using LocationsApi.Models;
using MongoDB.Driver;

namespace LocationsApi.Services;

public class UnitTrainingService
{
    private const string ScoutUnitType = "Scout";
    private const string ArcherUnitType = "Archer";
    private const string PeasantUnitType = "Peasant";

    private readonly IMongoCollection<UnitTraining> _training;
    private readonly IMongoCollection<UnitInstance> _units;
    private readonly IMongoCollection<Location> _locations;
    private readonly ResourceService _resources;
    private readonly GameSettingsService _settings;
    private readonly int _scoutGoldCost;
    private readonly int _archerGoldCost;
    private readonly int _archerWoodCost;
    private readonly int _peasantGoldCost;
    private readonly int _defaultScoutTrainingSeconds;
    private readonly int _defaultArcherTrainingSeconds;
    private readonly int _defaultPeasantTrainingSeconds;
    private readonly int _unitMovementPerTick;
    private readonly int _visibilityDepth;

    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");
        _units = database.GetCollection<UnitInstance>("Units");
        _locations = database.GetCollection<Location>("Locations");
        _resources = resources;
        _settings = settings;
        _scoutGoldCost = int.TryParse(cfg["Units:ScoutGoldCost"], out var scoutGoldCost) ? Math.Max(0, scoutGoldCost) : 50;
        _archerGoldCost = int.TryParse(cfg["Units:ArcherGoldCost"], out var archerGoldCost) ? Math.Max(0, archerGoldCost) : 100;
        _archerWoodCost = int.TryParse(cfg["Units:ArcherWoodCost"], out var archerWoodCost) ? Math.Max(0, archerWoodCost) : 100;
        _peasantGoldCost = int.TryParse(cfg["Units:PeasantGoldCost"], out var peasantGoldCost) ? Math.Max(0, peasantGoldCost) : 25;
        _defaultScoutTrainingSeconds = int.TryParse(cfg["Units:ScoutTrainingSeconds"], out var scoutTrainingSeconds)
            ? Math.Max(1, scoutTrainingSeconds)
            : 60;
        _defaultArcherTrainingSeconds = int.TryParse(cfg["Units:ArcherTrainingSeconds"], out var archerTrainingSeconds)
            ? Math.Max(1, archerTrainingSeconds)
            : 60;
        _defaultPeasantTrainingSeconds = int.TryParse(cfg["Units:PeasantTrainingSeconds"], out var peasantTrainingSeconds)
            ? Math.Max(1, peasantTrainingSeconds)
            : 60;
        _unitMovementPerTick = int.TryParse(cfg["Units:UnitMovementPerTick"], out var unitMovementPerTick)
            ? Math.Max(1, unitMovementPerTick)
            : 1;
        _visibilityDepth = int.TryParse(cfg["World:VisibilityDepth"], out var visibilityDepth) ? Math.Max(0, visibilityDepth) : 3;

        _training.Indexes.CreateOne(new CreateIndexModel<UnitTraining>(
            Builders<UnitTraining>.IndexKeys.Ascending(x => x.Username).Ascending(x => x.Status)));
        _units.Indexes.CreateOne(new CreateIndexModel<UnitInstance>(
            Builders<UnitInstance>.IndexKeys.Ascending(x => x.Username).Ascending(x => x.UnitType)));
        _units.Indexes.CreateOne(new CreateIndexModel<UnitInstance>(
            Builders<UnitInstance>.IndexKeys.Ascending(x => x.SourceTrainingId),
            new CreateIndexOptions<UnitInstance>
            {
                Unique = true,
                Sparse = true
            }));
    }

    public async Task<PlayerUnitsResponse> GetMineAsync(string username)
    {
        await CompleteFinishedTrainingAsync(username);
        await CompletePendingMovementAsync(username);
        await RefillMovementAsync(username);
        await _training.DeleteManyAsync(x => x.Username == username && x.Status == "Consumed");

