package days

import (
    "fmt"
    "strconv"
    "strings"
    "unicode"

    inputs "../inputs"
)

// Four : advent of code, day four part1 and 2
func Four() {
    requiredFields := []string{
        "byr",
        "iyr",
        "eyr",
        "hgt",
        "ecl",
        "pid",
        "hcl",
        "cid",
    }

    input := inputs.Day4

    passports := strings.Split(input, "\n\n")
    valid := 0
    completeMatch := false

    for i := 0; i < len(passports); i++ {
        for field := 0; field < len(requiredFields); field++ {
            if requiredFields[field] == "cid" {
                continue
            }

            if !strings.Contains(passports[i], requiredFields[field]) {
                completeMatch = false
                break
            } else if !isFieldValid(requiredFields[field], passports[i]) {
                completeMatch = false
                break
            }
            completeMatch = true
        }
        if completeMatch {
            valid++
            completeMatch = false
        }
    }
    fmt.Print("Number of valid passports reported: ")
    fmt.Println(valid)
}

func isFieldValid(field string, passport string) bool {
    passport = strings.Replace(passport, "\n", " ", -1)
    fields := strings.Split(passport, " ")
    for fieldIn := 0; fieldIn < len(fields); fieldIn++ {
        fields[fieldIn] = strings.Replace(fields[fieldIn], "\t", "", -1)
        if strings.Contains(fields[fieldIn], field) {
            fields[fieldIn] = strings.Split(fields[fieldIn], ":")[1]
            switch field {
            case "byr":
                return byr(fields[fieldIn])
            case "iyr":
                return iyr(fields[fieldIn])
            case "eyr":
                return eyr(fields[fieldIn])
            case "hgt":
                return hgt(fields[fieldIn])
            case "ecl":
                return ecl(fields[fieldIn])
            case "pid":
                return pid(fields[fieldIn])
            case "hcl":
                return hcl(fields[fieldIn])
            case "cid":
                return true
            default:
                fmt.Println("not a field")
            }
        }
    }
    return false
}

func hgt(in string) bool {
    // a number followed by either cm or in:
    // If cm, the number must be at least 150 and at most 193.
    // If in, the number must be at least 59 and at most 76.

    if strings.Contains(in, "cm") {
        in = strings.ReplaceAll(in, "cm", "")
        asInt, _ := strconv.Atoi(in)
        return asInt >= 150 && asInt <= 193
    } else if strings.Contains(in, "in") {
        in = strings.ReplaceAll(in, "in", "")
        asInt, _ := strconv.Atoi(in)
        return asInt >= 59 && asInt <= 76
    } else {
        return false
    }
}

func byr(in string) bool {
    // four digits; at least 1920 and at most 2002.
    asInt, _ := strconv.Atoi(in)
    return asInt >= 1920 && asInt <= 2002
}

func iyr(in string) bool {
    // four digits; at least 2010 and at most 2020.
    asInt, _ := strconv.Atoi(in)
    return asInt >= 2010 && asInt <= 2020
}

func eyr(in string) bool {
    // four digits; at least 2020 and at most 2030.
    asInt, _ := strconv.Atoi(in)
    return asInt >= 2020 && asInt <= 2030
}
func hcl(in string) bool {
    // a # followed by exactly six characters 0-9 or a-f.
    allGood := false
    if strings.HasPrefix(in, "#") {
        in = strings.ReplaceAll(in, "#", "")
        if !(len(in) == 6) {
            return false
        }
        toRune := []rune(in)

        for r := 0; r < len(toRune); r++ {
            allGood = (unicode.IsDigit(toRune[r]) || unicode.IsLetter(toRune[r]))
        }
    }
    return allGood
}

func ecl(in string) bool {
    // exactly one of: amb blu brn gry grn hzl oth.
    correctVals := []string{
        "amb",
        "blu",
        "brn",
        "gry",
        "grn",
        "hzl",
        "oth",
    }

    for _, val := range correctVals {
        if val == in {
            return true
        }
    }
    return false
}

func pid(in string) bool {
    // a nine-digit number, including leading zeroes.
    if !(len(in) == 9) {
        return false
    }
    _, err := strconv.Atoi(in)
    return err == nil
}