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

namespace InnovEnergy.App.Backend.Services;

public static class WeeklyReportService
{
    private static readonly string TmpReportDir = Environment.CurrentDirectory + "/tmp_report/";

    private static readonly ConcurrentDictionary<string, string> InsightCache = new();

    // Bump this version when the AI prompt changes to automatically invalidate old cache files
    private const string CacheVersion = "v2";

    /// <summary>
    /// Generates a full weekly report for the given installation.
    /// Caches the full report as JSON next to the xlsx. Cache is invalidated when xlsx is updated or CacheVersion changes.
    /// </summary>
    public static async Task<WeeklyReportResponse> GenerateReportAsync(long installationId, string installationName, string language = "en")
    {
        var xlsxPath  = TmpReportDir + installationId + ".xlsx";
        var cachePath = TmpReportDir + $"{installationId}_{language}_{CacheVersion}.cache.json";

        // Use cached report if xlsx hasn't changed since cache was written
        if (File.Exists(cachePath) && File.Exists(xlsxPath))
        {
            var xlsxModified  = File.GetLastWriteTimeUtc(xlsxPath);
            var cacheModified = File.GetLastWriteTimeUtc(cachePath);
            if (cacheModified > xlsxModified)
            {
                try
                {
                    var cached = JsonConvert.DeserializeObject<WeeklyReportResponse>(
                        await File.ReadAllTextAsync(cachePath));
                    if (cached != null)
                    {
                        Console.WriteLine($"[WeeklyReportService] Returning cached report for installation {installationId} ({language}).");
                        return cached;
                    }
                }
                catch
                {
                    // Cache corrupt — regenerate
                }
            }
        }

        var allDays = ExcelDataParser.Parse(xlsxPath);
        var report  = await GenerateReportFromDataAsync(allDays, installationName, language);

        // Write cache
        try
        {
            await File.WriteAllTextAsync(cachePath, JsonConvert.SerializeObject(report));
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[WeeklyReportService] Could not write cache: {ex.Message}");
        }

        return report;
    }

    /// <summary>
    /// Core report generation from daily data. Data-source agnostic.
    /// </summary>
    public static async Task<WeeklyReportResponse> GenerateReportFromDataAsync(
        List<DailyEnergyData> allDays, string installationName, string language = "en")
    {
        // Sort by date
        allDays = allDays.OrderBy(d => d.Date).ToList();

        // Split into previous week and current week
        List<DailyEnergyData> previousWeekDays;
        List<DailyEnergyData> currentWeekDays;

        if (allDays.Count > 7)
        {
            previousWeekDays = allDays.Take(allDays.Count - 7).ToList();
            currentWeekDays  = allDays.Skip(allDays.Count - 7).ToList();
        }
        else
        {
            previousWeekDays = new List<DailyEnergyData>();
            currentWeekDays  = allDays;
        }

        var currentSummary  = Summarize(currentWeekDays);
        var previousSummary = previousWeekDays.Count > 0 ? Summarize(previousWeekDays) : null;

        // Calculate key ratios for current week
        var selfSufficiency  = currentSummary.TotalConsumption > 0
            ? Math.Round((currentSummary.TotalConsumption - currentSummary.TotalGridImport) / currentSummary.TotalConsumption * 100, 1)
            : 0;

        var selfConsumption = currentSummary.TotalPvProduction > 0
            ? Math.Round((currentSummary.TotalPvProduction - currentSummary.TotalGridExport) / currentSummary.TotalPvProduction * 100, 1)
            : 0;

        var batteryEfficiency = currentSummary.TotalBatteryCharged > 0
            ? Math.Round(currentSummary.TotalBatteryDischarged / currentSummary.TotalBatteryCharged * 100, 1)
            : 0;

        var gridDependency = currentSummary.TotalConsumption > 0
            ? Math.Round(currentSummary.TotalGridImport / currentSummary.TotalConsumption * 100, 1)
            : 0;

        // Week-over-week changes
        var pvChange          = PercentChange(previousSummary?.TotalPvProduction, currentSummary.TotalPvProduction);
        var consumptionChange = PercentChange(previousSummary?.TotalConsumption, currentSummary.TotalConsumption);
        var gridImportChange  = PercentChange(previousSummary?.TotalGridImport, currentSummary.TotalGridImport);

        // AI insight
        var aiInsight = await GetAiInsightAsync(currentWeekDays, currentSummary, previousSummary,
            selfSufficiency, gridDependency, batteryEfficiency, installationName, language);

        return new WeeklyReportResponse
        {
            InstallationName        = installationName,
            PeriodStart             = currentWeekDays.First().Date,
            PeriodEnd               = currentWeekDays.Last().Date,
            CurrentWeek             = currentSummary,
            PreviousWeek            = previousSummary,
            SelfSufficiencyPercent  = selfSufficiency,
            SelfConsumptionPercent  = selfConsumption,
            BatteryEfficiencyPercent = batteryEfficiency,
            GridDependencyPercent   = gridDependency,
            PvChangePercent          = pvChange,
            ConsumptionChangePercent = consumptionChange,
            GridImportChangePercent  = gridImportChange,
            DailyData               = allDays,
            AiInsight               = aiInsight,
        };
    }

