using System.Text.Json;
using Campaign_Tracker.Server.Audit;
using Microsoft.Extensions.Logging.Abstractions;

namespace Campaign_Tracker.Server.Tests;

public sealed class AuditServiceTests : IDisposable
{
    private readonly string _tmpDir;
    private readonly AppendOnlyFileAuditService _service;

    public AuditServiceTests()
    {
        _tmpDir = Path.Combine(Path.GetTempPath(), $"ct-audit-test-{Guid.NewGuid()}");
        _service = new AppendOnlyFileAuditService(_tmpDir, NullLogger<AppendOnlyFileAuditService>.Instance);
    }

    public void Dispose()
    {
        if (Directory.Exists(_tmpDir))
        {
            Directory.Delete(_tmpDir, recursive: true);
        }
    }

    // AC #1 — required fields are written to the file

    [Fact]
    public void Record_WritesAllRequiredFieldsToFile_AC1()
    {
        var at = new DateTimeOffset(2026, 5, 5, 10, 0, 0, TimeSpan.Zero);
        var auditEvent = new AuditEvent(
            AuditEventType.SessionLogin,
            "alice@example.test",
            "authentication",
            "success",
            "trace-abc",
            at);

        _service.Record(auditEvent);

        var filePath = _service.GetDailyFilePath(at);
        Assert.True(File.Exists(filePath));
        var line = File.ReadAllLines(filePath).Single();
        Assert.Contains("SESSION_LOGIN", line);
        Assert.Contains("alice@example.test", line);
        Assert.Contains("authentication", line);
        Assert.Contains("success", line);
        Assert.Contains("trace-abc", line);
        Assert.Contains("2026-05-05", line);
    }

    [Fact]
    public void Record_NormalizesTimestampToUtc_AC1()
    {
        var at = new DateTimeOffset(2026, 5, 5, 23, 59, 0, TimeSpan.FromHours(5)); // UTC+5
        var auditEvent = new AuditEvent(
            AuditEventType.SessionLogout, "bob", "authentication/logout", "success", "t1", at);

        _service.Record(auditEvent);

        var filePath = _service.GetDailyFilePath(at);
        var line = File.ReadAllLines(filePath).Single();

        using var doc = JsonDocument.Parse(line);
        var recorded = doc.RootElement.GetProperty("recordedAt").GetDateTimeOffset();
        Assert.Equal(TimeSpan.Zero, recorded.Offset);
        Assert.Equal(at.ToUniversalTime(), recorded);
    }

    [Theory]
    [InlineData(null, "actor", "resource", "success", "trace")]
    [InlineData("", "actor", "resource", "success", "trace")]
    [InlineData("SESSION_LOGIN", "", "resource", "success", "trace")]
    [InlineData("SESSION_LOGIN", "actor", " ", "success", "trace")]
    [InlineData("SESSION_LOGIN", "actor", "resource", "", "trace")]
    [InlineData("SESSION_LOGIN", "actor", "resource", "success", "")]
    public void Record_RejectsIncompleteAuditEvents_AC1(
        string? eventType,
        string actor,
        string resource,
        string outcome,
        string traceIdentifier)
    {
        var auditEvent = new AuditEvent(
            eventType!,
            actor,
            resource,
            outcome,
            traceIdentifier,
            DateTimeOffset.UtcNow);

        Assert.ThrowsAny<ArgumentException>(() => _service.Record(auditEvent));
    }

    // AC #2 — files are never deleted (365-day retention)

    [Fact]
    public void Record_NeverDeletesFiles_FilesAccumulateForRetention_AC2()
    {
        var day1 = new DateTimeOffset(2025, 11, 1, 0, 0, 0, TimeSpan.Zero);
        var day2 = new DateTimeOffset(2026, 5, 5, 0, 0, 0, TimeSpan.Zero);

        _service.Record(new AuditEvent("X", "u", "r", "ok", "t", day1));
        _service.Record(new AuditEvent("X", "u", "r", "ok", "t", day2));

