using System;
using System.Linq;

namespace StellaOps.Notify.WebService.Options;

internal static class NotifyWebServiceOptionsValidator
{
    public static void Validate(NotifyWebServiceOptions options)
    {
        ArgumentNullException.ThrowIfNull(options);

        ValidateStorage(options.Storage);
        ValidateAuthority(options.Authority);
        ValidateApi(options.Api);
    }

    private static void ValidateStorage(NotifyWebServiceOptions.StorageOptions storage)
    {
        ArgumentNullException.ThrowIfNull(storage);

        var driver = storage.Driver ?? string.Empty;
        // Allow 'memory' driver for testing purposes, 'postgres' for production
        var allowedDrivers = new[] { "postgres", "memory" };
        if (!allowedDrivers.Any(d => string.Equals(d, driver, StringComparison.OrdinalIgnoreCase)))
        {
            throw new InvalidOperationException($"Unsupported storage driver '{storage.Driver}'. Supported drivers: {string.Join(", ", allowedDrivers)}.");
        }
    }

    private static void ValidateAuthority(NotifyWebServiceOptions.AuthorityOptions authority)
    {
        ArgumentNullException.ThrowIfNull(authority);

        if (authority.Enabled)
        {
            if (string.IsNullOrWhiteSpace(authority.Issuer))
            {
                throw new InvalidOperationException("notify:authority:issuer must be provided when authority is enabled.");
            }

            if (authority.Audiences is null || authority.Audiences.Count == 0)
            {
                throw new InvalidOperationException("notify:authority:audiences must include at least one value.");
            }

            if (string.IsNullOrWhiteSpace(authority.AdminScope)
                || string.IsNullOrWhiteSpace(authority.OperatorScope)
                || string.IsNullOrWhiteSpace(authority.ViewerScope))
            {
                throw new InvalidOperationException("notify:authority admin, operator, and viewer scopes must be configured.");
            }
        }
        else
        {
            if (string.IsNullOrWhiteSpace(authority.DevelopmentSigningKey) || authority.DevelopmentSigningKey.Length < 32)
            {
                throw new InvalidOperationException("notify:authority:developmentSigningKey must be at least 32 characters when authority is disabled.");
            }
        }
    }

    private static void ValidateApi(NotifyWebServiceOptions.ApiOptions api)
    {
        ArgumentNullException.ThrowIfNull(api);

        if (!api.BasePath.StartsWith("/", StringComparison.Ordinal))
        {
            throw new InvalidOperationException("notify:api:basePath must start with '/'.");
        }

        if (!api.InternalBasePath.StartsWith("/", StringComparison.Ordinal))
        {
            throw new InvalidOperationException("notify:api:internalBasePath must start with '/'.");
        }

        if (string.IsNullOrWhiteSpace(api.TenantHeader))
        {
            throw new InvalidOperationException("notify:api:tenantHeader must be provided.");
        }

        ValidateRateLimits(api.RateLimits);
    }

    private static void ValidateRateLimits(NotifyWebServiceOptions.RateLimitOptions rateLimits)
    {
        ArgumentNullException.ThrowIfNull(rateLimits);

        ValidatePolicy(rateLimits.DeliveryHistory, "notify:api:rateLimits:deliveryHistory");
        ValidatePolicy(rateLimits.TestSend, "notify:api:rateLimits:testSend");

        static void ValidatePolicy(NotifyWebServiceOptions.RateLimitPolicyOptions options, string prefix)
        {
            ArgumentNullException.ThrowIfNull(options);

            if (!options.Enabled)
            {
                return;
            }

            if (options.TokenLimit <= 0)
            {
                throw new InvalidOperationException($"{prefix}:tokenLimit must be positive when enabled.");
            }

            if (options.TokensPerPeriod <= 0)
            {
                throw new InvalidOperationException($"{prefix}:tokensPerPeriod must be positive when enabled.");
            }

            if (options.ReplenishmentPeriodSeconds <= 0)
            {
                throw new InvalidOperationException($"{prefix}:replenishmentPeriodSeconds must be positive when enabled.");
            }

            if (options.QueueLimit < 0)
            {
                throw new InvalidOperationException($"{prefix}:queueLimit cannot be negative.");
            }
        }
    }
}