    private static WeeklySummary Summarize(List<DailyEnergyData> days) => new()
    {
        TotalPvProduction      = Math.Round(days.Sum(d => d.PvProduction), 1),
        TotalConsumption       = Math.Round(days.Sum(d => d.LoadConsumption), 1),
        TotalGridImport        = Math.Round(days.Sum(d => d.GridImport), 1),
        TotalGridExport        = Math.Round(days.Sum(d => d.GridExport), 1),
        TotalBatteryCharged    = Math.Round(days.Sum(d => d.BatteryCharged), 1),
        TotalBatteryDischarged = Math.Round(days.Sum(d => d.BatteryDischarged), 1),
    };

    private static double PercentChange(double? previous, double current)
    {
        if (previous is null or 0) return 0;
        return Math.Round((current - previous.Value) / previous.Value * 100, 1);
    }

    // ── Mistral AI Insight ──────────────────────────────────────────────

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

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

    private static async Task<string> GetAiInsightAsync(
        List<DailyEnergyData> currentWeek,
        WeeklySummary current,
        WeeklySummary? previous,
        double selfSufficiency,
        double gridDependency,
        double batteryEfficiency,
        string installationName,
        string language = "en")
    {
        var apiKey = Environment.GetEnvironmentVariable("MISTRAL_API_KEY");
        if (string.IsNullOrWhiteSpace(apiKey))
        {
            Console.WriteLine("[WeeklyReportService] MISTRAL_API_KEY not set — skipping AI insight.");
            return "AI insight unavailable (API key not configured).";
        }

        // Cache key: installation + period + language
        var cacheKey = $"{installationName}_{currentWeek.Last().Date}_{language}";
        if (InsightCache.TryGetValue(cacheKey, out var cached))
            return cached;

        // Build compact prompt
        var dayLines = string.Join("\n", currentWeek.Select(d =>
        {
            var dayName = DateTime.Parse(d.Date).ToString("ddd");
            return $"{dayName} {d.Date}: PV={d.PvProduction:F1} Load={d.LoadConsumption:F1} GridIn={d.GridImport:F1} GridOut={d.GridExport:F1} BattIn={d.BatteryCharged:F1} BattOut={d.BatteryDischarged:F1}";
        }));

        var comparison = previous != null
            ? $"vs Last week: PV {current.TotalPvProduction} vs {previous.TotalPvProduction}, Grid Import {current.TotalGridImport} vs {previous.TotalGridImport}, Consumption {current.TotalConsumption} vs {previous.TotalConsumption}"
            : "No previous week data available.";

        var solarSavings = Math.Round(current.TotalPvProduction - current.TotalGridExport, 1);

        var prompt = $@"You are an energy advisor for a SodistoreHome installation: ""{installationName}"".

Write exactly 4 bullet points (each on its own line starting with ""- ""). No bold markers, no asterisks, no markdown — plain text only.

IMPORTANT FORMAT RULE: Each bullet MUST start with a short title followed by a colon, then the description. Example: ""- Title label: Description text here."" Translate the title label into {LanguageName(language)} but always keep the ""Title: description"" structure.

1. Solar savings: this week the system saved {solarSavings} kWh from the grid. Explain what this means in simple terms (e.g. equivalent to X days of average household use, or roughly X CHF saved at ~0.27 CHF/kWh).
2. Best vs worst solar day: name the best and worst days with their PV kWh values. Mention likely weather reason.
3. Battery performance: was the battery well-utilized this week? Mention charge/discharge totals and any standout days.
4. Tip of the week: one specific, practical recommendation based on THIS week's patterns to save more energy or money.

Rules: Use actual day names and numbers. Keep each bullet to 1-2 sentences. Write for a homeowner, not an engineer. Do NOT use asterisks or any formatting marks.
IMPORTANT: Write your entire response in {LanguageName(language)}.

Daily data (kWh):
{dayLines}

Totals: PV={current.TotalPvProduction:F1} Load={current.TotalConsumption:F1} GridIn={current.TotalGridImport:F1} GridOut={current.TotalGridExport:F1} BattIn={current.TotalBatteryCharged:F1} BattOut={current.TotalBatteryDischarged:F1}
Solar used at home={solarSavings} kWh ({selfSufficiency}% of consumption covered by solar)
Battery-eff={batteryEfficiency}%
{comparison}";

        try
        {
            var requestBody = new
            {
                model    = "mistral-small-latest",
                messages = new[] { new { role = "user", content = prompt } },
                max_tokens  = 350,
                temperature = 0.3
            };

            var responseText = await MistralUrl
                .WithHeader("Authorization", $"Bearer {apiKey}")
                .PostJsonAsync(requestBody)
                .ReceiveString();

            var envelope = JsonConvert.DeserializeObject<dynamic>(responseText);
            var content  = (string?)envelope?.choices?[0]?.message?.content;

            if (!string.IsNullOrWhiteSpace(content))
            {
                var insight = content.Trim();
                InsightCache.TryAdd(cacheKey, insight);
                Console.WriteLine($"[WeeklyReportService] AI insight generated ({insight.Length} chars).");
                return insight;
            }
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[WeeklyReportService] Mistral error: {ex.Message}");
        }

        return "AI insight could not be generated at this time.";
    }
}