require 'mime/types'
require 'erb'

if RUBY_VERSION >= "1.9.1"
  # The bundled mail library doesn't include activesupport.
  # Caveat is, it needs Ruby 1.9.x at least for the multibyte character
  # support. Why bother? Because ActiveSupport is evil, and we don't use
  # Rails. The memory overhead is just not worth it.
  $:.unshift(File.join(File.dirname(__FILE__), '..', '..', 'vendor', 'mail', 'lib'))
end

require 'mail'

module Rack
  class MailException
    VERSION = "0.0.1"

    FILTERING = %(['"]?%s['"]?=>?([^&\s]*))

    def initialize(app, options = {})
      @to      = options[:to]      || raise(ArgumentError, ":to is required")
      @from    = options[:from]    || raise(ArgumentError, ":from is required")
      @subject = options[:subject] || "[Application Exception] %s"

      @filters = Array(options[:filters])
      @app     = app
    end

    def call(env)
      status, headers, body =
        begin
          @app.call(env)
        rescue Exception => ex
          notify ex, env
          raise ex
        end

      [status, headers, body]
    end

  private
    def notify(exception, env)
      text = ERB.new(TEMPLATE).result(binding)

      Mail.deliver(
        :to      => @to,
        :from    => @from,
        :subject => @subject % exception,
        :body    => sanitize_filtered_parameters(text)
      )
    end

    def request_body(env)
      if io = env['rack.input']
        io.rewind if io.respond_to?(:rewind)
        io.read
      end
    end

    def sanitize_filtered_parameters(str)
      str.dup.tap do |ret|
        @filters.each do |filter|
          ret.gsub!(Regexp.new(FILTERING % filter)) { |m|
            m.gsub($1, '[FILTERED]')
          }
        end
      end
    end

    # Taken from rack/contrib/mailexceptions
    TEMPLATE = (<<-'EMAIL').gsub(/^ {4}/, '')
    A <%= exception.class.to_s %> occured: <%= exception.to_s %>
    <% if body = request_body(env) %>

    ===================================================================
    Request Body:
    ===================================================================

    <%= body.gsub(/^/, '  ') %>
    <% end %>

    ===================================================================
    Rack Environment:
    ===================================================================

      PID:                     <%= $$ %>
      PWD:                     <%= Dir.getwd %>

      <%= env.to_a.
        sort{|a,b| a.first <=> b.first}.
        map{ |k,v| "%-25s%p" % [k+':', v] }.
        join("\n  ") %>

    <% if exception.respond_to?(:backtrace) %>
    ===================================================================
    Backtrace:
    ===================================================================

      <%= exception.backtrace.join("\n  ") %>
    <% end %>
    EMAIL
  end
end