package main

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

const (
	seedToSoilMap            = "seed-to-soil map"
	soilToFertilizerMap      = "soil-to-fertilizer map"
	fertilizerToWaterMap     = "fertilizer-to-water map"
	waterToLightMap          = "water-to-light map"
	lightToTemperatureMap    = "light-to-temperature map"
	temperatureToHumidityMap = "temperature-to-humidity map"
	humidityToLocationMap    = "humidity-to-location map"
)

type almanac struct {
	seeds                 []int
	seedToSoil            map[int]int
	soilToFertilizer      map[int]int
	fertilizerToWater     map[int]int
	waterToLight          map[int]int
	lightToTemperature    map[int]int
	temperatureToHumidity map[int]int
	humidityToLocation    map[int]int
}

func parseAlmanac(contents []string) (almanac, error) {
	// Assumption: The first line always contains the seed numbers. An error is returned
	// if this is not the case or if the format is all wrong.
	seeds, err := parseSeedNums(contents[0])
	if err != nil {
		return almanac{}, fmt.Errorf("unable to parse the seed numbers; %w", err)
	}

	// mapLines = []string{}
	// loop while contents > 0
	//	if line is blank
	//	  if map lines > 0 -> parse map and populate relevant field
	//	  mapLines = []string{}
	//	else
	//	  if first rune is digit, add line to mapLines:
	//	  else get map name

	output := almanac{
		seeds: seeds,
	}

	return output, nil
}

func parseSeedNums(seedStr string) ([]int, error) {
	expectedPrefix := "seeds:"

	if !strings.HasPrefix(seedStr, expectedPrefix) {
		return nil, fmt.Errorf("%q does not begin with %s", seedStr, expectedPrefix)
	}

	seedStr = seedStr[strings.Index(seedStr, ":")+1:]

	seeds := []int{}
	seedNum := ""

	addSeed := func(digit string) error {
		value, err := strconv.Atoi(digit)
		if err != nil {
			return fmt.Errorf("unable to convert %q to int; %w", digit, err)
		}
		seeds = append(seeds, value)
		return nil
	}

	for ind, s := range seedStr {
		if unicode.IsDigit(s) {
			seedNum = seedNum + string(s)
			if ind == len(seedStr)-1 {
				if err := addSeed(seedNum); err != nil {
					return nil, fmt.Errorf("unable to add %q to seeds; %w", seedNum, err)
				}
			}
		} else {
			if len(seedNum) > 0 {
				if err := addSeed(seedNum); err != nil {
					return nil, fmt.Errorf("unable to add %q to seeds; %w", seedNum, err)
				}
			}

			seedNum = ""
		}
	}

	return seeds, nil
}

func parseMap(mapLines []string) (map[int]int, error) {
	var mapMatrix [][]int

	return nil, nil
}