function for trim spaces. good example for string iteration, borrowing, bytes datatype etc.

trim_spaces.rs

fn main() {
    let test1 = "We need more space.";
    assert_eq!(trim_spaces(test1), "We need more space.");
    
    let test2 = String::from("   There's space in front.");
    assert_eq!(trim_spaces(&test2), "There's space in front.");
    
    let test3 = String::from("There's space to the rear. ");
    assert_eq!(trim_spaces(&test3[..]), "There's space to the rear.");   
    
    let test4 = "  We're surrounded by space!    ";
    assert_eq!(trim_spaces(test4), "We're surrounded by space!");
    
    let test5 = "     ";
    assert_eq!(trim_spaces(test5), "");
    
    let test6 = "";
    assert_eq!(trim_spaces(test6), "");
    
    let test7 = " 🚀 ";
    assert_eq!(trim_spaces(test7), "🚀");
    println!("Tests passed!");
}

/* YOUR CODE GOES HERE */
fn trim_spaces(orig: &str) -> &str {
    // algo: iterate from beginning until the first non-space character
    // then iterate from end until first non-space character
    // to obtain start and end indexes to return
    let mut start = 0;
    let mut end = 0;

    for (i, &c) in orig.as_bytes().iter().enumerate() {
        if c != b' ' {
            // found first non-space char
            println!("found {} {:?}", i, c);
            start = i;
            break
        }   
    }

    println!("bytes len: {}", orig.len());

    for (i, &c) in orig.as_bytes().iter().enumerate().rev() { // in reverse

        println!("rev {} {}", i ,c);
        if c != b' ' {
            // found first non-space char
            println!("found end {} {}", i, c);
            end = i + 1;
            break
        }

    }
    
    &orig[start..end]

}