cleanup

eh/src/build.rs

@@ -1,5 +1,85 @@
-use crate::util::run_nix_cmd;
+use crate::command::{NixCommand, StdIoInterceptor};
+use crate::util::{HashExtractor, NixErrorClassifier, NixFileFixer};
+use std::io::Write;
 
-pub fn handle_nix_build(args: &[String]) {
-    run_nix_cmd("build", args);
+pub fn handle_nix_build(
+    args: &[String],
+    hash_extractor: &dyn HashExtractor,
+    fixer: &dyn NixFileFixer,
+    classifier: &dyn NixErrorClassifier,
+) {
+    let mut cmd = NixCommand::new("build").print_build_logs(true);
+    for arg in args {
+        cmd = cmd.arg(arg);
+    }
+    let status = cmd
+        .run_with_logs(StdIoInterceptor)
+        .expect("failed to run nix build");
+    if status.success() {
+        return;
+    }
+
+    let output = NixCommand::new("build")
+        .print_build_logs(true)
+        .args(args.iter().cloned())
+        .output()
+        .expect("failed to capture output");
+    let stderr = String::from_utf8_lossy(&output.stderr);
+
+    if let Some(new_hash) = hash_extractor.extract_hash(&stderr) {
+        if fixer.fix_hash_in_files(&new_hash) {
+            eprintln!("\x1b[32m✔ Fixed hash mismatch, retrying...\x1b[0m");
+            let retry_status = NixCommand::new("build")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    if classifier.should_retry(&stderr) {
+        if stderr.contains("unfree") {
+            eprintln!(
+                "\x1b[33m⚠ Unfree package detected, retrying with NIXPKGS_ALLOW_UNFREE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("build")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_UNFREE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("insecure") {
+            eprintln!(
+                "\x1b[33m⚠ Insecure package detected, retrying with NIXPKGS_ALLOW_INSECURE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("build")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_INSECURE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("broken") {
+            eprintln!(
+                "\x1b[33m⚠ Broken package detected, retrying with NIXPKGS_ALLOW_BROKEN=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("build")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_BROKEN", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    std::io::stderr().write_all(output.stderr.as_ref()).unwrap();
+    std::process::exit(status.code().unwrap_or(1));
 }

