using ZB.MOM.WW.ScadaBridge.Commons.Entities.ExternalSystems;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.InboundApi;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Notifications;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Scripts;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Transport;

namespace ZB.MOM.WW.ScadaBridge.Transport.Export;

/// <summary>
/// Expands an <see cref="ExportSelection"/> into the full set of entities that
/// must be in the bundle for the selection to be self-consistent. Walks the
/// dependency edges documented in §6.1 of the Transport design doc:
/// <list type="bullet">
///   <item>Template composes Template (via TemplateComposition.ComposedTemplateId).</item>
///   <item>Template references SharedScript (by name, scanned in script bodies).</item>
///   <item>Template references ExternalSystem (by name, scanned in script bodies + attribute DataSourceReference).</item>
///   <item>ApiMethod references SharedScript (by name, scanned in ApiMethod.Script).</item>
///   <item>Selected Template's folder chain (ancestor folders included).</item>
///   <item>ExternalSystemDefinition pulls its ExternalSystemMethods.</item>
/// </list>
/// Templates are returned topologically sorted (base-before-derived) via Kahn's
/// algorithm so importers can apply them in order.
/// <para>
/// M8 adds site/instance-scoped expansion: selecting a site pulls its
/// <c>DataConnection</c>s and <c>Instance</c>s; selecting an instance (with
/// <see cref="ExportSelection.IncludeDependencies"/>) pulls its owning site, the
/// data connections it binds, and feeds its template into the existing template
/// closure so the template/shared-script/external-system graph expands too.
/// </para>
/// </summary>
public sealed class DependencyResolver
{
    private readonly ITemplateEngineRepository _templates;
    private readonly IExternalSystemRepository _externalSystems;
    private readonly INotificationRepository _notifications;
    private readonly IInboundApiRepository _inboundApi;
    private readonly ISiteRepository _siteRepository;

    /// <summary>Initializes a new instance of <see cref="DependencyResolver"/>.</summary>
    /// <param name="templates">Repository for template, instance and shared script access.</param>
    /// <param name="externalSystems">Repository for external system definitions and methods.</param>
    /// <param name="notifications">Repository for notification lists and SMTP configurations.</param>
    /// <param name="inboundApi">Repository for inbound API keys and methods.</param>
    /// <param name="siteRepository">Repository for sites and site-scoped data connections.</param>
    public DependencyResolver(
        ITemplateEngineRepository templates,
        IExternalSystemRepository externalSystems,
        INotificationRepository notifications,
        IInboundApiRepository inboundApi,
        ISiteRepository siteRepository)
    {
        _templates = templates ?? throw new ArgumentNullException(nameof(templates));
        _externalSystems = externalSystems ?? throw new ArgumentNullException(nameof(externalSystems));
        _notifications = notifications ?? throw new ArgumentNullException(nameof(notifications));
        _inboundApi = inboundApi ?? throw new ArgumentNullException(nameof(inboundApi));
        _siteRepository = siteRepository ?? throw new ArgumentNullException(nameof(siteRepository));
    }

    /// <summary>Expands the selection into a fully self-consistent set of entities for bundling.</summary>
    /// <param name="selection">The user's export selection specifying which entities to include.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>A <see cref="ResolvedExport"/> with all transitively required entities.</returns>
    public async Task<ResolvedExport> ResolveAsync(ExportSelection selection, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(selection);

