namespace DramaLing.Api.Services;

/// <summary>
/// 測驗模式選擇服務介面
/// </summary>
public interface IReviewModeSelector
{
    List<string> GetPlannedTests(string userCEFRLevel, string wordCEFRLevel);
    string GetNextTestType(List<string> plannedTests, List<string> completedTestTypes);
}

/// <summary>
/// 測驗模式選擇服務實現
/// </summary>
public class ReviewModeSelector : IReviewModeSelector
{
    private readonly ILogger<ReviewModeSelector> _logger;

    public ReviewModeSelector(ILogger<ReviewModeSelector> logger)
    {
        _logger = logger;
    }

    /// <summary>
    /// 根據CEFR等級獲取預定的測驗類型列表
    /// </summary>
    public List<string> GetPlannedTests(string userCEFRLevel, string wordCEFRLevel)
    {
        var userLevel = GetCEFRLevel(userCEFRLevel);
        var wordLevel = GetCEFRLevel(wordCEFRLevel);
        var difficulty = wordLevel - userLevel;

        _logger.LogDebug("Planning tests for user {UserCEFR} vs word {WordCEFR}, difficulty: {Difficulty}",
            userCEFRLevel, wordCEFRLevel, difficulty);

        if (userCEFRLevel == "A1")
        {
            // A1學習者：基礎保護機制
            return new List<string> { "flip-memory", "vocab-choice", "vocab-listening" };
        }
        else if (difficulty < -10)
        {
            // 簡單詞彙：應用練習
            return new List<string> { "sentence-fill", "sentence-reorder" };
        }
        else if (difficulty >= -10 && difficulty <= 10)
        {
            // 適中詞彙：全方位練習
            return new List<string> { "sentence-fill", "sentence-reorder", "sentence-speaking" };
        }
        else
        {
            // 困難詞彙：基礎重建
            return new List<string> { "flip-memory", "vocab-choice" };
        }
    }

    /// <summary>
    /// 獲取下一個測驗類型
    /// </summary>
    public string GetNextTestType(List<string> plannedTests, List<string> completedTestTypes)
    {
        var nextTest = plannedTests.FirstOrDefault(test => !completedTestTypes.Contains(test));
        return nextTest ?? string.Empty;
    }

    /// <summary>
    /// CEFR等級轉換為數值
    /// </summary>
    private int GetCEFRLevel(string cefrLevel)
    {
        return cefrLevel switch
        {
            "A1" => 20,
            "A2" => 35,
            "B1" => 50,
            "B2" => 65,
            "C1" => 80,
            "C2" => 95,
            _ => 50 // 預設B1
        };
    }
}