using w4c_workflows.Models;
using w4c_workflows.Services;
using w4c_workflows.Services.Nodes;
using Xunit;

namespace w4c_workflows.Tests;

public class WorkflowCompilerTests
{
    private const string Tenant = "t1";
    private const string Path = "workflows/main-task.yaml";

    private static readonly string ExampleYaml = """
        name: main-task
        description: Root handler consuming order events
        mode: handler
        language: typescript
        target: default
        trigger:
          type: queue
          stream: orders
        entry: { file: index.ts, function: handler }
        env: { FOO: "bar" }
        tasks:
          - id: validate
            parent: root
            next: enrich
            onError: compensate
            language: python
            entry: { file: validate.py }
          - id: enrich
            parent: root
            next: persist
            language: csharp
            entry: { file: Enrich.cs }
          - id: persist
            parent: root
            language: shell
            entry: { file: persist.sh }
          - id: compensate
            parent: root
            language: python
            entry: { file: compensate.py }
        """;

    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_plan_example_with_correct_flow()
    {
        var result = NewCompiler().Compile(ExampleYaml, Path, Tenant);

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

        Assert.Equal("main-task", wf.Name);
        Assert.Equal(WorkflowMode.Handler, wf.Mode);
        Assert.Equal("compiled", wf.Status);

        // 1 root + 4 declared tasks.
        Assert.Equal(5, tasks.Count);

        var root = tasks.Single(t => t.Order == 0);
        var validate = tasks.Single(t => t.Id == TaskId("validate"));
        var enrich = tasks.Single(t => t.Id == TaskId("enrich"));
        var persist = tasks.Single(t => t.Id == TaskId("persist"));
        var compensate = tasks.Single(t => t.Id == TaskId("compensate"));

        Assert.Null(root.ParentId);
        Assert.Equal(validate.Id, root.NextId);

        Assert.Equal(root.Id, validate.ParentId);
        Assert.Equal(enrich.Id, validate.NextId);
        Assert.Equal(compensate.Id, validate.OnErrorId);

        Assert.Equal(enrich.NextId, persist.Id);
        Assert.Null(persist.NextId); // terminal

        // Compensation task is organizational (parent: root), not on the chain.
        Assert.Equal(root.Id, compensate.ParentId);
        Assert.Null(compensate.NextId);
    }

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

        Assert.Equal(first.Workflow!.Workflow.Id, second.Workflow!.Workflow.Id);
        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 Compiles_root_only_workflow()
    {
        var yaml = """
            name: ping
            mode: function
            language: shell
            entry: { file: ping.sh }
            """;

        var result = NewCompiler().Compile(yaml, "workflows/ping.yaml", Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        Assert.Single(result.Workflow!.Tasks);
        Assert.Null(result.Workflow!.Tasks[0].NextId);
    }

    [Theory]
    [InlineData("", "name is required")]
    [InlineData("mode: function\nlanguage: shell\nentry: { file: a.sh }", "name is required")]
    [InlineData("name: x\nlanguage: shell\nentry: { file: a.sh }", "mode is required")]
    [InlineData("name: x\nmode: function\nentry: { file: a.sh }", "language is required")]
    [InlineData("name: x\nmode: function\nlanguage: cobol\nentry: { file: a.sh }", "language 'cobol' is not supported")]
    public void Rejects_invalid_header(string yaml, string expectedError)
    {
        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.False(result.Success);
        Assert.Contains(result.Errors, e => e.Contains(expectedError, StringComparison.Ordinal));
    }

    [Fact]
    public void Rejects_unknown_next_reference()
    {
        var yaml = """
            name: x
            mode: function
            language: shell
            entry: { file: a.sh }
            tasks:
              - id: a
                next: ghost
                entry: { file: a.sh }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.Contains(result.Errors, e => e.Contains("next 'ghost' does not reference", StringComparison.Ordinal));
    }

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

        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.Contains(result.Errors, e => e.Contains("'a' is duplicated", StringComparison.Ordinal));
    }

    [Fact]
    public void Rejects_cycle_in_success_chain()
    {
        // root -> a -> b -> c -> b  (b↔c cycle; b also has 2 incoming edges)
        var yaml = """
            name: x
            mode: function
            language: shell
            entry: { file: a.sh }
            tasks:
              - id: a
                next: b
                entry: { file: a.sh }
              - id: b
                next: c
                entry: { file: b.sh }
              - id: c
                next: b
                entry: { file: c.sh }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.False(result.Success);
        Assert.Contains(result.Errors, e =>
            e.Contains("cycle", StringComparison.OrdinalIgnoreCase) ||
            e.Contains("linear", StringComparison.OrdinalIgnoreCase));
    }

    [Fact]
    public void Rejects_handler_mode_with_non_queue_trigger()
    {
        var yaml = """
            name: x
            mode: handler
            language: shell
            entry: { file: a.sh }
            trigger:
              type: cron
              cron: "0 * * * *"
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.Contains(result.Errors, e => e.Contains("handler mode requires trigger.type = 'queue'", StringComparison.Ordinal));
    }

    [Fact]
    public void Rejects_unreachable_task()
    {
        // a -> b, but d is disconnected (not on the chain, not a compensation target).
        var yaml = """
            name: x
            mode: function
            language: shell
            entry: { file: a.sh }
            tasks:
              - id: a
                next: b
                entry: { file: a.sh }
              - id: b
                entry: { file: b.sh }
              - id: d
                parent: root
                entry: { file: d.sh }
            """;

        var result = NewCompiler().Compile(yaml, Path, Tenant);
        Assert.Contains(result.Errors, e => e.Contains("unreachable", StringComparison.OrdinalIgnoreCase));
    }

