using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using Volo.Abp.Data;
using Volo.Abp.DependencyInjection;
using Volo.Abp.MultiTenancy;
using Volo.Abp.TenantManagement;

namespace ApiA.Data
{
    public class ApiADbMigrationService : ITransientDependency
    {
        public ILogger<ApiADbMigrationService> Logger { get; set; }

        private readonly IDataSeeder _dataSeeder;
        private readonly IEnumerable<IApiADbSchemaMigrator> _dbSchemaMigrators;
        private readonly ITenantRepository _tenantRepository;
        private readonly ICurrentTenant _currentTenant;

        public ApiADbMigrationService(
            IDataSeeder dataSeeder,
            IEnumerable<IApiADbSchemaMigrator> dbSchemaMigrators,
            ITenantRepository tenantRepository,
            ICurrentTenant currentTenant)
        {
            _dataSeeder = dataSeeder;
            _dbSchemaMigrators = dbSchemaMigrators;
            _tenantRepository = tenantRepository;
            _currentTenant = currentTenant;

            Logger = NullLogger<ApiADbMigrationService>.Instance;
        }

        public async Task MigrateAsync()
        {
            Logger.LogInformation("Started database migrations...");

            await MigrateDatabaseSchemaAsync();
            await SeedDataAsync();

            Logger.LogInformation($"Successfully completed host database migrations.");

            var tenants = await _tenantRepository.GetListAsync(includeDetails: true);

            var migratedDatabaseSchemas = new HashSet<string>();
            foreach (var tenant in tenants)
            {
                if (!tenant.ConnectionStrings.Any())
                {
                    continue;
                }

                using (_currentTenant.Change(tenant.Id))
                {
                    var tenantConnectionStrings = tenant.ConnectionStrings
                        .Select(x => x.Value)
                        .ToList();

                    if (!migratedDatabaseSchemas.IsSupersetOf(tenantConnectionStrings))
                    {
                        await MigrateDatabaseSchemaAsync(tenant);

                        migratedDatabaseSchemas.AddIfNotContains(tenantConnectionStrings);
                    }

                    await SeedDataAsync(tenant);
                }

                Logger.LogInformation($"Successfully completed {tenant.Name} tenant database migrations.");
            }

            Logger.LogInformation("Successfully completed database migrations.");
        }

        private async Task MigrateDatabaseSchemaAsync(Tenant tenant = null)
        {
            Logger.LogInformation(
                $"Migrating schema for {(tenant == null ? "host" : tenant.Name + " tenant")} database...");

            foreach (var migrator in _dbSchemaMigrators)
            {
                await migrator.MigrateAsync();
            }
        }

        private async Task SeedDataAsync(Tenant tenant = null)
        {
            Logger.LogInformation($"Executing {(tenant == null ? "host" : tenant.Name + " tenant")} database seed...");

            await _dataSeeder.SeedAsync(tenant?.Id);
        }
    }
}