when the

10 files changed, 684 insertions, 174 deletions

diff --git a/.idea/jsonSchemas.xml b/.idea/jsonSchemas.xml
new file mode 100644
index 0000000..7d1fb3b
--- /dev/null
+++ b/.idea/jsonSchemas.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="JsonSchemaMappingsProjectConfiguration">
+    <state>
+      <map>
+        <entry key="No JSON schema">
+          <value>
+            <SchemaInfo>
+              <option name="ignoredFile" value="true" />
+              <option name="name" value="No JSON schema" />
+              <option name="relativePathToSchema" value="" />
+              <option name="applicationDefined" value="true" />
+              <option name="patterns">
+                <list>
+                  <Item>
+                    <option name="path" value="file://$PROJECT_DIR$/test_stuff/versions/1.2.1.json" />
+                  </Item>
+                </list>
+              </option>
+              <option name="isIgnoredFile" value="true" />
+            </SchemaInfo>
+          </value>
+        </entry>
+      </map>
+    </state>
+  </component>
+</project>
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
index 367ebcf..a750f3f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -209,6 +209,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "fuchsia-cprng"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
+
+[[package]]
 name = "futures-channel"
 version = "0.3.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -248,6 +254,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "gcc"
+version = "0.3.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f5f3913fa0bfe7ee1fd8248b6b9f42a5af4b9d65ec2dd2c3c26132b950ecfc2"
+
+[[package]]
 name = "getrandom"
 version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -255,7 +267,7 @@ checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
 dependencies = [
  "cfg-if",
  "libc",
- "wasi",
+ "wasi 0.11.0+wasi-snapshot-preview1",
 ]
 
 [[package]]
@@ -290,6 +302,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
 
 [[package]]
+name = "hex"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
+dependencies = [
+ "serde",
+]
+
+[[package]]
 name = "http"
 version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -647,7 +668,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2886843bf800fba2e3377cff24abf6379b4c4d5c6681eaf9ea5b0d15090450bd"
 dependencies = [
  "libc",
- "wasi",
+ "wasi 0.11.0+wasi-snapshot-preview1",
  "windows-sys 0.52.0",
 ]
 
@@ -682,9 +703,11 @@ name = "o3launcher"
 version = "0.1.0"
 dependencies = [
  "chrono",
+ "hex",
  "log",
  "regex",
  "reqwest",
+ "rust-crypto",
  "serde",
  "serde_json",
  "tokio",
@@ -792,6 +815,53 @@ dependencies = [
 ]
 
 [[package]]
+name = "rand"
+version = "0.3.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64ac302d8f83c0c1974bf758f6b041c6c8ada916fbb44a609158ca8b064cc76c"
+dependencies = [
+ "libc",
+ "rand 0.4.6",
+]
+
+[[package]]
+name = "rand"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "552840b97013b1a26992c11eac34bdd778e464601a4c2054b5f0bff7c6761293"
+dependencies = [
+ "fuchsia-cprng",
+ "libc",
+ "rand_core 0.3.1",
+ "rdrand",
+ "winapi",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a6fdeb83b075e8266dcc8762c22776f6877a63111121f5f8c7411e5be7eed4b"
+dependencies = [
+ "rand_core 0.4.2",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c33a3c44ca05fa6f1807d8e6743f3824e8509beca625669633be0acbdf509dc"
+
+[[package]]
+name = "rdrand"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "678054eb77286b51581ba43620cc911abf02758c91f93f479767aed0f90458b2"
+dependencies = [
+ "rand_core 0.3.1",
+]
+
+[[package]]
 name = "regex"
 version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -879,12 +949,31 @@ dependencies = [
 ]
 
 [[package]]
+name = "rust-crypto"
+version = "0.2.36"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f76d05d3993fd5f4af9434e8e436db163a12a9d40e1a58a726f27a01dfd12a2a"
+dependencies = [
+ "gcc",
+ "libc",
+ "rand 0.3.23",
+ "rustc-serialize",
+ "time",
+]
+
+[[package]]
 name = "rustc-demangle"
 version = "0.1.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "719b953e2095829ee67db738b3bfa9fa368c94900df327b3f07fe6e794d2fe1f"
 
