using System;
using System.Collections.Generic;
using System.Globalization;

using Server.Items;
using Server.Mobiles;
using Server.Network;

namespace Server.Custom.Bridge
{
    /// <summary>
    ///     An event-owned NPC that answers questions. Protocol 7, EVENTS_PLAN.md Phase 12a.
    ///
    ///     EVENTS.md §G rates this the capability most worth having and gives the reason in one
    ///     line: *"this is literally a web form"*. An oracle is a greeting and a handful of
    ///     "when a player says X, reply Y" rows, and that is a form an event author can fill in
    ///     without knowing anything about Ultima Online — which is more than can be said for
    ///     choosing a spawn point.
    ///
    ///     ── Why this is ours and not `XmlDialog` ───────────────────────────────────────────────
    ///
    ///     ServUO already ships a complete dialogue engine in `XmlSpawner2.XmlDialog`, and its
    ///     `SpeechEntry` is the evidence that the shape below is right rather than invented: `Text`
    ///     plus a comma-separated `Keywords` list, an entry with no keywords being the one that
    ///     fires automatically, a proximity range (`defProximityRange = 3`), a conversation lock so
    ///     two players cannot talk over each other.
    ///
    ///     It is also exactly why this verb must not be built on it. `SpeechEntry` carries an
    ///     `Action` string — XmlSpawner's command-scripting language — and routing authored
    ///     dialogue through XmlDialog would leave an arbitrary-command field one field away from
    ///     an event author on the website. That is the `[set` that §G excludes, arriving through
    ///     the back door, in a subsystem this overlay does not own and an operator can switch off.
    ///
    ///     What the verb actually needs are two native virtuals on `Server.Mobile`:
    ///     `OnMovement`, which is delivered to **every** mobile in range (the `HandlesOnMovement`
    ///     filter applies only to Items — `Server/Mobile.cs:3369` against `:3375`), and
    ///     `HandlesOnSpeech`/`OnSpeech`. Nothing on the wire is executable: keywords and text.
    ///
    ///     ── It cannot be killed, moved or looted ───────────────────────────────────────────────
    ///
    ///     `CanBeDamaged()` is false, as `TownCrier`'s is, and it is `Blessed`, `Frozen` and
    ///     `CantWalk`. An event NPC that a player can drag out of the venue or kill for its robe is
    ///     an event NPC that stops being where the run's ledger says it is, and teardown deleting
    ///     something that has wandered two screens away is a worse outcome than it not moving.
    /// </summary>
    public class BridgeOracle : Mobile
    {
        /// <summary>One row of the form: what a player has to say, and what it answers.</summary>
        public sealed class Line
        {
            /// <summary>Lower-cased, already trimmed. Matched as substrings of what was said.</summary>
            public string[] Keywords;

            public string Text;
        }

        private string m_Greeting;
        private List<Line> m_Lines;

        /// <summary>
        ///     When each player was last spoken to, so an oracle cannot be farmed for spam.
        ///
        ///     Deliberately not serialized. It is a rate limiter, not state anybody is owed across
        ///     a restart, and a restart is exactly the moment a fresh greeting is *correct* — the
        ///     player is arriving at the venue again as far as the world is concerned.
        /// </summary>
        private readonly Dictionary<Mobile, DateTime> m_Greeted = new Dictionary<Mobile, DateTime>();

        private readonly Dictionary<Mobile, DateTime> m_Answered = new Dictionary<Mobile, DateTime>();

        [CommandProperty(AccessLevel.GameMaster, true)]
        public string Greeting { get { return m_Greeting; } set { m_Greeting = value; } }

        public List<Line> Lines
        {
            get { return m_Lines ?? (m_Lines = new List<Line>()); }
            set { m_Lines = value; }
        }

        public BridgeOracle()
            : this(null, null, 0, false)
        {
        }

        public BridgeOracle(string name, string title, int hue, bool female)
        {
            Name = String.IsNullOrEmpty(name) ? "the oracle" : name;
            Title = title;
            Female = female;
            Body = female ? 0x191 : 0x190;
            Hue = hue > 0 ? hue : Utility.RandomSkinHue();

            InitStats(100, 100, 25);

            AddItem(new Robe(Utility.RandomNeutralHue()));
            AddItem(new Sandals());

