using Glass.Editing;
using UnitTestSharp;

namespace Glass.UnitTests.Editing
{
    public class TextChangeTests : TestFixture
    {
        public static string Describe(TextChange change)
        {
            return $"({change.Start},{change.RemovedLength},{change.InsertedLength})";
        }

        public static string Apply(string text, TextChange change, string inserted)
        {
            return text.Substring(0, change.Start) + inserted
                + text.Substring(change.Start + change.RemovedLength);
        }

        public class CtorTests : TestFixture
        {
            public void StoresTheStartAndBothLengths()
            {
                var change = new TextChange(start: 3, removedLength: 4, insertedLength: 5);

                CheckEqual(3, change.Start);
                CheckEqual(4, change.RemovedLength);
                CheckEqual(5, change.InsertedLength);
            }
        }

        public class ThenTests : TestFixture
        {
            public void AdjacentInserts_JoinIntoOne()
            {
                CheckEqual("(0,0,2)", Describe(new TextChange(0, 0, 1).Then(new TextChange(1, 0, 1))));
            }

            public void AnEditInsideTheFirstInsert_ShrinksIt()
            {
                CheckEqual("(5,0,2)", Describe(new TextChange(5, 0, 3).Then(new TextChange(6, 1, 0))));
            }

            public void AnEditBeforeTheFirst_CoversTheTextBetween()
            {
                CheckEqual("(4,8,9)", Describe(new TextChange(10, 2, 3).Then(new TextChange(4, 1, 1))));
            }

            public void AnEditAfterTheFirst_CoversTheTextBetween()
            {
                CheckEqual("(0,9,11)", Describe(new TextChange(0, 0, 1).Then(new TextChange(10, 0, 1))));
            }

            public void ADeleteThatSwallowsTheFirstInsertAndMore_ReachesIntoTheOldText()
            {
                CheckEqual("(0,7,0)", Describe(new TextChange(2, 0, 3).Then(new TextChange(0, 10, 0))));
            }

            public void ADeleteThatUndoesTheFirstInsert_LeavesNothing()
            {
                CheckEqual("(3,0,0)", Describe(new TextChange(3, 0, 2).Then(new TextChange(3, 2, 0))));
            }

            public void AnInsertWhereTheFirstDeleted_ReplacesWhatWasDeleted()
            {
                CheckEqual("(4,3,2)", Describe(new TextChange(4, 3, 0).Then(new TextChange(4, 0, 2))));
            }

            public void AnEditThatStartsInsideTheFirstInsertAndEndsPastIt_ReachesIntoTheOldText()
            {
                CheckEqual("(2,4,3)", Describe(new TextChange(2, 1, 4).Then(new TextChange(4, 5, 1))));
            }

            public void TwoEmptyChanges_StayEmpty()
            {
                CheckEqual("(5,0,0)", Describe(new TextChange(5, 0, 0).Then(new TextChange(5, 0, 0))));
            }

            public void EveryPairOfSmallChanges_LeavesTheTextOutsideItUntouched()
            {
                const string original = "abcde";
                var failures = new System.Collections.Generic.List<string>();

                for (int firstStart = 0; firstStart <= original.Length; ++firstStart)
                {
                    for (int firstRemoved = 0; firstStart + firstRemoved <= original.Length; ++firstRemoved)
                    {
                        for (int firstInserted = 0; firstInserted <= 2; ++firstInserted)
                        {
                            var first = new TextChange(firstStart, firstRemoved, firstInserted);
                            string middle = Apply(original, first, new string('1', firstInserted));

                            for (int secondStart = 0; secondStart <= middle.Length; ++secondStart)
                            {
                                for (int secondRemoved = 0; secondStart + secondRemoved <= middle.Length;
                                    ++secondRemoved)
                                {
                                    for (int secondInserted = 0; secondInserted <= 2; ++secondInserted)
                                    {
                                        var second = new TextChange(secondStart, secondRemoved, secondInserted);
                                        string final = Apply(middle, second, new string('2', secondInserted));
                                        TextChange folded = first.Then(second);

                                        bool headKept = original.Substring(0, folded.Start)
                                            == final.Substring(0, folded.Start);
                                        bool tailKept = original.Substring(folded.Start + folded.RemovedLength)
                                            == final.Substring(folded.Start + folded.InsertedLength);
                                        if (!headKept || !tailKept)
                                        {
                                            failures.Add(Describe(first) + " then " + Describe(second) + " gave "
                                                + Describe(folded));
                                        }
                                    }
                                }
                            }
                        }
                    }
                }

                CheckEqual("", string.Join(", ", failures));
            }
        }
    }
}