eh/src/command.rs

@@ -0,0 +1,157 @@
+use std::collections::VecDeque;
+use std::io::{self, Read, Write};
+use std::process::{Command, ExitStatus, Output, Stdio};
+
+/// Trait for log interception and output handling.
+pub trait LogInterceptor: Send {
+    fn on_stderr(&mut self, chunk: &[u8]);
+    fn on_stdout(&mut self, chunk: &[u8]);
+}
+
+/// Default log interceptor that just writes to stdio.
+pub struct StdIoInterceptor;
+
+impl LogInterceptor for StdIoInterceptor {
+    fn on_stderr(&mut self, chunk: &[u8]) {
+        let _ = io::stderr().write_all(chunk);
+    }
+    fn on_stdout(&mut self, chunk: &[u8]) {
+        let _ = io::stdout().write_all(chunk);
+    }
+}
+
+/// Builder and executor for Nix commands.
+pub struct NixCommand {
+    subcommand: String,
+    args: Vec<String>,
+    env: Vec<(String, String)>,
+    impure: bool,
+    print_build_logs: bool,
+}
+
+impl NixCommand {
+    pub fn new<S: Into<String>>(subcommand: S) -> Self {
+        Self {
+            subcommand: subcommand.into(),
+            args: Vec::new(),
+            env: Vec::new(),
+            impure: false,
+            print_build_logs: true,
+        }
+    }
+
+    pub fn arg<S: Into<String>>(mut self, arg: S) -> Self {
+        self.args.push(arg.into());
+        self
+    }
+
+    pub fn args<I, S>(mut self, args: I) -> Self
+    where
+        I: IntoIterator<Item = S>,
+        S: Into<String>,
+    {
+        self.args.extend(args.into_iter().map(Into::into));
+        self
+    }
+
+    pub fn env<K: Into<String>, V: Into<String>>(mut self, key: K, value: V) -> Self {
+        self.env.push((key.into(), value.into()));
+        self
+    }
+
+    pub fn impure(mut self, yes: bool) -> Self {
+        self.impure = yes;
+        self
+    }
+
+    pub fn print_build_logs(mut self, yes: bool) -> Self {
+        self.print_build_logs = yes;
+        self
+    }
+
+    /// Run the command, streaming output to the provided interceptor.
+    pub fn run_with_logs<I: LogInterceptor + 'static>(
+        &self,
+        mut interceptor: I,
+    ) -> io::Result<ExitStatus> {
+        let mut cmd = Command::new("nix");
+        cmd.arg(&self.subcommand);
+
+        if self.print_build_logs && !self.args.iter().any(|a| a == "--no-build-output") {
+            cmd.arg("--print-build-logs");
+        }
+        if self.impure {
+            cmd.arg("--impure");
+        }
+        for (k, v) in &self.env {
+            cmd.env(k, v);
+        }
+        cmd.args(&self.args);
+        cmd.stdout(Stdio::piped());
+        cmd.stderr(Stdio::piped());
+
+        let mut child = cmd.spawn()?;
+        let mut stdout = child.stdout.take().unwrap();
+        let mut stderr = child.stderr.take().unwrap();
+
+        let mut out_buf = [0u8; 4096];
+        let mut err_buf = [0u8; 4096];
+
+        let mut out_queue = VecDeque::new();
+        let mut err_queue = VecDeque::new();
+
+        loop {
+            let mut did_something = false;
+
+            match stdout.read(&mut out_buf) {
+                Ok(0) => {}
+                Ok(n) => {
+                    interceptor.on_stdout(&out_buf[..n]);
+                    out_queue.push_back(Vec::from(&out_buf[..n]));
+                    did_something = true;
+                }
+                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
+                Err(e) => return Err(e),
+            }
+
+            match stderr.read(&mut err_buf) {
+                Ok(0) => {}
+                Ok(n) => {
+                    interceptor.on_stderr(&err_buf[..n]);
+                    err_queue.push_back(Vec::from(&err_buf[..n]));
+                    did_something = true;
+                }
+                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
+                Err(e) => return Err(e),
+            }
+
+            if !did_something && child.try_wait()?.is_some() {
+                break;
+            }
+        }
+
+        let status = child.wait()?;
+        Ok(status)
+    }
+
+    /// Run the command and capture all output.
+    pub fn output(&self) -> io::Result<Output> {
+        let mut cmd = Command::new("nix");
+        cmd.arg(&self.subcommand);
+
+        if self.print_build_logs && !self.args.iter().any(|a| a == "--no-build-output") {
+            cmd.arg("--print-build-logs");
+        }
+        if self.impure {
+            cmd.arg("--impure");
+        }
+        for (k, v) in &self.env {
+            cmd.env(k, v);
+        }
+        cmd.args(&self.args);
+        cmd.stdout(Stdio::piped());
+        cmd.stderr(Stdio::piped());
+
+        cmd.output()
+    }
+}

eh/src/main.rs

@@ -3,6 +3,7 @@ use std::env;
 use std::path::Path;
 
 mod build;
+mod command;
 mod run;
 mod shell;
 mod util;
@@ -45,17 +46,26 @@ fn main() {
     match app_name {
         "nr" => {
             let rest: Vec<String> = args.collect();
-            run::handle_nix_run(&rest);
+            let hash_extractor = util::RegexHashExtractor;
+            let fixer = util::DefaultNixFileFixer;
+            let classifier = util::DefaultNixErrorClassifier;
+            run::handle_nix_run(&rest, &hash_extractor, &fixer, &classifier);
             return;
         }
         "ns" => {
             let rest: Vec<String> = args.collect();
-            shell::handle_nix_shell(&rest);
+            let hash_extractor = util::RegexHashExtractor;
+            let fixer = util::DefaultNixFileFixer;
+            let classifier = util::DefaultNixErrorClassifier;
+            shell::handle_nix_shell(&rest, &hash_extractor, &fixer, &classifier);
             return;
         }
         "nb" => {
             let rest: Vec<String> = args.collect();
-            build::handle_nix_build(&rest);
+            let hash_extractor = util::RegexHashExtractor;
+            let fixer = util::DefaultNixFileFixer;
+            let classifier = util::DefaultNixErrorClassifier;
+            build::handle_nix_build(&rest, &hash_extractor, &fixer, &classifier);
             return;
         }
         _ => {}
@@ -63,10 +73,20 @@ fn main() {
 
     let cli = Cli::parse();
 
