using NeonSprawl.Server.Game.Factions;

namespace NeonSprawl.Server.Game.Contracts;

/// <summary>
/// Server-authoritative contract issuance from template catalog + seed inputs (NEO-147).
/// HTTP: E7M4-08 (NEO-151). Telemetry hook sites: E7M4-09 (NEO-152).
/// </summary>
public static class ContractGeneratorOperations
{
    /// <summary>
    /// Issues an active contract instance when template selection and store gates pass.
    /// </summary>
    public static ContractIssueOperationResult TryIssue(
        string playerId,
        string? templateId,
        string seedBucket,
        int? zoneDifficultyBand,
        IContractTemplateRegistry templateRegistry,
        IContractInstanceStore instanceStore,
        IFactionStandingStore standingStore,
        TimeProvider timeProvider)
    {
        var normalizedPlayerId = ContractInstanceIds.NormalizePlayerId(playerId);
        var normalizedSeedBucket = ContractInstanceIds.NormalizeSeedBucket(seedBucket);
        var band = zoneDifficultyBand ?? 1;

        if (normalizedPlayerId.Length == 0 || normalizedSeedBucket.Length == 0)
        {
            return Deny(ContractGeneratorReasonCodes.InvalidIds);
        }

        if (!instanceStore.CanWritePlayer(normalizedPlayerId))
        {
            return Deny(ContractGeneratorReasonCodes.PlayerNotWritable);
        }

        if (instanceStore.TryGetActiveForPlayer(normalizedPlayerId, out var activeSnapshot))
        {
            return Deny(ContractGeneratorReasonCodes.ActiveContractExists, activeSnapshot);
        }

        if (!TrySelectTemplate(
                templateId,
                band,
                normalizedPlayerId,
                templateRegistry,
                standingStore,
                out var template,
                out var denyReason))
        {
            return Deny(denyReason!);
        }

        var instanceId = ContractInstanceIds.MakeDeterministicInstanceId(
            normalizedPlayerId,
            template!.Id,
            normalizedSeedBucket);
        if (instanceId.Length == 0)
        {
            return Deny(ContractGeneratorReasonCodes.InvalidIds);
        }

        if (instanceStore.TryCreateActive(
                normalizedPlayerId,
                instanceId,
                template.Id,
                normalizedSeedBucket,
                timeProvider.GetUtcNow(),
                out var snapshot))
        {
            return Success(snapshot, template.EncounterTemplateId);
        }

        return DenyCreateFailure(instanceStore, normalizedPlayerId, snapshot);
    }

    private static bool TrySelectTemplate(
        string? templateId,
        int band,
        string normalizedPlayerId,
        IContractTemplateRegistry templateRegistry,
        IFactionStandingStore standingStore,
        out ContractTemplateRow? template,
        out string? denyReason)
    {
        template = null;
        denyReason = null;

        var normalizedTemplateId = ContractInstanceIds.NormalizeTemplateId(templateId);
        if (normalizedTemplateId.Length > 0)
        {
            if (!templateRegistry.TryGetDefinition(normalizedTemplateId, out template))
            {
                denyReason = ContractGeneratorReasonCodes.UnknownTemplate;
                return false;
            }

            if (!IsEligible(template, band, normalizedPlayerId, standingStore))
            {
                denyReason = ContractGeneratorReasonCodes.NoEligibleTemplate;
                template = null;
                return false;
            }

            return true;
        }

        foreach (var candidate in templateRegistry.GetDefinitionsInIdOrder())
        {
            if (!IsEligible(candidate, band, normalizedPlayerId, standingStore))
            {
                continue;
            }

            template = candidate;
            return true;
        }

        denyReason = ContractGeneratorReasonCodes.NoEligibleTemplate;
        return false;
    }

    private static bool IsEligible(
        ContractTemplateRow template,
        int band,
        string normalizedPlayerId,
        IFactionStandingStore standingStore)
    {
        if (template.ZoneDifficultyBand != band)
        {
            return false;
        }

        var gate = FactionGateOperations.TryEvaluate(
            normalizedPlayerId,
            [template.MinFactionStanding],
            standingStore);
        return gate.Success;
    }

    private static ContractIssueOperationResult DenyCreateFailure(
        IContractInstanceStore instanceStore,
        string normalizedPlayerId,
        ContractInstanceState attemptSnapshot)
    {
        if (instanceStore.TryGetActiveForPlayer(normalizedPlayerId, out var active))
        {
            return Deny(ContractGeneratorReasonCodes.ActiveContractExists, active);
        }

        if (attemptSnapshot.Status == ContractInstanceStatus.Active)
        {
            return Deny(ContractGeneratorReasonCodes.ActiveContractExists, attemptSnapshot);
        }

        return Deny(ContractGeneratorReasonCodes.InvalidIds, attemptSnapshot);
    }

    private static ContractIssueOperationResult Success(
        ContractInstanceState snapshot,
        string encounterTemplateId) =>
        new(true, null, snapshot, encounterTemplateId);

    private static ContractIssueOperationResult Deny(
        string reasonCode,
        ContractInstanceState? snapshot = null) =>
        new(false, reasonCode, snapshot, null);
}