 [[package]]
+name = "rustc-serialize"
+version = "0.3.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe834bc780604f4674073badbad26d7219cadfb4a2275802db12cbae17498401"
+
+[[package]]
 name = "rustix"
 version = "0.38.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1133,6 +1222,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "time"
+version = "0.1.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b797afad3f312d1c66a56d11d0316f916356d11bd158fbc6ca6389ff6bf805a"
+dependencies = [
+ "libc",
+ "wasi 0.10.0+wasi-snapshot-preview1",
+ "winapi",
+]
+
+[[package]]
 name = "tinystr"
 version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1273,6 +1373,12 @@ dependencies = [
 
 [[package]]
 name = "wasi"
+version = "0.10.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a143597ca7c7793eff794def352d41792a93c481eb1042423ff7ff72ba2c31f"
+
+[[package]]
+name = "wasi"
 version = "0.11.0+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
@@ -1355,6 +1461,28 @@ dependencies = [
 ]
 
 [[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
+[[package]]
 name = "windows-core"
 version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 7770ba5..991c1ff 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,9 +5,11 @@ edition = "2021"
 
 [dependencies]
 chrono = { version = "0.4.39", default-features = false, features = ["std", "alloc", "clock", "now", "serde"] }
+hex = { version = "0.4.3", features = ["serde"] }
 log = "0.4.22"
 regex = "1.11.1"
 reqwest = "0.12.9"
+rust-crypto = "0.2.36"
 serde = { version = "1.0.216", features = ["derive"] }
 serde_json = "1.0.133"
 tokio = { version = "1.42.0", features = ["fs"] }
diff --git a/src/launcher.rs b/src/launcher.rs
index 82abef0..d99a294 100644
--- a/src/launcher.rs
+++ b/src/launcher.rs
@@ -1,151 +1,15 @@
-use std::{collections::{BTreeMap, HashMap}, error::Error, fmt::Write, io::ErrorKind};

-use std::path::{Path, PathBuf};

-use chrono::{DateTime, Utc};

-use serde::{Serialize, Deserialize};

-

-use log::{debug, warn};

-

-use super::version::{*, manifest::*};

-

 mod constants;

-use constants::*;

-

-#[derive(Serialize, Deserialize, Debug)]

-struct RemoteVersionIndexEntry {

-	last_update: DateTime<Utc>

-}

-

-#[derive(Serialize, Deserialize, Debug)]

-struct RemoteVersionIndex {

-	versions: BTreeMap<String, RemoteVersionIndexEntry>

-}

-

-impl Default for RemoteVersionIndex {

-	fn default() -> Self {

-		RemoteVersionIndex {

-			versions: BTreeMap::new()

-		}

-	}

-}

-

-struct RemoteVersionList {

-	versions: HashMap<String, VersionManifestVersion>,

-	index: RemoteVersionIndex

-}

-

-impl RemoteVersionList {

-	async fn new(home: impl AsRef<Path>) -> Result<RemoteVersionList, Box<dyn Error>> {

-		let text = reqwest::get(URL_VERSION_MANIFEST).await?.error_for_status()?.text().await?;

-		let manifest: VersionManifest = serde_json::from_str(text.as_str())?;

-

-		let mut fname = home.as_ref().to_path_buf();

-		fname.push(".version.json");

-

-		let index: RemoteVersionIndex = match tokio::fs::read_to_string(fname).await {

-			Ok(s) => serde_json::from_str(s.as_str())?,

-			Err(e) => {

-				if e.kind() == ErrorKind::NotFound {

-					RemoteVersionIndex::default()

-				} else {

-					return Err(Box::new(e));

-				}

-			}

-		};

-

-		let mut versions = HashMap::new();

-		for v in manifest.versions {

-			versions.insert(v.id.clone(), v);

-		}

-

-		Ok(RemoteVersionList {

-			versions,

-			index

-		})

-	}

-}

+mod version;

 

-struct LocalVersionList {

-	versions: BTreeMap<String, CompleteVersion>

-}

-

-impl LocalVersionList {

-	async fn load_version(path: &PathBuf) -> Result<CompleteVersion, Box<dyn Error>> {

-		serde_json::from_str(tokio::fs::read_to_string(path).await?)?;

-	}

-

-	async fn load_versions(home: impl AsRef<Path>, skip: impl Fn(&str) -> bool) -> Result<LocalVersionList, Box<dyn Error>> {

-		let mut rd = tokio::fs::read_dir(home).await?;

-		let versions = BTreeMap::new();

