using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.Web.Script.Serialization;

namespace Server.Custom.Bridge
{
    /// <summary>
    ///     Outbound JSON is written by hand into a StringBuilder. It runs on the Core thread for
    ///     every emitted event, and the measured budget in https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/link/PLAN.md assumes this cost, not a
    ///     reflection serializer's.
    ///
    ///     Inbound JSON is parsed with JavaScriptSerializer. Commands arrive at human rates, so
    ///     correctness beats speed there, and parsing happens on the reader thread anyway.
    /// </summary>
    public static class BridgeJson
    {
        private static readonly DateTime Epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        [ThreadStatic]
        private static JavaScriptSerializer _parser;

        public static long NowMs()
        {
            return (long)(DateTime.UtcNow - Epoch).TotalMilliseconds;
        }

        // ---- outbound ----

        /// <summary>Opens an object and writes the `t` and `kind` fields.</summary>
        public static StringBuilder Begin(string kind)
        {
            var sb = new StringBuilder(256);
            sb.Append("{\"t\":").Append(NowMs());
            sb.Append(",\"kind\":\"").Append(kind).Append('"');
            return sb;
        }

        public static StringBuilder Str(this StringBuilder sb, string name, string value)
        {
            sb.Append(",\"").Append(name).Append("\":");

            if (value == null)
                sb.Append("null");
            else
                Escape(sb, value);

            return sb;
        }

        public static StringBuilder Num(this StringBuilder sb, string name, long value)
        {
            sb.Append(",\"").Append(name).Append("\":").Append(value);
            return sb;
        }

        public static StringBuilder Num(this StringBuilder sb, string name, double value)
        {
            sb.Append(",\"").Append(name).Append("\":")
              .Append(value.ToString("R", CultureInfo.InvariantCulture));
            return sb;
        }

        public static StringBuilder Bool(this StringBuilder sb, string name, bool value)
        {
            sb.Append(",\"").Append(name).Append("\":").Append(value ? "true" : "false");
            return sb;
        }

        /// <summary>Serial as the canonical "0x1A2B" string the sidecar keys on.</summary>
        public static StringBuilder Ser(this StringBuilder sb, string name, Serial serial)
        {
            sb.Append(",\"").Append(name).Append("\":\"0x")
              .Append(serial.Value.ToString("X")).Append('"');
            return sb;
        }

        /// <summary>
        ///     Writes a nested actor object: serial, name, account (when there is one), the linked
        ///     webId (when the account is linked), and the player flag. A `null` mobile writes null.
        ///     The richer counterpart to BridgeEvents' internal writer, used by the Part B streams so a
        ///     guild leader / joiner / governor can be attributed to a site user without a lookup.
        /// </summary>
        public static StringBuilder Actor(this StringBuilder sb, string name, Mobile m)
        {
            sb.Append(",\"").Append(name).Append("\":");
            WriteActor(sb, m);
            return sb;
        }

        /// <summary>
        ///     Writes a named array of actor objects — a guild roster (Protocol 4) being the first
        ///     caller. Every other outbound helper here emits a leading `,"name":`, so an array
        ///     element needs the bare object; that is why <see cref="WriteActor"/> exists separately
        ///     rather than <see cref="Actor"/> being reused.
        ///
        ///     `count` bounds how many are written, because a roster frame must stay a bounded line
        ///     (Bridge.GuildRosterMembersPerLine). A null entry in the sequence is skipped rather
        ///     than written as null, so the array is always a list of real members and a caller can
        ///     trust its length.
        ///
        ///     `withGuildRank` adds each member's guild rank to their object. It is a parameter
        ///     rather than always-on because rank is a property of a mobile's membership of THIS
        ///     guild, not of the mobile — every other actor this bridge writes is a bystander,
        ///     a killer, a governor, and guild rank is meaningless on all of them.
        /// </summary>
        public static StringBuilder Actors(
            this StringBuilder sb, string name, IList<Mobile> mobiles, int start, int count,
            bool withGuildRank = false)
        {
            sb.Append(",\"").Append(name).Append("\":[");

            if (mobiles != null)
            {
                var end = Math.Min(start + count, mobiles.Count);
                bool first = true;

                for (int i = start; i < end; i++)
                {
                    var m = mobiles[i];

                    if (m == null)
                        continue;

                    if (!first)
                        sb.Append(',');

                    if (withGuildRank)
                        WriteGuildMember(sb, m);
                    else
                        WriteActor(sb, m);