+    let hash_extractor = util::RegexHashExtractor;
+    let fixer = util::DefaultNixFileFixer;
+    let classifier = util::DefaultNixErrorClassifier;
+
     match cli.command {
-        Some(Command::Run { args }) => run::handle_nix_run(&args),
-        Some(Command::Shell { args }) => shell::handle_nix_shell(&args),
-        Some(Command::Build { args }) => build::handle_nix_build(&args),
+        Some(Command::Run { args }) => {
+            run::handle_nix_run(&args, &hash_extractor, &fixer, &classifier);
+        }
+        Some(Command::Shell { args }) => {
+            shell::handle_nix_shell(&args, &hash_extractor, &fixer, &classifier);
+        }
+        Some(Command::Build { args }) => {
+            build::handle_nix_build(&args, &hash_extractor, &fixer, &classifier);
+        }
         None => {
             Cli::command().print_help().unwrap();
             println!();

eh/src/run.rs

@@ -1,5 +1,85 @@
-use crate::util::run_nix_cmd;
+use crate::command::{NixCommand, StdIoInterceptor};
+use crate::util::{HashExtractor, NixErrorClassifier, NixFileFixer};
+use std::io::Write;
 
-pub fn handle_nix_run(args: &[String]) {
-    run_nix_cmd("run", args);
+pub fn handle_nix_run(
+    args: &[String],
+    hash_extractor: &dyn HashExtractor,
+    fixer: &dyn NixFileFixer,
+    classifier: &dyn NixErrorClassifier,
+) {
+    let mut cmd = NixCommand::new("run").print_build_logs(true);
+    for arg in args {
+        cmd = cmd.arg(arg);
+    }
+    let status = cmd
+        .run_with_logs(StdIoInterceptor)
+        .expect("failed to run nix run");
+    if status.success() {
+        return;
+    }
+
+    let output = NixCommand::new("run")
+        .print_build_logs(true)
+        .args(args.iter().cloned())
+        .output()
+        .expect("failed to capture output");
+    let stderr = String::from_utf8_lossy(&output.stderr);
+
+    if let Some(new_hash) = hash_extractor.extract_hash(&stderr) {
+        if fixer.fix_hash_in_files(&new_hash) {
+            eprintln!("\x1b[32m✔ Fixed hash mismatch, retrying...\x1b[0m");
+            let retry_status = NixCommand::new("run")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    if classifier.should_retry(&stderr) {
+        if stderr.contains("unfree") {
+            eprintln!(
+                "\x1b[33m⚠ Unfree package detected, retrying with NIXPKGS_ALLOW_UNFREE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("run")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_UNFREE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("insecure") {
+            eprintln!(
+                "\x1b[33m⚠ Insecure package detected, retrying with NIXPKGS_ALLOW_INSECURE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("run")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_INSECURE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("broken") {
+            eprintln!(
+                "\x1b[33m⚠ Broken package detected, retrying with NIXPKGS_ALLOW_BROKEN=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("run")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_BROKEN", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    std::io::stderr().write_all(output.stderr.as_ref()).unwrap();
+    std::process::exit(status.code().unwrap_or(1));
 }

eh/src/shell.rs

@@ -1,5 +1,85 @@
-use crate::util::run_nix_cmd;
+use crate::command::{NixCommand, StdIoInterceptor};
+use crate::util::{HashExtractor, NixErrorClassifier, NixFileFixer};
+use std::io::Write;
 
