241 lines
9.1 KiB
Rust
241 lines
9.1 KiB
Rust
/// External linking is a complex implementation to be able to serve a clean and easy-to-use
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/// interface.
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///
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/// Internally, there are no such things as "external links" (plural). Each Entry in the store can
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/// only have _one_ external link.
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///
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/// This library does the following therefor: It allows you to have several external links with one
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/// entry, which are internally one file in the store for each link, linked with "internal
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/// linking".
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///
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/// This helps us greatly with deduplication of URLs.
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///
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use std::ops::DerefMut;
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use std::collections::BTreeMap;
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use libimagstore::store::Entry;
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use libimagstore::store::FileLockEntry;
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use libimagstore::store::Store;
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use libimagstore::storeid::StoreId;
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use libimagstore::storeid::IntoStoreId;
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use error::LinkError as LE;
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use error::LinkErrorKind as LEK;
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use result::Result;
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use internal::InternalLinker;
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use module_path::ModuleEntryPath;
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use toml::Value;
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use url::Url;
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use crypto::sha1::Sha1;
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use crypto::digest::Digest;
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/// "Link" Type, just an abstraction over FileLockEntry to have some convenience internally.
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struct Link<'a> {
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link: FileLockEntry<'a>
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}
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impl<'a> Link<'a> {
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pub fn new(fle: FileLockEntry<'a>) -> Link<'a> {
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Link { link: fle }
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}
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/// For interal use only. Load an Link from a store id, if this is actually a Link
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fn retrieve(store: &'a Store, id: StoreId) -> Result<Option<Link<'a>>> {
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store.retrieve(id)
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.map(|fle| {
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if let Some(_) = Link::get_link_uri_from_filelockentry(&fle) {
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Some(Link {
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link: fle
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})
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} else {
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None
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}
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})
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.map_err(|e| LE::new(LEK::StoreReadError, Some(Box::new(e))))
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}
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/// Get a link Url object from a FileLockEntry, ignore errors.
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fn get_link_uri_from_filelockentry(file: &FileLockEntry<'a>) -> Option<Url> {
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file.get_header()
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.read("imag.content.uri")
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.ok()
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.and_then(|opt| {
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match opt {
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Some(Value::String(s)) => Url::parse(&s[..]).ok(),
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_ => None
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}
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})
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}
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pub fn get_url(&self) -> Result<Option<Url>> {
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let opt = self.link
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.get_header()
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.read("imag.content.uri");
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match opt {
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Ok(Some(Value::String(s))) => {
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Url::parse(&s[..])
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.map(|s| Some(s))
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.map_err(|e| LE::new(LEK::EntryHeaderReadError, Some(Box::new(e))))
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},
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Ok(None) => Ok(None),
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_ => Err(LE::new(LEK::EntryHeaderReadError, None))
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}
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}
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}
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pub trait ExternalLinker : InternalLinker {
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/// Get the external links from the implementor object
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fn get_external_links(&self, store: &Store) -> Result<Vec<Url>>;
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/// Set the external links for the implementor object
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fn set_external_links(&mut self, store: &Store, links: Vec<Url>) -> Result<()>;
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/// Add an external link to the implementor object
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fn add_external_link(&mut self, store: &Store, link: Url) -> Result<()>;
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/// Remove an external link from the implementor object
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fn remove_external_link(&mut self, store: &Store, link: Url) -> Result<()>;
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}
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/// Check whether the StoreId starts with `/link/external/`
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fn is_link_store_id(id: &StoreId) -> bool {
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debug!("Checking whether this is a /link/external/*: '{:?}'", id);
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id.starts_with("/link/external/")
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}
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fn get_external_link_from_file(entry: &FileLockEntry) -> Result<Url> {
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Link::get_link_uri_from_filelockentry(entry) // TODO: Do not hide error by using this function
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.ok_or(LE::new(LEK::StoreReadError, None))
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}
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/// Implement ExternalLinker for Entry, hiding the fact that there is no such thing as an external
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/// link in an entry, but internal links to other entries which serve as external links, as one
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/// entry in the store can only have one external link.
