// The samples keep their state in small JSON files under STATE_DIR (default ./state). A real
// connector keeps the same things in its own tables: the watermark, a staging table with a
// unique key on (order id, version, line number), and the ERP's own documents.
using System.Text.Json;

namespace Slflo.Samples;

public static class StateFiles
{
    private static readonly string Dir = Environment.GetEnvironmentVariable("STATE_DIR") ?? "state";

    public static T Load<T>(string name) where T : new()
    {
        var path = Path.Combine(Dir, name);
        return File.Exists(path) ? JsonSerializer.Deserialize<T>(File.ReadAllText(path)) ?? new T() : new T();
    }

    public static void Save<T>(string name, T value)
    {
        Directory.CreateDirectory(Dir);
        File.WriteAllText(Path.Combine(Dir, name), JsonSerializer.Serialize(value));
    }
}

/// <summary>A stand-in for your ERP's books: sales orders by their customer reference, and journals.</summary>
public sealed class FakeErp
{
    public Dictionary<string, string> SalesOrders { get; set; } = new(); // customer reference (the Slflo order id) -> SO number
    public Dictionary<string, string> Journals { get; set; } = new();    // "kind:id:version" -> journal number

    // Numbers far from the Python stand-in's, since both answer the same sandbox company and
    // one ERP number can belong to one Slflo record only (409 EXTERNAL_REF_CONFLICT).
    private const int FirstNumber = 500_000;

    public static FakeErp Open() => StateFiles.Load<FakeErp>("erp-cs.json");
    public void Save() => StateFiles.Save("erp-cs.json", this);

    public static bool OnHold(string account) =>
        (Environment.GetEnvironmentVariable("ERP_ON_HOLD") ?? "").Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries).Contains(account);

    public string? FindSalesOrder(string customerReference) => SalesOrders.GetValueOrDefault(customerReference);

    public string CreateSalesOrder(string customerReference)
    {
        var number = $"SO-{SalesOrders.Count + 1 + FirstNumber:D7}";
        SalesOrders[customerReference] = number;
        Save();
        return number;
    }

    public string PostJournal(string kind, string id, long version)
    {
        var key = $"{kind}:{id}:{version}";
        if (!Journals.TryGetValue(key, out var number))
        {
            number = $"JRN-{Journals.Count + 1 + FirstNumber:D6}";
            Journals[key] = number;
            Save();
        }
        return number;
    }
}