using LLama.Web.Async;
using LLama.Web.Common;
using LLama.Web.Models;
using Microsoft.Extensions.Options;
using System.Collections.Concurrent;

namespace LLama.Web.Services
{

    /// <summary>
    /// Service for handling Models,Weights & Contexts
    /// </summary>
    public class ModelService : IModelService
    {
        private readonly AsyncLock _modelLock;
        private readonly AsyncLock _contextLock;
        private readonly LLamaOptions _configuration;
        private readonly ILogger<ModelService> _llamaLogger;
        private readonly ConcurrentDictionary<string, LLamaModel> _modelInstances;


        /// <summary>
        /// Initializes a new instance of the <see cref="ModelService"/> class.
        /// </summary>
        /// <param name="logger">The logger.</param>
        /// <param name="options">The options.</param>
        public ModelService(IOptions<LLamaOptions> configuration, ILogger<ModelService> llamaLogger)
        {
            _llamaLogger = llamaLogger;
            _modelLock = new AsyncLock();
            _contextLock = new AsyncLock();
            _configuration = configuration.Value;
            _modelInstances = new ConcurrentDictionary<string, LLamaModel>();
        }


        /// <summary>
        /// Loads a model with the provided configuration.
        /// </summary>
        /// <param name="modelOptions">The model configuration.</param>
        /// <returns></returns>
        public async Task<LLamaModel> LoadModel(ModelOptions modelOptions)
        {
            if (_modelInstances.TryGetValue(modelOptions.Name, out var existingModel))
                return existingModel;

            using (await _modelLock.LockAsync())
            {
                if (_modelInstances.TryGetValue(modelOptions.Name, out var model))
                    return model;

                // If in single mode unload any other models
                if (_configuration.ModelLoadType == ModelLoadType.Single
                 || _configuration.ModelLoadType == ModelLoadType.PreloadSingle)
                    await UnloadModels();


                model = new LLamaModel(modelOptions, _llamaLogger);
                _modelInstances.TryAdd(modelOptions.Name, model);
                return model;
            }
        }


        /// <summary>
        /// Loads the models.
        /// </summary>
        public async Task LoadModels()
        {
            if (_configuration.ModelLoadType == ModelLoadType.Single
             || _configuration.ModelLoadType == ModelLoadType.Multiple)
                return;

            foreach (var modelConfig in _configuration.Models)
            {
                await LoadModel(modelConfig);

                //Only preload first model if in SinglePreload mode
                if (_configuration.ModelLoadType == ModelLoadType.PreloadSingle)
                    break;
            }
        }


        /// <summary>
        /// Unloads the model.
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <returns></returns>
        public Task UnloadModel(string modelName)
        {
            if (_modelInstances.TryRemove(modelName, out var model))
            {
                model?.Dispose();
                return Task.FromResult(true);
            }
            return Task.FromResult(false);
        }



        /// <summary>
        /// Unloads all models.
        /// </summary>
        public async Task UnloadModels()
        {
            foreach (var modelName in _modelInstances.Keys)
            {
                await UnloadModel(modelName);
            }
        }


        /// <summary>
        /// Gets a model ny name.
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <returns></returns>
        public Task<LLamaModel> GetModel(string modelName)
        {
            _modelInstances.TryGetValue(modelName, out var model);
            return Task.FromResult(model);
        }


        /// <summary>
        /// Gets a context from the specified model.
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <param name="contextName">The contextName.</param>
        /// <returns></returns>
        /// <exception cref="System.Exception">Model not found</exception>
        public async Task<LLamaContext> GetContext(string modelName, string contextName)
        {
            if (!_modelInstances.TryGetValue(modelName, out var model))
                throw new Exception("Model not found");

            return await model.GetContext(contextName);
        }


        /// <summary>
        /// Creates a context on the specified model.
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <param name="contextName">The contextName.</param>
        /// <returns></returns>
        /// <exception cref="System.Exception">Model not found</exception>
        public async Task<LLamaContext> CreateContext(string modelName, string contextName)
        {
            if (!_modelInstances.TryGetValue(modelName, out var model))
                throw new Exception("Model not found");

            using (await _contextLock.LockAsync())
            {
                return await model.CreateContext(contextName);
            }
        }


        /// <summary>
        /// Removes a context from the specified model.
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <param name="contextName">The contextName.</param>
        /// <returns></returns>
        /// <exception cref="System.Exception">Model not found</exception>
        public async Task<bool> RemoveContext(string modelName, string contextName)
        {
            if (!_modelInstances.TryGetValue(modelName, out var model))
                throw new Exception("Model not found");

            using (await _contextLock.LockAsync())
            {
                return await model.RemoveContext(contextName);
            }
        }


        /// <summary>
        /// Loads, Gets,Creates a Model and a Context
        /// </summary>
        /// <param name="modelName">Name of the model.</param>
        /// <param name="contextName">The contextName.</param>
        /// <returns></returns>
        /// <exception cref="System.Exception">Model option '{modelName}' not found</exception>
        public async Task<(LLamaModel, LLamaContext)> GetOrCreateModelAndContext(string modelName, string contextName)
        {
            if (_modelInstances.TryGetValue(modelName, out var model))
                return (model, await model.GetContext(contextName) ?? await model.CreateContext(contextName));


            // Get model configuration
            var modelConfig = _configuration.Models.FirstOrDefault(x => x.Name == modelName);
            if (modelConfig is null)
                throw new Exception($"Model option '{modelName}' not found");

            // Load Model
            model = await LoadModel(modelConfig);

            // Get or Create Context
            return (model, await model.GetContext(contextName) ?? await model.CreateContext(contextName));
        }

    }
}