-

-		while let Some(ent) = rd.next_entry().await? {

-			if !ent.file_type().await?.is_dir() { continue; }

-

-			// when the code is fugly

-			let path = match ent.file_name().to_str() {

-				Some(s) => {

-					if skip(s) {

-						debug!("Skipping local version {s} because (I assume) it is remotely tracked.");

-						continue

-					}

-

-					/* FIXME: once https://github.com/rust-lang/rust/issues/127292 is closed,

-					 *  use add_extension to avoid extra heap allocations (they hurt my feelings) */

-					let mut path = ent.path();

-

-					// can't use set_extension since s might contain a . (like 1.8.9)

-					path.push(format!("{s}.json"));

-

-

-				},

+use std::error::Error;

+pub use version::VersionList;

 

-				/* We just ignore directories with names that contain invalid unicode. Unfortunately, the laucher

-				 * will not be supporting such custom versions. Name your version something sensible please. */

-				None => {

-					warn!("Ignoring a local version because its id contains invalid unicode.");

-					continue

-				}

-			};

-

-			match Self::load_version(path).await {

-				Ok(v) => {

-					versions.insert(v.id.clone(), v);

-				},

-				Err(e) => {

-					// FIXME: just display the filename without to_string_lossy when https://github.com/rust-lang/rust/issues/120048 is closed

-					warn!("Ignoring local version {}: {e}", ent.file_name().to_string_lossy());

-				}

-			}

-		}

-

-		Ok(LocalVersionList { versions })

-	}

-}

-

-struct VersionList {

-	offline: bool,

-	remote: Option<RemoteVersionList>,

-	local: LocalVersionList

+pub struct Launcher {

+    pub versions: VersionList

 }

 

-impl VersionList {

-	pub async fn online(home: impl AsRef<Path>) -> Result<VersionList, Box<dyn Error>> {

-		let remote = RemoteVersionList::new(home).await?;

-		let local = LocalVersionList::load_versions(home, |s| remote.versions.contains_key(s)).await?;

-

-		Ok(VersionList {

-			offline: false,

-			remote: Some(remote),

-			local

-		})

-	}

-

-	pub async fn offline(home: impl AsRef<Path>) -> Result<VersionList, Box<dyn Error>> {

-		let local = LocalVersionList::load_versions(home, |_| false).await?;

-

-		Ok(VersionList {

-			offline: true,

-			remote: None,

-			local

-		})

-	}

-}

+impl Launcher {

+    pub async fn new() -> Result<Launcher, Box<dyn Error>> {

+        todo!()

