package com.guo.learningprogresstracker.service.impl;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.guo.learningprogresstracker.enums.ReviewMindMapFileFormatEnum;
import org.springframework.web.multipart.MultipartFile;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import javax.xml.parsers.DocumentBuilderFactory;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

class MindMapFileParser {

    private final ObjectMapper objectMapper;

    MindMapFileParser(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    ParseResult parse(MultipartFile file, ReviewMindMapFileFormatEnum format) throws IOException {
        byte[] bytes = file.getBytes();
        Map<String, Object> root = switch (format) {
            case XMIND -> parseXMind(bytes);
            case MARKDOWN -> parseMarkdown(new String(bytes, StandardCharsets.UTF_8), format);
            case OPML -> parseOutlineXml(bytes, "text", format);
            case FREEMIND -> parseOutlineXml(bytes, "TEXT", format);
            case TEXT -> parseMarkdown(new String(bytes, StandardCharsets.UTF_8), format);
        };
        String title = String.valueOf(root.getOrDefault("title", file.getOriginalFilename()));
        String outline = toOutline(root);
        int nodeCount = countNodes(root);
        int depth = maxDepth(root);
        String summary = "共解析 " + nodeCount + " 个节点，最大层级 " + depth + "。";
        return new ParseResult(title, format.getCode(), objectMapper.writeValueAsString(root), outline, summary);
    }

    private Map<String, Object> parseXMind(byte[] bytes) throws IOException {
        byte[] contentJson = null;
        byte[] contentXml = null;
        try (ZipInputStream zipInputStream = new ZipInputStream(new ByteArrayInputStream(bytes))) {
            ZipEntry entry;
            while ((entry = zipInputStream.getNextEntry()) != null) {
                if ("content.json".equals(entry.getName())) {
                    contentJson = zipInputStream.readAllBytes();
                } else if ("content.xml".equals(entry.getName())) {
                    contentXml = zipInputStream.readAllBytes();
                }
            }
        }
        if (contentJson != null) {
            return parseXMindJson(contentJson);
        }
        if (contentXml != null) {
            return parseXMindXml(contentXml);
        }
        throw new IOException("未找到 XMind 内容文件");
    }

    private Map<String, Object> parseXMindJson(byte[] bytes) throws IOException {
        JsonNode sheets = objectMapper.readTree(bytes);
        JsonNode sheet = sheets.isArray() && !sheets.isEmpty() ? sheets.get(0) : sheets;
        JsonNode rootTopic = sheet.path("rootTopic");
        Map<String, Object> root = node(rootTopic.path("title").asText("XMind 导图"));
        root.put("sourceFormat", ReviewMindMapFileFormatEnum.XMIND.getCode());
        root.put("nodes", parseXMindTopicChildren(rootTopic));
        return root;
    }

    private List<Map<String, Object>> parseXMindTopicChildren(JsonNode topic) {
        List<Map<String, Object>> result = new ArrayList<>();
        JsonNode attached = topic.path("children").path("attached");
        if (!attached.isArray()) {
            return result;
        }
        for (JsonNode child : attached) {
            Map<String, Object> item = node(child.path("title").asText("未命名节点"));
            item.put("children", parseXMindTopicChildren(child));
            result.add(item);
        }
        return result;
    }

    private Map<String, Object> parseXMindXml(byte[] bytes) throws IOException {
        Document document = xmlDocument(bytes);
        Element sheet = firstElementByName(document.getDocumentElement(), "sheet");
        Element topic = sheet == null ? firstElementByName(document.getDocumentElement(), "topic") : firstElementByName(sheet, "topic");
        if (topic == null) {
            throw new IOException("未找到 XMind 根节点");
        }
        Map<String, Object> root = parseTopicElement(topic);
        root.put("sourceFormat", ReviewMindMapFileFormatEnum.XMIND.getCode());
        root.put("nodes", root.remove("children"));
        return root;
    }

    private Map<String, Object> parseMarkdown(String content, ReviewMindMapFileFormatEnum format) {
        Map<String, Object> root = node("导图大纲");
        root.put("sourceFormat", format.getCode());
        List<Map<String, Object>> roots = new ArrayList<>();
        root.put("nodes", roots);

        ArrayDeque<StackItem> stack = new ArrayDeque<>();
        stack.push(new StackItem(0, roots));
        for (String rawLine : content.split("\\R")) {
            String line = rawLine.stripTrailing();
            if (line.isBlank()) {
                continue;
            }
            int level = markdownLevel(line);
            String title = markdownTitle(line);
            Map<String, Object> item = node(title);
            while (stack.peek().level >= level) {
                stack.pop();
            }
            stack.peek().children.add(item);
            @SuppressWarnings("unchecked")
            List<Map<String, Object>> children = (List<Map<String, Object>>) item.get("children");
            stack.push(new StackItem(level, children));
        }
        if (!roots.isEmpty()) {
            root.put("title", roots.get(0).get("title"));
        }
        return root;
    }

    private Map<String, Object> parseOutlineXml(byte[] bytes, String titleAttribute, ReviewMindMapFileFormatEnum format) throws IOException {
        Document document = xmlDocument(bytes);
        Element rootElement = document.getDocumentElement();
        Element first = firstElementByName(rootElement, "outline");
        if (first == null) {
            first = firstElementByName(rootElement, "node");
            titleAttribute = "TEXT";
        }
        if (first == null) {
            throw new IOException("未找到导图节点");
        }
        Map<String, Object> root = parseOutlineElement(first, titleAttribute);
        root.put("sourceFormat", format.getCode());
        root.put("nodes", root.remove("children"));
        return root;
    }

