using System.Diagnostics;
using System.Reflection;
using System.Text;

namespace CrupestApi.Commons.Crud;

public class ColumnInfo
{
    private readonly AggregateColumnMetadata _metadata = new AggregateColumnMetadata();
    private ILogger<ColumnInfo> _logger;

    /// <summary>
    /// Initialize a column without corresponding property.
    /// </summary>
    public ColumnInfo(TableInfo table, IColumnMetadata metadata, Type clrType, IColumnTypeProvider typeProvider, ILoggerFactory loggerFactory)
    {
        _logger = loggerFactory.CreateLogger<ColumnInfo>();
        if (metadata is null)
            throw new ArgumentException("You must specify metadata for non-property column.");
        if (metadata.TryGetValue(ColumnMetadataKeys.ColumnName, out var columnName))
            _logger.LogInformation("Create column without property.", columnName);
        else
            throw new ArgumentException("You must specify name in metadata for non-property column.");

        Table = table;
        _metadata.Add(metadata);
        ColumnType = typeProvider.Get(clrType);
    }

    /// <summary>
    /// Initialize a column with corresponding property.
    /// </summary>
    public ColumnInfo(TableInfo table, PropertyInfo propertyInfo, IColumnTypeProvider typeProvider, ILoggerFactory loggerFactory)
    {
        _logger = loggerFactory.CreateLogger<ColumnInfo>();
        _logger.LogInformation("Create column with property {}.", propertyInfo.Name);

        Table = table;
        PropertyInfo = propertyInfo;
        ColumnType = typeProvider.Get(propertyInfo.PropertyType);

        var columnAttribute = propertyInfo.GetCustomAttribute<ColumnAttribute>();
        if (columnAttribute is not null)
        {
            _metadata.Add(columnAttribute);
        }
    }

    public TableInfo Table { get; }

    public Type EntityType => Table.EntityType;

    // If null, there is no corresponding property.
    public PropertyInfo? PropertyInfo { get; } = null;

    public IColumnMetadata Metadata => _metadata;

    public IColumnTypeInfo ColumnType { get; }

    public bool IsPrimaryKey => Metadata.GetValueOrDefault(ColumnMetadataKeys.IsPrimaryKey) is true;
    public bool IsAutoIncrement => IsPrimaryKey;
    public bool IsNotNull => IsPrimaryKey || Metadata.GetValueOrDefault(ColumnMetadataKeys.NotNull) is true;
    public bool IsOnlyGenerated => Metadata.GetValueOrDefault(ColumnMetadataKeys.OnlyGenerated) is true;
    public bool IsNoUpdate => Metadata.GetValueOrDefault(ColumnMetadataKeys.NoUpdate) is true;
    public object? DefaultValue => Metadata.GetValueOrDefault(ColumnMetadataKeys.DefaultValue);
    /// <summary>
    /// This only returns metadata value. It doesn't not fall back to primary column. If you want to get the real key column, go to table info.
    /// </summary>
    /// <seealso cref="ColumnMetadataKeys.ActAsKey"/>
    /// <seealso cref="TableInfo.KeyColumn"/>
    public bool IsSpecifiedAsKey => Metadata.GetValueOrDefault(ColumnMetadataKeys.ActAsKey) is true;
    public ColumnIndexType Index => Metadata.GetValueOrDefault<ColumnIndexType?>(ColumnMetadataKeys.Index) ?? ColumnIndexType.None;

    /// <summary>
    /// Whether the column value can be generated, which means the column has a default value or a default value generator or is AUTOINCREMENT.
    /// </summary>
    public bool CanBeGenerated => DefaultValue is not null || DefaultValueGeneratorMethod is not null || IsAutoIncrement;

