From ef8c0fe7658534d4e999b939595dc9627d331335 Mon Sep 17 00:00:00 2001
From: Tom Kirchner <git@halffull.org>
Date: Wed, 15 Mar 2023 16:29:11 -0700
Subject: [PATCH] On Linux, find the Playdate serial device if possible

This will use the /dev/serial/by-id/usb-Panic_Inc_Playdate_PDU1-*
symlink to find the appropriate serial device, if possible.  If the
PLAYDATE_SERIAL_DEVICE variable is set, that will take precedence.  If
multiple Playdate devices are found, the user is told, and the first is
used.  If none are found, the same /dev/ttyACM0 backup will be used.
---
 Cargo.lock  | 21 ++++++++++++++
 Cargo.toml  |  5 +++-
 src/main.rs | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index c0e8c30..aee8a9f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -145,6 +145,7 @@ dependencies = [
  "serde_derive",
  "structopt",
  "toml",
+ "walkdir",
  "zip",
  "zip-extensions",
 ]
@@ -389,6 +390,15 @@ version = "1.0.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7b4b9743ed687d4b4bcedf9ff5eaa7398495ae14e61cba0a295704edbc7decde"
 
+[[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "semver"
 version = "0.9.0"
@@ -562,6 +572,17 @@ version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
+[[package]]
+name = "walkdir"
+version = "2.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "808cf2735cd4b6866113f648b791c6adc5714537bc222d9347bb203386ffda56"
+dependencies = [
+ "same-file",
+ "winapi",
+ "winapi-util",
+]
+
 [[package]]
 name = "wasi"
 version = "0.10.0+wasi-snapshot-preview1"
diff --git a/Cargo.toml b/Cargo.toml
index 1c80f60..1788b17 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,4 +25,7 @@ serde_derive = "1.0.110"
 structopt = "0.3.14"
 toml = "0.5.6"
 zip = "0.5"
-zip-extensions = "0.6"
\ No newline at end of file
+zip-extensions = "0.6"
+
+[target.'cfg(target_os = "linux")'.dependencies]
+walkdir = "2.3.2"
diff --git a/src/main.rs b/src/main.rs
index 87d3cc3..aac57ae 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,6 +17,9 @@ use zip_extensions::zip_create_from_directory_with_options;
 #[cfg(unix)]
 use anyhow::Context;
 
+#[cfg(target_os = "linux")]
+use walkdir::WalkDir;
+
 mod config;
 
 #[cfg(target_os = "macos")]
@@ -438,7 +441,13 @@ impl Build {
             env::var("PLAYDATE_SERIAL_DEVICE")
                 .unwrap_or(String::from("/dev/cu.usbmodemPDU1_Y0005491")),
         );
-        #[cfg(not(target_os = "macos"))]
+        #[cfg(target_os = "linux")]
+        let modem_path = PathBuf::from(
+            env::var("PLAYDATE_SERIAL_DEVICE")
+                // On Linux, we can use named symlinks to find the device in most cases
+                .unwrap_or(find_serial_device().unwrap_or(String::from("/dev/ttyACM0"))),
+        );
+        #[cfg(all(not(target_os = "linux"), not(target_os = "macos")))]
         let modem_path = PathBuf::from(
             env::var("PLAYDATE_SERIAL_DEVICE").unwrap_or(String::from("/dev/ttyACM0")),
         );
@@ -686,6 +695,75 @@ impl Build {
     }
 }
 
+#[cfg(target_os = "linux")]
+/// Finds the canonical (resolved) path for the Playdate serial device.  If multiple Playdate devices are
+/// found, warns and returns the first.  If none is found, returns None.  If any error occurs,
+/// returns None.
+fn find_serial_device() -> Option<String> {
+    // Walk through this directory to find Playdate device filenames
+    let directory = "/dev/serial/by-id";
+    let filename_prefix = "usb-Panic_Inc_Playdate_PDU1-";
+
+    let walker = WalkDir::new(directory)
+        .min_depth(1)
+        .max_depth(1)
+        // Don't follow links (yet) because we want file_name to give us the name in this directory
+        .follow_links(false)
+        // If there are multiple, we let the user know and take the first; sort so it's consistent.
+        // If the user wants a different one, they can set PLAYDATE_SERIAL_DEVICE.
+        .sort_by_file_name()
+        .into_iter()
+        .filter_entry(|e| {
+            e.file_name()
+                .to_str()
+                .map(|s| s.starts_with(filename_prefix))
+                .unwrap_or(false)
+        })
+        .filter_map(|e| e.ok());
+
+    // See what we found
+    let mut result: Option<PathBuf> = None;
+    for entry in walker {
+        match result {
+            // If there are multiple matches, let the user know, and return the first
+            Some(ref existing) => {
+                println!(
+                    "Found multiple Playdate devices in {}, using first: {}",
+                    directory,
+                    existing.display()
+                );
+                break;
+            }
+            None => {
+                result = Some(entry.into_path());
+            }
+        }
+    }
+
+    if let Some(path) = result {
+        // Fully resolve the link, which should result in something like "/dev/ttyACM0"
+        let resolved = fs::canonicalize(path).ok()?;
+        // Quick check that it did what we expected
+        if resolved
+            .to_str()
+            .map(|s| s.contains("tty"))
+            .unwrap_or(false)
+        {
+            println!("Resolved Playdate serial device to: {}", resolved.display());
+            // Other code expects String paths
+            return Some(resolved.to_string_lossy().into_owned());
+        } else {
+            eprintln!(
+                "Warning: found a device at '{}' but it's not named like we expect.  Using the default.",
+                resolved.display()
+            );
+            return None;
+        }
+    }
+
+    None
+}
+
 #[derive(Debug, StructOpt)]
 struct Package {
     /// Build a specific example from the examples/ dir.