\input texinfo
@setfilename guile-email.info
@settitle guile-email

@copying
Copyright @copyright{} 2019, 2021 Arun Isaac@*

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end copying

@ifnottex
@node Top
@top guile-email
@end ifnottex

@menu
* Introduction:: What is guile-email?
* Parsing Email:: Parsing email
* Data Types:: Data types provided by guile-email
* Encoding and Decoding:: Encoding and decoding Base64, Quoted-Printable
  and Q-encoding
* Reading Email:: Reading emails from the mbox format
* Contributing:: Contributing

Indices

* Procedure Index::
* Type Index::

@end menu

@node Introduction
@chapter Introduction

guile-email is a collection of email utilities implemented in pure
guile.  It supports parsing MIME (Multipurpose Internet Mail Extensions)
compliant email messages as specified in RFC5322, RFC2045, RFC2046,
RF2047 and RFC2049.

@section Features

@itemize
@item Parse @uref{https://tools.ietf.org/html/rfc5322,,RFC5322} compliant email messages (currently does not support @uref{https://tools.ietf.org/html/rfc5322#section-4,,obsolete syntax})
@item Parse MIME compliant email messages as specified in @uref{https://tools.ietf.org/html/rfc2045,,RFC2045}, @uref{https://tools.ietf.org/html/rfc2046,,RFC2046}, @uref{https://tools.ietf.org/html/rfc2047,,RFC2047} and @uref{https://tools.ietf.org/html/rfc2049,,RFC2049}
@item Parse non-standard @uref{https://www.gnu.org/software/emacs/manual/html_node/emacs/Mail-Headers.html, Emacs message mode parens style addresses}
@item Encode and decode Quoted-Printable encoding, Base64 encoding and Q-encoding
@item Read emails from the @uref{https://en.wikipedia.org/wiki/Mbox, mbox format}
@end itemize

@node Parsing Email
@chapter Parsing Email

@example
(use-modules (email email))
@end example

@deftypefn {Scheme Procedure} parse-email (bytevector @var{email})
@deftypefnx {Scheme Procedure} parse-email (string @var{email})
Parse bytevector @var{email} and return result as an @code{<email>}
record.

Parse string @var{email} and return result as an @code{<email>}
record.
@end deftypefn

@deffn {Scheme Procedure} parse-email-headers headers
Parse string @var{headers} as email headers and return an association
list of header keys and values.
@end deffn

@deftypefn {Scheme Procedure} parse-email-body (string @var{headers}) (bytevector @var{body})
@deftypefnx {Scheme Procedure} parse-email-body (string @var{headers}) (string @var{body})
Parse bytevector @var{body} as email body where @var{headers} is an
association list of header keys and values as returned by
@code{parse-email-headers}. Return a list of <mime-entity> records if
the body is a multipart message. Else, return a single <mime-entity>
record.

Parse string @var{body} as email body where @var{headers} is an
association list of header keys and values as returned by
@code{parse-email-headers}. Return a list of <mime-entity> records if
the body is a multipart message. Else, return a single <mime-entity>
record.
@end deftypefn

Note that while an email can have characters encoded using different
schemes, a string is constrained to have all characters encoded using
the same scheme. Therefore, passing a string to @code{parse-email} or
@code{parse-email-body} will not always produce correct results. Hence,
this variant of @code{parse-email} and @code{parse-email-body} will be
deprecated in the future. This variant is only provided in the interest
of backward compatibility.

@node Data Types
@chapter Data Types

guile-email provides data types for representing emails and MIME
entities.

@section email data type

@deftp {Data Type} <email> headers body
This is the data type representing emails.
@end deftp

@deffn {Scheme Procedure} email? object
@deffnx {Scheme Procedure} email-headers email
@deffnx {Scheme Procedure} email-body email
Predicate and field accessors for the @code{<email>} data type.
@end deffn

@deffn {Scheme Procedure} make-email headers body
Construct an @code{<email>} object.  @var{headers} is an association
list of email headers.  @var{body} is either a string or a list of
@code{<mime-entity>} objects.
@end deffn

@section mime-entity data type

@deftp {Data Type} <mime-entity> headers body
This is the data type representing MIME entities.
@end deftp

@deffn {Scheme Procedure} mime-entity? object
@deffnx {Scheme Procedure} mime-entity-headers mime-entity
@deffnx {Scheme Procedure} mime-entity-body mime-entity
Predicate and field accessors for the @code{<mime-entity>} data type.
@end deffn

@deffn {Scheme Procedure} make-mime-entity headers body
Construct a mime-entity object.  @var{headers} is an association list of
MIME entity headers.  @var{body} is either a string or a list of
@code{<mime-entity>} objects.
@end deffn

@section email headers

The following descriptions of email headers are only a summary.  Please
see the relevant RFCs for more details.

