using InboxIntel.Application.Abstractions;
using InboxIntel.Application.DTOs;
using InboxIntel.Domain.Enums;
using InboxIntel.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

namespace InboxIntel.Infrastructure.Analytics;

public class AnalyticsService : IAnalyticsService
{
    private readonly AppDbContext _db;
    public AnalyticsService(AppDbContext db) => _db = db;

    public async Task<DashboardSummaryDto> GetDashboardAsync(Guid userId, CancellationToken ct = default)
    {
        var health = await GetInboxHealthAsync(userId, ct);
        var top = await GetTopSendersAsync(userId, 10, ct);
        var volume = await GetVolumeOverTimeAsync(userId, 90, ct);
        var attachments = await GetAttachmentBreakdownAsync(userId, ct);

        return new DashboardSummaryDto(
            health, health.TotalEmails, health.UnreadEmails, top, volume, attachments,
            health.EstimatedStorageBytes);
    }

    public async Task<InboxHealthDto> GetInboxHealthAsync(Guid userId, CancellationToken ct = default)
    {
        var emails = _db.Emails.Where(e => e.UserId == userId);
        var total = await emails.CountAsync(ct);
        var unread = await emails.CountAsync(e => e.IsUnread, ct);
        var newsletters = await emails.CountAsync(e => e.Category == EmailCategory.Newsletter, ct);
        var storage = total == 0 ? 0 : await emails.SumAsync(e => e.SizeEstimateBytes, ct);
        var safeToUnsub = await _db.UnsubscribeItems.CountAsync(u => u.UserId == userId, ct);

        // Health score: penalise high unread ratio and newsletter clutter.
        var unreadRatio = total == 0 ? 0 : (double)unread / total;
        var newsletterRatio = total == 0 ? 0 : (double)newsletters / total;
        var score = (int)Math.Round(100 * (1 - 0.6 * unreadRatio - 0.4 * newsletterRatio));
        score = Math.Clamp(score, 0, 100);

        var grade = score switch { >= 90 => "A", >= 80 => "B", >= 70 => "C", >= 60 => "D", _ => "F" };
        var recs = new List<string>();
        if (unreadRatio > 0.3) recs.Add($"You have {unread:N0} unread emails. Consider bulk-marking older ones as read.");
        if (newsletters > 50) recs.Add($"{newsletters:N0} newsletters detected. Review the safe-to-unsubscribe list.");
        if (storage > 1_000_000_000) recs.Add("Inbox storage exceeds 1 GB. Clean up large attachments.");
        if (recs.Count == 0) recs.Add("Your inbox is in good shape. Keep it up!");

        return new InboxHealthDto(score, grade, total, unread, newsletters, safeToUnsub, storage, recs);
    }

    public async Task<IReadOnlyList<SenderStatDto>> GetTopSendersAsync(Guid userId, int take = 20, CancellationToken ct = default)
    {
        return await _db.Senders
            .Where(s => s.UserId == userId)
            .OrderByDescending(s => s.EmailCount)
            .Take(take)
            .Select(s => new SenderStatDto(
                s.Id, s.Address, s.DisplayName, s.Domain!.Name, s.EmailCount, s.UnreadCount,
                s.TotalSizeBytes, s.HasUnsubscribe, s.LastReceivedUtc))
            .ToListAsync(ct);
    }

    public async Task<IReadOnlyList<TimeSeriesPointDto>> GetVolumeOverTimeAsync(Guid userId, int days = 90, CancellationToken ct = default)
    {
        var since = DateTimeOffset.UtcNow.AddDays(-days);
        var raw = await _db.Emails
            .Where(e => e.UserId == userId && e.SentAtUtc >= since)
            .GroupBy(e => e.SentAtUtc.Date)
            .Select(g => new { Day = g.Key, Count = g.Count() })
            .ToListAsync(ct);

        return raw.OrderBy(x => x.Day)
            .Select(x => new TimeSeriesPointDto(DateOnly.FromDateTime(x.Day), x.Count))
            .ToList();
    }

    public async Task<IReadOnlyList<CategoryHeatmapCellDto>> GetCategoryHeatmapAsync(Guid userId, CancellationToken ct = default)
    {
        var raw = await _db.Emails
            .Where(e => e.UserId == userId)
            .Select(e => new { e.SentAtUtc, e.Category })
            .ToListAsync(ct);

        return raw
            .GroupBy(x => new { x.Category, Dow = (int)x.SentAtUtc.DayOfWeek })
            .Select(g => new CategoryHeatmapCellDto(g.Key.Category.ToString(), g.Key.Dow, g.Count()))
            .ToList();
    }

    public async Task<IReadOnlyList<AttachmentBreakdownDto>> GetAttachmentBreakdownAsync(Guid userId, CancellationToken ct = default)
    {
        var raw = await _db.Attachments
            .Where(a => a.UserId == userId)
            .Select(a => new { a.MimeType, a.SizeBytes })
            .ToListAsync(ct);

        return raw
            .GroupBy(a => Bucket(a.MimeType))
            .Select(g => new AttachmentBreakdownDto(g.Key, g.Sum(x => x.SizeBytes), g.Count()))
            .OrderByDescending(x => x.TotalBytes)
            .ToList();
    }

