// ABOUTME: API route for ICS calendar feed generation.
// ABOUTME: Returns subscribable iCal feed with cycle phases and warnings.
import { type NextRequest, NextResponse } from "next/server";

import { generateIcsFeed } from "@/lib/ics";
import { logger } from "@/lib/logger";
import { createPocketBaseClient } from "@/lib/pocketbase";

interface RouteParams {
  params: Promise<{
    userId: string;
    token: string;
  }>;
}

export async function GET(_request: NextRequest, { params }: RouteParams) {
  const { userId, token: rawToken } = await params;
  // Strip .ics suffix if present (Next.js may include it in the param)
  const token = rawToken.endsWith(".ics") ? rawToken.slice(0, -4) : rawToken;
  const pb = createPocketBaseClient();

  try {
    // Fetch user from database
    const user = await pb.collection("users").getOne(userId);

    // Check if user has a calendar token set
    if (!user.calendarToken) {
      return NextResponse.json(
        { error: "Unauthorized: Calendar not configured" },
        { status: 401 },
      );
    }

    // Validate token (case-sensitive comparison)
    if (user.calendarToken !== token) {
      return NextResponse.json(
        { error: "Unauthorized: Invalid token" },
        { status: 401 },
      );
    }

    // Fetch period logs for prediction accuracy display
    const periodLogs = await pb.collection("period_logs").getFullList({
      filter: `user = "${userId}"`,
      sort: "-startDate",
    });

    // Generate ICS feed with 90 days of events (3 months)
    const icsContent = generateIcsFeed({
      lastPeriodDate: new Date(user.lastPeriodDate as string),
      cycleLength: user.cycleLength as number,
      monthsAhead: 3,
      periodLogs: periodLogs.map((log) => ({
        id: log.id,
        user: log.user as string,
        startDate: new Date(log.startDate as string),
        predictedDate: log.predictedDate
          ? new Date(log.predictedDate as string)
          : null,
        created: new Date(log.created as string),
      })),
    });

    // Return ICS content with appropriate headers
    return new NextResponse(icsContent, {
      status: 200,
      headers: {
        "Content-Type": "text/calendar; charset=utf-8",
        "Cache-Control": "public, max-age=3600", // Cache for 1 hour
        "Content-Disposition": "attachment; filename=phaseflow-calendar.ics",
      },
    });
  } catch (error) {
    // Check if error is a "not found" error from PocketBase
    if (
      error instanceof Error &&
      (error as unknown as { status?: number }).status === 404
    ) {
      return NextResponse.json({ error: "User not found" }, { status: 404 });
    }

    logger.error({ err: error, userId }, "Calendar feed error");
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}