using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
using JobsMedical.Web.Data;
using JobsMedical.Web.Models;
using Microsoft.EntityFrameworkCore;

namespace JobsMedical.Web.Services.Scraping;

public record SourceResult(string Source, int Fetched, int Queued, int Published, int Flagged, int Spam, int Duplicates);

public record IngestionSummary(List<SourceResult> Sources)
{
    public int TotalFetched => Sources.Sum(s => s.Fetched);
    public int TotalQueued => Sources.Sum(s => s.Queued);
    public int TotalPublished => Sources.Sum(s => s.Published);
    public int TotalFlagged => Sources.Sum(s => s.Flagged);
    public int TotalSpam => Sources.Sum(s => s.Spam);
    public int TotalDuplicates => Sources.Sum(s => s.Duplicates);
}

/// <summary>
/// The scrape engine. For every enabled source: dedupe by content hash → parse → rule-validate →
/// (optional) AI audit → decide. Decision depends on admin settings:
///   • spam → Discarded
///   • AI on: AI verdict drives approve/reject/review; approve + Automatic + AiAutoApprove → publish
///   • AI off: Automatic + confidence ≥ threshold → publish; else queue/flag
/// "Publish" resolves-or-creates an (unverified) facility and creates the Shift/JobOpening.
/// </summary>
public class IngestionService
{
    /// <summary>Applicant posts older than this (by the source's date, or a Persian "time ago"
    /// phrase in the text) are skipped at ingest — availability goes stale fast.</summary>
    private const int TalentMaxAgeDays = 7;

    private readonly AppDbContext _db;
    private readonly IEnumerable<IListingSource> _sources;
    private readonly IListingParser _parser;
    private readonly ListingValidator _validator;
    private readonly IAiAuditor _ai;
    private readonly SettingsService _settings;
    private readonly ILogger<IngestionService> _log;

    public IngestionService(AppDbContext db, IEnumerable<IListingSource> sources, IListingParser parser,
        ListingValidator validator, IAiAuditor ai, SettingsService settings, ILogger<IngestionService> log)
    {
        _db = db; _sources = sources; _parser = parser; _validator = validator;
        _ai = ai; _settings = settings; _log = log;
    }

    public IReadOnlyList<string> SourceNames => _sources.Select(s => s.Name).ToList();

    /// <summary>Shared placeholder facility name for unnamed ads — kept identical to
    /// Review.ResolveFacilityIdAsync so the auto-publish and manual-review flows reuse ONE record.</summary>
    private const string UnknownFacilityName = "نامشخص / ثبت نشده";

    public async Task<IngestionSummary> RunAsync(CancellationToken ct = default)
    {
        var settings = await _settings.GetAsync();
        var roles = await _db.Roles.ToListAsync(ct);
        var cities = await _db.Cities.ToListAsync(ct);
        var districts = await _db.Districts.ToListAsync(ct);
        var facilities = await _db.Facilities.ToListAsync(ct);   // fuzzy-matched + grown as we create
        var roleNames = roles.Select(r => r.Name).ToList();
        var cityNames = cities.Select(c => c.Name).ToList();
        var districtNames = districts.Select(d => d.Name).ToList();

        var results = new List<SourceResult>();

        foreach (var source in _sources)
        {
            int fetched = 0, queued = 0, published = 0, flagged = 0, spam = 0, dupes = 0;
            IReadOnlyList<ScrapedItem> items;
            try { items = await source.FetchAsync(settings, ct); }
            catch (Exception ex) { _log.LogError(ex, "Source {Source} failed", source.Name); continue; }
            if (items.Count == 0) continue;   // disabled/unconfigured source

            foreach (var item in items)
            {
                fetched++;
                var hash = Hash(item.RawText);
                var existing = await _db.RawListings.FirstOrDefaultAsync(r => r.ContentHash == hash, ct);
                if (existing is not null)
                {
                    // Best-effort geo retry: coords are normally captured only on first ingest, but a
                    // re-fetch may now expose a map center the first fetch lacked (Divar can fail-soft to
                    // null on a bad response / out-of-bbox). Backfill the cached row when this fetch has
                    // coords and the row has none, so an item still sitting in the queue can be placed on
                    // the map when an admin publishes it. (A full refresh is the purge-and-reingest flow.)
                    if (existing.Lat is null && item.Lat is not null) { existing.Lat = item.Lat; existing.Lng = item.Lng; }
                    dupes++; continue;
                }

                var parsed = _parser.Parse(item.RawText, roleNames, cityNames, districtNames);
                var val = _validator.Validate(item.RawText, parsed);

