bodyext
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1 changed files with 331 additions and 0 deletions
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use std::borrow::Cow;
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use std::num::NonZeroU32;
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use std::collections::HashSet;
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use anyhow::{anyhow, bail, Result};
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use imap_codec::imap_types::body::{BasicFields, Body as FetchBody, BodyStructure, SpecificFields};
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use imap_codec::imap_types::core::{AString, IString, NonEmptyVec};
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use imap_codec::imap_types::fetch::{
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Section as FetchSection, Part as FetchPart
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};
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use eml_codec::{
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header, part::AnyPart, part::composite, part::discrete,
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};
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pub enum BodySection<'a> {
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Full(Cow<'a, [u8]>),
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Slice {
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body: Cow<'a, [u8]>,
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origin_octet: u32,
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},
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}
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/// Logic for BODY[<section>]<<partial>>
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/// Works in 3 times:
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/// 1. Find the section (RootMime::subset)
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/// 2. Apply the extraction logic (SelectedMime::extract), like TEXT, HEADERS, etc.
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/// 3. Keep only the given subset provided by partial
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///
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/// Example of message sections:
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///
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/// ```
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/// HEADER ([RFC-2822] header of the message)
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/// TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
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/// 1 TEXT/PLAIN
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/// 2 APPLICATION/OCTET-STREAM
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/// 3 MESSAGE/RFC822
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/// 3.HEADER ([RFC-2822] header of the message)
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/// 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
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/// 3.1 TEXT/PLAIN
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/// 3.2 APPLICATION/OCTET-STREAM
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/// 4 MULTIPART/MIXED
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/// 4.1 IMAGE/GIF
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/// 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
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/// 4.2 MESSAGE/RFC822
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/// 4.2.HEADER ([RFC-2822] header of the message)
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/// 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
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/// 4.2.1 TEXT/PLAIN
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/// 4.2.2 MULTIPART/ALTERNATIVE
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/// 4.2.2.1 TEXT/PLAIN
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/// 4.2.2.2 TEXT/RICHTEXT
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/// ```
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pub fn body_ext<'a>(
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part: &'a AnyPart<'a>,
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section: &'a Option<FetchSection<'a>>,
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partial: &'a Option<(u32, NonZeroU32)>
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) -> Result<BodySection<'a>> {
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let root_mime = NodeMime(part);
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let (extractor, path) = SubsettedSection::from(section);
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let selected_mime = root_mime.subset(path)?;
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let extracted_full = selected_mime.extract(&extractor)?;
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Ok(extracted_full.to_body_section(partial))
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}
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/// Logic for BODY and BODYSTRUCTURE
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///
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/// ```raw
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/// b fetch 29878:29879 (BODY)
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/// * 29878 FETCH (BODY (("text" "plain" ("charset" "utf-8") NIL NIL "quoted-printable" 3264 82)("text" "html" ("charset" "utf-8") NIL NIL "quoted-printable" 31834 643) "alternative"))
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/// * 29879 FETCH (BODY ("text" "html" ("charset" "us-ascii") NIL NIL "7bit" 4107 131))
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/// ^^^^^^^^^^^^^^^^^^^^^^ ^^^ ^^^ ^^^^^^ ^^^^ ^^^
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/// | | | | | | number of lines
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/// | | | | | size
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/// | | | | content transfer encoding
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/// | | | description
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/// | | id
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/// | parameter list
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/// b OK Fetch completed (0.001 + 0.000 secs).
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/// ```
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pub fn bodystructure(part: &AnyPart) -> Result<BodyStructure<'static>> {
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unimplemented!();
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}
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/// NodeMime
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///
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struct NodeMime<'a>(&'a AnyPart<'a>);
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impl<'a> NodeMime<'a> {
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/// A MIME object is a tree of elements.
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/// The path indicates which element must be picked.
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/// This function returns the picked element as the new view
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fn subset(self, path: Option<&'a FetchPart>) -> Result<SelectedMime<'a>> {
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match path {
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None => Ok(SelectedMime(self.0)),
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Some(v) => self.rec_subset(v.0.as_ref()),
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}
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}
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fn rec_subset(self, path: &'a [NonZeroU32]) -> Result<SelectedMime> {
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if path.is_empty() {
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Ok(SelectedMime(self.0))
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} else {
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match self.0 {
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AnyPart::Mult(x) => {
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let next = Self(x.children
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.get(path[0].get() as usize - 1)
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.ok_or(anyhow!("Unable to resolve subpath {:?}, current multipart has only {} elements", path, x.children.len()))?);
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next.rec_subset(&path[1..])