        // ---- Seed: fetch the directly-selected entities ----
        var templates = new Dictionary<int, Template>();
        foreach (var id in selection.TemplateIds.Distinct())
        {
            var t = await _templates.GetTemplateWithChildrenAsync(id, ct).ConfigureAwait(false);
            if (t is not null) templates[t.Id] = t;
        }

        var sharedScripts = new Dictionary<int, SharedScript>();
        foreach (var id in selection.SharedScriptIds.Distinct())
        {
            var s = await _templates.GetSharedScriptByIdAsync(id, ct).ConfigureAwait(false);
            if (s is not null) sharedScripts[s.Id] = s;
        }

        var externalSystems = new Dictionary<int, ExternalSystemDefinition>();
        foreach (var id in selection.ExternalSystemIds.Distinct())
        {
            var es = await _externalSystems.GetExternalSystemByIdAsync(id, ct).ConfigureAwait(false);
            if (es is not null) externalSystems[es.Id] = es;
        }

        var dbConnections = new Dictionary<int, DatabaseConnectionDefinition>();
        foreach (var id in selection.DatabaseConnectionIds.Distinct())
        {
            var db = await _externalSystems.GetDatabaseConnectionByIdAsync(id, ct).ConfigureAwait(false);
            if (db is not null) dbConnections[db.Id] = db;
        }

        var notificationLists = new Dictionary<int, NotificationList>();
        foreach (var id in selection.NotificationListIds.Distinct())
        {
            var nl = await _notifications.GetNotificationListByIdAsync(id, ct).ConfigureAwait(false);
            if (nl is not null) notificationLists[nl.Id] = nl;
        }

        var smtpConfigs = new Dictionary<int, SmtpConfiguration>();
        foreach (var id in selection.SmtpConfigurationIds.Distinct())
        {
            var sm = await _notifications.GetSmtpConfigurationByIdAsync(id, ct).ConfigureAwait(false);
            if (sm is not null) smtpConfigs[sm.Id] = sm;
        }

        // SMS provider configs (S10b): mirror the SMTP seed exactly — resolve each
        // selected id via the by-id repository accessor; missing ids are skipped.
        var smsConfigs = new Dictionary<int, SmsConfiguration>();
        foreach (var id in selection.SmsConfigurationIds.Distinct())
        {
            var sms = await _notifications.GetSmsConfigurationByIdAsync(id, ct).ConfigureAwait(false);
            if (sms is not null) smsConfigs[sms.Id] = sms;
        }

        // Inbound API keys are intentionally NOT resolved into the bundle: per the
        // inbound-API-key re-architecture (C4) keys are not transported between
        // environments. Only API methods travel.
        var apiMethods = new Dictionary<int, ApiMethod>();
        foreach (var id in selection.ApiMethodIds.Distinct())
        {
            var m = await _inboundApi.GetApiMethodByIdAsync(id, ct).ConfigureAwait(false);
            if (m is not null) apiMethods[m.Id] = m;
        }

        // ---- Seed: site/instance-scoped selection (M8) ----
        // sites/dataConnections/instances are keyed by surrogate id for dedup.
        var sites = new Dictionary<int, Site>();
        var dataConnections = new Dictionary<int, DataConnection>();
        var instances = new Dictionary<int, Instance>();

        // Selecting a SITE pulls its data connections and all of its instances. The
        // instance's overrides/bindings are loaded eagerly so the serializer can read
        // them off the entity navigation collections.
        foreach (var siteId in selection.SiteIds.Distinct())
        {
            var site = await _siteRepository.GetSiteByIdAsync(siteId, ct).ConfigureAwait(false);
            if (site is null) continue;
            sites[site.Id] = site;

            foreach (var conn in await _siteRepository.GetDataConnectionsBySiteIdAsync(site.Id, ct).ConfigureAwait(false))
            {
                dataConnections[conn.Id] = conn;
            }

            foreach (var siteInstance in await _siteRepository.GetInstancesBySiteIdAsync(site.Id, ct).ConfigureAwait(false))
            {
                if (instances.ContainsKey(siteInstance.Id)) continue;
                var loaded = await LoadInstanceWithChildrenAsync(siteInstance.Id, ct).ConfigureAwait(false);
                if (loaded is not null) instances[loaded.Id] = loaded;
            }
        }