    private Document xmlDocument(byte[] bytes) throws IOException {
        try {
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
            factory.setFeature("http://xml.org/sax/features/external-general-entities", false);
            factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
            factory.setNamespaceAware(false);
            return factory.newDocumentBuilder().parse(new ByteArrayInputStream(bytes));
        } catch (Exception e) {
            throw new IOException("导图 XML 解析失败", e);
        }
    }

    private Map<String, Object> parseTopicElement(Element element) {
        Map<String, Object> item = node(textOfFirstChild(element, "title", "未命名节点"));
        item.put("children", childTopicElements(element).stream()
                .map(this::parseTopicElement)
                .toList());
        return item;
    }

    private Map<String, Object> parseOutlineElement(Element element, String titleAttribute) {
        String title = element.getAttribute(titleAttribute);
        if (title == null || title.isBlank()) {
            title = element.getAttribute("text");
        }
        if (title == null || title.isBlank()) {
            title = "未命名节点";
        }
        Map<String, Object> item = node(title);
        List<Map<String, Object>> children = directChildElements(element).stream()
                .filter(child -> "outline".equalsIgnoreCase(child.getTagName()) || "node".equalsIgnoreCase(child.getTagName()))
                .map(child -> parseOutlineElement(child, titleAttribute))
                .toList();
        item.put("children", children);
        return item;
    }

    private Map<String, Object> node(String title) {
        Map<String, Object> node = new LinkedHashMap<>();
        node.put("title", title);
        node.put("notes", "");
        node.put("children", new ArrayList<Map<String, Object>>());
        return node;
    }

    private int markdownLevel(String line) {
        String trimmed = line.stripLeading();
        if (trimmed.startsWith("#")) {
            int count = 0;
            while (count < trimmed.length() && trimmed.charAt(count) == '#') {
                count++;
            }
            return count;
        }
        int indent = line.length() - trimmed.length();
        return 1 + indent / 2;
    }

    private String markdownTitle(String line) {
        return line.strip()
                .replaceFirst("^#{1,6}\\s*", "")
                .replaceFirst("^[-*+]\\s*", "")
                .replaceFirst("^\\d+\\.\\s*", "");
    }

    private List<Element> childTopicElements(Element element) {
        return directChildElements(element).stream()
                .flatMap(child -> {
                    if ("topic".equalsIgnoreCase(child.getTagName())) {
                        return List.of(child).stream();
                    }
                    return childTopicElements(child).stream();
                })
                .toList();
    }

    private Element firstElementByName(Element element, String name) {
        if (name.equalsIgnoreCase(element.getTagName())) {
            return element;
        }
        NodeList nodes = element.getChildNodes();
        for (int i = 0; i < nodes.getLength(); i++) {
            if (nodes.item(i) instanceof Element child) {
                Element found = firstElementByName(child, name);
                if (found != null) {
                    return found;
                }
            }
        }
        return null;
    }

    private List<Element> directChildElements(Element element) {
        List<Element> result = new ArrayList<>();
        NodeList nodes = element.getChildNodes();
        for (int i = 0; i < nodes.getLength(); i++) {
            if (nodes.item(i) instanceof Element child) {
                result.add(child);
            }
        }
        return result;
    }

    private String textOfFirstChild(Element element, String name, String fallback) {
        for (Element child : directChildElements(element)) {
            if (name.equalsIgnoreCase(child.getTagName())) {
                return child.getTextContent();
            }
        }
        return fallback;
    }

    private String toOutline(Map<String, Object> root) {
        StringBuilder builder = new StringBuilder();
        appendOutline(builder, root, 0);
        return builder.toString();
    }

    @SuppressWarnings("unchecked")
    private void appendOutline(StringBuilder builder, Map<String, Object> node, int level) {
        builder.append("  ".repeat(level)).append("- ").append(node.get("title")).append('\n');
        Object children = node.get(level == 0 && node.containsKey("nodes") ? "nodes" : "children");
        if (children instanceof List<?> list) {
            for (Object child : list) {
                appendOutline(builder, (Map<String, Object>) child, level + 1);
            }
        }
    }

    @SuppressWarnings("unchecked")
    private int countNodes(Map<String, Object> node) {
        int count = 1;
        Object children = node.get(node.containsKey("nodes") ? "nodes" : "children");
        if (children instanceof List<?> list) {
            for (Object child : list) {
                count += countNodes((Map<String, Object>) child);
            }
        }
        return count;
    }

    @SuppressWarnings("unchecked")
    private int maxDepth(Map<String, Object> node) {
        Object children = node.get(node.containsKey("nodes") ? "nodes" : "children");
        if (!(children instanceof List<?> list) || list.isEmpty()) {
            return 1;
        }
        int max = 1;
        for (Object child : list) {
            max = Math.max(max, 1 + maxDepth((Map<String, Object>) child));
        }
        return max;
    }

    record ParseResult(String title, String fileFormat, String parsedContent, String outline, String summary) {
    }

    private record StackItem(int level, List<Map<String, Object>> children) {
    }
}