        var allTraining = await _training.Find(x => x.Username == username).ToListAsync();
        var allUnits = await _units.Find(x => x.Username == username).ToListAsync();
        var completedScouts = allTraining.Count(x => x.UnitType == ScoutUnitType && x.Status == "Completed");
        var completedArchers = allUnits.Count(x => x.UnitType == ArcherUnitType);
        var completedPeasants = allUnits.Count(x => x.UnitType == PeasantUnitType && x.Status == "Idle");
        var activeTraining = allTraining
            .Where(x => x.Status == "Training")
            .OrderBy(x => x.CompletesAtUtc)
            .Select(UnitTrainingResponse.FromTraining)
            .ToList();

        return new PlayerUnitsResponse
        {
            CompletedScouts = completedScouts,
            CompletedArchers = completedArchers,
            CompletedPeasants = completedPeasants,
            Training = activeTraining,
            Units = allUnits
                .OrderBy(x => x.Q)
                .ThenBy(x => x.R)
                .ThenBy(x => x.CreatedAtUtc)
                .Select(UnitInstanceResponse.FromUnit)
                .ToList()
        };
    }

    public async Task<UnitTraining?> TrainAsync(string username, TrainUnitRequest request)
    {
        var normalizedUnitType = NormalizeUnitType(request.UnitType);
        if (normalizedUnitType is null)
        {
            throw new ArgumentException("Unsupported unit type.", nameof(request.UnitType));
        }

        Location? origin = null;
        if (normalizedUnitType == ArcherUnitType)
        {
            if (request.Q is null || request.R is null)
            {
                throw new InvalidOperationException("Select a completed Barracks to train Archers.");
            }

            origin = await GetBuiltBarracksAsync(username, request.Q.Value, request.R.Value);
            if (origin is null)
            {
                throw new InvalidOperationException("A completed Barracks is required to train Archers.");
            }
        }
        else if (normalizedUnitType == PeasantUnitType)
        {
            origin = await _locations.Find(x => x.OwnerUsername == username && x.Kind == "Home").FirstOrDefaultAsync();
            if (origin is null)
            {
                throw new InvalidOperationException("A town hall is required to train Peasants.");
            }
        }

        var goldCost = normalizedUnitType == ArcherUnitType
            ? await _settings.GetNonNegativeIntAsync(GameSettingsService.ArcherGoldCost, _archerGoldCost)
            : normalizedUnitType == PeasantUnitType
                ? await _settings.GetNonNegativeIntAsync(GameSettingsService.PeasantGoldCost, _peasantGoldCost)
                : await _settings.GetNonNegativeIntAsync(GameSettingsService.ScoutGoldCost, _scoutGoldCost);
        var woodCost = normalizedUnitType == ArcherUnitType
            ? await _settings.GetNonNegativeIntAsync(GameSettingsService.ArcherWoodCost, _archerWoodCost)
            : 0;
        var spent = normalizedUnitType == ArcherUnitType
            ? await _resources.TrySpendResourcesAsync(username, goldCost, woodCost, 0)
            : await _resources.TrySpendGoldAsync(username, goldCost);
        if (!spent)
        {
            return null;
        }

        var now = DateTime.UtcNow;
        var trainingSeconds = normalizedUnitType == ArcherUnitType
            ? await _settings.GetIntAsync(GameSettingsService.ArcherTrainingSeconds, _defaultArcherTrainingSeconds)
            : normalizedUnitType == PeasantUnitType
                ? await _settings.GetIntAsync(GameSettingsService.PeasantTrainingSeconds, _defaultPeasantTrainingSeconds)
            : await _settings.GetIntAsync(GameSettingsService.ScoutTrainingSeconds, _defaultScoutTrainingSeconds);
        var training = new UnitTraining
        {
            Username = username,
            UnitType = normalizedUnitType,
            GoldCost = goldCost,
            WoodCost = woodCost,
            OriginQ = origin?.Q,
            OriginR = origin?.R,
            Status = "Training",
            StartedAtUtc = now,
            CompletesAtUtc = now.AddSeconds(trainingSeconds),
            CreatedAtUtc = now,
            UpdatedAtUtc = now
        };

