ServiceNow attachment retrieval

ServiceNowAttachmentRetrievalTests.cs

using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Text;

namespace UnitTests
{
    [TestClass]
    public class ServiceNowAttachmentRetrievalTests
    {
        private static readonly string Chunk0AsBase64 = "H4sIAAAAAAAAAA=="; // Length = 16, position = 0

        // Length = 1,416, position = 1
        private static readonly string Chunk1AsBase64 =
            "7VVBcuQ2DPwKHjDxA5LDVu3Nl+SSD1AUZsi1RGoJcsba16cBSh77kHOqUrzYGhIAgUYD/b1VeqW1SSV+3xYXE9V" +
            "Me24U8oPcslANUWiNUt0bJ4ozO8pXmjnllnxMN9oWdtIKk0szbcVFsVMN9XBCUy7Jrl7pERHvFu9sDzjyeYVzha" +
            "f3iFY1cA1Mskvl9WJeyApXs507X5tDRux8wBty2t8Ku55/LlzO01paDRf7XB0Clt+mFpe5G4S2ukTBbVtMLPJCf" +
            "2bKianwD/ZVLjRHWeIb4ysXcvccZ3lWGqvwcr3QxN410d8Un9c4B6rnXQ0Zfx8h05wp5UpvCcgqugB6a0UaPwMX" +
            "V2NOgH0nToYJ0vU5Cf9sOGBBOJTqYMrvtfDKsFSor23RGpDqTYGPasjWk13L0ueXfIc/TPqj9jmzxKJRUf1U1dP" +
            "6BoD+pUTcfi0ve+/kzNnH4tsKqliquGqFlAYh+oA34tI5ok94wL+V7LXqEFeSvJ6NPNF4ob8zKe1AlVriPaL3/O" +
            "6UM5cjJhJtQnwHSiAJF7UWWhxIFzNutrBL9ObHxUeBI7973uqniu1lN99dqu7GdC15RbXf6DuqVNwCSAwYqcRbM" +
            "L9rRBFX1xbcxxqQnXJJTX3IaLbByelH3nH10VprnMZKGeFS3nVKPrfWmHY262Cc62CZL9Cam+KKAOgZnkfGH/G/" +
            "0V/JuJ618XgozQCJz0HlnqrVwIoMaoi3ZHSzphx8p5V7KUoxyWjzDUPDc7fhNRe3xF/4Pe32mg+urDaIH4Ue47c" +
            "C1lQvFmTBa92nE+7SK4LZrkTQqbhidIXZXK1mfbCW3KaFn6Sf+i5QeEHhP/qG+KlLYVoc2jjxknUxwOI5d1cH4h" +
            "mKHEH5VjV1RL4FAOTedP41ad1OJ6/6/JBoTLRMnHXr9JJQYnrTEyPLF2KDtAGFoCwlgua8cblip2A8JCp3e9JOd" +
            "s0SsFcEalHCC72iaoQECiG3ormgGfiiLT/62gLBInqJ9LAailsx/2dzzBhIBtu+BTORqpj3xHrkDEjbQg+FE9yw" +
            "hk8s6JKO0P5pwRmEE/DjBVv6eOIwsu4oP3l+sSnRcdbZ0/9fNoA65YdBlztdoDCdLtYGEN4oC4LcjIp2NTWxpaw" +
            "7xyQDkOiMKIR9p/R5OJIVkP3OR76FtzZHV4+MbdCOXLzOvaaMBiGusI2trUklH8Tu4XYEy8ssB13MpmIHH4zSDY" +
            "jW+6htRKZYkegs8v6dwod2fEoMTsK24vpU2n7D/w8Lm3le8A78Oc3mpQCbr4FMj1ykz4R0uIdeD70eej30euj10" +
            "Ouh10Ovh14PvR56PfR66PXQ66HXQ6+HXg+9Hno99Hro9dDroddDr4deD70eej30euj10Ov/WK+HXA+5HnI95HrI" +
            "9ZDr/5dc/wODfyWHSS0AAA==";


        /// <summary>
        /// The list of chunks. In practice, there are many more chunks when attachments are sized
        /// in Mebibytes.
        /// 
        /// Note that the order is important.
        /// </summary>
        private static readonly IList<string> Base64ChunksOrdered = new List<string>
        {
            Chunk0AsBase64,
            Chunk1AsBase64
        }.AsReadOnly();

        /// <summary>
        /// This method does everything.
        /// </summary>
        [TestMethod]
        public void RunServiceNowAttachmentRetrieval()
        {
            Assert.AreEqual(16, Chunk0AsBase64.Length);
            Assert.AreEqual(1416, Chunk1AsBase64.Length);

            var chunk0AsBinary = Convert.FromBase64String(Chunk0AsBase64);
            var chunk1AsBinary = Convert.FromBase64String(Chunk1AsBase64);

            var gzippedData = new byte[chunk0AsBinary.Length + chunk1AsBinary.Length];