                    first = false;
                }
            }

            sb.Append(']');
            return sb;
        }

        /// <summary>
        ///     A named array of actor objects each carrying a damage total — a boss kill's damage
        ///     table (Protocol 6), and the first actor array whose entries are ranked rather than
        ///     merely listed.
        ///
        ///     The pairs are written in the order given, so the CALLER owns the sort. That is
        ///     deliberate: "the top damagers" is a judgement about a fight, and the shard's job is
        ///     to report the numbers it holds rather than to decide what counts as a contribution.
        ///
        ///     Each entry is the standard actor object plus `damage`, which means it carries `acct`
        ///     and `webId` and is therefore governed by the website's locked-field rule exactly as
        ///     every other actor is. A shard that considers the whole table too revealing hides it
        ///     with one field rule rather than by dropping the kind.
        /// </summary>
        public static StringBuilder Damagers(
            this StringBuilder sb, string name, IList<KeyValuePair<Mobile, int>> pairs, int count)
        {
            sb.Append(",\"").Append(name).Append("\":[");

            if (pairs != null)
            {
                var end = Math.Min(count, pairs.Count);
                bool first = true;

                for (int i = 0; i < end; i++)
                {
                    var m = pairs[i].Key;

                    if (m == null)
                        continue;

                    if (!first)
                        sb.Append(',');

                    sb.Append('{');
                    WriteActorFields(sb, m);
                    sb.Append(",\"damage\":").Append(pairs[i].Value);
                    sb.Append('}');

                    first = false;
                }
            }

            sb.Append(']');
            return sb;
        }

        /// <summary>
        ///     A roster member: the standard actor object plus the member's rank in their guild.
        ///
        ///     **Only the raw rank is emitted, never a resolved label.** ServUO names the five
        ///     standard ranks with cliloc ids (1062959–1062963) and ships no text for them, so the
        ///     shard cannot produce "Warlord" without a client-file table it does not have. The
        ///     website module does have one, and resolving a game term is its job in any case.
        ///
        ///     `rank` is the numeric rank, 0–4, with 4 being Leader (`RankDefinition.Ranks`). A
        ///     custom rank definition may carry a literal string instead of a cliloc, so `rankName`
        ///     is written when there is one and `rankCliloc` when there is not; a shard that has
        ///     replaced the rank table therefore keeps its own naming rather than being flattened
        ///     into the stock five.
        ///
        ///     A member with no readable rank — a mobile that is not a PlayerMobile, or one whose
        ///     GuildRank is null — is written with no rank fields at all rather than a fabricated
        ///     default. Absent means "not known", and a consumer that treated a missing rank as 0
        ///     would silently demote them.
        ///
        ///     **Staff are deliberately written with no rank, and this is not a rounding error.**
        ///     `PlayerMobile.GuildRank` returns `RankDefinition.Leader` for anyone at GameMaster or
        ///     above, whatever their actual rank — a gameplay convenience so staff can operate a
        ///     guild stone, and emphatically not a claim about who leads the guild. The true value
        ///     is in a private field with no accessor, so the only honest options are "Leader" and
        ///     "not known", and publishing a staff member as a guild leader on a public roster is
        ///     the worse of the two by a wide margin. A staff account that genuinely leads its guild
        ///     shows as an unranked member, which is a visible gap rather than a false claim.
        /// </summary>
        private static void WriteGuildMember(StringBuilder sb, Mobile m)
        {
            if (m == null)
            {
                sb.Append("null");
                return;
            }

            sb.Append('{');
            WriteActorFields(sb, m);

            var pm = m as Server.Mobiles.PlayerMobile;
            var rank = pm == null || pm.AccessLevel >= AccessLevel.GameMaster ? null : pm.GuildRank;

            if (rank != null)
            {
                sb.Append(",\"rank\":").Append(rank.Rank);

                if (!string.IsNullOrEmpty(rank.Name.String))
                {
                    sb.Append(",\"rankName\":");
                    Escape(sb, rank.Name.String);
                }
                else if (rank.Name.Number > 0)
                {
                    sb.Append(",\"rankCliloc\":").Append(rank.Name.Number);
                }
            }

            sb.Append('}');
        }

        /// <summary>
        ///     One bare actor object, with no leading field name: serial, name, account (when there
        ///     is one), the linked webId (when the account is linked), and the player flag. A `null`
        ///     mobile writes null.
        ///
        ///     `acct` and `webId` are the site-identity fields, and they are emitted here
        ///     unconditionally by design — the sidecar is a forwarder, and deciding who may see them
        ///     is the website's job (it projects per the shard visibility rungs). Note that `acct` is
        ///     genuinely optional: a PlayerMobile can have no Account at all.
        /// </summary>
        private static void WriteActor(StringBuilder sb, Mobile m)
        {
            if (m == null)
            {
                sb.Append("null");
                return;
            }

            sb.Append('{');
            WriteActorFields(sb, m);
            sb.Append('}');
        }

