import { useState } from "react";
import conferencesData from "@/data/conferences.yml";
import { Conference } from "@/types/conference";
import { Calendar as CalendarIcon, Tag } from "lucide-react";
import { Calendar } from "@/components/ui/calendar";
import { parseISO, format, isValid, isSameMonth, isSameYear, isSameDay } from "date-fns";
import { Toggle } from "@/components/ui/toggle";

const CalendarPage = () => {
  const [selectedDate, setSelectedDate] = useState<Date | undefined>(new Date());
  const [isYearView, setIsYearView] = useState(false);
  
  // Helper function to safely parse dates
  const safeParseISO = (dateString: string | undefined | number): Date | null => {
    if (!dateString || dateString === 'TBD') return null;
    const dateStr = typeof dateString === 'number' ? dateString.toString() : dateString;
    
    try {
      const normalizedDate = dateStr.replace(/(\d{4})-(\d{1})-(\d{1,2})/, '$1-0$2-$3')
                                  .replace(/(\d{4})-(\d{2})-(\d{1})/, '$1-$2-0$3');
      const parsedDate = parseISO(normalizedDate);
      return isValid(parsedDate) ? parsedDate : null;
    } catch (error) {
      console.error("Error parsing date:", dateString);
      return null;
    }
  };

  // Get events for the current month/year
  const getEvents = (date: Date) => {
    return conferencesData.filter((conf: Conference) => {
      const deadlineDate = safeParseISO(conf.deadline);
      const startDate = safeParseISO(conf.start);
      const endDate = safeParseISO(conf.end);

      const dateMatches = isYearView ? isSameYear : isSameMonth;

      // Check if deadline is in the selected period
      const deadlineInPeriod = deadlineDate && dateMatches(deadlineDate, date);
      
      // Check if any part of the conference falls in the selected period
      let conferenceInPeriod = false;
      if (startDate && endDate) {
        let currentDate = new Date(startDate);
        while (currentDate <= endDate) {
          if (dateMatches(currentDate, date)) {
            conferenceInPeriod = true;
            break;
          }
          currentDate.setDate(currentDate.getDate() + 1);
        }
      } else if (startDate) {
        conferenceInPeriod = dateMatches(startDate, date);
      }

      return deadlineInPeriod || conferenceInPeriod;
    });
  };

  // Get all events for day indicators
  const getDayEvents = (date: Date) => {
    return conferencesData.reduce((acc, conf) => {
      const deadlineDate = safeParseISO(conf.deadline);
      const startDate = safeParseISO(conf.start);
      const endDate = safeParseISO(conf.end);

      if (deadlineDate && isSameDay(deadlineDate, date)) {
        acc.deadlines.push(conf);
      }

      if (startDate && endDate) {
        if (date >= startDate && date <= endDate) {
          acc.conferences.push(conf);
        }
      } else if (startDate && isSameDay(startDate, date)) {
        acc.conferences.push(conf);
      }

      return acc;
    }, { deadlines: [], conferences: [] } as { deadlines: Conference[], conferences: Conference[] });
  };

  const events = selectedDate ? getEvents(selectedDate) : [];

  // Custom day content renderer
  const renderDayContent = (day: Date) => {
    const dayEvents = getDayEvents(day);
    const hasDeadlines = dayEvents.deadlines.length > 0;
    const hasConferences = dayEvents.conferences.length > 0;

    return (
      <div className="relative w-full h-full flex flex-col items-center">
        <span className="mb-1">{format(day, 'd')}</span>
        <div className="absolute bottom-0 left-0 right-0 flex gap-0.5 px-1">
          {hasDeadlines && (
            <div className="h-0.5 flex-1 bg-red-500" title="Deadline" />
          )}
          {hasConferences && (
            <div className="h-0.5 flex-1 bg-purple-600" title="Conference" />
          )}
        </div>
      </div>
    );
  };

  return (
    <div className="min-h-screen bg-neutral-light p-6">
      <div className="max-w-7xl mx-auto">
        <div className="flex flex-col items-center mb-8">
          <h1 className="text-3xl font-bold mb-4">Calendar Overview</h1>
          <div className="flex items-center gap-4">
            <Toggle 
              pressed={!isYearView} 
              onPressedChange={() => setIsYearView(false)}
              variant="outline"
            >
              Month
            </Toggle>
            <Toggle 
              pressed={isYearView} 
              onPressedChange={() => setIsYearView(true)}
              variant="outline"
            >
              Year
            </Toggle>
          </div>
        </div>

