diff --git a/crates/puffin-cli/Cargo.toml b/crates/puffin-cli/Cargo.toml
index e4df72004..bc0509b8e 100644
--- a/crates/puffin-cli/Cargo.toml
+++ b/crates/puffin-cli/Cargo.toml
@@ -20,3 +20,7 @@ async-std = { version = "1.12.0", features = [
 ] }
 futures = "0.3.28"
 pep508_rs = "0.2.3"
+pep440_rs = "0.3.12"
+tracing = "0.1.37"
+tracing-tree = "0.2.5"
+tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }
diff --git a/crates/puffin-cli/src/commands/install.rs b/crates/puffin-cli/src/commands/install.rs
index 897279569..ab16703cf 100644
--- a/crates/puffin-cli/src/commands/install.rs
+++ b/crates/puffin-cli/src/commands/install.rs
@@ -1,17 +1,35 @@
+use std::collections::{HashMap, HashSet};
 use std::path::Path;
 use std::str::FromStr;
 
 use anyhow::Result;
 use futures::{StreamExt, TryFutureExt};
-use pep508_rs::VersionOrUrl;
+use pep440_rs::Version;
+use pep508_rs::{MarkerEnvironment, Requirement, StringVersion, VersionOrUrl};
+use tracing::trace;
 
 use puffin_client::{PypiClientBuilder, SimpleJson};
+use puffin_requirements::package_name::PackageName;
 use puffin_requirements::wheel::WheelName;
-use puffin_requirements::Requirement;
 
 use crate::commands::ExitStatus;
 
 pub(crate) async fn install(src: &Path) -> Result<ExitStatus> {
+    // TODO(charlie): Fetch from the environment.
+    let env = MarkerEnvironment {
+        implementation_name: String::new(),
+        implementation_version: StringVersion::from_str("3.10.0").unwrap(),
+        os_name: String::new(),
+        platform_machine: String::new(),
+        platform_python_implementation: String::new(),
+        platform_release: String::new(),
+        platform_system: String::new(),
+        platform_version: String::new(),
+        python_full_version: StringVersion::from_str("3.10.0").unwrap(),
+        python_version: StringVersion::from_str("3.10.0").unwrap(),
+        sys_platform: String::new(),
+    };
+
     // Read the `requirements.txt` from disk.
     let requirements_txt = std::fs::read_to_string(src)?;
 
@@ -24,6 +42,8 @@ pub(crate) async fn install(src: &Path) -> Result<ExitStatus> {
     // Fetch metadata in parallel.
     let (package_sink, package_stream) = futures::channel::mpsc::unbounded();
 
+    let mut resolution: HashMap<PackageName, Version> = HashMap::with_capacity(requirements.len());
+
     // Create a stream of futures that fetch metadata for each requirement.
     let mut package_stream = package_stream
         .map(|requirement: Requirement| {
@@ -31,28 +51,32 @@ pub(crate) async fn install(src: &Path) -> Result<ExitStatus> {
                 .simple(requirement.name.clone())
                 .map_ok(move |metadata| (metadata, requirement))
         })
-        .buffer_unordered(32)
-        .ready_chunks(32);
+        .buffer_unordered(48)
+        .ready_chunks(48);
 
     // Push all the requirements into the sink.
-    let mut in_flight = 0;
+    let mut in_flight: HashSet<PackageName> = HashSet::with_capacity(requirements.len());
     for requirement in requirements.iter() {
         package_sink.unbounded_send(requirement.clone())?;
-        in_flight += 1;
+        in_flight.insert(PackageName::normalize(&requirement.name));
     }
 
     while let Some(chunk) = package_stream.next().await {
-        in_flight -= chunk.len();
         for result in chunk {
             let (metadata, requirement): (SimpleJson, Requirement) = result?;
 