@subsection email header types

@deftp {Email Header Type} AssociationList
An association list of key-value pairs (@pxref{Association Lists,,,
guile}).  Keys are the name of the email header, downcased and converted
to symbols.  Values are specific to the header and explained below.
@end deftp

@deftp {Email Header Type} Date
An SRFI-19 date.  @xref{SRFI-19 Date,,, guile}.
@end deftp

@deftp {Email Header Type} Address
An association list of atmost two keys - 'name' and 'address'.  The
values corresponding to these keys are explained below.

@table @code
@item name
Display name of the email address.  When the email address
does not specifiy a display name, this key will be absent.
@item address
Actual email address.
@end table
@end deftp

@deftp {Email Header Type} AddressList
A list of addresses, each of type 'Address'.
@end deftp

@deftp {Email Header Type} MessageID
A string containing an email message ID with the surrounding angle
brackets (@samp{<} and @samp{>}) removed.  Email message IDs uniquely
identify the email.
@end deftp

@deftp {Email Header Type} MessageIDList
A list of message IDs, each of type @code{MessageID}.
@end deftp

@subsection email headers

@deftypevr {Email Header} Date date
The date the email was sent on, as specified in the @dfn{Date} header.
@end deftypevr

@deftypevr {Email Header} AddressList from
The list of authors of the email, as specified in the @dfn{From} header.
@end deftypevr

@deftypevr {Email Header} Address sender
The sender of the email, as specified in the @dfn{Sender} header.
@end deftypevr

@deftypevr {Email Header} AddressList reply-to
The list of addresses the author of the email suggests replies be sent
to, as specified in the @dfn{Reply-To} header.
@end deftypevr

@deftypevr {Email Header} AddressList to
The list of primary recipients of the email, as specified in the
@dfn{To} header.
@end deftypevr

@deftypevr {Email Header} AddressList cc
The list of other recipients of the email at whom the content of the
email may not be directed, as specified in the @dfn{Cc} header.
@end deftypevr

@deftypevr {Email Header} AddressList bcc
THe list of recipients whose address is not to be revealed to other
recipients of the email, as specified in the @dfn{Bcc} header.
@end deftypevr

@deftypevr {Email Header} MessageID message-id
The message ID of the email, as specified in the @dfn{Message-ID}
header.
@end deftypevr

@deftypevr {Email Header} MessageIDList in-reply-to
The list of message IDs of emails to which this email is a reply, as
specified in the @dfn{In-Reply-To} header.
@end deftypevr

@deftypevr {Email Header} MessageIDList references
The list of message IDs specified in the @dfn{References} header.
@end deftypevr

@deftypevr {Email Header} String subject
A string identifying the topic of the email, as specified in the
@dfn{Subject} header.
@end deftypevr

@deftypevr {Email Header} String comments
A string containing additional comments on the body of the email, as
specified in the @dfn{Comments} header.
@end deftypevr

@deftypevr {Email Header} StringList keywords
A list of strings each an important word or phrase, as specified in the
@dfn{Keywords} header.
@end deftypevr

@deftypevr {Email Header} Date resent-date
The date at which the resent message was dispatched by the resender, as
specified in the @dfn{Resent-Date} header.
@end deftypevr

@deftypevr {Email Header} AddressList resent-from
The list of addresses specified in the @dfn{Resent-From} header.
@end deftypevr

@deftypevr {Email Header} Address resent-sender
The address specified in the @dfn{Resent-Sender} header.
@end deftypevr

@deftypevr {Email Header} AddressList resent-to
The list of addresses specified in the @dfn{Resent-To} header.
@end deftypevr

@deftypevr {Email Header} AddressList resent-cc
The list of addresses specified in the @dfn{Resent-Cc} header.
@end deftypevr

@deftypevr {Email Header} AddressList resent-bcc
The list of addresses specified in the @dfn{Resent-Bcc} header.
@end deftypevr

@deftypevr {Email Header} MessageID resent-message-id
The message ID specified in the @dfn{Resent-Message-ID} header.
@end deftypevr

@c TODO: Document trace fields

@deftypevr {Email Header} String mime-version
The MIME version specified in the @dfn{MIME-Version} header.
@end deftypevr

@deftypevr {Email Header} AssociationList content-type
The MIME type of the body, as specified in the @dfn{Content-Type}
header, as an association list.  The following keys always exist in the
association list.  Any additional parameters will also be listed as
key-value pairs.  Keys are names of the parameters, downcased and
converted to symbols.

@table @code
@item type
The primary type
@item subtype
The secondary type
@item charset
The charset
@end table
@end deftypevr

If no Content-Type header is present, a type of @code{text}, a subtype
of @code{plain} and a charset of ``utf-8'' is assumed as the default.
That is, the following:

@example
((type . text)
 (subtype . plain)
 (charset . "utf-8"))
@end example

@deftypevr {Email Header} AssociationList content-disposition
The content disposition type, as specified in the
@dfn{Content-Disposition} header, as an association list.  The following
keys always exist in the association list.

