using System;
using System.IO;
using System.Linq;
using System.Linq;
using System.Reflection;
using Xunit;
using ytLive.Helpers;
using ytLive.ViewModels;

namespace ytLive.Tests;

/// <summary>
/// Good Dog (2026-09-26): in DEBUG, two LlamaCasty processes must be able to run side by
/// side without fighting over state, because pre-1.0 the creator streams in one and
/// screen-captures it from the other.
/// <para>Nothing in the app prevented a second instance — there is no single-instance
/// mutex and no port. What broke it was SHARED STATE, in two ways that are hard
/// failures rather than annoyances: the whole-scene read/write layout DB (two instances
/// clobber each other's saves) and Chromium's exclusive lock on the WebView2 user data
/// folder (the second instance of the same exe does not start).</para>
/// <para>These facts live with the tests on purpose. The app's side is a
/// <c>#if DEBUG</c> block in <see cref="InstanceProfile"/>; this file is the harness that
/// exercises it, and — the part that matters at 1.0 — the assertion that a Release
/// build cannot possibly contain it.</para>
/// </summary>
public sealed class InstanceIsolationTests
{
    // ---------- two identities get two private roots ----------

    [Fact]
    public void TwoInstances_EachGetTheirOwnLayoutDatabase()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            var roots = new string[2];
            for (var i = 0; i < 2; i++)
            {
                Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, $"{i + 1}");
                roots[i] = InstanceProfile.DataRoot;
            }

            Assert.NotEqual(roots[0], roots[1]);
            foreach (var root in roots)
                Assert.NotEqual(InstanceProfile.DefaultRoot, root);
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    [Fact]
    public void PrimaryInstance_StillUsesTheRealUserProfile()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            // Unset: the everyday case must be byte-for-byte what it always was. This is
            // the fact that stops the dev affordance from leaking into normal use.
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, null);
            Assert.Equal(InstanceProfile.DefaultRoot, InstanceProfile.DataRoot);
            Assert.Null(InstanceProfile.WebViewDataFolder);

            // Blank and whitespace are "no instance", not an instance called "".
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "   ");
            Assert.Equal(InstanceProfile.DefaultRoot, InstanceProfile.DataRoot);
            Assert.Null(InstanceProfile.WebViewDataFolder);
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    [Fact]
    public void EachInstance_GetsItsOwnWebViewDataFolder()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "a");
            var a = InstanceProfile.WebViewDataFolder;
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "b");
            var b = InstanceProfile.WebViewDataFolder;

            // Chromium locks this folder exclusively — a shared value means the second
            // instance fails to launch, so it is not a nice-to-have.
            Assert.NotNull(a);
            Assert.NotNull(b);
            Assert.NotEqual(a, b);
            Assert.Contains("a", a!);
            Assert.Contains("b", b!);
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    [Fact]
    public void AMaliciousOrMistypedId_CannotEscapeTheProfileFolder()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            foreach (var hostile in new[]
                     {
                         "..\\..\\Windows", "..", "a/b", "a\\b", "C:evil", "with space", "a;b", "*",
                     })
            {
                Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, hostile);
                // A rejected id degrades to the primary profile — it never builds a path
                // outside %APPDATA%\ytLlive, and never throws.
                Assert.Equal(InstanceProfile.DefaultRoot, InstanceProfile.DataRoot);
                Assert.Null(InstanceProfile.WebViewDataFolder);
            }
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    [Fact]
    public void ALegitimateId_AllowsLettersDigitsDashAndUnderscore()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "live_2-b");
            Assert.Equal("live_2-b", InstanceProfile.Id);
            Assert.NotEqual(InstanceProfile.DefaultRoot, InstanceProfile.DataRoot);
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    // ---------- the app's real outputs actually move with the profile ----------

    [Fact]
    public void TheRealOutputPaths_FollowTheInstanceProfile()
    {
        var previous = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "7");

