initial commit

backend/Infrastructure/Data/Configurations/BaseEntityConfiguration.cs

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+using Extrudex.Domain.Base;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Extrudex.Infrastructure.Data.Configurations;
+
+/// <summary>
+/// Base configuration for all entities. Sets up common conventions:
+/// - Table names in snake_case
+/// - GUID primary keys stored as PostgreSQL UUID
+/// - Automatic timestamp columns in snake_case
+/// </summary>
+/// <typeparam name="TEntity">The entity type to configure.</typeparam>
+public abstract class BaseEntityConfiguration<TEntity> : IEntityTypeConfiguration<TEntity>
+    where TEntity : BaseEntity
+{
+    public virtual void Configure(EntityTypeBuilder<TEntity> builder)
+    {
+        // Table name in snake_case
+        builder.ToTable(ToSnakeCase(typeof(TEntity).Name));
+
+        // Primary key stored as UUID
+        builder.HasKey(e => e.Id);
+        builder.Property(e => e.Id)
+            .HasColumnName("id")
+            .ValueGeneratedNever();
+
+        // If the entity is auditable, configure the timestamp columns
+        if (typeof(AuditableEntity).IsAssignableFrom(typeof(TEntity)))
+        {
+            ConfigureAuditColumns(builder);
+        }
+    }
+
+    /// <summary>
+    /// Configures audit timestamp columns (created_at, updated_at) for auditable entities.
+    /// Uses string-based property names since the generic type constraint is BaseEntity
+    /// and cannot be cast to AuditableEntity at compile time.
+    /// </summary>
+    private static void ConfigureAuditColumns(EntityTypeBuilder<TEntity> builder)
+    {
+        builder.Property<DateTime>("CreatedAt")
+            .HasColumnName("created_at")
+            .HasDefaultValueSql("now() at time zone 'utc'");
+
+        builder.Property<DateTime>("UpdatedAt")
+            .HasColumnName("updated_at")
+            .HasDefaultValueSql("now() at time zone 'utc'");
+    }
+
+    /// <summary>
+    /// Converts PascalCase or camelCase to snake_case.
+    /// </summary>
+    protected static string ToSnakeCase(string name)
+    {
+        return string.Concat(
+                name.Select((ch, i) =>
+                    i > 0 && char.IsUpper(ch) && (char.IsLower(name[i - 1]) || (i + 1 < name.Length && char.IsLower(name[i + 1])))
+                        ? "_" + ch
+                        : ch.ToString()))
+            .ToLowerInvariant();
+    }
+}