using Microsoft.EntityFrameworkCore;
using Npgsql;
using YarpGateway.Config;
using YarpGateway.Models;

namespace YarpGateway.Data;

public class GatewayDbContext : DbContext
{
    public GatewayDbContext(DbContextOptions<GatewayDbContext> options)
        : base(options)
    {
    }

    public DbSet<GwTenant> Tenants => Set<GwTenant>();
    public DbSet<GwTenantRoute> TenantRoutes => Set<GwTenantRoute>();
    public DbSet<GwServiceInstance> ServiceInstances => Set<GwServiceInstance>();

    public override int SaveChanges(bool acceptAllChangesOnSuccess)
    {
        DetectConfigChanges();
        var result = base.SaveChanges(acceptAllChangesOnSuccess);
        if (_configChangeDetected)
        {
            NotifyConfigChangedSync();
        }
        return result;
    }

    public override async Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default)
    {
        DetectConfigChanges();
        var result = await base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
        if (_configChangeDetected)
        {
            await NotifyConfigChangedAsync(cancellationToken);
        }
        return result;
    }

    private bool _configChangeDetected;

    private void DetectConfigChanges()
    {
        var entries = ChangeTracker.Entries()
            .Where(e => e.State is EntityState.Added or EntityState.Modified or EntityState.Deleted)
            .Where(e => e.Entity is GwTenantRoute or GwServiceInstance or GwTenant);

        _configChangeDetected = entries.Any();
    }

    private bool IsRelationalDatabase()
    {
        try
        {
            return Database.IsRelational();
        }
        catch
        {
            return false;
        }
    }

    private void NotifyConfigChangedSync()
    {
        if (!IsRelationalDatabase()) return;
        
        var connectionString = Database.GetConnectionString();
        if (string.IsNullOrEmpty(connectionString)) return;

        using var connection = new NpgsqlConnection(connectionString);
        connection.Open();
        using var cmd = new NpgsqlCommand($"NOTIFY {ConfigNotifyChannel.GatewayConfigChanged}", connection);
        cmd.ExecuteNonQuery();
    }

    private async Task NotifyConfigChangedAsync(CancellationToken cancellationToken)
    {
        if (!IsRelationalDatabase()) return;
        
        var connectionString = Database.GetConnectionString();
        if (string.IsNullOrEmpty(connectionString)) return;

        await using var connection = new NpgsqlConnection(connectionString);
        await connection.OpenAsync(cancellationToken);
        await using var cmd = new NpgsqlCommand($"NOTIFY {ConfigNotifyChannel.GatewayConfigChanged}", connection);
        await cmd.ExecuteNonQueryAsync(cancellationToken);
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<GwTenant>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.Property(e => e.TenantCode).HasMaxLength(50).IsRequired();
            entity.Property(e => e.TenantName).HasMaxLength(100).IsRequired();
            entity.HasIndex(e => e.TenantCode).IsUnique();
        });

        modelBuilder.Entity<GwTenantRoute>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.Property(e => e.TenantCode).HasMaxLength(50);
            entity.Property(e => e.ServiceName).HasMaxLength(100).IsRequired();
            entity.Property(e => e.ClusterId).HasMaxLength(100).IsRequired();
            entity.Property(e => e.PathPattern).HasMaxLength(200).IsRequired();
            entity.HasIndex(e => e.TenantCode);
            entity.HasIndex(e => e.ServiceName);
            entity.HasIndex(e => e.ClusterId);
            entity.HasIndex(e => new { e.ServiceName, e.IsGlobal, e.Status });
        });

        modelBuilder.Entity<GwServiceInstance>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.Property(e => e.ClusterId).HasMaxLength(100).IsRequired();
            entity.Property(e => e.DestinationId).HasMaxLength(100).IsRequired();
            entity.Property(e => e.Address).HasMaxLength(200).IsRequired();
            entity.HasIndex(e => new { e.ClusterId, e.DestinationId }).IsUnique();
            entity.HasIndex(e => e.Health);
        });

        base.OnModelCreating(modelBuilder);
    }
}