dramaling-vocab-learning/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.cs

using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

namespace DramaLing.Api.Migrations
{
    /// <inheritdoc />
    public partial class AddDifficultyLevelNumeric : Migration
    {
        /// <inheritdoc />
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            // 1. 新增數字欄位 (預設值為 0)
            migrationBuilder.AddColumn<int>(
                name: "difficulty_level_numeric",
                table: "flashcards",
                type: "INTEGER",
                nullable: false,
                defaultValue: 0);

            // 2. 資料遷移：將現有字串值轉換為數字
            migrationBuilder.Sql(@"
                UPDATE flashcards
                SET difficulty_level_numeric =
                    CASE difficulty_level
                        WHEN 'A1' THEN 1
                        WHEN 'A2' THEN 2
                        WHEN 'B1' THEN 3
                        WHEN 'B2' THEN 4
                        WHEN 'C1' THEN 5
                        WHEN 'C2' THEN 6
                        ELSE 0
                    END
                WHERE difficulty_level IS NOT NULL;
            ");
        }

        /// <inheritdoc />
        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropColumn(
                name: "difficulty_level_numeric",
                table: "flashcards");
        }
    }
}