        // Selecting an INSTANCE directly. Dedup against instances already pulled in
        // via their owning site above (a site + one of its instances selected together
        // must not double-add the instance).
        foreach (var instanceId in selection.InstanceIds.Distinct())
        {
            if (instances.ContainsKey(instanceId)) continue;
            var loaded = await LoadInstanceWithChildrenAsync(instanceId, ct).ConfigureAwait(false);
            if (loaded is not null) instances[loaded.Id] = loaded;
        }

        // ---- Dependency expansion ----
        if (selection.IncludeDependencies)
        {
            // Each gathered instance pulls in its owning site, the data connections it
            // binds, and (by feeding instance.TemplateId into the template dictionary)
            // its template — so the template/shared-script/external-system closure below
            // expands transitively over instance templates too.
            await ExpandSiteInstanceClosureAsync(instances, sites, dataConnections, templates, ct).ConfigureAwait(false);

            await ExpandTemplateClosureAsync(templates, ct).ConfigureAwait(false);
            await ExpandSharedScriptsFromTemplatesAsync(templates, sharedScripts, ct).ConfigureAwait(false);
            await ExpandSharedScriptsFromApiMethodsAsync(apiMethods, sharedScripts, ct).ConfigureAwait(false);
            await ExpandExternalSystemsFromTemplatesAsync(templates, externalSystems, ct).ConfigureAwait(false);
        }

        // ExternalSystemMethods always travel with their parent ExternalSystem.
        var externalSystemMethods = new List<ExternalSystemMethod>();
        foreach (var es in externalSystems.Values.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            var methods = await _externalSystems
                .GetMethodsByExternalSystemIdAsync(es.Id, ct)
                .ConfigureAwait(false);
            externalSystemMethods.AddRange(methods);
        }

        // Folder ancestor chain — always pull, regardless of IncludeDependencies,
        // so the imported tree never references missing parents.
        var folders = await ResolveFolderChainAsync(templates.Values, ct).ConfigureAwait(false);

        // ---- Topological sort of templates (base-before-derived) ----
        var orderedTemplates = TopologicallySortTemplates(templates.Values);

        // ---- Deterministic site/instance ordering (M8) ----
        // siteId → SiteIdentifier map: every connection's/instance's owning site lands
        // in `sites` after closure expansion, so ordering + dependsOn edges resolve names.
        var siteIdentifierById = sites.Values.ToDictionary(s => s.Id, s => s.SiteIdentifier);

        // I1: when an instance/data-connection is selected directly with
        // IncludeDependencies=false, its owning site is not packed (so it never
        // lands in `sites`) and the manifest dep-edge would degrade to the raw id
        // (Site:<rawId>) via SiteIdentifierOf's fallback. Resolve the identifier
        // for any referenced-but-unpacked owning site so the manifest reads
        // Site:<identifier> regardless of the deps flag — readability only, the
        // site row itself stays out of the bundle.
        var referencedSiteIds = instances.Values.Select(i => i.SiteId)
            .Concat(dataConnections.Values.Select(c => c.SiteId))
            .Distinct()
            .Where(id => !siteIdentifierById.ContainsKey(id));
        foreach (var siteId in referencedSiteIds)
        {
            var site = await _siteRepository.GetSiteByIdAsync(siteId, ct).ConfigureAwait(false);
            if (site is not null) siteIdentifierById[site.Id] = site.SiteIdentifier;
        }

        var orderedSites = sites.Values
            .OrderBy(s => s.SiteIdentifier, StringComparer.Ordinal)
            .ToList();
        var orderedDataConnections = dataConnections.Values
            .OrderBy(c => SiteIdentifierOf(c.SiteId, siteIdentifierById), StringComparer.Ordinal)
            .ThenBy(c => c.Name, StringComparer.Ordinal)
            .ToList();
        var orderedInstances = instances.Values
            .OrderBy(i => i.UniqueName, StringComparer.Ordinal)
            .ToList();

