using System.Text;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
using Shouldly;
using Xunit;
using ZB.MOM.WW.Configuration;
using ZB.MOM.WW.OtOpcUa.Host.Configuration;
using ZB.MOM.WW.OtOpcUa.OpcUaServer;

namespace ZB.MOM.WW.OtOpcUa.Host.IntegrationTests;

/// <summary>
///     lmxopcua#879 — <c>ConfigurationBinder</c> appends configured collection items to a pre-filled list, so
///     <c>OpcUa:EnabledSecurityProfiles</c> could never drop <c>None</c>. These tests pin "the configured list REPLACES
///     the default" through the same <c>AddValidatedOptions</c> wiring <c>Program.cs</c> uses, for the indexed
///     (env-var / in-memory) form and the JSON array form, plus the unchanged default and the empty-list rule.
/// </summary>
public sealed class OpcUaSecurityProfilesBindingTests
{
    private static readonly OpcUaSecurityProfile[] AllThree =
    [
        OpcUaSecurityProfile.None,
        OpcUaSecurityProfile.Basic256Sha256Sign,
        OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt,
    ];

    private static IOptions<OpcUaApplicationHostOptions> Resolve(IConfiguration configuration, out ServiceProvider provider)
    {
        var services = new ServiceCollection();
        services.AddSingleton(configuration);
        services.AddValidatedOptions<OpcUaApplicationHostOptions, OpcUaApplicationHostOptionsValidator>(configuration, "OpcUa");
        provider = services.BuildServiceProvider();
        return provider.GetRequiredService<IOptions<OpcUaApplicationHostOptions>>();
    }

    /// <summary>The #879 repro: only the secure profiles configured gives exactly those, no None.</summary>
    [Fact]
    public void Configured_secure_profiles_replace_the_default_and_drop_None()
    {
        var configuration = new ConfigurationBuilder().AddInMemoryCollection(new Dictionary<string, string?>
        {
            ["OpcUa:EnabledSecurityProfiles:0"] = "Basic256Sha256SignAndEncrypt",
            ["OpcUa:EnabledSecurityProfiles:1"] = "Basic256Sha256Sign",
        }).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        options.Value.ResolveEnabledSecurityProfiles().ShouldBe(
            [OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt, OpcUaSecurityProfile.Basic256Sha256Sign]);
        options.Value.ResolveEnabledSecurityProfiles().ShouldNotContain(OpcUaSecurityProfile.None);
    }

    /// <summary>The JSON array form (appsettings.json, as docs/security.md shows) behaves the same as the indexed form.</summary>
    [Fact]
    public void Json_array_form_replaces_the_default_too()
    {
        var json = """{ "OpcUa": { "EnabledSecurityProfiles": [ "Basic256Sha256Sign", "Basic256Sha256SignAndEncrypt" ] } }""";
        var configuration = new ConfigurationBuilder()
            .AddJsonStream(new MemoryStream(Encoding.UTF8.GetBytes(json))).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        options.Value.ResolveEnabledSecurityProfiles().ShouldBe(
            [OpcUaSecurityProfile.Basic256Sha256Sign, OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt]);
    }

    /// <summary>The environment-variable form (<c>OpcUa__EnabledSecurityProfiles__0</c>) used by the Windows service gate.</summary>
    [Fact]
    public void Environment_variable_form_replaces_the_default()
    {
        const string prefix = "OTOPCUA_879_TEST_";
        Environment.SetEnvironmentVariable(prefix + "OpcUa__EnabledSecurityProfiles__0", "Basic256Sha256SignAndEncrypt");
        try
        {
            var configuration = new ConfigurationBuilder().AddEnvironmentVariables(prefix).Build();
            var options = Resolve(configuration, out var provider);
            using var sp = provider;

            options.Value.ResolveEnabledSecurityProfiles().ShouldBe([OpcUaSecurityProfile.Basic256Sha256SignAndEncrypt]);
        }
        finally { Environment.SetEnvironmentVariable(prefix + "OpcUa__EnabledSecurityProfiles__0", null); }
    }

    /// <summary>Configuring None explicitly alongside the secure profiles still works (an operator may want it).</summary>
    [Fact]
    public void Explicit_None_is_honoured_when_listed()
    {
        var configuration = new ConfigurationBuilder().AddInMemoryCollection(new Dictionary<string, string?>
        {
            ["OpcUa:EnabledSecurityProfiles:0"] = "None",
        }).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        options.Value.ResolveEnabledSecurityProfiles().ShouldBe([OpcUaSecurityProfile.None]);
    }

    /// <summary>Nothing configured: the three-profile default is applied, unchanged from before the fix.</summary>
    [Fact]
    public void Nothing_configured_keeps_the_three_profile_default()
    {
        var configuration = new ConfigurationBuilder().AddInMemoryCollection(new Dictionary<string, string?>
        {
            ["OpcUa:OpcUaPort"] = "4841", // a section exists, the list key does not
        }).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        options.Value.ResolveEnabledSecurityProfiles().ShouldBe(AllThree);
        new OpcUaApplicationHostOptions().ResolveEnabledSecurityProfiles().ShouldBe(AllThree);
    }

    /// <summary>An empty JSON array binds to nothing, i.e. "not configured": the default, never "None only".</summary>
    [Fact]
    public void Empty_json_array_is_treated_as_not_configured_and_yields_the_default()
    {
        var json = """{ "OpcUa": { "EnabledSecurityProfiles": [] } }""";
        var configuration = new ConfigurationBuilder()
            .AddJsonStream(new MemoryStream(Encoding.UTF8.GetBytes(json))).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        options.Value.ResolveEnabledSecurityProfiles().ShouldBe(AllThree);
    }

    /// <summary>A list that is set but empty fails startup validation and cannot be resolved — it never means "None".</summary>
    [Fact]
    public void An_explicitly_empty_list_fails_validation_and_resolution()
    {
        var empty = new OpcUaApplicationHostOptions { EnabledSecurityProfiles = new List<OpcUaSecurityProfile>() };

        new OpcUaApplicationHostOptionsValidator().Validate(null, empty).Failed.ShouldBeTrue();
        Should.Throw<InvalidOperationException>(() => empty.ResolveEnabledSecurityProfiles());
    }

    /// <summary>An unparseable profile name fails startup rather than being ignored (which would otherwise leave the default).</summary>
    [Fact]
    public void An_unknown_profile_name_fails_options_resolution()
    {
        var configuration = new ConfigurationBuilder().AddInMemoryCollection(new Dictionary<string, string?>
        {
            ["OpcUa:EnabledSecurityProfiles:0"] = "Basic256Sha256-SignAndEncrypt",
        }).Build();

        var options = Resolve(configuration, out var provider);
        using var sp = provider;

        Should.Throw<Exception>(() => _ = options.Value.ResolveEnabledSecurityProfiles());
    }
}