using System.Data;
using Azaion.Missions.Database;
using Azaion.Missions.Database.Entities;
using Azaion.Missions.DTOs;

namespace Azaion.Missions.Services;

public class VehicleService(AppDataConnection db)
{
    // B12 (Option A): "exactly one default vehicle" is the user-visible truth.
    // Every code path that sets is_default=true clears existing defaults and
    // assigns the new default inside a Serializable transaction so two
    // concurrent default-set ops cannot leave 0 or 2 defaults. The DB-level
    // partial unique index `ux_vehicles_one_default` (DatabaseMigrator) is the
    // belt-and-braces backstop if a future code path forgets the transaction.
    public async Task<Vehicle> CreateVehicle(CreateVehicleRequest request)
    {
        var vehicle = new Vehicle
        {
            Id = Guid.NewGuid(),
            Type = request.Type,
            Model = request.Model,
            Name = request.Name,
            FuelType = request.FuelType,
            BatteryCapacity = request.BatteryCapacity,
            EngineConsumption = request.EngineConsumption,
            EngineConsumptionIdle = request.EngineConsumptionIdle,
            IsDefault = request.IsDefault
        };

        if (request.IsDefault)
        {
            await using var tx = await db.BeginTransactionAsync(IsolationLevel.Serializable);
            await db.Vehicles.Where(v => v.IsDefault).Set(v => v.IsDefault, false).UpdateAsync();
            await db.InsertAsync(vehicle);
            await tx.CommitAsync();
        }
        else
        {
            await db.InsertAsync(vehicle);
        }

        return vehicle;
    }

    public async Task<Vehicle> UpdateVehicle(Guid id, UpdateVehicleRequest request)
    {
        var vehicle = await db.Vehicles.FirstOrDefaultAsync(v => v.Id == id)
            ?? throw new KeyNotFoundException($"Vehicle {id} not found");

        if (request.Type.HasValue)
            vehicle.Type = request.Type.Value;
        if (request.Model != null)
            vehicle.Model = request.Model;
        if (request.Name != null)
            vehicle.Name = request.Name;
        if (request.FuelType.HasValue)
            vehicle.FuelType = request.FuelType.Value;
        if (request.BatteryCapacity.HasValue)
            vehicle.BatteryCapacity = request.BatteryCapacity.Value;
        if (request.EngineConsumption.HasValue)
            vehicle.EngineConsumption = request.EngineConsumption.Value;
        if (request.EngineConsumptionIdle.HasValue)
            vehicle.EngineConsumptionIdle = request.EngineConsumptionIdle.Value;

        if (request.IsDefault is true)
        {
            await using var tx = await db.BeginTransactionAsync(IsolationLevel.Serializable);
            await db.Vehicles.Where(v => v.IsDefault && v.Id != id).Set(v => v.IsDefault, false).UpdateAsync();
            vehicle.IsDefault = true;
            await db.UpdateAsync(vehicle);
            await tx.CommitAsync();
        }
        else
        {
            if (request.IsDefault is false)
                vehicle.IsDefault = false;
            await db.UpdateAsync(vehicle);
        }

        return vehicle;
    }

    public async Task<Vehicle> GetVehicle(Guid id)
    {
        var vehicle = await db.Vehicles.FirstOrDefaultAsync(v => v.Id == id)
            ?? throw new KeyNotFoundException($"Vehicle {id} not found");
        return vehicle;
    }

    public async Task<List<Vehicle>> GetVehicles(GetVehiclesQuery query)
    {
        var q = db.Vehicles.AsQueryable();

        if (!string.IsNullOrEmpty(query.Name))
            q = q.Where(v => v.Name.ToLower().Contains(query.Name.ToLower()));
        if (query.IsDefault.HasValue)
            q = q.Where(v => v.IsDefault == query.IsDefault.Value);

        return await q.OrderBy(v => v.Name).ToListAsync();
    }

    public async Task DeleteVehicle(Guid id)
    {
        var hasMissions = await db.Missions.AnyAsync(m => m.VehicleId == id);
        if (hasMissions)
            throw new InvalidOperationException($"Vehicle {id} is referenced by missions");

        var vehicle = await db.Vehicles.FirstOrDefaultAsync(v => v.Id == id)
            ?? throw new KeyNotFoundException($"Vehicle {id} not found");

        await db.Vehicles.DeleteAsync(v => v.Id == id);
    }

    public async Task SetDefault(Guid id, SetDefaultRequest request)
    {
        var vehicle = await db.Vehicles.FirstOrDefaultAsync(v => v.Id == id)
            ?? throw new KeyNotFoundException($"Vehicle {id} not found");

        if (request.IsDefault)
        {
            await using var tx = await db.BeginTransactionAsync(IsolationLevel.Serializable);
            await db.Vehicles.Where(v => v.IsDefault && v.Id != id).Set(v => v.IsDefault, false).UpdateAsync();
            vehicle.IsDefault = true;
            await db.UpdateAsync(vehicle);
            await tx.CommitAsync();
        }
        else
        {
            vehicle.IsDefault = false;
            await db.UpdateAsync(vehicle);
        }
    }
}