            Array.Copy(chunk0AsBinary, 0, gzippedData, 0, chunk0AsBinary.Length);
            Array.Copy(chunk1AsBinary, 0, gzippedData, chunk0AsBinary.Length, chunk1AsBinary.Length);

            //const int blockSize = 4096;
            var buffer = new byte[4096];

            using (var inputStream = new GZipStream(new MemoryStream(gzippedData), CompressionMode.Decompress))
            using (var outputStream = new MemoryStream())
            {
                var bytesRead = 0;
                while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
                {
                    outputStream.Write(buffer, 0, bytesRead);
                }

                var uncompressedData = outputStream.ToArray();
                var outputText = Encoding.UTF8.GetString(uncompressedData);

                Assert.AreEqual(CiceroText, outputText);
            }
        }

        /// <summary>
        /// And this method makes use of refactored code.
        /// </summary>
        [TestMethod]
        public void ServiceNow2()
        {
            var gzippedData = ConvertBase64ChunksToGzippedData(Base64ChunksOrdered);
            var decompressedData = DecompressGzippedData(gzippedData);

            var outputText = Encoding.UTF8.GetString(decompressedData);

            Assert.AreEqual(CiceroText, outputText);
        }

        private byte[] DecompressGzippedData(byte[] gzippedData)
        {
            var buffer = new byte[4096];

            using (var inputStream = new GZipStream(new MemoryStream(gzippedData), CompressionMode.Decompress))
            using (var decompressedData = new MemoryStream())
            {
                var bytesRead = 0;
                while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
                {
                    decompressedData.Write(buffer, 0, bytesRead);
                }

                return decompressedData.ToArray();
            }
        }

        private byte[] ConvertBase64ChunksToGzippedData(IList<string> attachmentBase64Chunks)
        {
            using (var ms = new MemoryStream())
            {
                foreach (var chunk in attachmentBase64Chunks)
                {
                    var chunkBinary = Convert.FromBase64String(chunk);

