implement url templates

in addition to url templates, this also includes special handling for crates.io:

crates.io index config.json dl: "https://crates.io/api/v1/crates"

request to "https://crates.io/api/v1/crates/{crate}/{vers}/download" will
return a 302 redirect to "https://static.crates.io/crates/{crate}/{crate}-{vers}.crate".

rather than follow the 302, this detects if the dl value is crates.io (`is_crates_io` method)
and performs the redirect preemptively.

in discussion with crates.io team on discord, @carol10cents indicated this would
avoid need to throttle requests as they would go right to cdn instead of
hitting crates.io webserver.

Cargo.lock

@@ -1323,7 +1323,7 @@ checksum = "a3f87b73ce11b1619a3c6332f45341e0047173771e8b8b73f87bfeefb7b56244"
 
 [[package]]
 name = "registry-backup"
-version = "0.3.0"
+version = "0.4.0-rc.1"
 dependencies = [
  "chrono",
  "clap",
@@ -1341,6 +1341,7 @@ dependencies = [
  "toml",
  "tracing",
  "tracing-subscriber",
+ "url",
  "walkdir",
 ]
 

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "registry-backup"
 authors = ["Jonathan Strong <jstrong@shipyard.rs>"]
-version = "0.3.0"
+version = "0.4.0-rc.1"
 edition = "2021"
 publish = ["shipyard-rs-public"]
 readme = "README.md"
@@ -38,6 +38,7 @@ pretty_toa = "1"
 tera = { version = "1", optional = true }
 chrono = { version = "0.4", optional = true }
 regex = "1.6"
+url = "2"
 
 [features]
 default = []

src/main.rs

@@ -12,7 +12,7 @@ use clap::Parser;
 use futures::stream::StreamExt;
 use governor::prelude::*;
 use governor::{Quota, RateLimiter};
-use reqwest::header::{ACCEPT, AUTHORIZATION, CONTENT_TYPE};
+use reqwest::header::AUTHORIZATION; // ACCEPT, CONTENT_TYPE};
 use serde::Deserialize;
 use tokio::io::AsyncBufReadExt;
 use tracing::{debug, error, info, warn};
@@ -20,6 +20,9 @@ use tracing_subscriber::filter::EnvFilter;
 
 type AnyError = Box<dyn std::error::Error>;
 
+// const CRATESIO_INDEX: &str = "https://github.com/rust-lang/crates.io-index.git";
+const CRATESIO_DL_URL: &str = "https://crates.io/api/v1/crates";
+
 /// type representing the schema of the config.json file
 /// placed at the root of the crate index repo.
 ///
@@ -43,11 +46,62 @@ pub struct RegistryConfig {
     pub auth_required: Option<bool>,
 }
 
+impl RegistryConfig {
+    pub fn is_crates_io(&self) -> bool {
+        self.dl == CRATESIO_DL_URL
+    }
+
+    pub fn get_dl_url(&self, name: &str, version: &str, cksum: &str) -> String {
+        const TEMPLATE_KEYS: [&str; 5] = [
+            "{crate}",
+            "{version}",
+            "{prefix}",
+            "{lowerprefix}",
+            "{sha256-checksum}",
+        ];
+
+        if self.is_crates_io() {
+            // instead of following 302 redirect from /api endpoint, just preemptively
+            // get the static cdn url
+            format!(
+                "https://static.crates.io/crates/{name}/{name}-{version}.crate",
+                name = name,
+                version = version,
+            )
+        } else if TEMPLATE_KEYS.iter().any(|k| self.dl.contains(k)) {
+            let mut out = self.dl.clone();
+
+            if self.dl.contains("{prefix}") {
+                let prefix = relative_index_file_helper(name).join("/");
+                out = out.replace("{prefix}", &prefix);
+            }
+
+            if self.dl.contains("{lowerprefix}") {
+                let prefix = relative_index_file_helper(&name.to_lowercase()).join("/");
+                out = out.replace("{lowerprefix}", &prefix);
+            }
+
+            out = out.replace("{crate}", name);
+            out = out.replace("{version}", version);
+            out = out.replace("{sha256-checksum}", cksum);
+            out
+        } else {
+            format!(
+                "{dl}/{name}/{version}/download",
+                dl = self.dl,
+                name = name,
+                version = version,
+            )
+        }
+    }
+}
+
 /// One version per line in the index metadata files.
 #[derive(Debug, Clone, Deserialize)]
 pub struct CrateVersion {
     pub name: String,
     pub vers: String,
+    pub cksum: String,
 }
 