                // Drop STALE applicant («آماده به کار») posts — a person's availability goes cold fast.
                // Age = the source's real timestamp, else a Persian "time ago" phrase in the text
                // (Divar embeds «۲ هفته پیش»…). Recorded as Discarded (keeps the dedupe hash + audit
                // trail; no AI spend). Shifts/jobs are NOT aged out — their dates are in the future.
                if (parsed.Kind == ListingKind.Talent && PostAgeDays(item) is int age && age > TalentMaxAgeDays)
                {
                    _db.RawListings.Add(new RawListing
                    {
                        SourceChannel = item.Source, SourceUrl = item.SourceUrl, RawText = item.RawText.Trim(),
                        ContentHash = hash, Confidence = 0, Status = RawListingStatus.Discarded,
                        ValidationNotes = $"آماده‌به‌کارِ قدیمی ({age} روز) — نادیده گرفته شد",
                        Lat = item.Lat, Lng = item.Lng,
                    });
                    spam++; continue;
                }

                AiAuditResult? ai = null;
                if (settings.AiEnabled && !val.IsSpam)
                    ai = await _ai.AuditAsync(item.RawText, settings, ct);

                var (status, reason, confidence) = Decide(settings, val, ai);

                var raw = new RawListing
                {
                    SourceChannel = item.Source,
                    SourceUrl = item.SourceUrl,
                    RawText = item.RawText.Trim(),
                    ContentHash = hash,
                    Confidence = confidence,
                    ValidationNotes = reason,
                    Status = status,
                    Lat = item.Lat, Lng = item.Lng,   // approx. map coords (Divar) → facility on publish
                };
                _db.RawListings.Add(raw);

                if (status == RawListingStatus.Normalized)
                {
                    try { Publish(parsed, ai, raw, roles, cities, districts, facilities); published++; }
                    catch (Exception ex) { _log.LogWarning(ex, "Auto-publish failed; queueing instead"); raw.Status = RawListingStatus.New; queued++; }
                }
                else if (status == RawListingStatus.New) queued++;
                else if (status == RawListingStatus.Flagged) flagged++;
                else spam++;
            }

            await _db.SaveChangesAsync(ct);
            results.Add(new SourceResult(source.Name, fetched, queued, published, flagged, spam, dupes));
            _log.LogInformation("Ingest {S}: fetched={F} queued={Q} published={P} flagged={Fl} spam={Sp} dupes={D}",
                source.Name, fetched, queued, published, flagged, spam, dupes);
        }

        var summary = new IngestionSummary(results);

        // Persist a run-log row so admins get a crawl history (with a per-source breakdown).
        if (results.Count > 0)
        {
            var detail = string.Join("؛ ", results.Select(r =>
                $"{r.Source}: یافت {r.Fetched}، صف {r.Queued}، منتشر {r.Published}، پرچم {r.Flagged}، اسپم {r.Spam}، تکراری {r.Duplicates}"));
            _db.IngestionRuns.Add(new IngestionRun
            {
                Fetched = summary.TotalFetched,
                Queued = summary.TotalQueued,
                Published = summary.TotalPublished,
                Flagged = summary.TotalFlagged,
                Spam = summary.TotalSpam,
                Duplicates = summary.TotalDuplicates,
                Detail = detail.Length > 2000 ? detail[..2000] : detail,
            });
            await _db.SaveChangesAsync(ct);
        }

        return summary;
    }

    private static (RawListingStatus status, string? reason, int confidence) Decide(
        AppSetting s, ValidationResult val, AiAuditResult? ai)
    {
        var notes = val.Issues.Count > 0 ? string.Join("؛ ", val.Issues) : null;

        if (val.IsSpam)
            return (RawListingStatus.Discarded, Join("اسپم", notes), val.Confidence);

        if (ai is not null)
        {
            var aiNote = Join($"AI: {ai.Decision} ({ai.Confidence}٪)" + (ai.Reason is null ? "" : $" — {ai.Reason}"), notes);
            if (ai.Reject) return (RawListingStatus.Discarded, aiNote, ai.Confidence);
            if (ai.Approve)
            {
                // MEDICAL GATE: the rule-validator's medical signal vetoes an AI approval. The AI can
                // hallucinate (e.g. approved a GeekVape product ad 95% as a «پرستار» job) — when our
                // own keyword/role check sees nothing clinical, never auto-publish; send to review.
                if (!val.LooksMedical)
                    return (RawListingStatus.Flagged, Join("هوش مصنوعی تأیید کرد ولی نشانهٔ کادر درمان یافت نشد — بررسی دستی", aiNote), ai.Confidence);
                return (s.Mode == IngestionMode.Automatic && s.AiAutoApprove
                    ? RawListingStatus.Normalized : RawListingStatus.New, aiNote, ai.Confidence);
            }
            return (RawListingStatus.Flagged, aiNote, ai.Confidence);  // review
        }

