package year25

import (
	"bufio"
	"cmp"
	"fmt"
	"iter"
	"slices"
	"strconv"
	"strings"

	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aoc"
)

type Day5Interval struct {
	Start, End int64
	isRemoved  bool
}

type MergedIntervals struct {
	intervals []*Day5Interval
}

func (m *MergedIntervals) Put1(newInterval Day5Interval) {
	for item := range m.Items() {
		if newInterval.Start <= item.End && newInterval.End >= item.Start {
			newInterval.Start = min(newInterval.Start, item.Start)
			newInterval.End = max(newInterval.End, item.End)

			item.isRemoved = true
			m.Put(newInterval)
			return
		}
	}

	// just in case there are too many intervals
	m.intervals = slices.DeleteFunc(m.intervals, func(i *Day5Interval) bool {
		return i.isRemoved
	})

	m.intervals = append(m.intervals, &newInterval)
}
func (m *MergedIntervals) Put(newInterval Day5Interval) {
	// fast search start, end
	for item := range m.Items() {
		if newInterval.Start <= item.End && newInterval.End >= item.Start {
			newInterval.Start = min(newInterval.Start, item.Start)
			newInterval.End = max(newInterval.End, item.End)

			item.isRemoved = true
			m.Put(newInterval)
			return
		}
	}

	m.intervals = slices.DeleteFunc(m.intervals, func(i *Day5Interval) bool {
		return i.isRemoved
	})

	i, _ := slices.BinarySearchFunc(m.intervals, &newInterval, func(interval *Day5Interval, d *Day5Interval) int {
		return cmp.Compare(interval.Start, newInterval.Start)
	})
	m.intervals = slices.Insert(m.intervals, i, &newInterval)
}

func (m *MergedIntervals) CheckItem(itemId int64) (*Day5Interval, bool) {
	for interval := range m.Items() {
		if interval.Start <= itemId && itemId <= interval.End {
			return interval, true
		}
	}
	return nil, false
}

func (m *MergedIntervals) Items() iter.Seq[*Day5Interval] {
	return func(yield func(*Day5Interval) bool) {
		for _, interval := range m.intervals {
			if !interval.isRemoved {
				if !yield(interval) {
					return
				}
			}
		}
	}
}

func Day5ParseIntervals(s *bufio.Scanner) (intervals *MergedIntervals, err error) {
	intervals = new(MergedIntervals)
	for s.Scan() {
		line := strings.TrimSpace(s.Text())
		if line == "" {
			return
		}

		var newInterval Day5Interval
		dashIndex := strings.Index(line, "-")
		newInterval.Start, err = strconv.ParseInt(line[:dashIndex], 10, 64)
		if err != nil {
			return intervals, fmt.Errorf("day5: failed to parse line %s. invalid start index: %w", line, err)
		}
		newInterval.End, err = strconv.ParseInt(line[dashIndex+1:], 10, 64)
		if err != nil {
			return intervals, fmt.Errorf("day5: failed to parse line %s. invalid end index: %w", line, err)
		}

		intervals.Put(newInterval)
	}

	return intervals, s.Err()
}

func Day5Part1(ctx aoc.Context) (int, error) {
	scanner := ctx.Scanner()
	intervals, err := Day5ParseIntervals(scanner)
	if err != nil {
		return 0, fmt.Errorf("day5: failed to parse intervals %w", err)
	}

	var freshIngredients int
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		itemId, err := strconv.ParseInt(line, 10, 64)
		if err != nil {
			return 0, fmt.Errorf("day5: failed to parse itemId in line %s. %w", line, err)
		}
		if interval, ok := intervals.CheckItem(itemId); ok {
			freshIngredients += 1
			ctx.Println(itemId, "is fresh because it was found in", interval)
		} else {
			ctx.Println(itemId, "is spoiled")
		}
	}
	return freshIngredients, scanner.Err()
}

func Day5Part2(ctx aoc.Context) (solution int64, _ error) {
	intervals, err := Day5ParseIntervals(ctx.Scanner())
	if err != nil {
		return 0, fmt.Errorf("day5: failed to parse intervals %w", err)
	}

	for interval := range intervals.Items() {
		solution += interval.End - interval.Start + 1
	}

	return solution, nil
}