    [Fact]
    public void Resolves_server_reference_from_header_default_and_task_override()
    {
        // S8: a workflow-level `server` becomes the default for every task; an explicit
        // task-level `server` overrides it. Absent everywhere => null (local subprocess).
        var yaml = """
            name: srv-flow
            mode: function
            language: shell
            server: srv-default
            entry: { file: a.sh }
            tasks:
              - id: a
                next: b
                entry: { file: a.sh }
              - id: b
                server: srv-optimized
                next: c
                entry: { file: b.sh }
              - id: c
                entry: { file: c.sh }
            """;

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

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

        // Root + 3 declared tasks.
        var root = tasks.Single(t => t.Order == 0);
        var a = tasks.Single(t => t.Key == "a");
        var b = tasks.Single(t => t.Key == "b");
        var c = tasks.Single(t => t.Key == "c");

        Assert.Equal("srv-default", root.Server);   // header default applies to root
        Assert.Equal("srv-default", a.Server);      // header default when no override
        Assert.Equal("srv-optimized", b.Server);    // task-level override wins
        Assert.Equal("srv-default", c.Server);      // header default for a chain task

        // No server anywhere => null keeps the local subprocess default.
        var bare = NewCompiler().Compile(ExampleYaml, Path, Tenant);
        Assert.All(bare.Workflow!.Tasks, t => Assert.Null(t.Server));
    }

    [Fact]
    public void DurationParser_parses_common_forms()
    {
        Assert.True(DurationParser.TryParse("45s", out var s));
        Assert.Equal(TimeSpan.FromSeconds(45), s);
        Assert.True(DurationParser.TryParse("30m", out var m));
        Assert.Equal(TimeSpan.FromMinutes(30), m);
        Assert.True(DurationParser.TryParse("2h", out var h));
        Assert.Equal(TimeSpan.FromHours(2), h);
        Assert.True(DurationParser.TryParse("1h30m", out var compound));
        Assert.Equal(TimeSpan.FromMinutes(90), compound);
        Assert.False(DurationParser.TryParse("soon", out _));
    }

    // ------------------------------------------------------- S1 convergence

    private const string FunctionScriptYaml = """
        name: legacy-fn
        mode: function
        language: shell
        entry: { file: root.sh }
        tasks:
          - id: a
            next: b
            language: shell
            entry: { file: a.sh }
          - id: b
            entry: { file: b.sh }
        """;

    private static WorkflowCompiler NewLoweringCompiler()
        => new(new WorkflowValidator(new LanguageRegistry()), lowerLegacyScripts: true);

    [Fact]
    public void Lowers_function_script_to_node_mode_when_enabled()
    {
        var result = NewLoweringCompiler().Compile(FunctionScriptYaml, "workflows/legacy-fn.yaml", Tenant);

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

        // Every step becomes a node step; the synthetic entry plus both tasks exist.
        Assert.All(tasks, t => Assert.Equal("node", t.Language));
        Assert.All(tasks, t => Assert.False(string.IsNullOrWhiteSpace(t.NodeType)));
        Assert.Contains(tasks, t => t.Key == LegacyWorkflowLowerer.EntryStepId);
        Assert.Contains(tasks, t => t.Key == "a");
        Assert.Contains(tasks, t => t.Key == "b");

        // The `next` chain is lowered into port edges instead of NextId.
        Assert.All(tasks, t => Assert.Null(t.NextId));
        Assert.NotEmpty(result.Workflow.Edges);
    }

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

        var result = NewLoweringCompiler().Compile(yaml, "workflows/durable-legacy.yaml", Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        // Durable/handler keep the linear engine: the node kernel does not
        // checkpoint/resume yet, so lowering them would lose semantics.
        Assert.All(result.Workflow!.Tasks, t => Assert.Null(t.NodeType));
        Assert.Empty(result.Workflow.Edges);
    }

    [Fact]
    public void Lowering_is_off_by_default()
    {
        var result = NewCompiler().Compile(FunctionScriptYaml, "workflows/legacy-fn.yaml", Tenant);

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

    [Fact]
    public void Webhook_trigger_populates_the_indexed_webhook_path()
    {
        var yaml = """
            name: hook
            mode: function
            language: shell
            entry: { file: root.sh }
            trigger:
              type: webhook
              webhookPath: /h/orders
            """;

        var result = NewCompiler().Compile(yaml, "workflows/hook.yaml", Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        Assert.Equal("/h/orders", result.Workflow!.Workflow.WebhookPath);
    }

    [Fact]
    public void Node_workflow_webhook_trigger_also_populates_the_column()
    {
        var yaml = """
            name: hook-node
            trigger:
              type: webhook
              webhookPath: /h/node-orders
            tasks:
              - id: only
                node: { type: core.noop }
            """;

        var result = NewCompiler().Compile(yaml, "workflows/hook-node.yaml", Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        Assert.Equal("/h/node-orders", result.Workflow!.Workflow.WebhookPath);
    }

    [Fact]
    public void Non_webhook_trigger_leaves_the_webhook_path_null()
    {
        var yaml = """
            name: cron-only
            mode: function
            language: shell
            entry: { file: root.sh }
            trigger:
              type: cron
              cron: "0 * * * *"
            """;

        var result = NewCompiler().Compile(yaml, "workflows/cron-only.yaml", Tenant);

        Assert.True(result.Success, string.Join("\n", result.Errors));
        Assert.Null(result.Workflow!.Workflow.WebhookPath);
    }
}