@table @code
@item type
@table @code
@item inline
@item attachment
@end table
@end table

Other optional keys include

@table @code
@item filename
@item creation-date
@item modification-date
@item read-date
@item size
@end table

Any additional parameters will also be listed as key-value pairs.
Keys are names of the parameters, downcased and converted to
symbols.
@end deftypevr

@deftypevr {Email Header} Symbol content-transfer-encoding
The encoding of the body of the email as specified in the
@dfn{Content-Transfer-Encoding} header.  This can be one of the
following symbols.

@table @code
@item 7bit
The message is 7-bit encoded.  This is the default if no
Content-Transfer-Encoding header is present.
@item 8bit
The message is 8-bit encoded.
@item quoted-printable
The message is encoded using Quoted-Printable encoding.
@item base64
The message is encoded using Base64 encoding.
@end table

Note that guile-email automatically decodes the email.  The user need
not read the @code{content-transfer-encoding} and invoke the appropriate
decoding procedure.  The @code{content-transfer-encoding} header is only
provided for the sake of completion.
@end deftypevr

@node Encoding and Decoding
@chapter Encoding and Decoding

guile-email supports encoding and decoding using Base64 encoding,
Quoted-Printable encoding and Q-encoding.  Note that guile-email
automatically invokes the necessary decoding procedures while parsing
email.  The following procedures are only provided in case you need to
use them in a context not automatically handled by guile-email.

Character encoding schemes such as UTF-8 encode characters as bytes.
Encoding schemes such as Quoted-Printable encoding, Base64 encoding and
Q-encoding re-encode these bytes as 7-bit text suitable for transmission
over a medium such as email that is not 8-bit clean.  Therefore, the
input to the following encoding procedures and the output from the
following decoding procedures is a bytevector.  Encoding characters to
bytes or decoding bytes to characters is not within the scope of these
procedures.  @xref{Representing Strings as Bytes,,, guile} for more
information on how to do this.

@section Base64 encoding

@example
(use-modules (email base64))
@end example

@deffn {Scheme Procedure} base64-encode bv
Encode bytevector @var{bv} using Base64 encoding and return the encoded
string.
@end deffn

@deffn {Scheme Procedure} base64-decode str
Decode Base64 encoded string @var{str} and return the decoded
bytevector.
@end deffn

@section Quoted-Printable encoding

The Quoted-Printable encoding and decoding procedures in this section
are typed functions in that they behave differently based on the types
of their arguments.

@example
(use-modules (email quoted-printable))
@end example

@deftypefn {Scheme Procedure} {} quoted-printable-encode (bytevector @var{bv})
@deftypefnx {Scheme Procedure} {} quoted-printable-encode (port @var{in})
@deftypefnx {Scheme Procedure} {} quoted-printable-encode (port @var{in}) (port @var{out})
Encode bytevector @var{bv} using Quoted-Printable encoding and return
the encoded string.

Read bytes from the bytevector input port @var{in} and return the
Quoted-Printable encoded string.

Read bytes from the bytevector input port @var{in} and write the
Quoted-Printable encoded string to output port @var{out}.
@end deftypefn

@deftypefn {Scheme Procedure} {} quoted-printable-decode (string @var{str})
@deftypefnx {Scheme Procedure} {} quoted-printable-decode (port @var{in})
@deftypefnx {Scheme Procedure} {} quoted-printable-decode (port @var{in}) (port @var{out})
Decode Quoted-Printable encoded string @var{str} and return the decoded
bytevector.

Read Quoted-Printable encoded characters from input port @var{in} and
return the decoded bytevector.

Read Quoted-Printable encoded characters from port @var{in} and write
the decoded bytevector to bytevector output port @var{out}.
@end deftypefn

@section Q-encoding

@example
(use-modules (email quoted-printable))
@end example

@deffn {Scheme Procedure} q-encoding-encode bv
Encode bytevector @var{bv} using Q-encoding and return the encoded
string.
@end deffn

@deffn {Scheme Procedure} q-encoding-decode str
Decode Q-encoding encoded string @var{str} and return the decoded
bytevector.
@end deffn

@node Reading Email
@chapter Reading Email

@deffn {Scheme Procedure} mbox->emails port
Read all emails from @var{port} and return as a list of bytevectors.
@var{port} is an input port reading an mbox file.
@end deffn

@node Contributing
@chapter Contributing

Feedback, suggestions, feature requests, bug reports and patches are all
welcome.  Please write to the mailing list at
@email{guile-email@@systemreboot.net}.

@node Procedure Index
@chapter Procedure Index

@printindex fn

@node Type Index
@chapter Type Index

@printindex tp

@bye