package at.procon.ted.camel;

import at.procon.ted.config.TedProcessorProperties;
import at.procon.ted.service.attachment.AttachmentExtractor;
import at.procon.ted.service.attachment.AttachmentProcessingService;
import jakarta.mail.BodyPart;
import jakarta.mail.Message;
import jakarta.mail.Multipart;
import jakarta.mail.Part;
import jakarta.mail.Session;
import jakarta.mail.internet.MimeMessage;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.apache.camel.Exchange;
import org.apache.camel.LoggingLevel;
import org.apache.camel.builder.RouteBuilder;
import org.jsoup.Jsoup;
import org.springframework.stereotype.Component;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

/**
 * Apache Camel route for IMAP mail processing.
 *
 * Features:
 * - IMAP connection with SSL/TLS to mail server
 * - MIME message decoding
 * - Asynchronous attachment processing with idempotency
 * - PDF text extraction
 * - ZIP file extraction with recursive processing
 * - HTML to plain text conversion
 *
 * @author Martin.Schweitzer@procon.co.at and claude.ai
 */
@Component
@RequiredArgsConstructor
@Slf4j
public class MailRoute extends RouteBuilder {

    private static final String ROUTE_ID_IMAP = "mail-imap-consumer";
    private static final String ROUTE_ID_MIME_FILE = "mail-mime-file-consumer";
    private static final String ROUTE_ID_MIME = "mail-mime-decoder";
    private static final String ROUTE_ID_ATTACHMENT = "mail-attachment-processor";
    private static final String ROUTE_ID_ATTACHMENT_ASYNC = "mail-attachment-async";

    private final TedProcessorProperties properties;
    private final AttachmentProcessingService attachmentProcessingService;

    @Override
    public void configure() throws Exception {
        TedProcessorProperties.MailProperties mail = properties.getMail();

        if (!mail.isEnabled()) {
            log.info("Mail processing is disabled, skipping route configuration");
            return;
        }

        log.info("Configuring mail routes (host={}, port={}, ssl={}, user={})",
                mail.getHost(), mail.getPort(), mail.isSsl(), mail.getUsername());

        // Ensure attachment output directory exists
        File attachmentDir = new File(mail.getAttachmentOutputDirectory());
        if (!attachmentDir.exists()) {
            attachmentDir.mkdirs();
            log.info("Created attachment output directory: {}", attachmentDir.getAbsolutePath());
        }

        // Error handler for mail processing
        errorHandler(deadLetterChannel("direct:mail-error-handler")
                .maximumRedeliveries(3)
                .redeliveryDelay(5000)
                .retryAttemptedLogLevel(LoggingLevel.WARN)
                .logStackTrace(true));

        // Mail error handler route
        from("direct:mail-error-handler")
                .routeId("mail-error-handler")
                .process(exchange -> {
                    Exception exception = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class);
                    String subject = exchange.getIn().getHeader("mailSubject", String.class);
                    if (exception != null) {
                        log.error("Mail processing error for subject '{}': {}", subject, exception.getMessage(), exception);
                    }
                })
                .log(LoggingLevel.ERROR, "Mail processing failed: ${exception.message}");

        // IMAP consumer route
        from(buildImapUri())
                .routeId(ROUTE_ID_IMAP)
                .log(LoggingLevel.INFO, "Received email: ${header.subject} from ${header.from}")
                .to("direct:mime");

        // MIME file consumer route - reads .eml files from directory
        if (mail.isMimeInputEnabled()) {
            configureMimeFileConsumer(mail);
        }

        // MIME decoder route - decodes the email and extracts content/attachments
        from("direct:mime")
                .routeId(ROUTE_ID_MIME)
                .process(exchange -> {
                    Message mailMessage = exchange.getIn().getBody(Message.class);

                    if (mailMessage == null) {
                        log.warn("Received null mail message, skipping");
                        return;
                    }

                    String subject = mailMessage.getSubject();
                    String from = mailMessage.getFrom() != null && mailMessage.getFrom().length > 0
                            ? mailMessage.getFrom()[0].toString() : "unknown";

                    log.info("Processing MIME message: subject='{}', from='{}'", subject, from);

                    // Store mail metadata in headers
                    exchange.getIn().setHeader("mailSubject", subject);
                    exchange.getIn().setHeader("mailFrom", from);
                    exchange.getIn().setHeader("mailReceivedDate", mailMessage.getReceivedDate());