-pub fn handle_nix_shell(args: &[String]) {
-    run_nix_cmd("shell", args);
+pub fn handle_nix_shell(
+    args: &[String],
+    hash_extractor: &dyn HashExtractor,
+    fixer: &dyn NixFileFixer,
+    classifier: &dyn NixErrorClassifier,
+) {
+    let mut cmd = NixCommand::new("shell").print_build_logs(true);
+    for arg in args {
+        cmd = cmd.arg(arg);
+    }
+    let status = cmd
+        .run_with_logs(StdIoInterceptor)
+        .expect("failed to run nix shell");
+    if status.success() {
+        return;
+    }
+
+    let output = NixCommand::new("shell")
+        .print_build_logs(true)
+        .args(args.iter().cloned())
+        .output()
+        .expect("failed to capture output");
+    let stderr = String::from_utf8_lossy(&output.stderr);
+
+    if let Some(new_hash) = hash_extractor.extract_hash(&stderr) {
+        if fixer.fix_hash_in_files(&new_hash) {
+            eprintln!("\x1b[32m✔ Fixed hash mismatch, retrying...\x1b[0m");
+            let retry_status = NixCommand::new("shell")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    if classifier.should_retry(&stderr) {
+        if stderr.contains("unfree") {
+            eprintln!(
+                "\x1b[33m⚠ Unfree package detected, retrying with NIXPKGS_ALLOW_UNFREE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("shell")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_UNFREE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("insecure") {
+            eprintln!(
+                "\x1b[33m⚠ Insecure package detected, retrying with NIXPKGS_ALLOW_INSECURE=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("shell")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_INSECURE", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+        if stderr.contains("broken") {
+            eprintln!(
+                "\x1b[33m⚠ Broken package detected, retrying with NIXPKGS_ALLOW_BROKEN=1...\x1b[0m"
+            );
+            let retry_status = NixCommand::new("shell")
+                .print_build_logs(true)
+                .args(args.iter().cloned())
+                .env("NIXPKGS_ALLOW_BROKEN", "1")
+                .impure(true)
+                .run_with_logs(StdIoInterceptor)
+                .unwrap();
+            std::process::exit(retry_status.code().unwrap_or(1));
+        }
+    }
+
+    std::io::stderr().write_all(output.stderr.as_ref()).unwrap();
+    std::process::exit(status.code().unwrap_or(1));
 }

eh/src/util.rs

@@ -1,195 +1,123 @@
 use regex::Regex;
 use std::fs;
-use std::io::{self, Write};
-use std::path::Path;
-use std::process::{Command as StdCommand, Stdio};
+use std::path::{Path, PathBuf};
 
-pub fn extract_hash_from_error(stderr: &str) -> Option<String> {
-    let patterns = [
-        r"got:\s+([a-zA-Z0-9+/=]+)",
-        r"actual:\s+([a-zA-Z0-9+/=]+)",
-        r"have:\s+([a-zA-Z0-9+/=]+)",
-    ];
-
-    for pattern in &patterns {
-        if let Ok(re) = Regex::new(pattern) {
-            if let Some(captures) = re.captures(stderr) {
-                if let Some(hash) = captures.get(1) {
-                    return Some(hash.as_str().to_string());
-                }
-            }
-        }
-    }
-    None
+pub trait HashExtractor {
+    fn extract_hash(&self, stderr: &str) -> Option<String>;
 }
 
-pub fn fix_hash_in_files(new_hash: &str) -> bool {
-    let nix_files = find_nix_files();
-    let mut fixed = false;
+pub struct RegexHashExtractor;
 
