using System.CommandLine;
using System.CommandLine.Parsing;
using System.Text.Json;
using ScadaLink.Commons.Messages.Management;

namespace ScadaLink.CLI.Commands;

internal static class CommandHelpers
{
    /// <summary>
    /// Resolves the management URL, credentials, and output format, then sends <paramref name="command"/>
    /// to the management API and returns the process exit code.
    /// </summary>
    /// <param name="result">Parsed command-line result from which option values are read.</param>
    /// <param name="urlOption">Option that supplies the management URL override.</param>
    /// <param name="formatOption">Option that supplies the output format override.</param>
    /// <param name="usernameOption">Option that supplies the username override.</param>
    /// <param name="passwordOption">Option that supplies the password override.</param>
    /// <param name="command">The management command object to send.</param>
    /// <param name="timeout">
    /// Optional per-command HTTP timeout. Defaults to 30s, matching the management API's
    /// own request timeout. Larger payloads (e.g. Transport bundles) should supply a
    /// longer value.
    /// </param>
    /// <param name="onSuccess">
    /// Optional success handler. When supplied, the helper invokes it with the success
    /// body instead of running the default <see cref="HandleResponse"/> rendering path —
    /// useful when the caller needs to capture the response (e.g. write a file) rather
    /// than print it. The authorization-failure exit-code contract
    /// (<see cref="IsAuthorizationFailure"/>) is preserved on the error path either way,
    /// closing CLI-017's regression.
    /// </param>
    internal static async Task<int> ExecuteCommandAsync(
        ParseResult result,
        Option<string> urlOption,
        Option<string> formatOption,
        Option<string> usernameOption,
        Option<string> passwordOption,
        object command,
        TimeSpan? timeout = null,
        Func<string, int>? onSuccess = null)
    {
        var config = CliConfig.Load();
        var format = ResolveFormat(result, formatOption, config);

        // Resolve management URL
        var url = result.GetValue(urlOption);
        if (string.IsNullOrWhiteSpace(url))
            url = config.ManagementUrl;

        if (string.IsNullOrWhiteSpace(url))
        {
            OutputFormatter.WriteError(
                "No management URL specified. Use --url, set SCADALINK_MANAGEMENT_URL, or add 'managementUrl' to ~/.scadalink/config.json.",
                "NO_URL");
            return 1;
        }

        if (!IsValidManagementUrl(url))
        {
            OutputFormatter.WriteError(
                $"Invalid management URL '{url}'. Expected an absolute http/https URL (e.g. http://localhost:9001).",
                "INVALID_URL");
            return 1;
        }

        // Resolve credentials: command-line options take precedence, then the
        // SCADALINK_USERNAME / SCADALINK_PASSWORD environment variables.
        var username = ResolveCredential(result.GetValue(usernameOption), config.Username);
        var password = ResolveCredential(result.GetValue(passwordOption), config.Password);

        if (string.IsNullOrWhiteSpace(username) || string.IsNullOrWhiteSpace(password))
        {
            OutputFormatter.WriteError(
                "Credentials required. Use --username/--password or set SCADALINK_USERNAME/SCADALINK_PASSWORD.",
                "NO_CREDENTIALS");
            return 1;
        }

        // Derive command name from type
        var commandName = ManagementCommandRegistry.GetCommandName(command.GetType());

        // Send via HTTP
        using var client = new ManagementHttpClient(url, username, password);
        var response = await client.SendCommandAsync(commandName, command, timeout ?? TimeSpan.FromSeconds(30));

        // Caller-supplied success handler short-circuits the default rendering — but
        // the error path still routes through IsAuthorizationFailure so the documented
        // exit-2 contract holds whether or not a custom handler is provided
        // (CLI-017 unification of the bundle path).
        if (onSuccess is not null)
        {
            if (response.JsonData is not null)
                return onSuccess(response.JsonData);

            OutputFormatter.WriteError(response.Error ?? "Unknown error", response.ErrorCode ?? "ERROR");
            return IsAuthorizationFailure(response) ? 2 : 1;
        }

        return HandleResponse(response, format);
    }

    /// <summary>
    /// Resolves the output format using the documented precedence chain:
    /// an explicitly supplied <c>--format</c> option wins, otherwise the
    /// config-file / environment-variable default (<see cref="CliConfig.DefaultFormat"/>)
    /// is used, otherwise <c>json</c>. The <c>--format</c> option must not declare a
    /// <c>DefaultValueFactory</c> — that would mask whether the flag was supplied.
    /// </summary>
    /// <param name="result">Parsed command-line result.</param>
    /// <param name="formatOption">The <c>--format</c> option definition.</param>
    /// <param name="config">Loaded CLI configuration providing the default format fallback.</param>
    internal static string ResolveFormat(ParseResult result, Option<string> formatOption, CliConfig config)
    {
        // GetResult returns non-null only when the option was actually present on the
        // command line, letting an explicit --format override the config default.
        if (result.GetResult(formatOption) != null)
        {
            var explicitValue = result.GetValue(formatOption);
            if (!string.IsNullOrWhiteSpace(explicitValue))
                return explicitValue;
        }

        return string.IsNullOrWhiteSpace(config.DefaultFormat) ? "json" : config.DefaultFormat;
    }

