From 8bd4b9b6a1362f53d48be1ee58bf751b1ac34e55 Mon Sep 17 00:00:00 2001
From: Jiahao XU <Jiahao_XU@outlook.com>
Date: Mon, 6 Jun 2022 22:32:15 +1000
Subject: [PATCH] Impl `detect_targets` for linux

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
---
 src/lib.rs    |  2 +-
 src/target.rs | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index ef3cfbaf..0a6c1437 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,7 +16,7 @@ pub mod bins;
 pub mod fetchers;
 
 mod target;
-pub use target::TARGET;
+pub use target::{detect_targets, TARGET};
 
 /// Default package path template (may be overridden in package Cargo.toml)
 pub const DEFAULT_PKG_URL: &str =
diff --git a/src/target.rs b/src/target.rs
index 94bfe775..4c6f8f57 100644
--- a/src/target.rs
+++ b/src/target.rs
@@ -1,2 +1,97 @@
 /// Compiled target triple, used as default for binary fetching
 pub const TARGET: &str = env!("TARGET");
+
+/// Detect the targets supported at runtime,
+/// which might be different from `TARGET` which is detected
+/// at compile-time.
+///
+/// Return targets supported in the order of preference.
+/// If target_os is linux and it support gnu, then it is preferred
+/// to musl.
+///
+/// If target_os is mac and it is aarch64, then aarch64 is preferred
+/// to x86_64.
+///
+/// Check [this issue](https://github.com/ryankurte/cargo-binstall/issues/155)
+/// for more information.
+pub async fn detect_targets() -> Vec<Box<str>> {
+    #[cfg(target_os = "linux")]
+    {
+        return linux::detect_targets_linux().await;
+    }
+
+    todo!()
+}
+
+#[cfg(target_os = "linux")]
+mod linux {
+    use super::TARGET;
+    use std::process::Output;
+    use tokio::process::Command;
+
+    async fn detect_targets_linux() -> Vec<Box<str>> {
+        let abi = parse_abi();
+
+        if let Ok(Output {
+            status: _,
+            stdout,
+            stderr,
+        }) = Command::new("ldd").arg("--version").output().await
+        {
+            let libc_version = if let Some(libc_version) = parse_libc_version(stdout) {
+                libc_version
+            } else if let Some(libc_version) = parse_libc_version(stderr) {
+                libc_version
+            } else {
+                return vec![create_target_str("musl", abi)];
+            };
+
+            if libc_version == "gnu" {
+                return vec![
+                    create_target_str("gnu", abi),
+                    create_target_str("musl", abi),
+                ];
+            }
+        }
+
+        // Fallback to using musl
+        vec![create_target_str("musl", abi)]
+    }
+
+    fn parse_libc_version(output: &[u8]) -> Option<&'static str> {
+        let s = String::from_utf8_lossy(output);
+        if s.contains("musl libc") {
+            Some("musl")
+        } else if s.contains("GLIBC") {
+            Some("gnu")
+        } else {
+            None
+        }
+    }
+
+    const fn parse_abi() -> &'static str {
+        if TARGET.endswith("abi64") {
+            "abi64"
+        } else if TARGET.endswith("eabi") {
+            "eabi"
+        } else if TARGET.endswith("eabihf") {
+            "eabihf"
+        } else if TARGET.endswith("gnu") || TARGET.endswith("musl") {
+            ""
+        } else {
+            panic!("Unknown abi")
+        }
+    }
+
+    fn create_target_str(libc_version: &str, abi: &str) -> Box<str> {
+        let prefix = TARGET.rsplit_once('-').unwrap().0;
+
+        let mut target = String::with_capacity(prefix.len() + 1 + libc_version.len() + abi.len());
+        target.push_str(prefix);
+        target.push('-');
+        target.push_str(libc_version);
+        target.push_str(abi);
+
+        target.into_boxed_str()
+    }
+}