# typed: strict
# frozen_string_literal: true

module RubyLsp
  module Requests
    # ![Code action resolve demo](../../code_action_resolve.gif)
    #
    # The [code action resolve](https://microsoft.github.io/language-server-protocol/specification#codeAction_resolve)
    # request is used to to resolve the edit field for a given code action, if it is not already provided in the
    # textDocument/codeAction response. We can use it for scenarios that require more computation such as refactoring.
    #
    # # Example: Extract to variable
    #
    # ```ruby
    # # Before:
    # 1 + 1 # Select the text and use Refactor: Extract Variable
    #
    # # After:
    # new_variable = 1 + 1
    # new_variable
    #
    # ```
    #
    class CodeActionResolve < Request
      extend T::Sig
      NEW_VARIABLE_NAME = "new_variable"

      class CodeActionError < StandardError; end

      class Error < ::T::Enum
        enums do
          EmptySelection = new
          InvalidTargetRange = new
        end
      end

      sig { params(document: Document, code_action: T::Hash[Symbol, T.untyped]).void }
      def initialize(document, code_action)
        super()
        @document = document
        @code_action = code_action
      end

      sig { override.returns(T.any(Interface::CodeAction, Error)) }
      def perform
        return Error::EmptySelection if @document.source.empty?

        source_range = @code_action.dig(:data, :range)
        return Error::EmptySelection if source_range[:start] == source_range[:end]

        scanner = @document.create_scanner
        start_index = scanner.find_char_position(source_range[:start])
        end_index = scanner.find_char_position(source_range[:end])
        extracted_source = T.must(@document.source[start_index...end_index])

        # Find the closest statements node, so that we place the refactor in a valid position
        closest_statements, parent_statements = @document
          .locate(@document.tree, start_index, node_types: [Prism::StatementsNode, Prism::BlockNode])

        return Error::InvalidTargetRange if closest_statements.nil? || closest_statements.child_nodes.compact.empty?

        # Find the node with the end line closest to the requested position, so that we can place the refactor
        # immediately after that closest node
        closest_node = T.must(closest_statements.child_nodes.compact.min_by do |node|
          distance = source_range.dig(:start, :line) - (node.location.end_line - 1)
          distance <= 0 ? Float::INFINITY : distance
        end)

        return Error::InvalidTargetRange if closest_node.is_a?(Prism::MissingNode)

        closest_node_loc = closest_node.location
        # If the parent expression is a single line block, then we have to extract it inside of the oneline block
        if parent_statements.is_a?(Prism::BlockNode) &&
            parent_statements.location.start_line == parent_statements.location.end_line

          variable_source = " #{NEW_VARIABLE_NAME} = #{extracted_source};"
          character = source_range.dig(:start, :character) - 1
          target_range = {
            start: { line: closest_node_loc.end_line - 1, character: character },
            end: { line: closest_node_loc.end_line - 1, character: character },
          }
        else
          # If the closest node covers the requested location, then we're extracting a statement nested inside of it. In
          # that case, we want to place the extraction at the start of the closest node (one line above). Otherwise, we
          # want to place the extract right below the closest node
          if closest_node_loc.start_line - 1 <= source_range.dig(
            :start,
            :line,
          ) && closest_node_loc.end_line - 1 >= source_range.dig(:end, :line)
            indentation_line_number = closest_node_loc.start_line - 1
            target_line = indentation_line_number
          else
            target_line = closest_node_loc.end_line
            indentation_line_number = closest_node_loc.end_line - 1
          end

          lines = @document.source.lines

          indentation_line = lines[indentation_line_number]
          return Error::InvalidTargetRange unless indentation_line

          indentation = T.must(indentation_line[/\A */]).size

          target_range = {
            start: { line: target_line, character: indentation },
            end: { line: target_line, character: indentation },
          }

          line = lines[target_line]
          return Error::InvalidTargetRange unless line

          variable_source = if line.strip.empty?
            "\n#{" " * indentation}#{NEW_VARIABLE_NAME} = #{extracted_source}"
          else
            "#{NEW_VARIABLE_NAME} = #{extracted_source}\n#{" " * indentation}"
          end
        end

        Interface::CodeAction.new(
          title: "Refactor: Extract Variable",
          edit: Interface::WorkspaceEdit.new(
            document_changes: [
              Interface::TextDocumentEdit.new(
                text_document: Interface::OptionalVersionedTextDocumentIdentifier.new(
                  uri: @code_action.dig(:data, :uri),
                  version: nil,
                ),
                edits: [
                  create_text_edit(source_range, NEW_VARIABLE_NAME),
                  create_text_edit(target_range, variable_source),
                ],
              ),
            ],
          ),
        )
      end

      private

      sig { params(range: T::Hash[Symbol, T.untyped], new_text: String).returns(Interface::TextEdit) }
      def create_text_edit(range, new_text)
        Interface::TextEdit.new(
          range: Interface::Range.new(
            start: Interface::Position.new(line: range.dig(:start, :line), character: range.dig(:start, :character)),
            end: Interface::Position.new(line: range.dig(:end, :line), character: range.dig(:end, :character)),
          ),
          new_text: new_text,
        )
      end
    end
  end
end