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impl ExternalLinker for Entry {
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/// Get the external links from the implementor object
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fn get_external_links(&self, store: &Store) -> Result<Vec<Url>> {
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// Iterate through all internal links and filter for FileLockEntries which live in
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// /link/external/<SHA> -> load these files and get the external link from their headers,
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// put them into the return vector.
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self.get_internal_links()
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.map(|vect| {
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debug!("Getting external links");
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vect.into_iter()
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.filter(is_link_store_id)
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.map(|id| {
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debug!("Retrieving entry for id: '{:?}'", id);
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match store.retrieve(id.clone()) {
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Ok(f) => get_external_link_from_file(&f),
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Err(e) => {
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debug!("Retrieving entry for id: '{:?}' failed", id);
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Err(LE::new(LEK::StoreReadError, Some(Box::new(e))))
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}
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}
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})
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.filter_map(|x| x.ok()) // TODO: Do not ignore error here
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.collect()
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})
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.map_err(|e| LE::new(LEK::StoreReadError, Some(Box::new(e))))
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}
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/// Set the external links for the implementor object
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fn set_external_links(&mut self, store: &Store, links: Vec<Url>) -> Result<()> {
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// Take all the links, generate a SHA sum out of each one, filter out the already existing
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// store entries and store the other URIs in the header of one FileLockEntry each, in
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// the path /link/external/<SHA of the URL>
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debug!("Iterating {} links = {:?}", links.len(), links);
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for link in links { // for all links
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let hash = {
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let mut s = Sha1::new();
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s.input_str(&link.serialize()[..]);
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s.result_str()
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};
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let file_id = ModuleEntryPath::new(format!("external/{}", hash)).into_storeid();
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debug!("Link = '{:?}'", link);
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debug!("Hash = '{:?}'", hash);
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debug!("StoreId = '{:?}'", file_id);
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// retrieve the file from the store, which implicitely creates the entry if it does not
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// exist
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let file = store.retrieve(file_id.clone());
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if file.is_err() {
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debug!("Failed to create or retrieve an file for this link '{:?}'", link);
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return Err(LE::new(LEK::StoreWriteError, Some(Box::new(file.unwrap_err()))));
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}
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let mut file = file.unwrap();
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debug!("Generating header content!");
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{
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let mut hdr = file.deref_mut().get_header_mut();
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let mut table = match hdr.read("imag.content") {
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Ok(Some(Value::Table(table))) => table,
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Ok(Some(_)) => {
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warn!("There is a value at 'imag.content' which is not a table.");
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warn!("Going to override this value");
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BTreeMap::new()
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},
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Ok(None) => BTreeMap::new(),
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Err(e) => return Err(LE::new(LEK::StoreWriteError, Some(Box::new(e)))),
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};
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let v = Value::String(link.serialize());
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debug!("setting URL = '{:?}", v);
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table.insert(String::from("url"), v);
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if let Err(e) = hdr.set("imag.content", Value::Table(table)) {
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return Err(LE::new(LEK::StoreWriteError, Some(Box::new(e))));
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} else {
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debug!("Setting URL worked");
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}
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}
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// then add an internal link to the new file or return an error if this fails
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if let Err(e) = self.add_internal_link(file.deref_mut()) {
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debug!("Error adding internal link");
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return Err(LE::new(LEK::StoreWriteError, Some(Box::new(e))));
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}
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}
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debug!("Ready iterating");
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Ok(())
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}
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/// Add an external link to the implementor object
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fn add_external_link(&mut self, store: &Store, link: Url) -> Result<()> {
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// get external links, add this one, save them
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debug!("Getting links");
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self.get_external_links(store)
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.and_then(|mut links| {
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debug!("Adding link = '{:?}' to links = {:?}", link, links);
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links.push(link);
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debug!("Setting {} links = {:?}", links.len(), links);
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self.set_external_links(store, links)
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})
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}
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/// Remove an external link from the implementor object
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fn remove_external_link(&mut self, store: &Store, link: Url) -> Result<()> {
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// get external links, remove this one, save them
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self.get_external_links(store)
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.and_then(|links| {
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debug!("Removing link = '{:?}' from links = {:?}", link, links);
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let links = links.into_iter()
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.filter(|l| l.serialize() != link.serialize())
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.collect();
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self.set_external_links(store, links)
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})
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}
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}
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