using Json.Schema;
using System.Security.Cryptography;
using System.Text.Json;
using System.Text.RegularExpressions;

namespace Zcbot.WindowsNode;

internal static class AdapterContractLoader
{
    internal static AdapterDescriptor Load(string directory)
    {
        var root = Path.GetFullPath(directory);
        var manifestPath = ResolveFile(root, "adapter.json");
        using var manifestDocument = JsonDocument.Parse(File.ReadAllBytes(manifestPath));
        var manifestRoot = manifestDocument.RootElement;
        RequireOnlyProperties(
            manifestRoot, "capability", "adapter_version", "runtime", "runtime_id",
            "entrypoint", "contract", "worker_timeout_minutes", "running_detail");
        var manifest = new AdapterManifest(
            RequiredString(manifestRoot, "capability"),
            RequiredVersion(manifestRoot, "adapter_version"),
            RequiredString(manifestRoot, "runtime"),
            OptionalString(manifestRoot, "runtime_id"),
            RequiredString(manifestRoot, "entrypoint"),
            RequiredString(manifestRoot, "contract"),
            OptionalInteger(manifestRoot, "worker_timeout_minutes", 30, 1, 1440),
            RequiredString(manifestRoot, "running_detail"));
        ValidateManifest(manifest);

        var contractPath = ResolveFile(root, manifest.Contract);
        var contractBytes = File.ReadAllBytes(contractPath);
        var contractSha256 = Convert.ToHexString(SHA256.HashData(contractBytes)).ToLowerInvariant();
        using var contractDocument = JsonDocument.Parse(contractBytes);
        var contractRoot = contractDocument.RootElement;
        var capability = RequiredString(contractRoot, "capability");
        if (!capability.Equals(manifest.Capability, StringComparison.Ordinal))
        {
            throw new InvalidDataException("Adapter manifest capability does not match its contract.");
        }
        var currentVersion = ParseVersion(manifest.AdapterVersion);
        var features = contractRoot.GetProperty("features").EnumerateObject()
            .Where(item => ParseVersion(item.Value.GetString() ?? "0.0.0") <= currentVersion)
            .Select(item => item.Name)
            .ToArray();
        var (workspaceStateFilename, previewOutputIds) = ReadWorkspace(contractRoot);
        var schema = JsonSchema.Build(contractRoot.GetProperty("request_schema").Clone());
        var entrypointPath = ResolveFile(root, manifest.Entrypoint);
        ValidateEntrypoint(manifest, entrypointPath);
        return new AdapterDescriptor(
            root,
            entrypointPath,
            contractPath,
            contractSha256,
            manifest,
            new NodeAdapterContract(
                capability,
                RequiredString(contractRoot, "display_name"),
                features,
                schema,
                workspaceStateFilename,
                previewOutputIds));
    }

    private static void ValidateManifest(AdapterManifest manifest)
    {
        if (!Regex.IsMatch(manifest.Capability, "^[a-z][a-z0-9_.-]+@v[1-9][0-9]*$"))
        {
            throw new InvalidDataException("Adapter capability is invalid.");
        }
        if (manifest.Runtime is not ("python" or "executable"))
        {
            throw new InvalidDataException("Adapter runtime must be python or executable.");
        }
        if (manifest.Runtime == "python"
            && (manifest.RuntimeId is null
                || !Regex.IsMatch(manifest.RuntimeId, "^[a-z][a-z0-9_-]{0,31}$")))
        {
            throw new InvalidDataException("Python adapter runtime_id is invalid.");
        }
        if (manifest.Runtime == "executable" && manifest.RuntimeId is not null)
        {
            throw new InvalidDataException("Executable adapter must not declare runtime_id.");
        }
    }

    private static (string? StateFilename, IReadOnlyList<string> PreviewOutputIds) ReadWorkspace(
        JsonElement contractRoot)
    {
        if (!contractRoot.TryGetProperty("workspace", out var workspace)
            || workspace.ValueKind != JsonValueKind.Object)
        {
            return (null, []);
        }
        var stateOutput = RequiredString(workspace, "state_output");
        var outputs = contractRoot.GetProperty("outputs");
        if (!outputs.TryGetProperty(stateOutput, out var stateSpec))
        {
            throw new InvalidDataException("Workspace state output is missing from contract.");
        }
        var previewOutputIds = workspace.GetProperty("preview_outputs")
            .EnumerateArray()
            .Select(item => item.GetString()
                ?? throw new InvalidDataException("Workspace preview output is invalid."))
            .ToArray();
        return (RequiredString(stateSpec, "filename"), previewOutputIds);
    }

    private static void ValidateEntrypoint(AdapterManifest manifest, string entrypointPath)
    {
        if ((manifest.Runtime == "python"
                && !Path.GetExtension(entrypointPath).Equals(".py", StringComparison.OrdinalIgnoreCase))
            || (manifest.Runtime == "executable"
                && !Path.GetExtension(entrypointPath).Equals(".exe", StringComparison.OrdinalIgnoreCase)))
        {
            throw new InvalidDataException("Adapter entrypoint extension does not match its runtime.");
        }
    }

    private static string ResolveFile(string root, string relativePath)
    {
        if (string.IsNullOrWhiteSpace(relativePath) || Path.IsPathFullyQualified(relativePath))
        {
            throw new InvalidDataException("Adapter file path must be relative.");
        }
        var resolved = Path.GetFullPath(Path.Combine(root, relativePath));
        if (!resolved.StartsWith(root + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase)
            || !File.Exists(resolved))
        {
            throw new InvalidDataException("Adapter file is missing or outside its directory.");
        }
        return resolved;
    }

    private static void RequireOnlyProperties(JsonElement value, params string[] names)
    {
        if (value.ValueKind != JsonValueKind.Object)
        {
            throw new InvalidDataException("Adapter manifest must be an object.");
        }
        var allowed = names.ToHashSet(StringComparer.Ordinal);
        if (value.EnumerateObject().Any(item => !allowed.Contains(item.Name)))
        {
            throw new InvalidDataException("Adapter manifest contains unknown properties.");
        }
    }

    private static string RequiredString(JsonElement value, string name) =>
        value.TryGetProperty(name, out var property)
        && property.ValueKind == JsonValueKind.String
        && !string.IsNullOrWhiteSpace(property.GetString())
            ? property.GetString()!
            : throw new InvalidDataException($"Adapter property {name} is missing.");

    private static string RequiredVersion(JsonElement value, string name)
    {
        var version = RequiredString(value, name);
        if (!Regex.IsMatch(version, "^[0-9]+\\.[0-9]+\\.[0-9]+$")
            || !Version.TryParse(version, out _))
        {
            throw new InvalidDataException($"Adapter property {name} is not a semantic version.");
        }
        return version;
    }

    private static int OptionalInteger(
        JsonElement value, string name, int defaultValue, int minimum, int maximum)
    {
        if (!value.TryGetProperty(name, out var property)) return defaultValue;
        return property.TryGetInt32(out var result)
            && result >= minimum
            && result <= maximum
                ? result
                : throw new InvalidDataException($"Adapter property {name} is invalid.");
    }

    private static string? OptionalString(JsonElement value, string name) =>
        !value.TryGetProperty(name, out var property) || property.ValueKind == JsonValueKind.Null
            ? null
            : property.ValueKind == JsonValueKind.String
                ? property.GetString()
                : throw new InvalidDataException($"Adapter property {name} must be a string.");

    private static Version ParseVersion(string value) =>
        Version.TryParse(value, out var version) ? version : new Version(0, 0, 0);
}