+            // Remove this requirement from the in-flight set.
+            let normalized_name = PackageName::normalize(&requirement.name);
+            in_flight.remove(&normalized_name);
+
             // TODO(charlie): Support URLs. Right now, we treat a URL as an unpinned dependency.
-            let specifiers = requirement.version_or_url.and_then(|version_or_url| {
-                match version_or_url {
+            let specifiers = requirement
+                .version_or_url
+                .as_ref()
+                .and_then(|version_or_url| match version_or_url {
                     VersionOrUrl::VersionSpecifier(specifiers) => Some(specifiers),
                     VersionOrUrl::Url(_) => None,
-                }
-            });
+                });
 
             // Pick a version that satisfies the requirement.
             let Some(file) = metadata.files.iter().rev().find(|file| {
@@ -68,16 +92,61 @@ pub(crate) async fn install(src: &Path) -> Result<ExitStatus> {
                 continue;
             };
 
-            #[allow(clippy::print_stdout)]
-            {
-                println!("{}: {:?}", requirement.name, file);
+            // Fetch the metadata for this specific version.
+            let metadata = client.file(file).await?;
+            trace!(
+                "Selecting {version} for {requirement}",
+                version = metadata.version,
+                requirement = requirement
+            );
+
+            // Add to the resolved set.
+            let normalized_name = PackageName::normalize(&requirement.name);
+            resolution.insert(normalized_name, metadata.version);
+
+            // Enqueue its dependencies.
+            for dependency in metadata.requires_dist {
+                if !dependency
+                    .evaluate_markers(&env, requirement.extras.clone().unwrap_or_default())
+                {
+                    trace!("Ignoring {dependency} because it doesn't match the environment");
+                    continue;
+                }
+
+                if dependency
+                    .extras
+                    .as_ref()
+                    .is_some_and(|extras| !extras.is_empty())
+                {
+                    trace!("Ignoring {dependency} because it has extras");
+                    continue;
+                }
+
+                let normalized_name = PackageName::normalize(&dependency.name);
+                if resolution.contains_key(&normalized_name) {
+                    continue;
+                }
+
+                if !in_flight.insert(normalized_name) {
+                    continue;
+                }
+
+                trace!("Enqueueing {dependency}");
+                package_sink.unbounded_send(dependency)?;
             }
         }
 
-        if in_flight == 0 {
+        if in_flight.is_empty() {
             break;
         }
     }
 
+    for (name, version) in resolution {
+        #[allow(clippy::print_stdout)]
+        {
+            println!("{name}=={version}");
+        }
+    }
+
     Ok(ExitStatus::Success)
 }
diff --git a/crates/puffin-cli/src/logging.rs b/crates/puffin-cli/src/logging.rs
new file mode 100644
index 000000000..3931cf290
--- /dev/null
+++ b/crates/puffin-cli/src/logging.rs
@@ -0,0 +1,20 @@
+use anyhow::Result;
+use tracing_subscriber::layer::SubscriberExt;
+use tracing_subscriber::{EnvFilter, Layer, Registry};
+use tracing_tree::time::Uptime;
+
+pub(crate) fn setup_logging() -> Result<()> {
+    let subscriber = Registry::default().with(
+        tracing_tree::HierarchicalLayer::default()
+            .with_indent_lines(true)
+            .with_indent_amount(2)
+            .with_bracketed_fields(true)
+            .with_targets(true)
+            .with_writer(|| Box::new(std::io::stderr()))
+            .with_timer(Uptime::default())
+            .with_filter(EnvFilter::from_default_env()),
+    );
+    tracing::subscriber::set_global_default(subscriber)?;
+
+    Ok(())
+}
diff --git a/crates/puffin-cli/src/main.rs b/crates/puffin-cli/src/main.rs
index 798f29994..1615d3011 100644
--- a/crates/puffin-cli/src/main.rs
+++ b/crates/puffin-cli/src/main.rs
@@ -7,6 +7,7 @@ use colored::Colorize;
 use crate::commands::ExitStatus;
 
 mod commands;
+mod logging;
 
 #[derive(Parser)]
 #[command(author, version, about)]
@@ -32,6 +33,8 @@ struct InstallArgs {
 async fn main() -> ExitCode {
     let cli = Cli::parse();
 