        // ---- Build deterministic content manifest ----
        var manifest = BuildContentManifest(
            folders,
            orderedTemplates,
            sharedScripts.Values,
            externalSystems.Values,
            externalSystemMethods,
            dbConnections.Values,
            notificationLists.Values,
            smtpConfigs.Values,
            smsConfigs.Values,
            apiMethods.Values,
            orderedSites,
            orderedDataConnections,
            orderedInstances,
            siteIdentifierById,
            templates);

        return new ResolvedExport(
            TemplateFolders: folders,
            Templates: orderedTemplates,
            SharedScripts: sharedScripts.Values.OrderBy(s => s.Name, StringComparer.Ordinal).ToList(),
            ExternalSystems: externalSystems.Values.OrderBy(e => e.Name, StringComparer.Ordinal).ToList(),
            ExternalSystemMethods: externalSystemMethods,
            DatabaseConnections: dbConnections.Values.OrderBy(d => d.Name, StringComparer.Ordinal).ToList(),
            NotificationLists: notificationLists.Values.OrderBy(n => n.Name, StringComparer.Ordinal).ToList(),
            SmtpConfigs: smtpConfigs.Values.OrderBy(s => s.Host, StringComparer.Ordinal).ToList(),
            ApiMethods: apiMethods.Values.OrderBy(a => a.Name, StringComparer.Ordinal).ToList(),
            ContentManifest: manifest)
        {
            Sites = orderedSites,
            DataConnections = orderedDataConnections,
            Instances = orderedInstances,
            // SMS (S10b): ordered by AccountSid — the natural key the importer matches
            // on, mirroring how SMTP is ordered by Host.
            SmsConfigs = smsConfigs.Values.OrderBy(s => s.AccountSid, StringComparer.Ordinal).ToList(),
        };
    }

    // ---- Instance child loading (M8) ----
    // Loads an instance and attaches its overrides/bindings onto the entity's own
    // navigation collections, so the serializer reads children off the entity (the
    // same shape central-config entities use). Returns null if the instance is gone.
    private async Task<Instance?> LoadInstanceWithChildrenAsync(int instanceId, CancellationToken ct)
    {
        var instance = await _templates.GetInstanceByIdAsync(instanceId, ct).ConfigureAwait(false);
        if (instance is null) return null;

        var attributeOverrides = await _templates.GetOverridesByInstanceIdAsync(instance.Id, ct).ConfigureAwait(false);
        var alarmOverrides = await _templates.GetAlarmOverridesByInstanceIdAsync(instance.Id, ct).ConfigureAwait(false);
        var nativeAlarmOverrides = await _templates.GetNativeAlarmSourceOverridesByInstanceIdAsync(instance.Id, ct).ConfigureAwait(false);
        var bindings = await _templates.GetBindingsByInstanceIdAsync(instance.Id, ct).ConfigureAwait(false);

        instance.AttributeOverrides = attributeOverrides.ToList();
        instance.AlarmOverrides = alarmOverrides.ToList();
        instance.NativeAlarmSourceOverrides = nativeAlarmOverrides.ToList();
        instance.ConnectionBindings = bindings.ToList();
        return instance;
    }

    // ---- Site/instance closure (M8) ----
    // For every gathered instance: ensure its owning Site is in the bundle, include
    // the DataConnections it binds (via ConnectionBinding.DataConnectionId resolved
    // within the instance's site, plus NativeAlarmSourceOverride.ConnectionNameOverride
    // resolved by name within that site), and feed its TemplateId into the template
    // dictionary so the template closure expands over it.
    private async Task ExpandSiteInstanceClosureAsync(
        Dictionary<int, Instance> instances,
        Dictionary<int, Site> sites,
        Dictionary<int, DataConnection> dataConnections,
        Dictionary<int, Template> templates,
        CancellationToken ct)
    {
        // Snapshot the instances: the loop only grows sites/dataConnections/templates,
        // never instances, so iterating a snapshot keeps the dictionary stable.
        foreach (var instance in instances.Values.ToList())
        {
            // 1. Owning site.
            if (!sites.ContainsKey(instance.SiteId))
            {
                var site = await _siteRepository.GetSiteByIdAsync(instance.SiteId, ct).ConfigureAwait(false);
                if (site is not null) sites[site.Id] = site;
            }