-    for file_path in nix_files {
-        if fix_hash_in_file(&file_path, new_hash) {
-            println!("Updated hash in {file_path}");
-            fixed = true;
-        }
-    }
-
-    fixed
-}
-
-pub fn find_nix_files() -> Vec<String> {
-    let mut files = Vec::new();
-
-    let candidates = [
-        "default.nix",
-        "package.nix",
-        "shell.nix",
-        "flake.nix",
-        "nix/default.nix",
-        "nix/package.nix",
-        "nix/site.nix",
-    ];
-
-    for candidate in &candidates {
-        if Path::new(*candidate).exists() {
-            files.push((*candidate).to_string());
-        }
-    }
-
-    if let Ok(entries) = fs::read_dir(".") {
-        for entry in entries.flatten() {
-            if let Some(name) = entry.file_name().to_str() {
-                let path = std::path::Path::new(name);
-                if path
-                    .extension()
-                    .is_some_and(|ext| ext.eq_ignore_ascii_case("nix"))
-                    && !files.contains(&name.to_string())
-                {
-                    files.push(name.to_string());
-                }
-            }
-        }
-    }
-
-    files
-}
-
-pub fn fix_hash_in_file(file_path: &str, new_hash: &str) -> bool {
-    if let Ok(content) = fs::read_to_string(file_path) {
+impl HashExtractor for RegexHashExtractor {
+    fn extract_hash(&self, stderr: &str) -> Option<String> {
         let patterns = [
-            (r#"hash\s*=\s*"[^"]*""#, format!(r#"hash = "{new_hash}""#)),
-            (
-                r#"sha256\s*=\s*"[^"]*""#,
-                format!(r#"sha256 = "{new_hash}""#),
-            ),
-            (
-                r#"outputHash\s*=\s*"[^"]*""#,
-                format!(r#"outputHash = "{new_hash}""#),
-            ),
+            r"got:\s+([a-zA-Z0-9+/=]+)",
+            r"actual:\s+([a-zA-Z0-9+/=]+)",
+            r"have:\s+([a-zA-Z0-9+/=]+)",
         ];
-
-        for (pattern, replacement) in &patterns {
+        for pattern in &patterns {
             if let Ok(re) = Regex::new(pattern) {
-                if re.is_match(&content) {
-                    let new_content = re.replace_all(&content, replacement);
-                    if fs::write(file_path, new_content.as_ref()).is_ok() {
-                        return true;
+                if let Some(captures) = re.captures(stderr) {
+                    if let Some(hash) = captures.get(1) {
+                        return Some(hash.as_str().to_string());
                     }
                 }
             }
         }
+        None
     }
-    false
 }
 
-pub fn should_retry_nix_error(stderr: &str) -> bool {
-    if extract_hash_from_error(stderr).is_some() {
-        return true;
-    }
-    (stderr.contains("unfree") && stderr.contains("refusing"))
-        || (stderr.contains("insecure") && stderr.contains("refusing"))
-        || (stderr.contains("broken") && stderr.contains("refusing"))
+pub trait NixFileFixer {
+    fn fix_hash_in_files(&self, new_hash: &str) -> bool;
+    fn find_nix_files(&self) -> Vec<PathBuf>;
+    fn fix_hash_in_file(&self, file_path: &Path, new_hash: &str) -> bool;
 }
 
-pub fn handle_nix_error(subcommand: &str, args: &[String], stderr: &str) {
-    if let Some(new_hash) = extract_hash_from_error(stderr) {
-        if fix_hash_in_files(&new_hash) {
-            println!("Fixed hash mismatch, retrying...");
-            run_nix_cmd(subcommand, args);
-            return;
+pub struct DefaultNixFileFixer;
+
+impl NixFileFixer for DefaultNixFileFixer {
+    fn fix_hash_in_files(&self, new_hash: &str) -> bool {
+        let nix_files = self.find_nix_files();
+        let mut fixed = false;
+        for file_path in nix_files {
+            if self.fix_hash_in_file(&file_path, new_hash) {
+                println!("Updated hash in {}", file_path.display());
+                fixed = true;
+            }
         }
+        fixed
     }
 