                    // Process the content
                    List<AttachmentInfo> attachments = new ArrayList<>();
                    StringBuilder textContent = new StringBuilder();
                    StringBuilder htmlContent = new StringBuilder();

                    processMessageContent(mailMessage, textContent, htmlContent, attachments);

                    // Convert HTML to plain text if we have HTML but no plain text
                    String finalTextContent;
                    if (textContent.length() == 0 && htmlContent.length() > 0) {
                        finalTextContent = convertHtmlToText(htmlContent.toString());
                        log.debug("Converted HTML mail to plain text ({} chars)", finalTextContent.length());
                    } else {
                        finalTextContent = textContent.toString();
                    }

                    // Store results
                    exchange.getIn().setHeader("mailTextContent", finalTextContent);
                    exchange.getIn().setHeader("mailHtmlContent", htmlContent.toString());
                    exchange.getIn().setHeader("mailAttachments", attachments);
                    exchange.getIn().setHeader("mailAttachmentCount", attachments.size());

                    log.info("MIME decoded: subject='{}', textLength={}, htmlLength={}, attachments={}",
                            subject, finalTextContent.length(), htmlContent.length(), attachments.size());
                })
                // Queue attachments for async processing
                .choice()
                    .when(simple("${header.mailAttachmentCount} > 0"))
                        .log(LoggingLevel.INFO, "Queueing ${header.mailAttachmentCount} attachments for async processing")
                    .otherwise()
                        .log(LoggingLevel.DEBUG, "No attachments in email: ${header.mailSubject}")
                .end()
                // Process attachments asynchronously via SEDA
                .filter(simple("${header.mailAttachmentCount} > 0"))
                    .split(header("mailAttachments"))
                        .to("seda:attachment-async?waitForTaskToComplete=Never&size=500")
                    .end()
                .end()
                .log(LoggingLevel.INFO, "Mail processing completed: ${header.mailSubject}");

        // Async attachment processor route via SEDA
        from("seda:attachment-async?concurrentConsumers=2&size=500")
                .routeId(ROUTE_ID_ATTACHMENT_ASYNC)
                .to("direct:attachment");

        // Attachment processor route - handles individual attachments with idempotency
        from("direct:attachment")
                .routeId(ROUTE_ID_ATTACHMENT)
                .process(exchange -> {
                    AttachmentInfo attachment = exchange.getIn().getBody(AttachmentInfo.class);

                    if (attachment == null) {
                        log.warn("Received null attachment info, skipping");
                        return;
                    }

                    String mailSubject = exchange.getIn().getHeader("mailSubject", String.class);
                    String mailFrom = exchange.getIn().getHeader("mailFrom", String.class);
                    String parentHash = exchange.getIn().getHeader("parentHash", String.class);

                    log.info("Processing attachment: '{}' ({} bytes, type={}) from email '{}'",
                            attachment.getFilename(), attachment.getSize(),
                            attachment.getContentType(), mailSubject);

                    // Process attachment with idempotency check
                    AttachmentProcessingService.ProcessingResult result = attachmentProcessingService.processAttachment(
                            attachment.getData(),
                            attachment.getFilename(),
                            attachment.getContentType(),
                            mailSubject,
                            mailFrom,
                            parentHash
                    );

                    if (result.isDuplicate()) {
                        log.info("Attachment is duplicate, skipping: '{}'", attachment.getFilename());
                        exchange.setProperty("isDuplicate", true);
                        return;
                    }

                    if (!result.isSuccess()) {
                        log.warn("Attachment processing failed: '{}' - {}",
                                attachment.getFilename(), result.errorMessage());
                        return;
                    }

                    // Store result in exchange
                    exchange.getIn().setHeader("attachmentId", result.attachment().getId());
                    exchange.getIn().setHeader("attachmentHash", result.attachment().getContentHash());
                    exchange.getIn().setHeader("extractedText",
                            result.attachment().getExtractedText() != null
                                    ? result.attachment().getExtractedText().length() + " chars"
                                    : "none");

                    // Queue child attachments (from ZIP) for recursive processing
                    if (result.hasChildren()) {
                        log.info("Queueing {} child attachments from ZIP '{}'",
                                result.childAttachments().size(), attachment.getFilename());

                        for (AttachmentExtractor.ChildAttachment child : result.childAttachments()) {
                            // Create AttachmentInfo for child and send to SEDA queue
                            AttachmentInfo childInfo = new AttachmentInfo(
                                    child.filename(),
                                    child.contentType(),
                                    child.data(),
                                    child.data().length
                            );