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

    public async Task<List<UnitInstance>> MoveSquadAsync(string username, MoveUnitSquadRequest request)
    {
        await CompletePendingMovementAsync(username);
        await RefillMovementAsync(username);

        var normalizedUnitType = NormalizeUnitType(request.UnitType);
        if (normalizedUnitType != ArcherUnitType)
        {
            throw new ArgumentException("Only Archer squads can be moved right now.", nameof(request.UnitType));
        }

        if (request.FromQ == request.ToQ && request.FromR == request.ToR)
        {
            throw new InvalidOperationException("Select a different destination tile.");
        }

        if (HexDistance(request.FromQ, request.FromR, request.ToQ, request.ToR) != 1)
        {
            throw new InvalidOperationException("Archers can only move to adjacent tiles.");
        }

        if (!await CanMoveToAsync(username, request.ToQ, request.ToR))
        {
            throw new InvalidOperationException("Archers can only move to visible tiles.");
        }

        var now = DateTime.UtcNow;
        var units = await _units.Find(x =>
                x.Username == username &&
                x.UnitType == ArcherUnitType &&
                x.Status == "Idle" &&
                x.Q == request.FromQ &&
                x.R == request.FromR)
            .ToListAsync();

        if (units.Count == 0)
        {
            return [];
        }

        if (units.Any(x => x.MovementRemaining <= 0))
        {
            throw new InvalidOperationException("That squad has no movement remaining this tick.");
        }

        var movementCompletesAt = now.AddMinutes(1);
        await _units.UpdateManyAsync(
            x => x.Username == username &&
                 x.UnitType == ArcherUnitType &&
                 x.Status == "Idle" &&
                 x.Q == request.FromQ &&
                 x.R == request.FromR,
            Builders<UnitInstance>.Update
                .Set(x => x.Status, "Moving")
                .Inc(x => x.MovementRemaining, -1)
                .Set(x => x.DestinationQ, request.ToQ)
                .Set(x => x.DestinationR, request.ToR)
                .Set(x => x.MovementStartedAtUtc, now)
                .Set(x => x.MovementCompletesAtUtc, movementCompletesAt)
                .Set(x => x.UpdatedAtUtc, now));

        return await _units.Find(x =>
                x.Username == username &&
                x.UnitType == ArcherUnitType &&
                x.Status == "Moving" &&
                x.Q == request.FromQ &&
                x.R == request.FromR &&
                x.DestinationQ == request.ToQ &&
                x.DestinationR == request.ToR)
            .ToListAsync();
    }

    private async Task<Location?> GetBuiltBarracksAsync(string username, int q, int r)
    {
        await CompleteFinishedBuildingsAsync(username);
        return await _locations.Find(x =>
                x.OwnerUsername == username &&
                x.Q == q &&
                x.R == r &&
                x.BuildingType == "Barracks" &&
                (x.BuildingStatus == "Built" || x.BuildingStatus == null || x.BuildingStatus == ""))
            .FirstOrDefaultAsync();
    }

    private async Task CompletePendingMovementAsync(string username)
    {
        var now = DateTime.UtcNow;
        var movementPerTick = await _settings.GetIntAsync(GameSettingsService.UnitMovementPerTick, _unitMovementPerTick);
        var movingUnits = await _units.Find(x =>
                x.Username == username &&
                x.Status == "Moving" &&
                x.MovementCompletesAtUtc != null &&
                x.MovementCompletesAtUtc <= now)
            .ToListAsync();

