dramaling-vocab-learning/backend/DramaLing.Api/Services/AI/AIProviderManager.cs

using DramaLing.Api.Models.DTOs;

namespace DramaLing.Api.Services.AI;

/// <summary>
/// AI 提供商管理器實作
/// </summary>
public class AIProviderManager : IAIProviderManager
{
    private readonly IEnumerable<IAIProvider> _providers;
    private readonly ILogger<AIProviderManager> _logger;
    private readonly Random _random = new();

    public AIProviderManager(IEnumerable<IAIProvider> providers, ILogger<AIProviderManager> logger)
    {
        _providers = providers ?? throw new ArgumentNullException(nameof(providers));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));

        _logger.LogInformation("AIProviderManager initialized with {ProviderCount} providers: {ProviderNames}",
            _providers.Count(), string.Join(", ", _providers.Select(p => p.ProviderName)));
    }

    public async Task<IAIProvider> GetBestProviderAsync(ProviderSelectionStrategy strategy = ProviderSelectionStrategy.Performance)
    {
        var availableProviders = await GetAvailableProvidersAsync();

        if (!availableProviders.Any())
        {
            throw new InvalidOperationException("No AI providers are available");
        }

        var selectedProvider = strategy switch
        {
            ProviderSelectionStrategy.Performance => await SelectByPerformanceAsync(availableProviders),
            ProviderSelectionStrategy.Cost => SelectByCost(availableProviders),
            ProviderSelectionStrategy.Reliability => await SelectByReliabilityAsync(availableProviders),
            ProviderSelectionStrategy.LoadBalance => SelectByLoadBalance(availableProviders),
            ProviderSelectionStrategy.Primary => SelectPrimary(availableProviders),
            _ => availableProviders.First()
        };

        _logger.LogDebug("Selected AI provider: {ProviderName} using strategy: {Strategy}",
            selectedProvider.ProviderName, strategy);

        return selectedProvider;
    }

    public async Task<IEnumerable<IAIProvider>> GetAvailableProvidersAsync()
    {
        var availableProviders = new List<IAIProvider>();

        foreach (var provider in _providers)
        {
            try
            {
                if (provider.IsAvailable)
                {
                    var healthStatus = await provider.CheckHealthAsync();
                    if (healthStatus.IsHealthy)
                    {
                        availableProviders.Add(provider);
                    }
                    else
                    {
                        _logger.LogWarning("Provider {ProviderName} is not healthy: {Error}",
                            provider.ProviderName, healthStatus.ErrorMessage);
                    }
                }
                else
                {
                    _logger.LogWarning("Provider {ProviderName} is not available", provider.ProviderName);
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error checking provider {ProviderName} availability", provider.ProviderName);
            }
        }

        return availableProviders;
    }

    public async Task<IAIProvider?> GetProviderByNameAsync(string providerName)
    {
        var provider = _providers.FirstOrDefault(p => p.ProviderName.Equals(providerName, StringComparison.OrdinalIgnoreCase));

        if (provider != null && provider.IsAvailable)
        {
            try
            {
                var healthStatus = await provider.CheckHealthAsync();
                if (healthStatus.IsHealthy)
                {
                    return provider;
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error checking provider {ProviderName} health", providerName);
            }
        }

        return null;
    }

    public async Task<ProviderHealthReport> CheckAllProvidersHealthAsync()
    {
        var report = new ProviderHealthReport
        {
            CheckedAt = DateTime.UtcNow,
            TotalProviders = _providers.Count()
        };

        var healthTasks = _providers.Select(async provider =>
        {
            try
            {
                var healthStatus = await provider.CheckHealthAsync();
                var stats = await provider.GetStatsAsync();