        if (!val.IsValid) return (RawListingStatus.Flagged, notes, val.Confidence);
        if (s.Mode == IngestionMode.Automatic && val.Confidence >= s.AutoPublishMinConfidence)
            return (RawListingStatus.Normalized, notes, val.Confidence);
        return (RawListingStatus.New, notes, val.Confidence);
    }

    private void Publish(ParsedListing parsed, AiAuditResult? ai, RawListing raw,
        List<Role> roles, List<City> cities, List<District> districts, List<Facility> facilities)
    {
        var d = ai?.Data;
        var cityName = d?.City ?? parsed.CityName;
        var districtName = d?.District ?? parsed.DistrictName;

        // One ad can name several roles («پرستار سالمند و کودک و همراه بیمار») — resolve them all
        // and publish one listing per role so each is browsable/filterable. Capped to avoid spam.
        // The AI's role (+ its category) is the trusted, possibly-new one; parser names are already
        // canonical matches. Unknown roles are CREATED (dynamic taxonomy), not dropped.
        var candidates = new List<(string name, string? category)>();
        if (!string.IsNullOrWhiteSpace(d?.Role)) candidates.Add((d!.Role!.Trim(), d.Category));
        foreach (var n in parsed.RoleNames) candidates.Add((n, null));
        if (parsed.RoleName is not null) candidates.Add((parsed.RoleName, null));

        var pubRoles = new List<Role>();
        foreach (var (name, category) in candidates)
        {
            if (string.IsNullOrWhiteSpace(name)) continue;
            var role = ResolveOrCreateRole(roles, name, category);
            if (!pubRoles.Contains(role)) pubRoles.Add(role);
            if (pubRoles.Count >= 4) break;
        }
        if (pubRoles.Count == 0) pubRoles.Add(roles.First());

        var city = cities.FirstOrDefault(c => c.Name == cityName)
                   ?? cities.FirstOrDefault(c => c.IsActive) ?? cities.First();
        var district = districts.FirstOrDefault(x => x.Name == districtName && x.CityId == city.Id);

        var kindStr = (d?.Kind ?? parsed.Kind.ToString()).ToLowerInvariant();

        // «آماده به کار» — a worker offering themselves. No facility involved.
        if (parsed.Kind == ListingKind.Talent || kindStr.Contains("talent") || kindStr.Contains("آماده"))
        {
            // Prefer the AI's tags when present, else the heuristic parser.
            var tPay = d?.PayAmount ?? parsed.PayAmount;
            var tShare = d?.SharePercent ?? parsed.SharePercent;
            foreach (var role in pubRoles)
                _db.TalentListings.Add(new TalentListing
                {
                    Role = role, City = city, DistrictId = district?.Id,
                    PersonName = !string.IsNullOrWhiteSpace(d?.PersonName) ? d!.PersonName!.Trim() : parsed.PersonName,
                    YearsExperience = d?.YearsExperience ?? parsed.YearsExperience,
                    IsLicensed = d?.IsLicensed ?? parsed.IsLicensed,
                    AreaNote = parsed.AreaNote,
                    Availability = MapEmployment(d?.EmploymentType, parsed.EmploymentType),
                    Gender = parsed.Gender,
                    PayType = tShare is not null && tPay is null ? PayType.Percentage
                              : tPay is null ? PayType.Negotiable : PayType.PerShift,
                    PayAmount = tPay, SharePercent = tShare,
                    Phone = !string.IsNullOrWhiteSpace(d?.Phone) ? d!.Phone!.Trim() : parsed.Phone,
                    Description = raw.RawText,
                    Status = ShiftStatus.Open, Source = ShiftSource.Aggregated, SourceUrl = raw.SourceUrl,
                    Contacts = BuildContacts(d, parsed),   // fresh instances per listing
                    Tags = BuildTags(parsed, d, role, city),
                });
            raw.Status = RawListingStatus.Normalized;
            return;
        }

