using System.Reflection;
using System.Text.Json;
using w4c_workflows.Models.Nodes;

namespace w4c_workflows.Services.Nodes;

/// <summary>
/// The catalog of known node types. It is the single source of truth for the
/// compiler/validator and the authoring UI (palette + generic parameter forms).
///
/// Blueprints come from two places:
///   - built-in core nodes, shipped as embedded JSON under <c>Catalog/</c>;
///   - additional packs (connectors, OpenAPI imports) loaded from files.
/// </summary>
public class NodeBlueprintCatalog
{
    private const string EmbeddedRoot = "w4c_workflows.Services.Nodes.Catalog.";

    private readonly IReadOnlyDictionary<string, List<NodeBlueprint>> _byType;

    public NodeBlueprintCatalog(IEnumerable<NodeBlueprint> blueprints)
    {
        var byType = new Dictionary<string, List<NodeBlueprint>>(StringComparer.Ordinal);

        foreach (var blueprint in blueprints)
        {
            if (string.IsNullOrWhiteSpace(blueprint.Type))
                throw new InvalidOperationException("a node blueprint is missing its type id");

            if (!byType.TryGetValue(blueprint.Type, out var versions))
                byType[blueprint.Type] = versions = new List<NodeBlueprint>();

            if (versions.Any(existing => SameVersion(existing.Version, blueprint.Version)))
                throw new InvalidOperationException(
                    $"duplicate node blueprint '{blueprint.Type}' version {blueprint.Version}");

            versions.Add(blueprint);
        }

        foreach (var versions in byType.Values)
            versions.Sort((a, b) => a.Version.CompareTo(b.Version));

        _byType = byType;
    }

    /// <summary>All registered blueprints, newest version first within each type.</summary>
    public IReadOnlyList<NodeBlueprint> All =>
        _byType.Values.SelectMany(v => v).ToList();

    /// <summary>Distinct category labels, sorted, for the palette's category rail.</summary>
    public IReadOnlyList<string> Categories =>
        _byType.Values.SelectMany(v => v)
            .SelectMany(b => b.Categories)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .OrderBy(c => c, StringComparer.OrdinalIgnoreCase)
            .ToList();

    public bool Contains(string type) => _byType.ContainsKey(type);

    /// <summary>The default (highest) version of a type, or null when unknown.</summary>
    public NodeBlueprint? Get(string type)
        => _byType.TryGetValue(type, out var versions) ? versions[^1] : null;

    /// <summary>
    /// Resolves a specific version. A requested version of 0/null means "default"
    /// (highest). Otherwise the closest version not newer than requested is used,
    /// so a task pinned to 2.5 keeps working after 2.6 ships.
    /// </summary>
    public NodeBlueprint? Resolve(string type, double? version = null)
    {
        if (!_byType.TryGetValue(type, out var versions))
            return null;

        if (version is null or 0)
            return versions[^1];

        NodeBlueprint? match = null;
        foreach (var candidate in versions)
        {
            if (candidate.Version <= version.Value + 0.0001)
                match = candidate;
            else
                break;
        }

        return match;
    }

    /// <summary>All versions of a type, newest first.</summary>
    public IReadOnlyList<NodeBlueprint> Versions(string type)
        => _byType.TryGetValue(type, out var versions)
            ? versions.OrderByDescending(v => v.Version).ToList()
            : Array.Empty<NodeBlueprint>();

    /// <summary>
    /// Filters the palette. <paramref name="query"/> matches type, display name,
    /// description or category; <paramref name="kind"/> matches <see cref="NodeKind"/>;
    /// <paramref name="category"/> matches a category label.
    /// </summary>
    public IReadOnlyList<NodeBlueprint> Search(string? query = null, string? kind = null, string? category = null)
    {
        IEnumerable<NodeBlueprint> results = _byType.Values.Select(v => v[^1]);

        if (!string.IsNullOrWhiteSpace(kind))
            results = results.Where(b => string.Equals(b.Kind, kind, StringComparison.OrdinalIgnoreCase));

        if (!string.IsNullOrWhiteSpace(category))
            results = results.Where(b => b.Categories.Any(c => string.Equals(c, category, StringComparison.OrdinalIgnoreCase)));

        if (!string.IsNullOrWhiteSpace(query))
        {
            var needle = query.Trim();
            results = results.Where(b =>
                Contains(b.Type, needle) ||
                Contains(b.DisplayName, needle) ||
                Contains(b.Description, needle) ||
                b.Categories.Any(c => Contains(c, needle)));
        }

        return results
            .OrderBy(b => b.DisplayName, StringComparer.OrdinalIgnoreCase)
            .ToList();
    }

    /// <summary>Loads core blueprints embedded in the running assembly.</summary>
    public static IReadOnlyList<NodeBlueprint> LoadEmbedded()
        => LoadEmbedded(typeof(NodeBlueprintCatalog).Assembly);

    /// <summary>Loads every <c>Catalog/*.json</c> embedded in <paramref name="assembly"/>.</summary>
    public static IReadOnlyList<NodeBlueprint> LoadEmbedded(Assembly assembly)
    {
        var blueprints = new List<NodeBlueprint>();

        foreach (var resource in assembly.GetManifestResourceNames())
        {
            if (!resource.StartsWith(EmbeddedRoot, StringComparison.Ordinal) ||
                !resource.EndsWith(".json", StringComparison.Ordinal))
            {
                continue;
            }

            using var stream = assembly.GetManifestResourceStream(resource);
            if (stream == null)
                continue;

            using var reader = new StreamReader(stream);
            var json = reader.ReadToEnd();
            var blueprint = JsonSerializer.Deserialize<NodeBlueprint>(json, NodeJson.Options)
                ?? throw new InvalidOperationException($"node blueprint '{resource}' is empty");
            blueprints.Add(blueprint);
        }

        return blueprints;
    }

    /// <summary>Loads all <c>*.json</c> blueprints from a directory (connector packs).</summary>
    public static IReadOnlyList<NodeBlueprint> LoadDirectory(string directory)
    {
        var blueprints = new List<NodeBlueprint>();
        if (!Directory.Exists(directory))
            return blueprints;

        foreach (var file in Directory.EnumerateFiles(directory, "*.json", SearchOption.AllDirectories))
        {
            var json = File.ReadAllText(file);
            var blueprint = JsonSerializer.Deserialize<NodeBlueprint>(json, NodeJson.Options)
                ?? throw new InvalidOperationException($"node blueprint '{file}' is empty");
            blueprints.Add(blueprint);
        }

        return blueprints;
    }

    private static bool SameVersion(double a, double b) => Math.Abs(a - b) < 0.0001;

    private static bool Contains(string? haystack, string needle)
        => haystack?.Contains(needle, StringComparison.OrdinalIgnoreCase) == true;
}