using System.Diagnostics.CodeAnalysis;
using System.Text.RegularExpressions;

using MultiversalDiplomacy.Orders;

namespace MultiversalDiplomacy.Model;

/// <summary>
/// This class defines the regular expressions that are used to build up larger expressions for matching orders
/// and other script inputs. It also provides helper functions to extract the captured order elements as tuples,
/// which function as the structured intermediate representation between raw user input and full Order objects.
/// </summary>
public class OrderRegex(World world)
{
    public const string Type = "(A|F|Army|Fleet)";

    public const string Timeline = "([A-Za-z]+)";

    public const string Turn = "([0-9]+)";

    public const string SlashLocation = "(?:/([A-Za-z]+))";

    public const string ParenLocation = "(?:\\(([A-Za-z ]+)\\))";

    public string FullLocation => $"(?:{Timeline}-)?{world.Map.ProvinceRegex}(?:{SlashLocation}|{ParenLocation})?(?:@{Turn})?";

    public string UnitSpec => $"(?:{Type} )?{FullLocation}";

    public const string HoldVerb = "(h|hold|holds)";

    public const string MoveVerb = "(-|(?:->)|(?:=>)|(?:attack(?:s)?)|(?:move(?:s)?(?: to)?))";

    public const string SupportVerb = "(s|support|supports)";

    public const string ViaConvoy = "(convoy|via convoy|by convoy)";

    public Regex Hold => new(
        $"^{UnitSpec} {HoldVerb}$",
        RegexOptions.IgnoreCase);

    public static (
        string type,
        string timeline,
        string province,
        string location,
        string turn,
        string holdVerb)
        ParseHold(Match match) => (
            match.Groups[1].Value,
            match.Groups[2].Value,
            match.Groups[3].Value,
            match.Groups[4].Length > 0
                ? match.Groups[4].Value
                : match.Groups[5].Value,
            match.Groups[6].Value,
            match.Groups[7].Value);

    public Regex Move => new(
        $"^{UnitSpec} {MoveVerb} {FullLocation}(?: {ViaConvoy})?$",
        RegexOptions.IgnoreCase);

    public static (
        string type,
        string timeline,
        string province,
        string location,
        string turn,
        string moveVerb,
        string destTimeline,
        string destProvince,
        string destLocation,
        string destTurn,
        string viaConvoy)
        ParseMove(Match match) => (
            match.Groups[1].Value,
            match.Groups[2].Value,
            match.Groups[3].Value,
            match.Groups[4].Length > 0
                ? match.Groups[4].Value
                : match.Groups[5].Value,
            match.Groups[6].Value,
            match.Groups[7].Value,
            match.Groups[8].Value,
            match.Groups[9].Value,
            match.Groups[10].Length > 0
                ? match.Groups[10].Value
                : match.Groups[11].Value,
            match.Groups[12].Value,
            match.Groups[13].Value);

    public Regex SupportHold => new(
        $"^{UnitSpec} {SupportVerb} {UnitSpec}$",
        RegexOptions.IgnoreCase);

    public static (
        string type,
        string timeline,
        string province,
        string location,
        string turn,
        string supportVerb,
        string targetType,
        string targetTimeline,
        string targetProvince,
        string targetLocation,
        string targetTurn)
        ParseSupportHold(Match match) => (
            match.Groups[1].Value,
            match.Groups[2].Value,
            match.Groups[3].Value,
            match.Groups[4].Length > 0
                ? match.Groups[4].Value
                : match.Groups[5].Value,
            match.Groups[6].Value,
            match.Groups[7].Value,
            match.Groups[8].Value,
            match.Groups[9].Value,
            match.Groups[10].Value,
            match.Groups[11].Length > 0
                ? match.Groups[11].Value
                : match.Groups[12].Value,
            match.Groups[13].Value);

    public static bool TryParseUnit(World world, string unitSpec, [NotNullWhen(true)] out Unit? newUnit)
    {
        newUnit = null;

        Regex reUnit = new(
            $"^{world.Map.PowerRegex} {Type} {world.Map.ProvinceRegex}(?:{SlashLocation}|{ParenLocation})?$");
        Match match = reUnit.Match(unitSpec);
        if (!match.Success) {
            Console.WriteLine($"Could not match unit spec \"{unitSpec}\"");
            return false;
        }

        string power = world.Map.Powers.First(p => p.EqualsAnyCase(match.Groups[1].Value));

        string typeName = Enum.GetNames<UnitType>().First(name => name.StartsWithAnyCase(match.Groups[2].Value));
        UnitType type = Enum.Parse<UnitType>(typeName);

        Province province = world.Map.Provinces.First(prov
            => prov.Name.EqualsAnyCase(match.Groups[3].Value)
            || prov.Abbreviations.Any(abv => abv.EqualsAnyCase(match.Groups[3].Value)));

        string locationName = match.Groups[4].Length > 0 ? match.Groups[4].Value : match.Groups[5].Value;
        Location location = province.Locations.First(loc
            => loc.Name.StartsWithAnyCase(locationName)
            || loc.Abbreviation.StartsWithAnyCase(locationName));

        newUnit = Unit.Build(location.Key, Season.First, power, type);       
        return true;
    }

    public static bool TryParseOrder(World world, string power, string command, out Order? order) {
        order = null;
        OrderRegex re = new(world);
        Match match;
        if ((match = re.Hold.Match(command)).Success) {
            var hold = ParseHold(match);
            Unit unit = world.Units.First(unit
                => world.Map.GetLocation(unit.Location).ProvinceName == hold.province
                && unit.Season.Timeline == (hold.timeline.Length > 0 ? hold.timeline : "a")
                && unit.Season.Turn.ToString() == (hold.turn.Length > 0 ? hold.turn : "0"));
            order = new HoldOrder(power, unit);
            return true;
        } else if ((match = re.Move.Match(command)).Success) {
            var move = ParseMove(match);
            Unit unit = world.Units.First(unit
                => world.Map.GetLocation(unit.Location).ProvinceName == move.province
                && unit.Season.Timeline == (move.timeline.Length > 0 ? move.timeline : "a")
                && unit.Season.Turn.ToString() == (move.turn.Length > 0 ? move.turn : "0"));
            order = new MoveOrder(power, unit, Season.First, "l");
            return true;
        }

        return false;
    }
}