using ClawdDotNet.Core.Audit;
using ClawdDotNet.Core.Files;
using ClawdDotNet.Core.Storage;
using ClawdDotNet.Core.Tests.Infrastructure;
using Shouldly;

namespace ClawdDotNet.Core.Tests.Files;

/// <summary>
/// #720: The lost update — A reads, B reads, A writes, B writes, and A's change is gone
/// without a word. The ledger refuses B's write instead and keeps the conflict for the count.
/// </summary>
public sealed class FileLedgerTests : IDisposable
{
    private readonly string _dir = Path.Combine(Path.GetTempPath(), "clawd-tests", "ledger-" + Guid.NewGuid().ToString("N")[..8]);
    private readonly string _file;
    private readonly FileLedger _ledger;

    public FileLedgerTests()
    {
        Directory.CreateDirectory(_dir);
        _file = Path.Combine(_dir, "plan.md");
        File.WriteAllText(_file, "v1");
        _ledger = new FileLedger(new SqliteStorage(Path.Combine(_dir, "state.db")));
    }

    public void Dispose()
    {
        SqliteStorage.ReleasePooledConnections(_dir);
        try { Directory.Delete(_dir, recursive: true); }
        catch { /* cleanup is secondary */ }
    }

    private string? Now => FileLedger.HashOf(_file);

    private void Write(string agent, string content)
    {
        File.WriteAllText(_file, content);
        _ledger.NoteReplace(agent, "run-" + agent, _file, Now);
    }

    [Fact]
    public void The_second_writer_of_the_same_read_is_refused()
    {
        _ledger.NoteRead("a", _file, Now);
        _ledger.NoteRead("b", _file, Now);

        _ledger.CheckReplace("a", "run-a", _file, "shared", Now).ShouldBeNull();
        Write("a", "v2 by a");

        var conflict = _ledger.CheckReplace("b", "run-b", _file, "shared", Now);
        conflict.ShouldNotBeNull();
        conflict.Kind.ShouldBe(FileConflict.ChangedSinceRead);
        conflict.OtherAgentId.ShouldBe("a");
        conflict.OtherRunId.ShouldBe("run-a");
    }

    [Fact]
    public void After_reading_again_the_write_goes_through()
    {
        _ledger.NoteRead("b", _file, Now);
        Write("a", "v2 by a");
        _ledger.CheckReplace("b", null, _file, "shared", Now).ShouldNotBeNull();

        _ledger.NoteRead("b", _file, Now);

        _ledger.CheckReplace("b", null, _file, "shared", Now).ShouldBeNull();
    }

    [Fact]
    public void Writing_twice_in_a_row_is_not_a_conflict_with_oneself()
    {
        _ledger.NoteRead("a", _file, Now);
        Write("a", "v2");

        _ledger.CheckReplace("a", null, _file, "shared", Now).ShouldBeNull();
    }

    [Fact]
    public void Another_agents_file_is_not_overwritten_unread()
    {
        Write("a", "a's work");

        var conflict = _ledger.CheckReplace("b", null, _file, "shared", Now);

        conflict.ShouldNotBeNull();
        conflict.Kind.ShouldBe(FileConflict.NotRead);
        conflict.Message("shared:/plan.md").ShouldContain("have not read it");
    }

    [Fact]
    public void The_own_file_and_a_file_of_unknown_origin_may_be_overwritten_unread()
    {
        Write("a", "a's work");
        _ledger.CheckReplace("a", null, _file, "shared", Now).ShouldBeNull();

        // A file nobody wrote through the ledger — from before, or by a human.
        File.WriteAllText(_file, "put there by hand");
        _ledger.CheckReplace("b", null, _file, "shared", Now).ShouldBeNull();
    }

    [Fact]
    public void A_new_file_replaces_nothing()
        => _ledger.CheckReplace("b", null, Path.Combine(_dir, "new.md"), "shared", null).ShouldBeNull();

