using AyCode.Core.Extensions;
using AyCode.Core.Serializers.Binaries;
using System.Reflection;
using static AyCode.Core.Tests.Serialization.AcSerializerModels;

namespace AyCode.Core.Tests.Serialization;

/// <summary>
/// Diagnostic tests to help debug serialization issues.
/// </summary>
[TestClass]
public class AcBinarySerializerDiagnosticTests
{
    /// <summary>
    /// Diagnostic test to understand the exact binary structure.
    /// This test outputs the binary bytes to help debug production issues.
    /// </summary>
    [TestMethod]
    public void Diagnostic_StockTaking_BinaryStructure()
    {
        var stockTaking = new TestStockTakingWithInheritance
        {
            Id = 1,
            StartDateTime = new DateTime(2025, 1, 24, 10, 0, 0, DateTimeKind.Utc),
            IsClosed = false,
            Creator = 6,
            Created = new DateTime(2025, 1, 24, 15, 25, 0, DateTimeKind.Utc),
            Modified = new DateTime(2025, 1, 24, 16, 0, 0, DateTimeKind.Utc),
            StockTakingItems = null
        };

        var binary = stockTaking.ToBinary();
        
        var hexDump = string.Join(" ", binary.Select(b => b.ToString("X2")));
        Console.WriteLine($"Binary length: {binary.Length}");
        Console.WriteLine($"Binary hex: {hexDump}");
        
        for (int i = 0; i < binary.Length; i++)
        {
            if (binary[i] == 214)
            {
                Console.WriteLine($"Found 0xD6 at position {i}");
            }
        }

        var result = binary.BinaryTo<TestStockTakingWithInheritance>();
        
        Assert.IsNotNull(result);
        Assert.AreEqual(6, result.Creator);
        Assert.AreEqual(stockTaking.Created.Ticks, result.Created.Ticks);
    }

    /// <summary>
    /// Test with nested list to ensure proper stream positioning.
    /// </summary>
    [TestMethod]
    public void Diagnostic_StockTaking_WithNestedItems()
    {
        var stockTaking = new TestStockTakingWithInheritance
        {
            Id = 1,
            StartDateTime = new DateTime(2025, 1, 24, 10, 0, 0, DateTimeKind.Utc),
            IsClosed = false,
            Creator = 6,
            Created = new DateTime(2025, 1, 24, 15, 25, 0, DateTimeKind.Utc),
            Modified = new DateTime(2025, 1, 24, 16, 0, 0, DateTimeKind.Utc),
            StockTakingItems = new List<TestStockTakingItemWithInheritance>
            {
                new()
                {
                    Id = 10,
                    StockTakingId = 1,
                    ProductId = 100,
                    IsMeasured = true,
                    OriginalStockQuantity = 50,
                    MeasuredStockQuantity = 48,
                    Created = new DateTime(2025, 1, 24, 14, 0, 0, DateTimeKind.Utc),
                    Modified = new DateTime(2025, 1, 24, 14, 30, 0, DateTimeKind.Utc),
                    StockTakingItemPallets = null
                }
            }
        };

        var binary = stockTaking.ToBinary();
        Console.WriteLine($"Binary length with 1 item: {binary.Length}");

        var result = binary.BinaryTo<TestStockTakingWithInheritance>();
        
        Assert.IsNotNull(result);
        Assert.AreEqual(6, result.Creator, "Creator should be 6");
        Assert.AreEqual(stockTaking.Created.Ticks, result.Created.Ticks, 
            $"Created mismatch. Expected: {stockTaking.Created}, Got: {result.Created}");
        Assert.IsNotNull(result.StockTakingItems);
        Assert.AreEqual(1, result.StockTakingItems.Count);
    }