                            // Send to SEDA for async processing with parent hash
                            getContext().createProducerTemplate().sendBodyAndHeaders(
                                    "seda:attachment-async?waitForTaskToComplete=Never",
                                    childInfo,
                                    java.util.Map.of(
                                            "mailSubject", mailSubject != null ? mailSubject : "",
                                            "mailFrom", mailFrom != null ? mailFrom : "",
                                            "parentHash", result.attachment().getContentHash(),
                                            "pathInArchive", child.pathInArchive()
                                    )
                            );
                        }
                    }
                })
                .choice()
                    .when(exchangeProperty("isDuplicate").isEqualTo(true))
                        .log(LoggingLevel.DEBUG, "Skipped duplicate attachment")
                    .otherwise()
                        .log(LoggingLevel.INFO, "Attachment processed: ${header.attachmentId}, extracted=${header.extractedText}")
                .end();
    }

    /**
     * Configure the MIME file consumer route.
     */
    private void configureMimeFileConsumer(TedProcessorProperties.MailProperties mail) throws Exception {
        // Ensure MIME input directory exists
        File mimeInputDir = new File(mail.getMimeInputDirectory());
        if (!mimeInputDir.exists()) {
            mimeInputDir.mkdirs();
            log.info("Created MIME input directory: {}", mimeInputDir.getAbsolutePath());
        }

        String mimeFileUri = buildMimeFileUri(mail);
        log.info("Configuring MIME file consumer: {}", mimeFileUri);

        // MIME file consumer - reads .eml files and sends to direct:mime
        from(mimeFileUri)
                .routeId(ROUTE_ID_MIME_FILE)
                .log(LoggingLevel.INFO, "Reading MIME file: ${header.CamelFileName}")
                .process(exchange -> {
                    // Read file content as bytes
                    byte[] fileContent = exchange.getIn().getBody(byte[].class);
                    String filename = exchange.getIn().getHeader(Exchange.FILE_NAME, String.class);

                    if (fileContent == null || fileContent.length == 0) {
                        log.warn("Empty MIME file: {}", filename);
                        throw new RuntimeException("Empty MIME file: " + filename);
                    }

                    log.debug("Parsing MIME file: {} ({} bytes)", filename, fileContent.length);

                    // Parse the file as a MimeMessage
                    Session session = Session.getDefaultInstance(new Properties());
                    try (ByteArrayInputStream bais = new ByteArrayInputStream(fileContent)) {
                        MimeMessage mimeMessage = new MimeMessage(session, bais);

                        // Set the parsed message as body for direct:mime
                        exchange.getIn().setBody(mimeMessage);

                        log.info("Parsed MIME file: {} -> subject='{}'",
                                filename, mimeMessage.getSubject());
                    }
                })
                .to("direct:mime")
                .log(LoggingLevel.INFO, "MIME file processed successfully: ${header.CamelFileName}");
    }

    /**
     * Build the file URI for MIME file consumer.
     */
    private String buildMimeFileUri(TedProcessorProperties.MailProperties mail) {
        String directory = mail.getMimeInputDirectory().replace("\\", "/");

        StringBuilder uri = new StringBuilder("file:");
        uri.append(directory);
        uri.append("?");
        // File pattern
        uri.append("include=").append(mail.getMimeInputPattern());
        // Polling interval
        uri.append("&delay=").append(mail.getMimeInputPollInterval());
        // Move to .processed after successful processing
        uri.append("&move=.processed");
        // Move to .error on failure
        uri.append("&moveFailed=.error");
        // Read lock to prevent processing incomplete files
        uri.append("&readLock=changed");
        uri.append("&readLockCheckInterval=1000");
        uri.append("&readLockTimeout=30000");
        // Sort by name for consistent ordering
        uri.append("&sortBy=file:name");
        // Don't process hidden files
        uri.append("&exclude=^\\..*");
        // Recursive scanning disabled by default
        uri.append("&recursive=false");

        return uri.toString();
    }

    /**
     * Build the IMAP URI for the mail consumer.
     */
    private String buildImapUri() {
        TedProcessorProperties.MailProperties mail = properties.getMail();

