require 'time'

module Redwood

## a Message is what's threaded.
##
## it is also where the parsing for quotes and signatures is done, but
## that should be moved out to a separate class at some point (because
## i would like, for example, to be able to add in a ruby-talk
## specific module that would detect and link to /ruby-talk:\d+/
## sequences in the text of an email. (how sweet would that be?)

class Message
  SNIPPET_LEN = 80
  RE_PATTERN = /^((re|re[\[\(]\d[\]\)]):\s*)+/i

  ## some utility methods
  class << self
    def normalize_subj s; s.gsub(RE_PATTERN, ""); end
    def subj_is_reply? s; s =~ RE_PATTERN; end
    def reify_subj s; subj_is_reply?(s) ? s : "Re: " + s; end
  end

  QUOTE_PATTERN = /^\s{0,4}[>|\}]/
  BLOCK_QUOTE_PATTERN = /^-----\s*Original Message\s*----+$/
  SIG_PATTERN = /(^(- )*-- ?$)|(^\s*----------+\s*$)|(^\s*_________+\s*$)|(^\s*--~--~-)|(^\s*--\+\+\*\*==)/

  GPG_SIGNED_START = "-----BEGIN PGP SIGNED MESSAGE-----"
  GPG_SIGNED_END = "-----END PGP SIGNED MESSAGE-----"
  GPG_START = "-----BEGIN PGP MESSAGE-----"
  GPG_END = "-----END PGP MESSAGE-----"
  GPG_SIG_START = "-----BEGIN PGP SIGNATURE-----"
  GPG_SIG_END = "-----END PGP SIGNATURE-----"

  MAX_SIG_DISTANCE = 15 # lines from the end
  DEFAULT_SUBJECT = ""
  DEFAULT_SENDER = "(missing sender)"
  MAX_HEADER_VALUE_SIZE = 4096

  attr_reader :id, :date, :from, :subj, :refs, :replytos, :to,
              :cc, :bcc, :labels, :attachments, :list_address, :recipient_email, :replyto,
              :list_subscribe, :list_unsubscribe

  bool_reader :dirty, :source_marked_read, :snippet_contains_encrypted_content

  attr_accessor :locations

  ## if you specify a :header, will use values from that. otherwise,
  ## will try and load the header from the source.
  def initialize opts
    @locations = opts[:locations] or raise ArgumentError, "locations can't be nil"
    @snippet = opts[:snippet]
    @snippet_contains_encrypted_content = false
    @have_snippet = !(opts[:snippet].nil? || opts[:snippet].empty?)
    @labels = Set.new(opts[:labels] || [])
    @dirty = false
    @encrypted = false
    @chunks = nil
    @attachments = []

    ## we need to initialize this. see comments in parse_header as to
    ## why.
    @refs = []

    #parse_header(opts[:header] || @source.load_header(@source_info))
  end

  def decode_header_field v
    return unless v
    return v unless v.is_a? String
    return unless v.size < MAX_HEADER_VALUE_SIZE # avoid regex blowup on spam
    Rfc2047.decode_to $encoding, Iconv.easy_decode($encoding, 'ASCII', v)
  end

  def parse_header encoded_header
    header = SavingHash.new { |k| decode_header_field encoded_header[k] }

    @id = ''
    if header["message-id"]
      mid = header["message-id"] =~ /<(.+?)>/ ? $1 : header["message-id"]
      @id = sanitize_message_id mid
    end
    if (not @id.include? '@') || @id.length < 6
      @id = "sup-faked-" + Digest::MD5.hexdigest(raw_header)
      #from = header["from"]
      #debug "faking non-existent message-id for message from #{from}: #{id}"
    end

    @from = Person.from_address(if header["from"]
      header["from"]
    else
      name = "Sup Auto-generated Fake Sender <sup@fake.sender.example.com>"
      #debug "faking non-existent sender for message #@id: #{name}"
      name
    end)