    /// <summary>
    /// CRITICAL TEST: Verify property order is consistent.
    /// This test checks that the reflection-based property order matches
    /// what's expected for serialization/deserialization.
    /// </summary>
    [TestMethod]
    public void Diagnostic_PropertyOrder_InheritanceHierarchy()
    {
        var type = typeof(SimStockTaking);
        var props = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
        
        Console.WriteLine($"Properties of {type.Name} (count: {props.Length}):");
        for (int i = 0; i < props.Length; i++)
        {
            var prop = props[i];
            Console.WriteLine($"  [{i}] {prop.Name} : {prop.PropertyType.Name} (declared in: {prop.DeclaringType?.Name})");
        }
        
        // The exact order may vary by platform!
        // Log it so we can compare server vs client
        Assert.IsTrue(props.Length >= 7, "Should have at least 7 properties");
        
        // Check that all expected properties exist
        var propNames = props.Select(p => p.Name).ToHashSet();
        Assert.IsTrue(propNames.Contains("Id"), "Should have Id");
        Assert.IsTrue(propNames.Contains("StartDateTime"), "Should have StartDateTime");
        Assert.IsTrue(propNames.Contains("IsClosed"), "Should have IsClosed");
        Assert.IsTrue(propNames.Contains("Creator"), "Should have Creator");
        Assert.IsTrue(propNames.Contains("Created"), "Should have Created");
        Assert.IsTrue(propNames.Contains("Modified"), "Should have Modified");
        Assert.IsTrue(propNames.Contains("StockTakingItems"), "Should have StockTakingItems");
    }

    /// <summary>
    /// CRITICAL REGRESSION TEST: Simulates exact production hierarchy.
    /// StockTaking : MgStockTaking&lt;StockTakingItem&gt; : MgEntityBase : BaseEntity
    /// </summary>
    [TestMethod]
    public void Diagnostic_SimStockTaking_RoundTrip()
    {
        var stockTaking = new SimStockTaking
        {
            Id = 1,
            StartDateTime = new DateTime(2025, 1, 24, 10, 0, 0, DateTimeKind.Utc),
            IsClosed = false,
            Creator = 6, // The exact value from production error
            Created = new DateTime(2025, 1, 24, 15, 25, 0, DateTimeKind.Utc),
            Modified = new DateTime(2025, 1, 24, 16, 0, 0, DateTimeKind.Utc),
            StockTakingItems = null // loadRelations = false means no items
        };

        var binary = stockTaking.ToBinary();
        
        // Log the property names in the header
        Console.WriteLine($"Binary length: {binary.Length}");
        
        var result = binary.BinaryTo<SimStockTaking>();
        
        Assert.IsNotNull(result);
        Assert.AreEqual(1, result.Id, "Id should be 1");
        Assert.AreEqual(6, result.Creator, "Creator should be 6 - this is where the bug occurs!");
        Assert.AreEqual(stockTaking.Created.Ticks, result.Created.Ticks, 
            $"Created mismatch. Expected: {stockTaking.Created}, Got: {result.Created}");
        Assert.AreEqual(stockTaking.StartDateTime, result.StartDateTime);
        Assert.IsFalse(result.IsClosed);
    }

    /// <summary>
    /// Test List of SimStockTaking - exact production scenario.
    /// </summary>
    [TestMethod]
    public void Diagnostic_ListOfSimStockTaking_RoundTrip()
    {
        var stockTakings = Enumerable.Range(1, 3).Select(i => new SimStockTaking
        {
            Id = i,
            StartDateTime = DateTime.UtcNow.AddDays(-i),
            IsClosed = i % 2 == 0,
            Creator = i,
            Created = DateTime.UtcNow.AddDays(-i),
            Modified = DateTime.UtcNow,
            StockTakingItems = null
        }).ToList();

        var binary = stockTakings.ToBinary();
        var result = binary.BinaryTo<List<SimStockTaking>>();

        Assert.IsNotNull(result);
        Assert.AreEqual(3, result.Count);

        for (int i = 0; i < 3; i++)
        {
            var original = stockTakings[i];
            var deserialized = result[i];

