using System.Collections.Generic;

namespace Ink.Parsed
{
    [System.Flags]
    public enum SequenceType
    {
        Stopping = 1, // default
        Cycle = 2,
        Shuffle = 4,
        Once = 8
    }

    public class Sequence : Parsed.Object
    {

        public List<Parsed.Object> sequenceElements;
        public SequenceType sequenceType;

        public Sequence (List<ContentList> elementContentLists, SequenceType sequenceType)
        {
            this.sequenceType = sequenceType;
            this.sequenceElements = new List<Parsed.Object> ();

            foreach (var elementContentList in elementContentLists) {

                var contentObjs = elementContentList.content;

                Parsed.Object seqElObject = null;

                // Don't attempt to create a weave for the sequence element 
                // if the content list is empty. Weaves don't like it!
                if (contentObjs == null || contentObjs.Count == 0)
                    seqElObject = elementContentList;
                else
                    seqElObject = new Weave (contentObjs);
                
                this.sequenceElements.Add (seqElObject);
                AddContent (seqElObject);
            }
        }

        // Generate runtime code that looks like:
        //
        //   chosenIndex = MIN(sequence counter, num elements) e.g. for "Stopping"
        //   if chosenIndex == 0, divert to s0
        //   if chosenIndex == 1, divert to s1  [etc]
        //
        //   - s0:
        //      <content for sequence element>
        //      divert to no-op
        //   - s1:
        //      <content for sequence element>
        //      divert to no-op
        //   - s2:
        //      empty branch if using "once"
        //      divert to no-op
        //
        //    no-op
        //
        public override Runtime.Object GenerateRuntimeObject ()
        {
            var container = new Runtime.Container ();
            container.visitsShouldBeCounted = true;
            container.countingAtStartOnly = true;

            _sequenceDivertsToResove = new List<SequenceDivertToResolve> ();

            // Get sequence read count
            container.AddContent (Runtime.ControlCommand.EvalStart ());
            container.AddContent (Runtime.ControlCommand.VisitIndex ());

            bool once = (sequenceType & SequenceType.Once) > 0;
            bool cycle = (sequenceType & SequenceType.Cycle) > 0;
            bool stopping = (sequenceType & SequenceType.Stopping) > 0;
            bool shuffle = (sequenceType & SequenceType.Shuffle) > 0;

            var seqBranchCount = sequenceElements.Count;
            if (once) seqBranchCount++;

            // Chosen sequence index:
            //  - Stopping: take the MIN(read count, num elements - 1)
            //  - Once: take the MIN(read count, num elements)
            //    (the last one being empty)
            if (stopping || once) {
                //var limit = stopping ? seqBranchCount-1 : seqBranchCount;
                container.AddContent (new Runtime.IntValue (seqBranchCount-1));
                container.AddContent (Runtime.NativeFunctionCall.CallWithName ("MIN"));
            } 

            // - Cycle: take (read count % num elements)
            else if (cycle) {
                container.AddContent (new Runtime.IntValue (sequenceElements.Count));
                container.AddContent (Runtime.NativeFunctionCall.CallWithName ("%"));
            }

            // Shuffle
            if (shuffle) {

                // Create point to return to when sequence is complete
                var postShuffleNoOp = Runtime.ControlCommand.NoOp();

                // When visitIndex == lastIdx, we skip the shuffle
                if ( once || stopping )
                {
                    // if( visitIndex == lastIdx ) -> skipShuffle
                    int lastIdx = stopping ? sequenceElements.Count - 1 : sequenceElements.Count;
                    container.AddContent(Runtime.ControlCommand.Duplicate());
                    container.AddContent(new Runtime.IntValue(lastIdx));
                    container.AddContent(Runtime.NativeFunctionCall.CallWithName("=="));

                    var skipShuffleDivert = new Runtime.Divert();
                    skipShuffleDivert.isConditional = true;
                    container.AddContent(skipShuffleDivert);

                    AddDivertToResolve(skipShuffleDivert, postShuffleNoOp);
                }

                // This one's a bit more complex! Choose the index at runtime.
                var elementCountToShuffle = sequenceElements.Count;
                if (stopping) elementCountToShuffle--;
                container.AddContent (new Runtime.IntValue (elementCountToShuffle));
                container.AddContent (Runtime.ControlCommand.SequenceShuffleIndex ());
                if (once || stopping) container.AddContent(postShuffleNoOp);
            }

            container.AddContent (Runtime.ControlCommand.EvalEnd ());

            // Create point to return to when sequence is complete
            var postSequenceNoOp = Runtime.ControlCommand.NoOp();

            // Each of the main sequence branches, and one extra empty branch if 
            // we have a "once" sequence.
            for (var elIndex=0; elIndex<seqBranchCount; elIndex++) {

                // This sequence element:
                //  if( chosenIndex == this index ) divert to this sequence element
                // duplicate chosen sequence index, since it'll be consumed by "=="
                container.AddContent (Runtime.ControlCommand.EvalStart ());
                container.AddContent (Runtime.ControlCommand.Duplicate ()); 
                container.AddContent (new Runtime.IntValue (elIndex));
                container.AddContent (Runtime.NativeFunctionCall.CallWithName ("=="));
                container.AddContent (Runtime.ControlCommand.EvalEnd ());

                // Divert branch for this sequence element
                var sequenceDivert = new Runtime.Divert ();
                sequenceDivert.isConditional = true;
                container.AddContent (sequenceDivert);

                Runtime.Container contentContainerForSequenceBranch;

                // Generate content for this sequence element
                if ( elIndex < sequenceElements.Count ) {
                    var el = sequenceElements[elIndex];
                    contentContainerForSequenceBranch = (Runtime.Container)el.runtimeObject;
                } 

                // Final empty branch for "once" sequences
                else {
                    contentContainerForSequenceBranch = new Runtime.Container();
                }

                contentContainerForSequenceBranch.name = "s" + elIndex;
                contentContainerForSequenceBranch.InsertContent(Runtime.ControlCommand.PopEvaluatedValue(), 0);

                // When sequence element is complete, divert back to end of sequence
                var seqBranchCompleteDivert = new Runtime.Divert ();
                contentContainerForSequenceBranch.AddContent (seqBranchCompleteDivert);
                container.AddToNamedContentOnly (contentContainerForSequenceBranch);

                // Save the diverts for reference resolution later (in ResolveReferences)
                AddDivertToResolve (sequenceDivert, contentContainerForSequenceBranch);
                AddDivertToResolve (seqBranchCompleteDivert, postSequenceNoOp);
            }

            container.AddContent (postSequenceNoOp);

            return container;
        }

        void AddDivertToResolve(Runtime.Divert divert, Runtime.Object targetContent)
        {
            _sequenceDivertsToResove.Add( new SequenceDivertToResolve() { 
                divert = divert, 
                targetContent = targetContent
            });
        }

        public override void ResolveReferences(Story context)
        {
            base.ResolveReferences (context);

            foreach (var toResolve in _sequenceDivertsToResove) {
                toResolve.divert.targetPath = toResolve.targetContent.path;
            }
        }

        class SequenceDivertToResolve
        {
            public Runtime.Divert divert;
            public Runtime.Object targetContent;
        }
        List<SequenceDivertToResolve> _sequenceDivertsToResove;
    }
}