    @date = case(date = header["date"])
    when Time
      date
    when String
      begin
        Time.parse date
      rescue ArgumentError => e
        #debug "faking mangled date header for #{@id} (orig #{header['date'].inspect} gave error: #{e.message})"
        Time.now
      end
    else
      #debug "faking non-existent date header for #{@id}"
      Time.now
    end

    @subj = header["subject"] ? header["subject"].gsub(/\s+/, " ").gsub(/\s+$/, "") : DEFAULT_SUBJECT
    @to = Person.from_address_list header["to"]
    @cc = Person.from_address_list header["cc"]
    @bcc = Person.from_address_list header["bcc"]

    ## before loading our full header from the source, we can actually
    ## have some extra refs set by the UI. (this happens when the user
    ## joins threads manually). so we will merge the current refs values
    ## in here.
    refs = (header["references"] || "").scan(/<(.+?)>/).map { |x| sanitize_message_id x.first }
    @refs = (@refs + refs).uniq
    @replytos = (header["in-reply-to"] || "").scan(/<(.+?)>/).map { |x| sanitize_message_id x.first }

    @replyto = Person.from_address header["reply-to"]
    @list_address = if header["list-post"]
      address = if header["list-post"] =~ /mailto:(.*?)[>\s$]/
        $1
      elsif header["list-post"] =~ /@/
        header["list-post"] # just try the whole fucking thing
      end
      address && Person.from_address(address)
    elsif header["x-mailing-list"]
      Person.from_address header["x-mailing-list"]
    end

    @recipient_email = header["envelope-to"] || header["x-original-to"] || header["delivered-to"]
    @source_marked_read = header["status"] == "RO"
    @list_subscribe = header["list-subscribe"]
    @list_unsubscribe = header["list-unsubscribe"]
  end

  ## Expected index entry format:
  ## :message_id, :subject => String
  ## :date => Time
  ## :refs, :replytos => Array of String
  ## :from => Person
  ## :to, :cc, :bcc => Array of Person
  def load_from_index! entry
    @id = entry[:message_id]
    @from = entry[:from]
    @date = entry[:date]
    @subj = entry[:subject]
    @to = entry[:to]
    @cc = entry[:cc]
    @bcc = entry[:bcc]
    @refs = (@refs + entry[:refs]).uniq
    @replytos = entry[:replytos]

    @replyto = nil
    @list_address = nil
    @recipient_email = nil
    @source_marked_read = false
    @list_subscribe = nil
    @list_unsubscribe = nil
  end

  def add_ref ref
    @refs << ref
    @dirty = true
  end

  def remove_ref ref
    @dirty = true if @refs.delete ref
  end

  attr_reader :snippet
  def is_list_message?; !@list_address.nil?; end
  def is_draft?; @labels.member? :draft; end
  def draft_filename
    raise "not a draft" unless is_draft?
    source.fn_for_offset source_info
  end

  ## sanitize message ids by removing spaces and non-ascii characters.
  ## also, truncate to 255 characters. all these steps are necessary
  ## to make the index happy. of course, we probably fuck up a couple
  ## valid message ids as well. as long as we're consistent, this
  ## should be fine, though.
  ##
  ## also, mostly the message ids that are changed by this belong to
  ## spam email.
  ##
  ## an alternative would be to SHA1 or MD5 all message ids on a regular basis.
  ## don't tempt me.
  def sanitize_message_id mid; mid.gsub(/(\s|[^\000-\177])+/, "")[0..254] end

  def clear_dirty
    @dirty = false
  end

  def has_label? t; @labels.member? t; end
  def add_label l
    l = l.to_sym
    return if @labels.member? l
    @labels << l
    @dirty = true
  end
  def remove_label l
    l = l.to_sym
    return unless @labels.member? l
    @labels.delete l
    @dirty = true
  end

  def recipients
    @to + @cc + @bcc
  end

  def labels= l
    raise ArgumentError, "not a set" unless l.is_a?(Set)
    raise ArgumentError, "not a set of labels" unless l.all? { |ll| ll.is_a?(Symbol) }
    return if @labels == l
    @labels = l
    @dirty = true
  end

  def chunks
    load_from_source!
    @chunks
  end

  def location
    @locations.find { |x| x.valid? } || raise(OutOfSyncSourceError.new)
  end