        /// <summary>
        ///     The actor fields, with no braces, so a caller can add its own.
        ///
        ///     Split out for <see cref="WriteGuildMember"/>, which is the same object plus guild
        ///     rank. Note the first field is written WITHOUT a leading comma and every later one
        ///     with, so this must be the first thing inside its object.
        /// </summary>
        private static void WriteActorFields(StringBuilder sb, Mobile m)
        {
            sb.Append("\"serial\":\"0x").Append(m.Serial.Value.ToString("X")).Append('"');

            sb.Append(",\"name\":");
            Escape(sb, m.Name ?? "");

            var acct = m.Account as Accounting.Account;
            if (acct != null)
            {
                sb.Append(",\"acct\":");
                Escape(sb, acct.Username);

                var webId = BridgeAccountLink.WebIdFor(acct);
                if (webId != null)
                {
                    sb.Append(",\"webId\":");
                    Escape(sb, webId);
                }
            }

            sb.Append(",\"player\":").Append(m.Player ? "true" : "false");
        }

        /// <summary>Closes the object. The trailing newline is the frame delimiter.</summary>
        public static string End(this StringBuilder sb)
        {
            sb.Append('}');
            return sb.ToString();
        }

        /// <summary>
        ///     Writes a bare JSON string value, or `null`, with no leading comma and no field name.
        ///     For the hand-built arrays the event plane emits, where <see cref="Escape"/> would
        ///     throw on the null a nullable field is entitled to be.
        /// </summary>
        public static void Text(StringBuilder sb, string value)
        {
            if (value == null)
                sb.Append("null");
            else
                Escape(sb, value);
        }

        public static void Escape(StringBuilder sb, string value)
        {
            sb.Append('"');

            for (int i = 0; i < value.Length; i++)
            {
                char c = value[i];

                switch (c)
                {
                    case '"': sb.Append("\\\""); break;
                    case '\\': sb.Append("\\\\"); break;
                    case '\n': sb.Append("\\n"); break;
                    case '\r': sb.Append("\\r"); break;
                    case '\t': sb.Append("\\t"); break;
                    case '\b': sb.Append("\\b"); break;
                    case '\f': sb.Append("\\f"); break;
                    default:
                        if (c < ' ')
                            sb.Append("\\u").Append(((int)c).ToString("x4"));
                        else
                            sb.Append(c);
                        break;
                }
            }

            sb.Append('"');
        }

        // ---- rewriting an already-built line (protocol 6) ----
        //
        // BridgeIdempotency replays a stored reply under the REPEAT's correlation id. It could
        // parse the line, edit the dictionary and re-serialize, but a round trip through
        // JavaScriptSerializer would silently renormalise every number and string in a reply this
        // file went to the trouble of writing by hand. These two edit the text instead, so a
        // replayed reply is byte-for-byte the original apart from the field that had to change.

        /// <summary>
        ///     Replaces the value of a top-level STRING field, honouring backslash escapes when
        ///     finding the value's end. Returns null if the field is not present as a string —
        ///     never a half-rewritten line.
        /// </summary>
        public static string RewriteStringField(string line, string name, string value)
        {
            if (line == null || name == null || value == null)
                return null;

            // The leading comma is part of the needle: every top-level field is written by Str()
            // after Begin() has already emitted `t` and `kind`, so a real one always has one. It
            // is the cheapest thing that stops the search matching the same text inside a value.
            var needle = ",\"" + name + "\":\"";
            int at = line.IndexOf(needle, StringComparison.Ordinal);

            if (at < 0)
                return null;

            int valueStart = at + needle.Length;
            int i = valueStart;

            while (i < line.Length)
            {
                char c = line[i];

                if (c == '\\')
                {
                    i += 2; // an escape consumes the next character, whatever it is
                    continue;
                }

                if (c == '"')
                    break;

                i++;
            }

            if (i >= line.Length)
                return null; // unterminated: refuse rather than guess

            var sb = new StringBuilder(line.Length + value.Length);
            sb.Append(line, 0, valueStart - 1); // up to and excluding the opening quote
            Escape(sb, value);
            sb.Append(line, i + 1, line.Length - i - 1);

