require 'stringio'

module TerraformLandscape
  # Takes output from Terraform executable nad outputs it in a prettified
  # format.
  class Printer
    def initialize(output)
      @output = output
    end

    def process_stream(io) # rubocop:disable Metrics/MethodLength
      apply = nil
      buffer = StringIO.new
      begin
        block_size = 1024

        done = false
        until done
          readable_fds, = IO.select([io])
          next unless readable_fds

          readable_fds.each do |f|
            begin
              buffer << strip_ansi(f.read_nonblock(block_size))
            rescue IO::WaitReadable # rubocop:disable Lint/HandleExceptions
              # Ignore; we'll call IO.select again
            rescue EOFError
              done = true
            end
          end

          apply = apply_prompt(buffer.string)
          done = true if apply
        end
        process_string(buffer.string)

        @output.print apply if apply
        @output.write_from(io)
      ensure
        io.close
      end
    end

    def process_string(plan_output) # rubocop:disable Metrics/MethodLength
      scrubbed_output = strip_ansi(plan_output)

      # Remove initialization messages like
      # "- Downloading plugin for provider "aws" (1.1.0)..."
      # as these break the parser which thinks "-" is a resource deletion
      scrubbed_output.gsub!(/^- .*\.\.\.$/, '')

      # Remove separation lines that appear after refreshing state
      scrubbed_output.gsub!(/^-+$/, '')

      # Remove preface
      if (match = scrubbed_output.match(/^Path:[^\n]+/))
        scrubbed_output = scrubbed_output[match.end(0)..-1]
      elsif (match = scrubbed_output.match(/^Terraform.+following\sactions:/))
        scrubbed_output = scrubbed_output[match.end(0)..-1]
      elsif (match = scrubbed_output.match(/^\s*(~|\+|\-)/))
        scrubbed_output = scrubbed_output[match.begin(0)..-1]
      elsif scrubbed_output =~ /^(No changes|This plan does nothing)/
        @output.puts 'No changes'
        return
      else
        raise ParseError, 'Output does not contain proper preface'
      end

      # Remove postface
      if (match = scrubbed_output.match(/^Plan:[^\n]+/))
        plan_summary = scrubbed_output[match.begin(0)..match.end(0)]
        scrubbed_output = scrubbed_output[0...match.begin(0)]
      end

      plan = TerraformPlan.from_output(scrubbed_output)
      plan.display(@output)
      @output.puts plan_summary
    end

    private

    def strip_ansi(string)
      string.gsub(/\e\[\d+m/, '')
    end

    def apply_prompt(output)
      return unless output =~ /Enter a value:\s+$/
      output[/Do you want to perform these actions\?.*$/m, 0]
    end
  end
end