  def source
    location.source
  end

  def source_info
    location.info
  end

  ## this is called when the message body needs to actually be loaded.
  def load_from_source!
    @chunks ||=
      begin
        ## we need to re-read the header because it contains information
        ## that we don't store in the index. actually i think it's just
        ## the mailing list address (if any), so this is kinda overkill.
        ## i could just store that in the index, but i think there might
        ## be other things like that in the future, and i'd rather not
        ## bloat the index.
        ## actually, it's also the differentiation between to/cc/bcc,
        ## so i will keep this.
        rmsg = location.parsed_message
        parse_header rmsg.header
        message_to_chunks rmsg
      rescue SourceError, SocketError, RMail::EncodingUnsupportedError => e
        warn "problem reading message #{id}"
        [Chunk::Text.new(error_message.split("\n"))]
      end
  end

  def error_message
    <<EOS
#@snippet...

***********************************************************************
 An error occurred while loading this message.
***********************************************************************
EOS
  end

  def raw_header
    location.raw_header
  end

  def raw_message
    location.raw_message
  end

  def each_raw_message_line &b
    location.each_raw_message_line &b
  end

  ## returns all the content from a message that will be indexed
  def indexable_content
    load_from_source!
    [
      from && from.indexable_content,
      to.map { |p| p.indexable_content },
      cc.map { |p| p.indexable_content },
      bcc.map { |p| p.indexable_content },
      indexable_chunks.map { |c| c.lines },
      indexable_subject,
    ].flatten.compact.join " "
  end

  def indexable_body
    indexable_chunks.map { |c| c.lines }.flatten.compact.join " "
  end

  def indexable_chunks
    chunks.select { |c| c.is_a? Chunk::Text }
  end

  def indexable_subject
    Message.normalize_subj(subj)
  end

  def quotable_body_lines
    chunks.find_all { |c| c.quotable? }.map { |c| c.lines }.flatten
  end

  def quotable_header_lines
    ["From: #{@from.full_address}"] +
      (@to.empty? ? [] : ["To: " + @to.map { |p| p.full_address }.join(", ")]) +
      (@cc.empty? ? [] : ["Cc: " + @cc.map { |p| p.full_address }.join(", ")]) +
      (@bcc.empty? ? [] : ["Bcc: " + @bcc.map { |p| p.full_address }.join(", ")]) +
      ["Date: #{@date.rfc822}",
       "Subject: #{@subj}"]
  end

  def self.build_from_source source, source_info
    m = Message.new :locations => [Location.new(source, source_info)]
    m.load_from_source!
    m
  end

private

  ## here's where we handle decoding mime attachments. unfortunately
  ## but unsurprisingly, the world of mime attachments is a bit of a
  ## mess. as an empiricist, i'm basing the following behavior on
  ## observed mail rather than on interpretations of rfcs, so probably
  ## this will have to be tweaked.
  ##
  ## the general behavior i want is: ignore content-disposition, at
  ## least in so far as it suggests something being inline vs being an
  ## attachment. (because really, that should be the recipient's
  ## decision to make.) if a mime part is text/plain, OR if the user
  ## decoding hook converts it, then decode it and display it
  ## inline. for these decoded attachments, if it has associated
  ## filename, then make it collapsable and individually saveable;
  ## otherwise, treat it as regular body text.
  ##
  ## everything else is just an attachment and is not displayed
  ## inline.
  ##
  ## so, in contrast to mutt, the user is not exposed to the workings
  ## of the gruesome slaughterhouse and sausage factory that is a
  ## mime-encoded message, but need only see the delicious end
  ## product.

  def multipart_signed_to_chunks m
    if m.body.size != 2
      warn "multipart/signed with #{m.body.size} parts (expecting 2)"
      return
    end

    payload, signature = m.body
    if signature.multipart?
      warn "multipart/signed with payload multipart #{payload.multipart?} and signature multipart #{signature.multipart?}"
      return
    end

