] the catalog's dotted action name
  Action = Struct.new(:name)
  # @!override Vamp::Mode#name
  #   @return [String] the lowercase binding mode
  Mode = Struct.new(:name)

  # Action methods and nested modules come exclusively from the Rust catalog.
  # @type [Module<Vamp::Core>]
  Core = Module.new

  # @param names [Array<String>] dotted core action names
  # @return [Array<Module>] frozen action namespaces
  def self.install_actions(names)
    raise TypeError, "core action catalog must be an Array" unless names.is_a?(Array)

    namespaces = [Core]
    names.each { |name| install_action(name, namespaces) }
    namespaces.each(&:freeze)
  end

  # Frozen binding mode values, distinct from a buffer's editing state.
  module Modes
    # @!method self.normal
    #   @return [Vamp::Mode]
    # @!method self.insert
    #   @return [Vamp::Mode]
    # @!method self.command
    #   @return [Vamp::Mode]
    # @!method self.search
    #   @return [Vamp::Mode]
    # @!method self.visual
    #   @return [Vamp::Mode]
    # @!method self.selection
    #   @return [Vamp::Mode]
    # @!method self.tree
    #   @return [Vamp::Mode]
    %w[normal insert command search visual selection tree].each do |name|
      mode = Mode.new(name.freeze).freeze
      define_singleton_method(name) { mode }
    end
  end

  Action.private_class_method :new
  Mode.private_class_method :new

  # @param value [Hash{String, Symbol => Object}]
  # @return [Hash{String => Object}]
  def self.json_hash(value)
    value.to_h do |key, item|
      raise TypeError, "option keys must be Strings or Symbols" unless key.is_a?(String) || key.is_a?(Symbol)

      [string!(key.to_s, "option key"), json_value!(item)]
    end
  end

  # @param value [Object]
  # @return [String, Integer, Float, Boolean, nil]
  def self.json_scalar(value)
    case value
    when String
      string!(value, "option value")
    when Integer, TrueClass, FalseClass, NilClass, Float
      json_literal(value)
    else
      raise TypeError, "options must contain only JSON values"
    end
  end

  # @param value [Integer, Float, Boolean, nil]
  # @return [Integer, Float, Boolean, nil]
  def self.json_literal(value)
    raise ArgumentError, "option numbers must be finite" if value.is_a?(Float) && !value.finite?

    value
  end

  # @param name [String]
  # @param namespaces [Array<Module>]
  # @return [Symbol] the installed action method name
  def self.install_action(name, namespaces)
    name = action_name(name)
    parts = name.split(".").drop(1)
    namespace = parts[0...-1].reduce(Core) { |parent, part| action_namespace(parent, part, namespaces, name) }
    leaf = parts.last
    available_action!(namespace, leaf, name)
    action = Action.send(:new, name.freeze).freeze
    namespace.define_singleton_method(leaf) { action }
  end

  # @param name [Object]
  # @return [String]
  def self.action_name(name)
    name = string!(name, "core action name")
    raise ArgumentError, "invalid core action name: #{name}" unless name.match?(/\Acore(?:\.[a-z_][a-z0-9_]*)+\z/)

    name
  end

  # @param parent [Module]
  # @param part [String]
  # @param namespaces [Array<Module>]
  # @param name [String]
  # @return [Module]
  def self.action_namespace(parent, part, namespaces, name)
    return new_action_namespace(parent, part, namespaces) unless parent.singleton_methods(false).include?(part.to_sym)

    child = parent.public_send(part)
    raise ArgumentError, "conflicting core action namespace: #{name}" unless child.is_a?(Module)

    child
  end

  # @param parent [Module]
  # @param part [String]
  # @param namespaces [Array<Module>]
  # @return [Module]
  def self.new_action_namespace(parent, part, namespaces)
    child = Module.new
    parent.define_singleton_method(part) { child }
    namespaces << child
    child
  end

  # @param namespace [Module]
  # @param leaf [String]
  # @param name [String]
  # @return [nil]
  def self.available_action!(namespace, leaf, name)
    return unless namespace.singleton_methods(false).include?(leaf.to_sym)

    raise ArgumentError, "conflicting core action name: #{name}"
  end

  private_class_method :json_hash, :json_scalar, :json_literal, :install_action, :action_name,
                       :action_namespace, :new_action_namespace, :available_action!
end