feat: implement semantic search, knowledge unit extraction, and visualization components

src/NexusReader.Domain/Entities/KnowledgeUnit.cs

@@ -0,0 +1,41 @@
+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)
+
+    [Required]
+    [MaxLength(128)]
+    public string SourceId { get; set; } = string.Empty;
+
+    [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;
+
+    [Column(TypeName = "vector(768)")] // Default for text-embedding-004
+    public float[]? Vector { get; set; }
+
+    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>();
+}

src/NexusReader.Domain/Entities/KnowledgeUnitLink.cs

@@ -0,0 +1,28 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace NexusReader.Domain.Entities;
+
+public class KnowledgeUnitLink
+{
+    [Key]
+    public int Id { get; set; }
+
+    [Required]
+    [MaxLength(128)]
+    public string SourceUnitId { get; set; } = string.Empty;
+
+    [Required]
+    [MaxLength(128)]
+    public string TargetUnitId { get; set; } = string.Empty;
+
+    [Required]
+    [MaxLength(50)]
+    public string RelationType { get; set; } = "References"; // e.g., "Next", "Defines", "Contains"
+
+    [ForeignKey(nameof(SourceUnitId))]
+    public KnowledgeUnit SourceUnit { get; set; } = null!;
+
+    [ForeignKey(nameof(TargetUnitId))]
+    public KnowledgeUnit TargetUnit { get; set; } = null!;
+}

src/NexusReader.Domain/Entities/SemanticKnowledgeCache.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 
 namespace NexusReader.Domain.Entities;
 
@@ -11,6 +12,9 @@ public class SemanticKnowledgeCache
     [Required]
     public string JsonData { get; set; } = string.Empty;
 
+    [Required]
+    public string OriginalText { get; set; } = string.Empty;
+
     [Required]
     [MaxLength(50)]
     public string ModelId { get; set; } = "gemini-1.5-flash";
@@ -19,5 +23,12 @@ public class SemanticKnowledgeCache
     [MaxLength(10)]
     public string PromptVersion { get; set; } = "1.0";
 
+    [Required]
+    [MaxLength(128)]
+    public string TenantId { get; set; } = string.Empty;
+
+    [Column(TypeName = "vector(1536)")] // text-embedding-004 has 768 or 1536 dims, assuming 1536 for high-fidelity
+    public float[]? Vector { get; set; }
+
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 }

src/NexusReader.Domain/Enums/KnowledgeUnitType.cs

@@ -0,0 +1,12 @@
+namespace NexusReader.Domain.Enums;
+
+public enum KnowledgeUnitType
+{
+    Section,
+    Table,
+    Definition,
+    ProcedureStep,
+    PolicyRule,
+    KeyConcept,
+    Snippet
+}