+    }

+}
\ No newline at end of file
diff --git a/src/launcher/version.rs b/src/launcher/version.rs
new file mode 100644
index 0000000..378e008
--- /dev/null
+++ b/src/launcher/version.rs
@@ -0,0 +1,293 @@
+use std::{collections::{BTreeMap, HashMap}, error::Error, io::ErrorKind};
+use std::borrow::Cow;
+use std::collections::HashSet;
+use std::fmt::Display;
+use std::path::{Path, PathBuf};
+use chrono::{DateTime, Utc};
+use crypto::digest::Digest;
+use crypto::sha1::Sha1;
+use serde::{Serialize, Deserialize};
+
+use log::{debug, info, warn};
+
+use crate::version::{*, manifest::*};
+
+use super::constants::*;
+
+struct RemoteVersionList {
+    versions: HashMap<String, VersionManifestVersion>,
+    latest: LatestVersions
+}
+
+impl RemoteVersionList {
+    async fn new() -> Result<RemoteVersionList, Box<dyn Error>> {
+        let text = reqwest::get(URL_VERSION_MANIFEST).await?.error_for_status()?.text().await?;
+        let manifest: VersionManifest = serde_json::from_str(text.as_str())?;
+
+        let mut versions = HashMap::new();
+        for v in manifest.versions {
+            versions.insert(v.id.clone(), v);
+        }
+
+        Ok(RemoteVersionList {
+            versions,
+            latest: manifest.latest
+        })
+    }
+
+    async fn download_version(&self, ver: &VersionManifestVersion, path: &Path) -> Result<CompleteVersion, Box<dyn Error>> {
+        // ensure parent directory exists
+        match tokio::fs::create_dir_all(path.parent().expect("version .json has no parent (impossible)")).await {
+            Err(e) => {
+                if e.kind() != ErrorKind::AlreadyExists {
+                    warn!("failed to create {} parent dirs: {e}", path.to_string_lossy());
+                    return Err(e.into());
+                }
+            },
+            Ok(()) => {}
+        }
+
+        // download it
+        let ver_text = reqwest::get(ver.url.as_str()).await?.error_for_status()?.text().await?;
+
+        // make sure it's valid
+        ver.sha1.verify(ver_text.as_str())
+            .map_err::<Box<dyn Error>, _>(|e| format!("downloaded version {} has wrong hash! (expect {}, got {})", ver.id.as_str(), &ver.sha1, e).as_str().into())?;
+
+        // make sure it's well-formed
+        let cver: CompleteVersion = serde_json::from_str(ver.url.as_str())?;
+
+        // write it out
+        tokio::fs::write(path, ver_text).await?;
+
+        Ok(cver)
+    }
+}
+
+struct LocalVersionList {
+    versions: BTreeMap<String, CompleteVersion>
+}
+
+#[derive(Debug)]
+enum LocalVersionError {
+    Sha1Mismatch { exp: Sha1Digest, got: Sha1Digest },
+    VersionMismatch { fname: String, json: String },
+    Unknown(Box<dyn Error>)
+}
+
+impl Display for LocalVersionError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Sha1Mismatch { exp, got } => {
+                write!(f, "sha1 mismatch (exp {exp}, got {got})")
+            },
+            VersionMismatch { fname, json } => {
+                write!(f, "version ID mismatch (filename {fname}, json {json})")
+            },
+            LocalVersionError::Unknown(err) => {
+                write!(f, "unknown version error: {err}")
+            }
+        }
+    }
+}
+
+impl Error for LocalVersionError {}
+
+impl LocalVersionList {
+    async fn load_version(path: &Path, sha1: Option<&Sha1Digest>) -> Result<CompleteVersion, LocalVersionError> {
+        // grumble grumble I don't like reading in the whole file at once
+        let ver = tokio::fs::read_to_string(path).await.map_err(|e| LocalVersionError::Unknown(Box::new(e)))?;
+        if let Some(digest_exp) = sha1 {
+            digest_exp.verify(ver.as_str())
+                .map_err(|got| Sha1Mismatch { exp: digest_exp.to_owned(), got })?;
+        }
+
+        let ver: CompleteVersion = serde_json::from_str(ver.as_str()).map_err(|e| LocalVersionError::Unknown(Box::new(e)))?;
+
+        let fname_id = path.file_stem()
+            .expect("tried to load a local version with no path") // should be impossible
+            .to_str()
+            .expect("tried to load a local version with invalid UTF-8 filename"); // we already checked if the filename is valid UTF-8 at this point
+
+        if fname_id == ver.id.as_str() {
+            Ok(ver)
+        } else {
+            Err(VersionMismatch { fname: fname_id.to_owned(), json: ver.id })
+        }
+    }
+
+    async fn load_versions(home: &Path, skip: impl Fn(&str) -> bool) -> Result<LocalVersionList, Box<dyn Error>> {
