package md2html;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.*;

public class Md2Html {

    public static void main(String[] args) {
        if (args == null || args.length < 2) {
            return;
        }

        try (
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(new FileInputStream(args[0]), StandardCharsets.UTF_8));
                BufferedWriter writer = new BufferedWriter(
                        new OutputStreamWriter(new FileOutputStream(args[1]), StandardCharsets.UTF_8))
        ) {
            List<String> blocks = readBlocks(reader);
            for (String block : blocks) {
                writer.write(convertBlock(block));
                writer.newLine();
            }
        } catch (IOException e) {
            // по условию обычно можно игнорировать или просто завершить
        }
    }

    private static List<String> readBlocks(BufferedReader reader) throws IOException {
        List<String> blocks = new ArrayList<>();
        StringBuilder current = new StringBuilder();
        String line;

        while ((line = reader.readLine()) != null) {
            if (line.isEmpty()) {
                if (!current.isEmpty()) {
                    blocks.add(current.toString());
                    current.setLength(0);
                }
            } else {
                if (!current.isEmpty()) {
                    current.append('\n');
                }
                current.append(line);
            }
        }

        if (!current.isEmpty()) {
            blocks.add(current.toString());
        }

        return blocks;
    }

    private static String convertBlock(String block) {
        int level = countHeaderLevel(block);

        if (level > 0) {
            String content = block.substring(level + 1);
            return "<h" + level + ">" + parseInline(content) + "</h" + level + ">";
        } else {
            return "<p>" + parseInline(block) + "</p>";
        }
    }

    private static int countHeaderLevel(String block) {
        int i = 0;
        while (i < block.length() && block.charAt(i) == '#') {
            i++;
        }
        if (i > 0 && i <= 6 && i < block.length() && block.charAt(i) == ' ') {
            return i;
        }
        return 0;
    }

    private static String parseInline(String text) {
        StringBuilder result = new StringBuilder();
        Deque<String> stack = new ArrayDeque<>();

        Map<String, String> tags = Map.of(
                "*", "em",
                "_", "em",
                "**", "strong",
                "__", "strong",
                "--", "s",
                "`", "code"
        );

        for (int i = 0; i < text.length(); ) {

            // escape
            if (text.charAt(i) == '\\' && i + 1 < text.length()) {
                result.append(escapeHtml(text.charAt(i + 1)));
                i += 2;
                continue;
            }

            // check double markers first
            if (i + 1 < text.length()) {
                String two = text.substring(i, i + 2);
                if (tags.containsKey(two)) {
                    if (!stack.isEmpty() && stack.peek().equals(two)) {
                        result.append("</").append(tags.get(two)).append(">");
                        stack.pop();
                    } else {
                        result.append("<").append(tags.get(two)).append(">");
                        stack.push(two);
                    }
                    i += 2;
                    continue;
                }
            }

            // single markers
            String one = String.valueOf(text.charAt(i));
            if (tags.containsKey(one)) {
                if (!stack.isEmpty() && stack.peek().equals(one)) {
                    result.append("</").append(tags.get(one)).append(">");
                    stack.pop();
                } else {
                    result.append("<").append(tags.get(one)).append(">");
                    stack.push(one);
                }
                i++;
                continue;
            }

            // normal char
            result.append(escapeHtml(text.charAt(i)));
            i++;
        }

        return result.toString();
    }

    private static String escapeHtml(char c) {
        return switch (c) {
            case '<' -> "&lt;";
            case '>' -> "&gt;";
            case '&' -> "&amp;";
            default -> String.valueOf(c);
        };
    }
}