diff --git a/minigrep/src/lib.rs b/minigrep/src/lib.rs
index a5cbc19..2e9a8ce 100644
--- a/minigrep/src/lib.rs
+++ b/minigrep/src/lib.rs
@@ -8,6 +8,27 @@ pub struct Config {
 }
 
 impl Config {
+    pub fn build(mut args: impl Iterator<Item = String>) -> Result<Config, &'static str> {
+        args.next();
+
+        let query = match args.next() {
+            Some(arg) => arg,
+            None => return Err("query not provided"),
+        };
+
+        let file_path = match args.next() {
+            Some(arg) => arg,
+            None => return Err("file path not provided"),
+        };
+
+        let ignore_case = env::var("IGNORE_CASE").is_ok();
+        Ok(Config {
+            query,
+            file_path,
+            ignore_case,
+        })
+    }
+
     pub fn new(args: &[String]) -> Result<Config, &'static str> {
         if args.len() < 3 {
             return Err("not enough arguments");
@@ -28,8 +49,10 @@ impl Config {
 pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
     let contents = fs::read_to_string(config.file_path)?;
     let results = if config.ignore_case {
+        println!("Ignoring case");
         search_case_insensitive(&config.query, &contents)
     } else {
+        println!("Case sensitive");
         search(&config.query, &contents)
     };
 
@@ -80,24 +103,32 @@ Trust me.";
 }
 
 pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
-    let mut result = Vec::new();
-    for line in contents.lines() {
-        if line.contains(&query) {
-            result.push(line);
-        }
-    }
-    result
+    // let mut result = Vec::new();
+    // for line in contents.lines() {
+    //     if line.contains(&query) {
+    //         result.push(line);
+    //     }
+    // }
+    // result
+    contents
+        .lines()
+        .filter(|line| line.contains(&query))
+        .collect()
 }
 
 pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
-    let query = query.to_lowercase();
-    let mut result = Vec::new();
+    // let query = query.to_lowercase();
+    // let mut result = Vec::new();
 
-    for line in contents.lines() {
-        if line.to_lowercase().contains(&query) {
-            result.push(line);
-        }
-    }
+    // for line in contents.lines() {
+    //     if line.to_lowercase().contains(&query) {
+    //         result.push(line);
+    //     }
+    // }
 
-    result
+    // result
+    contents
+        .lines()
+        .filter(|line| line.to_lowercase().contains(&query.to_lowercase()))
+        .collect()
 }
diff --git a/minigrep/src/main.rs b/minigrep/src/main.rs
index 433af04..9854078 100644
--- a/minigrep/src/main.rs
+++ b/minigrep/src/main.rs
@@ -4,9 +4,13 @@ use std::process;
 use minigrep::Config;
 
 fn main() {
-    let args: Vec<String> = env::args().collect();
-    let config = Config::new(&args).unwrap_or_else(|err| {
-        println!("Problem parsing arguments: {}", err);
+    // let args: Vec<String> = env::args().collect();
+    // let config = Config::new(&args).unwrap_or_else(|err| {
+    //     eprintln!("Problem parsing arguments: {}", err);
+    //     process::exit(1);
+    // });
+    let config = Config::build(env::args()).unwrap_or_else(|err| {
+        eprintln!("Problem parsing arguments: {}", err);
         process::exit(1);
     });
 
@@ -14,7 +18,7 @@ fn main() {
     println!("In file {}", config.file_path);
 
     if let Err(e) = minigrep::run(config) {
-        println!("Application error: {}", e);
+        eprintln!("Application error: {}", e);
         process::exit(1);
     }
 }