using System.Text.Json;
using FluentAssertions;
using Workflow.Api.Serialization;
using Xunit;

namespace Workflow.Tests.Serialization;

/// <summary>
/// 验证统一数据规范：DateTime / DateTimeOffset 序列化为 UTC 毫秒时间戳（long）。
/// 这是第二期"后端数据规范统一"的核心契约 —— 后端只输出毫秒时间戳，时区/格式化交给前端。
/// </summary>
public class TimestampJsonConverterTests
{
    private static JsonSerializerOptions BuildOptions() => new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        Converters = { new TimestampDateTimeConverter(), new TimestampDateTimeOffsetConverter() }
    };

    private class SampleDto
    {
        public Guid Id { get; set; }
        public DateTime CreatedAt { get; set; }
        public DateTimeOffset? UpdatedAt { get; set; }
    }

    [Fact]
    public void DateTime_serializes_to_millisecond_epoch_number()
    {
        // 固定时刻：2026-06-14T03:30:00Z
        var utc = new DateTime(2026, 6, 14, 3, 30, 0, DateTimeKind.Utc);
        var expectedMs = new DateTimeOffset(utc, TimeSpan.Zero).ToUnixTimeMilliseconds();

        var dto = new SampleDto { Id = Guid.NewGuid(), CreatedAt = utc };
        var json = JsonSerializer.Serialize(dto, BuildOptions());

        using var doc = JsonDocument.Parse(json);
        doc.RootElement.GetProperty("createdAt").ValueKind.Should().Be(JsonValueKind.Number);
        doc.RootElement.GetProperty("createdAt").GetInt64().Should().Be(expectedMs);
    }

    [Fact]
    public void DateTimeOffset_serializes_to_millisecond_epoch_number()
    {
        var dto = new DateTimeOffset(2026, 1, 2, 3, 4, 5, TimeSpan.Zero);
        var expectedMs = dto.ToUnixTimeMilliseconds();

        var json = JsonSerializer.Serialize(new { t = dto }, BuildOptions());

        using var doc = JsonDocument.Parse(json);
        doc.RootElement.GetProperty("t").GetInt64().Should().Be(expectedMs);
    }

    [Fact]
    public void Guid_serializes_as_string()
    {
        // 验证 ID 统一为字符串（Guid 天然序列化为字符串，无需额外转换器）
        var id = Guid.NewGuid();
        var dto = new SampleDto { Id = id };
        var json = JsonSerializer.Serialize(dto, BuildOptions());

        using var doc = JsonDocument.Parse(json);
        doc.RootElement.GetProperty("id").ValueKind.Should().Be(JsonValueKind.String);
        doc.RootElement.GetProperty("id").GetGuid().Should().Be(id);
    }

    [Fact]
    public void Deserializes_epoch_number_back_to_utc_dateTime()
    {
        var utc = new DateTime(2026, 6, 14, 3, 30, 0, DateTimeKind.Utc);
        var ms = new DateTimeOffset(utc, TimeSpan.Zero).ToUnixTimeMilliseconds();
        var json = $$"""{"id":"00000000-0000-0000-0000-000000000000","createdAt":{{ms}}}""";

        var dto = JsonSerializer.Deserialize<SampleDto>(json, BuildOptions())!;

        dto.CreatedAt.Should().Be(utc);
        dto.CreatedAt.Kind.Should().Be(DateTimeKind.Utc);
    }

    [Fact]
    public void Deserializes_legacy_iso_string_for_backward_compatibility()
    {
        // 旧客户端/旧数据可能仍是 ISO 字符串，必须能读回（向后兼容）
        var json = """{"id":"00000000-0000-0000-0000-000000000000","createdAt":"2026-06-14T03:30:00Z"}""";

        var dto = JsonSerializer.Deserialize<SampleDto>(json, BuildOptions())!;

        dto.CreatedAt.Should().Be(new DateTime(2026, 6, 14, 3, 30, 0, DateTimeKind.Utc));
    }
}