using System.Text;
using Akka.Actor;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;

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

/// <summary>
/// Script file access (design 2026-09-28): the host-side guard behind the <c>Files</c> global —
/// off by default, allow-listed roots with a directory-boundary match, no traversal, no links,
/// a size cap — plus the script-facing accessor and a real compile-and-run through
/// <see cref="ScriptCompilationService"/> (so the trust validator is proven to accept it).
/// </summary>
public sealed class ScriptFileReaderTests : IDisposable
{
    private readonly string _base;
    private readonly string _root;

    public ScriptFileReaderTests()
    {
        _base = Path.Combine(Path.GetTempPath(), "sb-files-" + Guid.NewGuid().ToString("N"));
        _root = Path.Combine(_base, "recipes");
        Directory.CreateDirectory(_root);
    }

    public void Dispose()
    {
        try { Directory.Delete(_base, recursive: true); } catch { /* best effort */ }
    }

    private static IOptionsMonitor<SiteRuntimeOptions> Monitor(ScriptFileAccessOptions files) =>
        new StaticMonitor(new SiteRuntimeOptions { ScriptFileAccess = files });

    private ScriptFileReader Reader(long maxBytes = 1024 * 1024, params string[] roots) =>
        new(Monitor(new ScriptFileAccessOptions
        {
            AllowedRoots = roots.Length == 0 ? [_root] : roots.ToList(),
            MaxFileBytes = maxBytes,
        }), NullLogger<ScriptFileReader>.Instance);

    private string Write(string relative, string content)
    {
        var path = Path.Combine(_root, relative);
        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
        File.WriteAllText(path, content);
        return path;
    }

    private static async Task<ScriptFileAccessFailure> FailureOf(Func<Task> act) =>
        (await Assert.ThrowsAsync<ScriptFileAccessException>(act)).Failure;

    [Fact]
    public async Task NoRoots_IsDisabled_ByDefault()
    {
        var reader = new ScriptFileReader(Monitor(new ScriptFileAccessOptions()), NullLogger<ScriptFileReader>.Instance);
        var path = Write("a.txt", "x");

        Assert.Equal(ScriptFileAccessFailure.Disabled, await FailureOf(() => reader.ReadTextAsync(path, default)));
        Assert.Equal(ScriptFileAccessFailure.Disabled, await FailureOf(() => reader.ExistsAsync(path, default)));
    }

    [Fact]
    public async Task ReadsText_UnderRoot_AndDetectsBom()
    {
        var path = Path.Combine(_root, "bom.txt");
        File.WriteAllText(path, "ReactorTempSP,1050\n", new UTF8Encoding(encoderShouldEmitUTF8Identifier: true));

        var text = await Reader().ReadTextAsync(path, default);

        Assert.Equal("ReactorTempSP,1050\n", text);
    }

    [Fact]
    public async Task ReadsFromNestedDirectory()
    {
        var path = Write(Path.Combine("wo", "1001", "r.txt"), "a,1");
        Assert.Equal("a,1", await Reader().ReadTextAsync(path, default));
    }

    [Theory]
    [InlineData("")]
    [InlineData("   ")]
    [InlineData("relative/r.txt")]
    public async Task RejectsEmptyOrRelative(string path)
    {
        Assert.Equal(ScriptFileAccessFailure.InvalidPath, await FailureOf(() => Reader().ReadTextAsync(path, default)));
    }

    [Fact]
    public async Task RejectsPathOutsideRoot()
    {
        var outside = Path.Combine(_base, "secret.txt");
        File.WriteAllText(outside, "nope");

        Assert.Equal(ScriptFileAccessFailure.OutsideAllowedRoots,
            await FailureOf(() => Reader().ReadTextAsync(outside, default)));
    }

    [Fact]
    public async Task RejectsDotDotTraversalOutOfRoot()
    {
        File.WriteAllText(Path.Combine(_base, "secret.txt"), "nope");
        var sneaky = _root + Path.DirectorySeparatorChar + ".." + Path.DirectorySeparatorChar + "secret.txt";