    ## this probably will never happen
    if payload.header.content_type && payload.header.content_type.downcase == "application/pgp-signature"
      warn "multipart/signed with payload content type #{payload.header.content_type}"
      return
    end

    if signature.header.content_type && signature.header.content_type.downcase != "application/pgp-signature"
      ## unknown signature type; just ignore.
      #warn "multipart/signed with signature content type #{signature.header.content_type}"
      return
    end

    [CryptoManager.verify(payload, signature), message_to_chunks(payload)].flatten.compact
  end

  def multipart_encrypted_to_chunks m
    if m.body.size != 2
      warn "multipart/encrypted with #{m.body.size} parts (expecting 2)"
      return
    end

    control, payload = m.body
    if control.multipart?
      warn "multipart/encrypted with control multipart #{control.multipart?} and payload multipart #{payload.multipart?}"
      return
    end

    if payload.header.content_type && payload.header.content_type.downcase != "application/octet-stream"
      warn "multipart/encrypted with payload content type #{payload.header.content_type}"
      return
    end

    if control.header.content_type && control.header.content_type.downcase != "application/pgp-encrypted"
      warn "multipart/encrypted with control content type #{signature.header.content_type}"
      return
    end

    notice, sig, decryptedm = CryptoManager.decrypt payload
    if decryptedm # managed to decrypt
      children = message_to_chunks(decryptedm, true)
      [notice, sig].compact + children
    else
      [notice]
    end
  end

  ## takes a RMail::Message, breaks it into Chunk:: classes.
  def message_to_chunks m, encrypted=false, sibling_types=[]
    if m.multipart?
      chunks =
        case m.header.content_type.downcase
        when "multipart/signed"
          multipart_signed_to_chunks m
        when "multipart/encrypted"
          multipart_encrypted_to_chunks m
        end

      unless chunks
        sibling_types = m.body.map { |p| p.header.content_type }
        chunks = m.body.map { |p| message_to_chunks p, encrypted, sibling_types }.flatten.compact
      end

      chunks
    elsif m.header.content_type && m.header.content_type.downcase == "message/rfc822"
      encoding = m.header["Content-Transfer-Encoding"]
      if m.body
        body =
        case encoding
        when "base64"
          m.body.unpack("m")[0]
        when "quoted-printable"
          m.body.unpack("M")[0]
        when "7bit", "8bit", nil
          m.body
        else
          raise RMail::EncodingUnsupportedError, encoding.inspect
        end
        body = body.normalize_whitespace
        payload = RMail::Parser.read(body)
        from = payload.header.from.first ? payload.header.from.first.format : ""
        to = payload.header.to.map { |p| p.format }.join(", ")
        cc = payload.header.cc.map { |p| p.format }.join(", ")
        subj = decode_header_field(payload.header.subject) || DEFAULT_SUBJECT
        subj = Message.normalize_subj(subj.gsub(/\s+/, " ").gsub(/\s+$/, ""))
        msgdate = payload.header.date
        from_person = from ? Person.from_address(decode_header_field(from)) : nil
        to_people = to ? Person.from_address_list(decode_header_field(to)) : nil
        cc_people = cc ? Person.from_address_list(decode_header_field(cc)) : nil
        [Chunk::EnclosedMessage.new(from_person, to_people, cc_people, msgdate, subj)] + message_to_chunks(payload, encrypted)
      else
        debug "no body for message/rfc822 enclosure; skipping"
        []
      end
    elsif m.header.content_type && m.header.content_type.downcase == "application/pgp" && m.body
      ## apparently some versions of Thunderbird generate encryped email that
      ## does not follow RFC3156, e.g. messages with X-Enigmail-Version: 0.95.0
      ## they have no MIME multipart and just set the body content type to
      ## application/pgp. this handles that.
      ##
      ## TODO: unduplicate code between here and multipart_encrypted_to_chunks
      notice, sig, decryptedm = CryptoManager.decrypt m.body
      if decryptedm # managed to decrypt
        children = message_to_chunks decryptedm, true
        [notice, sig].compact + children
      else
        [notice]
      end
    else
      filename =
        ## first, paw through the headers looking for a filename.
        ## RFC 2183 (Content-Disposition) specifies that disposition-parms are
        ## separated by ";". So, we match everything up to " and ; (if present).
        if m.header["Content-Disposition"] && m.header["Content-Disposition"] =~ /filename="?(.*?[^\\])("|;|\z)/m
          $1
        elsif m.header["Content-Type"] && m.header["Content-Type"] =~ /name="?(.*?[^\\])("|;|\z)/im
          $1

