'use client';

import { useState, useCallback } from 'react';
import { Loader2, Mail, Copy, Check } from 'lucide-react';

import { Button } from '@/components/ui/button';
import {
  Sheet,
  SheetContent,
  SheetHeader,
  SheetTitle,
  SheetDescription,
} from '@/components/ui/sheet';
import { useFeatureFlag } from '@/hooks/use-feature-flag';
import { apiFetch } from '@/lib/api/client';

// ─── Types ────────────────────────────────────────────────────────────────────

interface EmailDraftButtonProps {
  interestId: string;
  clientId: string;
  context?: 'follow_up' | 'introduction' | 'stage_update' | 'general';
  additionalInstructions?: string;
}

interface DraftResult {
  subject: string;
  body: string;
  generatedAt: string;
}

// ─── Polling helper ───────────────────────────────────────────────────────────

const POLL_INTERVAL_MS = 1500;
const POLL_MAX_ATTEMPTS = 20; // 30 s total

async function pollDraftResult(jobId: string): Promise<DraftResult> {
  for (let attempt = 0; attempt < POLL_MAX_ATTEMPTS; attempt++) {
    await new Promise((resolve) => setTimeout(resolve, POLL_INTERVAL_MS));

    const res = await apiFetch<{ status: string; data?: DraftResult }>(
      `/api/v1/ai/email-draft/${jobId}`,
    );

    if (res.status === 'complete' && res.data) {
      return res.data;
    }
  }
  throw new Error('Email draft generation timed out. Please try again.');
}

// ─── Component ────────────────────────────────────────────────────────────────

export function EmailDraftButton({
  interestId,
  clientId,
  context = 'follow_up',
  additionalInstructions,
}: EmailDraftButtonProps) {
  const featureEnabled = useFeatureFlag('ai_email_drafts');

  const [isLoading, setIsLoading] = useState(false);
  const [sheetOpen, setSheetOpen] = useState(false);
  const [draft, setDraft] = useState<DraftResult | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [copied, setCopied] = useState(false);

  const handleGenerateDraft = useCallback(async () => {
    setIsLoading(true);
    setError(null);
    setDraft(null);

    try {
      const { jobId } = await apiFetch<{ jobId: string }>('/api/v1/ai/email-draft', {
        method: 'POST',
        body: { interestId, clientId, context, additionalInstructions },
      });

      const result = await pollDraftResult(jobId);
      setDraft(result);
      setSheetOpen(true);
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Failed to generate draft');
    } finally {
      setIsLoading(false);
    }
  }, [interestId, clientId, context, additionalInstructions]);

  const handleCopy = useCallback(async () => {
    if (!draft) return;
    const text = `Subject: ${draft.subject}\n\n${draft.body}`;
    await navigator.clipboard.writeText(text);
    setCopied(true);
    setTimeout(() => setCopied(false), 2000);
  }, [draft]);

  if (!featureEnabled) return null;

  return (
    <>
      <Button variant="outline" size="sm" onClick={handleGenerateDraft} disabled={isLoading}>
        {isLoading ? (
          <>
            <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" />
            Generating...
          </>
        ) : (
          <>
            <Mail className="mr-1.5 h-3.5 w-3.5" />
            Draft Email
          </>
        )}
      </Button>

      {error && <p className="text-xs text-destructive mt-1">{error}</p>}

      <Sheet open={sheetOpen} onOpenChange={setSheetOpen}>
        <SheetContent side="right" className="w-full max-w-lg flex flex-col">
          <SheetHeader>
            <SheetTitle>Generated Email Draft</SheetTitle>
            <SheetDescription>Review and edit the draft before sending.</SheetDescription>
          </SheetHeader>

          {draft && (
            <div className="flex-1 overflow-y-auto mt-4 space-y-4">
              {/* Subject */}
              <div>
                <label className="text-xs font-medium text-muted-foreground uppercase tracking-wide">
                  Subject
                </label>
                <p
                  contentEditable
                  suppressContentEditableWarning
                  className="mt-1 text-sm font-medium border rounded-md px-3 py-2 focus:outline-hidden focus:ring-2 focus:ring-ring"
                >
                  {draft.subject}
                </p>
              </div>

              {/* Body */}
              <div className="flex-1">
                <label className="text-xs font-medium text-muted-foreground uppercase tracking-wide">
                  Body
                </label>
                <pre
                  contentEditable
                  suppressContentEditableWarning
                  className="mt-1 text-sm whitespace-pre-wrap font-sans border rounded-md px-3 py-2 min-h-[300px] focus:outline-hidden focus:ring-2 focus:ring-ring"
                >
                  {draft.body}
                </pre>
              </div>

              {/* Actions */}
              <div className="flex gap-2 pt-2 border-t">
                <Button variant="outline" size="sm" onClick={handleCopy}>
                  {copied ? (
                    <>
                      <Check className="mr-1.5 h-3.5 w-3.5 text-green-600" />
                      Copied
                    </>
                  ) : (
                    <>
                      <Copy className="mr-1.5 h-3.5 w-3.5" />
                      Copy to clipboard
                    </>
                  )}
                </Button>
                <Button
                  variant="outline"
                  size="sm"
                  onClick={handleGenerateDraft}
                  disabled={isLoading}
                >
                  {isLoading ? (
                    <>
                      <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" />
                      Regenerating...
                    </>
                  ) : (
                    'Regenerate'
                  )}
                </Button>
              </div>
            </div>
          )}
        </SheetContent>
      </Sheet>
    </>
  );
}