initial version

src/error.rs

@@ -0,0 +1 @@
+

src/main.rs

@@ -1,3 +1,66 @@
-fn main() {
-    println!("Hello, world!");
+use clap::Parser;
+use crate::product_info::ProductInfoFetcher;
+use main_error::MainResult;
+use serde::Serialize;
+use crate::prefetch::prefetch;
+
+mod product_info;
+mod error;
+mod prefetch;
+
+#[derive(Debug, Parser)]
+struct Args {
+    /// App to prefetch depots for
+    app_id: u32,
+    /// Branch to prefetch, defaults to "public"
+    #[clap(long, default_value_t = String::from("public"))]
+    branch: String,
+    /// Only prefetch the listed depot(s)
+    #[clap(long)]
+    depot: Vec<u32>,
 }
+
+#[tokio::main]
+async fn main() -> MainResult {
+    let args = Args::parse();
+
+    let info_fetcher = ProductInfoFetcher::new().await?;
+    let depots = info_fetcher.fetch_depots(args.app_id).await?;
+
+    let manifests = depots.into_iter()
+        .filter(|(depot_id, _)| args.depot.is_empty() || args.depot.contains(depot_id))
+        .flat_map(|(depot_id, depot)| depot.branches.into_iter().map(move |(branch, manifest)| (depot_id, branch, manifest)))
+        .filter(|(_, branch, _)| &args.branch == branch)
+        .map(|(depot_id, _, manifest)| ManifestInput {
+            app_id: args.app_id,
+            depot_id,
+            manifest: manifest.gid,
+        });
+
+    let outputs = manifests.map(|input| {
+        prefetch(&input).map(|hash| ManifestOutput {
+            app_id: input.app_id,
+            depot_id: input.depot_id,
+            manifest: input.manifest,
+            hash,
+        })
+    }).collect::<Result<Vec<_>, _>>()?;
+
+    serde_json::to_writer_pretty(std::io::stdout(), &outputs)?;
+
+    Ok(())
+}
+
+struct ManifestInput {
+    app_id: u32,
+    depot_id: u32,
+    manifest: u64,
+}
+
+#[derive(Debug, Serialize)]
+struct ManifestOutput {
+    app_id: u32,
+    depot_id: u32,
+    manifest: u64,
+    hash: String,
+}

src/prefetch.rs

@@ -0,0 +1,63 @@
+use crate::ManifestInput;
+use std::process::Command;
+use std::string::FromUtf8Error;
+use thiserror::Error;
+
+const EXPRESSION_TEMPLATE: &str = r#"
+    {
+  pkgs ? import (fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/9ba04bda9249d5d5e5238303c9755de5a49a79c5.tar.gz";
+    sha256 = "sha256-H8J4H2XCIMEJ5g6fZ179QfQvsc2dUqhqfBjC8RAHNRY=";
+  }) {}
+}: let
+  steam-fetcher = pkgs.fetchFromGitHub {
+    owner = "nix-community";
+    repo = "steam-fetcher";
+    rev = "12f66eafb7862d91b3e30c14035f96a21941bd9c";
+    hash = "sha256-PkgC9jqoN6cJ8XYzTA2PlrWs7aPJkM3BGiTxNqax0cA=";
+  };
+  fetchSteam = pkgs.callPackage (steam-fetcher + "/fetch-steam") {};
+in fetchSteam {
+  name = "steam-depot-APP_ID-DEPOT_ID";
+  appId = "APP_ID";
+  depotId = "DEPOT_ID";
+  manifestId = "MANIFEST_ID";
+  hash = "";
+}
+    "#;
+
+pub fn prefetch(manifest: &ManifestInput) -> Result<String, PrefetchError> {
+    let expression = EXPRESSION_TEMPLATE
+        .replace("APP_ID", &manifest.app_id.to_string())
+        .replace("DEPOT_ID", &manifest.depot_id.to_string())
+        .replace("MANIFEST_ID", &manifest.manifest.to_string());
+
+    let command = Command::new("nix-build")
+        .arg("-E")
+        .arg(&expression)
+        .arg("--no-out-link")
+        .output()
+        .map_err(PrefetchError::CommandFailed)?;
+
+    let stderr = String::from_utf8(command.stderr).map_err(PrefetchError::Utf8)?;
+    let Some(line) = stderr.lines().find(|line| line.contains("got:")) else {
+        return Err(PrefetchError::BuildFailed);
+    };
+    let Some(start) = line.find("sha256-") else {
+        return Err(PrefetchError::BuildFailed);
+    };
+    let Some(length) = line[start..].find("=") else {
+        return Err(PrefetchError::BuildFailed);
+    };
+    Ok(line[start..(start + length + 1)].to_string())
+}
+
+#[derive(Debug, Error)]
+pub enum PrefetchError {
+    #[error("Error while running nix-build: {0:#}")]
+    CommandFailed(std::io::Error),
+    #[error("nix-build failed or didn't provide an output hash")]
+    BuildFailed,
+    #[error("nix-build returned non-utf8 output")]
+    Utf8(FromUtf8Error),
+}