            Assert.AreEqual(original.Id, deserialized.Id, $"[{i}] Id mismatch");
            Assert.AreEqual(original.Creator, deserialized.Creator, $"[{i}] Creator mismatch");
            Assert.AreEqual(original.Created.Ticks, deserialized.Created.Ticks, 
                $"[{i}] Created mismatch. Expected: {original.Created}, Got: {deserialized.Created}");
        }
    }

    /// <summary>
    /// Diagnostic: Check what PropertyType the reflection returns for generic type parameter.
    /// </summary>
    [TestMethod]
    public void Diagnostic_GenericProperty_ReflectionType()
    {
        var parentType = typeof(ConcreteParent);
        var itemsProp = parentType.GetProperty("Items");
        
        Assert.IsNotNull(itemsProp);
        
        var propType = itemsProp.PropertyType;
        Console.WriteLine($"PropertyType: {propType}");
        Console.WriteLine($"PropertyType.FullName: {propType.FullName}");
        Console.WriteLine($"IsGenericType: {propType.IsGenericType}");
        
        if (propType.IsGenericType)
        {
            var args = propType.GetGenericArguments();
            Console.WriteLine($"GenericArguments.Length: {args.Length}");
            foreach (var arg in args)
            {
                Console.WriteLine($"  GenericArgument: {arg.FullName}");
            }
        }
        
        Assert.IsTrue(propType.IsGenericType);
        var elementType = propType.GetGenericArguments()[0];
        Assert.AreEqual(typeof(GenericItemImpl), elementType, 
            "Element type should be GenericItemImpl, not IGenericItem");
    }

    /// <summary>
    /// CRITICAL BUG REPRODUCTION: StockTakingItems is null (loadRelations = false)
    /// This test verifies what happens when:
    /// 1. Metadata header registers ALL properties including StockTakingItems
    /// 2. Body SKIPS StockTakingItems because it's null
    /// 3. Deserializer reads the body and must correctly map indices
    /// </summary>
    [TestMethod]
    public void Diagnostic_NullStockTakingItems_VerifyPropertyIndices()
    {
        var stockTaking = new SimStockTaking
        {
            Id = 1,
            StartDateTime = new DateTime(2025, 1, 24, 10, 0, 0, DateTimeKind.Utc),
            IsClosed = false,
            Creator = 6, // The exact value from production error (becomes TinyInt 0xD6)
            Created = new DateTime(2025, 1, 24, 15, 25, 0, DateTimeKind.Utc),
            Modified = new DateTime(2025, 1, 24, 16, 0, 0, DateTimeKind.Utc),
            StockTakingItems = null // THIS IS THE KEY - loadRelations = false
        };

        var binary = stockTaking.ToBinary();
        
        // Log the binary structure
        Console.WriteLine($"Binary length: {binary.Length}");
        
        // Parse the header manually to understand structure
        var pos = 0;
        var version = binary[pos++];
        Console.WriteLine($"Version: {version}");
        
        var marker = binary[pos++];
        Console.WriteLine($"Marker: 0x{marker:X2}");
        
        // Read property count from metadata header
        if ((marker & 0x10) != 0) // HasMetadata flag
        {
            var propCount = binary[pos++];
            Console.WriteLine($"\n=== METADATA HEADER ===");
            Console.WriteLine($"Property count in header: {propCount}");
            
            for (int i = 0; i < propCount; i++)
            {
                var strLen = binary[pos++];
                var propName = System.Text.Encoding.UTF8.GetString(binary, pos, strLen);
                pos += strLen;
                Console.WriteLine($"  Header property [{i}]: '{propName}'");
            }
        }
        
        Console.WriteLine($"\n=== BODY (starts at position {pos}) ===");
        
        // The body should start with Object marker (0x19)
        var bodyStart = pos;
        var objectMarker = binary[pos++];
        Console.WriteLine($"Object marker: 0x{objectMarker:X2} (expected 0x19 for Object)");
        
