'use client';

import { useEffect, useMemo, useState } from 'react';
import { templateCatalog, type TemplateCategory } from '../emails/registry';
import { theme } from '../emails/theme';
import type { Locale } from '../emails/i18n/types';
import type { ShopSummaryPeriod } from '../emails/shop-summary';

const periods: ShopSummaryPeriod[] = [
  'daily',
  'weekly',
  'monthly',
  'quarterly',
  'yearly',
];

export default function Home() {
  const [selectedId, setSelectedId] = useState(templateCatalog[0].id);
  const [locale, setLocale] = useState<Locale>('en');
  const [period, setPeriod] = useState<ShopSummaryPeriod>('weekly');
  const [htmlContent, setHtmlContent] = useState('');
  const [loading, setLoading] = useState(true);

  const selected = useMemo(
    () => templateCatalog.find((t) => t.id === selectedId) || templateCatalog[0],
    [selectedId]
  );

  const grouped = useMemo(() => {
    return templateCatalog.reduce<Record<TemplateCategory, typeof templateCatalog>>(
      (acc, item) => {
        if (!acc[item.category]) acc[item.category] = [];
        acc[item.category].push(item);
        return acc;
      },
      {} as Record<TemplateCategory, typeof templateCatalog>
    );
  }, []);

  const loadTemplate = async (id: string, nextLocale: Locale, nextPeriod: ShopSummaryPeriod) => {
    setLoading(true);
    try {
      const params = new URLSearchParams({ locale: nextLocale });
      if (id === 'shop-summary') params.set('period', nextPeriod);
      const response = await fetch(`/api/email/${id}?${params.toString()}`);
      const html = await response.text();
      setHtmlContent(html);
    } catch (error) {
      console.error(error);
      setHtmlContent('<p>Failed to render template.</p>');
    } finally {
      setLoading(false);
    }
  };

  useEffect(() => {
    loadTemplate(selectedId, locale, period);
  }, [selectedId, locale, period]);

  const handleDownload = () => {
    const blob = new Blob([htmlContent], { type: 'text/html' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `${selectedId}-${locale}.html`;
    a.click();
    URL.revokeObjectURL(url);
  };

  return (
    <div style={page}>
      <header style={header}>
        <div>
          <p style={eyebrow}>Gishen Pharmacy</p>
          <h1 style={title}>Email Templates</h1>
          <p style={subtitle}>
            Shared previews for Ecom, Admin, and B2B · brand colors & logo from Gishen apps
          </p>
        </div>
        <div style={controls}>
          <label style={controlLabel}>
            Locale
            <select
              value={locale}
              onChange={(e) => setLocale(e.target.value as Locale)}
              style={select}
            >
              <option value="en">English</option>
              <option value="am">አማርኛ</option>
            </select>
          </label>
          {selectedId === 'shop-summary' && (
            <label style={controlLabel}>
              Period
              <select
                value={period}
                onChange={(e) => setPeriod(e.target.value as ShopSummaryPeriod)}
                style={select}
              >
                {periods.map((p) => (
                  <option key={p} value={p}>
                    {p}
                  </option>
                ))}
              </select>
            </label>
          )}
          <button type="button" onClick={handleDownload} style={downloadBtn} disabled={loading}>
            Download HTML
          </button>
        </div>
      </header>

      <div style={layout}>
        <aside style={sidebar}>
          {(Object.keys(grouped) as TemplateCategory[]).map((category) => (
            <div key={category} style={categoryBlock}>
              <h2 style={categoryTitle}>{category}</h2>
              <nav style={nav}>
                {grouped[category].map((template) => {
                  const active = template.id === selected.id;
                  return (
                    <button
                      key={template.id}
                      type="button"
                      onClick={() => setSelectedId(template.id)}
                      style={{
                        ...navButton,
                        ...(active ? activeNavButton : {}),
                      }}
                    >
                      {template.name}
                    </button>
                  );
                })}
              </nav>
            </div>
          ))}
        </aside>

