import { json } from '@sveltejs/kit';
import type { RequestHandler } from './$types';
import { sendGmail } from '$lib/google/gmail/server.js';
import QRCode from 'qrcode';

interface Participant {
	id: string;
	name: string;
	surname: string;
	email: string;
}

interface EmailResult {
	participant: Participant;
	success: boolean;
	error?: string;
}

/**
 * Replaces template variables in a string with participant data
 * Currently supports {name} and {surname} placeholders
 */
function replaceTemplateVariables(template: string, participant: Participant): string {
	return template
		.replace(/{name}/gi, participant.name || '')
		.replace(/{surname}/gi, participant.surname || '');
}

async function generateQRCode(participantId: string): Promise<string> {
	const qrCodeBase64 = await QRCode.toDataURL(participantId, {
		type: 'image/png',
		margin: 2,
		scale: 8
	});

	// Remove the data URL prefix to get just the base64 string
	return qrCodeBase64.replace(/^data:image\/png;base64,/, '');
}

async function sendEmailToParticipant(
	participant: Participant,
	subject: string,
	text: string,
	eventId: string,
	refreshToken: string,
	supabase: any
): Promise<EmailResult> {
	try {
		const qrCodeBase64Data = await generateQRCode(participant.id);

		// Replace template variables in subject and body
		const personalizedSubject = replaceTemplateVariables(subject, participant);
		const personalizedText = replaceTemplateVariables(text, participant);

		// Send email with QR code
		await sendGmail(refreshToken, {
			to: participant.email,
			subject: personalizedSubject,
			text: personalizedText,
			qr_code: qrCodeBase64Data
		});


		// Call the participant_emailed RPC function
		try {
			await supabase.rpc('participant_emailed', {
				p_participant_id: participant.id
			});
		} catch (dbError) {
			console.error('Failed to call participant_emailed RPC:', dbError);
			// Don't fail the entire operation if the RPC call fails
		}

		return {
			participant: participant,
			success: true
		};
	} catch (error) {
		console.error('Failed to send email to participant:', participant.email, error);
		return {
			participant: participant,
			success: false,
			error: error instanceof Error ? error.message : 'Unknown error'
		};
	}
}

function validateRequest(participants: unknown, subject: unknown, text: unknown, eventId: unknown, refreshToken: unknown) {
	if (!participants || !Array.isArray(participants)) {
		return { error: 'Invalid participants array', status: 400 };
	}

	if (!subject || !text) {
		return { error: 'Subject and text are required', status: 400 };
	}

	if (!eventId) {
		return { error: 'Event ID is required', status: 400 };
	}

	if (!refreshToken || typeof refreshToken !== 'string') {
		return { error: 'Refresh token is required', status: 401 };
	}

	return null;
}

export const POST: RequestHandler = async ({ request, locals }) => {
	try {
		const { participants, subject, text, eventId, refreshToken } = await request.json();
		
		const validationError = validateRequest(participants, subject, text, eventId, refreshToken);
		if (validationError) {
			return json({ error: validationError.error }, { status: validationError.status });
		}

		const results: EmailResult[] = [];
		let successCount = 0;
		let errorCount = 0;

		// Send emails to each participant
		for (const participant of participants as Participant[]) {
			const result = await sendEmailToParticipant(
				participant,
				subject as string,
				text as string,
				eventId as string,
				refreshToken as string,
				locals.supabase
			);

			results.push(result);
			
			if (result.success) {
				successCount++;
			} else {
				errorCount++;
			}
		}

		return json({
			success: true,
			results,
			summary: {
				total: participants.length,
				success: successCount,
				errors: errorCount
			}
		});
	} catch (error) {
		console.error('Email sending error:', error);
		
		// Handle specific Gmail API errors
		if (error instanceof Error) {
			if (error.message.includes('Invalid Credentials') || error.message.includes('unauthorized')) {
				return json({ error: 'Invalid or expired Google credentials' }, { status: 401 });
			}
			if (error.message.includes('quota')) {
				return json({ error: 'Gmail API quota exceeded' }, { status: 429 });
			}
			if (error.message.includes('rate')) {
				return json({ error: 'Rate limit exceeded' }, { status: 429 });
			}
		}
		
		return json({ error: 'Failed to send emails' }, { status: 500 });
	}
};