Add a torrent from-link subcommand

It is now possible to create a torrent file from a magnet link. The
search is performed with minimal concurrency, and so may take a while to
complete.

type: added
fixes: casey#255

Cargo.toml

@@ -33,6 +33,7 @@ rand              = "0.7.3"
 open              = "1.4.0"
 pretty_assertions = "0.6.0"
 pretty_env_logger = "0.4.0"
+rayon             = "<=1.6.0"
 regex             = "1.0.0"
 serde-hex         = "0.1.0"
 serde_bytes       = "0.11.0"

bin/gen/config.yaml

@@ -19,6 +19,10 @@ examples:
   text:    "Intermodal can be used to create `.torrent` files:"
   code:    "imdl torrent create --input foo"
 
+- command: imdl torrent from-link
+  text:    "Intermodal can be used to create a `.torrent` file from a magnet link:"
+  code:    "imdl torrent from-link magnet:?foo"
+
 - command: imdl torrent show
   text:    "Print information about existing `.torrent` files:"
   code:    "imdl torrent show --input foo.torrent"

src/common.rs

@@ -19,7 +19,7 @@ pub(crate) use std::{
   process::ExitStatus,
   str::{self, FromStr},
   string::FromUtf8Error,
-  sync::Once,
+  sync::{mpsc::channel, Once},
   time::{Duration, SystemTime, SystemTimeError},
   usize,
 };
@@ -94,6 +94,7 @@ mod test {
     ops::{Deref, DerefMut},
     process::Command,
     rc::Rc,
+    thread,
   };
 
   // test dependencies

src/error.rs

@@ -30,6 +30,8 @@ pub(crate) enum Error {
   Filesystem { source: io::Error, path: PathBuf },
   #[snafu(display("Error searching for files: {}", source))]
   FileSearch { source: ignore::Error },
+  #[snafu(display("Failed to fetch infodict from accessible peers"))]
+  FromLinkNoInfo,
   #[snafu(display("Invalid glob: {}", source))]
   GlobParse { source: globset::Error },
   #[snafu(display("Failed to serialize torrent info dictionary: {}", source))]

src/magnet_link.rs

@@ -1,12 +1,12 @@
 use crate::common::*;
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub(crate) struct MagnetLink {
-  infohash: Infohash,
-  name: Option<String>,
-  peers: Vec<HostPort>,
-  trackers: Vec<Url>,
-  indices: BTreeSet<u64>,
+  pub(crate) infohash: Infohash,
+  pub(crate) name: Option<String>,
+  pub(crate) peers: Vec<HostPort>,
+  pub(crate) trackers: Vec<Url>,
+  pub(crate) indices: BTreeSet<u64>,
 }
 
 impl MagnetLink {

src/subcommand/torrent.rs

@@ -2,6 +2,7 @@ use crate::common::*;
 
 mod announce;
 mod create;
+mod from_link;
 mod link;
 mod piece_length;
 mod show;
@@ -17,6 +18,7 @@ mod verify;
 pub(crate) enum Torrent {
   Announce(announce::Announce),
   Create(create::Create),
+  FromLink(from_link::FromLink),
   Link(link::Link),
   #[structopt(alias = "piece-size")]
   PieceLength(piece_length::PieceLength),
@@ -30,6 +32,7 @@ impl Torrent {
     match self {
       Self::Announce(announce) => announce.run(env),
       Self::Create(create) => create.run(env, options),
+      Self::FromLink(from_link) => from_link.run(env, options),
       Self::Link(link) => link.run(env),
       Self::PieceLength(piece_length) => piece_length.run(env),
       Self::Show(show) => show.run(env),

src/subcommand/torrent/announce.rs

@@ -60,7 +60,7 @@ impl Announce {
         }
       };
 
-      let client = match tracker::Client::from_url(tracker_url) {
+      let client = match tracker::Client::from_url(&tracker_url) {
         Ok(client) => client,
         Err(err) => {
           errln!(env, "Couldn't build tracker client. {}", err)?;
@@ -69,7 +69,7 @@ impl Announce {
       };
 
       usable_trackers += 1;
-      match client.announce_exchange(infohash) {
+      match client.announce_exchange(&infohash) {
         Ok(peer_list) => peers.extend(peer_list),
         Err(err) => errln!(env, "Announce failed: {}", err)?,
       }