+    let _ = logging::setup_logging();
+
     let result = match &cli.command {
         Commands::Install(install) => commands::install(&install.src).await,
     };
diff --git a/crates/puffin-client/Cargo.toml b/crates/puffin-client/Cargo.toml
index b6c5924a9..59eb01d79 100644
--- a/crates/puffin-client/Cargo.toml
+++ b/crates/puffin-client/Cargo.toml
@@ -6,11 +6,13 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-http-cache-reqwest = "0.11.3"
+puffin-requirements = { path = "../puffin-requirements" }
+
+http-cache-reqwest = { version = "0.11.3" }
 reqwest = { version = "0.11.22", features = ["json", "gzip", "stream"] }
-reqwest-middleware = "0.2.3"
-reqwest-retry = "0.3.0"
-serde = "1.0.188"
-serde_json = "1.0.107"
+reqwest-middleware = { version = "0.2.3" }
+reqwest-retry = { version = "0.3.0" }
+serde = { version = "1.0.188" }
+serde_json = { version = "1.0.107" }
 thiserror = { version = "1.0.49" }
 url = { version = "2.4.1" }
diff --git a/crates/puffin-client/src/api/mod.rs b/crates/puffin-client/src/api.rs
similarity index 63%
rename from crates/puffin-client/src/api/mod.rs
rename to crates/puffin-client/src/api.rs
index eced665d6..85dcfe9a7 100644
--- a/crates/puffin-client/src/api/mod.rs
+++ b/crates/puffin-client/src/api.rs
@@ -2,8 +2,11 @@ use reqwest::StatusCode;
 use serde::{Deserialize, Serialize};
 use url::Url;
 
+use puffin_requirements::metadata::Metadata21;
+use puffin_requirements::package_name::PackageName;
+
+use crate::client::PypiClient;
 use crate::error::PypiClientError;
-use crate::PypiClient;
 
 impl PypiClient {
     pub async fn simple(
@@ -12,7 +15,9 @@ impl PypiClient {
     ) -> Result<SimpleJson, PypiClientError> {
         // Format the URL for PyPI.
         let mut url = self.registry.join("simple")?;
-        url.path_segments_mut().unwrap().push(package_name.as_ref());
+        url.path_segments_mut()
+            .unwrap()
+            .push(PackageName::normalize(&package_name).as_ref());
         url.path_segments_mut().unwrap().push("");
         url.set_query(Some("format=application/vnd.pypi.simple.v1+json"));
 
@@ -46,6 +51,44 @@ impl PypiClient {
             .text()
             .await?)
     }
+
+    pub async fn file(&self, file: &File) -> Result<Metadata21, PypiClientError> {
+        // Send to the proxy.
+        let url = self.proxy.join(
+            file.url
+                .strip_prefix("https://files.pythonhosted.org/")
+                .unwrap(),
+        )?;
+
+        // Fetch from the registry.
+        let text = self.file_impl(&file.filename, &url).await?;
+        Metadata21::parse(text.as_bytes()).map_err(std::convert::Into::into)
+    }
+
+    async fn file_impl(
+        &self,
+        filename: impl AsRef<str>,
+        url: &Url,
+    ) -> Result<String, PypiClientError> {
+        Ok(self
+            .client
+            .get(url.clone())
+            .send()
+            .await?
+            .error_for_status()
+            .map_err(|err| {
+                if err.status() == Some(StatusCode::NOT_FOUND) {
+                    PypiClientError::FileNotFound(
+                        (*self.registry).clone(),
+                        filename.as_ref().to_string(),
+                    )
+                } else {
+                    PypiClientError::RequestError(err)
+                }
+            })?
+            .text()
+            .await?)
+    }
 }
 
