using System.Text.Json.Nodes;
using w4c_workflows.Models.Nodes;
using w4c_workflows.Services.Nodes;
using w4c_workflows.Services.Nodes.Executors;
using Xunit;

namespace w4c_workflows.Tests;

/// <summary>
/// Unit tests for the <c>core.executeWorkflow</c> node: parameter validation,
/// fan-out modes, child-failure mapping and the no-wait behaviour. The actual
/// child execution is exercised end-to-end in <c>SubWorkflowInvokerTests</c>.
/// </summary>
public class ExecuteWorkflowNodeExecutorTests
{
    private static readonly NodeBlueprintCatalog Catalog = NodeTestData.CoreCatalog();

    private static FlowItem Item(string json) => FlowItem.FromJson(JsonNode.Parse(json)!.AsObject());

    private sealed class FakeInvoker : ISubWorkflowInvoker
    {
        public string? ChildJson { get; init; }
        public NodeFailure? Failure { get; init; }
        public List<SubWorkflowInvocation> Calls { get; } = new();

        public int MaxDepth => 10;

        public Task<SubWorkflowRunResult> InvokeAsync(SubWorkflowInvocation invocation, CancellationToken ct)
        {
            Calls.Add(invocation);
            if (Failure != null)
                return Task.FromResult(new SubWorkflowRunResult { Items = Array.Empty<FlowItem>(), Failure = Failure });

            var items = ChildJson == null
                ? Array.Empty<FlowItem>()
                : new FlowItem[] { Item(ChildJson) };
            return Task.FromResult(SubWorkflowRunResult.Ok(items, Guid.NewGuid()));
        }
    }

    private static NodeExecutionContext Context(
        JsonObject parameters, ISubWorkflowInvoker? invoker, params IReadOnlyList<FlowItem>[] inputs)
        => new()
        {
            Blueprint = Catalog.Get("core.executeWorkflow")!,
            Parameters = parameters,
            Inputs = inputs,
            SubWorkflows = invoker,
            TaskId = "call",
        };

    [Fact]
    public async Task Fails_when_no_sub_workflow_invoker_is_installed()
    {
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child" }, null, Array.Empty<FlowItem>()), default);

        Assert.False(outcome.Succeeded);
        Assert.Equal("subworkflow_unavailable", outcome.Failure!.Code);
    }

    [Fact]
    public async Task Requires_a_workflow_parameter()
    {
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject(), new FakeInvoker(), Array.Empty<FlowItem>()), default);

        Assert.False(outcome.Succeeded);
        Assert.Equal("invalid_parameter", outcome.Failure!.Code);
    }

    [Fact]
    public async Task Runs_once_with_all_items_and_maps_the_child_output()
    {
        var invoker = new FakeInvoker { ChildJson = """{"child":true}""" };
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child-transform" }, invoker,
                new[] { Item("""{"n":1}"""), Item("""{"n":2}""") }), default);

        Assert.True(outcome.Succeeded);
        var invocation = Assert.Single(invoker.Calls);
        Assert.Equal(SubWorkflowMode.AllItems, invocation.Mode);
        Assert.Equal(2, invocation.Input.Count);
        Assert.True(invocation.RecordHistory);
        var item = Assert.Single(outcome.Outputs[0]);
        Assert.True(item.Json["child"]!.GetValue<bool>());
    }

    [Fact]
    public async Task Forwards_each_item_mode_to_the_invoker()
    {
        // Fan-out itself is the invoker's job (covered end-to-end); the executor
        // only validates and forwards the mode.
        var invoker = new FakeInvoker { ChildJson = """{"child":true}""" };
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child", ["mode"] = "eachItem" }, invoker,
                new[] { Item("""{"n":1}"""), Item("""{"n":2}""") }), default);

        Assert.True(outcome.Succeeded);
        var invocation = Assert.Single(invoker.Calls);
        Assert.Equal(SubWorkflowMode.EachItem, invocation.Mode);
        Assert.Equal(2, invocation.Input.Count);
    }

    [Fact]
    public async Task Maps_a_child_failure_to_a_node_failure()
    {
        var invoker = new FakeInvoker { Failure = new NodeFailure("child boom", "child_code") };
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child" }, invoker, new[] { Item("{}") }), default);

        Assert.False(outcome.Succeeded);
        Assert.Equal("child boom", outcome.Failure!.Message);
        Assert.Equal("child_code", outcome.Failure.Code);
    }

    [Fact]
    public async Task Does_not_emit_child_items_when_not_waiting()
    {
        var invoker = new FakeInvoker { ChildJson = """{"child":true}""" };
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child", ["waitForCompletion"] = false },
                invoker, new[] { Item("""{"n":1}""") }), default);

        Assert.True(outcome.Succeeded);
        Assert.Single(invoker.Calls);          // the child still ran
        Assert.Empty(outcome.Outputs);         // but its items are not forwarded
    }

    [Fact]
    public async Task Rejects_an_invalid_mode()
    {
        var outcome = await new ExecuteWorkflowNodeExecutor().RunAsync(
            Context(new JsonObject { ["workflow"] = "child", ["mode"] = "sideways" },
                new FakeInvoker(), new[] { Item("{}") }), default);

        Assert.False(outcome.Succeeded);
        Assert.Equal("invalid_parameter", outcome.Failure!.Code);
    }
}