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},
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AnyPart::Msg(x) => {
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let next = Self(x.child.as_ref());
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next.rec_subset(path)
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},
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_ => bail!("You tried to access a subpart on an atomic part (text or binary). Unresolved subpath {:?}", path),
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}
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}
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}
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}
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//----------------------------------------------------------
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/// A FetchSection must be handled in 2 times:
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/// - First we must extract the MIME part
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/// - Then we must process it as desired
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/// The given struct mixes both work, so
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/// we separate this work here.
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enum SubsettedSection<'a> {
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Part,
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Header,
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HeaderFields(&'a NonEmptyVec<AString<'a>>),
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HeaderFieldsNot(&'a NonEmptyVec<AString<'a>>),
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Text,
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Mime,
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}
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impl<'a> SubsettedSection<'a> {
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fn from(section: &'a Option<FetchSection>) -> (Self, Option<&'a FetchPart>) {
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match section {
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Some(FetchSection::Text(maybe_part)) => (Self::Text, maybe_part.as_ref()),
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Some(FetchSection::Header(maybe_part)) => (Self::Header, maybe_part.as_ref()),
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Some(FetchSection::HeaderFields(maybe_part, fields)) => (Self::HeaderFields(fields), maybe_part.as_ref()),
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Some(FetchSection::HeaderFieldsNot(maybe_part, fields)) => (Self::HeaderFieldsNot(fields), maybe_part.as_ref()),
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Some(FetchSection::Mime(part)) => (Self::Mime, Some(part)),
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Some(FetchSection::Part(part)) => (Self::Part, Some(part)),
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None => (Self::Part, None),
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}
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}
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}
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struct SelectedMime<'a>(&'a AnyPart<'a>);
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impl<'a> SelectedMime<'a> {
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/// The subsetted fetch section basically tells us the
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/// extraction logic to apply on our selected MIME.
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/// This function acts as a router for these logic.
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fn extract(&self, extractor: &SubsettedSection<'a>) -> Result<ExtractedFull<'a>> {
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match extractor {
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SubsettedSection::Text => self.text(),
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SubsettedSection::Header => self.header(),
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SubsettedSection::HeaderFields(fields) => self.header_fields(fields, false),
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SubsettedSection::HeaderFieldsNot(fields) => self.header_fields(fields, true),
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SubsettedSection::Part => self.part(),
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SubsettedSection::Mime => self.mime(),
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}
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}
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fn mime(&self) -> Result<ExtractedFull<'a>> {
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let bytes = match &self.0 {
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AnyPart::Txt(p) => p.mime.fields.raw,
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AnyPart::Bin(p) => p.mime.fields.raw,
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AnyPart::Msg(p) => p.child.mime().raw,
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AnyPart::Mult(p) => p.mime.fields.raw,
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};
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Ok(ExtractedFull(bytes.into()))
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}
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fn part(&self) -> Result<ExtractedFull<'a>> {
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let bytes = match &self.0 {
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AnyPart::Txt(p) => p.body,
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AnyPart::Bin(p) => p.body,
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AnyPart::Msg(p) => p.raw_part,
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AnyPart::Mult(_) => bail!("Multipart part has no body"),
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};
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Ok(ExtractedFull(bytes.to_vec().into()))
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}
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/// The [...] HEADER.FIELDS, and HEADER.FIELDS.NOT part
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/// specifiers refer to the [RFC-2822] header of the message or of
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/// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
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/// HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
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/// field-name (as defined in [RFC-2822]) names, and return a
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/// subset of the header. The subset returned by HEADER.FIELDS
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/// contains only those header fields with a field-name that
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/// matches one of the names in the list; similarly, the subset
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/// returned by HEADER.FIELDS.NOT contains only the header fields
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/// with a non-matching field-name. The field-matching is
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/// case-insensitive but otherwise exact.
