using System.Diagnostics.CodeAnalysis;

using MultiversalDiplomacy.Model;

namespace MultiversalDiplomacy.Script;

/// <summary>
/// A script handler for modifying a game before it begins.
/// </summary>
public class SetupScriptHandler(World world, bool strict = false) : IScriptHandler
{
    public string Prompt => "5dp> ";

    public World World { get; private set; } = world;

    /// <summary>
    /// Whether unsuccessful commands should terminate the script.
    /// </summary>
    public bool Strict { get; } = strict;

    public IScriptHandler? HandleInput(string input)
    {
        var args = input.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        if (args.Length == 0)
        {
            return this;
        }

        var command = args[0];
        switch (command)
        {
            case "help":
            case "?":
                Console.WriteLine("commands:");
                Console.WriteLine("  begin: complete setup and start the game");
                Console.WriteLine("  list <type>: list things in a game category");
                Console.WriteLine("  option <name> <value>: set a game option");
                Console.WriteLine("  unit <power> <type> <province> [location]: add a unit to the game");
                Console.WriteLine("       <province> may be \"province/location\"");
                break;

            case "begin":
                return null; // TODO

            case "list" when args.Length == 1:
                Console.WriteLine("usage:");
                Console.WriteLine("  list powers: the powers in the game");
                Console.WriteLine("  list units: units created so far");
                break;

            case "list" when args[1] == "powers":
                Console.WriteLine("Powers:");
                foreach (string powerName in World.Powers)
                {
                    Console.WriteLine($"  {powerName}");
                }
                break;

            case "list" when args[1] == "units":
                Console.WriteLine("Units:");
                foreach (Unit unit in World.Units)
                {
                    Console.WriteLine($"  {unit}");
                }
                break;

            case "option" when args.Length < 3:
                throw new NotImplementedException();

            case "unit" when args.Length < 4:
                Console.WriteLine("usage: unit [power] [type] [province] <location>");
                break;

            case "unit":
                string power = args[1];
                string type = args[2];
                string province = args[3];
                string? location = args.Length >= 5 ? args[4] : null;
                if (ParseUnit(power, type, province, location, out Unit? newUnit)) {
                    World = World.Update(units: World.Units.Append(newUnit));
                    Console.WriteLine($"Created {newUnit}");
                } else if (Strict) {
                    return null;
                }
                break;

            default:
                // noop on comments that begin with #
                if (command.StartsWith('#')) break;
                Console.WriteLine($"Unrecognized command: {command}");
                if (Strict) return null;
                break;
        }

        return this;
    }

    private bool ParseUnit(
        string powerArg,
        string typeArg,
        string provinceArg,
        string? locationArg,
        [NotNullWhen(true)] out Unit? newUnit)
    {
        newUnit = null;

        // Parse the power name by substring matching.
        var matchingPowers = World.Powers.Where(p => p.StartsWithAnyCase(powerArg));
        if (!matchingPowers.Any())
        {
            Console.WriteLine($"No power named \"{powerArg}\"");
            return false;
        }
        if (matchingPowers.Count() > 1)
        {
            Console.WriteLine($"Ambiguous power \"{powerArg}\" between {string.Join(", ", matchingPowers)}");
            return false;
        }
        string power = matchingPowers.First();

        // Parse the unit type by substring matching.
        var matchingTypes = Enum.GetNames<UnitType>().Where(t => t.StartsWithAnyCase(typeArg));
        if (!matchingTypes.Any())
        {
            Console.WriteLine($"No unit type \"{typeArg}\"");
            return false;
        }
        if (matchingTypes.Count() > 1)
        {
            Console.WriteLine($"Ambiguous unit type \"{typeArg}\" between {string.Join(", ", matchingTypes)}");
            return false;
        }
        UnitType type = Enum.Parse<UnitType>(matchingTypes.First());

        // Parse the province by matching the province name or one of its abbreviations,
        // allowing location specifications separated by a forward slash, e.g. spa/nc.
        if (provinceArg.Contains('/')) {
            var split = provinceArg.Split('/', 2);
            locationArg ??= split[1];
            provinceArg = split[0];
        }
        var matchingProvs = World.Provinces.Where(pr
            => pr.Abbreviations.Any(abv => abv.EqualsAnyCase(provinceArg))
            || pr.Name.EqualsAnyCase(provinceArg));
        if (!matchingProvs.Any())
        {
            Console.WriteLine($"No province matches \"{provinceArg}\"");
            return false;
        }
        if (matchingProvs.Count() > 1)
        {
            Console.WriteLine($"Ambiguous province \"{provinceArg}\" between {string.Join(", ", matchingProvs)}");
            return false;
        }
        Province province = matchingProvs.First();
        Location location;
        locationArg ??=  type == UnitType.Army ? "land" : "water";
        var matchingLocs = locationArg is null
            ? province.Locations.Where(loc
                => type == UnitType.Army && loc.Type == LocationType.Land
                || type == UnitType.Fleet && loc.Type == LocationType.Water)
            : province.Locations.Where(loc
                => loc.Name.EqualsAnyCase(locationArg)
                || loc.Abbreviation.EqualsAnyCase(locationArg));
        if (!matchingLocs.Any()) {
            Console.WriteLine($"Province {province.Name} has no {locationArg} location");
            return false;
        }
        location = matchingLocs.First();

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