                    ms.Write(chunkBinary, 0, chunkBinary.Length);
                }

                return ms.ToArray();
            }
        }


        #region Test string

        /// <summary>
        /// Our testing string. Sufficiently large that ServiceNow used two chunks to store it
        /// as an attachment.
        /// </summary>
        private readonly string CiceroText =
            "But I must explain to you how all this mistaken idea of deno" +
        "uncing pleasure and praising pain was born and I will give y" +
        "ou a complete account of the system, and expound the actual " +
        "teachings of the great explorer of the truth, the master-bui" +
        "lder of human happiness. No one rejects, dislikes, or avoids" +
        " pleasure itself, because it is pleasure, but because those " +
        "who do not know how to pursue pleasure rationally encounter " +
        "consequences that are extremely painful. Nor again is there " +
        "anyone who loves or pursues or desires to obtain pain of its" +
        "elf, because it is pain, but because occasionally circumstan" +
        "ces occur in which toil and pain can procure him some great " +
        "pleasure. To take a trivial example, which of us ever undert" +
        "akes laborious physical exercise, except to obtain some adva" +
        "ntage from it? But who has any right to find fault with a ma" +
        "n who chooses to enjoy a pleasure that has no annoying conse" +
        "quences, or one who avoids a pain that produces no resultant" +
        " pleasure? On the other hand, we denounce with righteous ind" +
        "ignation and dislike men who are so beguiled and demoralized" +
        " by the charms of pleasure of the moment, so blinded by desi" +
        "re, that they cannot foresee the pain and trouble that are b" +
        "ound to ensue; and equal blame belongs to those who fail in " +
        "their duty through weakness of will, which is the same as sa" +
        "ying through shrinking from toil and pain. These cases are p" +
        "erfectly simple and easy to distinguish. In a free hour, whe" +
        "n our power of choice is untrammelled and when nothing preve" +
        "nts our being able to do what we like best, every pleasure i" +
        "s to be welcomed and every pain avoided. But in certain circ" +
        "umstances and owing to the claims of duty or the obligations" +
        " of business it will frequently occur that pleasures have to" +
        " be repudiated and annoyances accepted. The wise man therefo" +
        "re always holds in these matters to this principle of select" +
        "ion: he rejects pleasures to secure other greater pleasures," +
        " or else he endures pains to avoid worse pains. But I must e" +
        "xplain to you how all this mistaken idea of denouncing pleas" +
        "ure and praising pain was born and I will give you a complet" +
        "e account of the system, and expound the actual teachings of" +
        " the great explorer of the truth, the master-builder of huma" +
        "n happiness. No one rejects, dislikes, or avoids pleasure it" +
        "self, because it is pleasure, but because those who do not k" +
        "now how to pursue pleasure rationally encounter consequences" +
        " that are extremely painful. Nor again is there anyone who l" +
        "oves or pursues or desires to obtain pain of itself, because" +
        " it is pain, but because occasionally circumstances occur in" +
        " which toil and pain can procure him some great pleasure. To" +
        " take a trivial example, which of us ever undertakes laborio" +
        "us physical exercise, except to obtain some advantage from i" +
        "t? But who has any right to find fault with a man who choose" +
        "s to enjoy a pleasure that has no annoying consequences, or " +
        "one who avoids a pain that produces no resultant pleasure? O" +
        "n the other hand, we denounce with righteous indignation and" +
        " dislike men who are so beguiled and demoralized by the char" +
        "ms of pleasure of the moment, so blinded by desire, that the" +
        "y cannot foresee the pain and trouble that are bound to ensu" +
        "e; and equal blame belongs to those who fail in their duty t" +
        "hrough weakness of will, which is the same as saying through" +
        " shrinking from toil and pain. These cases are perfectly sim" +
        "ple and easy to distinguish. In a free hour, when our power " +
        "of choice is untrammelled and when nothing prevents our bein" +
        "g able to do what we like best, every pleasure is to be welc" +
        "omed and every pain avoided. But in certain circumstances an" +
        "d owing to the claims of duty or the obligations of business" +
        " it will frequently occur that pleasures have to be repudiat" +
        "ed and annoyances accepted. The wise man therefore always ho" +
        "lds in these matters to this principle of selection: he reje" +
        "cts pleasures to secure other greater pleasures, or else he " +
        "endures pains to avoid worse pains. But I must explain to yo" +
        "u how all this mistaken idea of denouncing pleasure and prai" +
        "sing pain was born and I will give you a complete account of" +
        " the system, and expound the actual teachings of the great e" +
        "xplorer of the truth, the master-builder of human happiness." +
        " No one rejects, dislikes, or avoids pleasure itself, becaus" +
        "e it is pleasure, but because those who do not know how to p" +
        "ursue pleasure rationally encounter consequences that are ex" +
        "tremely painful. Nor again is there anyone who loves or purs" +
        "ues or desires to obtain pain of itself, because it is pain," +
        " but because occasionally circumstances occur in which toil " +
        "and pain can procure him some great pleasure. To take a triv" +
        "ial example, which of us ever undertakes laborious physical " +
        "exercise, except to obtain some advantage from it? But who h" +
        "as any right to find fault with a man who chooses to enjoy a" +
        " pleasure that has no annoying consequences, or one who avoi" +
        "ds a pain that produces no resultant pleasure? On the other " +
        "hand, we denounce with righteous indignation and dislike men" +
        " who are so beguiled and demoralized by the charms of pleasu" +
        "re of the moment, so blinded by desire, that they cannot for" +
        "esee the pain and trouble that are bound to ensue; and equal" +
        " blame belongs to those who fail in their duty through weakn" +
        "ess of will, which is the same as saying through shrinking f" +
        "rom toil and pain. These cases are perfectly simple and easy" +
        " to distinguish. In a free hour, when our power of choice is" +
        " untrammelled and when nothing prevents our being able to do" +
        " what we like best, every pleasure is to be welcomed and eve" +
        "ry pain avoided. But in certain circumstances and owing to t" +
        "he claims of duty or the obligations of business it will fre" +