    /// <summary>
    /// Resolves a single credential: an explicit command-line value wins, otherwise the
    /// environment-variable fallback (from <see cref="CliConfig"/>) is used.
    /// </summary>
    /// <param name="commandLineValue">Value supplied on the command line, or null if absent.</param>
    /// <param name="envValue">Fallback value from the config file or environment variable.</param>
    internal static string? ResolveCredential(string? commandLineValue, string? envValue)
        => string.IsNullOrWhiteSpace(commandLineValue) ? envValue : commandLineValue;

    /// <summary>
    /// Validates that a management URL is an absolute http/https URL. A malformed URL
    /// (missing scheme, empty, or a non-http scheme) would otherwise reach
    /// <c>new Uri(...)</c> in the <see cref="ManagementHttpClient"/> constructor and throw
    /// an unhandled <see cref="UriFormatException"/>.
    /// </summary>
    /// <param name="url">URL string to validate.</param>
    internal static bool IsValidManagementUrl(string? url)
    {
        if (string.IsNullOrWhiteSpace(url))
            return false;

        return Uri.TryCreate(url, UriKind.Absolute, out var uri)
            && (uri.Scheme == Uri.UriSchemeHttp || uri.Scheme == Uri.UriSchemeHttps);
    }

    /// <summary>
    /// Writes the management response to stdout and returns the appropriate process exit code.
    /// </summary>
    /// <param name="response">Response received from the management API.</param>
    /// <param name="format">Output format (<c>json</c> or <c>table</c>).</param>
    internal static int HandleResponse(ManagementResponse response, string format)
    {
        if (response.JsonData != null)
        {
            // A success status with an empty/whitespace body (e.g. a 204 from a delete)
            // is a "command succeeded, no output" case — do not attempt to parse it.
            if (string.IsNullOrWhiteSpace(response.JsonData))
            {
                Console.WriteLine("(ok)");
                return 0;
            }

            if (string.Equals(format, "table", StringComparison.OrdinalIgnoreCase))
            {
                WriteAsTable(response.JsonData);
            }
            else
            {
                Console.WriteLine(response.JsonData);
            }
            return 0;
        }

        var errorCode = response.ErrorCode ?? "ERROR";
        var error = response.Error ?? "Unknown error";

        OutputFormatter.WriteError(error, errorCode);
        return IsAuthorizationFailure(response) ? 2 : 1;
    }

    /// <summary>
    /// Determines whether an error response represents an authorization failure
    /// (insufficient role), which the documented exit-code table maps to exit code 2.
    /// An HTTP 403 status is the primary signal; the server may also signal it via an
    /// <c>UNAUTHORIZED</c> / <c>FORBIDDEN</c> error code on a different HTTP status, so
    /// both channels are honoured. (Authentication failure — HTTP 401 / bad credentials
    /// — is deliberately <em>not</em> treated as authorization failure; it is exit 1.)
    /// </summary>
    internal static bool IsAuthorizationFailure(ManagementResponse response)
    {
        if (response.StatusCode == 403)
            return true;

        return string.Equals(response.ErrorCode, "FORBIDDEN", StringComparison.OrdinalIgnoreCase)
            || string.Equals(response.ErrorCode, "UNAUTHORIZED", StringComparison.OrdinalIgnoreCase);
    }

    private static void WriteAsTable(string json)
    {
        JsonDocument doc;
        try
        {
            doc = JsonDocument.Parse(json);
        }
        catch (JsonException)
        {
            // The server returned a success status but a non-JSON body (e.g. a proxy
            // HTML error page, or a plain-text message). Print it verbatim rather than
            // crashing — mirrors the raw-body fallback on the JSON path.
            Console.WriteLine(json);
            return;
        }

        using (doc)
        {
            var root = doc.RootElement;

            if (root.ValueKind == JsonValueKind.Array)
            {
                var items = root.EnumerateArray().ToList();
                if (items.Count == 0)
                {
                    Console.WriteLine("(no results)");
                    return;
                }

                // Derive the header set as the union of property names across *every*
                // element, in first-seen order. Using only items[0] would silently drop
                // columns for any later element with a different shape (CLI-016).
                var objectItems = items.Where(i => i.ValueKind == JsonValueKind.Object).ToList();
                string[] headers;
                if (objectItems.Count > 0)
                {
                    var seen = new List<string>();
                    var known = new HashSet<string>(StringComparer.Ordinal);
                    foreach (var item in objectItems)
                        foreach (var prop in item.EnumerateObject())
                            if (known.Add(prop.Name))
                                seen.Add(prop.Name);
                    headers = seen.ToArray();
                }
                else
                {
                    headers = new[] { "Value" };
                }

                var rows = items.Select(item =>
                {
                    if (item.ValueKind == JsonValueKind.Object)
                    {
                        return headers.Select(h =>
                            item.TryGetProperty(h, out var val)
                                ? val.ValueKind == JsonValueKind.Null ? "" : val.ToString()
                                : "").ToArray();
                    }
                    return new[] { item.ToString() };
                });

                OutputFormatter.WriteTable(rows, headers);
            }
            else if (root.ValueKind == JsonValueKind.Object)
            {
                var headers = new[] { "Property", "Value" };
                var rows = root.EnumerateObject().Select(p =>
                    new[] { p.Name, p.Value.ValueKind == JsonValueKind.Null ? "" : p.Value.ToString() });
                OutputFormatter.WriteTable(rows, headers);
            }
            else
            {
                Console.WriteLine(root.ToString());
            }
        }
    }
}