            // These are the exact expressions the app uses at startup. If any of them
            // stops consulting InstanceProfile, two dev instances start clobbering
            // each other again and nothing else in the suite would notice.
            var layout = Path.Combine(InstanceProfile.DataRoot, "ytLlive.db");
            var auth = TokenStore.DefaultPath;
            Assert.Equal(Path.Combine(InstanceProfile.DataRoot, "ytLlive.auth"), auth);
            Assert.Contains("instances", layout);
            Assert.Contains("instances", auth);
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, previous);
        }
    }

    // ---------- the 1.0 gate ----------

    [Fact]
    public void InstanceProfile_ExposesNoThirdPathForACallerToDiscover()
    {
        // Every member exists in every configuration — the call sites are unconditional,
        // so Release cannot drift by forgetting an #if — and there are only these three.
        var properties = typeof(InstanceProfile)
            .GetProperties(BindingFlags.Public | BindingFlags.Static | BindingFlags.DeclaredOnly)
            .Select(p => p.Name)
            .OrderBy(n => n, StringComparer.Ordinal)
            .ToArray();
        // The dev surface (Id) exists only in a DEBUG build, by design; the three
        // production members exist in both, which is what keeps the call sites
        // unconditional. Pin both shapes so neither can change unnoticed.
#if DEBUG
        Assert.Equal(new[] { "DataRoot", "DefaultRoot", "Id", "WebViewDataFolder" }, properties);
#else
        Assert.Equal(new[] { "DataRoot", "DefaultRoot", "WebViewDataFolder" }, properties);
#endif

        // The primary instance must not perturb the everyday Chromium profile.
        Assert.Null(typeof(InstanceProfile)
            .GetProperty("WebViewDataFolder")!.GetValue(null));
    }

    [Fact]
    public void TheAlternateProfile_IsConfinedToTheDebugBuild()
    {
        // The 1.0 promise is structural, so this asserts the structure: the alternate
        // profile must live inside #if DEBUG and the #else arm must be the real user
        // profile and nothing else. If someone ever hoists the implementation out of the
        // DEBUG arm — or adds a second one — this fails, which is the point.
        //
        // Verified against the real Release binary too (2026-09-26): a Release build has
        // no InstanceVariable field in metadata and no "instances" path segment, while
        // DataRoot / WebViewDataFolder are present in both configurations. Note a
        // const like YTLIVE_INSTANCE is INLINED at compile time and therefore never
        // appears in either binary — grepping for the variable name proves nothing.
        var source = File.ReadAllText(RepoFile("Helpers", "InstanceProfile.cs"));

        // The whole promise is that a Release build compiles to the #else arm, so assert
        // that arm IS production: the one real user profile, no alternate folder, and no
        // environment variable. If the implementation is ever hoisted out of #if DEBUG,
        // this fails — which is the entire point of having it.
        var elseAt = source.IndexOf("#else", StringComparison.Ordinal);
        var endifAt = source.IndexOf("#endif", StringComparison.Ordinal);
        Assert.True(elseAt > 0 && endifAt > elseAt,
            "InstanceProfile.cs has no #else/#endif arm — the Release behaviour is no longer explicit");

        var releaseArm = source.Substring(elseAt, endifAt - elseAt);
        Assert.Contains("DefaultRoot", releaseArm);
        Assert.DoesNotContain("instances", releaseArm);
        Assert.DoesNotContain("Environment", releaseArm);
        Assert.DoesNotContain("Sanitize", releaseArm);

        // And the development behaviour really is in the DEBUG arm above it.
        var debugArm = source.Substring(0, elseAt);
        Assert.Contains("#if DEBUG", debugArm);
        Assert.Contains("instances", debugArm);
    }

    private static string RepoFile(params string[] parts)
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir != null)
        {
            var candidate = Path.Combine(new[] { dir.FullName }.Concat(parts).ToArray());
            if (File.Exists(candidate)) return candidate;
            dir = dir.Parent;
        }
        throw new FileNotFoundException(
            $"could not locate {Path.Combine(parts)} above {AppContext.BaseDirectory}");
    }
}