Complete day 4.1

day-4/src/main.rs

@@ -0,0 +1,80 @@
+use std::collections::HashMap;
+use std::fs;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let input = fs::read_to_string("input")?;
+    let passports = parse_passports(&input)?;
+    println!("{}", validate_passports(&passports));
+
+    Ok(())
+}
+
+fn parse_passports(input: &str) -> Result<Vec<HashMap<&str, &str>>, &str> {
+    input
+        .split("\n\n")
+        .map(|passport| {
+            passport
+                .trim()
+                .split(|c| c == ' ' || c == '\n')
+                .map(|field| {
+                    let split = field
+                        .find(':')
+                        .ok_or("Invalid passport entry; no separator")?;
+                    let item = field.split_at(split);
+
+                    let key = item.0;
+                    let value = item
+                        .1
+                        .strip_prefix(":")
+                        .expect("We've already checked the separator exists");
+
+                    Ok((key, value))
+                })
+                .collect()
+        })
+        .collect()
+}
+
+fn validate_passports(passports: &Vec<HashMap<&str, &str>>) -> usize {
+    let required_fields = ["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"];
+
+    passports
+        .iter()
+        .filter(|passport| {
+            required_fields
+                .iter()
+                .all(|field| passport.contains_key(field))
+        })
+        .count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+
+    #[test]
+    fn test_simple() -> Result<(), String> {
+        let example = indoc!(
+            "ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
+             byr:1937 iyr:2017 cid:147 hgt:183cm
+
+             iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
+             hcl:#cfa07d byr:1929
+
+             hcl:#ae17e1 iyr:2013
+             eyr:2024
+             ecl:brn pid:760753108 byr:1931
+             hgt:179cm
+
+             hcl:#cfa07d eyr:2025 pid:166559648
+             iyr:2011 ecl:brn hgt:59in
+             "
+        );
+
+        let passports = parse_passports(example)?;
+        assert_eq!(validate_passports(&passports), 2);
+
+        Ok(())
+    }
+}