        <div className="flex justify-center gap-6 mb-6">
          <div className="flex items-center gap-2">
            <div className="w-4 h-1 bg-purple-600" />
            <span>Conference Dates</span>
          </div>
          <div className="flex items-center gap-2">
            <div className="w-4 h-1 bg-red-500" />
            <span>Submission Deadlines</span>
          </div>
        </div>

        <div className="grid grid-cols-1 gap-8">
          <div className="mx-auto w-full max-w-4xl">
            <Calendar
              mode="single"
              selected={selectedDate}
              onSelect={setSelectedDate}
              numberOfMonths={isYearView ? 12 : 1}
              className="bg-white rounded-lg p-6 shadow-sm mx-auto w-full"
              components={{
                Day: ({ date, ...props }) => (
                  <button {...props} className="w-full h-full p-2">
                    {renderDayContent(date)}
                  </button>
                ),
              }}
              classNames={{
                months: `grid ${isYearView ? 'grid-cols-3 gap-4' : ''} justify-center`,
                month: "space-y-4",
                caption: "flex justify-center pt-1 relative items-center mb-4",
                caption_label: "text-lg font-semibold",
                table: "w-full border-collapse space-y-1",
                head_row: "flex",
                head_cell: "text-muted-foreground rounded-md w-10 font-normal text-[0.8rem]",
                row: "flex w-full mt-2",
                cell: `h-10 w-10 text-center text-sm p-0 relative focus-within:relative focus-within:z-20 
                      [&:has([aria-selected])]:bg-accent first:[&:has([aria-selected])]:rounded-l-md 
                      last:[&:has([aria-selected])]:rounded-r-md hover:bg-neutral-50`,
                day: "h-10 w-10 p-0 font-normal hover:bg-neutral-100 rounded-lg transition-colors",
                day_today: "bg-neutral-100 text-primary font-semibold",
                nav: "space-x-1 flex items-center",
                nav_button: "h-7 w-7 bg-transparent p-0 opacity-50 hover:opacity-100",
                nav_button_previous: "absolute left-1",
                nav_button_next: "absolute right-1",
              }}
            />
          </div>

          {selectedDate && events.length > 0 && (
            <div className="mx-auto w-full max-w-3xl space-y-4">
              <h2 className="text-xl font-semibold flex items-center gap-2">
                <CalendarIcon className="h-5 w-5" />
                Events in {format(selectedDate, isYearView ? 'yyyy' : 'MMMM yyyy')}
              </h2>
              <div className="space-y-4">
                {events.map((conf: Conference) => (
                  <div key={conf.id} className="bg-white p-4 rounded-lg shadow-sm">
                    <h3 className="font-semibold text-lg">{conf.title}</h3>
                    <div className="space-y-1">
                      {conf.deadline && safeParseISO(conf.deadline) && (
                        <p className="text-red-500">
                          Submission Deadline: {format(safeParseISO(conf.deadline)!, 'MMMM d, yyyy')}
                        </p>
                      )}
                      {conf.start && (
                        <p className="text-purple-600">
                          Conference Date: {format(safeParseISO(conf.start)!, 'MMMM d')}
                          {conf.end ? ` - ${format(safeParseISO(conf.end)!, 'MMMM d, yyyy')}` : 
                            `, ${format(safeParseISO(conf.start)!, 'yyyy')}`}
                        </p>
                      )}
                    </div>
                    <div className="mt-2 flex flex-wrap gap-2">
                      {conf.tags.map((tag) => (
                        <span key={tag} className="inline-flex items-center px-2 py-1 rounded-full 
                          text-xs bg-neutral-100">
                          <Tag className="h-3 w-3 mr-1" />
                          {tag}
                        </span>
                      ))}
                    </div>
                  </div>
                ))}
              </div>
            </div>
          )}
        </div>
      </div>
    </div>
  );
};

export default CalendarPage;