using System.Collections.Concurrent;
using Flurl.Http;
using InnovEnergy.App.Backend.Database;
using InnovEnergy.App.Backend.DataTypes;
using Newtonsoft.Json;

namespace InnovEnergy.App.Backend.Services;

/// <summary>
/// Calls Mistral AI to generate plain-English diagnostics for errors/warnings.
/// Caches responses in-memory keyed by error description so the same
/// error code is only sent to the API once.
/// </summary>
public static class DiagnosticService
{
    private static string _apiKey = "";

    /// <summary>In-memory cache: errorDescription → parsed response.</summary>
    private static readonly ConcurrentDictionary<string, DiagnosticResponse> Cache = new();

    // ── initialisation ──────────────────────────────────────────────

    public static void Initialize()
    {
        var apiKey = Environment.GetEnvironmentVariable("MISTRAL_API_KEY");

        if (string.IsNullOrWhiteSpace(apiKey))
        {
            Console.Error.WriteLine("[DiagnosticService] MISTRAL_API_KEY not set – AI diagnostics disabled.");
            return;
        }

        _apiKey = apiKey;
        Console.WriteLine("[DiagnosticService] initialised.");
    }

    public static bool IsEnabled => !string.IsNullOrEmpty(_apiKey);

    // ── public entry-point ──────────────────────────────────────────

    /// <summary>
    /// Returns a diagnosis for <paramref name="errorDescription"/>.
    /// First checks the static AlarmKnowledgeBase for known Sinexcel/Growatt alarms.
    /// Falls back to in-memory cache, then calls Mistral AI only for unknown alarms.
    /// </summary>
    public static async Task<DiagnosticResponse?> DiagnoseAsync(Int64 installationId, string errorDescription)
    {
        // 1. Check the static knowledge base first (no API call needed)
        var knownDiagnosis = AlarmKnowledgeBase.TryGetDiagnosis(errorDescription);
        if (knownDiagnosis is not null)
        {
            Console.WriteLine($"[DiagnosticService] Found diagnosis in knowledge base for: {errorDescription}");
            return knownDiagnosis;
        }

        // 2. If AI is not enabled, we can't proceed further
        if (!IsEnabled) return null;

        // 3. Check in-memory cache for previously fetched AI diagnoses
        if (Cache.TryGetValue(errorDescription, out var cached))
            return cached;

        // 4. Gather context from the DB for AI prompt
        var installation = Db.GetInstallationById(installationId);
        if (installation is null) return null;

        var productName = ((ProductType)installation.Product).ToString();

        var recentDescriptions = Db.Errors
            .Where(e => e.InstallationId == installationId)
            .OrderByDescending(e => e.Date + " " + e.Time)   // Date/Time stored as strings in DB
            .Select(e => e.Description)
            .Distinct()                                       // deduplicate — same error repeated adds no signal
            .Take(5)
            .ToList();

        // 5. Build prompt and call Mistral API (only for unknown alarms)
        Console.WriteLine($"[DiagnosticService] Calling Mistral for unknown alarm: {errorDescription}");
        var prompt   = BuildPrompt(errorDescription, productName, recentDescriptions);
        var response = await CallMistralAsync(prompt);

        if (response is null) return null;

        // 6. Store in cache for future requests
        Cache.TryAdd(errorDescription, response);
        return response;
    }

    // ── prompt ──────────────────────────────────────────────────────

    private static string BuildPrompt(string errorDescription, string productName, List<string> recentErrors)
    {
        var recentList = recentErrors.Count > 0
            ? string.Join(", ", recentErrors)
            : "none";

        return $@"You are a technician for Innovenergy {productName} battery energy storage systems.
These are lithium-ion BESS units with a BMS, PV inverter, and grid inverter.

Error: {errorDescription}
Other recent errors: {recentList}

Explain in plain English for a homeowner. List likely causes and next steps.
Reply with ONLY valid JSON, no markdown:
{{""explanation"":""2-3 sentences"",""causes"":[""...""],""nextSteps"":[""...""]}}
";
    }

    // ── Mistral HTTP call ────────────────────────────────────────────

    private static readonly string MistralUrl = "https://api.mistral.ai/v1/chat/completions";

    private static async Task<DiagnosticResponse?> CallMistralAsync(string userPrompt)
    {
        try
        {
            var requestBody = new
            {
                model = "mistral-small-latest",  // cost-efficient, fast; swap to "mistral-large-latest" if quality needs tuning
                messages = new[]
                {
                    new { role = "user", content = userPrompt }
                },
                max_tokens  = 400,
                temperature = 0.2               // low temperature for factual consistency
            };

            var responseText = await MistralUrl
                .SetHeader("Authorization", $"Bearer {_apiKey}")
                .SetHeader("Content-Type", "application/json")
                .PostJsonAsync(requestBody)
                .ReceiveString();

            // parse Mistral envelope (same structure as OpenAI)
            var envelope = JsonConvert.DeserializeObject<dynamic>(responseText);
            var content  = (string?) envelope?.choices?[0]?.message?.content;

            if (string.IsNullOrWhiteSpace(content))
            {
                Console.Error.WriteLine("[DiagnosticService] Mistral returned empty content.");
                return null;
            }

            // parse the JSON the model produced
            var diagnostic = JsonConvert.DeserializeObject<DiagnosticResponse>(content);
            return diagnostic;
        }
        catch (FlurlHttpException httpEx)
        {
            Console.Error.WriteLine($"[DiagnosticService] HTTP error {httpEx.Response?.StatusCode}: {await httpEx.Response?.GetStringAsync()}");
            return null;
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[DiagnosticService] {ex.Message}");
            return null;
        }
    }
}

// ── config / response models ────────────────────────────────────────────────

public class DiagnosticResponse
{
    public string               Explanation { get; set; } = "";
    public IReadOnlyList<string> Causes     { get; set; } = Array.Empty<string>();
    public IReadOnlyList<string> NextSteps  { get; set; } = Array.Empty<string>();
}