1 files changed, 64 insertions, 17 deletions

diff --git a/crates/typst-cli/src/package.rs b/crates/typst-cli/src/package.rs
index 8141ad19..7d3f2264 100644
--- a/crates/typst-cli/src/package.rs
+++ b/crates/typst-cli/src/package.rs
@@ -5,12 +5,16 @@ use std::path::{Path, PathBuf};
 use codespan_reporting::term::{self, termcolor};
 use ecow::eco_format;
 use termcolor::WriteColor;
-use typst::diag::{PackageError, PackageResult};
-use typst::syntax::PackageSpec;
+use typst::diag::{bail, PackageError, PackageResult, StrResult};
+use typst::syntax::package::{
+    PackageInfo, PackageSpec, PackageVersion, VersionlessPackageSpec,
+};
 
-use crate::download::download_with_progress;
+use crate::download::{download, download_with_progress};
 use crate::terminal;
 
+const HOST: &str = "https://packages.typst.org";
+
 /// Make a package available in the on-disk cache.
 pub fn prepare_package(spec: &PackageSpec) -> PackageResult<PathBuf> {
     let subdir =
@@ -25,30 +29,59 @@ pub fn prepare_package(spec: &PackageSpec) -> PackageResult<PathBuf> {
 
     if let Some(cache_dir) = dirs::cache_dir() {
         let dir = cache_dir.join(&subdir);
+        if dir.exists() {
+            return Ok(dir);
+        }
 
         // Download from network if it doesn't exist yet.
-        if spec.namespace == "preview" && !dir.exists() {
+        if spec.namespace == "preview" {
             download_package(spec, &dir)?;
-        }
-
-        if dir.exists() {
-            return Ok(dir);
+            if dir.exists() {
+                return Ok(dir);
+            }
         }
     }
 
     Err(PackageError::NotFound(spec.clone()))
 }
 
+/// Try to determine the latest version of a package.
+pub fn determine_latest_version(
+    spec: &VersionlessPackageSpec,
+) -> StrResult<PackageVersion> {
+    if spec.namespace == "preview" {
+        // For `@preview`, download the package index and find the latest
+        // version.
+        download_index()?
+            .iter()
+            .filter(|package| package.name == spec.name)
+            .map(|package| package.version)
+            .max()
+            .ok_or_else(|| eco_format!("failed to find package {spec}"))
+    } else {
+        // For other namespaces, search locally. We only search in the data
+        // directory and not the cache directory, because the latter is not
+        // intended for storage of local packages.
+        let subdir = format!("typst/packages/{}/{}", spec.namespace, spec.name);
+        dirs::data_dir()
+            .into_iter()
+            .flat_map(|dir| std::fs::read_dir(dir.join(&subdir)).ok())
+            .flatten()
+            .filter_map(|entry| entry.ok())
+            .map(|entry| entry.path())
+            .filter_map(|path| path.file_name()?.to_string_lossy().parse().ok())
+            .max()
+            .ok_or_else(|| eco_format!("please specify the desired version"))
+    }
+}
+
 /// Download a package over the network.
 fn download_package(spec: &PackageSpec, package_dir: &Path) -> PackageResult<()> {
     // The `@preview` namespace is the only namespace that supports on-demand
     // fetching.
     assert_eq!(spec.namespace, "preview");
 
-    let url = format!(
-        "https://packages.typst.org/preview/{}-{}.tar.gz",
-        spec.name, spec.version
-    );
+    let url = format!("{HOST}/preview/{}-{}.tar.gz", spec.name, spec.version);
 
     print_downloading(spec).unwrap();
 
@@ -67,14 +100,28 @@ fn download_package(spec: &PackageSpec, package_dir: &Path) -> PackageResult<()>
     })
 }
 
+/// Download the `@preview` package index.
+fn download_index() -> StrResult<Vec<PackageInfo>> {
+    let url = format!("{HOST}/preview/index.json");
+    match download(&url) {
+        Ok(response) => response
+            .into_json()
+            .map_err(|err| eco_format!("failed to parse package index: {err}")),
+        Err(ureq::Error::Status(404, _)) => {
+            bail!("failed to fetch package index (not found)")
+        }
+        Err(err) => bail!("failed to fetch package index ({err})"),
+    }
+}
+
 /// Print that a package downloading is happening.
 fn print_downloading(spec: &PackageSpec) -> io::Result<()> {
     let styles = term::Styles::default();
 
-    let mut term_out = terminal::out();
-    term_out.set_color(&styles.header_help)?;
-    write!(term_out, "downloading")?;
+    let mut out = terminal::out();
+    out.set_color(&styles.header_help)?;
+    write!(out, "downloading")?;
 
-    term_out.reset()?;
-    writeln!(term_out, " {spec}")
+    out.reset()?;
+    writeln!(out, " {spec}")
 }