        // Both daily files are present — none deleted
        Assert.True(File.Exists(_service.GetDailyFilePath(day1)));
        Assert.True(File.Exists(_service.GetDailyFilePath(day2)));
        Assert.Equal(2, Directory.GetFiles(_tmpDir, "*.jsonl").Length);
    }

    // AC #3 — shared service contract: GetRecent returns what was recorded

    [Fact]
    public void GetRecent_ReturnsRecordedEvents_SharedServiceSatisfied_AC3()
    {
        var at = DateTimeOffset.UtcNow;
        _service.Record(new AuditEvent(AuditEventType.SessionLogin, "alice", "auth", "success", "t1", at));
        _service.Record(new AuditEvent(AuditEventType.SessionLogout, "bob", "auth/logout", "success", "t2", at));

        var recent = _service.GetRecent();

        Assert.Equal(2, recent.Count);
        Assert.Contains(recent, e => e.ActorIdentity == "alice" && e.EventType == AuditEventType.SessionLogin);
        Assert.Contains(recent, e => e.ActorIdentity == "bob" && e.EventType == AuditEventType.SessionLogout);
    }

    [Fact]
    public void GetRecent_WithNegativeCount_ThrowsArgumentOutOfRange()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => _service.GetRecent(-1));
    }

    // AC #4 — append-only: interface has no update or delete methods

    [Fact]
    public void IAuditService_HasNoUpdateOrDeleteMethods_AppendOnlyInterface_AC4()
    {
        var publicMethods = typeof(IAuditService).GetMethods()
            .Select(m => m.Name)
            .ToArray();

        Assert.DoesNotContain(publicMethods, name =>
            name.StartsWith("Delete", StringComparison.OrdinalIgnoreCase) ||
            name.StartsWith("Remove", StringComparison.OrdinalIgnoreCase) ||
            name.StartsWith("Update", StringComparison.OrdinalIgnoreCase) ||
            name.StartsWith("Modify", StringComparison.OrdinalIgnoreCase) ||
            name.StartsWith("Purge", StringComparison.OrdinalIgnoreCase));
    }

    [Fact]
    public void Record_MultipleEvents_AllAppendedToFile_NoPreviousLineOverwritten_AC4()
    {
        var at = new DateTimeOffset(2026, 5, 5, 12, 0, 0, TimeSpan.Zero);
        _service.Record(new AuditEvent("E1", "user1", "r", "ok", "t1", at));
        _service.Record(new AuditEvent("E2", "user2", "r", "ok", "t2", at));
        _service.Record(new AuditEvent("E3", "user3", "r", "ok", "t3", at));

        var lines = File.ReadAllLines(_service.GetDailyFilePath(at));

        Assert.Equal(3, lines.Length);
        Assert.Contains("E1", lines[0]);
        Assert.Contains("E2", lines[1]);
        Assert.Contains("E3", lines[2]);
    }

    // AC #5 — audit service unavailable: Record throws, caller is blocked

    [Fact]
    public void Record_ThrowsAuditServiceUnavailableException_WhenDirectoryIsDeleted_AC5()
    {
        // Record one event to ensure directory exists, then delete it to simulate unavailability.
        var at = DateTimeOffset.UtcNow;
        _service.Record(new AuditEvent("X", "u", "r", "ok", "t", at));
        Directory.Delete(_tmpDir, recursive: true);

        Assert.Throws<AuditServiceUnavailableException>(() =>
            _service.Record(new AuditEvent("X", "u", "r", "ok", "t", at)));
    }

    [Fact]
    public void Record_WhenThrown_ExceptionInnerCauseIsFileSystemException_AC5()
    {
        var at = DateTimeOffset.UtcNow;
        _service.Record(new AuditEvent("X", "u", "r", "ok", "t", at));
        Directory.Delete(_tmpDir, recursive: true);

        var ex = Assert.Throws<AuditServiceUnavailableException>(() =>
            _service.Record(new AuditEvent("X", "u", "r", "ok", "t", at)));

        Assert.NotNull(ex.InnerException);
        Assert.IsAssignableFrom<IOException>(ex.InnerException);
    }
}