            // 2. Template → the existing template closure picks it up below.
            if (!templates.ContainsKey(instance.TemplateId))
            {
                var template = await _templates.GetTemplateWithChildrenAsync(instance.TemplateId, ct).ConfigureAwait(false);
                if (template is not null) templates[template.Id] = template;
            }

            // 3. Data connections the instance references, resolved within its site.
            //    Connection bindings reference connections by id; native-alarm-source
            //    overrides reference them by name — resolve both against the site set.
            var bindingConnectionIds = instance.ConnectionBindings
                .Select(b => b.DataConnectionId)
                .Where(id => !dataConnections.ContainsKey(id))
                .Distinct()
                .ToList();

            var referencedConnectionNames = instance.NativeAlarmSourceOverrides
                .Select(o => o.ConnectionNameOverride)
                .Where(n => !string.IsNullOrEmpty(n))
                .Select(n => n!)
                .ToHashSet(StringComparer.Ordinal);

            if (bindingConnectionIds.Count == 0 && referencedConnectionNames.Count == 0) continue;

            var siteConnections = await _siteRepository
                .GetDataConnectionsBySiteIdAsync(instance.SiteId, ct)
                .ConfigureAwait(false);

            foreach (var conn in siteConnections)
            {
                if (dataConnections.ContainsKey(conn.Id)) continue;
                if (bindingConnectionIds.Contains(conn.Id) || referencedConnectionNames.Contains(conn.Name))
                {
                    dataConnections[conn.Id] = conn;
                }
            }
        }
    }

    private static string SiteIdentifierOf(int siteId, IReadOnlyDictionary<int, string> siteIdentifierById) =>
        siteIdentifierById.TryGetValue(siteId, out var id) ? id : siteId.ToString();

    // ---- Template composition closure ----
    private async Task ExpandTemplateClosureAsync(Dictionary<int, Template> templates, CancellationToken ct)
    {
        var queue = new Queue<Template>(templates.Values);
        while (queue.Count > 0)
        {
            var current = queue.Dequeue();
            foreach (var comp in current.Compositions)
            {
                if (templates.ContainsKey(comp.ComposedTemplateId)) continue;
                var composed = await _templates
                    .GetTemplateWithChildrenAsync(comp.ComposedTemplateId, ct)
                    .ConfigureAwait(false);
                if (composed is null) continue;
                templates[composed.Id] = composed;
                queue.Enqueue(composed);
            }
        }
    }

    // ---- SharedScript pulls from template script bodies + attributes ----
    private async Task ExpandSharedScriptsFromTemplatesAsync(
        Dictionary<int, Template> templates,
        Dictionary<int, SharedScript> sharedScripts,
        CancellationToken ct)
    {
        var allShared = await _templates.GetAllSharedScriptsAsync(ct).ConfigureAwait(false);
        foreach (var shared in allShared)
        {
            if (sharedScripts.ContainsKey(shared.Id)) continue;
            if (TemplatesReferenceName(templates.Values, shared.Name))
            {
                sharedScripts[shared.Id] = shared;
            }
        }
    }

    // ---- SharedScript pulls from ApiMethod.Script bodies ----
    private async Task ExpandSharedScriptsFromApiMethodsAsync(
        Dictionary<int, ApiMethod> apiMethods,
        Dictionary<int, SharedScript> sharedScripts,
        CancellationToken ct)
    {
        if (apiMethods.Count == 0) return;
        var allShared = await _templates.GetAllSharedScriptsAsync(ct).ConfigureAwait(false);
        foreach (var shared in allShared)
        {
            if (sharedScripts.ContainsKey(shared.Id)) continue;
            if (apiMethods.Values.Any(m => ContainsIdentifier(m.Script, shared.Name)))
            {
                sharedScripts[shared.Id] = shared;
            }
        }
    }