 #[derive(Debug, Serialize, Deserialize)]
diff --git a/crates/puffin-client/src/client.rs b/crates/puffin-client/src/client.rs
new file mode 100644
index 000000000..c8e1ac4d6
--- /dev/null
+++ b/crates/puffin-client/src/client.rs
@@ -0,0 +1,92 @@
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+use http_cache_reqwest::{CACacheManager, Cache, CacheMode, HttpCache, HttpCacheOptions};
+use reqwest::ClientBuilder;
+use reqwest_middleware::ClientWithMiddleware;
+use reqwest_retry::policies::ExponentialBackoff;
+use reqwest_retry::RetryTransientMiddleware;
+use url::Url;
+
+#[derive(Debug, Clone)]
+pub struct PypiClientBuilder {
+    registry: Url,
+    proxy: Url,
+    retries: u32,
+    cache: Option<PathBuf>,
+}
+
+impl Default for PypiClientBuilder {
+    fn default() -> Self {
+        Self {
+            registry: Url::parse("https://pypi.org").unwrap(),
+            proxy: Url::parse("https://pypi-metadata.ruff.rs").unwrap(),
+            cache: None,
+            retries: 0,
+        }
+    }
+}
+
+impl PypiClientBuilder {
+    #[must_use]
+    pub fn registry(mut self, registry: Url) -> Self {
+        self.registry = registry;
+        self
+    }
+
+    #[must_use]
+    pub fn proxy(mut self, proxy: Url) -> Self {
+        self.proxy = proxy;
+        self
+    }
+
+    #[must_use]
+    pub fn retries(mut self, retries: u32) -> Self {
+        self.retries = retries;
+        self
+    }
+
+    #[must_use]
+    pub fn cache(mut self, cache: impl AsRef<Path>) -> Self {
+        self.cache = Some(PathBuf::from(cache.as_ref()));
+        self
+    }
+
+    pub fn build(self) -> PypiClient {
+        let client_raw = {
+            let client_core = ClientBuilder::new()
+                .user_agent("puffin")
+                .pool_max_idle_per_host(20)
+                .timeout(std::time::Duration::from_secs(60 * 5));
+
+            client_core.build().expect("Fail to build HTTP client.")
+        };
+
+        let retry_policy = ExponentialBackoff::builder().build_with_max_retries(self.retries);
+        let retry_strategy = RetryTransientMiddleware::new_with_policy(retry_policy);
+
+        let mut client_builder =
+            reqwest_middleware::ClientBuilder::new(client_raw).with(retry_strategy);
+
+        if let Some(path) = self.cache {
+            client_builder = client_builder.with(Cache(HttpCache {
+                mode: CacheMode::Default,
+                manager: CACacheManager { path },
+                options: HttpCacheOptions::default(),
+            }));
+        }
+
+        PypiClient {
+            registry: Arc::new(self.registry),
+            proxy: Arc::new(self.proxy),
+            client: client_builder.build(),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct PypiClient {
+    pub(crate) registry: Arc<Url>,
+    pub(crate) proxy: Arc<Url>,
+    pub(crate) client: ClientWithMiddleware,
+}
diff --git a/crates/puffin-client/src/error.rs b/crates/puffin-client/src/error.rs
index 698441165..d7a86198f 100644
--- a/crates/puffin-client/src/error.rs
+++ b/crates/puffin-client/src/error.rs
@@ -1,3 +1,4 @@
+use puffin_requirements::metadata;
 use thiserror::Error;
 use url::Url;
 
@@ -14,6 +15,14 @@ pub enum PypiClientError {
     #[error("Package `{1}` was not found in registry {0}.")]
     PackageNotFound(Url, String),
 
+    /// The metadata file could not be parsed.
+    #[error(transparent)]
+    MetadataParseError(#[from] metadata::Error),
+
+    /// The metadata file was not found in the registry.
+    #[error("File `{1}` was not found in registry {0}.")]
+    FileNotFound(Url, String),
+
     /// A generic request error happened while making a request. Refer to the
     /// error message for more details.
     #[error(transparent)]
@@ -24,7 +33,7 @@ pub enum PypiClientError {
     #[error(transparent)]
     RequestMiddlewareError(#[from] reqwest_middleware::Error),
 