        foreach (var unit in movingUnits)
        {
            if (unit.DestinationQ is null || unit.DestinationR is null)
            {
                await _units.UpdateOneAsync(
                    x => x.Id == unit.Id,
                    Builders<UnitInstance>.Update
                        .Set(x => x.Status, "Idle")
                        .Set(x => x.MovementPerTick, movementPerTick)
                        .Set(x => x.MovementRemaining, movementPerTick)
                        .Unset(x => x.MovementStartedAtUtc)
                        .Unset(x => x.MovementCompletesAtUtc)
                        .Set(x => x.UpdatedAtUtc, now));
                continue;
            }

            await _units.UpdateOneAsync(
                x => x.Id == unit.Id,
                Builders<UnitInstance>.Update
                    .Set(x => x.Q, unit.DestinationQ.Value)
                    .Set(x => x.R, unit.DestinationR.Value)
                    .Set(x => x.Status, "Idle")
                    .Set(x => x.MovementPerTick, movementPerTick)
                    .Set(x => x.MovementRemaining, movementPerTick)
                    .Set(x => x.LastMovementRefillAtUtc, now)
                    .Unset(x => x.DestinationQ)
                    .Unset(x => x.DestinationR)
                    .Unset(x => x.MovementStartedAtUtc)
                    .Unset(x => x.MovementCompletesAtUtc)
                    .Set(x => x.UpdatedAtUtc, now));

            if (unit.UnitType == ArcherUnitType)
            {
                await ClaimTargetIfEmptyAsync(username, unit.DestinationQ.Value, unit.DestinationR.Value, now);
            }
        }
    }

    private async Task RefillMovementAsync(string username)
    {
        var now = DateTime.UtcNow;
        var movementPerTick = await _settings.GetIntAsync(GameSettingsService.UnitMovementPerTick, _unitMovementPerTick);
        var units = await _units.Find(x => x.Username == username && x.Status != "Moving" && x.Status != "MovingToWork").ToListAsync();

        foreach (var unit in units)
        {
            var lastRefill = unit.LastMovementRefillAtUtc.Year < 2000 ? now : unit.LastMovementRefillAtUtc;
            var elapsedTicks = (int)Math.Floor((now - lastRefill).TotalMinutes);
            var movementRemaining = elapsedTicks > 0
                ? movementPerTick
                : Math.Min(unit.MovementRemaining, movementPerTick);
            if (elapsedTicks <= 0 && unit.MovementPerTick == movementPerTick && unit.MovementRemaining == movementRemaining)
            {
                continue;
            }

            var update = Builders<UnitInstance>.Update
                .Set(x => x.MovementPerTick, movementPerTick)
                .Set(x => x.MovementRemaining, movementRemaining)
                .Set(x => x.UpdatedAtUtc, now);
            if (elapsedTicks > 0)
            {
                update = update.Set(x => x.LastMovementRefillAtUtc, lastRefill.AddMinutes(elapsedTicks));
            }

            await _units.UpdateOneAsync(x => x.Id == unit.Id, update);
        }
    }

    private async Task CompleteFinishedBuildingsAsync(string username)
    {
        var now = DateTime.UtcNow;
        var update = Builders<Location>.Update
            .Set(x => x.BuildingStatus, "Built")
            .Set(x => x.BuildingBuiltAtUtc, now)
            .Set(x => x.UpdatedAtUtc, now);

        await _locations.UpdateManyAsync(
            x => x.OwnerUsername == username &&
                 x.BuildingType == "Barracks" &&
                 x.BuildingStatus == "Building" &&
                 x.BuildingCompletesAtUtc <= now,
            update);
    }

    private async Task<bool> CanMoveToAsync(string username, int q, int r)
    {
        var ownedLocations = await _locations.Find(x => x.OwnerUsername == username).ToListAsync();
        if (ownedLocations.Any(owned => HexDistance(owned.Q, owned.R, q, r) <= _visibilityDepth))
        {
            return true;
        }

        var playerUnits = await _units.Find(x => x.Username == username).ToListAsync();
        return playerUnits.Any(unit => HexDistance(unit.Q, unit.R, q, r) <= 1);
    }

