import {
  deriveResourceForecast,
  getMonthRange,
  countWorkingDaysInOverlap,
  calculateSAH,
  type AssignmentSlice,
} from "@planarchy/engine";
import type { SpainScheduleRule } from "@planarchy/shared";
import { isChargeabilityActualBooking, listAssignmentBookings } from "@planarchy/application";
import { VacationStatus } from "@planarchy/db";
import { createNotificationsForUsers } from "./create-notification.js";

/**
 * Minimal DB client type for chargeability alerts.
 * Uses structural typing so we can pass in `prisma as any` from the cron route.
 */
type DbClient = {
  resource: {
    findMany: (args: {
      where: Record<string, unknown>;
      select: Record<string, unknown>;
    }) => Promise<
      Array<{
        id: string;
        displayName: string;
        fte: number;
        chargeabilityTarget: number;
        country: { dailyWorkingHours: number | null; scheduleRules: unknown } | null;
        managementLevelGroup: { targetPercentage: number | null } | null;
      }>
    >;
  };
  vacation: {
    findMany: (args: {
      where: Record<string, unknown>;
      select: Record<string, unknown>;
    }) => Promise<
      Array<{
        resourceId: string;
        startDate: Date;
        endDate: Date;
        type: string;
        isHalfDay: boolean;
      }>
    >;
  };
  notification: {
    findFirst: (args: {
      where: Record<string, unknown>;
      select: { id: true };
    }) => Promise<{ id: string } | null>;
    create: (args: {
      data: {
        userId: string;
        type: string;
        category: string;
        priority: string;
        title: string;
        body: string;
        entityId: string;
        entityType: string;
        link: string;
        channel: string;
      };
    }) => Promise<{ id: string; userId: string }>;
  };
  user: {
    findMany: (args: {
      where: { systemRole: { in: string[] } };
      select: { id: true };
    }) => Promise<Array<{ id: string }>>;
  };
};

/** Alert when chargeability is more than 15pp below target */
const GAP_THRESHOLD_PP = 15;

/**
 * Find resources whose current-month chargeability is >15 percentage points
 * below their target, and create a notification for all managers.
 *
 * Duplicate-safe: skips resources that already have an alert this month.
 *
 * Returns the number of new alerts created.
 */
export async function checkChargeabilityAlerts(
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  db: any,
): Promise<number> {
  const now = new Date();
  const year = now.getUTCFullYear();
  const month = now.getUTCMonth() + 1;
  const { start: monthStart, end: monthEnd } = getMonthRange(year, month);
  const monthKey = `${year}-${String(month).padStart(2, "0")}`;

  // Fetch active, chg-responsible resources
  const resources = await (db as DbClient).resource.findMany({
    where: {
      isActive: true,
      chgResponsibility: true,
      departed: false,
      rolledOff: false,
    },
    select: {
      id: true,
      displayName: true,
      fte: true,
      chargeabilityTarget: true,
      country: { select: { dailyWorkingHours: true, scheduleRules: true } },
      managementLevelGroup: { select: { targetPercentage: true } },
    },
  });

  if (resources.length === 0) return 0;

  const resourceIds = resources.map((r) => r.id);

  // Fetch bookings for the current month
  const allBookings = await listAssignmentBookings(db, {
    startDate: monthStart,
    endDate: monthEnd,
    resourceIds,
  });

  // Fetch vacations for the current month
  const vacations = await (db as DbClient).vacation.findMany({
    where: {
      resourceId: { in: resourceIds },
      status: VacationStatus.APPROVED,
      startDate: { lte: monthEnd },
      endDate: { gte: monthStart },
    },
    select: {
      resourceId: true,
      startDate: true,
      endDate: true,
      type: true,
      isHalfDay: true,
    },
  });

  // Compute chargeability per resource
  const underperformers: Array<{ resource: typeof resources[0]; chg: number; target: number; gap: number }> = [];

  for (const resource of resources) {
    const dailyHours = resource.country?.dailyWorkingHours ?? 8;

    // Compute absence dates for SAH
    const resourceVacations = vacations.filter((v) => v.resourceId === resource.id);
    const absenceDates: string[] = [];
    for (const v of resourceVacations) {
      const vStart = new Date(Math.max(v.startDate.getTime(), monthStart.getTime()));
      const vEnd = new Date(Math.min(v.endDate.getTime(), monthEnd.getTime()));
      if (vStart > vEnd) continue;
      const cursor = new Date(vStart);
      cursor.setUTCHours(0, 0, 0, 0);
      const endNorm = new Date(vEnd);
      endNorm.setUTCHours(0, 0, 0, 0);
      while (cursor <= endNorm) {
        absenceDates.push(cursor.toISOString().slice(0, 10));
        cursor.setUTCDate(cursor.getUTCDate() + 1);
      }
    }

    const scheduleRules = (resource.country?.scheduleRules ?? null) as SpainScheduleRule | null;
    const sahResult = calculateSAH({
      dailyWorkingHours: dailyHours,
      scheduleRules,
      fte: resource.fte,
      periodStart: monthStart,
      periodEnd: monthEnd,
      publicHolidays: [],
      absenceDays: absenceDates,
    });

    // Build assignment slices
    const resourceBookings = allBookings.filter(
      (b) => b.resourceId === resource.id && isChargeabilityActualBooking(b, false),
    );

    const slices: AssignmentSlice[] = resourceBookings.map((b) => {
      const workingDays = countWorkingDaysInOverlap(monthStart, monthEnd, b.startDate, b.endDate);
      return {
        hoursPerDay: b.hoursPerDay,
        workingDays,
        categoryCode: "Chg", // simplified — treat all actual bookings as chargeable
      };
    });

    const targetPct = resource.managementLevelGroup?.targetPercentage
      ?? (resource.chargeabilityTarget / 100);

    const forecast = deriveResourceForecast({
      fte: resource.fte,
      targetPercentage: targetPct,
      assignments: slices,
      sah: sahResult.standardAvailableHours,
    });

    const chgPct = forecast.chg * 100;
    const targetPctVal = targetPct * 100;
    const gap = targetPctVal - chgPct;

    if (gap > GAP_THRESHOLD_PP) {
      underperformers.push({
        resource,
        chg: Math.round(chgPct),
        target: Math.round(targetPctVal),
        gap: Math.round(gap),
      });
    }
  }

  if (underperformers.length === 0) return 0;

  // Fetch managers to notify
  const managers = await (db as DbClient).user.findMany({
    where: { systemRole: { in: ["ADMIN", "MANAGER"] } },
    select: { id: true },
  });

  if (managers.length === 0) return 0;

  let alertCount = 0;

  for (const { resource, chg, target, gap } of underperformers) {
    // Duplicate check: one alert per resource per month
    const entityId = `chg-alert-${resource.id}-${monthKey}`;
    const existing = await (db as DbClient).notification.findFirst({
      where: {
        entityId,
        entityType: "chargeability_alert",
        type: "CHARGEABILITY_ALERT",
      },
      select: { id: true },
    });

    if (existing) continue;

    await createNotificationsForUsers({
      db: db as DbClient,
      userIds: managers.map((m) => m.id),
      type: "CHARGEABILITY_ALERT",
      category: "NOTIFICATION",
      priority: "HIGH",
      title: `Low chargeability: ${resource.displayName}`,
      body: `${resource.displayName} is at ${chg}% chargeability this month (target: ${target}%, gap: ${gap}pp).`,
      entityId,
      entityType: "chargeability_alert",
      link: "/chargeability",
      channel: "in_app",
    });

    alertCount++;
  }

  return alertCount;
}