-    #[error("Received some unexpected JSON. Unable to parse.")]
+    #[error("Received some unexpected JSON: {source}")]
     BadJson {
         source: serde_json::Error,
         url: String,
diff --git a/crates/puffin-client/src/lib.rs b/crates/puffin-client/src/lib.rs
index d6c17252e..5d783c71d 100644
--- a/crates/puffin-client/src/lib.rs
+++ b/crates/puffin-client/src/lib.rs
@@ -1,87 +1,6 @@
-use std::path::{Path, PathBuf};
-use std::sync::Arc;
-
-use http_cache_reqwest::{CACacheManager, Cache, CacheMode, HttpCache, HttpCacheOptions};
-use reqwest::ClientBuilder;
-use reqwest_middleware::ClientWithMiddleware;
-use reqwest_retry::policies::ExponentialBackoff;
-use reqwest_retry::RetryTransientMiddleware;
-use url::Url;
+pub use api::SimpleJson;
+pub use client::PypiClientBuilder;
 
 mod api;
+mod client;
 mod error;
-
-pub use api::SimpleJson;
-
-#[derive(Debug, Clone)]
-pub struct PypiClientBuilder {
-    registry: Url,
-    retries: u32,
-    cache: Option<PathBuf>,
-}
-
-impl Default for PypiClientBuilder {
-    fn default() -> Self {
-        Self {
-            registry: Url::parse("https://pypi.org").unwrap(),
-            cache: None,
-            retries: 0,
-        }
-    }
-}
-
-impl PypiClientBuilder {
-    #[must_use]
-    pub fn registry(mut self, registry: Url) -> Self {
-        self.registry = registry;
-        self
-    }
-
-    #[must_use]
-    pub fn retries(mut self, retries: u32) -> Self {
-        self.retries = retries;
-        self
-    }
-
-    #[must_use]
-    pub fn cache(mut self, cache: impl AsRef<Path>) -> Self {
-        self.cache = Some(PathBuf::from(cache.as_ref()));
-        self
-    }
-
-    pub fn build(self) -> PypiClient {
-        let client_raw = {
-            let client_core = ClientBuilder::new()
-                .user_agent("puffin")
-                .pool_max_idle_per_host(20)
-                .timeout(std::time::Duration::from_secs(60 * 5));
-
-            client_core.build().expect("Fail to build HTTP client.")
-        };
-
-        let retry_policy = ExponentialBackoff::builder().build_with_max_retries(self.retries);
-        let retry_strategy = RetryTransientMiddleware::new_with_policy(retry_policy);
-
-        let mut client_builder =
-            reqwest_middleware::ClientBuilder::new(client_raw).with(retry_strategy);
-
-        if let Some(path) = self.cache {
-            client_builder = client_builder.with(Cache(HttpCache {
-                mode: CacheMode::Default,
-                manager: CACacheManager { path },
-                options: HttpCacheOptions::default(),
-            }));
-        }
-
-        PypiClient {
-            registry: Arc::new(self.registry),
-            client: client_builder.build(),
-        }
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct PypiClient {
-    pub(crate) registry: Arc<Url>,
-    pub(crate) client: ClientWithMiddleware,
-}
diff --git a/crates/puffin-requirements/Cargo.toml b/crates/puffin-requirements/Cargo.toml
index 37b76b1b2..98d628281 100644
--- a/crates/puffin-requirements/Cargo.toml
+++ b/crates/puffin-requirements/Cargo.toml
@@ -6,15 +6,19 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-anyhow = "1.0.75"
+anyhow = { version = "1.0.75" }
 clap = { version = "4.4.6", features = ["derive"] }
 colored = { version = "2.0.4" }
-insta = "1.33.0"
+insta = { version = "1.33.0" }
+mailparse = { version = "0.14.0" }
 memchr = { version = "2.6.4" }
-once_cell = "1.18.0"
-pep440_rs = "0.3.12"
-pep508_rs = { version = "0.2.3" }
-regex = "1.9.6"
+once_cell = { version = "1.18.0" }
+pep440_rs = { version = "0.3.12", features = ["serde"] }
+pep508_rs = { version = "0.2.3", features = ["serde"] }
+regex = { version = "1.9.6" }
+rfc2047-decoder = { version = "1.0.1" }
+serde = { version = "1.0.188" }
+thiserror = { version = "1.0.49" }
 