+        let mut rd = tokio::fs::read_dir(home).await?;
+        let mut versions = BTreeMap::new();
+
+        while let Some(ent) = rd.next_entry().await? {
+            if !ent.file_type().await?.is_dir() { continue; }
+
+            // when the code is fugly
+            let path = match ent.file_name().to_str() {
+                Some(s) => {
+                    if skip(s) {
+                        debug!("Skipping local version {s} because (I assume) it is remotely tracked.");
+                        continue
+                    }
+
+                    /* FIXME: once https://github.com/rust-lang/rust/issues/127292 is closed,
+                     *  use add_extension to avoid extra heap allocations (they hurt my feelings) */
+                    let mut path = ent.path();
+
+                    // can't use set_extension since s might contain a . (like 1.8.9)
+                    path.push(format!("{s}.json"));
+                    path
+                },
+
+                /* We just ignore directories with names that contain invalid unicode. Unfortunately, the laucher
+                 * will not be supporting such custom versions. Name your version something sensible please. */
+                None => {
+                    warn!("Ignoring a local version {} because its id contains invalid unicode.", ent.file_name().to_string_lossy());
+                    continue
+                }
+            };
+
+            match Self::load_version(&path, None).await {
+                Ok(v) => {
+                    versions.insert(v.id.clone(), v);
+                },
+                Err(e) => {
+                    // FIXME: just display the filename without to_string_lossy when https://github.com/rust-lang/rust/issues/120048 is closed
+                    warn!("Ignoring local version {}: {e}", ent.file_name().to_string_lossy());
+                }
+            }
+        }
+
+        Ok(LocalVersionList { versions })
+    }
+}
+
+pub struct VersionList {
+    remote: Option<RemoteVersionList>,
+    local: LocalVersionList,
+    home: PathBuf
+}
+
+pub enum VersionResult<'a> {
+    Complete(&'a CompleteVersion),
+    Remote(&'a VersionManifestVersion),
+    None
+}
+
+impl<'a> From<&'a CompleteVersion> for VersionResult<'a> {
+    fn from(value: &'a CompleteVersion) -> Self {
+        Self::Complete(value)
+    }
+}
+
+impl<'a> From<&'a VersionManifestVersion> for VersionResult<'a> {
+    fn from(value: &'a VersionManifestVersion) -> Self {
+        Self::Remote(value)
+    }
+}
+
+impl<'a, T: Into<VersionResult<'a>>> From<Option<T>> for VersionResult<'a> {
+    fn from(value: Option<T>) -> Self {
+        value.map_or(VersionResult::None, |v| v.into())
+    }
+}
+
+pub enum VersionResolveError {
+    InheritanceLoop,
+    MissingVersion(String),
+    Unknown(Box<dyn Error>)
+}
+
+use crate::util::{Sha1Digest, SHA1_DIGEST_BYTES};
+use crate::launcher::version::LocalVersionError::{Sha1Mismatch, VersionMismatch};
+use crate::launcher::version::VersionResolveError::MissingVersion;
+
+impl VersionList {
+    pub async fn online(home: &Path) -> Result<VersionList, Box<dyn Error>> {
+        let remote = RemoteVersionList::new().await?;
+        let local = LocalVersionList::load_versions(home.as_ref(), |s| remote.versions.contains_key(s)).await?;
+
+        Ok(VersionList {
+            remote: Some(remote),
+            local,
+            home: home.to_path_buf()
+        })
+    }
+
+    pub async fn offline(home: &Path) -> Result<VersionList, Box<dyn Error>> {
+        let local = LocalVersionList::load_versions(home, |_| false).await?;
+
+        Ok(VersionList {
+            remote: None,
+            local,
+            home: home.to_path_buf()
+        })
+    }
+
+    pub fn is_online(&self) -> bool {
+        self.remote.is_some()
+    }
+
+    pub fn get_version_lazy(&self, id: &str) -> VersionResult {
+        self.remote.as_ref()
+            .map_or_else(|| self.local.versions.get(id).into(), |r| r.versions.get(id).into())
+    }
+
+    pub fn get_remote_version(&self, id: &str) -> Option<&VersionManifestVersion> {
+        let remote = self.remote.as_ref().expect("get_remote_version called in offline mode!");
+
+        remote.versions.get(id)
+    }
+
+    pub async fn load_remote_version(&self, ver: &VersionManifestVersion) -> Result<CompleteVersion, Box<dyn Error>> {