            return sb.ToString();
        }

        /// <summary>
        ///     Appends `"name":true` to an already-closed object. Returns the line unchanged if it
        ///     is not one, so a malformed reply is passed through rather than corrupted further.
        /// </summary>
        public static string WithTrueFlag(string line, string name)
        {
            if (String.IsNullOrEmpty(line) || line[line.Length - 1] != '}')
                return line;

            return line.Substring(0, line.Length - 1) + ",\"" + name + "\":true}";
        }

        // ---- inbound ----

        /// <summary>
        ///     Parses one line into a dictionary. Returns null on malformed input rather than
        ///     throwing: a bad line from the sidecar must never reach a game code path.
        /// </summary>
        public static Dictionary<string, object> Parse(string line)
        {
            if (String.IsNullOrEmpty(line))
                return null;

            try
            {
                if (_parser == null)
                {
                    _parser = new JavaScriptSerializer();
                    _parser.MaxJsonLength = 1 << 20;
                }

                return _parser.Deserialize<Dictionary<string, object>>(line);
            }
            catch
            {
                return null;
            }
        }

        public static string GetString(Dictionary<string, object> o, string key)
        {
            object v;

            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return null;

            return v as string ?? Convert.ToString(v, CultureInfo.InvariantCulture);
        }

        /// <summary>
        ///     Extracts a JSON array of strings. JavaScriptSerializer materializes JSON arrays as
        ///     object[] (or ArrayList) when the target is object, so handle both and stringify each
        ///     element. Returns an empty list for a missing or non-array value, never null.
        /// </summary>
        public static List<string> GetStringList(Dictionary<string, object> o, string key)
        {
            var result = new List<string>();

            object v;
            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return result;

            var enumerable = v as System.Collections.IEnumerable;

            if (enumerable == null || v is string)
                return result;

            foreach (var item in enumerable)
            {
                if (item == null)
                    continue;

                result.Add(item as string ?? Convert.ToString(item, CultureInfo.InvariantCulture));
            }

            return result;
        }

        /// <summary>
        ///     Extracts a JSON array of OBJECTS, as a list of dictionaries.
        ///
        ///     `JavaScriptSerializer` already materializes a nested object as another
        ///     `Dictionary&lt;string, object&gt;` when the target is `object`, so this needs no
        ///     parser work -- only the same defensive walk `GetStringList` does. Anything in the
        ///     array that is not an object is skipped rather than failing the whole field: a
        ///     malformed row in an oracle's dialogue should cost that row, not the NPC.
        ///
        ///     Returns an empty list for a missing or non-array value, never null.
        /// </summary>
        public static List<Dictionary<string, object>> GetObjectList(
            Dictionary<string, object> o, string key)
        {
            var result = new List<Dictionary<string, object>>();

            object v;
            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return result;

            var enumerable = v as System.Collections.IEnumerable;

            if (enumerable == null || v is string)
                return result;

            foreach (var item in enumerable)
            {
                var row = item as Dictionary<string, object>;

                if (row != null)
                    result.Add(row);
            }

            return result;
        }

        public static int GetInt(Dictionary<string, object> o, string key, int fallback)
        {
            object v;

            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return fallback;

            try
            {
                return Convert.ToInt32(v, CultureInfo.InvariantCulture);
            }
            catch
            {
                return fallback;
            }
        }

        /// <summary>
        ///     Epoch milliseconds and lease durations do not fit an int, and JavaScriptSerializer
        ///     hands a large JSON number back as a long or a decimal depending on its magnitude, so
        ///     the conversion is done rather than the cast attempted.
        /// </summary>
        public static long GetLong(Dictionary<string, object> o, string key, long fallback)
        {
            object v;

            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return fallback;

            try
            {
                return Convert.ToInt64(v, CultureInfo.InvariantCulture);
            }
            catch
            {
                return fallback;
            }
        }

        /// <summary>
        ///     A lease VALUE arrives as text on the wire whatever its declared type (see
        ///     BridgeLeases), so this exists for the numbers that are genuinely numbers - a radius,
        ///     a weight. InvariantCulture throughout: a shard running under a comma-decimal locale
        ///     must read the same bytes the same way as one that is not.
        /// </summary>
        public static double GetDouble(Dictionary<string, object> o, string key, double fallback)
        {
            object v;

            if (o == null || !o.TryGetValue(key, out v) || v == null)
                return fallback;

            try
            {
                return Convert.ToDouble(v, CultureInfo.InvariantCulture);
            }
            catch
            {
                return fallback;
            }
        }
    }
}