//! Day 04 of 2020.

use crate::prelude::*;

/// Get the solution for day 04 of 2020.
pub fn solution() -> Solution {
  Solution::new(Day::new(4, 2020), part_1, part_2).with_expected(237, 172)
}

/// The passport puzzle input.
#[derive(Debug, Clone)]
struct Passport {
  /// Birth year.
  byr: Option<String>,
  /// Issue year.
  iyr: Option<String>,
  /// Expiration year.
  eyr: Option<String>,
  /// Height.
  hgt: Option<String>,
  /// Hair color.
  hcl: Option<String>,
  /// Eye color.
  ecl: Option<String>,
  /// Passport ID.
  pid: Option<String>,
  /// Country ID.
  cid: Option<String>,
}

/// Parse the puzzle input into a list of passports.
fn parse_passports(input: &str) -> Vec<Passport> {
  let mut passports = vec![];
  let blank = Passport {
    byr: None,
    iyr: None,
    eyr: None,
    hgt: None,
    hcl: None,
    ecl: None,
    pid: None,
    cid: None,
  };
  let mut intermediate = blank.clone();

  for line in input.lines() {
    if line.is_empty() {
      passports.push(intermediate.clone());
      intermediate = blank.clone();
      continue;
    }

    let components = line.split(' ');
    for component in components {
      let colon_index = component.find(':').unwrap();
      let key = &component[0..colon_index];
      let value = &component[colon_index + 1..];
      match key {
        "byr" => intermediate.byr = Some(value.to_string()),
        "iyr" => intermediate.iyr = Some(value.to_string()),
        "eyr" => intermediate.eyr = Some(value.to_string()),
        "hgt" => intermediate.hgt = Some(value.to_string()),
        "hcl" => intermediate.hcl = Some(value.to_string()),
        "ecl" => intermediate.ecl = Some(value.to_string()),
        "pid" => intermediate.pid = Some(value.to_string()),
        "cid" => intermediate.cid = Some(value.to_string()),
        _ => unreachable!("{key}"),
      };
    }
  }

  passports
}

/// The logic to solve part one.
fn part_1(input: &str) -> Result<String> {
  Ok(
    parse_passports(input)
      .into_iter()
      .filter(|passport| {
        passport.byr.is_some()
          && passport.iyr.is_some()
          && passport.eyr.is_some()
          && passport.hgt.is_some()
          && passport.hcl.is_some()
          && passport.ecl.is_some()
          && passport.pid.is_some()
      })
      .count()
      .to_string(),
  )
}

/// The logic to solve part two.
fn part_2(input: &str) -> Result<String> {
  let hcl_regex = Regex::new("^#[a-fA-F0-9]{6}$").unwrap();
  let pid_regex = Regex::new("^[0-9]{9}$").unwrap();

  let ecl_values = vec![
    "amb".to_string(),
    "blu".to_string(),
    "brn".to_string(),
    "gry".to_string(),
    "grn".to_string(),
    "hzl".to_string(),
    "oth".to_string(),
  ];

  Ok(
    parse_passports(input)
      .into_iter()
      .filter(|passport| {
        passport.byr.is_some()
          && passport.iyr.is_some()
          && passport.eyr.is_some()
          && passport.hgt.is_some()
          && passport.hcl.is_some()
          && passport.ecl.is_some()
          && passport.pid.is_some()
      })
      .filter(|passport| {
        let byr = passport
          .byr
          .as_ref()
          .unwrap()
          .parse::<i32>()
          .unwrap_or_default();
        (1920..=2002).contains(&byr)
      })
      .filter(|passport| {
        let iyr = passport
          .iyr
          .as_ref()
          .unwrap()
          .parse::<i32>()
          .unwrap_or_default();
        (2010..=2020).contains(&iyr)
      })
      .filter(|passport| {
        let eyr = passport
          .eyr
          .as_ref()
          .unwrap()
          .parse::<i32>()
          .unwrap_or_default();
        (2020..=2030).contains(&eyr)
      })
      .filter(|passport| {
        let hgt = passport.hgt.as_ref().unwrap();
        match &hgt[hgt.len() - 2..] {
          "cm" => {
            let value =
              hgt[0..hgt.len() - 2].parse::<i32>().unwrap_or_default();
            (150..=193).contains(&value)
          }
          "in" => {
            let value =
              hgt[0..hgt.len() - 2].parse::<i32>().unwrap_or_default();
            (59..=76).contains(&value)
          }
          _ => false,
        }
      })
      .filter(|passport| {
        let hcl = passport.hcl.as_ref().unwrap();
        hcl_regex.is_match(hcl)
      })
      .filter(|passport| {
        let ecl = passport.ecl.as_ref().unwrap();
        ecl_values.contains(ecl)
      })
      .filter(|passport| {
        let pid = passport.pid.as_ref().unwrap();
        pid_regex.is_match(pid)
      })
      .count()
      .to_string(),
  )
}