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fn header_fields(&self, fields: &'a NonEmptyVec<AString<'a>>, invert: bool) -> Result<ExtractedFull<'a>> {
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// Build a lowercase ascii hashset with the fields to fetch
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let index = fields
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.as_ref()
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.iter()
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.map(|x| match x {
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AString::Atom(a) => a.inner().as_bytes(),
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AString::String(IString::Literal(l)) => l.as_ref(),
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AString::String(IString::Quoted(q)) => q.inner().as_bytes(),
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}.to_ascii_lowercase())
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.collect::<HashSet<_>>();
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// Extract MIME headers
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let mime = match &self.0 {
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AnyPart::Msg(msg) => msg.child.mime(),
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other => other.mime(),
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};
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// Filter our MIME headers based on the field index
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// 1. Keep only the correctly formatted headers
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// 2. Keep only based on the index presence or absence
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// 3. Reduce as a byte vector
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let buffer = mime.kv.iter()
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.filter_map(|field| match field {
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header::Field::Good(header::Kv2(k, v)) => Some((k, v)),
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_ => None,
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})
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.filter(|(k, _)| index.contains(&k.to_ascii_lowercase()) ^ invert)
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.fold(vec![], |mut acc, (k, v)| {
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acc.extend(*k);
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acc.extend(b": ");
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acc.extend(*v);
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acc.extend(b"\r\n");
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acc
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});
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Ok(ExtractedFull(buffer.into()))
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}
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/// The HEADER [...] part specifiers refer to the [RFC-2822] header of the message or of
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/// an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
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/// ```raw
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/// HEADER ([RFC-2822] header of the message)
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/// ```
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fn header(&self) -> Result<ExtractedFull<'a>> {
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let msg = self.0.as_message().ok_or(anyhow!("Selected part must be a message/rfc822"))?;
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Ok(ExtractedFull(msg.raw_headers.into()))
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}
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/// The TEXT part specifier refers to the text body of the message, omitting the [RFC-2822] header.
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fn text(&self) -> Result<ExtractedFull<'a>> {
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let msg = self.0.as_message().ok_or(anyhow!("Selected part must be a message/rfc822"))?;
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Ok(ExtractedFull(msg.raw_body.into()))
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}
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// ------------
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/// Returns the structure of the message
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fn structure(&self) -> Result<BodyStructure<'static>> {
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unimplemented!();
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}
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}
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// ---------------------------
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struct SelectedMsg<'a>(&'a SelectedMime<'a>, &'a composite::Message<'a>);
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struct SelectedMult<'a>(&'a SelectedMime<'a>, &'a composite::Multipart<'a>);
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struct SelectedTxt<'a>(&'a SelectedMime<'a>, &'a discrete::Text<'a>);
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struct SelectedBin<'a>(&'a SelectedMime<'a>, &'a discrete::Binary<'a>);
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// ---------------------------
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struct ExtractedFull<'a>(Cow<'a, [u8]>);
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impl<'a> ExtractedFull<'a> {
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/// It is possible to fetch a substring of the designated text.
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/// This is done by appending an open angle bracket ("<"), the
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/// octet position of the first desired octet, a period, the
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/// maximum number of octets desired, and a close angle bracket
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/// (">") to the part specifier. If the starting octet is beyond
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/// the end of the text, an empty string is returned.
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///
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/// Any partial fetch that attempts to read beyond the end of the
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/// text is truncated as appropriate. A partial fetch that starts
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/// at octet 0 is returned as a partial fetch, even if this
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/// truncation happened.
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///
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/// Note: This means that BODY[]<0.2048> of a 1500-octet message
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/// will return BODY[]<0> with a literal of size 1500, not
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/// BODY[].
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///
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/// Note: A substring fetch of a HEADER.FIELDS or
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/// HEADER.FIELDS.NOT part specifier is calculated after
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/// subsetting the header.
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fn to_body_section(self, partial: &'_ Option<(u32, NonZeroU32)>) -> BodySection<'a> {
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match partial {
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Some((begin, len)) => self.partialize(*begin, *len),
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None => BodySection::Full(self.0),
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}
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}
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fn partialize(self, begin: u32, len: NonZeroU32) -> BodySection<'a> {
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// Asked range is starting after the end of the content,
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// returning an empty buffer
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if begin as usize > self.0.len() {
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return BodySection::Slice {
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body: Cow::Borrowed(&[][..]),
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origin_octet: begin,
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}
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}
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// Asked range is ending after the end of the content,
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// slice only the beginning of the buffer
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if (begin + len.get()) as usize >= self.0.len() {
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return BodySection::Slice {
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body: match self.0 {
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Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..]),
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Cow::Owned(body) => Cow::Owned(body[begin as usize..].to_vec()),
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},
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origin_octet: begin,
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}
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}
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// Range is included inside the considered content,
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// this is the "happy case"
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BodySection::Slice {
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body: match self.0 {
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Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..(begin + len.get()) as usize]),
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Cow::Owned(body) => Cow::Owned(body[begin as usize..(begin + len.get()) as usize].to_vec()),
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},
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origin_octet: begin,
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}
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}
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}
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