namespace MxGateway.Server.Security.Authentication;

public static class ApiKeyAdminCommandLineParser
{
    public static ApiKeyAdminParseResult Parse(IReadOnlyList<string> args)
    {
        if (args.Count == 0 || !string.Equals(args[0], "apikey", StringComparison.OrdinalIgnoreCase))
        {
            return ApiKeyAdminParseResult.NotApiKeyCommand();
        }

        if (args.Count < 2)
        {
            return ApiKeyAdminParseResult.Fail("Missing apikey subcommand.");
        }

        if (!TryParseKind(args[1], out ApiKeyAdminCommandKind kind))
        {
            return ApiKeyAdminParseResult.Fail($"Unknown apikey subcommand '{args[1]}'.");
        }

        Dictionary<string, string?> options = new(StringComparer.OrdinalIgnoreCase);
        bool json = false;

        for (int index = 2; index < args.Count; index++)
        {
            string arg = args[index];
            if (string.Equals(arg, "--json", StringComparison.OrdinalIgnoreCase))
            {
                json = true;
                continue;
            }

            if (!arg.StartsWith("--", StringComparison.Ordinal))
            {
                return ApiKeyAdminParseResult.Fail($"Unexpected argument '{arg}'.");
            }

            string name = arg[2..];
            string? value;

            int equalsIndex = name.IndexOf('=', StringComparison.Ordinal);
            if (equalsIndex >= 0)
            {
                value = name[(equalsIndex + 1)..];
                name = name[..equalsIndex];
            }
            else
            {
                if (index + 1 >= args.Count || args[index + 1].StartsWith("--", StringComparison.Ordinal))
                {
                    return ApiKeyAdminParseResult.Fail($"Option '--{name}' requires a value.");
                }

                value = args[++index];
            }

            options[name] = value;
        }

        string? keyId = GetOption(options, "key-id");
        string? displayName = GetOption(options, "display-name");
        IReadOnlySet<string> scopes = ParseScopes(GetOption(options, "scopes"));

        string? validationError = Validate(kind, keyId, displayName);
        if (validationError is not null)
        {
            return ApiKeyAdminParseResult.Fail(validationError);
        }

        return ApiKeyAdminParseResult.Success(new ApiKeyAdminCommand(
            Kind: kind,
            Json: json,
            SqlitePath: GetOption(options, "sqlite-path"),
            Pepper: GetOption(options, "pepper"),
            KeyId: keyId,
            DisplayName: displayName,
            Scopes: scopes));
    }

    private static bool TryParseKind(string value, out ApiKeyAdminCommandKind kind)
    {
        switch (value.ToLowerInvariant())
        {
            case "init-db":
                kind = ApiKeyAdminCommandKind.InitDb;
                return true;
            case "create-key":
                kind = ApiKeyAdminCommandKind.CreateKey;
                return true;
            case "list-keys":
                kind = ApiKeyAdminCommandKind.ListKeys;
                return true;
            case "revoke-key":
                kind = ApiKeyAdminCommandKind.RevokeKey;
                return true;
            case "rotate-key":
                kind = ApiKeyAdminCommandKind.RotateKey;
                return true;
            default:
                kind = default;
                return false;
        }
    }

    private static string? Validate(ApiKeyAdminCommandKind kind, string? keyId, string? displayName)
    {
        if (kind is ApiKeyAdminCommandKind.CreateKey or ApiKeyAdminCommandKind.RevokeKey or ApiKeyAdminCommandKind.RotateKey
            && string.IsNullOrWhiteSpace(keyId))
        {
            return $"Subcommand '{KindName(kind)}' requires --key-id.";
        }

        if (!string.IsNullOrWhiteSpace(keyId) && !IsValidKeyId(keyId))
        {
            return "API key id may contain only letters, numbers, periods, and hyphens.";
        }

        if (kind == ApiKeyAdminCommandKind.CreateKey && string.IsNullOrWhiteSpace(displayName))
        {
            return "Subcommand 'create-key' requires --display-name.";
        }

        return null;
    }

    private static string KindName(ApiKeyAdminCommandKind kind)
    {
        return kind switch
        {
            ApiKeyAdminCommandKind.InitDb => "init-db",
            ApiKeyAdminCommandKind.CreateKey => "create-key",
            ApiKeyAdminCommandKind.ListKeys => "list-keys",
            ApiKeyAdminCommandKind.RevokeKey => "revoke-key",
            ApiKeyAdminCommandKind.RotateKey => "rotate-key",
            _ => kind.ToString()
        };
    }

    private static bool IsValidKeyId(string keyId)
    {
        return keyId.All(character =>
            char.IsAsciiLetterOrDigit(character)
            || character is '.' or '-');
    }

    private static string? GetOption(Dictionary<string, string?> options, string name)
    {
        return options.TryGetValue(name, out string? value) ? value : null;
    }

    private static IReadOnlySet<string> ParseScopes(string? scopes)
    {
        return new HashSet<string>(
            (scopes ?? string.Empty)
                .Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries),
            StringComparer.Ordinal);
    }
}