using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using StellaOps.DependencyInjection;
using StellaOps.Notify.Engine;
using StellaOps.Notify.Models;

namespace StellaOps.Notify.Connectors.Slack;

[ServiceBinding(typeof(INotifyChannelTestProvider), ServiceLifetime.Singleton)]
public sealed class SlackChannelTestProvider : INotifyChannelTestProvider
{
    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);

    private static readonly string DefaultTitle = "Stella Ops Notify Preview";

    public NotifyChannelType ChannelType => NotifyChannelType.Slack;

    public Task<ChannelTestPreviewResult> BuildPreviewAsync(ChannelTestPreviewContext context, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();

        var title = !string.IsNullOrWhiteSpace(context.Request.Title)
            ? context.Request.Title!
            : DefaultTitle;
        var summary = !string.IsNullOrWhiteSpace(context.Request.Summary)
            ? context.Request.Summary!
            : $"Preview generated for Slack destination at {context.Timestamp:O}.";
        var bodyText = !string.IsNullOrWhiteSpace(context.Request.Body)
            ? context.Request.Body!
            : summary;
        var workspace = context.Channel.Config.Properties.TryGetValue("workspace", out var workspaceName)
            ? workspaceName
            : null;

        var contextElements = new List<object>
        {
            new { type = "mrkdwn", text = $"Preview generated {context.Timestamp:O} · Trace `{context.TraceId}`" }
        };

        if (!string.IsNullOrWhiteSpace(workspace))
        {
            contextElements.Add(new { type = "mrkdwn", text = $"Workspace: `{workspace}`" });
        }

        var payload = new
        {
            channel = context.Target,
            text = $"{title}\n{bodyText}",
            blocks = new object[]
            {
                new
                {
                    type = "section",
                    text = new { type = "mrkdwn", text = $"*{title}*\n{bodyText}" }
                },
                new
                {
                    type = "context",
                    elements = contextElements.ToArray()
                }
            }
        };

        var body = JsonSerializer.Serialize(payload, JsonOptions);

        var preview = NotifyDeliveryRendered.Create(
            NotifyChannelType.Slack,
            NotifyDeliveryFormat.Slack,
            context.Target,
            title,
            body,
            summary,
            context.Request.TextBody ?? bodyText,
            context.Request.Locale,
            ChannelTestPreviewUtilities.ComputeBodyHash(body),
            context.Request.Attachments);

        var metadata = SlackMetadataBuilder.Build(context);

        return Task.FromResult(new ChannelTestPreviewResult(preview, metadata));
    }
}