 [dev-dependencies]
 criterion = "0.5.1"
diff --git a/crates/puffin-requirements/src/lib.rs b/crates/puffin-requirements/src/lib.rs
index 6235d74f5..16fbcd671 100644
--- a/crates/puffin-requirements/src/lib.rs
+++ b/crates/puffin-requirements/src/lib.rs
@@ -1,12 +1,14 @@
-pub mod wheel;
 use std::borrow::Cow;
-
 use std::ops::Deref;
 use std::str::FromStr;
 
 use anyhow::Result;
 use memchr::{memchr2, memchr_iter};
-pub use pep508_rs::{Pep508Error, Requirement};
+use pep508_rs::{Pep508Error, Requirement};
+
+pub mod metadata;
+pub mod package_name;
+pub mod wheel;
 
 #[derive(Debug)]
 pub struct Requirements(Vec<Requirement>);
@@ -196,10 +198,10 @@ fn find_newline(text: &str) -> Option<(usize, usize)> {
 mod tests {
     use std::str::FromStr;
 
+    use anyhow::Result;
     use insta::assert_debug_snapshot;
 
     use crate::Requirements;
-    use anyhow::Result;
 
     #[test]
     fn simple() -> Result<()> {
diff --git a/crates/puffin-requirements/src/metadata.rs b/crates/puffin-requirements/src/metadata.rs
new file mode 100644
index 000000000..e7f8a8804
--- /dev/null
+++ b/crates/puffin-requirements/src/metadata.rs
@@ -0,0 +1,194 @@
+//! Derived from `pypi_types_crate`.
+
+use std::collections::HashMap;
+use std::io;
+use std::str::FromStr;
+
+use mailparse::{MailHeaderMap, MailParseError};
+use pep440_rs::{Pep440Error, Version, VersionSpecifiers};
+use pep508_rs::{Pep508Error, Requirement};
+use serde::{Deserialize, Serialize};
+use thiserror::Error;
+
+/// Python Package Metadata 2.1 as specified in
+/// <https://packaging.python.org/specifications/core-metadata/>
+///
+/// One addition is the requirements fixup which insert missing commas e.g. in
+/// `elasticsearch-dsl (>=7.2.0<8.0.0)`
+#[derive(Serialize, Deserialize, Debug, Clone, Eq, PartialEq)]
+#[serde(rename_all = "kebab-case")]
+pub struct Metadata21 {
+    // Mandatory fields
+    pub metadata_version: String,
+    pub name: String,
+    pub version: Version,
+    // Optional fields
+    pub platforms: Vec<String>,
+    pub supported_platforms: Vec<String>,
+    pub summary: Option<String>,
+    pub description: Option<String>,
+    pub description_content_type: Option<String>,
+    pub keywords: Option<String>,
+    pub home_page: Option<String>,
+    pub download_url: Option<String>,
+    pub author: Option<String>,
+    pub author_email: Option<String>,
+    pub maintainer: Option<String>,
+    pub maintainer_email: Option<String>,
+    pub license: Option<String>,
+    pub classifiers: Vec<String>,
+    pub requires_dist: Vec<Requirement>,
+    pub provides_dist: Vec<String>,
+    pub obsoletes_dist: Vec<String>,
+    pub requires_python: Option<VersionSpecifiers>,
+    pub requires_external: Vec<String>,
+    pub project_urls: HashMap<String, String>,
+    pub provides_extras: Vec<String>,
+}
+
+/// <https://github.com/PyO3/python-pkginfo-rs/blob/d719988323a0cfea86d4737116d7917f30e819e2/src/error.rs>
+///
+/// The error type
+#[derive(Error, Debug)]
+pub enum Error {
+    /// I/O error
+    #[error(transparent)]
+    Io(#[from] io::Error),
+    /// mail parse error
+    #[error(transparent)]
+    MailParse(#[from] MailParseError),
+    /// Metadata field not found
+    #[error("metadata field {0} not found")]
+    FieldNotFound(&'static str),
+    /// Unknown distribution type
+    #[error("unknown distribution type")]
+    UnknownDistributionType,
+    /// Metadata file not found
+    #[error("metadata file not found")]
+    MetadataNotFound,
+    /// Invalid project URL (no comma)
+    #[error("Invalid Project-URL field (missing comma): '{0}'")]
+    InvalidProjectUrl(String),
+    /// Multiple metadata files found
+    #[error("found multiple metadata files: {0:?}")]