        // Never surface the crawl source (e.g. «مدجابز») in a public facility name. An unnamed ad
        // falls back to ONE shared placeholder (same string as the manual-review flow, so both
        // pipelines reuse a single record). That placeholder is shared by every unnamed ad in a
        // city, so it must NEVER receive a single ad's fuzzy coords — that would mis-place dozens of
        // unrelated listings on the map and in «near me». Mirrors Review.ResolveFacilityIdAsync.
        bool unnamed = string.IsNullOrWhiteSpace(d?.FacilityName) && string.IsNullOrWhiteSpace(parsed.FacilityName);
        var facilityName = !string.IsNullOrWhiteSpace(d?.FacilityName) ? d!.FacilityName!.Trim()
            : !string.IsNullOrWhiteSpace(parsed.FacilityName) ? parsed.FacilityName!.Trim()
            : UnknownFacilityName;
        // Reuse an existing facility (exact or Persian-aware fuzzy match) before creating a new one.
        var facility = FacilityMatcher.FindBest(facilities, facilityName, city.Id);
        if (facility is null)
        {
            facility = new Facility
            {
                Name = facilityName, Type = FacilityType.Clinic, City = city, DistrictId = district?.Id,
                Phone = !string.IsNullOrWhiteSpace(d?.Phone) ? d!.Phone!.Trim() : parsed.Phone, IsVerified = false,
                Lat = unnamed ? null : raw.Lat, Lng = unnamed ? null : raw.Lng,   // approx. Divar map center
            };
            _db.Facilities.Add(facility);
            facilities.Add(facility);   // so later listings in this run match it too
        }
        else if (!unnamed && facility.Lat is null && facility.Lng is null && raw.Lat is not null)
        {
            // Backfill coords only when the matched (real, named) facility has none — never overwrite a
            // real (employer-set or verified) location with Divar's fuzzy point.
            facility.Lat = raw.Lat; facility.Lng = raw.Lng;
        }

        if (kindStr.Contains("job") || kindStr.Contains("استخدام"))
        {
            foreach (var role in pubRoles)
                _db.JobOpenings.Add(new JobOpening
                {
                    Facility = facility, Role = role,
                    Title = !string.IsNullOrWhiteSpace(d?.Title) && pubRoles.Count == 1 ? d!.Title!.Trim() : $"استخدام {role.Name}",
                    EmploymentType = MapEmployment(d?.EmploymentType, parsed.EmploymentType),
                    SalaryMin = parsed.PayAmount,
                    Description = raw.RawText, Status = ShiftStatus.Open, Source = ShiftSource.Aggregated,
                    SourceUrl = raw.SourceUrl,
                    Contacts = BuildContacts(d, parsed),   // the ad's OWN number(s) — fresh per listing
                });
        }
        else
        {
            var st = MapShiftType(d?.ShiftType, parsed.ShiftType);
            var (start, end) = DefaultTimes(st);
            foreach (var role in pubRoles)
                _db.Shifts.Add(new Shift
                {
                    Facility = facility, Role = role,
                    Date = DateOnly.FromDateTime(DateTime.UtcNow).AddDays(1),
                    StartTime = start, EndTime = end, ShiftType = st,
                    SpecialtyRequired = role.Name, Description = raw.RawText,
                    PayType = parsed.SharePercent is not null && parsed.PayAmount is null ? PayType.Percentage
                              : parsed.PayAmount is null ? PayType.Negotiable : PayType.PerShift,
                    PayAmount = parsed.PayAmount, SharePercent = parsed.SharePercent,
                    Status = ShiftStatus.Open, Source = ShiftSource.Aggregated, SourceUrl = raw.SourceUrl,
                    Contacts = BuildContacts(d, parsed),   // the ad's OWN number(s) — fresh per listing
                });
        }
        raw.Status = RawListingStatus.Normalized;
    }

    /// <summary>Space-separated searchable tags: parsed cert/skill tags + AI-detected skills/requirements
    /// + this listing's role/category + city. Drives deep search and tag chips on the applicant card.</summary>
    private static string BuildTags(ParsedListing parsed, AiStructured? d, Role role, City city)
    {
        var tags = new List<string>(parsed.Tags) { role.Name, role.Category, city.Name };
        if (d?.Tags is not null)
            tags.AddRange(d.Tags.Where(t => !string.IsNullOrWhiteSpace(t)).Select(t => t.Trim()));
        return string.Join(" ", tags.Where(t => !string.IsNullOrWhiteSpace(t)).Distinct());
    }