        "quently occur that pleasures have to be repudiated and annoy" +
        "ances accepted. The wise man therefore always holds in these" +
        " matters to this principle of selection: he rejects pleasure" +
        "s to secure other greater pleasures, or else he endures pain" +
        "s to avoid worse pains. But I must explain to you how all th" +
        "is mistaken idea of denouncing pleasure and praising pain wa" +
        "s born and I will give you a complete account of the system," +
        " and expound the actual teachings of the great explorer of t" +
        "he truth, the master-builder of human happiness. No one reje" +
        "cts, dislikes, or avoids pleasure itself, because it is plea" +
        "sure, but because those who do not know how to pursue pleasu" +
        "re rationally encounter consequences that are extremely pain" +
        "ful. Nor again is there anyone who loves or pursues or desir" +
        "es to obtain pain of itself, because it is pain, but because" +
        " occasionally circumstances occur in which toil and pain can" +
        " procure him some great pleasure. To take a trivial example," +
        " which of us ever undertakes laborious physical exercise, ex" +
        "cept to obtain some advantage from it? But who has any right" +
        " to find fault with a man who chooses to enjoy a pleasure th" +
        "at has no annoying consequences, or one who avoids a pain th" +
        "at produces no resultant pleasure? On the other hand, we den" +
        "ounce with righteous indignation and dislike men who are so " +
        "beguiled and demoralized by the charms of pleasure of the mo" +
        "ment, so blinded by desire, that they cannot foresee the pai" +
        "n and trouble that are bound to ensue; and equal blame belon" +
        "gs to those who fail in their duty through weakness of will," +
        " which is the same as saying through shrinking from toil and" +
        " pain. These cases are perfectly simple and easy to distingu" +
        "ish. In a free hour, when our power of choice is untrammelle" +
        "d and when nothing prevents our being able to do what we lik" +
        "e best, every pleasure is to be welcomed and every pain avoi" +
        "ded. But in certain circumstances and owing to the claims of" +
        " duty or the obligations of business it will frequently occu" +
        "r that pleasures have to be repudiated and annoyances accept" +
        "ed. The wise man therefore always holds in these matters to " +
        "this principle of selection: he rejects pleasures to secure " +
        "other greater pleasures, or else he endures pains to avoid w" +
        "orse pains. But I must explain to you how all this mistaken " +
        "idea of denouncing pleasure and praising pain was born and I" +
        " will give you a complete account of the system, and expound" +
        " the actual teachings of the great explorer of the truth, th" +
        "e master-builder of human happiness. No one rejects, dislike" +
        "s, or avoids pleasure itself, because it is pleasure, but be" +
        "cause those who do not know how to pursue pleasure rationall" +
        "y encounter consequences that are extremely painful. Nor aga" +
        "in is there anyone who loves or pursues or desires to obtain" +
        " pain of itself, because it is pain, but because occasionall" +
        "y circumstances occur in which toil and pain can procure him" +
        " some great pleasure. To take a trivial example, which of us" +
        " ever undertakes laborious physical exercise, except to obta" +
        "in some advantage from it? But who has any right to find fau" +
        "lt with a man who chooses to enjoy a pleasure that has no an" +
        "noying consequences, or one who avoids a pain that produces " +
        "no resultant pleasure? On the other hand, we denounce with r" +
        "ighteous indignation and dislike men who are so beguiled and" +
        " demoralized by the charms of pleasure of the moment, so bli" +
        "nded by desire, that they cannot foresee the pain and troubl" +
        "e that are bound to ensue; and equal blame belongs to those " +
        "who fail in their duty through weakness of will, which is th" +
        "e same as saying through shrinking from toil and pain. These" +
        " cases are perfectly simple and easy to distinguish. In a fr" +
        "ee hour, when our power of choice is untrammelled and when n" +
        "othing prevents our being able to do what we like best, ever" +
        "y pleasure is to be welcomed and every pain avoided. But in " +
        "certain circumstances and owing to the claims of duty or the" +
        " obligations of business it will frequently occur that pleas" +
        "ures have to be repudiated and annoyances accepted. The wise" +
        " man therefore always holds in these matters to this princip" +
        "le of selection: he rejects pleasures to secure other greate" +
        "r pleasures, or else he endures pains to avoid worse pains.B" +
        "ut I must explain to you how all this mistaken idea of denou" +
        "ncing pleasure and praising pain was born and I will give yo" +
        "u a complete account of the system, and expound the actual t" +
        "eachings of the great explorer of the truth, the master-buil" +
        "der of human happiness. No one rejects, dislikes, or avoids " +
        "pleasure itself, because it is pleasure, but because those w" +
        "ho do not know how to pursue pleasure rationally encounter c" +
        "onsequences that are extremely painful. Nor again is there a" +
        "nyone who loves or pursues or desires to obtain pain of itse" +
        "lf, because it is pain, but because occasionally circumstanc" +
        "es occur in which toil and pain can procure him some great p" +
        "leasure. To take a trivial example, which of us ever underta" +
        "kes laborious physical exercise, except to obtain some advan" +
        "tage from it? But who has any right to find fault with a man" +
        " who chooses to enjoy a pleasure that has no annoying conseq" +
        "uences, or one who avoids a pain that produces no resultant " +
        "pleasure? On the other hand, we denounce with righteous indi" +
        "gnation and dislike men who are so beguiled and demoralized " +
        "by the charms of pleasure of the moment, so blinded by desir" +
        "e, that they cannot foresee the pain and trouble that are bo" +
        "und to ensue; and equal blame belongs to those who fail in t" +
        "heir duty through weakness of will, which is the same as say" +
        "ing through shrinking from toil and pain. These cases are pe" +
        "rfectly simple and easy to distinguish. In a free hour, when" +
        " our power of choice is untrammelled and when nothing preven" +
        "ts our being able to do what we like best, every pleasure is" +
        " to be welcomed and every pain avoided. But in certain circu" +
        "mstances and owing to the claims of duty or the obligations " +
        "of business it will frequently occur that pleasures have to " +
        "be repudiated";

        #endregion
    }
}