import type { Pool, PoolClient } from 'pg';
import { resolveBillingAccessState } from '../../../shared/billing/lifecycle.js';
import type { AccountBillingState } from '../../../shared/types.js';
import type { EntitlementDecision, UsageAction, UsageAmount, UsageCostEstimate, UsageResource } from '../../../shared/billing/entitlements.js';
import { evaluateActionEntitlement, isActivePlanCodeForEntitlements } from '../../../shared/billing/entitlements.js';
import { ensureWorkspaceForUser } from '../account/repository.js';
import { ensureBillingAccountForWorkspace, incrementUsageCounter } from './repository.js';
import { ensureCurrentUsagePeriodForBillingAccount, getWorkspaceBillingState } from './service.js';

type DbClient = Pool | PoolClient;

export interface WorkspaceEnforcementContext {
  workspaceId: string;
  billing: AccountBillingState;
}

export interface EnforcementCheckInput {
  userId: string;
  workspaceId: string;
  action: UsageAction;
  costEstimate: UsageCostEstimate;
}

export interface EnforcementCheckResult {
  allowed: boolean;
  decision: EntitlementDecision;
}

export interface UsageRecordingInput {
  workspaceId: string;
  action: UsageAction;
  costEstimate: UsageCostEstimate;
}

export async function getWorkspaceEnforcementContext(
  db: DbClient,
  user: { id: string; email: string; displayName?: string | null },
): Promise<WorkspaceEnforcementContext> {
  const workspace = await ensureWorkspaceForUser(db, user);

  if (!workspace) {
    throw new Error('Failed to resolve enforcement workspace.');
  }

  const billing = await getWorkspaceBillingState(db, workspace.id);

  return {
    workspaceId: workspace.id,
    billing,
  };
}

export async function checkActionEntitlementForWorkspace(
  db: DbClient,
  input: EnforcementCheckInput,
): Promise<EnforcementCheckResult> {
  const billing = await getWorkspaceBillingState(db, input.workspaceId);

  if (!billing.planCode || !isActivePlanCodeForEntitlements(billing.planCode)) {
    return {
      allowed: false,
      decision: {
        status: 'blocked_upgrade_required',
        denialReason: 'billing_not_configured',
        action: input.action,
        resource: getPrimaryUsageAmount(input.costEstimate)?.resource ?? 'research_credits',
        requiredAmount: getPrimaryUsageAmount(input.costEstimate)?.amount ?? 0,
        remainingAmount: 0,
        currentPlanCode: null,
        suggestedUpgradePlanCode: 'starter_monthly',
        addonEligible: false,
        contactSalesRequired: false,
      },
    };
  }

  const billingAccess = resolveBillingAccessState({
    status: billing.status,
    currentPeriodEndsAt: billing.currentPeriodEndsAt,
    cancelAtPeriodEnd: billing.cancelAtPeriodEnd,
    gracePeriodEndsAt: billing.gracePeriodEndsAt,
  });

  if (input.costEstimate.isChargeable && billingAccess.accessMode === 'blocked') {
    return {
      allowed: false,
      decision: {
        status: 'blocked_upgrade_required',
        denialReason: mapBillingStatusToDenialReason(billing.status),
        action: input.action,
        resource: getPrimaryUsageAmount(input.costEstimate)?.resource ?? 'research_credits',
        requiredAmount: getPrimaryUsageAmount(input.costEstimate)?.amount ?? 0,
        remainingAmount: 0,
        currentPlanCode: billing.planCode,
        suggestedUpgradePlanCode: billing.planCode,
        addonEligible: false,
        contactSalesRequired: false,
      },
    };
  }

  if (!input.costEstimate.isChargeable) {
    return {
      allowed: true,
      decision: evaluateActionEntitlement({
        planCode: billing.planCode,
        action: input.action,
        resource: getPrimaryUsageAmount(input.costEstimate)?.resource ?? 'research_credits',
        requiredAmount: getPrimaryUsageAmount(input.costEstimate)?.amount ?? 0,
        remainingAmount: null,
      }),
    };
  }

  const primaryAmount = getPrimaryUsageAmount(input.costEstimate);

  if (!primaryAmount) {
    throw new Error(`Missing usage amount for chargeable action '${input.action}'.`);
  }

  const remainingAmount = getRemainingAmountForResource(billing, primaryAmount.resource);
  const decision = evaluateActionEntitlement({
    planCode: billing.planCode,
    action: input.action,
    resource: primaryAmount.resource,
    requiredAmount: primaryAmount.amount,
    remainingAmount,
  });

  return {
    allowed: decision.status === 'allowed',
    decision,
  };
}

export async function recordSuccessfulActionUsage(
  db: DbClient,
  input: UsageRecordingInput,
): Promise<void> {
  if (!input.costEstimate.isChargeable) {
    return;
  }

  const billingAccount = await ensureBillingAccountForWorkspace(db, input.workspaceId);
  const usagePeriod = await ensureCurrentUsagePeriodForBillingAccount(db, billingAccount);

  if (!usagePeriod) {
    return;
  }

  for (const usageAmount of input.costEstimate.amounts) {
    if (usageAmount.amount <= 0) {
      continue;
    }

    await incrementUsageCounter(db, {
      usagePeriodId: usagePeriod.id,
      workspaceId: input.workspaceId,
      resource: usageAmount.resource,
      delta: usageAmount.amount,
    });
  }
}

export function buildEntitlementErrorResponse(decision: EntitlementDecision) {
  return {
    statusCode: decision.denialReason === 'quota_exhausted' ? 409 : 403,
    body: {
      error: formatEntitlementErrorMessage(decision),
      code: 'entitlement_blocked' as const,
      entitlement: decision,
    },
  };
}

function getRemainingAmountForResource(billing: AccountBillingState, resource: UsageResource): number | null {
  const resourceSummary = billing.usage.find((usage) => usage.resource === resource);

  if (!resourceSummary) {
    return 0;
  }

  return resourceSummary.remaining;
}

function getPrimaryUsageAmount(costEstimate: UsageCostEstimate): UsageAmount | null {
  return costEstimate.amounts[0] ?? null;
}

function formatEntitlementErrorMessage(decision: EntitlementDecision) {
  switch (decision.denialReason) {
    case 'billing_not_configured':
      return 'A billing plan is required before this action can run.';
    case 'billing_past_due':
      return 'Payment is overdue and billing access is currently blocked.';
    case 'billing_canceled':
      return 'This subscription is canceled. Reactivate billing to continue.';
    case 'billing_inactive':
      return 'Billing is inactive for this workspace.';
    case 'feature_not_available':
      return 'Your current plan does not include this feature.';
    case 'not_launch_ready':
      return 'This feature is included in plan definitions but is not launch-ready yet.';
    case 'custom_enterprise_only':
      return 'This action requires an enterprise or custom sales engagement.';
    case 'quota_exhausted':
      return 'Your current plan has exhausted the available allowance for this action.';
    default:
      return 'This action is blocked by the current entitlement policy.';
  }
}

function mapBillingStatusToDenialReason(status: AccountBillingState['status']) {
  switch (status) {
    case 'past_due':
      return 'billing_past_due' as const;
    case 'canceled':
      return 'billing_canceled' as const;
    case 'inactive':
    case 'not_configured':
      return 'billing_inactive' as const;
    case 'active':
      return 'billing_inactive' as const;
  }
}

// Export policy exists in shared billing modules, but route-level export enforcement
// stays deferred until export generation moves to a backend endpoint.