    /// <summary>Resolve a role name to an existing Role; if it's genuinely new, create it (dynamic
    /// taxonomy). Matching is layered so a differently-worded-but-same-meaning role maps to the
    /// canonical one instead of forking: (1) exact normalized name, (2) synonym/abbreviation alias
    /// → canonical (دکتر→پزشک عمومی، نرس→پرستار…), (3) create. Only TRUE synonyms collapse — real
    /// sub-specialties («پرستار ICU») stay distinct on purpose.</summary>
    private Role ResolveOrCreateRole(List<Role> roles, string name, string? category)
    {
        var norm = NormalizeFa(name);

        // (1) Already a known role (same word or spelling variant).
        var match = roles.FirstOrDefault(r => NormalizeFa(r.Name) == norm);
        if (match is not null) return match;

        // (2) A synonym of a canonical role → use that role; don't create a duplicate.
        if (RoleAliases.TryGetValue(norm, out var canonical))
        {
            var canonNorm = NormalizeFa(canonical);
            var aliased = roles.FirstOrDefault(r => NormalizeFa(r.Name) == canonNorm);
            if (aliased is not null) return aliased;
            name = canonical; norm = canonNorm;   // canonical not seeded yet → create under its proper name
        }

        // (3) Genuinely new role — create it under a canonical-resolved category.
        var created = new Role
        {
            Name = Clamp(name.Trim(), 100),                  // respect Role.Name MaxLength(100)
            Category = Clamp(ResolveCategory(roles, category), 50),  // respect Role.Category MaxLength(50)
            IsActive = true,
            SortOrder = (roles.Count == 0 ? 0 : roles.Max(r => r.SortOrder)) + 1,
        };
        _db.Roles.Add(created);
        roles.Add(created);   // reuse within this run (saved with the batch at end of source)
        _log.LogInformation("Ingestion introduced new role «{Role}» (category «{Category}») from AI.",
            created.Name, created.Category);
        return created;
    }

    /// <summary>Map an AI-suggested category to a canonical one: synonym alias first
    /// (پزشکی→پزشک، nursing→پرستار…), then any existing category that normalizes the same, else as-is.</summary>
    private static string ResolveCategory(List<Role> roles, string? category)
    {
        var raw = string.IsNullOrWhiteSpace(category) ? "سایر" : category!.Trim();
        // Resolve to a canonical first (synonym alias), then to whichever normalized form is the
        // matching target. Crucially, ALWAYS prefer a category string already stored on a role — even
        // after an alias maps to a canonical — so we never fork a second variant of the same group.
        var target = CategoryAliases.TryGetValue(NormalizeFa(raw), out var canonical) ? canonical : raw;
        var targetNorm = NormalizeFa(target);
        return roles.Select(r => r.Category)
            .FirstOrDefault(c => !string.IsNullOrWhiteSpace(c) && NormalizeFa(c) == targetNorm) ?? target;
    }

    // Synonyms/abbreviations → canonical ROLE name, so the AI naming a role differently maps onto an
    // existing role instead of forking the taxonomy. Keys are matched after NormalizeFa. Add freely.
    private static readonly Dictionary<string, string> RoleAliases = BuildAliasMap(new()
    {
        ["پزشک عمومی"]             = new[] { "دکتر", "طبیب", "پزشک", "جی پی", "gp", "general practitioner" },
        ["پزشک متخصص"]            = new[] { "متخصص", "فوق تخصص", "اسپشالیست", "specialist" },
        ["پرستار"]                 = new[] { "نرس", "nurse", "پرستاری", "کارشناس پرستاری" },
        ["پرستار سالمندان"]        = new[] { "مراقب سالمند", "مراقب سالمندان", "پرستار سالمند", "نگهدار سالمند", "مراقبت سالمند" },
        ["ماما"]                   = new[] { "مامایی", "کارشناس مامایی", "midwife" },
        ["تکنسین اتاق عمل"]        = new[] { "اتاق عمل", "اسکراب", "scrub", "تکنولوژیست اتاق عمل" },
        ["تکنسین فوریت‌های پزشکی"]  = new[] { "فوریت پزشکی", "تکنسین اورژانس", "پارامدیک", "paramedic", "emt", "اورژانس ۱۱۵" },
        ["کارشناس آزمایشگاه"]      = new[] { "علوم آزمایشگاهی", "تکنسین آزمایشگاه", "آزمایشگاهی", "لابراتوار", "lab", "laboratory" },
        ["دندانپزشک"]             = new[] { "دندان پزشک", "دندون پزشک", "dentist" },
    });

