package day5

import (
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

type Almanach struct {
	SeedToSoil,
	SoilToFert,
	FertToWater,
	WaterToLight,
	LightToTemp,
	TempToHum,
	HumToLocation map[int]int
}

func applyMap(source int, mapping map[int]int) int {
	var result int
	result, found := mapping[source]
	if !found {
		result = source
	}
	return result
}

func (a Almanach)locationForSeed(seed int) int {
	soil := applyMap(seed, a.SeedToSoil)
	fert := applyMap(soil, a.SoilToFert)
	water := applyMap(fert, a.FertToWater)
	light := applyMap(water, a.WaterToLight)
	temp := applyMap(light, a.LightToTemp)
	hum := applyMap(temp, a.TempToHum)
	location := applyMap(hum, a.HumToLocation)
	return location
}

func Run() int {
	fmt.Println("the day 5")
	inputDir := "day5/example"
	seedToSoil := fmt.Sprint(inputDir, "/seed-to-soil")
	soilToFert := fmt.Sprint(inputDir, "/soil-to-fertilizer")
	fertToWater := fmt.Sprint(inputDir, "/fertilizer-to-water")
	waterToLight := fmt.Sprint(inputDir, "/water-to-light")
	lightToTemp := fmt.Sprint(inputDir, "/light-to-temperature")
	tempToHum := fmt.Sprint(inputDir, "/temperature-to-humidity")
	humToLocation := fmt.Sprint(inputDir, "/humidity-to-location")

	seedsFileName := fmt.Sprint(inputDir, "/seeds")
	seedsBytes, err := os.ReadFile(seedsFileName)
	if err != nil {
		panic(fmt.Sprint("error reading seeds file ", seedsFileName))
	}
	seedsLine := string(seedsBytes)
	var seeds []int
	for _, seedStr := range strings.Fields(seedsLine) {
		seed, err := strconv.Atoi(seedStr)
		if err != nil {
			panic(fmt.Sprint("can't read seeds ", seedStr))
		}
		seeds = append(seeds, seed)
	}

	almanach := Almanach{
		SeedToSoil: ReadMap(seedToSoil),
		SoilToFert: ReadMap(soilToFert),
		FertToWater: ReadMap(fertToWater),
		WaterToLight: ReadMap(waterToLight),
		LightToTemp: ReadMap(lightToTemp),
		TempToHum: ReadMap(tempToHum),
		HumToLocation: ReadMap(humToLocation),
	}

	result := math.MaxInt
	for _, seed := range seeds {
		location := almanach.locationForSeed(seed)
		if location < result {
			result = location
		}
	}

	return result
}

func ReadMap(filename string) map[int]int {
	result := make(map[int]int)
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(fmt.Sprintf("error reading file %s", filename))
	}
	text := string(bytes)
	text = strings.TrimSpace(text)
	for _, line := range strings.Split(text, "\n") {
		nums := strings.Fields(line)
		if len(nums) != 3 {
			panic(fmt.Sprint("error, map line doesn't have 3 nums: ", line, nums))
		}
		destinaitonStart, err1 := strconv.Atoi(nums[0])
		sourceStart, err2 := strconv.Atoi(nums[1])
		rangeLength, err3 := strconv.Atoi(nums[2])
		if err1 != nil || err2 != nil || err3 != nil {
			panic(fmt.Sprint("error converting one of the numbers: ", nums))
		}
		for i := 0; i < rangeLength; i++ {
			result[sourceStart+i] = destinaitonStart + i
		}
	}

	return result
}