using System.Text.Json.Nodes;
using w4c_workflows.Models.Credentials;
using w4c_workflows.Models.Nodes;
using w4c_workflows.Services.Nodes.Interpolation;
using w4c_workflows.Services.Security;

namespace w4c_workflows.Services.Nodes;

// Invocation half of the graph runner: resolving a node's parameters per item,
// building its execution context and running the executor (one call per item, or
// the whole array at once for all-items nodes).

public sealed partial class NodeGraphRunner
{
    private async Task<NodeExecutionOutcome> InvokeAsync(
        NodeGraphNode node,
        IReadOnlyList<IReadOnlyList<FlowItem>> inputs,
        NodeRunEnvironment environment,
        IReadOnlyDictionary<string, List<IReadOnlyList<FlowItem>>> outputs,
        NodeGraph graph,
        int runIndex,
        CancellationToken ct)
    {
        var executor = _executors.Resolve(node.Blueprint.Type)
            ?? throw new InvalidOperationException($"no executor for '{node.Blueprint.Type}'");

        var loopBackInput = graph.EdgesTo(node.Id).Any(e => e.IsLoopBack);

        // Nodes with several inputs, or an explicit all-items run mode, receive the
        // whole array at once; the default is one invocation per input item.
        var allItems = node.EffectiveRunMode == NodeRunMode.AllItems || node.Blueprint.Inputs.Count > 1;
        if (allItems)
        {
            var parameters = ResolveParameters(node, null, 0, environment, outputs, graph, runIndex);
            return await executor.RunAsync(
                BuildContext(node, parameters, inputs, environment, 0, runIndex, loopBackInput), ct);
        }

        var mainItems = inputs.Count > 0 ? inputs[0] : Array.Empty<FlowItem>();

        // A node with no incoming items is skipped, except the entry node: like a
        // trigger/source it runs once with an empty item so it can generate data.
        var isEntry = string.Equals(node.Id, graph.EntryNodeId, StringComparison.Ordinal);
        if (mainItems.Count == 0 && !isEntry)
            return NodeExecutionOutcome.Empty;
        if (mainItems.Count == 0)
            mainItems = new[] { new FlowItem { Json = new JsonObject() } };

        var accumulated = new List<List<FlowItem>>();

        for (var index = 0; index < mainItems.Count; index++)
        {
            var parameters = ResolveParameters(node, mainItems[index], index, environment, outputs, graph, runIndex);
            var outcome = await executor.RunAsync(
                BuildContext(node, parameters, new[] { (IReadOnlyList<FlowItem>)new[] { mainItems[index] } }, environment, index, runIndex, loopBackInput),
                ct);

            if (!outcome.Succeeded)
                return outcome;

            while (accumulated.Count < outcome.Outputs.Count)
                accumulated.Add(new List<FlowItem>());

            for (var port = 0; port < outcome.Outputs.Count; port++)
                accumulated[port].AddRange(outcome.Outputs[port]);
        }

        return new NodeExecutionOutcome
        {
            Outputs = accumulated.Select(list => (IReadOnlyList<FlowItem>)list).ToList(),
        };
    }

    private NodeExecutionContext BuildContext(
        NodeGraphNode node,
        JsonObject parameters,
        IReadOnlyList<IReadOnlyList<FlowItem>> inputs,
        NodeRunEnvironment environment,
        int itemIndex,
        int runIndex,
        bool loopBackInput = false)
        => new()
        {
            Blueprint = node.Blueprint,
            Parameters = parameters,
            Inputs = inputs,
            Credentials = environment.Credentials,
            Environment = environment.Variables,
            TenantId = environment.TenantId,
            RunId = environment.RunId,
            TaskId = node.Id,
            NodeName = node.Id,
            ItemIndex = itemIndex,
            RunIndex = runIndex,
            WorkingDirectory = environment.WorkingDirectory,
            LoopBackInput = loopBackInput,
            State = environment.State,
            SubWorkflows = environment.SubWorkflows,
            Depth = environment.Depth,
            Services = environment.Services,
        };

    private JsonObject ResolveParameters(
        NodeGraphNode node,
        FlowItem? item,
        int itemIndex,
        NodeRunEnvironment environment,
        IReadOnlyDictionary<string, List<IReadOnlyList<FlowItem>>> outputs,
        NodeGraph graph,
        int runIndex)
    {
        var scope = new InterpolationScope
        {
            Item = item?.Json,
            Parameters = node.Parameters,
            Environment = environment.Variables,
            ItemIndex = itemIndex,
            RunIndex = runIndex,
            NodeItems = name => ResolveNodeItems(name, outputs, graph),
        };

        return _interpolator.ResolveObject(node.Parameters, scope);
    }

    private static IReadOnlyList<FlowItem> ResolveNodeItems(
        string name,
        IReadOnlyDictionary<string, List<IReadOnlyList<FlowItem>>> outputs,
        NodeGraph graph)
    {
        if (outputs.TryGetValue(name, out var direct) && direct.Count > 0)
            return direct[0];

        // Fall back to the blueprint display name, so $("Send message") also works.
        var byName = graph.FindByDisplayName(name);
        if (byName != null && outputs.TryGetValue(byName.Id, out var named) && named.Count > 0)
            return named[0];

        return Array.Empty<FlowItem>();
    }
}