using ControlPlane.Api.Services;
using ControlPlane.Core.Models;
using System.Text.Json;

namespace ControlPlane.Api.Endpoints;

public static class PromotionEndpoints
{
    private static readonly JsonSerializerOptions JsonOpts = new(JsonSerializerDefaults.Web);

    public static IEndpointRouteBuilder MapPromotionEndpoints(this IEndpointRouteBuilder app)
    {
        var g = app.MapGroup("/api/promotions").WithTags("Promotions");

        // GET /api/promotions/ladder  — branch status for all 4 ladder branches
        g.MapGet("/ladder", async (PromotionService svc, CancellationToken ct) =>
            Results.Ok(await svc.GetLadderStatusAsync(ct)));

        // GET /api/promotions/history
        g.MapGet("/history", async (PromotionService svc) =>
            Results.Ok(await svc.GetHistoryAsync()));

        // POST /api/promotions/promote  — body: { from, to, requestedBy, note }
        // Streams SSE log lines then sends {done, promotion} when complete
        g.MapPost("/promote", async (
            HttpContext ctx,
            PromotionService svc,
            PromoteRequest req,
            CancellationToken ct) =>
        {
            // Validate ladder step
            var ladder = PromotionService.Ladder;
            var fi = Array.IndexOf(ladder, req.From);
            var ti = Array.IndexOf(ladder, req.To);
            if (fi < 0 || ti < 0 || ti != fi + 1)
            {
                ctx.Response.StatusCode = 400;
                await ctx.Response.WriteAsJsonAsync(
                    new { error = $"Invalid promotion step: {req.From} → {req.To}. Must be adjacent in ladder." }, ct);
                return;
            }

            ctx.Response.Headers.ContentType  = "text/event-stream";
            ctx.Response.Headers.CacheControl = "no-cache";
            ctx.Response.Headers.Connection   = "keep-alive";

            var channel = System.Threading.Channels.Channel.CreateUnbounded<string?>(
                new System.Threading.Channels.UnboundedChannelOptions { SingleWriter = true, SingleReader = true });

            void OnLine(string line) => channel.Writer.TryWrite(line);

            var promoteTask = Task.Run(() =>
                svc.PromoteAsync(req.From, req.To, req.RequestedBy ?? "system", req.Note, OnLine, ct), ct)
                .ContinueWith(t => channel.Writer.TryComplete(t.Exception), TaskScheduler.Default);

            await foreach (var line in channel.Reader.ReadAllAsync(ct))
            {
                var json = JsonSerializer.Serialize(new { line }, JsonOpts);
                await ctx.Response.WriteAsync($"data: {json}\n\n", ct);
                await ctx.Response.Body.FlushAsync(ct);
            }

            var promotion = await promoteTask;
            var doneJson  = JsonSerializer.Serialize(new { done = true, promotion }, JsonOpts);
            await ctx.Response.WriteAsync($"data: {doneJson}\n\n", ct);
            await ctx.Response.Body.FlushAsync(ct);
        });

        return app;
    }
}

public record PromoteRequest(string From, string To, string? RequestedBy, string? Note);