src/product_info.rs

@@ -0,0 +1,124 @@
+use serde::Deserialize;
+use std::collections::{BTreeMap, HashMap};
+use std::str::FromStr;
+use std::string::FromUtf8Error;
+use steam_vent::proto::steammessages_clientserver_appinfo::{
+    CMsgClientPICSProductInfoRequest, CMsgClientPICSProductInfoResponse,
+    cmsg_client_picsproduct_info_request,
+};
+use steam_vent::{Connection, ConnectionError, ConnectionTrait, NetworkError, ServerList};
+use thiserror::Error;
+use vdf_reader::VdfError;
+
+pub struct ProductInfoFetcher {
+    connection: Connection,
+}
+
+impl ProductInfoFetcher {
+    pub async fn new() -> Result<ProductInfoFetcher, ProductInfoError> {
+        let server_list = ServerList::discover()
+            .await
+            .map_err(ConnectionError::Discovery)?;
+        let connection = Connection::anonymous(&server_list).await?;
+        Ok(ProductInfoFetcher { connection })
+    }
+
+    pub async fn fetch_depots(
+        &self,
+        app_id: u32,
+    ) -> Result<BTreeMap<u32, Depot>, ProductInfoError> {
+        let msg = CMsgClientPICSProductInfoRequest {
+            apps: vec![cmsg_client_picsproduct_info_request::AppInfo {
+                appid: Some(app_id),
+                only_public_obsolete: Some(true),
+                ..Default::default()
+            }],
+            meta_data_only: Some(false),
+            single_response: Some(true),
+            ..Default::default()
+        };
+
+        let response: CMsgClientPICSProductInfoResponse = self.connection.job(msg).await?;
+        let app_info = response.apps.into_iter().next().unwrap();
+        let mut buffer = app_info.buffer.unwrap_or_default();
+        while buffer.ends_with(&[0]) {
+            let _ = buffer.pop();
+        }
+
+        let raw_vdf = String::from_utf8(buffer)?;
+        let vdf: Response = vdf_reader::from_str(&raw_vdf)?;
+        assert_eq!(app_id, vdf.app_info.app_id);
+
+        Ok(vdf
+            .app_info
+            .depots
+            .depots
+            .into_iter()
+            .filter_map(|(depot_id, depot)| Some((u32::from_str(&depot_id).ok()?, depot)))
+            .collect())
+    }
+}
+
+#[derive(Debug, Deserialize)]
+struct Response {
+    #[serde(rename = "appinfo")]
+    app_info: AppInfo,
+}
+
+#[derive(Debug, Deserialize)]
+struct AppInfo {
+    #[serde(rename = "appid")]
+    app_id: u32,
+    depots: Depots,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Deserialize)]
+struct Depots {
+    overridescddb: bool,
+    branches: HashMap<String, Branch>,
+    #[serde(flatten)]
+    depots: BTreeMap<String, Depot>,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Deserialize)]
+pub struct Depot {
+    #[serde(default)]
+    pub config: DepotConfig,
+    #[serde(rename = "manifests")]
+    pub branches: HashMap<String, Manifest>,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Default, Deserialize)]
+pub struct DepotConfig {
+    pub oslist: Option<String>,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Deserialize)]
+pub struct Manifest {
+    pub gid: u64,
+    pub size: u64,
+    pub download: u64,
+}
+
+#[allow(dead_code)]
+#[derive(Debug, Deserialize)]
+struct Branch {
+    timeupdated: u64,
+    buildid: u64,
+}
+
+#[derive(Debug, Error)]
+pub enum ProductInfoError {
+    #[error("Error while connecting to steam: {0:#}")]
+    Connect(#[from] ConnectionError),
+    #[error("Error while fetching product info from steam: {0:#}")]
+    Steam(#[from] NetworkError),
+    #[error("Steam returned non-utf8 data")]
+    Utf8(#[from] FromUtf8Error),
+    #[error("Error while parsing product info: {0:#}")]
+    Vdf(#[from] VdfError),
+}