// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#if DEBUG
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Net;

namespace System.Text.RegularExpressions.Symbolic
{
    internal sealed partial class SymbolicRegexMatcher<TSet>
    {
        /// <inheritdoc cref="Regex.SaveDGML(TextWriter, int)"/>
        [ExcludeFromCodeCoverage(Justification = "Currently only used for testing")]
        public override void SaveDGML(TextWriter writer, int maxLabelLength)
        {
            lock (this)
            {
                if (maxLabelLength < 0)
                    maxLabelLength = int.MaxValue;

                Dictionary<(int Source, int Target), (TSet Rule, List<int> NfaTargets)> transitions = GatherTransitions(this);

                writer.WriteLine("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
                writer.WriteLine("<DirectedGraph xmlns=\"http://schemas.microsoft.com/vs/2009/dgml\" ZoomLevel=\"1.5\" GraphDirection=\"TopToBottom\" >");
                writer.WriteLine("    <Nodes>");
                writer.WriteLine("        <Node Id=\"dfa\" Label=\" \" Group=\"Collapsed\" Category=\"DFA\" DFAInfo=\"{0}\" />", FormatInfo(this, transitions.Count));
                writer.WriteLine("        <Node Id=\"dfainfo\" Category=\"DFAInfo\" Label=\"{0}\"/>", FormatInfo(this, transitions.Count));
                foreach (MatchingState<TSet> state in _stateCache.Values)
                {
                    string info = CharKind.DescribePrev(state.PrevCharKind);
                    string deriv = WebUtility.HtmlEncode(state.Node.ToString());
                    string nodeDgmlView = $"{(string.IsNullOrEmpty(info) ? info : $"Previous: {info}&#13;")}{(string.IsNullOrEmpty(deriv) ? "()" : deriv)}";

                    writer.WriteLine("        <Node Id=\"{0}\" Label=\"{0}\" Category=\"State\" Group=\"Collapsed\" StateInfo=\"{1}\">", state.Id, nodeDgmlView);
                    if (_stateFlagsArray[state.Id].IsInitial())
                    {
                        writer.WriteLine("            <Category Ref=\"InitialState\" />");
                    }
                    if (state.Node.CanBeNullable)
                    {
                        writer.WriteLine("            <Category Ref=\"FinalState\" />");
                    }
                    writer.WriteLine("        </Node>");
                    writer.WriteLine("        <Node Id=\"{0}info\" Label=\"{1}\" Category=\"StateInfo\"/>", state.Id, nodeDgmlView);
                }
                writer.WriteLine("    </Nodes>");
                writer.WriteLine("    <Links>");
                foreach (MatchingState<TSet> initialState in GetInitialStates(this))
                {
                    writer.WriteLine("        <Link Source=\"dfa\" Target=\"{0}\" Label=\"\" Category=\"StartTransition\" />", initialState.Id);
                }
                writer.WriteLine("        <Link Source=\"dfa\" Target=\"dfainfo\" Label=\"\" Category=\"Contains\" />");

                foreach (KeyValuePair<(int Source, int Target), (TSet Rule, List<int> NfaTargets)> transition in transitions)
                {
                    string label = DescribeLabel(transition.Value.Rule, _builder);
                    string info = "";
                    if (label.Length > maxLabelLength)
                    {
                        info = $"FullLabel = \"{label}\" ";
                        label = string.Concat(label.AsSpan(0, maxLabelLength), "..");
                    }

                    writer.WriteLine($"        <Link Source=\"{transition.Key.Source}\" Target=\"{transition.Key.Target}\" Label=\"{label}\" Category=\"NonEpsilonTransition\" {info}/>");
                    // Render NFA transitions as labelless "epsilon" transitions (i.e. ones that don't consume a character)
                    // from the target of the DFA transition.
                    foreach (int nfaTarget in transition.Value.NfaTargets)
                    {
                        writer.WriteLine($"        <Link Source=\"{transition.Key.Target}\" Target=\"{nfaTarget}\" Category=\"EpsilonTransition\"/>");
                    }
                }

                foreach (MatchingState<TSet> state in _stateCache.Values)
                {
                    writer.WriteLine("        <Link Source=\"{0}\" Target=\"{0}info\" Category=\"Contains\" />", state.Id);
                }

