[refactor] optimize string formatting, cleanup imports, and implement default trait for backends

src/backend.rs

@@ -98,24 +98,36 @@ impl CpuBackend {
         CpuBackend
     }
 }
+impl Default for CpuBackend {
+    fn default() -> Self { Self::new() }
+}
 impl CudaBackend {
     /// Create a new CUDA backend instance.
     pub fn new() -> Self {
         CudaBackend
     }
 }
+impl Default for CudaBackend {
+    fn default() -> Self { Self::new() }
+}
 impl HipBackend {
     /// Create a new HIP backend instance.
     pub fn new() -> Self {
         HipBackend
     }
 }
+impl Default for HipBackend {
+    fn default() -> Self { Self::new() }
+}
 impl VulkanBackend {
     /// Create a new Vulkan backend instance.
     pub fn new() -> Self {
         VulkanBackend
     }
 }
+impl Default for VulkanBackend {
+    fn default() -> Self { Self::new() }
+}
 
 impl TranscribeBackend for CpuBackend {
     fn kind(&self) -> BackendKind {
@@ -311,7 +323,7 @@ pub(crate) fn transcribe_with_whisper_rs(
     }
 
     // Suppress stderr from whisper/ggml during model load and inference when quiet and not verbose.
-    let (ctx, mut state) = crate::with_suppressed_stderr(|| {
+    let (_ctx, mut state) = crate::with_suppressed_stderr(|| {
         let cparams = whisper_rs::WhisperContextParameters::default();
         let ctx = whisper_rs::WhisperContext::new_with_params(model_str, cparams)
             .with_context(|| format!("Failed to load Whisper model at {}", model.display()))?;

src/main.rs

@@ -1,8 +1,6 @@
 use std::fs::{File, create_dir_all};
 use std::io::{self, Read, Write};
 use std::path::{Path, PathBuf};
-#[cfg(unix)]
-use std::os::unix::io::AsRawFd;
 
 use anyhow::{Context, Result, anyhow};
 use clap::{Parser, Subcommand};
@@ -774,7 +772,6 @@ fn main() {
 mod tests {
     use super::*;
     use clap::CommandFactory;
-    use polyscribe::backend::*;
     use polyscribe::format_srt_time;
     use std::env as std_env;
     use std::fs;

src/models.rs

@@ -81,14 +81,14 @@ fn human_size(bytes: u64) -> String {
     } else if b >= KB {
         format!("{:.2} KiB", b / KB)
     } else {
-        format!("{} B", bytes)
+        format!("{bytes} B")
     }
 }
 
 fn to_hex_lower(bytes: &[u8]) -> String {
     let mut s = String::with_capacity(bytes.len() * 2);
     for b in bytes {
-        s.push_str(&format!("{:02x}", b));
+        s.push_str(&format!("{b:02x}"));
     }
     s
 }
@@ -159,8 +159,7 @@ fn fill_meta_via_head(repo: &str, name: &str) -> (Option<u64>, Option<String>) {
         Err(_) => return (None, None),
     };
     let url = format!(
-        "https://huggingface.co/{}/resolve/main/ggml-{}.bin",
-        repo, name
+        "https://huggingface.co/{repo}/resolve/main/ggml-{name}.bin"
     );
     let resp = match head_client
         .head(url)
@@ -207,8 +206,7 @@ fn hf_fetch_repo_models(client: &Client, repo: &'static str) -> Result<Vec<Model
     }
     // Prefer the tree endpoint for reliable size/hash metadata, then fall back to model metadata
     let tree_url = format!(
-        "https://huggingface.co/api/models/{}/tree/main?recursive=1",
-        repo
+        "https://huggingface.co/api/models/{repo}/tree/main?recursive=1"
     );
     let mut out: Vec<ModelEntry> = Vec::new();
 
@@ -249,7 +247,7 @@ fn hf_fetch_repo_models(client: &Client, repo: &'static str) -> Result<Vec<Model
     }
 
     if out.is_empty() {
-        let url = format!("https://huggingface.co/api/models/{}", repo);
+        let url = format!("https://huggingface.co/api/models/{repo}");
         let resp = client
             .get(url)
             .send()
@@ -286,13 +284,13 @@ fn hf_fetch_repo_models(client: &Client, repo: &'static str) -> Result<Vec<Model
     }
 
     // Fill missing metadata (size/hash) via HEAD request if necessary
-    if out.iter().any(|m| m.size == 0 || m.sha256.is_none()) {
-        if !(crate::is_no_interaction() && crate::verbose_level() < 2) {
-            ilog!(
-                "Fetching online data: completing metadata checks for models in {}...",
-                repo
-            );
-        }
+    if out.iter().any(|m| m.size == 0 || m.sha256.is_none())
+        && !(crate::is_no_interaction() && crate::verbose_level() < 2)
+    {
+        ilog!(
+            "Fetching online data: completing metadata checks for models in {}...",
+            repo
+        );
     }
     for m in out.iter_mut() {
         if m.size == 0 || m.sha256.is_none() {
@@ -374,8 +372,8 @@ fn format_model_list(models: &[ModelEntry]) -> String {
     for m in models.iter() {
         if m.base != current {
             current = m.base.clone();
-            out.push_str("\n");
-            out.push_str(&format!("{}:\n", current));
+            out.push('\n');
+            out.push_str(&format!("{current}:\n"));
         }
         // Format without hash and with aligned columns
         out.push_str(&format!(
@@ -406,7 +404,7 @@ fn prompt_select_models_two_stage(models: &[ModelEntry]) -> Result<Vec<ModelEntr
     for m in models.iter() {
         if m.base != last {
             // models are sorted by base; avoid duplicates while preserving order
-            if bases.last().map(|b| b == &m.base).unwrap_or(false) == false {
+            if !bases.last().map(|b| b == &m.base).unwrap_or(false) {
                 bases.push(m.base.clone());
             }
             last = m.base.clone();

tests/integration_cli.rs

@@ -7,6 +7,7 @@ use chrono::Local;
 use serde::Deserialize;
 
 #[derive(Deserialize)]
+#[allow(dead_code)]
 struct OutputEntry {
     id: u64,
     speaker: String,
@@ -257,7 +258,7 @@ fn cli_merge_and_separate_writes_both_kinds_of_outputs() {
 #[test]
 fn cli_set_speaker_names_merge_prompts_and_uses_names() {
     // Also validate that -q does not suppress prompts by running with -q
-    use std::io::{Read as _, Write as _};
+    use std::io::Write as _;
     use std::process::Stdio;
 
     let exe = env!("CARGO_BIN_EXE_polyscribe");