+        let remote = self.remote.as_ref().expect("load_remote_version called in offline mode!");
+
+        let id = ver.id.as_str();
+        let mut ver_path = self.home.join(id);
+        ver_path.push(format!("{id}.json"));
+
+        match LocalVersionList::load_version(ver_path.as_path(), Some(&ver.sha1)).await {
+            Ok(v) => return Ok(v),
+            Err(e) => {
+                info!("redownloading {id}, since the local copy could not be loaded: {e}");
+            }
+        }
+
+        remote.download_version(ver, ver_path.as_path()).await
+    }
+
+    pub async fn resolve_version<'v>(&self, ver: &'v CompleteVersion) -> Result<Cow<'v, CompleteVersion>, VersionResolveError> {
+        let mut seen: HashSet<String> = HashSet::new();
+        seen.insert(ver.id.clone());
+
+        let Some(inherit) = ver.inherits_from.as_ref() else {
+            return Ok(Cow::Borrowed(ver));
+        };
+
+        let mut ver = ver.clone();
+        let mut inherit = inherit.clone();
+
+        loop {
+            let inherited_ver = match self.get_version_lazy(inherit.as_str()) {
+                VersionResult::Complete(v) => Cow::Borrowed(v),
+                VersionResult::Remote(v) =>
+                    Cow::Owned(self.load_remote_version(v).await.map_err(|e| VersionResolveError::Unknown(e))?),
+                VersionResult::None => {
+                    warn!("Cannot resolve version {}, it inherits an unknown version {inherit}", ver.id);
+                    return Err(MissingVersion(inherit));
+                }
+            };
+
+            ver.apply_child(inherited_ver.as_ref());
+            
+            let Some(new_inherit) = inherited_ver.inherits_from.as_ref() else {
+                break
+            };
+            
+            inherit.replace_range(.., new_inherit.as_str());
+        }
+
+        Ok(Cow::Owned(ver))
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 5f506fc..70041eb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,2 +1,3 @@
+mod util;
 mod version;
 mod launcher;
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..2a778e4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,3 @@
 fn main() {
-    println!("Hello, world!");
+
 }
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..428990c
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,68 @@
+use std::fmt::{Debug, Display, Formatter, Pointer};
+use std::ops::Deref;
+use crypto::digest::Digest;
+use crypto::sha1::Sha1;
+use serde::{Deserialize, Deserializer};
+use serde::de::{Error, Visitor};
+use hex::{FromHex, ToHex};
+
+// sha1 digests are 20 bytes long
+pub const SHA1_DIGEST_BYTES: usize = 20;
+pub type Sha1DigestBytes = [u8; SHA1_DIGEST_BYTES];
+
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone)]
+pub struct Sha1Digest(pub Sha1DigestBytes);
+
+impl Debug for Sha1Digest {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Sha1Digest {{{}}}", self.0.encode_hex::<String>())
+    }
+}
+
+impl Display for Sha1Digest {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0.encode_hex::<String>())
+    }
+}
+
+impl Sha1Digest {
+    pub fn verify(&self, s: &str) -> Result<(), Sha1Digest> {
+        let mut st = Sha1::new();
+        let mut dig = [0u8; SHA1_DIGEST_BYTES];
+
+        st.input_str(s);
+        st.result(&mut dig);
+
+        if self.0 == dig {
+            return Ok(());
+        }
+
+        Err(Sha1Digest(dig))
+    }
+}
+
+struct Sha1DigestVisitor;
+
+impl <'a> Visitor<'a> for Sha1DigestVisitor {
+    type Value = Sha1Digest;
+
+    fn expecting(&self, formatter: &mut Formatter) -> std::fmt::Result {
+        write!(formatter, "a valid SHA-1 digest (40-character hex string)")
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Sha1DigestBytes::from_hex(v).map_err(|e| E::custom(e)).map(Sha1Digest)
+    }
+}
+
+impl<'a> Deserialize<'a> for Sha1Digest {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'a>,
+    {
+        deserializer.deserialize_any(Sha1DigestVisitor)
+    }
+}
\ No newline at end of file
diff --git a/src/version.rs b/src/version.rs
index 0c1e65f..190dd72 100644
--- a/src/version.rs
+++ b/src/version.rs
@@ -1,12 +1,15 @@
 use core::fmt;
 use std::{collections::BTreeMap, convert::Infallible, marker::PhantomData, ops::Deref, str::FromStr};
-
+use std::ascii::AsciiExt;
+use std::collections::HashMap;
 use chrono::{DateTime, Utc};
 use regex::Regex;
 use serde::{de::{self, Visitor}, Deserialize, Deserializer};
+use serde::de::SeqAccess;
 