        Assert.Equal(ScriptFileAccessFailure.OutsideAllowedRoots,
            await FailureOf(() => Reader().ReadTextAsync(sneaky, default)));
    }

    [Fact]
    public async Task SiblingDirectorySharingThePrefix_IsNotInsideTheRoot()
    {
        // Root ".../recipes" must not admit ".../recipes2/x" — a directory-boundary match, not a string prefix.
        var sibling = Path.Combine(_base, "recipes2");
        Directory.CreateDirectory(sibling);
        var path = Path.Combine(sibling, "x.txt");
        File.WriteAllText(path, "nope");

        Assert.Equal(ScriptFileAccessFailure.OutsideAllowedRoots,
            await FailureOf(() => Reader().ReadTextAsync(path, default)));
    }

    [Fact]
    public async Task TheRootItself_IsNotAFile()
    {
        Assert.Equal(ScriptFileAccessFailure.OutsideAllowedRoots,
            await FailureOf(() => Reader().ReadTextAsync(_root, default)));
    }

    [Fact]
    public async Task SymlinkedFileInsideRoot_IsRefused()
    {
        var outside = Path.Combine(_base, "secret.txt");
        File.WriteAllText(outside, "nope");
        var link = Path.Combine(_root, "link.txt");
        File.CreateSymbolicLink(link, outside);

        Assert.Equal(ScriptFileAccessFailure.LinkNotAllowed,
            await FailureOf(() => Reader().ReadTextAsync(link, default)));
    }

    [Fact]
    public async Task SymlinkedDirectoryInsideRoot_IsRefused()
    {
        var outsideDir = Path.Combine(_base, "elsewhere");
        Directory.CreateDirectory(outsideDir);
        File.WriteAllText(Path.Combine(outsideDir, "secret.txt"), "nope");
        Directory.CreateSymbolicLink(Path.Combine(_root, "linked"), outsideDir);

        Assert.Equal(ScriptFileAccessFailure.LinkNotAllowed,
            await FailureOf(() => Reader().ReadTextAsync(Path.Combine(_root, "linked", "secret.txt"), default)));
    }

    [Fact]
    public async Task MissingFile_IsNotFound_AndExistsIsFalse()
    {
        var path = Path.Combine(_root, "missing.txt");

        Assert.Equal(ScriptFileAccessFailure.NotFound, await FailureOf(() => Reader().ReadTextAsync(path, default)));
        Assert.False(await Reader().ExistsAsync(path, default));
    }

    [Fact]
    public async Task Exists_TrueForFile_ButStillEnforcesRoots()
    {
        var path = Write("r.txt", "x");
        Assert.True(await Reader().ExistsAsync(path, default));
        Assert.Equal(ScriptFileAccessFailure.OutsideAllowedRoots,
            await FailureOf(() => Reader().ExistsAsync(Path.Combine(_base, "whatever.txt"), default)));
    }

    [Fact]
    public async Task FileOverTheCap_IsTooLarge()
    {
        var path = Write("big.txt", new string('x', 2048));

        Assert.Equal(ScriptFileAccessFailure.TooLarge, await FailureOf(() => Reader(maxBytes: 1024).ReadTextAsync(path, default)));
        Assert.Equal(2048, (await Reader(maxBytes: 2048).ReadTextAsync(path, default)).Length);
    }

    [Fact]
    public async Task SecondRoot_IsHonoured()
    {
        var other = Path.Combine(_base, "other");
        Directory.CreateDirectory(other);
        var path = Path.Combine(other, "o.txt");
        File.WriteAllText(path, "ok");

        Assert.Equal("ok", await Reader(1024 * 1024, _root, other).ReadTextAsync(path, default));
    }

    [Fact]
    public async Task RootConfiguredWithTrailingSeparator_Works()
    {
        var path = Write("t.txt", "ok");
        Assert.Equal("ok", await Reader(1024 * 1024, _root + Path.DirectorySeparatorChar).ReadTextAsync(path, default));
    }

