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 ──────────────────────────────────────────

    private static string LanguageName(string code) => code switch
    {
        "de" => "German",
        "fr" => "French",
        "it" => "Italian",
        _    => "English"
    };

    /// <summary>
    /// Returns a diagnosis for <paramref name="errorDescription"/> in the given language.
    /// For English: checks the static AlarmKnowledgeBase first, then in-memory cache, then Mistral AI.
    /// For other languages: skips the knowledge base (English-only) and goes directly to Mistral AI.
    /// Cache is keyed by (errorDescription, language) so each language is cached separately.
    /// </summary>
    public static async Task<DiagnosticResponse?> DiagnoseAsync(Int64 installationId, string errorDescription, string language = "en")
    {
        var cacheKey = $"{errorDescription}|{language}";

        // 1. For English only: check the static knowledge base first (no API call needed)
        if (language == "en")
        {
            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(cacheKey, 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)
            .ThenByDescending(e => e.Time)
            .ToList()                                         // materialize before LINQ-to-objects ops
            .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} ({language})");
        var prompt   = BuildPrompt(errorDescription, productName, recentDescriptions, language);
        var response = await CallMistralAsync(prompt);

        if (response is null) return null;

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

    // ── test helper (no DB dependency) ─────────────────────────────

    /// <summary>
    /// Calls Mistral directly with a generic prompt. For testing only - no DB lookup.
    /// </summary>
    public static async Task<DiagnosticResponse?> TestCallMistralAsync(string errorDescription)
    {
        if (!IsEnabled) return null;

        // Check cache first
        if (Cache.TryGetValue(errorDescription, out var cached))
            return cached;

        var prompt   = BuildPrompt(errorDescription, "SodioHome", new List<string>(), "en");
        var response = await CallMistralAsync(prompt);

        if (response is not null)
            Cache.TryAdd(errorDescription, response);

        return response;
    }

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

    private static string BuildPrompt(string errorDescription, string productName, List<string> recentErrors, string language = "en")
    {
        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 for a non-technical homeowner. Keep it very short and simple:
- explanation: 1 short sentence, no jargon
- causes: 2-3 bullet points, plain language
- nextSteps: 2-3 simple action items a homeowner can understand
IMPORTANT: Write all text values in {LanguageName(language)}. Reply with ONLY valid JSON, no markdown:
{{""explanation"":""1 short sentence"",""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
                .WithHeader("Authorization", $"Bearer {_apiKey}")
                .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;
            }

            // strip markdown code fences if Mistral wraps the JSON in ```json ... ```
            var json = content.Trim();
            if (json.StartsWith("```"))
            {
                var firstNewline = json.IndexOf('\n');
                if (firstNewline >= 0) json = json[(firstNewline + 1)..];
                if (json.EndsWith("```")) json = json[..^3];
                json = json.Trim();
            }

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