    [Fact]
    public void An_append_by_another_makes_an_older_read_stale()
    {
        _ledger.NoteRead("a", _file, Now);

        var before = Now;
        File.AppendAllText(_file, "\n+ b's line");
        _ledger.NoteAppend("b", "run-b", _file, before, Now);

        var conflict = _ledger.CheckReplace("a", null, _file, "shared", Now);
        conflict.ShouldNotBeNull("a's replace would drop b's appended line");
        conflict.OtherAgentId.ShouldBe("b");
    }

    [Fact]
    public void An_own_append_on_a_known_file_keeps_the_read_valid()
    {
        _ledger.NoteRead("a", _file, Now);
        var before = Now;
        File.AppendAllText(_file, "\n+ a's line");
        _ledger.NoteAppend("a", null, _file, before, Now);

        _ledger.CheckReplace("a", null, _file, "shared", Now).ShouldBeNull();
    }

    [Fact]
    public void A_change_by_hand_after_the_read_is_a_conflict_too()
    {
        _ledger.NoteRead("a", _file, Now);
        File.WriteAllText(_file, "edited by a human");

        var conflict = _ledger.CheckReplace("a", null, _file, "shared", Now);

        conflict.ShouldNotBeNull();
        conflict.OtherAgentId.ShouldBeNull();
        conflict.Message("shared:/plan.md").ShouldContain("someone else");
    }

    [Fact]
    public async Task Hotspots_are_files_with_repeated_conflicts()
    {
        var other = Path.Combine(_dir, "once.md");
        for (var i = 0; i < 3; i++)
            await _ledger.RecordAsync(new FileConflict(_file, "shared", "b", null, "a", null, FileConflict.ChangedSinceRead, DateTime.UtcNow), default);
        await _ledger.RecordAsync(new FileConflict(other, "shared", "c", null, null, null, FileConflict.NotRead, DateTime.UtcNow), default);
        await _ledger.RecordAsync(new FileConflict(_file, "shared", "b", null, "a", null, FileConflict.ChangedSinceRead, DateTime.UtcNow.AddDays(-30)), default);

        var hotspots = await _ledger.HotspotsAsync(DateTime.UtcNow.AddDays(-7), minimum: 3, limit: 10, default);

        hotspots.Count.ShouldBe(1);
        hotspots[0].Path.ShouldBe(_file);
        hotspots[0].Conflicts.ShouldBe(3, "the one from a month ago is outside the window");
        hotspots[0].Agents.ShouldBe(["a", "b"]);
    }

    [Fact]
    public async Task The_engine_audits_a_refused_write_as_a_conflict_not_an_error()
    {
        var audit = new InMemoryAuditRepository();
        var fixture = new EngineFixture(audit).WithTool(FakeTool.Conflicting("Conflict: plan.md was changed"));
        var agent = fixture.AddAgent("agent-a", "TestTool");
        fixture.Client.RespondsWithToolCall("TestTool").RespondsWithText("done");

        await fixture.Engine.RunAsync(agent, "go", "test-instance", default);

        audit.Entries.Single(e => e.Status != AuditStatus.Started).Status.ShouldBe(AuditStatus.Conflict);
    }

    [Fact]
    public async Task Tools_find_the_ledger_in_their_context()
    {
        Core.Tools.AgentToolContext? seen = null;
        var fixture = new EngineFixture().WithTool(FakeTool.Observing(c => seen = c));
        fixture.Engine.Files = _ledger;
        var agent = fixture.AddAgent("agent-a", "TestTool");
        fixture.Client.RespondsWithToolCall("TestTool").RespondsWithText("done");

        await fixture.Engine.RunAsync(agent, "go", "test-instance", default);

        seen!.Files.ShouldBeSameAs(_ledger);
        seen.RunId.ShouldNotBeNullOrWhiteSpace("a conflict names the run");
    }
}