using FinalFactory.Rendezvous.Contracts;

namespace FinalFactory.Rendezvous.Server.Provisioning;

internal sealed class GamePolicyRegistry
{
    private readonly Dictionary<(GameId Game, EnvironmentId Environment), GamePolicy> _policies;

    private GamePolicyRegistry(
        Dictionary<(GameId Game, EnvironmentId Environment), GamePolicy> policies) =>
        _policies = policies;

    public bool HasEnabledPolicies => _policies.Values.Any(static policy => policy.Enabled);
    public IEnumerable<GamePolicy> EnabledPolicies =>
        _policies.Values.Where(static policy => policy.Enabled);

    public static GamePolicyRegistry Create(IEnumerable<GamePolicyOptions> options)
    {
        GamePolicyOptions[] configuredPolicies = options.ToArray();
        if (configuredPolicies.Length > ProvisioningLimits.MaxGamePolicies)
        {
            throw new ProvisioningConfigurationException(
                $"At most {ProvisioningLimits.MaxGamePolicies} game policies may be configured.");
        }

        Dictionary<(GameId Game, EnvironmentId Environment), GamePolicy> policies = [];
        foreach (GamePolicyOptions policyOptions in configuredPolicies)
        {
            Validate(policyOptions);
            GamePolicy policy = new(policyOptions);
            if (!policies.TryAdd((policy.GameId, policy.EnvironmentId), policy))
            {
                throw new ProvisioningConfigurationException(
                    $"Duplicate game/environment policy: {policy.GameId}/{policy.EnvironmentId}.");
            }
        }

        return new GamePolicyRegistry(policies);
    }

    public bool TryGet(
        GameId gameId,
        EnvironmentId environmentId,
        out GamePolicy? policy)
    {
        if (_policies.TryGetValue((gameId, environmentId), out GamePolicy? candidate)
            && candidate.Enabled)
        {
            policy = candidate;
            return true;
        }

        policy = null;
        return false;
    }

    private static void Validate(GamePolicyOptions options)
    {
        if (!GameId.TryParse(options.GameId, out _)
            || !EnvironmentId.TryParse(options.EnvironmentId, out _))
        {
            throw new ProvisioningConfigurationException(
                "Game policies require valid game and environment IDs.");
        }

        if (options.ProtocolVersions.Count is 0 or > ProvisioningLimits.MaxProtocolVersionsPerPolicy
            || options.ProtocolVersions.Contains(0)
            || options.ProtocolVersions.Count != options.ProtocolVersions.Distinct().Count())
        {
            throw new ProvisioningConfigurationException(
                $"Policy {options.GameId}/{options.EnvironmentId} requires unique non-zero protocol versions.");
        }

        if (options.Regions.Count is 0 or > ProvisioningLimits.MaxRegionsPerPolicy
            || options.Regions.Any(static region => !RegionId.TryParse(region, out _))
            || options.Regions.Count != options.Regions.Distinct(StringComparer.Ordinal).Count())
        {
            throw new ProvisioningConfigurationException(
                $"Policy {options.GameId}/{options.EnvironmentId} requires unique valid regions.");
        }

        if (options.VisibilityModes.Count == 0
            || options.VisibilityModes.Any(static mode => !Enum.IsDefined(mode))
            || options.VisibilityModes.Count != options.VisibilityModes.Distinct().Count()
            || options.PublisherTrustModes.Count == 0
            || options.PublisherTrustModes.Any(static mode => !Enum.IsDefined(mode))
            || options.PublisherTrustModes.Count != options.PublisherTrustModes.Distinct().Count())
        {
            throw new ProvisioningConfigurationException(
                $"Policy {options.GameId}/{options.EnvironmentId} requires valid visibility and trust modes.");
        }

        if (options.MetadataMaxBytes is < 2 or > ContractLimits.MetadataMaxBytes
            || options.MetadataMaxKeys is < 0 or > ContractLimits.MetadataMaxKeys
            || options.MetadataValueMaxBytes.Count > options.MetadataMaxKeys
            || options.MetadataValueMaxBytes.Any(static item =>
                string.IsNullOrWhiteSpace(item.Key)
                || !ContractValidation.IsUtf8LengthWithin(item.Key, ContractLimits.MetadataKeyMaxBytes)
                || item.Value is < 0 or > ContractLimits.MetadataValueMaxBytes)
            || options.RequiredMetadataKeys.Any(key =>
                !options.MetadataValueMaxBytes.ContainsKey(key)))
        {
            throw new ProvisioningConfigurationException(
                $"Policy {options.GameId}/{options.EnvironmentId} has an invalid metadata schema.");
        }

        if (options.MaxListingsPerPrincipal is < 1 or > ProvisioningLimits.MaxListingsPerPrincipal
            || options.MaxAnonymousListingsPerAddress < 0
            || options.MaxAnonymousListingsPerAddress > options.MaxListingsPerPrincipal
            || options.MaxActiveJoinAttempts is < 1
                or > ProvisioningLimits.MaxActiveJoinAttemptsPerPolicy
            || !Enum.IsDefined(options.FallbackPolicy))
        {
            throw new ProvisioningConfigurationException(
                $"Policy {options.GameId}/{options.EnvironmentId} has invalid quotas or fallback policy.");
        }
    }
}