using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Text.Json;
using NucleicProtocol.Interop;

namespace NucleicApp.Services;

/// Read-only projection of host authority (WINDOWS_PORT §7). Every mutation enters through a
/// HostMsg; user actions leave as ClientMsg intents through ``HostConnection``.
public sealed class RendererStore : INotifyPropertyChanged, IDisposable
{
    private readonly Dictionary<string, SessionSummary> sessions = new(StringComparer.Ordinal);
    private readonly Dictionary<string, ApprovalRequest> approvals = new(StringComparer.Ordinal);
    private readonly ITranscriptProjector? projector;

    private IReadOnlyList<SessionSummary> sessionSnapshot = [];
    private IReadOnlyList<ApprovalRequest> approvalSnapshot = [];
    private JsonElement? dashboard;
    private JsonElement? settings;
    private JsonElement? peers;
    private JsonElement? intelligenceCatalog;
    private string? lastError;

    public RendererStore(ITranscriptProjector? projector = null) => this.projector = projector;

    public IReadOnlyList<SessionSummary> Sessions => sessionSnapshot;
    public IReadOnlyList<ApprovalRequest> PendingApprovals => approvalSnapshot;
    public JsonElement? Dashboard => dashboard;
    public JsonElement? Settings => settings;
    public JsonElement? Peers => peers;
    public JsonElement? IntelligenceCatalog => intelligenceCatalog;
    public string? LastError => lastError;

    public event PropertyChangedEventHandler? PropertyChanged;
    public event Action<ProjectionDiff>? ProjectionChanged;
    public event Action<ProtocolMessage>? MessageApplied;

    public void Apply(string hostMessageJson) => Apply(ProtocolMessage.Parse(hostMessageJson));

    public void Apply(ProtocolMessage message)
    {
        var root = message.Root;
        switch (message.Tag)
        {
            case "sessionList":
                sessions.Clear();
                if (root.TryGetProperty("input", out var list))
                    foreach (var item in list.EnumerateArray()) UpsertSession(item);
                PublishSessions();
                break;
            case "sessionUpdated":
                UpsertSession(root);
                PublishSessions();
                break;
            case "snapshot":
                if (root.TryGetProperty("summary", out var summary))
                {
                    UpsertSession(summary);
                    PublishSessions();
                }
                if (root.TryGetProperty("pendingApprovals", out var pending))
                {
                    foreach (var item in pending.EnumerateArray()) UpsertApproval(item);
                    PublishApprovals();
                }
                break;
            case "approvalRequested":
                UpsertApproval(root);
                PublishApprovals();
                break;
            case "approvalResolved":
                if (String(root, "id") is { } resolved) approvals.Remove(resolved);
                PublishApprovals();
                break;
            case "dashboard":
                dashboard = root.Clone();
                Changed(nameof(Dashboard));
                break;
            case "settings":
                settings = root.GetProperty("settings").Clone();
                Changed(nameof(Settings));
                break;
            case "peerList":
                peers = root.GetProperty("input").Clone();
                Changed(nameof(Peers));
                break;
            case "intelligenceCatalog":
                intelligenceCatalog = root.GetProperty("intelligenceCatalog").Clone();
                Changed(nameof(IntelligenceCatalog));
                break;
            case "error":
                lastError = String(root, "message") ?? "The host reported an error.";
                Changed(nameof(LastError));
                break;
        }

        if (projector is not null)
        {
            var diff = projector.Apply(message.Json);
            if (diff.Root.GetProperty("splices").GetArrayLength() > 0)
                ProjectionChanged?.Invoke(diff);
        }
        MessageApplied?.Invoke(message);
    }

    private void UpsertSession(JsonElement json)
    {
        var id = String(json, "sessionID") ?? throw new JsonException("session summary has no sessionID");
        sessions[id] = new SessionSummary(
            id, String(json, "title") ?? "Untitled", String(json, "projectID"),
            String(json, "projectName"), String(json, "status") ?? "unknown",
            Int(json, "pendingApprovalCount"), json.Clone());
    }

    private void UpsertApproval(JsonElement json)
    {
        var id = String(json, "id") ?? throw new JsonException("approval has no id");
        approvals[id] = new ApprovalRequest(
            id, String(json, "sessionID") ?? string.Empty, String(json, "title") ?? "Approval",
            String(json, "toolName") ?? string.Empty, String(json, "risk") ?? string.Empty,
            json.Clone());
    }

    private void PublishSessions()
    {
        sessionSnapshot = sessions.Values
            .OrderByDescending(item => item.Raw.TryGetProperty("updatedAt", out var value)
                ? value.GetDouble() : 0)
            .ToArray();
        Changed(nameof(Sessions));
    }

    private void PublishApprovals()
    {
        approvalSnapshot = approvals.Values.ToArray();
        Changed(nameof(PendingApprovals));
    }

    private static string? String(JsonElement root, string name) =>
        root.TryGetProperty(name, out var value) && value.ValueKind == JsonValueKind.String
            ? value.GetString() : null;
    private static int Int(JsonElement root, string name) =>
        root.TryGetProperty(name, out var value) && value.TryGetInt32(out var number) ? number : 0;
    private void Changed([CallerMemberName] string? name = null) =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));

    public void Dispose() => projector?.Dispose();
}

public sealed record SessionSummary(
    string Id, string Title, string? ProjectId, string? ProjectName,
    string Status, int PendingApprovalCount, JsonElement Raw);

public sealed record ApprovalRequest(
    string Id, string SessionId, string Title, string ToolName, string Risk, JsonElement Raw);