territory-autobattler/microservices/LocationsApi/Services/UnitTrainingService.cs

using LocationsApi.Models;
using MongoDB.Driver;

namespace LocationsApi.Services;

public class UnitTrainingService
{
    private const string ScoutUnitType = "Scout";

    private readonly IMongoCollection<UnitTraining> _training;
    private readonly ResourceService _resources;
    private readonly GameSettingsService _settings;
    private readonly int _scoutGoldCost;
    private readonly int _defaultScoutTrainingSeconds;

    public UnitTrainingService(IConfiguration cfg, ResourceService resources, GameSettingsService settings)
    {
        var connectionString = cfg["MongoDB:ConnectionString"] ?? "mongodb://127.0.0.1:27017";
        var databaseName = cfg["MongoDB:DatabaseName"] ?? "territory-autobattler";
        var client = new MongoClient(connectionString);
        var database = client.GetDatabase(databaseName);
        _training = database.GetCollection<UnitTraining>("UnitTraining");
        _resources = resources;
        _settings = settings;
        _scoutGoldCost = int.TryParse(cfg["Units:ScoutGoldCost"], out var scoutGoldCost) ? Math.Max(0, scoutGoldCost) : 50;
        _defaultScoutTrainingSeconds = int.TryParse(cfg["Units:ScoutTrainingSeconds"], out var scoutTrainingSeconds)
            ? Math.Max(1, scoutTrainingSeconds)
            : 60;

        _training.Indexes.CreateOne(new CreateIndexModel<UnitTraining>(
            Builders<UnitTraining>.IndexKeys.Ascending(x => x.Username).Ascending(x => x.Status)));
    }

    public async Task<PlayerUnitsResponse> GetMineAsync(string username)
    {
        await CompleteFinishedTrainingAsync(username);

        var all = await _training.Find(x => x.Username == username).ToListAsync();
        var completedScouts = all.Count(x => x.UnitType == ScoutUnitType && x.Status == "Completed");
        var activeTraining = all
            .Where(x => x.Status == "Training")
            .OrderBy(x => x.CompletesAtUtc)
            .Select(UnitTrainingResponse.FromTraining)
            .ToList();

        return new PlayerUnitsResponse
        {
            CompletedScouts = completedScouts,
            Training = activeTraining
        };
    }

    public async Task<UnitTraining?> TrainAsync(string username, string unitType)
    {
        if (!string.Equals(unitType, ScoutUnitType, StringComparison.OrdinalIgnoreCase))
        {
            throw new ArgumentException("Unsupported unit type.", nameof(unitType));
        }

        var spent = await _resources.TrySpendGoldAsync(username, _scoutGoldCost);
        if (!spent)
        {
            return null;
        }

        var now = DateTime.UtcNow;
        var scoutTrainingSeconds = await _settings.GetIntAsync(GameSettingsService.ScoutTrainingSeconds, _defaultScoutTrainingSeconds);
        var training = new UnitTraining
        {
            Username = username,
            UnitType = ScoutUnitType,
            GoldCost = _scoutGoldCost,
            Status = "Training",
            StartedAtUtc = now,
            CompletesAtUtc = now.AddSeconds(scoutTrainingSeconds),
            CreatedAtUtc = now,
            UpdatedAtUtc = now
        };

        await _training.InsertOneAsync(training);
        return training;
    }

    public async Task<bool> TryConsumeCompletedScoutAsync(string username)
    {
        await CompleteFinishedTrainingAsync(username);

        var now = DateTime.UtcNow;
        var update = Builders<UnitTraining>.Update
            .Set(x => x.Status, "Consumed")
            .Set(x => x.UpdatedAtUtc, now);

        var consumed = await _training.FindOneAndUpdateAsync(
            x => x.Username == username && x.UnitType == ScoutUnitType && x.Status == "Completed",
            update,
            new FindOneAndUpdateOptions<UnitTraining>
            {
                Sort = Builders<UnitTraining>.Sort.Ascending(x => x.CompletedAtUtc).Ascending(x => x.CreatedAtUtc),
                ReturnDocument = ReturnDocument.After
            });

        return consumed is not null;
    }

    public async Task<bool> HasCompletedScoutAsync(string username)
    {
        await CompleteFinishedTrainingAsync(username);
        return await _training.Find(x => x.Username == username && x.UnitType == ScoutUnitType && x.Status == "Completed").AnyAsync();
    }

    private async Task CompleteFinishedTrainingAsync(string username)
    {
        var now = DateTime.UtcNow;
        var update = Builders<UnitTraining>.Update
            .Set(x => x.Status, "Completed")
            .Set(x => x.CompletedAtUtc, now)
            .Set(x => x.UpdatedAtUtc, now);

        await _training.UpdateManyAsync(
            x => x.Username == username && x.Status == "Training" && x.CompletesAtUtc <= now,
            update);
    }
}