-    if stderr.contains("unfree") && stderr.contains("refusing") {
-        println!("Unfree package detected, retrying with NIXPKGS_ALLOW_UNFREE=1...");
-        run_nix_cmd_with_env(subcommand, args, "NIXPKGS_ALLOW_UNFREE", "1");
-        return;
-    }
-
-    if stderr.contains("insecure") && stderr.contains("refusing") {
-        println!("Insecure package detected, retrying with NIXPKGS_ALLOW_INSECURE=1...");
-        run_nix_cmd_with_env(subcommand, args, "NIXPKGS_ALLOW_INSECURE", "1");
-        return;
-    }
-
-    if stderr.contains("broken") && stderr.contains("refusing") {
-        println!("Broken package detected, retrying with NIXPKGS_ALLOW_BROKEN=1...");
-        run_nix_cmd_with_env(subcommand, args, "NIXPKGS_ALLOW_BROKEN", "1");
-        return;
-    }
-
-    io::stderr().write_all(stderr.as_bytes()).unwrap();
-    std::process::exit(1);
-}
-
-pub fn run_nix_cmd(subcommand: &str, args: &[String]) {
-    let mut cmd = StdCommand::new("nix");
-    cmd.arg(subcommand);
-
-    if !args.iter().any(|arg| arg == "--no-build-output") {
-        cmd.arg("--print-build-logs");
-    }
-
-    cmd.args(args);
-    cmd.stderr(Stdio::piped());
-    cmd.stdout(Stdio::inherit());
-
-    let mut child = cmd.spawn().expect("Failed to start nix command");
-    let stderr = child.stderr.take().unwrap();
-
-    let stderr_handle = std::thread::spawn(move || {
-        let mut buffer = Vec::new();
-        std::io::copy(&mut std::io::BufReader::new(stderr), &mut buffer).unwrap();
-        buffer
-    });
-
-    let exit_status = child.wait().expect("Failed to wait for nix command");
-    let stderr_output = stderr_handle.join().unwrap();
-
-    let stderr_str = String::from_utf8_lossy(&stderr_output);
-
-    if !exit_status.success() {
-        if !should_retry_nix_error(&stderr_str) {
-            io::stderr().write_all(&stderr_output).unwrap();
+    fn find_nix_files(&self) -> Vec<PathBuf> {
+        let mut files = Vec::new();
+        let candidates = [
+            "default.nix",
+            "package.nix",
+            "shell.nix",
+            "flake.nix",
+            "nix/default.nix",
+            "nix/package.nix",
+            "nix/site.nix",
+        ];
+        for candidate in &candidates {
+            let path = Path::new(candidate);
+            if path.exists() {
+                files.push(path.to_path_buf());
+            }
         }
-        handle_nix_error(subcommand, args, &stderr_str);
+        if let Ok(entries) = fs::read_dir(".") {
+            for entry in entries.flatten() {
+                let path = entry.path();
+                if let Some(ext) = path.extension() {
+                    if ext.eq_ignore_ascii_case("nix") && !files.contains(&path) {
+                        files.push(path);
+                    }
+                }
+            }
+        }
+        files
+    }
+
+    fn fix_hash_in_file(&self, file_path: &Path, new_hash: &str) -> bool {
+        if let Ok(content) = fs::read_to_string(file_path) {
+            let patterns = [
+                (r#"hash\s*=\s*"[^"]*""#, format!(r#"hash = "{new_hash}""#)),
+                (
+                    r#"sha256\s*=\s*"[^"]*""#,
+                    format!(r#"sha256 = "{new_hash}""#),
+                ),
+                (
+                    r#"outputHash\s*=\s*"[^"]*""#,
+                    format!(r#"outputHash = "{new_hash}""#),
+                ),
+            ];
+            for (pattern, replacement) in &patterns {
+                if let Ok(re) = Regex::new(pattern) {
+                    if re.is_match(&content) {
+                        let new_content = re.replace_all(&content, replacement);
+                        if fs::write(file_path, new_content.as_ref()).is_ok() {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+        false
     }
 }
 
-pub fn run_nix_cmd_with_env(subcommand: &str, args: &[String], env_key: &str, env_value: &str) {
-    let mut cmd = StdCommand::new("nix");
-    cmd.env(env_key, env_value);
-    cmd.arg(subcommand);
-
-    // Add --impure for env var to take effect
-    cmd.arg("--impure");
-
-    if !args.iter().any(|arg| arg == "--no-build-output") {
-        cmd.arg("--print-build-logs");
-    }
-
-    cmd.args(args);
-
-    let exit_status = cmd.status().expect("Failed to retry nix command");
-    std::process::exit(exit_status.code().unwrap_or(1));
+pub trait NixErrorClassifier {
+    fn should_retry(&self, stderr: &str) -> bool;
+}
+
+pub struct DefaultNixErrorClassifier;
+
+impl NixErrorClassifier for DefaultNixErrorClassifier {
+    fn should_retry(&self, stderr: &str) -> bool {
+        RegexHashExtractor.extract_hash(stderr).is_some()
+            || (stderr.contains("unfree") && stderr.contains("refusing"))
+            || (stderr.contains("insecure") && stderr.contains("refusing"))
+            || (stderr.contains("broken") && stderr.contains("refusing"))
+    }
 }