    private async Task ClaimTargetIfEmptyAsync(string username, int q, int r, DateTime now)
    {
        var hasOtherUnits = await _units.Find(x => x.Username != username && x.Q == q && x.R == r).AnyAsync();
        var target = await _locations.Find(x => x.Q == q && x.R == r).FirstOrDefaultAsync();
        var hasBuilding = target is not null &&
            (!string.IsNullOrWhiteSpace(target.BuildingType) ||
             string.Equals(target.Kind, "Home", StringComparison.OrdinalIgnoreCase));

        if (hasOtherUnits || hasBuilding)
        {
            return;
        }

        if (target is null)
        {
            var location = new Location
            {
                Q = q,
                R = r,
                Terrain = "Field",
                Kind = "Claimed",
                OwnerUsername = username,
                Level = 1,
                CreatedAtUtc = now,
                UpdatedAtUtc = now
            };

            try
            {
                await _locations.InsertOneAsync(location);
            }
            catch (MongoWriteException)
            {
            }

            return;
        }

        if (string.Equals(target.OwnerUsername, username, StringComparison.OrdinalIgnoreCase))
        {
            return;
        }

        var capturableFilter = Builders<Location>.Filter.And(
            Builders<Location>.Filter.Eq(x => x.Id, target.Id),
            Builders<Location>.Filter.Ne(x => x.Kind, "Home"),
            Builders<Location>.Filter.Or(
                Builders<Location>.Filter.Eq(x => x.BuildingType, null),
                Builders<Location>.Filter.Eq(x => x.BuildingType, "")));

        await _locations.UpdateOneAsync(
            capturableFilter,
            Builders<Location>.Update
                .Set(x => x.OwnerUsername, username)
                .Set(x => x.Kind, "Claimed")
                .Set(x => x.UpdatedAtUtc, now));
    }

    private static int HexDistance(int q1, int r1, int q2, int r2)
    {
        var s1 = -q1 - r1;
        var s2 = -q2 - r2;
        return Math.Max(Math.Max(Math.Abs(q1 - q2), Math.Abs(r1 - r2)), Math.Abs(s1 - s2));
    }

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

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

        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 readyTraining = await _training.Find(x =>
                x.Username == username &&
                x.Status == "Training" &&
                x.CompletesAtUtc <= now)
            .ToListAsync();

        foreach (var training in readyTraining)
        {
            var update = Builders<UnitTraining>.Update
                .Set(x => x.Status, "Completed")
                .Set(x => x.CompletedAtUtc, now)
                .Set(x => x.UpdatedAtUtc, now);

            var completed = await _training.FindOneAndUpdateAsync(
                x => x.Id == training.Id && x.Status == "Training",
                update,
                new FindOneAndUpdateOptions<UnitTraining>
                {
                    ReturnDocument = ReturnDocument.After
                });

            if (completed is null || (completed.UnitType != ArcherUnitType && completed.UnitType != PeasantUnitType))
            {
                continue;
            }

            var movementPerTick = await _settings.GetIntAsync(GameSettingsService.UnitMovementPerTick, _unitMovementPerTick);
            var unit = new UnitInstance
            {
                Username = completed.Username,
                UnitType = completed.UnitType,
                Q = completed.OriginQ ?? 0,
                R = completed.OriginR ?? 0,
                Status = "Idle",
                MovementPerTick = movementPerTick,
                MovementRemaining = movementPerTick,
                LastMovementRefillAtUtc = now,
                SourceTrainingId = completed.Id,
                CreatedAtUtc = now,
                UpdatedAtUtc = now
            };

            try
            {
                await _units.InsertOneAsync(unit);
            }
            catch (MongoWriteException)
            {
            }
        }
    }

    private static string? NormalizeUnitType(string unitType)
    {
        var trimmed = unitType.Trim();
        return trimmed.ToLowerInvariant() switch
        {
            "scout" => ScoutUnitType,
            "archer" => ArcherUnitType,
            "peasant" => PeasantUnitType,
            _ => null
        };
    }
}