using System.ComponentModel.DataAnnotations.Schema;
using System.Reflection;
using System.Text.Json;
using Npgsql;
using StickyBoard.Core.Models.Base;

namespace StickyBoard.Core.Common;

public static class MappingHelper
{
    public static T MapEntity<T>(NpgsqlDataReader reader) where T : IEntity, new()
    {
        var entity = new T();

        foreach (var prop in typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance))
        {
            var col = prop.GetCustomAttribute<ColumnAttribute>()?.Name
                      ?? prop.Name.ToLower();

            if (!reader.HasColumn(col))
                continue;

            var dbValue = reader[col];
            if (dbValue is DBNull)
                continue;

            var targetType = prop.PropertyType;

            // -----------------------------------------
            // Enum
            // -----------------------------------------
            if (targetType.IsEnum)
            {
                if (dbValue is int i)
                    prop.SetValue(entity, Enum.ToObject(targetType, i));
                else if (int.TryParse(dbValue.ToString(), out var j))
                    prop.SetValue(entity, Enum.ToObject(targetType, j));
                else
                    prop.SetValue(entity, Enum.Parse(targetType, dbValue.ToString()!, true));

                continue;
            }

            // -----------------------------------------
            // Binary: bytea → byte[]
            // -----------------------------------------
            if (targetType == typeof(byte[]))
            {
                prop.SetValue(entity, (byte[])dbValue);
                continue;
            }


            // -----------------------------------------
            // JSON: jsonb → JsonDocument
            // -----------------------------------------
            if (targetType == typeof(JsonDocument))
            {
                if (dbValue is string s)
                    prop.SetValue(entity, JsonDocument.Parse(s));
                else if (dbValue is JsonElement el)
                    prop.SetValue(entity, JsonDocument.Parse(el.GetRawText()));
                else
                    prop.SetValue(entity, JsonDocument.Parse("{}"));
                continue;
            }

            // -----------------------------------------
            // Arrays: PostgreSQL text[] → string[]
            // -----------------------------------------
            if (targetType == typeof(string[]))
            {
                prop.SetValue(entity, (string[])dbValue);
                continue;
            }

            // -----------------------------------------
            // Nullable<T>
            // -----------------------------------------
            var underlying = Nullable.GetUnderlyingType(targetType);
            if (underlying != null)
            {
                prop.SetValue(entity, Convert.ChangeType(dbValue, underlying));
                continue;
            }

            // -----------------------------------------
            // Guid
            // -----------------------------------------
            if (targetType == typeof(Guid))
            {
                prop.SetValue(entity, (Guid)dbValue);
                continue;
            }

            // -----------------------------------------
            // bool
            // -----------------------------------------
            if (targetType == typeof(bool))
            {
                prop.SetValue(entity, (bool)dbValue);
                continue;
            }

            // -----------------------------------------
            // int
            // -----------------------------------------
            if (targetType == typeof(int))
            {
                prop.SetValue(entity, (int)dbValue);
                continue;
            }

            // -----------------------------------------
            // DateTime
            // -----------------------------------------
            if (targetType == typeof(DateTime))
            {
                prop.SetValue(entity, (DateTime)dbValue);
                continue;
            }

            // -----------------------------------------
            // string
            // -----------------------------------------
            if (targetType == typeof(string))
            {
                prop.SetValue(entity, dbValue.ToString());
                continue;
            }

            // -----------------------------------------
            // Fallback: Convert.ChangeType
            // -----------------------------------------
            prop.SetValue(entity, Convert.ChangeType(dbValue, targetType));
        }

        return entity;
    }

    // Helper for safe column lookup
    private static bool HasColumn(this NpgsqlDataReader r, string column)
    {
        for (var i = 0; i < r.FieldCount; i++)
            if (string.Equals(r.GetName(i), column, StringComparison.OrdinalIgnoreCase))
                return true;
        return false;
    }
}