naps2/NAPS2.Sdk/ImportExport/Placeholders.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace NAPS2.ImportExport
{
    public abstract class Placeholders
    {
        public const string YEAR_4_DIGITS = "$(YYYY)";
        public const string YEAR_2_DIGITS = "$(YY)";
        public const string MONTH_2_DIGITS = "$(MM)";
        public const string DAY_2_DIGITS = "$(DD)";
        public const string HOUR_24_CLOCK = "$(hh)";
        public const string MINUTE_2_DIGITS = "$(mm)";
        public const string SECOND_2_DIGITS = "$(ss)";
        public const string NUMBER_4_DIGITS = "$(nnnn)";
        public const string NUMBER_3_DIGITS = "$(nnn)";
        public const string NUMBER_2_DIGITS = "$(nn)";
        public const string NUMBER_1_DIGIT = "$(n)";

        public static DefaultPlaceholders All => new DefaultPlaceholders();

        public static EnvironmentPlaceholders Env => new EnvironmentPlaceholders();

        public static StubPlaceholders None => new StubPlaceholders();

        public abstract string Substitute(string filePath, bool incrementIfExists = true, int numberSkip = 0, int autoNumberDigits = 0);

        public class StubPlaceholders : Placeholders
        {
            public override string Substitute(string filePath, bool incrementIfExists = true, int numberSkip = 0, int autoNumberDigits = 0) => filePath;
        }

        public class EnvironmentPlaceholders : Placeholders
        {
            public override string Substitute(string filePath, bool incrementIfExists = true, int numberSkip = 0, int autoNumberDigits = 0) => Environment.ExpandEnvironmentVariables(filePath);
        }

        public class DefaultPlaceholders : Placeholders
        {
            private static readonly Dictionary<string, Func<DateTime, string>> Replacements = new Dictionary<string, Func<DateTime, string>>
            {
                {YEAR_4_DIGITS, dateTime => dateTime.ToString("yyyy")},
                {YEAR_2_DIGITS, dateTime => dateTime.ToString("yy")},
                {MONTH_2_DIGITS, dateTime => dateTime.ToString("MM")},
                {DAY_2_DIGITS, dateTime => dateTime.ToString("dd")},
                {HOUR_24_CLOCK, dateTime => dateTime.ToString("HH")},
                {MINUTE_2_DIGITS, dateTime => dateTime.ToString("mm")},
                {SECOND_2_DIGITS, dateTime => dateTime.ToString("ss")},
            };

            private static readonly Regex NumberPlaceholderPattern = new Regex(@"\$\(n+\)");

            private readonly DateTime? dateTimeOverride;
            
            public DefaultPlaceholders(DateTime? dateTimeOverride = null)
            {
                this.dateTimeOverride = dateTimeOverride;
            }

            public DefaultPlaceholders WithDate(DateTime dateTime) => new DefaultPlaceholders(dateTime);

            public override string Substitute(string filePath, bool incrementIfExists = true, int numberSkip = 0, int autoNumberDigits = 0)
            {
                if (filePath == null)
                {
                    return null;
                }

                var dateTime = dateTimeOverride ?? DateTime.Now;
                // Start with environment variables
                string result = Environment.ExpandEnvironmentVariables(filePath);
                // Most placeholders don't need a special case
                result = Replacements.Aggregate(result, (current, ph) => current.Replace(ph.Key, ph.Value(dateTime)));
                // One does, however
                var match = NumberPlaceholderPattern.Match(result);
                if (match.Success)
                {
                    result = NumberPlaceholderPattern.Replace(result, "");
                    result = SubstituteNumber(result, match.Index, match.Length - 3, numberSkip, true);
                }
                else if (autoNumberDigits > 0)
                {
                    result = result.Insert(result.Length - Path.GetExtension(result).Length, ".");
                    result = SubstituteNumber(result, result.Length - Path.GetExtension(result).Length, autoNumberDigits, numberSkip, incrementIfExists);
                }

                return result;
            }

            private string SubstituteNumber(string path, int insertionIndex, int minDigits, int skip, bool incrementIfExists)
            {
                string result;
                int i = skip;
                do
                {
                    ++i;
                    result = path.Insert(insertionIndex, i.ToString("D" + minDigits));
                } while (incrementIfExists && File.Exists(result));

                return result;
            }
        }
    }
}