Discussion on: Advent of Code 2020 Solution Megathread - Day 4: Passport Processing

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "regexp"
    "strconv"
    "strings"
)

var requiredAttributes = []string{"byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"}

func isValid(passport map[string]string) bool {
    for _, attribute := range requiredAttributes {
        if _, exists := passport[attribute]; !exists {
            return false
        }
    }

    return true
}

func exists(slice []string, val string) bool {
    for _, item := range slice {
        if item == val {
            return true
        }
    }
    return false
}

func validateRange(val string, lower, upper int) bool {
    num, err := strconv.Atoi(val)
    return err == nil && num >= lower && num <= upper
}

func isValidV2(passport map[string]string) bool {
    for attr, val := range passport {
        switch attr {
        case "byr":
            if !validateRange(val, 1920, 2002) {
                return false
            }
        case "iyr":
            if !validateRange(val, 2010, 2020) {
                return false
            }
        case "eyr":
            if !validateRange(val, 2020, 2030) {
                return false
            }

        case "hgt":
            if strings.HasSuffix(val, "cm") {
                if !validateRange(strings.TrimSuffix(val, "cm"), 150, 193) {
                    return false
                }
            } else if strings.HasSuffix(val, "in") {
                if !validateRange(strings.TrimSuffix(val, "in"), 59, 76) {
                    return false
                }
            } else {
                return false
            }

        case "hcl":
            if match, _ := regexp.MatchString("^#[0-9a-f]{6}$", val); !match {
                return false
            }

        case "ecl":
            eyeColors := []string{"amb", "blu", "brn", "gry", "grn", "hzl", "oth"}
            if !exists(eyeColors, val) {
                return false
            }

        case "pid":
            if match, _ := regexp.MatchString("^[0-9]{9}$", val); !match {
                return false
            }
        }
    }

    return true
}

func main() {
    reader := bufio.NewReader(os.Stdin)
    passport := make(map[string]string, 8)

    numValid, numValidV2 := 0, 0
    for {
        var line string
        line, err := reader.ReadString('\n')
        if err == io.EOF {
            break
        }

        line = strings.TrimSpace(line)

        if len(line) == 0 {
            // passport complete
            if isValid(passport) {
                numValid++
                if isValidV2(passport) {
                    numValidV2++
                }
            }
            // reset passport
            passport = make(map[string]string, 8)
        } else {
            parts := strings.Split(line, " ")
            for _, part := range parts {
                attribute := strings.Split(part, ":")
                passport[attribute[0]] = attribute[1]
            }
        }
    }

    // last one is special snowflake, as file does not end with 2 newlines
    if isValid(passport) {
        numValid++
        if isValidV2(passport) {
            numValidV2++
        }
    }

    fmt.Println(numValid, numValidV2)
}