                writer.WriteLine("    </Links>");
                writer.WriteLine("    <Categories>");
                writer.WriteLine("        <Category Id=\"DFA\" Label=\"DFA\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"EpsilonTransition\" Label=\"Epsilon transition\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"StartTransition\" Label=\"Initial transition\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"FinalLabel\" Label=\"Final transition\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"FinalState\" Label=\"Final\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"SinkState\" Label=\"Sink state\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"EpsilonState\" Label=\"Epsilon state\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"InitialState\" Label=\"Initial\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"NonEpsilonTransition\" Label=\"Nonepsilon transition\" IsTag=\"True\" />");
                writer.WriteLine("        <Category Id=\"State\" Label=\"State\" IsTag=\"True\" />");
                writer.WriteLine("    </Categories>");
                writer.WriteLine("    <Styles>");
                writer.WriteLine("        <Style TargetType=\"Node\" GroupLabel=\"InitialState\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('InitialState')\" />");
                writer.WriteLine("            <Setter Property=\"Background\" Value=\"lightblue\" />");
                writer.WriteLine("            <Setter Property=\"MinWidth\" Value=\"0\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Node\" GroupLabel=\"FinalState\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('FinalState')\" />");
                writer.WriteLine("            <Setter Property=\"Background\" Value=\"lightgreen\" />");
                writer.WriteLine("            <Setter Property=\"StrokeThickness\" Value=\"4\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Node\" GroupLabel=\"State\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('State')\" />");
                writer.WriteLine("            <Setter Property=\"Stroke\" Value=\"black\" />");
                writer.WriteLine("            <Setter Property=\"Background\" Value=\"white\" />");
                writer.WriteLine("            <Setter Property=\"MinWidth\" Value=\"0\" />");
                writer.WriteLine("            <Setter Property=\"FontSize\" Value=\"12\" />");
                writer.WriteLine("            <Setter Property=\"FontFamily\" Value=\"Arial\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Link\" GroupLabel=\"NonEpsilonTransition\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('NonEpsilonTransition')\" />");
                writer.WriteLine("            <Setter Property=\"FontSize\" Value=\"18\" />");
                writer.WriteLine("            <Setter Property=\"FontFamily\" Value=\"Arial\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Link\" GroupLabel=\"StartTransition\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('StartTransition')\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Link\" GroupLabel=\"EpsilonTransition\" ValueLabel=\"True\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('EpsilonTransition')\" />");
                writer.WriteLine("            <Setter Property=\"StrokeDashArray\" Value=\"8 8\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Link\" GroupLabel=\"FinalLabel\" ValueLabel=\"False\">");
                writer.WriteLine("            <Condition Expression=\"HasCategory('FinalLabel')\" />");
                writer.WriteLine("            <Setter Property=\"StrokeDashArray\" Value=\"8 8\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Node\" GroupLabel=\"StateInfo\" ValueLabel=\"True\">");
                writer.WriteLine("            <Setter Property=\"Stroke\" Value=\"white\" />");
                writer.WriteLine("            <Setter Property=\"FontSize\" Value=\"18\" />");
                writer.WriteLine("            <Setter Property=\"FontFamily\" Value=\"Arial\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("        <Style TargetType=\"Node\" GroupLabel=\"DFAInfo\" ValueLabel=\"True\">");
                writer.WriteLine("            <Setter Property=\"Stroke\" Value=\"white\" />");
                writer.WriteLine("            <Setter Property=\"FontSize\" Value=\"18\" />");
                writer.WriteLine("            <Setter Property=\"FontFamily\" Value=\"Arial\" />");
                writer.WriteLine("        </Style>");
                writer.WriteLine("    </Styles>");
                writer.WriteLine("</DirectedGraph>");
            }

            // This function gathers all transitions in the given builder and groups them by (source,destination) state ID
            static Dictionary<(int Source, int Target), (TSet Rule, List<int> NfaTargets)> GatherTransitions(SymbolicRegexMatcher<TSet> matcher)
            {
                Dictionary<(int Source, int Target), (TSet Rule, List<int> NfaTargets)> result = new();
                foreach (MatchingState<TSet> source in matcher._stateCache.Values)
                {
                    // Get the span of entries in delta that gives the transitions for the different minterms
                    ReadOnlySpan<int> deltas = matcher.GetDeltasFor(source);
                    ReadOnlySpan<int[]?> nfaDeltas = matcher.GetNfaDeltasFor(source);
                    Debug.Assert(deltas.Length == matcher._minterms.Length);
                    for (int i = 0; i < deltas.Length; ++i)
                    {
                        // negative entries are transitions not explored yet, so skip them
                        int targetId = deltas[i];
                        if (targetId >= 0)
                        {
                            // Get or create the data for this (source,destination) state ID pair
                            (int Source, int Target) key = (source.Id, targetId);
                            if (!result.TryGetValue(key, out (TSet Rule, List<int> NfaTargets) entry))
                            {
                                entry = (matcher.Solver.Empty, new List<int>());
                            }
                            // If this state has an NFA transition for the same minterm, then associate
                            // those with the transition.
                            if (nfaDeltas.Length > 0 && nfaDeltas[i] is int[] nfaTargets)
                            {
                                foreach (int nfaTarget in nfaTargets)
                                {
                                    entry.NfaTargets.Add(matcher._nfaCoreIdArray[nfaTarget]);
                                }
                            }
                            // Expand the rule for this minterm
                            result[key] = (matcher.Solver.Or(entry.Rule, matcher._minterms[i]), entry.NfaTargets);
                        }
                    }
                }
                return result;
            }

            static string FormatInfo(SymbolicRegexMatcher<TSet> matcher, int transitionCount)
            {
                StringBuilder sb = new();
                sb.Append($"States = {matcher._stateCache.Count}&#13;");
                sb.Append($"Transitions = {transitionCount}&#13;");
                sb.Append($"Min Terms ({matcher.Solver.GetMinterms()!.Length}) = ").AppendJoin(',',
                    DescribeLabels(matcher.Solver.GetMinterms()!, matcher._builder));
                return sb.ToString();
            }

            static IEnumerable<string> DescribeLabels(IEnumerable<TSet> labels, SymbolicRegexBuilder<TSet> builder)
            {
                foreach (TSet label in labels)
                {
                    yield return DescribeLabel(label, builder);
                }
            }

            static string DescribeLabel(TSet label, SymbolicRegexBuilder<TSet> builder) =>
                WebUtility.HtmlEncode(builder._solver.PrettyPrint(label, builder._charSetSolver));

            static IEnumerable<MatchingState<TSet>> GetInitialStates(SymbolicRegexMatcher<TSet> matcher)
            {
                foreach (MatchingState<TSet> state in matcher._dotstarredInitialStates)
                    yield return state;
                foreach (MatchingState<TSet> state in matcher._initialStates)
                    yield return state;
                foreach (MatchingState<TSet> state in matcher._reverseInitialStates)
                    yield return state;
            }
        }
    }
}
#endif