using System.Reflection;
using ZB.MOM.WW.ScadaBridge.ScriptAnalysis;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;

namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Scripts;

/// <summary>
/// M3.3: compile-surface parity guard. The shared
/// <see cref="ScriptCompileSurface"/> / <see cref="TriggerCompileSurface"/> are
/// compile-only stubs the design-time deploy gate binds candidate scripts
/// against; they must mirror the real SiteRuntime <see cref="ScriptGlobals"/> /
/// <see cref="TriggerExpressionGlobals"/> bind surfaces. If a member a script can
/// reference on the real globals is missing from the compile surface, a script
/// that uses it would pass the design-time gate but fail at the site — so the
/// compile surface's public top-level member NAMES must be a SUPERSET of the
/// real globals' names. This test fails loudly (listing the missing names) when
/// the surface drifts behind the runtime globals.
///
/// <para>
/// Top-level member-name parity is sufficient: the design-time compile against
/// the surface catches deeper signature mismatches itself; this guard only
/// ensures every entry point a script can name on the real globals exists on the
/// stub.
/// </para>
/// </summary>
public class CompileSurfaceParityTests
{
    [Fact]
    public void ScriptCompileSurface_MemberNames_AreSupersetOf_ScriptGlobals()
    {
        AssertSurfaceCoversGlobals(
            surface: typeof(ScriptCompileSurface),
            globals: typeof(ScriptGlobals));
    }

    [Fact]
    public void TriggerCompileSurface_MemberNames_AreSupersetOf_TriggerExpressionGlobals()
    {
        AssertSurfaceCoversGlobals(
            surface: typeof(TriggerCompileSurface),
            globals: typeof(TriggerExpressionGlobals));
    }

    /// <summary>
    /// Asserts that the public instance property + method member names of
    /// <paramref name="surface"/> are a superset of those of
    /// <paramref name="globals"/>. Inherited <see cref="object"/> members
    /// (ToString/GetHashCode/Equals/GetType) are excluded. Fails with the exact
    /// list of missing names when the surface does not cover the globals.
    /// </summary>
    private static void AssertSurfaceCoversGlobals(Type surface, Type globals)
    {
        var surfaceNames = PublicInstanceMemberNames(surface);
        var globalsNames = PublicInstanceMemberNames(globals);

        var missing = globalsNames
            .Where(name => !surfaceNames.Contains(name))
            .OrderBy(name => name, StringComparer.Ordinal)
            .ToList();

        Assert.True(
            missing.Count == 0,
            $"Compile surface '{surface.Name}' is missing {missing.Count} member name(s) "
            + $"present on '{globals.Name}': {string.Join(", ", missing)}. "
            + "The compile-only surface must mirror the runtime globals — add the "
            + "missing member(s) to the ScriptAnalysis surface type.");
    }

    /// <summary>
    /// Public instance property + method member names declared on or inherited by
    /// <paramref name="type"/>, excluding the inherited <see cref="object"/>
    /// members (ToString, GetHashCode, Equals, GetType) so only script-reachable
    /// API names remain. Property/method names are compared (no signatures).
    /// </summary>
    private static HashSet<string> PublicInstanceMemberNames(Type type)
    {
        const BindingFlags flags = BindingFlags.Public | BindingFlags.Instance;

        var objectMembers = new HashSet<string>(StringComparer.Ordinal)
        {
            nameof(ToString),
            nameof(GetHashCode),
            nameof(Equals),
            nameof(GetType),
        };

        var names = new HashSet<string>(StringComparer.Ordinal);

        foreach (var property in type.GetProperties(flags))
            names.Add(property.Name);

        foreach (var method in type.GetMethods(flags))
        {
            // Skip compiler-generated property accessors (get_X / set_X) — the
            // property itself is already counted by name above.
            if (method.IsSpecialName)
                continue;
            if (objectMembers.Contains(method.Name))
                continue;
            names.Add(method.Name);
        }

        return names;
    }
}