    [Fact]
    public void SplitLines_HandlesMixedEndings_AndDropsTrailingEmptyLine()
    {
        Assert.Equal(["a", "b", "c", "", "d"], FilesAccessor.SplitLines("a\r\nb\nc\r\rd\n"));
        Assert.Empty(FilesAccessor.SplitLines(""));
        Assert.Equal([""], FilesAccessor.SplitLines("\n"));
    }

    [Fact]
    public async Task Accessor_WithoutReader_ThrowsDisabled()
    {
        var files = new FilesAccessor(reader: null, CancellationToken.None);
        Assert.Equal(ScriptFileAccessFailure.Disabled, await FailureOf(() => files.ReadTextAsync("C:/x.txt")));
    }

    [Fact]
    public async Task Accessor_HonoursTheScriptDeadline()
    {
        var path = Write("r.txt", "x");
        using var expired = new CancellationTokenSource();
        await expired.CancelAsync();
        var files = new FilesAccessor(Reader(), expired.Token);

        await Assert.ThrowsAnyAsync<OperationCanceledException>(() => files.ReadTextAsync(path));
    }

    [Fact]
    public async Task RealScript_CompilesThroughTheTrustGate_AndParsesARecipe()
    {
        // End-to-end at the script boundary: the runtime compiler (trust validator included)
        // accepts a script that uses Files + catches ScriptFileAccessException by name, and the
        // compiled script reads + parses a recipe through the real ScriptRuntimeContext wiring.
        var path = Write("recipe.txt", "# comment\nReactorTempSP,1050\nCoatingType,Aluminide\n\nTargetRuntime,480\n");
        const string code = """
            var path = (string)Parameters["Path"];
            try {
                var values = new System.Collections.Generic.Dictionary<string, string>();
                foreach (var line in await Files.ReadLinesAsync(path)) {
                    if (line.Trim().Length == 0 || line.TrimStart().StartsWith("#")) continue;
                    var i = line.IndexOf(',');
                    values[line.Substring(0, i).Trim()] = line.Substring(i + 1).Trim();
                }
                var exists = await Instance.Files.ExistsAsync(path);
                return values.Count + "|" + values["CoatingType"] + "|" + exists;
            } catch (ScriptFileAccessException ex) when (ex.Failure == ScriptFileAccessFailure.NotFound) {
                return "missing";
            }
            """;
        var compiled = new ScriptCompilationService(NullLogger<ScriptCompilationService>.Instance).Compile("RecipeParse", code);
        Assert.True(compiled.IsSuccess, string.Join("; ", compiled.Errors));

        var ctx = new ScriptRuntimeContext(
            ActorRefs.Nobody, sharedScriptLibrary: null!, currentCallDepth: 0, maxCallDepth: 10,
            askTimeout: TimeSpan.FromSeconds(5), instanceName: "SBTEST01",
            logger: NullLogger<ScriptRuntimeContext>.Instance, fileReader: Reader());
        var run = async (string p) => (await compiled.CompiledScript!.RunAsync(new ScriptGlobals
        {
            Instance = ctx,
            Parameters = new ScriptParameters(new Dictionary<string, object?> { ["Path"] = p }),
        })).ReturnValue;

        Assert.Equal("3|Aluminide|True", await run(path));
        Assert.Equal("missing", await run(Path.Combine(_root, "nope.txt")));
    }

    [Fact]
    public void RawSystemIo_IsStillRejectedByTheTrustGate()
    {
        // The Files global is the ONLY sanctioned door — System.IO stays forbidden.
        var compiled = new ScriptCompilationService(NullLogger<ScriptCompilationService>.Instance)
            .Compile("Raw", "return System.IO.File.ReadAllText(\"C:/x.txt\");");
        Assert.False(compiled.IsSuccess);
    }

    private sealed class StaticMonitor(SiteRuntimeOptions value) : IOptionsMonitor<SiteRuntimeOptions>
    {
        public SiteRuntimeOptions CurrentValue => value;
        public SiteRuntimeOptions Get(string? name) => value;
        public IDisposable? OnChange(Action<SiteRuntimeOptions, string?> listener) => null;
    }
}