using System.Text.Json;
using System.Text.Json.Serialization;

namespace MultiversalDiplomacy.Model;

/// <summary>
/// The global game state.
/// </summary>
public class World
{
    public static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
    };

    /// <summary>
    /// The map variant of the game.
    /// </summary>
    [JsonIgnore]
    public Map Map { get; }

    /// <summary>
    /// The map variant of the game.
    /// </summary>
    /// <remarks>
    /// While this is serialized to JSON, deserialization uses it to populate <see cref="Map"/>
    /// </remarks>
    public MapType MapType => this.Map.Type;

    /// <summary>
    /// The game map.
    /// </summary>
    [JsonIgnore]
    public IReadOnlyCollection<Province> Provinces => this.Map.Provinces;

    /// <summary>
    /// The game powers.
    /// </summary>
    [JsonIgnore]
    public IReadOnlyCollection<string> Powers => this.Map.Powers;

    /// <summary>
    /// All units in the multiverse.
    /// </summary>
    public List<Unit> Units { get; }

    /// <summary>
    /// All retreating units in the multiverse.
    /// </summary>
    public List<RetreatingUnit> RetreatingUnits { get; }

    /// <summary>
    /// Orders given to units in each season.
    /// </summary>
    public Dictionary<string, OrderHistory> OrderHistory { get; }

    /// <summary>
    /// The shared timeline number generator.
    /// </summary>
    public Timelines Timelines { get; }

    /// <summary>
    /// Immutable game options.
    /// </summary>
    public Options Options { get; }

    [JsonConstructor]
    public World(
        MapType mapType,
        List<Unit> units,
        List<RetreatingUnit> retreatingUnits,
        Dictionary<string, OrderHistory> orderHistory,
        Timelines timelines,
        Options options)
    {
        this.Map = Map.FromType(mapType);
        this.Units = units;
        this.RetreatingUnits = retreatingUnits;
        this.OrderHistory = orderHistory;
        this.Timelines = timelines;
        this.Options = options;

    }

    /// <summary>
    /// Create a new World, providing all state data.
    /// </summary>
    private World(
        Map map,
        List<Unit> units,
        List<RetreatingUnit> retreatingUnits,
        Dictionary<string, OrderHistory> orderHistory,
        Timelines timelines,
        Options options)
    {
        this.Map = map;
        this.Units = units;
        this.RetreatingUnits = retreatingUnits;
        this.OrderHistory = orderHistory;
        this.Timelines = timelines;
        this.Options = options;
    }

    /// <summary>
    /// Create a new World from a previous one, replacing some state data.
    /// </summary>
    private World(
        World previous,
        List<Unit>? units = null,
        List<RetreatingUnit>? retreatingUnits = null,
        Dictionary<string, OrderHistory>? orderHistory = null,
        Timelines? timelines = null,
        Options? options = null)
        : this(
            previous.Map,
            units ?? previous.Units,
            retreatingUnits ?? previous.RetreatingUnits,
            orderHistory ?? previous.OrderHistory,
            timelines ?? previous.Timelines,
            options ?? previous.Options)
    {
    }

    /// <summary>
    /// Create a new world with specified provinces and powers and an initial season.
    /// </summary>
    public static World WithMap(Map map)
    {
        return new World(
            map,
            new([]),
            new([]),
            new(new Dictionary<string, OrderHistory>()),
            Timelines.Create(),
            new Options());
    }

    /// <summary>
    /// Create a new world with the standard Diplomacy provinces and powers.
    /// </summary>
    public static World WithStandardMap()
        => WithMap(Map.Classical);

    public World Update(
        IEnumerable<Unit>? units = null,
        IEnumerable<RetreatingUnit>? retreats = null,
        IEnumerable<KeyValuePair<string, OrderHistory>>? orders = null,
        Timelines? timelines = null)
        => new(
            previous: this,
            units: units == null
                ? this.Units
                : new(units.ToList()),
            retreatingUnits: retreats == null
                ? this.RetreatingUnits
                : new(retreats.ToList()),
            orderHistory: orders == null
                ? this.OrderHistory
                : new(orders.ToDictionary(kvp => kvp.Key, kvp => kvp.Value)),
            timelines: timelines ?? this.Timelines);

    /// <summary>
    /// Create a new world with new units created from unit specs. Units specs are in the format
    /// "<power> <A/F> <province> [<coast>]". If the province or coast name has a space in it, the
    /// abbreviation should be used. Unit specs always describe units in the root season.
    /// </summary>
    public World AddUnits(params string[] unitSpecs)
    {
        IEnumerable<Unit> units = unitSpecs.Select(spec =>
        {
            string[] splits = spec.Split(' ', 4);
            string power = Map.GetPower(splits[0]);
            UnitType type = splits[1] switch
            {
                "A" => UnitType.Army,
                "F" => UnitType.Fleet,
                _ => throw new ApplicationException($"Unknown unit type {splits[1]}")
            };
            Location location = type == UnitType.Army
                ? Map.GetLand(splits[2])
                : splits.Length == 3
                    ? Map.GetWater(splits[2])
                    : Map.GetWater(splits[2], splits[3]);
            Unit unit = Unit.Build(location.Key, new("a0"), power, type);
            return unit;
        });
        return this.Update(units: units);
    }

    /// <summary>
    /// Create a new world with standard Diplomacy initial unit placements.
    /// </summary>
    public World AddStandardUnits()
    {
        return this.AddUnits(
            "Austria A Bud",
            "Austria A Vir",
            "Austria F Tri",
            "England A Lvp",
            "England F Edi",
            "England F Lon",
            "France A Mar",
            "France A Par",
            "France F Bre",
            "Germany A Ber",
            "Germany A Mun",
            "Germany F Kie",
            "Italy A Rom",
            "Italy A Ven",
            "Italy F Nap",
            "Russia A Mos",
            "Russia A War",
            "Russia F Sev",
            "Russia F Stp wc",
            "Turkey A Con",
            "Turkey A Smy",
            "Turkey F Ank"
        );
    }

    /// <summary>
    /// A standard Diplomacy game setup.
    /// </summary>
    public static World Standard => WithStandardMap().AddStandardUnits();

    /// <summary>
    /// Returns a unit in a province. Throws if there are duplicate units.
    /// </summary>
    public Unit GetUnitAt(string provinceName, Season? season = null)
    {
        Province province = Map.GetProvince(provinceName);
        season ??= new("a0");
        Unit? foundUnit = this.Units.SingleOrDefault(
            u => Map.GetLocation(u!).Province == province && u!.Season == season,
            null)
            ?? throw new KeyNotFoundException($"Unit at {province} at {season} not found");
        return foundUnit;
    }

    public Unit GetUnitByKey(string designation)
        => Units.SingleOrDefault(u => u!.Key == designation, null)
        ?? throw new KeyNotFoundException($"Unit {designation} not found");
}