        // Read ref ID (if reference handling is enabled)
        // VarInt: if top bit is set, continue reading
        var refIdByte = binary[pos];
        int refId;
        if ((refIdByte & 0x80) == 0)
        {
            refId = refIdByte;
            pos++;
        }
        else
        {
            // Multi-byte VarInt - simplified parsing
            refId = -1;
            pos += 2; // Skip for now
        }
        Console.WriteLine($"RefId: {refId}");
        
        // Read property count in body
        var bodyPropCount = binary[pos++];
        Console.WriteLine($"Property count in body: {bodyPropCount}");
        
        Console.WriteLine($"\n=== BODY PROPERTIES ===");
        for (int i = 0; i < bodyPropCount && pos < binary.Length; i++)
        {
            var propIndex = binary[pos++];
            Console.WriteLine($"  Body property [{i}]: index={propIndex}, next bytes: 0x{binary[pos]:X2} 0x{(pos + 1 < binary.Length ? binary[pos + 1] : 0):X2}");
            
            // Skip the value (simplified - just log)
            var valueType = binary[pos];
            if (valueType == 0x14) // DateTime
            {
                Console.WriteLine($"    -> DateTime (9 bytes)");
                pos += 10; // type + 9 bytes
            }
            else if (valueType >= 0xD0 && valueType <= 0xE7) // TinyInt
            {
                var tinyValue = valueType - 0xD0;
                Console.WriteLine($"    -> TinyInt value: {tinyValue}");
                pos += 1;
            }
            else if (valueType == 0x03) // False
            {
                Console.WriteLine($"    -> Boolean: false");
                pos += 1;
            }
            else if (valueType == 0x02) // True
            {
                Console.WriteLine($"    -> Boolean: true");
                pos += 1;
            }
            else
            {
                Console.WriteLine($"    -> Unknown type: 0x{valueType:X2}");
                break;
            }
        }
        
        // Find where 0xD6 (Creator = 6) appears in the body
        Console.WriteLine($"\n=== 0xD6 OCCURRENCES ===");
        for (int i = bodyStart; i < binary.Length; i++)
        {
            if (binary[i] == 0xD6)
            {
                Console.WriteLine($"Found 0xD6 (TinyInt 6 = Creator value) at position {i}");
            }
        }
        
        // Deserialize and verify
        var result = binary.BinaryTo<SimStockTaking>();
        
        Assert.IsNotNull(result);
        Assert.AreEqual(1, result.Id, "Id should be 1");
        Assert.AreEqual(6, result.Creator, 
            $"Creator should be 6. Got: {result.Creator}. " +
            $"If this fails with a very large number, it means DateTime bytes were interpreted as int!");
        Assert.AreEqual(stockTaking.Created, result.Created, 
            $"Created mismatch. Expected: {stockTaking.Created}, Got: {result.Created}. " +
            $"If Created has wrong value, deserializer read wrong bytes!");
        Assert.AreEqual(stockTaking.StartDateTime, result.StartDateTime);
        Assert.IsFalse(result.IsClosed);
        Assert.IsNull(result.StockTakingItems, "StockTakingItems should remain null");
    }

    /// <summary>
    /// Test to verify property order consistency between serializer and deserializer.
    /// </summary>
    [TestMethod]
    public void Diagnostic_VerifyPropertyOrderConsistency()
    {
        // Get serializer's property order
        var serializerType = typeof(AcBinarySerializer);
        var metadataCacheField = serializerType.GetField("TypeMetadataCache", 
            BindingFlags.NonPublic | BindingFlags.Static);
        
        // Clear cache to force fresh metadata creation
        // (This helps ensure we're testing the actual order)
        
        var type = typeof(SimStockTaking);
        var props = type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
            .Where(p => p.CanRead && p.GetIndexParameters().Length == 0)
            .ToArray();
        
