package com.dsh.account.service;

import com.dsh.account.model.ImageCaptchaVo;
import com.dsh.account.util.RedisUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import javax.imageio.ImageIO;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.SecureRandom;
import java.util.Base64;
import java.util.Locale;
import java.util.UUID;

/**
 * 短信发送前置图形验证码服务。
 */
@Service
public class ImageCaptchaService {

    private static final String CAPTCHA_KEY_PREFIX = "security:sms:image-captcha:";
    private static final String CREATE_LIMIT_KEY_PREFIX = "security:sms:image-captcha:create:";
    private static final char[] CAPTCHA_CHARS = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ".toCharArray();
    private static final int CAPTCHA_LENGTH = 4;
    private static final int IMAGE_WIDTH = 120;
    private static final int IMAGE_HEIGHT = 44;

    private final SecureRandom secureRandom = new SecureRandom();

    @Autowired
    private RedisUtil redisUtil;

    @Value("${security.sms.image-captcha-expire-seconds:120}")
    private int expireSeconds;

    @Value("${security.sms.image-captcha-max-per-minute:10}")
    private int maxPerMinute;

    /**
     * 创建与手机号、短信用途绑定的图形验证码。
     *
     * @return 达到生成频率上限时返回null
     */
    public ImageCaptchaVo create(String phone, Integer type, String clientIp) throws IOException {
        if (!redisUtil.tryAcquireFixedWindow(
                CREATE_LIMIT_KEY_PREFIX + clientIp,
                maxPerMinute,
                60)) {
            return null;
        }

        String captchaId = UUID.randomUUID().toString().replace("-", "");
        String captchaCode = randomCode();
        redisUtil.setStrValue(
                CAPTCHA_KEY_PREFIX + captchaId,
                captchaValue(phone, type, captchaCode),
                expireSeconds
        );
        return new ImageCaptchaVo(captchaId, renderImage(captchaCode), expireSeconds);
    }

    /**
     * 原子校验并删除验证码。无论输入是否正确，每个验证码都只能提交一次。
     */
    public boolean verifyAndConsume(String captchaId, String captchaCode, String phone, Integer type) {
        if (captchaId == null || captchaCode == null) {
            return false;
        }

        String normalizedId = captchaId.trim().toLowerCase(Locale.ROOT);
        String normalizedCode = captchaCode.trim().toUpperCase(Locale.ROOT);
        if (!normalizedId.matches("[0-9a-f]{32}") || !normalizedCode.matches("[0-9A-Z]{4}")) {
            return false;
        }

        return redisUtil.consumeIfEquals(
                CAPTCHA_KEY_PREFIX + normalizedId,
                captchaValue(phone, type, normalizedCode)
        );
    }

    private String randomCode() {
        StringBuilder code = new StringBuilder(CAPTCHA_LENGTH);
        for (int i = 0; i < CAPTCHA_LENGTH; i++) {
            code.append(CAPTCHA_CHARS[secureRandom.nextInt(CAPTCHA_CHARS.length)]);
        }
        return code.toString();
    }

    private String renderImage(String code) throws IOException {
        BufferedImage image = new BufferedImage(IMAGE_WIDTH, IMAGE_HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = image.createGraphics();
        try {
            graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            graphics.setColor(new Color(245, 247, 250));
            graphics.fillRect(0, 0, IMAGE_WIDTH, IMAGE_HEIGHT);
            drawNoise(graphics);
            drawCode(graphics, code);
        } finally {
            graphics.dispose();
        }

        try (ByteArrayOutputStream output = new ByteArrayOutputStream()) {
            ImageIO.write(image, "png", output);
            return "data:image/png;base64," + Base64.getEncoder().encodeToString(output.toByteArray());
        }
    }

    private void drawNoise(Graphics2D graphics) {
        for (int i = 0; i < 7; i++) {
            graphics.setColor(randomColor(150, 210));
            graphics.drawLine(
                    secureRandom.nextInt(IMAGE_WIDTH),
                    secureRandom.nextInt(IMAGE_HEIGHT),
                    secureRandom.nextInt(IMAGE_WIDTH),
                    secureRandom.nextInt(IMAGE_HEIGHT)
            );
        }
        for (int i = 0; i < 45; i++) {
            graphics.setColor(randomColor(120, 220));
            graphics.fillOval(secureRandom.nextInt(IMAGE_WIDTH), secureRandom.nextInt(IMAGE_HEIGHT), 2, 2);
        }
    }

    private void drawCode(Graphics2D graphics, String code) {
        graphics.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 27));
        for (int i = 0; i < code.length(); i++) {
            Graphics2D characterGraphics = (Graphics2D) graphics.create();
            try {
                characterGraphics.setColor(randomColor(25, 115));
                double angle = (secureRandom.nextDouble() - 0.5D) * 0.45D;
                int x = 12 + i * 26;
                int y = 31 + secureRandom.nextInt(6) - 3;
                characterGraphics.setTransform(AffineTransform.getRotateInstance(angle, x + 9, y - 10));
                characterGraphics.drawString(String.valueOf(code.charAt(i)), x, y);
            } finally {
                characterGraphics.dispose();
            }
        }
    }

    private Color randomColor(int min, int max) {
        int bound = max - min + 1;
        return new Color(
                min + secureRandom.nextInt(bound),
                min + secureRandom.nextInt(bound),
                min + secureRandom.nextInt(bound)
        );
    }

    private String captchaValue(String phone, Integer type, String code) {
        return phone + ":" + type + ":" + code;
    }
}