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

namespace w4c_workflows.Tests;

/// <summary>
/// Covers the node-mode half of <see cref="WorkflowCompiler"/>: steps become
/// tasks with node columns and their next/explicit connections become persisted
/// edge rows. The legacy (script) path is covered by WorkflowCompilerTests.
/// </summary>
public class NodeWorkflowCompilerTests
{
    private const string Tenant = "t1";
    private const string Path = "workflows/branch.yaml";

    private const string BranchYaml = """
        name: branch-demo
        tasks:
          - id: prepare
            node: { type: core.set }
            parameters:
              mode: manual
              fields:
                - name: status
                  value: ready
            next: decide
          - id: decide
            node: { type: core.if }
            parameters:
              left: "={{ $json.status }}"
              operator: equals
              right: ready
            edges:
              - { output: 0, to: ok }
              - { output: 1, to: nope }
          - id: ok
            node: { type: core.noop }
          - id: nope
            node: { type: core.noop }
        """;

    private static WorkflowCompiler NewCompiler()
        => new(new WorkflowValidator(new LanguageRegistry()));

    private static Guid TaskId(string id) => DeterministicGuid.For($"task::{Tenant}::workflows::{Path}::{id}");

    [Fact]
    public void Compiles_node_tasks_with_node_columns_and_parameters_json()
    {
        var result = NewCompiler().Compile(BranchYaml, Path, Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        var compiled = result.Workflow!;

        Assert.Equal(WorkflowMode.Function, compiled.Workflow.Mode);
        Assert.Equal(4, compiled.Tasks.Count);
        Assert.Empty(compiled.Tasks.Where(t => t.NodeType == null));

        var prepare = compiled.Tasks.Single(t => t.Key == "prepare");
        Assert.Equal("core.set", prepare.NodeType);
        Assert.Equal(1, prepare.NodeVersion);
        Assert.Equal("node", prepare.Language);
        Assert.Null(prepare.NextId); // node mode never uses the linear chain

        var parameters = JsonNode.Parse(prepare.ParametersJson!)!.AsObject();
        Assert.Equal("manual", parameters["mode"]!.GetValue<string>());
    }

    [Fact]
    public void Lowers_next_and_explicit_outputs_into_edges()
    {
        var result = NewCompiler().Compile(BranchYaml, Path, Tenant);
        Assert.True(result.Success, string.Join("\n", result.Errors));

        var edges = result.Workflow!.Edges;
        Assert.Contains(edges, e => e.FromTaskId == TaskId("prepare") && e.FromOutput == 0 && e.ToTaskId == TaskId("decide"));
        Assert.Contains(edges, e => e.FromTaskId == TaskId("decide") && e.FromOutput == 0 && e.ToTaskId == TaskId("ok"));
        Assert.Contains(edges, e => e.FromTaskId == TaskId("decide") && e.FromOutput == 1 && e.ToTaskId == TaskId("nope"));
    }

    [Fact]
    public void Compile_is_idempotent_for_node_workflows()
    {
        var compiler = NewCompiler();
        var first = compiler.Compile(BranchYaml, Path, Tenant);
        var second = compiler.Compile(BranchYaml, Path, Tenant);

        Assert.Equal(
            first.Workflow!.Edges.Select(e => e.Id).OrderBy(x => x),
            second.Workflow!.Edges.Select(e => e.Id).OrderBy(x => x));
        Assert.Equal(
            first.Workflow!.Tasks.Select(t => t.Id).OrderBy(x => x),
            second.Workflow!.Tasks.Select(t => t.Id).OrderBy(x => x));
    }

    [Fact]
    public void Rejects_an_unknown_node_type()
    {
        var yaml = """
            name: unknown
            tasks:
              - id: a
                node: { type: does.not.exist }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);

        Assert.False(result.Success);
        Assert.Contains(result.Errors, e => e.Contains("unknown node type 'does.not.exist'"));
    }

    [Fact]
    public void Rejects_a_node_workflow_step_without_a_node()
    {
        var yaml = """
            name: mixed
            tasks:
              - id: a
                node: { type: core.noop }
              - id: b
                entry: { file: b.sh }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);

        Assert.False(result.Success);
        Assert.Contains(result.Errors, e => e.Contains("must declare 'node'"));
    }

    [Fact]
    public void Legacy_workflow_compiles_without_edges_and_keeps_the_next_chain()
    {
        var yaml = """
            name: legacy
            mode: function
            language: shell
            entry: { file: root.sh }
            tasks:
              - id: a
                parent: root
                next: b
                entry: { file: a.sh }
              - id: b
                parent: root
                entry: { file: b.sh }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        Assert.Empty(result.Workflow!.Edges);
        Assert.All(result.Workflow.Tasks, t => Assert.Null(t.NodeType));

        var a = result.Workflow.Tasks.Single(t => t.Key == "a");
        var b = result.Workflow.Tasks.Single(t => t.Key == "b");
        Assert.Equal(b.Id, a.NextId);
    }
}