        ## haven't found one, but it's a non-text message. fake
        ## it.
        ##
        ## TODO: make this less lame.
        elsif m.header["Content-Type"] && m.header["Content-Type"] !~ /^text\/plain/i
          extension =
            case m.header["Content-Type"]
            when /text\/html/ then "html"
            when /image\/(.*)/ then $1
            end

          ["sup-attachment-#{Time.now.to_i}-#{rand 10000}", extension].join(".")
        end

      ## if there's a filename, we'll treat it as an attachment.
      if filename
        ## filename could be 2047 encoded
        filename = Rfc2047.decode_to $encoding, filename
        # add this to the attachments list if its not a generated html
        # attachment (should we allow images with generated names?).
        # Lowercase the filename because searches are easier that way
        @attachments.push filename.downcase unless filename =~ /^sup-attachment-/
        add_label :attachment unless filename =~ /^sup-attachment-/
        content_type = (m.header.content_type || "application/unknown").downcase # sometimes RubyMail gives us nil
        [Chunk::Attachment.new(content_type, filename, m, sibling_types)]

      ## otherwise, it's body text
      else
        ## Decode the body, charset conversion will follow either in
        ## inline_gpg_to_chunks (for inline GPG signed messages) or
        ## a few lines below (messages without inline GPG)
        body = m.body ? m.decode : ""

        ## Check for inline-PGP
        chunks = inline_gpg_to_chunks body, $encoding, (m.charset || $encoding)
        return chunks if chunks

        if m.body
          ## if there's no charset, use the current encoding as the charset.
          ## this ensures that the body is normalized to avoid non-displayable
          ## characters
          body = Iconv.easy_decode($encoding, m.charset || $encoding, m.decode)
        else
          body = ""
        end

        text_to_chunks(body.normalize_whitespace.split("\n"), encrypted)
      end
    end
  end

  ## looks for gpg signed (but not encrypted) inline  messages inside the
  ## message body (there is no extra header for inline GPG) or for encrypted
  ## (and possible signed) inline GPG messages
  def inline_gpg_to_chunks body, encoding_to, encoding_from
    lines = body.split("\n")
    gpg = lines.between(GPG_SIGNED_START, GPG_SIGNED_END)
    if !gpg.empty?
      msg = RMail::Message.new
      msg.body = gpg.join("\n")

      body = Iconv.easy_decode(encoding_to, encoding_from, body)
      lines = body.split("\n")
      sig = lines.between(GPG_SIGNED_START, GPG_SIG_START)
      startidx = lines.index(GPG_SIGNED_START)
      endidx = lines.index(GPG_SIG_END)
      before = startidx != 0 ? lines[0 .. startidx-1] : []
      after = endidx ? lines[endidx+1 .. lines.size] : []

      payload = RMail::Message.new
      payload.body = sig[1, sig.size-2].join("\n")
      return [text_to_chunks(before, false),
              CryptoManager.verify(nil, msg, false),
              message_to_chunks(payload),
              text_to_chunks(after, false)].flatten.compact
    end

    gpg = lines.between(GPG_START, GPG_END)
    # between does not check if GPG_END actually exists
    if !gpg.empty? && !lines.index(GPG_END).nil?
      msg = RMail::Message.new
      msg.body = gpg.join("\n")

      startidx = lines.index(GPG_START)
      before = startidx != 0 ? lines[0 .. startidx-1] : []
      after = lines[lines.index(GPG_END)+1 .. lines.size]

      notice, sig, decryptedm = CryptoManager.decrypt msg, true
      chunks = if decryptedm # managed to decrypt
        children = message_to_chunks(decryptedm, true)
        [notice, sig].compact + children
      else
        [notice]
      end
      return [text_to_chunks(before, false),
              chunks,
              text_to_chunks(after, false)].flatten.compact
    end
  end