    // ---- ExternalSystem pulls from template script/attribute bodies ----
    private async Task ExpandExternalSystemsFromTemplatesAsync(
        Dictionary<int, Template> templates,
        Dictionary<int, ExternalSystemDefinition> externalSystems,
        CancellationToken ct)
    {
        var allSystems = await _externalSystems.GetAllExternalSystemsAsync(ct).ConfigureAwait(false);
        foreach (var es in allSystems)
        {
            if (externalSystems.ContainsKey(es.Id)) continue;
            if (TemplatesReferenceName(templates.Values, es.Name))
            {
                externalSystems[es.Id] = es;
            }
        }
    }

    private static bool TemplatesReferenceName(IEnumerable<Template> templates, string name)
    {
        foreach (var t in templates)
        {
            foreach (var s in t.Scripts)
            {
                if (ContainsIdentifier(s.Code, name)) return true;
            }
            foreach (var a in t.Attributes)
            {
                if (a.DataSourceReference is not null && ContainsIdentifier(a.DataSourceReference, name)) return true;
                if (a.Value is not null && ContainsIdentifier(a.Value, name)) return true;
            }
        }
        return false;
    }

    /// <summary>
    /// Substring scan with word-boundary guarding: the name must not be a partial
    /// match of a longer identifier. Cheap, dependency-free, sufficient for the
    /// v1 export-time scan (callers can always over-include with explicit ids).
    /// </summary>
    private static bool ContainsIdentifier(string? haystack, string name)
    {
        if (string.IsNullOrEmpty(haystack) || string.IsNullOrEmpty(name)) return false;
        var idx = 0;
        while (true)
        {
            var hit = haystack.IndexOf(name, idx, StringComparison.Ordinal);
            if (hit < 0) return false;
            var before = hit == 0 ? '\0' : haystack[hit - 1];
            var afterIdx = hit + name.Length;
            var after = afterIdx >= haystack.Length ? '\0' : haystack[afterIdx];
            if (!IsIdentifierChar(before) && !IsIdentifierChar(after)) return true;
            idx = hit + 1;
        }
    }

    private static bool IsIdentifierChar(char c) => c == '_' || char.IsLetterOrDigit(c);

    // ---- Folder ancestor chain ----
    private async Task<IReadOnlyList<TemplateFolder>> ResolveFolderChainAsync(
        IEnumerable<Template> templates,
        CancellationToken ct)
    {
        var allFolders = await _templates.GetAllFoldersAsync(ct).ConfigureAwait(false);
        var byId = allFolders.ToDictionary(f => f.Id);

        var needed = new Dictionary<int, TemplateFolder>();
        foreach (var t in templates)
        {
            var fid = t.FolderId;
            while (fid is not null && byId.TryGetValue(fid.Value, out var folder))
            {
                if (!needed.TryAdd(folder.Id, folder)) break; // already walked this chain
                fid = folder.ParentFolderId;
            }
        }

        // Root-first ordering so importers create parents before children.
        return needed.Values
            .OrderBy(f => DepthOf(f, byId))
            .ThenBy(f => f.SortOrder)
            .ThenBy(f => f.Name, StringComparer.Ordinal)
            .ToList();
    }

    private static int DepthOf(TemplateFolder folder, IReadOnlyDictionary<int, TemplateFolder> byId)
    {
        var depth = 0;
        var current = folder;
        while (current.ParentFolderId is int pid && byId.TryGetValue(pid, out var parent))
        {
            depth++;
            current = parent;
            if (depth > 1024) break; // defensive: folder graph is acyclic by schema
        }
        return depth;
    }