        <main style={previewPane}>
          <div style={previewHeader}>
            <strong>{selected.name}</strong>
            <span style={meta}>
              /api/email/{selected.id}?locale={locale}
              {selectedId === 'shop-summary' ? `&period=${period}` : ''}
            </span>
          </div>
          {loading ? (
            <div style={loadingState}>Rendering…</div>
          ) : (
            <iframe title={selected.name} srcDoc={htmlContent} style={iframe} />
          )}
        </main>
      </div>
    </div>
  );
}

const page = {
  minHeight: '100vh',
  background: `linear-gradient(180deg, ${theme.colors.cream} 0%, #E8EDD8 100%)`,
};

const header = {
  display: 'flex',
  justifyContent: 'space-between',
  gap: '24px',
  alignItems: 'flex-end',
  padding: '28px 32px 20px',
  borderBottom: `1px solid ${theme.colors.line}`,
  background: theme.colors.surface,
  flexWrap: 'wrap' as const,
};

const eyebrow = {
  margin: 0,
  color: theme.colors.brandDeep,
  fontWeight: 700,
  letterSpacing: '0.04em',
  textTransform: 'uppercase' as const,
  fontSize: '12px',
};

const title = {
  margin: '6px 0 8px',
  fontSize: '32px',
  color: theme.colors.forest,
};

const subtitle = {
  margin: 0,
  color: theme.colors.muted,
  maxWidth: '520px',
};

const controls = {
  display: 'flex',
  gap: '12px',
  alignItems: 'flex-end',
  flexWrap: 'wrap' as const,
};

const controlLabel = {
  display: 'flex',
  flexDirection: 'column' as const,
  gap: '6px',
  fontSize: '12px',
  fontWeight: 600,
  color: theme.colors.muted,
};

const select = {
  minWidth: '140px',
  padding: '10px 12px',
  borderRadius: '8px',
  border: `1px solid ${theme.colors.line}`,
  background: theme.colors.surface,
  color: theme.colors.forest,
};

const downloadBtn = {
  padding: '11px 16px',
  borderRadius: '8px',
  border: 'none',
  background: theme.colors.forest,
  color: theme.colors.brand,
  fontWeight: 600,
  cursor: 'pointer',
};

const layout = {
  display: 'grid',
  gridTemplateColumns: '280px 1fr',
  minHeight: 'calc(100vh - 140px)',
};

const sidebar = {
  padding: '20px 16px 40px',
  borderRight: `1px solid ${theme.colors.line}`,
  background: 'rgba(255,255,255,0.7)',
  overflowY: 'auto' as const,
  maxHeight: 'calc(100vh - 140px)',
};

const categoryBlock = {
  marginBottom: '18px',
};

const categoryTitle = {
  margin: '0 0 8px',
  fontSize: '12px',
  textTransform: 'uppercase' as const,
  letterSpacing: '0.06em',
  color: theme.colors.muted,
};

const nav = {
  display: 'flex',
  flexDirection: 'column' as const,
  gap: '4px',
};

const navButton = {
  textAlign: 'left' as const,
  padding: '10px 12px',
  borderRadius: '8px',
  border: 'none',
  background: 'transparent',
  color: theme.colors.forest,
  cursor: 'pointer',
  fontSize: '14px',
};

const activeNavButton = {
  background: theme.colors.brand,
  color: theme.colors.forest,
  fontWeight: 700,
};

const previewPane = {
  padding: '20px',
};

const previewHeader = {
  display: 'flex',
  justifyContent: 'space-between',
  gap: '12px',
  alignItems: 'center',
  marginBottom: '12px',
  flexWrap: 'wrap' as const,
};

const meta = {
  fontSize: '12px',
  color: theme.colors.muted,
  fontFamily: 'ui-monospace, SFMono-Regular, Menlo, monospace',
};

const iframe = {
  width: '100%',
  height: 'calc(100vh - 220px)',
  border: `1px solid ${theme.colors.line}`,
  borderRadius: '12px',
  background: theme.colors.surface,
};

const loadingState = {
  height: 'calc(100vh - 220px)',
  display: 'grid',
  placeItems: 'center',
  border: `1px dashed ${theme.colors.line}`,
  borderRadius: '12px',
  color: theme.colors.muted,
};