using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using NexusReader.Domain.Enums;

namespace NexusReader.Domain.Entities;

public class KnowledgeUnit
{
    [Key]
    [MaxLength(128)]
    public string Id { get; set; } = string.Empty; // Hash(Source + Content + Version)

    public Guid? EbookId { get; set; }
 
     [ForeignKey(nameof(EbookId))]
    public virtual Ebook? Ebook { get; set; }

    [Required]
    [MaxLength(50)]
    public string Version { get; set; } = "1.0";

    [Required]
    public KnowledgeUnitType Type { get; set; }

    [Required]
    public string Content { get; set; } = string.Empty;

    public string? MetadataJson { get; set; } // e.g. { "page": 1, "path": "Chapter 1 > Intro" }

    [Required]
    [MaxLength(128)]
    public string TenantId { get; set; } = string.Empty;

    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;

    // Relationships
    public ICollection<KnowledgeUnitLink> OutgoingLinks { get; set; } = new List<KnowledgeUnitLink>();
    public ICollection<KnowledgeUnitLink> IncomingLinks { get; set; } = new List<KnowledgeUnitLink>();
}