 pub mod manifest;
 use manifest::*;
+use crate::util::Sha1Digest;
 
 #[derive(Deserialize, Debug, Clone, Copy)]
 #[serde(rename_all = "lowercase")]
@@ -29,7 +32,7 @@ pub enum OperatingSystem {
     Unknown  // (not used in official jsons)
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 struct WrappedRegex(Regex);
 
 impl Deref for WrappedRegex {
@@ -63,7 +66,7 @@ impl<'de> Deserialize<'de> for WrappedRegex {
     }
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct OSRestriction {
     pub name: Option<OperatingSystem>,
 
@@ -71,7 +74,7 @@ pub struct OSRestriction {
     pub arch: Option<WrappedRegex>
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct CompatibilityRule {
     pub action: RuleAction,
     pub features: Option<BTreeMap<String, bool>>,
@@ -92,7 +95,7 @@ impl CompatibilityRule {
     }
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct Argument {
     #[serde(default)]
     pub rules: Option<Vec<CompatibilityRule>>,
@@ -102,7 +105,7 @@ pub struct Argument {
     pub value: Vec<String>
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct WrappedArgument(Argument);
 
 impl FromStr for Argument {
@@ -132,13 +135,29 @@ impl<'de> Deserialize<'de> for WrappedArgument {
     }
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct Arguments {
     pub game: Option<Vec<WrappedArgument>>,
     pub jvm: Option<Vec<WrappedArgument>>
 }
 
-#[derive(Deserialize, Debug, PartialEq, Eq, PartialOrd, Ord)]
+impl Arguments {
+    fn apply_child(&mut self, other: &Arguments) {
+        if self.game.is_none() {
+            if let Some(game) = other.game.as_ref() {
+                self.game.replace(game.to_owned());
+            }
+        }
+
+        if self.jvm.is_none() {
+            if let Some(jvm) = other.jvm.as_ref() {
+                self.jvm.replace(jvm.to_owned());
+            }
+        }
+    }
+}
+
+#[derive(Deserialize, Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
 #[serde(rename_all = "snake_case")]
 pub enum DownloadType {
     Client,
@@ -148,9 +167,9 @@ pub enum DownloadType {
     WindowsServer
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct DownloadInfo {
-    pub sha1: Option<String>,
+    pub sha1: Option<Sha1Digest>,
     pub size: Option<usize>,
     pub total_size: Option<usize>, // available for asset index
     pub url: Option<String>, // may not be present for libraries
@@ -158,26 +177,26 @@ pub struct DownloadInfo {
     pub path: Option<String>
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "camelCase")]
 pub struct JavaVersionInfo {
     pub component: String,
     pub major_version: u32
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct LibraryDownloads {
     pub artifact: Option<DownloadInfo>,
     pub classifiers: Option<BTreeMap<String, DownloadInfo>>
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct LibraryExtractRule {
     #[serde(default)]
     pub exclude: Vec<String>
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct Library {
     pub downloads: Option<LibraryDownloads>,
     pub name: String,
@@ -187,7 +206,7 @@ pub struct Library {
     pub url: Option<String> // old format
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct ClientLogging {
     pub argument: String,
 
@@ -196,12 +215,12 @@ pub struct ClientLogging {
     pub file: DownloadInfo
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 pub struct Logging {
     pub client: ClientLogging // other fields unknown
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Clone)]
 #[serde(rename_all = "camelCase")]
 pub struct CompleteVersion {
     pub arguments: Option<Arguments>,
@@ -217,8 +236,8 @@ pub struct CompleteVersion {
     #[serde(default)]
     pub downloads: BTreeMap<DownloadType, DownloadInfo>,
 
-    #[serde(default)]
-    pub libraries: Vec<Library>,
+    #[serde(default, deserialize_with = "deserialize_libraries")]
+    pub libraries: HashMap<String, Library>,
 
     pub id: String,
     pub jar: Option<String>, // used as the jar filename if specified? (no longer used officially)
@@ -243,6 +262,104 @@ pub struct CompleteVersion {
      */
 }
 