+    MultipleMetadataFiles(Vec<String>),
+    /// Invalid Version
+    #[error("invalid version: {0}")]
+    Pep440VersionError(String),
+    /// Invalid VersionSpecifier
+    #[error(transparent)]
+    Pep440Error(#[from] Pep440Error),
+    /// Invalid Requirement
+    #[error(transparent)]
+    Pep508Error(#[from] Pep508Error),
+}
+
+/// From <https://github.com/PyO3/python-pkginfo-rs/blob/d719988323a0cfea86d4737116d7917f30e819e2/src/metadata.rs#LL78C2-L91C26>
+impl Metadata21 {
+    /// Parse distribution metadata from metadata bytes
+    pub fn parse(content: &[u8]) -> Result<Self, Error> {
+        // HACK: trick mailparse to parse as UTF-8 instead of ASCII
+        let mut mail = b"Content-Type: text/plain; charset=utf-8\n".to_vec();
+        mail.extend_from_slice(content);
+
+        let msg = mailparse::parse_mail(&mail)?;
+        let headers = msg.get_headers();
+        let get_first_value = |name| {
+            headers.get_first_header(name).and_then(|header| {
+                match rfc2047_decoder::decode(header.get_value_raw()) {
+                    Ok(value) => {
+                        if value == "UNKNOWN" {
+                            None
+                        } else {
+                            Some(value)
+                        }
+                    }
+                    Err(_) => None,
+                }
+            })
+        };
+        let get_all_values = |name| {
+            let values: Vec<String> = headers
+                .get_all_values(name)
+                .into_iter()
+                .filter(|value| value != "UNKNOWN")
+                .collect();
+            values
+        };
+        let metadata_version = headers
+            .get_first_value("Metadata-Version")
+            .ok_or(Error::FieldNotFound("Metadata-Version"))?;
+        let name = headers
+            .get_first_value("Name")
+            .ok_or(Error::FieldNotFound("Name"))?;
+        let version = Version::from_str(
+            &headers
+                .get_first_value("Version")
+                .ok_or(Error::FieldNotFound("Version"))?,
+        )
+        .map_err(Error::Pep440VersionError)?;
+        let platforms = get_all_values("Platform");
+        let supported_platforms = get_all_values("Supported-Platform");
+        let summary = get_first_value("Summary");
+        let body = msg.get_body()?;
+        let description = if body.trim().is_empty() {
+            get_first_value("Description")
+        } else {
+            Some(body)
+        };
+        let keywords = get_first_value("Keywords");
+        let home_page = get_first_value("Home-Page");
+        let download_url = get_first_value("Download-URL");
+        let author = get_first_value("Author");
+        let author_email = get_first_value("Author-email");
+        let license = get_first_value("License");
+        let classifiers = get_all_values("Classifier");
+        let requires_dist = get_all_values("Requires-Dist")
+            .iter()
+            .map(|requires_dist| Requirement::from_str(requires_dist))
+            .collect::<Result<Vec<_>, _>>()?;
+        let provides_dist = get_all_values("Provides-Dist");
+        let obsoletes_dist = get_all_values("Obsoletes-Dist");
+        let maintainer = get_first_value("Maintainer");
+        let maintainer_email = get_first_value("Maintainer-email");
+        let requires_python = get_first_value("Requires-Python")
+            .map(|requires_python| VersionSpecifiers::from_str(&requires_python))
+            .transpose()?;
+        let requires_external = get_all_values("Requires-External");
+        let project_urls = get_all_values("Project-URL")
+            .iter()
