using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Core.Resilience;

namespace ZB.MOM.WW.OtOpcUa.Core.Tests.Resilience;

[Trait("Category", "Unit")]
public sealed class DriverResilienceOptionsTests
{
    /// <summary>Verifies that tier defaults cover every capability.</summary>
    /// <param name="tier">The driver tier to test.</param>
    [Theory]
    [InlineData(DriverTier.A)]
    [InlineData(DriverTier.B)]
    [InlineData(DriverTier.C)]
    public void TierDefaults_Cover_EveryCapability(DriverTier tier)
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(tier);

        foreach (var capability in Enum.GetValues<DriverCapability>())
            defaults.ShouldContainKey(capability);
    }

    /// <summary>Verifies that write never retries by default.</summary>
    /// <param name="tier">The driver tier to test.</param>
    [Theory]
    [InlineData(DriverTier.A)]
    [InlineData(DriverTier.B)]
    [InlineData(DriverTier.C)]
    public void Write_NeverRetries_ByDefault(DriverTier tier)
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(tier);
        defaults[DriverCapability.Write].RetryCount.ShouldBe(0);
    }

    /// <summary>Verifies that alarm acknowledge never retries by default.</summary>
    /// <param name="tier">The driver tier to test.</param>
    [Theory]
    [InlineData(DriverTier.A)]
    [InlineData(DriverTier.B)]
    [InlineData(DriverTier.C)]
    public void AlarmAcknowledge_NeverRetries_ByDefault(DriverTier tier)
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(tier);
        defaults[DriverCapability.AlarmAcknowledge].RetryCount.ShouldBe(0);
    }

    /// <summary>Verifies that idempotent capabilities retry by default.</summary>
    /// <param name="tier">The driver tier to test.</param>
    /// <param name="capability">The driver capability to test.</param>
    [Theory]
    [InlineData(DriverTier.A, DriverCapability.Read)]
    [InlineData(DriverTier.A, DriverCapability.HistoryRead)]
    [InlineData(DriverTier.B, DriverCapability.Discover)]
    [InlineData(DriverTier.B, DriverCapability.Probe)]
    [InlineData(DriverTier.C, DriverCapability.AlarmSubscribe)]
    public void IdempotentCapabilities_Retry_ByDefault(DriverTier tier, DriverCapability capability)
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(tier);
        defaults[capability].RetryCount.ShouldBeGreaterThan(0);
    }

    /// <summary>Verifies that TierC disables circuit breaker deferring to supervisor.</summary>
    [Fact]
    public void TierC_DisablesCircuitBreaker_DeferringToSupervisor()
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(DriverTier.C);

        foreach (var (_, policy) in defaults)
            policy.BreakerFailureThreshold.ShouldBe(0, "Tier C breaker is handled by the Proxy supervisor (decision #68)");
    }

    /// <summary>Verifies that TierA and TierB enable circuit breaker.</summary>
    /// <param name="tier">The driver tier to test.</param>
    [Theory]
    [InlineData(DriverTier.A)]
    [InlineData(DriverTier.B)]
    public void TierAAndB_EnableCircuitBreaker(DriverTier tier)
    {
        var defaults = DriverResilienceOptions.GetTierDefaults(tier);

        foreach (var (_, policy) in defaults)
            policy.BreakerFailureThreshold.ShouldBeGreaterThan(0);
    }

    /// <summary>Verifies that resolve uses tier defaults when no override is set.</summary>
    [Fact]
    public void Resolve_Uses_TierDefaults_When_NoOverride()
    {
        var options = new DriverResilienceOptions { Tier = DriverTier.A };

        var resolved = options.Resolve(DriverCapability.Read);

        resolved.ShouldBe(DriverResilienceOptions.GetTierDefaults(DriverTier.A)[DriverCapability.Read]);
    }

    /// <summary>Verifies that resolve uses override when configured.</summary>
    [Fact]
    public void Resolve_Uses_Override_When_Configured()
    {
        var custom = new CapabilityPolicy(TimeoutSeconds: 42, RetryCount: 7, BreakerFailureThreshold: 9);
        var options = new DriverResilienceOptions
        {
            Tier = DriverTier.A,
            CapabilityPolicies = new Dictionary<DriverCapability, CapabilityPolicy>
            {
                [DriverCapability.Read] = custom,
            },
        };

        options.Resolve(DriverCapability.Read).ShouldBe(custom);
        options.Resolve(DriverCapability.Write).ShouldBe(
            DriverResilienceOptions.GetTierDefaults(DriverTier.A)[DriverCapability.Write]);
    }

    /// <summary>
    ///     Core-010 regression: every <see cref="DriverCapability"/> value must successfully resolve
    ///     under every tier with a default <see cref="DriverResilienceOptions"/>. A future
    ///     enum-only addition that forgets to update <c>GetTierDefaults</c> would otherwise blow up
    ///     on the hot path with <see cref="KeyNotFoundException"/>.
    /// </summary>
    /// <param name="tier">The driver tier to test.</param>
    [Theory]
    [InlineData(DriverTier.A)]
    [InlineData(DriverTier.B)]
    [InlineData(DriverTier.C)]
    public void Resolve_Returns_NonNull_Policy_For_Every_Capability(DriverTier tier)
    {
        var options = new DriverResilienceOptions { Tier = tier };

        foreach (var capability in Enum.GetValues<DriverCapability>())
        {
            var policy = options.Resolve(capability);
            policy.ShouldNotBeNull(
                $"every DriverCapability must resolve to a non-null policy for tier {tier} — {capability} did not");
        }
    }

    /// <summary>
    ///     Core-010 regression: when a capability is somehow missing from BOTH the override
    ///     map and the tier defaults (defensive — should be impossible thanks to the
    ///     <c>TierDefaults_Cover_EveryCapability</c> invariant, but is the failure mode the
    ///     finding flagged), <c>Resolve</c> must throw a diagnostic <see cref="KeyNotFoundException"/>
    ///     that names the missing capability and tier — not a bare lookup failure.
    /// </summary>
    [Fact]
    public void Resolve_Throws_Diagnostic_When_Capability_Missing_From_Tier_Defaults()
    {
        // Use a CapabilityPolicies dict that purposely omits one capability and use reflection
        // to confirm the message names the capability when the tier defaults also omit it.
        // We can't easily mutate GetTierDefaults so we exercise the documented behavior on a
        // synthetic non-tier-known capability (we cast an out-of-range enum value).
        var options = new DriverResilienceOptions { Tier = DriverTier.A };
        var bogus = (DriverCapability)int.MaxValue;

        var ex = Should.Throw<KeyNotFoundException>(() => options.Resolve(bogus));
        ex.Message.ShouldContain(bogus.ToString());
        ex.Message.ShouldContain(DriverTier.A.ToString());
        ex.Message.ShouldContain(nameof(DriverResilienceOptions.GetTierDefaults));
    }
}