+impl CompleteVersion {
+    pub fn get_jar(&self) -> &String {
+        &self.jar.as_ref().unwrap_or(&self.id)
+    }
+
+    pub fn apply_child(&mut self, other: &CompleteVersion) {
+        macro_rules! replace_missing {
+            ($name:ident) => {
+                if self.$name.is_none() {
+                    if let Some($name) = other.$name.as_ref() {
+                        self.$name.replace($name.to_owned());
+                    }
+                }
+            };
+        }
+
+        if let Some(arguments) = other.arguments.as_ref() {
+            if let Some(my_args) = self.arguments.as_mut() {
+                my_args.apply_child(arguments);
+            } else {
+                self.arguments.replace(arguments.to_owned());
+            }
+        }
+
+        replace_missing!(minecraft_arguments);
+        replace_missing!(asset_index);
+        replace_missing!(assets);
+        replace_missing!(compliance_level);
+        replace_missing!(java_version);
+
+        for (dltype, dl) in other.downloads.iter().by_ref() {
+            self.downloads.entry(*dltype).or_insert_with(|| dl.clone());
+        }
+
+        for (name, lib) in other.libraries.iter().by_ref() {
+            self.libraries.entry(name.to_owned()).or_insert_with(|| lib.clone());
+        }
+
+        replace_missing!(logging);
+        replace_missing!(main_class);
+        replace_missing!(minimum_launcher_version);
+        replace_missing!(release_time);
+        replace_missing!(time);
+        replace_missing!(version_type);
+
+        if let Some(rules) = other.compatibility_rules.as_ref() {
+            if let Some(my_rules) = self.compatibility_rules.as_mut() {
+                for rule in rules {
+                    my_rules.push(rule.to_owned());
+                }
+            } else {
+                self.compatibility_rules.replace(rules.to_owned());
+            }
+        }
+
+        replace_missing!(incompatibility_reason);
+    }
+}
+
+fn canonicalize_library_name(name: &str) -> String {
+    name.split(':')
+        .enumerate()
+        .filter(|(i, _)| *i != 2)
+        .map(|(_, s)| s.to_ascii_lowercase())
+        .collect::<Vec<_>>()
+        .join(":")
+}
+
+fn deserialize_libraries<'de, D>(deserializer: D) -> Result<HashMap<String, Library>, D::Error>
+where
+    D: Deserializer<'de>
+{
+    struct LibrariesVisitor;
+
+    impl<'de> Visitor<'de> for LibrariesVisitor {
+        type Value = HashMap<String, Library>;
+
+        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            formatter.write_str("an array of libraries")
+        }
+
+        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+        where
+            A: SeqAccess<'de>,
+        {
+            let mut map = HashMap::new();
+
+            while let Some(lib) = seq.next_element::<Library>()? {
+                map.insert(canonicalize_library_name(lib.name.as_str()), lib);
+            }
+
+            Ok(map)
+        }
+    }
+
+    deserializer.deserialize_seq(LibrariesVisitor)
+}
+
 // https://serde.rs/string-or-struct.html
 fn string_or_struct<'de, T, D>(deserializer: D) -> Result<T, D::Error>
 where
@@ -257,19 +374,19 @@ where
     {
         type Value = T;
 
-        fn expecting(&self, formatter: &mut std::fmt::Formatter) -> fmt::Result {
+        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
             formatter.write_str("string or map")
         }
 
         fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
             where
-                E: serde::de::Error, {
+                E: de::Error, {
             Ok(FromStr::from_str(v).unwrap())
         }
 
         fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
             where
-                A: serde::de::MapAccess<'de>, {
+                A: de::MapAccess<'de>, {
             // wizardry (check comment in link)
             Deserialize::deserialize(de::value::MapAccessDeserializer::new(map))
         }
@@ -304,7 +421,7 @@ where
 
         fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
             where
-                A: de::SeqAccess<'de>, {
+                A: SeqAccess<'de>, {
             Deserialize::deserialize(de::value::SeqAccessDeserializer::new(seq))
         }
     }
@@ -333,4 +450,13 @@ mod tests {
         let arg: VersionManifest = serde_json::from_str(s.unwrap().as_str()).unwrap();
         dbg!(arg);
     }
+
+    #[test]
+    fn test_it3() {
+        assert_eq!(canonicalize_library_name("group:artifact:version"), String::from("group:artifact"));
+        assert_eq!(canonicalize_library_name("group:artifact:version:specifier"), String::from("group:artifact:specifier"));
+        assert_eq!(canonicalize_library_name("not_enough:fields"), String::from("not_enough:fields"));
+        assert_eq!(canonicalize_library_name("word"), String::from("word"));
+        assert_eq!(canonicalize_library_name(""), String::from(""));
+    }
 }
diff --git a/src/version/manifest.rs b/src/version/manifest.rs
index 1fa8041..437daf6 100644
--- a/src/version/manifest.rs
+++ b/src/version/manifest.rs
@@ -2,6 +2,7 @@ use core::fmt;
 
 use chrono::{DateTime, Utc};
 use serde::{de::Visitor, Deserialize};
+use crate::util::Sha1Digest;
 
 #[derive(Deserialize, Debug)]
 pub struct LatestVersions {
@@ -9,7 +10,7 @@ pub struct LatestVersions {
     pub snapshot: String
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum VersionType {
     Snapshot,
     Release,
@@ -58,7 +59,7 @@ pub struct VersionManifestVersion {
     pub url: String,
     pub time: DateTime<Utc>,
     pub release_time: DateTime<Utc>,
-    pub sha1: String,
+    pub sha1: Sha1Digest,
     pub compliance_level: u32
 }