    // Synonyms → canonical CATEGORY (the role-group used for filters/chips).
    private static readonly Dictionary<string, string> CategoryAliases = BuildAliasMap(new()
    {
        ["پزشک"]      = new[] { "دکتر", "طبیب", "doctor", "پزشکی" },
        ["پرستار"]    = new[] { "پرستاری", "nurse", "nursing" },
        ["ماما"]      = new[] { "مامایی", "midwifery" },
        ["تکنسین"]    = new[] { "تکنیسین", "تکنولوژیست", "technician", "کاردان فنی" },
        ["دندانپزشک"] = new[] { "دندان پزشک", "دندانپزشکی", "dental" },
    });

    /// <summary>Flatten {canonical → [synonyms]} into a {normalized synonym → canonical} lookup,
    /// also mapping each canonical's own normalized form to itself.</summary>
    private static Dictionary<string, string> BuildAliasMap(Dictionary<string, string[]> src)
    {
        var map = new Dictionary<string, string>();
        foreach (var (canonical, aliases) in src)
        {
            map[NormalizeFa(canonical)] = canonical;
            foreach (var a in aliases) map[NormalizeFa(a)] = canonical;
        }
        return map;
    }

    /// <summary>Normalize a Persian string for dedupe: unify Arabic/Persian ي→ی and ك→ک, drop ZWNJ,
    /// collapse whitespace, trim, lowercase (so Latin tags like "ICU"/"icu" also match).</summary>
    private static string NormalizeFa(string? s) => Regex.Replace(
        (s ?? "").Replace('ي', 'ی').Replace('ك', 'ک').Replace('‌', ' ').Trim(),
        @"\s+", " ").ToLowerInvariant();

    private static string Clamp(string s, int max) => s.Length <= max ? s : s[..max].Trim();

    /// <summary>Fresh ContactMethod rows for one talent listing (parser contacts + AI phone).</summary>
    private static List<ContactMethod> BuildContacts(AiStructured? d, ParsedListing parsed)
    {
        var contacts = parsed.Contacts
            .Select((c, i) => new ContactMethod { Type = c.Type, Value = c.Value, SortOrder = i })
            .ToList();
        if (!string.IsNullOrWhiteSpace(d?.Phone)
            && !contacts.Any(c => c.Type is ContactType.Mobile or ContactType.Phone))
            contacts.Insert(0, new ContactMethod { Type = ContactType.Mobile, Value = d!.Phone!.Trim(), SortOrder = -1 });
        return contacts;
    }

    private static ShiftType MapShiftType(string? ai, ShiftType? parsed) => (ai?.ToLowerInvariant()) switch
    {
        "day" => ShiftType.Day, "evening" => ShiftType.Evening, "night" => ShiftType.Night, "oncall" => ShiftType.OnCall,
        _ => parsed ?? ShiftType.Day,
    };

    private static EmploymentType MapEmployment(string? ai, EmploymentType? parsed) => (ai?.ToLowerInvariant()) switch
    {
        "parttime" => EmploymentType.PartTime, "contract" => EmploymentType.Contract,
        "plan" => EmploymentType.Plan, "fulltime" => EmploymentType.FullTime,
        _ => parsed ?? EmploymentType.FullTime,
    };

    private static (TimeOnly, TimeOnly) DefaultTimes(ShiftType t) => t switch
    {
        ShiftType.Day => (new TimeOnly(8, 0), new TimeOnly(14, 0)),
        ShiftType.Evening => (new TimeOnly(14, 0), new TimeOnly(20, 0)),
        ShiftType.Night => (new TimeOnly(20, 0), new TimeOnly(8, 0)),
        _ => (new TimeOnly(8, 0), new TimeOnly(8, 0)),
    };

    private static string? Join(string a, string? b) => string.IsNullOrEmpty(b) ? a : $"{a} | {b}";

    private static string Hash(string text)
    {
        var normalized = Regex.Replace((text ?? "").Trim(), @"\s+", " ");
        return Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(normalized))).ToLowerInvariant();
    }

    /// <summary>Age of a post in whole days — from the source's real timestamp when present, else a
    /// Persian "time ago" phrase in the text (Divar). Null when neither is available (= unknown age,
    /// so it's NOT filtered out).</summary>
    private static int? PostAgeDays(ScrapedItem item)
    {
        if (item.PostedAt is DateTime posted)
            return Math.Max(0, (int)Math.Floor((DateTime.UtcNow - posted).TotalDays));
        return HtmlUtil.AgeDaysFromPersianText(item.RawText);
    }
}