                return new ProviderHealthInfo
                {
                    ProviderName = provider.ProviderName,
                    IsHealthy = healthStatus.IsHealthy,
                    ResponseTimeMs = healthStatus.ResponseTimeMs,
                    ErrorMessage = healthStatus.ErrorMessage,
                    Stats = stats
                };
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error checking health for provider {ProviderName}", provider.ProviderName);
                return new ProviderHealthInfo
                {
                    ProviderName = provider.ProviderName,
                    IsHealthy = false,
                    ErrorMessage = ex.Message,
                    Stats = new AIProviderStats()
                };
            }
        });

        report.ProviderHealthInfos = (await Task.WhenAll(healthTasks)).ToList();
        report.HealthyProviders = report.ProviderHealthInfos.Count(p => p.IsHealthy);

        return report;
    }

    public async Task<SentenceAnalysisData> AnalyzeSentenceAsync(string inputText, AnalysisOptions options,
        ProviderSelectionStrategy strategy = ProviderSelectionStrategy.Performance)
    {
        var provider = await GetBestProviderAsync(strategy);

        try
        {
            var result = await provider.AnalyzeSentenceAsync(inputText, options);
            _logger.LogInformation("Sentence analyzed successfully using provider: {ProviderName}", provider.ProviderName);
            return result;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error analyzing sentence with provider {ProviderName}, attempting fallback",
                provider.ProviderName);

            // 嘗試使用其他可用的提供商
            var availableProviders = (await GetAvailableProvidersAsync())
                .Where(p => p.ProviderName != provider.ProviderName)
                .ToList();

            foreach (var fallbackProvider in availableProviders)
            {
                try
                {
                    var result = await fallbackProvider.AnalyzeSentenceAsync(inputText, options);
                    _logger.LogWarning("Fallback successful using provider: {ProviderName}", fallbackProvider.ProviderName);
                    return result;
                }
                catch (Exception fallbackEx)
                {
                    _logger.LogError(fallbackEx, "Fallback provider {ProviderName} also failed", fallbackProvider.ProviderName);
                }
            }

            // 如果所有提供商都失敗，重新拋出原始異常
            throw;
        }
    }

    #region 私有選擇方法

    private async Task<IAIProvider> SelectByPerformanceAsync(IEnumerable<IAIProvider> providers)
    {
        var providerList = providers.ToList();
        var performanceData = new List<(IAIProvider Provider, int ResponseTime)>();

        foreach (var provider in providerList)
        {
            try
            {
                var stats = await provider.GetStatsAsync();
                performanceData.Add((provider, stats.AverageResponseTimeMs));
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Could not get stats for provider {ProviderName}", provider.ProviderName);
                performanceData.Add((provider, int.MaxValue)); // 最低優先級
            }
        }

        return performanceData
            .OrderBy(p => p.ResponseTime)
            .First().Provider;
    }

    private IAIProvider SelectByCost(IEnumerable<IAIProvider> providers)
    {
        return providers
            .OrderBy(p => p.CostPerRequest)
            .First();
    }

    private async Task<IAIProvider> SelectByReliabilityAsync(IEnumerable<IAIProvider> providers)
    {
        var providerList = providers.ToList();
        var reliabilityData = new List<(IAIProvider Provider, double SuccessRate)>();

        foreach (var provider in providerList)
        {
            try
            {
                var stats = await provider.GetStatsAsync();
                reliabilityData.Add((provider, stats.SuccessRate));
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Could not get stats for provider {ProviderName}", provider.ProviderName);
                reliabilityData.Add((provider, 0.0)); // 最低優先級
            }
        }

        return reliabilityData
            .OrderByDescending(p => p.SuccessRate)
            .First().Provider;
    }

    private IAIProvider SelectByLoadBalance(IEnumerable<IAIProvider> providers)
    {
        var providerList = providers.ToList();
        var randomIndex = _random.Next(providerList.Count);
        return providerList[randomIndex];
    }

    private IAIProvider SelectPrimary(IEnumerable<IAIProvider> providers)
    {
        // 使用第一個可用的提供商作為主要提供商
        return providers.First();
    }

    #endregion
}