    /// <summary>
    /// The real column name. Maybe set in metadata or just the property name.
    /// </summary>
    /// <value></value>
    public string ColumnName
    {
        get
        {
            object? value = Metadata.GetValueOrDefault(ColumnMetadataKeys.ColumnName);
            Debug.Assert(value is null || value is string);
            return ((string?)value ?? PropertyInfo?.Name) ?? throw new Exception("Failed to get column name.");
        }
    }

    public MethodInfo? DefaultValueGeneratorMethod
    {
        get
        {
            object? value = Metadata.GetValueOrDefault(ColumnMetadataKeys.DefaultValueGenerator);
            Debug.Assert(value is null || value is string);
            MethodInfo? result;
            if (value is null)
            {
                string methodName = ColumnName + "DefaultValueGenerator";
                result = Table.EntityType.GetMethod(methodName, BindingFlags.Public | BindingFlags.Static);
            }
            else
            {
                string methodName = (string)value;
                result = Table.EntityType.GetMethod(methodName, BindingFlags.Static) ?? throw new Exception("The default value generator does not exist.");
            }

            return result;
        }
    }

    public MethodInfo? ValidatorMethod
    {
        get
        {
            object? value = Metadata.GetValueOrDefault(ColumnMetadataKeys.DefaultValueGenerator);
            Debug.Assert(value is null || value is string);
            MethodInfo? result;
            if (value is null)
            {
                string methodName = ColumnName + "Validator";
                result = Table.EntityType.GetMethod(methodName, BindingFlags.Static);
            }
            else
            {
                string methodName = (string)value;
                result = Table.EntityType.GetMethod(methodName, BindingFlags.Static) ?? throw new Exception("The validator does not exist.");
            }

            return result;
        }
    }

    public void InvokeValidator(object? value)
    {
        var method = this.ValidatorMethod;
        if (method is null)
        {
            _logger.LogInformation("Try to invoke validator for column {} but it does not exist.", ColumnName);
            return;
        }
        var parameters = method.GetParameters();
        if (parameters.Length == 0)
        {
            throw new Exception("The validator method must have at least one parameter.");
        }
        else if (parameters.Length == 1)
        {
            method.Invoke(null, new object?[] { value });
        }
        else if (parameters.Length == 2)
        {
            if (parameters[0].ParameterType == typeof(ColumnInfo))
                method.Invoke(null, new object?[] { this, value });
            else if (parameters[1].ParameterType == typeof(ColumnInfo))
                method.Invoke(null, new object?[] { value, this });
            else
                throw new Exception("The validator method must have a parameter of type ColumnInfo if it has 2 parameters.");
        }
        else
        {
            throw new Exception("The validator method can only have 1 or 2 parameters.");
        }
    }

    public object? InvokeDefaultValueGenerator()
    {
        var method = this.DefaultValueGeneratorMethod;
        if (method is null)
        {
            _logger.LogInformation("Try to invoke default value generator for column {} but it does not exist.", ColumnName);
            return null;
        }
        var parameters = method.GetParameters();
        if (parameters.Length == 0)
        {
            return method.Invoke(null, new object?[0]);
        }
        else if (parameters.Length == 1)
        {
            if (parameters[0].ParameterType != typeof(ColumnInfo))
                throw new Exception("The default value generator method can only have a parameter of type ColumnInfo.");
            return method.Invoke(null, new object?[] { this });
        }
        else
        {
            throw new Exception("The default value generator method can only have 0 or 1 parameter.");
        }
    }

    public object? GenerateDefaultValue()
    {
        if (DefaultValueGeneratorMethod is not null)
        {
            return InvokeDefaultValueGenerator();
        }

        if (Metadata.TryGetValue(ColumnMetadataKeys.DefaultValue, out object? value))
        {
            return value;
        }
        else
        {
            return null;
        }
    }

    public string GenerateCreateTableColumnString(string? dbProviderId = null)
    {
        StringBuilder result = new StringBuilder();
        result.Append(ColumnName);
        result.Append(' ');
        result.Append(ColumnType.GetSqlTypeString(dbProviderId));
        if (IsPrimaryKey)
        {
            result.Append(' ');
            result.Append("PRIMARY KEY");
        }
        else if (IsNotNull)
        {
            result.Append(' ');
            result.Append("NOT NULL");
        }

        if (IsAutoIncrement)
        {
            result.Append(' ');
            result.Append("AUTOINCREMENT");
        }

        return result.ToString();
    }
}