// Invoices by the gap-free counter: keep one integer, read what was issued after it, book, ack.
using System.Text.Json.Nodes;

namespace Slflo.Samples;

public sealed class SeqState
{
    public long? LastSeq { get; set; }
}

public static class InvoicesBySeq
{
    public static async Task<Dictionary<string, object?>> RunAsync(SlfloClient api)
    {
        var state = StateFiles.Load<SeqState>("seq-cs.json");
        var erp = FakeErp.Open();
        if (state.LastSeq is null)
        {
            // First run: start from now, not from the company's whole history.
            var cursor = await api.GetAsync("/invoices/cursor");
            state.LastSeq = cursor["data"]!["last_seq"]!.GetValue<long>();
            StateFiles.Save("seq-cs.json", state);
        }

        var read = 0;
        object? gap = null;
        while (gap is null)
        {
            var page = await api.GetAsync("/invoices", new Dictionary<string, object> { ["filter[seq_after]"] = state.LastSeq, ["per_page"] = 100 });
            var items = new JsonArray();
            foreach (var invoice in page["data"]!.AsArray())
            {
                var seq = invoice!["seq"]!.GetValue<long>();
                if (seq != state.LastSeq + 1) { gap = new { expected = state.LastSeq + 1, got = seq }; break; } // alert
                var id = invoice["id"]!.GetValue<string>();
                var journal = erp.PostJournal("invoice", id, invoice["version"]!.GetValue<long>());
                items.Add(new JsonObject { ["id"] = id, ["outcome"] = "ACCEPTED", ["external_ref"] = journal, ["external_number"] = journal });
                state.LastSeq = seq;
                read++;
            }
            if (items.Count > 0)
            {
                var first = items[0]!["id"]!.GetValue<string>();
                await api.PostAsync("/acks", new JsonObject { ["entity"] = "invoice", ["items"] = items }, $"invoice-acks:{first}:{state.LastSeq}");
            }
            StateFiles.Save("seq-cs.json", state);
            if (!page["meta"]!["has_more"]!.GetValue<bool>()) break;
        }
        return new() { ["read"] = read, ["last_seq"] = state.LastSeq, ["gap"] = gap };
    }
}