        Console.WriteLine($"Properties of {type.Name} (reflection order):");
        for (int i = 0; i < props.Length; i++)
        {
            var prop = props[i];
            Console.WriteLine($"  [{i}] {prop.Name} : {prop.PropertyType.Name}");
        }
        
        // Verify Creator comes BEFORE Created in the reflection order
        var creatorIndex = Array.FindIndex(props, p => p.Name == "Creator");
        var createdIndex = Array.FindIndex(props, p => p.Name == "Created");
        var stockTakingItemsIndex = Array.FindIndex(props, p => p.Name == "StockTakingItems");
        
        Console.WriteLine($"\nKey indices:");
        Console.WriteLine($"  StockTakingItems: {stockTakingItemsIndex}");
        Console.WriteLine($"  Creator: {creatorIndex}");
        Console.WriteLine($"  Created: {createdIndex}");
        
        // The bug scenario: if StockTakingItems is skipped during serialization,
        // but the deserializer still expects it at the original index position,
        // then Creator (index 3) would be read when expecting StockTakingItems (index 2)
        // and Created (index 4) would be read when expecting Creator (index 3)
        
        Assert.IsTrue(stockTakingItemsIndex >= 0, "StockTakingItems should exist");
        Assert.IsTrue(creatorIndex >= 0, "Creator should exist");
        Assert.IsTrue(createdIndex >= 0, "Created should exist");
        
        // In the class definition order:
        // StockTakingItems comes BEFORE Creator and Created
        Assert.IsTrue(stockTakingItemsIndex < creatorIndex, 
            "StockTakingItems should come before Creator");
        Assert.IsTrue(creatorIndex < createdIndex, 
            "Creator should come before Created");
    }

    /// <summary>
    /// Test multiple StockTakings with null StockTakingItems - exact production scenario.
    /// </summary>
    [TestMethod]
    public void Diagnostic_MultipleStockTakings_NullItems()
    {
        var stockTakings = new List<SimStockTaking>
        {
            new()
            {
                Id = 1,
                StartDateTime = new DateTime(2025, 1, 24, 10, 0, 0, DateTimeKind.Utc),
                IsClosed = false,
                Creator = 6,
                Created = new DateTime(2025, 1, 24, 15, 25, 0, DateTimeKind.Utc),
                Modified = new DateTime(2025, 1, 24, 16, 0, 0, DateTimeKind.Utc),
                StockTakingItems = null
            },
            new()
            {
                Id = 2,
                StartDateTime = new DateTime(2025, 1, 23, 9, 0, 0, DateTimeKind.Utc),
                IsClosed = true,
                Creator = 12,
                Created = new DateTime(2025, 1, 23, 14, 0, 0, DateTimeKind.Utc),
                Modified = new DateTime(2025, 1, 23, 15, 30, 0, DateTimeKind.Utc),
                StockTakingItems = null
            }
        };

        var binary = stockTakings.ToBinary();
        Console.WriteLine($"Binary length for 2 StockTakings: {binary.Length}");

        var result = binary.BinaryTo<List<SimStockTaking>>();

        Assert.IsNotNull(result);
        Assert.AreEqual(2, result.Count);

        // First item
        Assert.AreEqual(1, result[0].Id);
        Assert.AreEqual(6, result[0].Creator, "First item Creator should be 6");
        Assert.AreEqual(stockTakings[0].Created, result[0].Created, 
            $"First item Created mismatch. Expected: {stockTakings[0].Created}, Got: {result[0].Created}");

        // Second item
        Assert.AreEqual(2, result[1].Id);
        Assert.AreEqual(12, result[1].Creator, "Second item Creator should be 12");
        Assert.AreEqual(stockTakings[1].Created, result[1].Created,
            $"Second item Created mismatch. Expected: {stockTakings[1].Created}, Got: {result[1].Created}");
    }
}