Unity assets: Korea gacha drop-rate disclosure (2024 law)

using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

// Weighted drop table that prints every item's exact drop rate on the purchase / view screen.
// Rates are shown as percentages and rounded no coarser than four places below the first
// non-zero digit (Korea, Enforcement Decree of the Game Industry Promotion Act, Annex 3-2, 2.A.2).
public class DropRateTable : MonoBehaviour
{
    [Serializable]
    public class Entry
    {
        [Tooltip("Name the player sees, e.g. 'SSR Dragon Knight'.")]
        public string itemName = "Item";

        [Tooltip("Grade or rarity label, e.g. 'SSR'. Used by PityCounter. Leave empty to hide it.")]
        public string grade = "";

        [Tooltip("Relative weight. Drop rate = this weight / sum of all weights.")]
        [Min(0)] public float weight = 1f;
    }

    [Tooltip("Every item this box, banner or upgrade can give. Weight 0 is listed as 0% and never drops.")]
    public List<Entry> entries = new List<Entry>();

    [Tooltip("Significant digits kept when rounding. 4 is the coarsest rounding Annex 3-2 allows; raise it for more precision.")]
    [Min(4)] public int significantDigits = 4;

    [Tooltip("Text on the purchase or view screen that receives the full rate list.")]
    public Text disclosureText;

    [Tooltip("First line of the list, in the language of your store page.")]
    public string header = "Drop rates (probability item)";

    [Tooltip("Show the grade in brackets after each item name.")]
    public bool showGrade = true;

    [Tooltip("Hard cap on listed entries so a bad import cannot freeze the UI. Raise it if the box really holds more.")]
    [Min(1)] public int maxEntries = 500;

    // Last text written, readable by the exporter and by tests.
    public string LastDisclosure { get; private set; }

    bool warnedMissingText;

    void OnEnable()
    {
        Refresh();
    }

    void OnValidate()
    {
        if (significantDigits < 4) significantDigits = 4;
        if (disclosureText != null) Refresh();
    }

    // Sum of all usable weights. NaN, infinity and negatives count as 0 so one bad value
    // cannot turn every rate into NaN.
    public double TotalWeight()
    {
        double total = 0;
        int n = Mathf.Min(entries.Count, maxEntries);
        for (int i = 0; i < n; i++) total += SafeWeight(entries[i]);
        return total;
    }

    static double SafeWeight(Entry e)
    {
        if (e == null) return 0;
        double w = e.weight;
        if (double.IsNaN(w) || double.IsInfinity(w) || w < 0) return 0;
        return w;
    }

    // Exact rate of entry i in percent (0..100).
    public double RatePercent(int i)
    {
        double total = TotalWeight();
        if (total <= 0 || i < 0 || i >= entries.Count || i >= maxEntries) return 0;
        return SafeWeight(entries[i]) / total * 100.0;
    }

    // Combined rate of every entry with this grade, in percent.
    public double GradePercent(string grade)
    {
        double sum = 0;
        int n = Mathf.Min(entries.Count, maxEntries);
        for (int i = 0; i < n; i++)
            if (entries[i] != null && entries[i].grade == grade) sum += RatePercent(i);
        return sum;
    }

    // Percent string rounded at the decimal place `significantDigits` below the first
    // non-zero digit. 0.069979 -> "0.06998%", 4.4987 -> "4.499%", 50.01 -> "50.01%".
    public static string FormatPercent(double pct, int significantDigits)
    {
        if (double.IsNaN(pct) || pct <= 0) return "0%";
        if (significantDigits < 4) significantDigits = 4;
        int firstDigit = (int)Math.Floor(Math.Log10(pct));
        int decimals = Mathf.Clamp(significantDigits - 1 - firstDigit, 0, 15);
        return pct.ToString("F" + decimals, System.Globalization.CultureInfo.InvariantCulture) + "%";
    }

    public string FormatRate(int i)
    {
        return FormatPercent(RatePercent(i), significantDigits);
    }

    public string BuildDisclosure()
    {
        var sb = new System.Text.StringBuilder();
        if (!string.IsNullOrEmpty(header)) sb.AppendLine(header);
        int n = Mathf.Min(entries.Count, maxEntries);
        for (int i = 0; i < n; i++)
        {
            Entry e = entries[i];
            if (e == null) continue;
            sb.Append(e.itemName);
            if (showGrade && !string.IsNullOrEmpty(e.grade)) sb.Append(" [").Append(e.grade).Append("]");
            sb.Append("  ").AppendLine(FormatRate(i));
        }
        if (entries.Count > maxEntries)
            sb.AppendLine("(" + (entries.Count - maxEntries) + " entries over maxEntries are not listed and never drop)");
        return sb.ToString();
    }

    // Rewrites the on-screen list. Call it after you change weights at runtime.
    public void Refresh()
    {
        LastDisclosure = BuildDisclosure();
        if (disclosureText == null)
        {
            if (!warnedMissingText && Application.isPlaying)
            {
                Debug.LogWarning(name + ": DropRateTable has no disclosureText, so the rates are not on screen.", this);
                warnedMissingText = true;
            }
            return;
        }
        disclosureText.text = LastDisclosure;
    }

    // Picks an index by weight, or -1 if nothing can drop.
    public int Roll()
    {
        return RollWhere(null);
    }

    // Picks an index by weight among entries of one grade (used for a guarantee), or -1.
    public int RollGrade(string grade)
    {
        return RollWhere(grade);
    }

    int RollWhere(string grade)
    {
        int n = Mathf.Min(entries.Count, maxEntries);
        double total = 0;
        int lastUsable = -1;
        for (int i = 0; i < n; i++)
        {
            if (entries[i] == null || (grade != null && entries[i].grade != grade)) continue;
            double w = SafeWeight(entries[i]);
            if (w <= 0) continue;
            total += w;
            lastUsable = i;
        }
        if (lastUsable < 0) return -1;
        // Random.value can return exactly 1.0; without the fallback below that roll would
        // fall off the end of the list.
        double r = UnityEngine.Random.value * total;
        double acc = 0;
        for (int i = 0; i < n; i++)
        {
            if (entries[i] == null || (grade != null && entries[i].grade != grade)) continue;
            double w = SafeWeight(entries[i]);
            if (w <= 0) continue;
            acc += w;
            if (r < acc) return i;
        }
        return lastUsable;
    }
}