    private static string Bucket(string? mime) => mime switch
    {
        null => "other",
        var m when m.StartsWith("image/") => "images",
        var m when m.StartsWith("video/") => "video",
        var m when m.StartsWith("audio/") => "audio",
        var m when m.Contains("pdf") => "pdf",
        var m when m.Contains("zip") || m.Contains("compressed") => "archives",
        var m when m.Contains("spreadsheet") || m.Contains("excel") => "spreadsheets",
        var m when m.Contains("word") || m.Contains("document") => "documents",
        _ => "other"
    };

    public async Task<SidebarCountsDto> GetSidebarCountsAsync(Guid userId, CancellationToken ct = default)
    {
        var emails = _db.Emails.Where(e => e.UserId == userId);

        var allMail = await emails.CountAsync(ct);
        var inbox = await emails.CountAsync(e => e.IsInInbox, ct);
        var unread = await emails.CountAsync(e => e.IsUnread, ct);
        var starred = await emails.CountAsync(e => e.IsStarred, ct);
        var trash = await emails.CountAsync(e => e.IsTrashed, ct);
        var large = await emails.CountAsync(e => e.SizeEstimateBytes > 5_000_000, ct);
        var cutoff = DateTimeOffset.UtcNow.AddYears(-1);
        var old = await emails.CountAsync(e => e.SentAtUtc < cutoff, ct);

        // Label-backed counts (SENT / DRAFT / SPAM are system Gmail labels)
        async Task<int> LabelCount(string gmailId)
        {
            var labelId = await _db.Labels
                .Where(l => l.UserId == userId && l.GmailLabelId == gmailId)
                .Select(l => (Guid?)l.Id)
                .FirstOrDefaultAsync(ct);
            return labelId.HasValue
                ? await _db.EmailLabels.CountAsync(el => el.LabelId == labelId.Value, ct)
                : 0;
        }

        var sent = await LabelCount("SENT");
        var drafts = await LabelCount("DRAFT");
        var spam = await LabelCount("SPAM");

        // Category → smart-folder slug mapping
        var catCounts = await emails
            .GroupBy(e => e.Category)
            .Select(g => new { Cat = g.Key, N = g.Count() })
            .ToListAsync(ct);

        int Cat(EmailCategory c) => catCounts.FirstOrDefault(x => x.Cat == c)?.N ?? 0;

        var smartFolders = new Dictionary<string, int>
        {
            ["automated"] = Cat(EmailCategory.Notification),
            ["finance"] = Cat(EmailCategory.Finance),
            ["social"] = Cat(EmailCategory.Social),
            ["shopping"] = Cat(EmailCategory.Shopping) + Cat(EmailCategory.Promotional),
            ["noreply"] = Cat(EmailCategory.Notification),
            ["gaming"] = Cat(EmailCategory.Gaming),
            ["sales"] = Cat(EmailCategory.SeasonalSales),
            ["ridesharing"] = Cat(EmailCategory.RideSharing),
            ["food"] = Cat(EmailCategory.FoodDelivery),
            ["wellness"] = Cat(EmailCategory.Wellness),
            // New categories
            ["travel"] = Cat(EmailCategory.Travel),
            ["subscriptions"] = Cat(EmailCategory.Subscriptions),
            ["parcels"] = Cat(EmailCategory.Parcels),
            ["recruitment"] = Cat(EmailCategory.Recruitment),
            ["events"] = Cat(EmailCategory.Events),
            ["security"] = Cat(EmailCategory.SecurityAlerts),
            ["healthcare"] = Cat(EmailCategory.Healthcare),
            ["education"] = Cat(EmailCategory.Education),
            ["news"] = Cat(EmailCategory.NewsMedia),
            ["property"] = Cat(EmailCategory.PropertyUtilities),
            ["charity"] = Cat(EmailCategory.Charity),
            ["government"] = Cat(EmailCategory.Government),
            ["crypto"] = Cat(EmailCategory.CryptoInvesting),
            ["family"] = Cat(EmailCategory.FamilySchool),
        };

        return new SidebarCountsDto(inbox, allMail, unread, starred, sent, drafts, trash, spam, large, old, smartFolders);
    }

    public async Task RefreshAggregatesAsync(Guid userId, CancellationToken ct = default)
    {
        var since = DateTimeOffset.UtcNow.AddDays(-365);
        var perDay = await _db.Emails
            .Where(e => e.UserId == userId && e.SentAtUtc >= since)
            .Select(e => new { e.SentAtUtc, e.IsUnread, e.Category, e.HasAttachments, e.SizeEstimateBytes })
            .ToListAsync(ct);

        var grouped = perDay.GroupBy(e => DateOnly.FromDateTime(e.SentAtUtc.UtcDateTime.Date));
        foreach (var g in grouped)
        {
            var existing = await _db.AnalyticsAggregates.FirstOrDefaultAsync(a => a.UserId == userId && a.Day == g.Key, ct);
            var agg = existing ?? new Domain.Entities.AnalyticsAggregate { UserId = userId, Day = g.Key };
            agg.TotalReceived = g.Count();
            agg.TotalUnread = g.Count(x => x.IsUnread);
            agg.NewsletterCount = g.Count(x => x.Category == EmailCategory.Newsletter);
            agg.WithAttachments = g.Count(x => x.HasAttachments);
            agg.TotalSizeBytes = g.Sum(x => x.SizeEstimateBytes);
            if (existing is null) _db.AnalyticsAggregates.Add(agg);
        }
        await _db.SaveChangesAsync(ct);
    }
}