51 lines
1.9 KiB
C#
51 lines
1.9 KiB
C#
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namespace MultiversalDiplomacy.Model;
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/// <summary>
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/// A shared counter for handing out new timeline designations.
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/// </summary>
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internal class TimelineFactory
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{
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private static readonly char[] Letters = [
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'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
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'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
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'u', 'v', 'w', 'x', 'y', 'z',
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];
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/// <summary>
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/// Convert a string timeline identifier to its serial number.
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/// </summary>
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/// <param name="timeline">Timeline identifier.</param>
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/// <returns>Integer.</returns>
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public static int StringToInt(string timeline)
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{
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int result = Array.IndexOf(Letters, timeline[0]);
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for (int i = 1; i < timeline.Length; i++) {
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// The result is incremented by one because timeline designations are not a true base26 system.
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// The "ones digit" maps a-z 0-25, but the "tens digit" maps a to 1, so "10" (26) is "aa" and not "a0"
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result = (result + 1) * 26;
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result += Array.IndexOf(Letters, timeline[i]);
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}
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return result;
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}
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/// <summary>
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/// Convert a timeline serial number to its string identifier.
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/// </summary>
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/// <param name="designation">Integer.</param>
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/// <returns>Timeline identifier.</returns>
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public static string IntToString(int designation) {
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static int downshift(int i ) => (i - (i % 26)) / 26;
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IEnumerable<char> result = [Letters[designation % 26]];
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for (int remainder = downshift(designation); remainder > 0; remainder = downshift(remainder) - 1) {
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// We subtract 1 after downshifting for the same reason we add 1 above after upshifting.
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//
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result = result.Prepend(Letters[(remainder % 26 + 25) % 26]);
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}
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return new string(result.ToArray());
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}
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private int nextTimeline = 0;
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public string NextTimeline() => IntToString(nextTimeline++);
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}
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