    // ---- Kahn's algorithm: order templates base-before-derived ----
    /// <summary>Sorts templates in base-before-derived order using Kahn's algorithm.</summary>
    /// <param name="templates">The templates to sort; must form an acyclic composition graph.</param>
    /// <returns>Templates sorted so composed (base) templates appear before their composing (derived) templates.</returns>
    internal static List<Template> TopologicallySortTemplates(IEnumerable<Template> templates)
    {
        // Edge: composed --> composing (composed must appear first).
        var nodes = templates.ToDictionary(t => t.Id);
        var inDegree = nodes.ToDictionary(kv => kv.Key, _ => 0);
        var outEdges = nodes.ToDictionary(kv => kv.Key, _ => new List<int>());

        foreach (var t in nodes.Values)
        {
            foreach (var comp in t.Compositions)
            {
                if (!nodes.ContainsKey(comp.ComposedTemplateId)) continue;
                outEdges[comp.ComposedTemplateId].Add(t.Id);
                inDegree[t.Id]++;
            }
        }

        var queue = new Queue<int>(
            inDegree.Where(kv => kv.Value == 0)
                    .OrderBy(kv => nodes[kv.Key].Name, StringComparer.Ordinal)
                    .Select(kv => kv.Key));

        var result = new List<Template>(nodes.Count);
        while (queue.Count > 0)
        {
            var id = queue.Dequeue();
            result.Add(nodes[id]);
            foreach (var next in outEdges[id].OrderBy(x => nodes[x].Name, StringComparer.Ordinal))
            {
                if (--inDegree[next] == 0) queue.Enqueue(next);
            }
        }

        if (result.Count != nodes.Count)
            throw new InvalidOperationException("Template composition graph is cyclic");
        return result;
    }

    private static IReadOnlyList<ManifestContentEntry> BuildContentManifest(
        IReadOnlyList<TemplateFolder> folders,
        IReadOnlyList<Template> templates,
        IEnumerable<SharedScript> sharedScripts,
        IEnumerable<ExternalSystemDefinition> externalSystems,
        IEnumerable<ExternalSystemMethod> externalSystemMethods,
        IEnumerable<DatabaseConnectionDefinition> dbConnections,
        IEnumerable<NotificationList> notificationLists,
        IEnumerable<SmtpConfiguration> smtpConfigs,
        IEnumerable<SmsConfiguration> smsConfigs,
        IEnumerable<ApiMethod> apiMethods,
        IReadOnlyList<Site> sites,
        IReadOnlyList<DataConnection> dataConnections,
        IReadOnlyList<Instance> instances,
        IReadOnlyDictionary<int, string> siteIdentifierById,
        IReadOnlyDictionary<int, Template> templatesById)
    {
        var entries = new List<ManifestContentEntry>();

        foreach (var f in folders)
        {
            entries.Add(new ManifestContentEntry("TemplateFolder", f.Name, 1, Array.Empty<string>()));
        }
        foreach (var t in templates)
        {
            var deps = t.Compositions
                .Select(c => $"Template:{(templates.FirstOrDefault(x => x.Id == c.ComposedTemplateId)?.Name ?? c.ComposedTemplateId.ToString())}")
                .OrderBy(x => x, StringComparer.Ordinal)
                .ToList();
            entries.Add(new ManifestContentEntry("Template", t.Name, 1, deps));
        }
        foreach (var s in sharedScripts.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("SharedScript", s.Name, 1, Array.Empty<string>()));
        }
        foreach (var es in externalSystems.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("ExternalSystem", es.Name, 1, Array.Empty<string>()));
        }
        var methodsBySystem = externalSystemMethods.GroupBy(m => m.ExternalSystemDefinitionId);
        var systemById = externalSystems.ToDictionary(x => x.Id);
        foreach (var grp in methodsBySystem.OrderBy(g => systemById.TryGetValue(g.Key, out var es) ? es.Name : string.Empty, StringComparer.Ordinal))
        {
            var systemName = systemById.TryGetValue(grp.Key, out var es) ? es.Name : grp.Key.ToString();
            foreach (var m in grp.OrderBy(x => x.Name, StringComparer.Ordinal))
            {
                entries.Add(new ManifestContentEntry(
                    "ExternalSystemMethod",
                    $"{systemName}.{m.Name}",
                    1,
                    new[] { $"ExternalSystem:{systemName}" }));
            }
        }
        foreach (var d in dbConnections.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("DatabaseConnection", d.Name, 1, Array.Empty<string>()));
        }
        foreach (var n in notificationLists.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("NotificationList", n.Name, 1, Array.Empty<string>()));
        }
        foreach (var s in smtpConfigs.OrderBy(x => x.Host, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("SmtpConfiguration", s.Host, 1, Array.Empty<string>()));
        }
        // SMS (S10b): mirror SMTP — one manifest row per config, keyed by AccountSid
        // (the natural key the importer matches on).
        foreach (var s in smsConfigs.OrderBy(x => x.AccountSid, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("SmsConfiguration", s.AccountSid, 1, Array.Empty<string>()));
        }
        // Inbound API keys are not transported (re-arch C4) — no ApiKey manifest entries.
        foreach (var m in apiMethods.OrderBy(x => x.Name, StringComparer.Ordinal))
        {
            entries.Add(new ManifestContentEntry("ApiMethod", m.Name, 1, Array.Empty<string>()));
        }