        StringBuilder uri = new StringBuilder();
        uri.append(mail.isSsl() ? "imaps://" : "imap://");
        uri.append(mail.getHost());
        uri.append(":").append(mail.getPort());
        uri.append("?username=").append(encodeUriComponent(mail.getUsername()));
        uri.append("&password=").append(encodeUriComponent(mail.getPassword()));
        uri.append("&folderName=").append(mail.getFolderName());
        uri.append("&delete=").append(mail.isDelete());
        // peek=false means messages will be marked as SEEN after fetch
        // peek=true means messages will NOT be marked as SEEN (peek only)
        uri.append("&peek=").append(!mail.isSeen());
        uri.append("&unseen=").append(mail.isUnseen());
        uri.append("&delay=").append(mail.getDelay());
        uri.append("&maxMessagesPerPoll=").append(mail.getMaxMessagesPerPoll());
        // Connection settings
        uri.append("&connectionTimeout=30000");
        uri.append("&fetchSize=-1");  // Fetch entire message
        uri.append("&debugMode=false");

        log.info("IMAP URI configured (password hidden): {}://{}:{}?username={}&folderName={}",
                mail.isSsl() ? "imaps" : "imap", mail.getHost(), mail.getPort(),
                mail.getUsername(), mail.getFolderName());

        return uri.toString();
    }

    /**
     * URL-encode a URI component.
     */
    private String encodeUriComponent(String value) {
        if (value == null) return "";
        try {
            return java.net.URLEncoder.encode(value, StandardCharsets.UTF_8);
        } catch (Exception e) {
            return value;
        }
    }

    /**
     * Recursively process message content to extract text, HTML, and attachments.
     */
    private void processMessageContent(Part part, StringBuilder textContent,
            StringBuilder htmlContent, List<AttachmentInfo> attachments) throws Exception {

        String contentType = part.getContentType().toLowerCase();
        String disposition = part.getDisposition();

        // Check if this is an attachment
        if (disposition != null && (disposition.equalsIgnoreCase(Part.ATTACHMENT)
                || disposition.equalsIgnoreCase(Part.INLINE))) {
            extractAttachment(part, attachments);
            return;
        }

        Object content = part.getContent();

        if (content instanceof Multipart multipart) {
            // Process each part of the multipart message
            for (int i = 0; i < multipart.getCount(); i++) {
                BodyPart bodyPart = multipart.getBodyPart(i);
                processMessageContent(bodyPart, textContent, htmlContent, attachments);
            }
        } else if (contentType.contains("text/plain")) {
            // Plain text content
            String text = content.toString();
            textContent.append(text);
        } else if (contentType.contains("text/html")) {
            // HTML content
            String html = content.toString();
            htmlContent.append(html);
        } else if (part.getFileName() != null) {
            // Has filename - treat as attachment
            extractAttachment(part, attachments);
        }
    }

    /**
     * Extract attachment data from a message part.
     */
    private void extractAttachment(Part part, List<AttachmentInfo> attachments) throws Exception {
        String filename = part.getFileName();
        if (filename == null) {
            filename = "unnamed_attachment";
        }

        // Decode filename if necessary (might be MIME-encoded)
        try {
            filename = jakarta.mail.internet.MimeUtility.decodeText(filename);
        } catch (Exception e) {
            log.debug("Could not decode filename: {}", filename);
        }

        String contentType = part.getContentType();

        // Read attachment data
        byte[] data;
        try (InputStream is = part.getInputStream()) {
            data = is.readAllBytes();
        }

        AttachmentInfo info = new AttachmentInfo(filename, contentType, data, data.length);
        attachments.add(info);

        log.debug("Extracted attachment: '{}' ({} bytes, type={})", filename, data.length, contentType);
    }

    /**
     * Convert HTML content to plain text using JSoup.
     */
    private String convertHtmlToText(String html) {
        if (html == null || html.isBlank()) {
            return "";
        }

        try {
            // Parse HTML and extract text
            org.jsoup.nodes.Document doc = Jsoup.parse(html);

            // Remove script and style elements
            doc.select("script, style").remove();

            // Get text with whitespace preservation
            String text = doc.text();

            // Clean up excessive whitespace
            text = text.replaceAll("\\s+", " ").trim();

            return text;
        } catch (Exception e) {
            log.warn("Failed to convert HTML to text: {}", e.getMessage());
            // Fallback: strip HTML tags with regex
            return html.replaceAll("<[^>]+>", " ").replaceAll("\\s+", " ").trim();
        }
    }

    /**
     * DTO for attachment information.
     */
    @lombok.Data
    @lombok.AllArgsConstructor
    public static class AttachmentInfo {
        private String filename;
        private String contentType;
        private byte[] data;
        private int size;
    }
}