import React, { useMemo, useState } from 'react';
import { Button, SearchInput } from '@/components/ds';
import { useApplications, useInterviews, useJobPostings, useUpdateApplication, useHireCandidate } from '@/lib/krowHooks';
import { base44 } from '@/api/base44Client';
import { toast } from 'react-hot-toast';
import { AdminPage, Toolbar } from '@/pages/admin/_shell';
import { FilterSelect } from '@/pages/admin/Positions';
import CandidateCard from '@/components/krow/CandidateCard';
import AIInterviewModal from '@/components/krow/AIInterviewModal';
import ScheduleInterviewModal from '@/components/krow/ScheduleInterviewModal';
import MessageCandidateModal from '@/components/krow/MessageCandidateModal';

const SCORE_BANDS = {
  all: () => true,
  top: (s) => s >= 80,
  strong: (s) => s >= 60 && s < 80,
  weak: (s) => s > 0 && s < 60,
  unscored: (s) => !s,
};

const SORTS = {
  score: { label: 'Highest score', compare: (a, b) => (b.ai_score || 0) - (a.ai_score || 0) },
  recent: { label: 'Recent activity', compare: (a, b) => new Date(b.updated_date) - new Date(a.updated_date) },
  name: { label: 'Name A–Z', compare: (a, b) => a.applicant_name.localeCompare(b.applicant_name) },
  experience: { label: 'Most experience', compare: (a, b) => (b.years_experience || 0) - (a.years_experience || 0) },
};

export default function AdminCandidates() {
  const { data: applications = [], isLoading } = useApplications();
  const { data: postings = [] } = useJobPostings();
  const { data: interviews = [] } = useInterviews();
  const updateApp = useUpdateApplication();
  const hireCandidate = useHireCandidate();

  const [search, setSearch] = useState('');
  const [position, setPosition] = useState('all');
  const [stage, setStage] = useState('all');
  const [band, setBand] = useState('all');
  const [sort, setSort] = useState('score');

  const [interviewApp, setInterviewApp] = useState(null);
  const [scheduleApp, setScheduleApp] = useState(null);
  const [messageApp, setMessageApp] = useState(null);

  const handleDecline = async (app) => {
    try {
      await updateApp.mutateAsync({ id: app.id, data: { status: 'rejected' } });
      toast.success(`${app.applicant_name} declined`);
    } catch (e) {
      toast.error('Failed to decline candidate');
    }
  };

  const handleDelete = async (app) => {
    try {
      await base44.entities.JobApplication.delete(app.id);
      toast.success(`${app.applicant_name} deleted`);
    } catch (e) {
      toast.error('Failed to delete candidate');
    }
  };

  const handleHire = async (app) => {
    try {
      const job = postings.find(p => p.id === app.job_posting_id);
      await hireCandidate.mutateAsync({ application: app, job });
      toast.success(`${app.applicant_name} hired!`);
    } catch (e) {
      toast.error('Failed to hire candidate');
    }
  };

  const handleAction = (app) => {
    if (app.status === 'interview') {
      setInterviewApp(app);
    } else {
      setScheduleApp(app);
    }
  };

  const positions = useMemo(
    () => [...new Set(applications.map((a) => a.job_title).filter(Boolean))].sort(),
    [applications]
  );

  const filtered = useMemo(() => {
    const q = search.toLowerCase();
    return applications
      .filter((a) => {
        if (q && !`${a.applicant_name} ${a.email} ${a.job_title} ${(a.skills || []).join(' ')}`.toLowerCase().includes(q)) return false;
        if (position !== 'all' && a.job_title !== position) return false;
        if (stage !== 'all' && a.stage !== stage) return false;
        if (band !== 'all' && !SCORE_BANDS[band](a.ai_score)) return false;
        return true;
      })
      .sort(SORTS[sort].compare);
  }, [applications, search, position, stage, band, sort]);

  const isFiltered = Boolean(search) || [position, stage, band].some((v) => v !== 'all');
  const clearFilters = () => { setSearch(''); setPosition('all'); setStage('all'); setBand('all'); };

  const postingById = useMemo(() => Object.fromEntries(postings.map(p => [p.id, p])), [postings]);
  const resolveTitle = (a) => a.job_title || postingById[a.job_posting_id]?.title || '';

  return (
    <AdminPage
      title="Candidates"
      subtitle="Review, compare and manage the candidate pipeline."
    >
      <Toolbar
        search={<SearchInput value={search} onChange={setSearch} placeholder="Search candidates..." size="sm" />}
        filters={
          <>
            <FilterSelect value={position} onChange={setPosition} label="Position"
              options={[{ value: 'all', label: 'All positions' }, ...positions.map((p) => ({ value: p, label: p }))]} />
            <FilterSelect value={stage} onChange={setStage} label="Stage" options={[
              { value: 'all', label: 'All stages' }, { value: 'applied', label: 'Applied' },
              { value: 'ai_screened', label: 'AI Screened' }, { value: 'interview', label: 'Interviewing' },
              { value: 'hired', label: 'Hired' }, { value: 'rejected', label: 'Declined' },
            ]} />
            <FilterSelect value={band} onChange={setBand} label="Score" options={[
              { value: 'all', label: 'All scores' }, { value: 'top', label: '80+ Top' },
              { value: 'strong', label: '60–79 Strong' }, { value: 'weak', label: 'Under 60' },
              { value: 'unscored', label: 'Unscored' },
            ]} />
            <FilterSelect value={sort} onChange={setSort} label="Sort"
              options={Object.entries(SORTS).map(([value, s]) => ({ value, label: s.label }))} />
          </>
        }
        meta={`${filtered.length} of ${applications.length} candidates${isFiltered ? ' · filtered' : ''}`}
      />

      {isLoading ? (
        <div className="space-y-3">
          {[...Array(5)].map((_, i) => (
            <div key={i} className="h-24 bg-white border border-[#E5E7EB] rounded-xl animate-pulse" />
          ))}
        </div>
      ) : filtered.length === 0 ? (
        <div className="text-center py-16">
          <p className="text-body-sm text-ink-3">No candidates match your filters</p>
          {isFiltered && (
            <Button size="xs" variant="outline" className="mt-3" onClick={clearFilters}>
              Clear filters
            </Button>
          )}
        </div>
      ) : (
        <div className="space-y-4">
          {filtered.map((app, idx) => (
            <CandidateCard
              key={app.id}
              application={app}
              jobTitle={resolveTitle(app)}
              rank={idx + 1}
              onAction={handleAction}
              onMessage={setMessageApp}
              onCall={setMessageApp}
              onSchedule={setScheduleApp}
              onDecline={handleDecline}
              onDelete={handleDelete}
              onHire={handleHire}
            />
          ))}
        </div>
      )}

      {/* Modals */}
      {interviewApp && (
        <AIInterviewModal open={true} onClose={() => setInterviewApp(null)} application={interviewApp} job={postings.find(p => p.id === interviewApp.job_posting_id)} />
      )}
      {scheduleApp && (
        <ScheduleInterviewModal open={true} onClose={() => setScheduleApp(null)} application={scheduleApp} />
      )}
      {messageApp && (
        <MessageCandidateModal open={true} onClose={() => setMessageApp(null)} application={messageApp} />
      )}
    </AdminPage>
  );
}