using System.Net.Http.Headers;
using System.Runtime.CompilerServices;
using System.Text;
using System.Text.Json;

using AIStudio.Chat;
using AIStudio.Provider.OpenAI;
using AIStudio.Settings;

namespace AIStudio.Provider.Google;

public class ProviderGoogle() : BaseProvider(LLMProviders.GOOGLE, "https://generativelanguage.googleapis.com/v1beta/openai/", LOGGER)
{
    private static readonly ILogger<ProviderGoogle> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderGoogle>();

    #region Implementation of IProvider

    /// <inheritdoc />
    public override string Id => LLMProviders.GOOGLE.ToName();

    /// <inheritdoc />
    public override string InstanceName { get; set; } = "Google Gemini";

    /// <inheritdoc />
    public override async IAsyncEnumerable<ContentStreamChunk> StreamChatCompletion(Model chatModel, ChatThread chatThread, SettingsManager settingsManager, [EnumeratorCancellation] CancellationToken token = default)
    {
        // Get the API key:
        var requestedSecret = await RUST_SERVICE.GetAPIKey(this, SecretStoreType.LLM_PROVIDER);
        if(!requestedSecret.Success)
            yield break;

        // Prepare the system prompt:
        var systemPrompt = new TextMessage
        {
            Role = "system",
            Content = chatThread.PrepareSystemPrompt(settingsManager),
        };
        
        // Parse the API parameters:
        var apiParameters = this.ParseAdditionalApiParameters();
        
        // Build the list of messages:
        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
        
        // Prepare the Google HTTP chat request:
        var geminiChatRequest = JsonSerializer.Serialize(new ChatRequest
        {
            Model = chatModel.Id,
            
            // Build the messages:
            // - First of all the system prompt
            // - Then none-empty user and AI messages
            Messages = [systemPrompt, ..messages],
            
            // Right now, we only support streaming completions:
            Stream = true,
            AdditionalApiParameters = apiParameters
        }, JSON_SERIALIZER_OPTIONS);

        async Task<HttpRequestMessage> RequestBuilder()
        {
            // Build the HTTP post request:
            var request = new HttpRequestMessage(HttpMethod.Post, "chat/completions");

            // Set the authorization header:
            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", await requestedSecret.Secret.Decrypt(ENCRYPTION));

            // Set the content:
            request.Content = new StringContent(geminiChatRequest, Encoding.UTF8, "application/json");
            return request;
        }
        
        await foreach (var content in this.StreamChatCompletionInternal<ChatCompletionDeltaStreamLine, NoChatCompletionAnnotationStreamLine>("Google", RequestBuilder, token))
            yield return content;
    }

    #pragma warning disable CS1998 // Async method lacks 'await' operators and will run synchronously
    /// <inheritdoc />
    public override async IAsyncEnumerable<ImageURL> StreamImageCompletion(Model imageModel, string promptPositive, string promptNegative = FilterOperator.String.Empty, ImageURL referenceImageURL = default, [EnumeratorCancellation] CancellationToken token = default)
    {
        yield break;
    }
    #pragma warning restore CS1998 // Async method lacks 'await' operators and will run synchronously

    /// <inheritdoc />
    public override Task<string> TranscribeAudioAsync(Model transcriptionModel, string audioFilePath, SettingsManager settingsManager, CancellationToken token = default)
    {
        return Task.FromResult(string.Empty);
    }

    /// <inheritdoc />
    public override async Task<IEnumerable<Model>> GetTextModels(string? apiKeyProvisional = null, CancellationToken token = default)
    {
        var models = await this.LoadModels(SecretStoreType.LLM_PROVIDER, token, apiKeyProvisional);
        return models.Where(model =>
                model.Id.StartsWith("gemini-", StringComparison.OrdinalIgnoreCase) &&
                !this.IsEmbeddingModel(model.Id))
            .Select(this.WithDisplayNameFallback);
    }

    /// <inheritdoc />
    public override Task<IEnumerable<Model>> GetImageModels(string? apiKeyProvisional = null, CancellationToken token = default)
    {
        return Task.FromResult(Enumerable.Empty<Model>());
    }

    public override async Task<IEnumerable<Model>> GetEmbeddingModels(string? apiKeyProvisional = null, CancellationToken token = default)
    {
        var models = await this.LoadModels(SecretStoreType.EMBEDDING_PROVIDER, token, apiKeyProvisional);
        return models.Where(model => this.IsEmbeddingModel(model.Id))
            .Select(this.WithDisplayNameFallback);
    }
    
    /// <inheritdoc />
    public override Task<IEnumerable<Model>> GetTranscriptionModels(string? apiKeyProvisional = null, CancellationToken token = default)
    {
        return Task.FromResult(Enumerable.Empty<Model>());
    }
    
    #endregion

    private async Task<IReadOnlyList<Model>> LoadModels(SecretStoreType storeType, CancellationToken token, string? apiKeyProvisional = null)
    {
        var secretKey = apiKeyProvisional switch
        {
            not null => apiKeyProvisional,
            _ => await RUST_SERVICE.GetAPIKey(this, storeType) switch
            {
                { Success: true } result => await result.Secret.Decrypt(ENCRYPTION),
                _ => null,
            }
        };

        if (string.IsNullOrWhiteSpace(secretKey))
            return [];

        using var request = new HttpRequestMessage(HttpMethod.Get, "models");
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", secretKey);
        
        using var response = await this.httpClient.SendAsync(request, token);
        if(!response.IsSuccessStatusCode)
        {
            LOGGER.LogError("Failed to load models with status code {ResponseStatusCode} and body: '{ResponseBody}'.", response.StatusCode, await response.Content.ReadAsStringAsync(token));
            return [];
        }

        try
        {
            var modelResponse = await response.Content.ReadFromJsonAsync<ModelsResponse>(token);
            if (modelResponse == default || modelResponse.Data.Count is 0)
            {
                LOGGER.LogError("Google model list response did not contain a valid data array.");
                return [];
            }

            return modelResponse.Data
                .Where(model => !string.IsNullOrWhiteSpace(model.Id))
                .Select(model => new Model(this.NormalizeModelId(model.Id), model.DisplayName))
                .ToArray();
        }
        catch (Exception e)
        {
            LOGGER.LogError("Failed to parse Google model list response: '{Message}'.", e.Message);
            return [];
        }
    }

    private bool IsEmbeddingModel(string modelId)
    {
        return modelId.Contains("embedding", StringComparison.OrdinalIgnoreCase) ||
               modelId.Contains("embed", StringComparison.OrdinalIgnoreCase);
    }

    private Model WithDisplayNameFallback(Model model)
    {
        return string.IsNullOrWhiteSpace(model.DisplayName)
            ? new Model(model.Id, model.Id)
            : model;
    }

    private string NormalizeModelId(string modelId)
    {
        return modelId.StartsWith("models/", StringComparison.OrdinalIgnoreCase)
            ? modelId["models/".Length..]
            : modelId;
    }
}