import { Router } from "express";
import { db } from "../db";
import { authenticateToken, type AuthenticatedRequest } from "../middleware/auth.middleware";
import { tenantIsolation } from "../middleware/tenant.middleware";
import { tasks, forms, formStatuses, taskAssignees } from "@shared/schema";
import { eq, and, or, gte, lte, sql, inArray, isNotNull, asc, exists } from "drizzle-orm";

export const calendarRouter = Router();

interface CalendarTask {
  id: number;
  title: string;
  dueDate: string;
  formId: number;
  currentStatusId: number;
  statusColor: string | null;
  statusName: string | null;
  isCompleted: boolean;
  isAllDay: boolean;
}

function parseDateParam(value: unknown): Date | null {
  if (typeof value !== "string" || !value) return null;
  const d = new Date(value);
  if (isNaN(d.getTime())) return null;
  return d;
}

function isMidnight(date: Date): boolean {
  // All-day tasks are stored in the DB with time 00:00:00 (no timezone).
  // Checking UTC midnight makes the detection independent of the client's timezone.
  return date.getUTCHours() === 0 && date.getUTCMinutes() === 0 && date.getUTCSeconds() === 0 && date.getUTCMilliseconds() === 0;
}

function parseFormIds(value: unknown): number[] | undefined {
  if (typeof value !== "string" || !value) return undefined;
  const ids = value
    .split(",")
    .map((s) => parseInt(s.trim(), 10))
    .filter((n) => !isNaN(n));
  return ids.length > 0 ? ids : undefined;
}

// GET /api/calendar/tasks?from=ISO&to=ISO&formIds=1,2,3
// Returns tasks assigned to current user within date range, excluding completed/final tasks.
calendarRouter.get("/api/calendar/tasks", authenticateToken, tenantIsolation, async (req: AuthenticatedRequest, res) => {
  try {
    const from = parseDateParam(req.query.from);
    const to = parseDateParam(req.query.to);
    const formIds = parseFormIds(req.query.formIds);

    if (!from || !to) {
      return res.status(400).json({ success: false, error: "Требуются параметры from и to" });
    }

    const userId = req.user!.id;
    const organizationId = req.organizationId!;

    const conditions = [
      eq(forms.organizationId, organizationId),
      eq(tasks.isCompleted, false),
      eq(formStatuses.isFinal, false),
      isNotNull(tasks.dueDate),
      gte(tasks.dueDate, from),
      lte(tasks.dueDate, to),
      or(eq(tasks.assignedTo, userId), exists(
        db
          .select()
          .from(taskAssignees)
          .where(and(
            eq(taskAssignees.taskId, tasks.id),
            eq(taskAssignees.userId, userId)
          ))
      ))
    ];

    if (formIds) {
      conditions.push(inArray(tasks.formId, formIds));
    }

    const results = await db
      .select({
        id: tasks.id,
        title: tasks.title,
        dueDate: tasks.dueDate,
        formId: tasks.formId,
        currentStatusId: tasks.currentStatusId,
        statusColor: formStatuses.color,
        statusName: formStatuses.name,
        isCompleted: tasks.isCompleted,
      })
      .from(tasks)
      .innerJoin(forms, eq(tasks.formId, forms.id))
      .innerJoin(formStatuses, eq(tasks.currentStatusId, formStatuses.id))
      .where(and(...conditions))
      .orderBy(asc(tasks.dueDate));

    const mapped: CalendarTask[] = results.map((row) => {
      const due = row.dueDate ? new Date(row.dueDate) : null;
      return {
        id: row.id,
        title: row.title,
        dueDate: row.dueDate ? row.dueDate.toISOString() : "",
        formId: row.formId,
        currentStatusId: row.currentStatusId,
        statusColor: row.statusColor,
        statusName: row.statusName,
        isCompleted: row.isCompleted ?? false,
        isAllDay: due ? isMidnight(due) : false,
      };
    });

    res.json({ success: true, tasks: mapped });
  } catch (error) {
    console.error("Calendar tasks error:", error);
    res.status(500).json({ success: false, error: "Ошибка при получении задач календаря" });
  }
});

// PUT /api/calendar/tasks/:id/due-date
// Updates only dueDate for drag-and-drop rescheduling.
calendarRouter.put("/api/calendar/tasks/:id/due-date", authenticateToken, tenantIsolation, async (req: AuthenticatedRequest, res) => {
  try {
    const taskId = parseInt(req.params.id, 10);
    const { dueDate } = req.body;

    if (isNaN(taskId)) {
      return res.status(400).json({ success: false, error: "Неверный ID задачи" });
    }

    const newDueDate = dueDate ? new Date(dueDate) : null;
    if (newDueDate && isNaN(newDueDate.getTime())) {
      return res.status(400).json({ success: false, error: "Неверная дата" });
    }

    const organizationId = req.organizationId!;

    const [updated] = await db
      .update(tasks)
      .set({
        dueDate: newDueDate,
        updatedAt: new Date(),
      })
      .where(and(
        eq(tasks.id, taskId),
        exists(
          db
            .select()
            .from(forms)
            .where(and(eq(forms.id, tasks.formId), eq(forms.organizationId, organizationId)))
        )
      ))
      .returning();

    if (!updated) {
      return res.status(404).json({ success: false, error: "Задача не найдена" });
    }

    res.json({ success: true, task: updated });
  } catch (error) {
    console.error("Calendar update due date error:", error);
    res.status(500).json({ success: false, error: "Ошибка при обновлении срока задачи" });
  }
});