using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.Secrets.Abstractions;
using ZB.MOM.WW.Secrets.Configuration;

namespace ZB.MOM.WW.Secrets.Tests.Configuration;

/// <summary>
/// scadaproj#32 (Secrets-003): a configuration reload must not revert <c>${secret:}</c> expansion
/// to the placeholder text. Before the fix the expander wrote into the providers' in-memory data, and
/// a file provider's <c>Load()</c> replaces that data, so the next <c>appsettings.json</c> reload put
/// <c>Password=${secret:…}</c> back into every reader's hands.
/// </summary>
public sealed class SecretExpansionReloadTests : IDisposable
{
    private readonly string _dir = Path.Combine(Path.GetTempPath(), $"zb-reload-{Guid.NewGuid():N}");

    public SecretExpansionReloadTests() => Directory.CreateDirectory(_dir);

    private sealed class FixedResolver(Dictionary<string, string> values) : ISecretResolver
    {
        public Task<string?> GetAsync(SecretName name, CancellationToken ct) =>
            Task.FromResult(values.TryGetValue(name.Value, out string? v) ? v : null);
    }

    private static SecretReferenceExpander Expander() =>
        new(new FixedResolver(new Dictionary<string, string> { ["db/pw"] = "hunter2" }));

    private string WriteSettings(string level)
    {
        string path = Path.Combine(_dir, "appsettings.json");
        File.WriteAllText(path, $$"""
            { "Cs": "Server=s;Password=${secret:db/pw}", "Opts": { "Cs": "pw=${secret:db/pw}", "Level": "{{level}}" } }
            """);
        return path;
    }

    private sealed class Opts
    {
        public string? Cs { get; set; }

        public string? Level { get; set; }
    }

    [Fact]
    public async Task ConfigurationManager_keeps_the_expansion_through_a_reload()
    {
        // The shape every family host uses: builder.Configuration is a ConfigurationManager.
        var config = new ConfigurationManager();
        config.AddJsonFile(WriteSettings("Info"), optional: false, reloadOnChange: false);

        await Expander().ExpandConfigurationAsync(config, CancellationToken.None);
        Assert.Equal("Server=s;Password=hunter2", config["Cs"]);

        ((IConfigurationRoot)config).Reload();

        Assert.Equal("Server=s;Password=hunter2", config["Cs"]);
    }

    [Fact]
    public async Task An_options_monitor_rebinds_to_the_expanded_value_and_unrelated_keys_still_reload()
    {
        var config = new ConfigurationManager();
        string path = WriteSettings("Info");
        config.AddJsonFile(path, optional: false, reloadOnChange: false);
        await Expander().ExpandConfigurationAsync(config, CancellationToken.None);

        var services = new ServiceCollection();
        services.Configure<Opts>(config.GetSection("Opts"));
        using ServiceProvider provider = services.BuildServiceProvider();
        IOptionsMonitor<Opts> monitor = provider.GetRequiredService<IOptionsMonitor<Opts>>();
        Assert.Equal("pw=hunter2", monitor.CurrentValue.Cs);

        // The operator edits a log level on a running service.
        WriteSettings("Debug");
        ((IConfigurationRoot)config).Reload();

        Assert.Equal("Debug", monitor.CurrentValue.Level);       // the edit took effect...
        Assert.Equal("pw=hunter2", monitor.CurrentValue.Cs);     // ...and the credential survived it
    }

    [Fact]
    public async Task A_plain_root_reapplies_the_expansion_after_a_reload()
    {
        IConfigurationRoot config = new ConfigurationBuilder()
            .AddJsonFile(WriteSettings("Info"), optional: false, reloadOnChange: false)
            .Build();

        await Expander().ExpandConfigurationAsync(config, CancellationToken.None);
        ((IConfigurationRoot)config).Reload();

        Assert.Equal("Server=s;Password=hunter2", config["Cs"]);
    }

    [Fact]
    public async Task A_missing_secret_fails_closed_without_expanding_anything()
    {
        var config = new ConfigurationManager();
        config.AddInMemoryCollection(new Dictionary<string, string?>
        {
            ["A"] = "${secret:db/pw}",
            ["B"] = "${secret:db/absent}",
        });

        await Assert.ThrowsAsync<SecretNotFoundException>(
            () => Expander().ExpandConfigurationAsync(config, CancellationToken.None));

        Assert.Equal("${secret:db/pw}", config["A"]);
    }

    public void Dispose() => Directory.Delete(_dir, recursive: true);
}