require 'active_support/core_ext/module/attribute_accessors'
require 'rack/utils'

module ActionDispatch
  class ExceptionWrapper
    cattr_accessor :rescue_responses
    @@rescue_responses = Hash.new(:internal_server_error)
    @@rescue_responses.merge!(
      'ActionController::RoutingError'                => :not_found,
      'AbstractController::ActionNotFound'            => :not_found,
      'ActionController::MethodNotAllowed'            => :method_not_allowed,
      'ActionController::UnknownHttpMethod'           => :method_not_allowed,
      'ActionController::NotImplemented'              => :not_implemented,
      'ActionController::UnknownFormat'               => :not_acceptable,
      'ActionController::InvalidAuthenticityToken'    => :unprocessable_entity,
      'ActionController::InvalidCrossOriginRequest'   => :unprocessable_entity,
      'ActionDispatch::ParamsParser::ParseError'      => :bad_request,
      'ActionController::BadRequest'                  => :bad_request,
      'ActionController::ParameterMissing'            => :bad_request,
      'Rack::Utils::ParameterTypeError'               => :bad_request,
      'Rack::Utils::InvalidParameterError'            => :bad_request
    )

    cattr_accessor :rescue_templates
    @@rescue_templates = Hash.new('diagnostics')
    @@rescue_templates.merge!(
      'ActionView::MissingTemplate'         => 'missing_template',
      'ActionController::RoutingError'      => 'routing_error',
      'AbstractController::ActionNotFound'  => 'unknown_action',
      'ActionView::Template::Error'         => 'template_error'
    )

    attr_reader :backtrace_cleaner, :exception, :line_number, :file

    def initialize(backtrace_cleaner, exception)
      @backtrace_cleaner = backtrace_cleaner
      @exception = original_exception(exception)

      expand_backtrace if exception.is_a?(SyntaxError) || exception.cause.is_a?(SyntaxError)
    end

    def rescue_template
      @@rescue_templates[@exception.class.name]
    end

    def status_code
      self.class.status_code_for_exception(@exception.class.name)
    end

    def application_trace
      clean_backtrace(:silent)
    end

    def framework_trace
      clean_backtrace(:noise)
    end

    def full_trace
      clean_backtrace(:all)
    end

    def traces
      application_trace_with_ids = []
      framework_trace_with_ids = []
      full_trace_with_ids = []

      full_trace.each_with_index do |trace, idx|
        trace_with_id = { id: idx, trace: trace }

        if application_trace.include?(trace)
          application_trace_with_ids << trace_with_id
        else
          framework_trace_with_ids << trace_with_id
        end

        full_trace_with_ids << trace_with_id
      end

      {
        "Application Trace" => application_trace_with_ids,
        "Framework Trace" => framework_trace_with_ids,
        "Full Trace" => full_trace_with_ids
      }
    end

    def self.status_code_for_exception(class_name)
      Rack::Utils.status_code(@@rescue_responses[class_name])
    end

    def source_extracts
      backtrace.map do |trace|
        file, line_number = extract_file_and_line_number(trace)

        {
          code: source_fragment(file, line_number),
          line_number: line_number
        }
      end
    end

    private

    def backtrace
      Array(@exception.backtrace)
    end

    def original_exception(exception)
      if @@rescue_responses.has_key?(exception.cause.class.name)
        exception.cause
      else
        exception
      end
    end

    def clean_backtrace(*args)
      if backtrace_cleaner
        backtrace_cleaner.clean(backtrace, *args)
      else
        backtrace
      end
    end

    def source_fragment(path, line)
      return unless Rails.respond_to?(:root) && Rails.root
      full_path = Rails.root.join(path)
      if File.exist?(full_path)
        File.open(full_path, "r") do |file|
          start = [line - 3, 0].max
          lines = file.each_line.drop(start).take(6)
          Hash[*(start+1..(lines.count+start)).zip(lines).flatten]
        end
      end
    end

    def extract_file_and_line_number(trace)
      # Split by the first colon followed by some digits, which works for both
      # Windows and Unix path styles.
      file, line = trace.match(/^(.+?):(\d+).*$/, &:captures) || trace
      [file, line.to_i]
    end

    def expand_backtrace
      @exception.backtrace.unshift(
        @exception.to_s.split("\n")
      ).flatten!
    end
  end
end