 /// Configuration for where to save the downloaded .crate files, and
@@ -175,8 +229,6 @@ pub struct Config {
 const DEFAULT_OUTPUT_PATH: &str = "output";
 const DEFAULT_USER_AGENT: &str = concat!("registry-backup/v", clap::crate_version!());
 
-//const CRATESIO_INDEX: &str = "https://github.com/rust-lang/crates.io-index.git";
-
 fn default_output_path() -> PathBuf {
     PathBuf::from(DEFAULT_OUTPUT_PATH)
 }
@@ -487,6 +539,37 @@ async fn ensure_file_parent_dir_exists<P: AsRef<std::path::Path>>(path: P) -> Re
     }
 }
 
+// relative_index_* fns taken from rust-lang/crates.io source code
+
+/// Returns the relative path to the crate index file.
+/// Does not perform conversion to lowercase.
+fn relative_index_file_helper(name: &str) -> Vec<&str> {
+    match name.len() {
+        1 => vec!["1", name],
+        2 => vec!["2", name],
+        3 => vec!["3", &name[..1], name],
+        _ => vec![&name[0..2], &name[2..4], name],
+    }
+}
+
+// /// Returns the relative path to the crate index file that corresponds to
+// /// the given crate name as a path (i.e. with platform-dependent folder separators).
+// ///
+// /// see <https://doc.rust-lang.org/cargo/reference/registries.html#index-format>
+// fn relative_index_file(name: &str) -> PathBuf {
+//     let name = name.to_lowercase();
+//     Self::relative_index_file_helper(&name).iter().collect()
+// }
+//
+// /// Returns the relative path to the crate index file that corresponds to
+// /// the given crate name for usage in URLs (i.e. with `/` separator).
+// ///
+// /// see <https://doc.rust-lang.org/cargo/reference/registries.html#index-format>
+// fn relative_index_file_for_url(name: &str) -> String {
+//     let name = name.to_lowercase();
+//     Self::relative_index_file_helper(&name).join("/")
+// }
+
 macro_rules! megabytes {
     ($x:expr) => {{
         use pretty_toa::ThousandsSep;
@@ -532,9 +615,9 @@ async fn download_versions(
 
         async move {
             // TODO actually parse and use the format
-            let vers_path = format!("{}/{}/download", vers.name, vers.vers);
-            let url = format!("{}/{}", registry_config.dl, vers_path);
-            let output_path = config.output.path.join(vers_path);
+            let url =
+                url::Url::parse(&registry_config.get_dl_url(&vers.name, &vers.vers, &vers.cksum))?;
+            let output_path = config.output.path.join(url.path());
 
             if config.dry_run {
                 debug!(%url, "skipping download (--dry-run mode)");
@@ -542,11 +625,7 @@ async fn download_versions(
             }
 
             debug!(?url, "downloading...");
-            let req = http_client
-                .get(url)
-                //.header(CONTENT_TYPE, "application/json")
-                //.header(ACCEPT, "application/json")
-                ;
+            let req = http_client.get(url);
 
             let req = if let Some(token) = config.registry.auth_token.as_deref() {
                 req.header(AUTHORIZATION, token)
@@ -687,4 +766,19 @@ mod tests {
         const TOML: &str = include_str!("../config.toml.sample");
         let _config: Config = toml::from_str(TOML).unwrap();
     }
+
+    #[test]
+    fn sanity_check_url_template_rendering() {
+        let config = RegistryConfig {
+            dl: "{prefix}__{lowerprefix}__{sha256-checksum}__{crate}__{version}.tar.gz".to_string(),
+            api: String::new(),
+            allowed_registries: vec![],
+            auth_required: Some(true),
+        };
+
+        assert_eq!(
+            config.get_dl_url("iM-14yo-LoL", "0.69.42-rc.123", "c5b6fc73"),
+            "iM/-1/iM-14yo-LoL__im/-1/im-14yo-lol__c5b6fc73__iM-14yo-LoL__0.69.42-rc.123.tar.gz",
+        );
+    }
 }