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

namespace w4c_workflows.Services.Nodes.Executors;

/// <summary>
/// Edit-fields node. Two modes:
///   - <c>manual</c>: set the listed <c>fields</c> (an array of <c>{ name, value }</c>)
///     on each item, optionally discarding the fields that were not listed;
///   - <c>json</c>: replace the item payload with the resolved <c>jsonOutput</c>.
/// Binary attachments pass through unless <c>includeBinary</c> is false.
/// </summary>
public sealed class SetNodeExecutor : INodeExecutor
{
    public string Type => "core.set";

    public Task<NodeExecutionOutcome> RunAsync(NodeExecutionContext context, CancellationToken ct)
    {
        var mode = ReadString(context, "mode") ?? "manual";
        var keepOnlySet = ReadBool(context, "keepOnlySet");
        var includeBinary = ReadBool(context, "includeBinary", defaultValue: true);
        var items = context.Input(0);

        var output = new List<FlowItem>(items.Count);
        foreach (var item in items)
        {
            var json = string.Equals(mode, "json", StringComparison.OrdinalIgnoreCase)
                ? BuildFromJson(context)
                : ApplyFields(context, item.Json, keepOnlySet);

            output.Add(new FlowItem
            {
                Json = json,
                Binary = includeBinary ? item.Binary : null,
                Origin = item.Origin,
            });
        }

        return Task.FromResult(NodeExecutionOutcome.Single(output));
    }

    private static JsonObject ApplyFields(NodeExecutionContext context, JsonObject source, bool keepOnlySet)
    {
        var result = keepOnlySet ? new JsonObject() : (JsonObject)source.DeepClone();

        if (context.Parameters["fields"] is not JsonArray fields)
            return result;

        foreach (var entry in fields)
        {
            if (entry is not JsonObject field)
                continue;
            var name = field["name"]?.GetValue<string>();
            if (string.IsNullOrWhiteSpace(name))
                continue;
            result[name] = field["value"]?.DeepClone();
        }

        return result;
    }

    private static JsonObject BuildFromJson(NodeExecutionContext context)
    {
        var value = context.Parameters["jsonOutput"];
        if (value is JsonObject obj)
            return (JsonObject)obj.DeepClone();

        return value is null
            ? new JsonObject()
            : new JsonObject { ["value"] = value.DeepClone() };
    }

    private static string? ReadString(NodeExecutionContext context, string name)
        => context.Parameters[name] is JsonValue value && value.TryGetValue<string>(out var text) ? text : null;

    private static bool ReadBool(NodeExecutionContext context, string name, bool defaultValue = false)
        => context.Parameters[name] is JsonValue value && value.TryGetValue<bool>(out var flag) ? flag : defaultValue;
}