        // ---- M8: site/instance-scoped manifest rows ----
        // Sites are roots (no dependsOn). DataConnections depend on their site.
        // Instances depend on their template, their site, and each data connection
        // they bind. Inputs arrive pre-ordered, so iterate as-is for determinism.
        var connectionById = dataConnections.ToDictionary(c => c.Id);
        var connectionBySiteAndName = dataConnections
            .GroupBy(c => c.SiteId)
            .ToDictionary(g => g.Key, g => g.ToDictionary(c => c.Name, StringComparer.Ordinal));

        foreach (var site in sites)
        {
            entries.Add(new ManifestContentEntry("Site", site.SiteIdentifier, 1, Array.Empty<string>()));
        }
        foreach (var conn in dataConnections)
        {
            var siteIdentifier = SiteIdentifierOf(conn.SiteId, siteIdentifierById);
            entries.Add(new ManifestContentEntry(
                "DataConnection",
                $"{siteIdentifier}/{conn.Name}",
                1,
                new[] { $"Site:{siteIdentifier}" }));
        }
        foreach (var instance in instances)
        {
            var siteIdentifier = SiteIdentifierOf(instance.SiteId, siteIdentifierById);
            var templateName = templatesById.TryGetValue(instance.TemplateId, out var tpl)
                ? tpl.Name
                : instance.TemplateId.ToString();

            var deps = new List<string>
            {
                $"Template:{templateName}",
                $"Site:{siteIdentifier}",
            };

            // Connection-binding edges (resolved by id within the export closure).
            foreach (var binding in instance.ConnectionBindings)
            {
                if (connectionById.TryGetValue(binding.DataConnectionId, out var conn))
                {
                    deps.Add($"DataConnection:{SiteIdentifierOf(conn.SiteId, siteIdentifierById)}/{conn.Name}");
                }
            }
            // Native-alarm-source connection-name overrides (resolved by name within the site).
            if (connectionBySiteAndName.TryGetValue(instance.SiteId, out var byName))
            {
                foreach (var ovr in instance.NativeAlarmSourceOverrides)
                {
                    if (!string.IsNullOrEmpty(ovr.ConnectionNameOverride)
                        && byName.ContainsKey(ovr.ConnectionNameOverride))
                    {
                        deps.Add($"DataConnection:{siteIdentifier}/{ovr.ConnectionNameOverride}");
                    }
                }
            }

            var orderedDeps = deps.Distinct().OrderBy(x => x, StringComparer.Ordinal).ToList();
            entries.Add(new ManifestContentEntry("Instance", instance.UniqueName, 1, orderedDeps));
        }

        return entries;
    }
}