+            .map(|name_value| match name_value.split_once(',') {
+                None => Err(Error::InvalidProjectUrl(name_value.clone())),
+                Some((name, value)) => Ok((name.to_string(), value.trim().to_string())),
+            })
+            .collect::<Result<_, _>>()?;
+        let provides_extras = get_all_values("Provides-Extra");
+        let description_content_type = get_first_value("Description-Content-Type");
+        Ok(Metadata21 {
+            metadata_version,
+            name,
+            version,
+            platforms,
+            supported_platforms,
+            summary,
+            description,
+            description_content_type,
+            keywords,
+            home_page,
+            download_url,
+            author,
+            author_email,
+            maintainer,
+            maintainer_email,
+            license,
+            classifiers,
+            requires_dist,
+            provides_dist,
+            obsoletes_dist,
+            requires_python,
+            requires_external,
+            project_urls,
+            provides_extras,
+        })
+    }
+}
diff --git a/crates/puffin-requirements/src/package_name.rs b/crates/puffin-requirements/src/package_name.rs
new file mode 100644
index 000000000..91687177b
--- /dev/null
+++ b/crates/puffin-requirements/src/package_name.rs
@@ -0,0 +1,35 @@
+use std::fmt;
+use std::fmt::{Display, Formatter};
+use std::ops::Deref;
+
+use once_cell::sync::Lazy;
+use regex::Regex;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct PackageName(String);
+
+impl Display for PackageName {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+static NAME_NORMALIZE: Lazy<Regex> = Lazy::new(|| Regex::new(r"[-_.]").unwrap());
+
+impl PackageName {
+    /// See: <https://packaging.python.org/en/latest/specifications/name-normalization/>
+    pub fn normalize(name: impl AsRef<str>) -> Self {
+        // TODO(charlie): Avoid allocating in the common case (when no normalization is required).
+        let mut normalized = NAME_NORMALIZE.replace_all(name.as_ref(), "-").to_string();
+        normalized.make_ascii_lowercase();
+        Self(normalized)
+    }
+}
+
+impl Deref for PackageName {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
diff --git a/crates/puffin-requirements/src/wheel.rs b/crates/puffin-requirements/src/wheel.rs
index db3d5cacb..abeffafee 100644
--- a/crates/puffin-requirements/src/wheel.rs
+++ b/crates/puffin-requirements/src/wheel.rs
@@ -46,19 +46,19 @@ impl FromStr for WheelName {
             build_name = captures.get(2).unwrap().as_str().into();
         } else {
             build_number = None;
-            build_name = "".to_owned();
+            build_name = String::new();
         }
 
         let [distribution, version, py_tags, abi_tags, arch_tags] = pieces.as_slice() else {
             bail!("can't parse binary name {s:?}");
         };
 
-        let distribution = distribution.to_string();
+        let distribution = (*distribution).to_string();
         let version = Version::from_str(version)
             .map_err(|e| anyhow!("failed to parse version {:?} from {:?}: {}", version, s, e))?;
-        let py_tags = py_tags.split('.').map(|tag| tag.into()).collect();
-        let abi_tags = abi_tags.split('.').map(|tag| tag.into()).collect();
-        let arch_tags = arch_tags.split('.').map(|tag| tag.into()).collect();
+        let py_tags = py_tags.split('.').map(std::convert::Into::into).collect();
+        let abi_tags = abi_tags.split('.').map(std::convert::Into::into).collect();
+        let arch_tags = arch_tags.split('.').map(std::convert::Into::into).collect();
 
         Ok(Self {
             distribution,