imag/libimagentrylink/src/external.rs

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