  ## parse the lines of text into chunk objects.  the heuristics here
  ## need tweaking in some nice manner. TODO: move these heuristics
  ## into the classes themselves.
  def text_to_chunks lines, encrypted
    state = :text # one of :text, :quote, or :sig
    chunks = []
    chunk_lines = []
    nextline_index = -1

    lines.each_with_index do |line, i|
      if i >= nextline_index
        # look for next nonblank line only when needed to avoid O(n²)
        # behavior on sequences of blank lines
        if nextline_index = lines[(i+1)..-1].index { |l| l !~ /^\s*$/ } # skip blank lines
          nextline_index += i + 1
          nextline = lines[nextline_index]
        else
          nextline_index = lines.length
          nextline = nil
        end
      end

      case state
      when :text
        newstate = nil

        ## the following /:$/ followed by /\w/ is an attempt to detect the
        ## start of a quote. this is split into two regexen because the
        ## original regex /\w.*:$/ had very poor behavior on long lines
        ## like ":a:a:a:a:a" that occurred in certain emails.
        if line =~ QUOTE_PATTERN || (line =~ /:$/ && line =~ /\w/ && nextline =~ QUOTE_PATTERN)
          newstate = :quote
        elsif line =~ SIG_PATTERN && (lines.length - i) < MAX_SIG_DISTANCE
          newstate = :sig
        elsif line =~ BLOCK_QUOTE_PATTERN
          newstate = :block_quote
        end

        if newstate
          chunks << Chunk::Text.new(chunk_lines) unless chunk_lines.empty?
          chunk_lines = [line]
          state = newstate
        else
          chunk_lines << line
        end

      when :quote
        newstate = nil

        if line =~ QUOTE_PATTERN || (line =~ /^\s*$/ && nextline =~ QUOTE_PATTERN)
          chunk_lines << line
        elsif line =~ SIG_PATTERN && (lines.length - i) < MAX_SIG_DISTANCE
          newstate = :sig
        else
          newstate = :text
        end

        if newstate
          if chunk_lines.empty?
            # nothing
          else
            chunks << Chunk::Quote.new(chunk_lines)
          end
          chunk_lines = [line]
          state = newstate
        end

      when :block_quote, :sig
        chunk_lines << line
      end

      if !@have_snippet && state == :text && (@snippet.nil? || @snippet.length < SNIPPET_LEN) && line !~ /[=\*#_-]{3,}/ && line !~ /^\s*$/
        @snippet ||= ""
        @snippet += " " unless @snippet.empty?
        @snippet += line.gsub(/^\s+/, "").gsub(/[\r\n]/, "").gsub(/\s+/, " ")
        oldlen = @snippet.length
        @snippet = @snippet[0 ... SNIPPET_LEN].chomp
        @snippet += "..." if @snippet.length < oldlen
        @dirty = true unless encrypted && $config[:discard_snippets_from_encrypted_messages]
        @snippet_contains_encrypted_content = true if encrypted
      end
    end

    ## final object
    case state
    when :quote, :block_quote
      chunks << Chunk::Quote.new(chunk_lines) unless chunk_lines.empty?
    when :text
      chunks << Chunk::Text.new(chunk_lines) unless chunk_lines.empty?
    when :sig
      chunks << Chunk::Signature.new(chunk_lines) unless chunk_lines.empty?
    end
    chunks
  end
end

class Location
  attr_reader :source
  attr_reader :info

  def initialize source, info
    @source = source
    @info = info
  end

  def raw_header
    source.raw_header info
  end

  def raw_message
    source.raw_message info
  end

  ## much faster than raw_message
  def each_raw_message_line &b
    source.each_raw_message_line info, &b
  end

  def parsed_message
    source.load_message info
  end

  def valid?
    source.valid? info
  end

  def == o
    o.source.id == source.id and o.info == info
  end

  def hash
    [source.id, info].hash
  end
end

end