            // See the class header. A run's ledger records where this NPC is; letting the world
            // move it would make that record a lie within a minute of a curious player arriving.
            Blessed = true;
            Frozen = true;
            CantWalk = true;
        }

        public BridgeOracle(Serial serial)
            : base(serial)
        {
        }

        public override bool CanBeDamaged()
        {
            return false;
        }

        public override bool ClickTitle { get { return false; } }

        // ---- the greeting ----

        /// <summary>
        ///     Greet a player who has just come into range.
        ///
        ///     "Just come into range" rather than "is in range": `OnMovement` fires on every step,
        ///     so greeting on proximity alone would have the oracle shouting at anyone who walked
        ///     past it. The old location is compared as well as the new one, which makes this fire
        ///     once per approach, and the per-player cooldown catches the player who paces the line.
        /// </summary>
        public override void OnMovement(Mobile m, Point3D oldLocation)
        {
            base.OnMovement(m, oldLocation);

            if (String.IsNullOrEmpty(m_Greeting) || m == this || m.Deleted || Deleted)
                return;

            if (!(m is PlayerMobile) || !m.Alive || m.Map != Map)
                return;

            var range = BridgeConfig.EventsOracleGreetRange;

            if (!InRange(m, range) || InRange(oldLocation, range))
                return;

            if (!Recent(m_Greeted, m, BridgeConfig.EventsOracleGreetCooldownSec))
                return;

            m_Greeted[m] = DateTime.UtcNow;
            Direction = GetDirectionTo(m);
            Say(m_Greeting);
        }

        // ---- the keyword lines ----

        public override bool HandlesOnSpeech(Mobile from)
        {
            return m_Lines != null && m_Lines.Count > 0 && from.Alive && from is PlayerMobile &&
                   InRange(from, BridgeConfig.EventsOracleSpeechRange);
        }

        public override void OnSpeech(SpeechEventArgs e)
        {
            base.OnSpeech(e);

            if (e.Handled || m_Lines == null || m_Lines.Count == 0 || Deleted)
                return;

            var from = e.Mobile;

            if (from == null || !from.Alive || !(from is PlayerMobile) ||
                !InRange(from, BridgeConfig.EventsOracleSpeechRange))
                return;

            var said = (e.Speech ?? "").ToLower(CultureInfo.InvariantCulture);

            if (said.Length == 0)
                return;

            var line = Match(said);

            if (line == null)
                return;

            // The cooldown is consulted only once something actually matched. Checking it first
            // would let a player burn their own cooldown on an unrelated sentence and then find
            // the oracle mute when they finally said the word.
            if (!Recent(m_Answered, from, BridgeConfig.EventsOracleAnswerCooldownSec))
                return;

            m_Answered[from] = DateTime.UtcNow;
            Direction = GetDirectionTo(from);
            Say(line.Text);

            e.Handled = true;
        }

        private Line Match(string said)
        {
            for (int i = 0; i < m_Lines.Count; i++)
            {
                var line = m_Lines[i];

                if (line == null || line.Keywords == null || String.IsNullOrEmpty(line.Text))
                    continue;

                for (int j = 0; j < line.Keywords.Length; j++)
                {
                    var keyword = line.Keywords[j];

                    if (!String.IsNullOrEmpty(keyword) && said.IndexOf(keyword, StringComparison.Ordinal) >= 0)
                        return line;
                }
            }

            return null;
        }

        /// <summary>
        ///     Whether enough time has passed to speak to this player again, pruning as it goes.
        ///
        ///     The prune matters: without it a busy venue leaves one dictionary entry per player
        ///     who ever walked past, held by a strong reference to a `Mobile` that may since have
        ///     been deleted, for as long as the NPC exists.
        /// </summary>
        private static bool Recent(Dictionary<Mobile, DateTime> seen, Mobile m, int cooldownSec)
        {
            var now = DateTime.UtcNow;
            var cooldown = TimeSpan.FromSeconds(cooldownSec);

            if (seen.Count > 64)
            {
                List<Mobile> stale = null;

                foreach (var pair in seen)
                {
                    if (pair.Key == null || pair.Key.Deleted || now - pair.Value > cooldown)
                        (stale ?? (stale = new List<Mobile>())).Add(pair.Key);
                }

                if (stale != null)
                {
                    for (int i = 0; i < stale.Count; i++)
                        seen.Remove(stale[i]);
                }
            }

            DateTime last;

            return !seen.TryGetValue(m, out last) || now - last >= cooldown;
        }

        // ---- persistence ----

        public override void Serialize(GenericWriter writer)
        {
            base.Serialize(writer);

            writer.Write(0); // version

            writer.Write(m_Greeting ?? "");

            var lines = m_Lines ?? new List<Line>();
            writer.Write(lines.Count);

            foreach (var line in lines)
            {
                writer.Write(String.Join(",", line.Keywords ?? new string[0]));
                writer.Write(line.Text ?? "");
            }
        }

        public override void Deserialize(GenericReader reader)
        {
            base.Deserialize(reader);

            reader.ReadInt(); // version

            m_Greeting = reader.ReadString();

            var count = reader.ReadInt();
            m_Lines = new List<Line>(count);

            for (int i = 0; i < count; i++)
            {
                var keywords = reader.ReadString() ?? "";
                var text = reader.ReadString();

                m_Lines.Add(new Line
                {
                    Keywords = keywords.Length == 0 ? new string[0] : keywords.Split(','),
                    Text = text,
                });
            }
        }
    }
}