package command;

import model.CrawlResult;
import model.Statistics;
import model.ResultContainer;
import strategy.CrawlStrategy;
import exception.CrawlerException;
import exception.NetworkException;
import exception.ParseException;
import view.CrawlerView;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class CrawlCommand implements Command {
    private static final Logger logger = LoggerFactory.getLogger(CrawlCommand.class);

    private final CrawlStrategy strategy;
    private final int startPage;
    private final int endPage;
    private final String outputFile;
    private final CrawlerView view;
    private final int maxRetries;
    private final int baseRetryDelay;
    private final Statistics<String> statistics;
    private final int pageDelay;

    public CrawlCommand(CrawlStrategy strategy, int startPage, int endPage,
                         String outputFile, CrawlerView view) {
        this(strategy, startPage, endPage, outputFile, view, 3, 1500, 1500);
    }

    public CrawlCommand(CrawlStrategy strategy, int startPage, int endPage,
                         String outputFile, CrawlerView view, int maxRetries, int baseRetryDelay, int pageDelay) {
        validateConstructorParams(strategy, startPage, endPage, view);
        this.strategy = strategy;
        this.startPage = startPage;
        this.endPage = endPage;
        this.outputFile = outputFile;
        this.view = view;
        this.maxRetries = maxRetries;
        this.baseRetryDelay = baseRetryDelay;
        this.pageDelay = pageDelay;
        this.statistics = new Statistics<>("CrawlCommand_" + strategy.getSiteName());
        logger.debug("CrawlCommand 初始化: site={}, pages={}-{}, pageDelay={}ms",
                strategy.getSiteName(), startPage, endPage, pageDelay);
    }

    private void validateConstructorParams(CrawlStrategy strategy, int startPage,
                                          int endPage, CrawlerView view) {
        if (strategy == null) {
            throw new IllegalArgumentException("Strategy cannot be null");
        }
        if (startPage < 1) {
            throw new IllegalArgumentException("Start page must be >= 1");
        }
        if (endPage < startPage) {
            throw new IllegalArgumentException("End page must be >= start page");
        }
        if (view == null) {
            throw new IllegalArgumentException("View cannot be null");
        }
    }

    @Override
    public List<CrawlResult> execute() throws CrawlerException {
        List<CrawlResult> allResults = new ArrayList<>();
        int consecutiveFailures = 0;
        logger.info("开始爬取: {} (页码 {} 到 {})", strategy.getSiteName(), startPage, endPage);
        view.showMessage("开始爬取: " + strategy.getSiteName());
        view.showMessage("目标: " + (endPage - startPage + 1) + " 页数据，每页间隔 " + pageDelay + "ms");
        view.showLine();

        for (int page = startPage; page <= endPage; page++) {
            List<CrawlResult> pageResults = null;
            boolean pageSuccess = false;

            for (int retry = 0; retry < maxRetries; retry++) {
                try {
                    logger.info("正在爬取第 {} 页...", page);
                    view.showMessage("正在爬取第 " + page + " 页...");
                    pageResults = strategy.crawlPage(page);

                    if (pageResults != null && !pageResults.isEmpty()) {
                        consecutiveFailures = 0;
                        statistics.increment("success_pages");
                        logger.debug("第 {} 页爬取成功，获取 {} 条数据", page, pageResults.size());
                        pageSuccess = true;
                        break;
                    }
                    logger.warn("第 {} 页返回空结果", page);
                    view.showWarning("第 " + page + " 页返回空结果");

                    if (retry < maxRetries - 1) {
                        int delay = baseRetryDelay * (int) Math.pow(2, retry);
                        view.showMessage("等待 " + delay + "ms 后重试...");
                        Thread.sleep(delay);
                    }
                } catch (ParseException e) {
                    consecutiveFailures++;
                    statistics.increment("parse_failures");
                    logger.error("第 {} 页解析失败 (尝试 {}/{}): {}",
                            page, retry + 1, maxRetries, e.getMessage());
                    view.showError("解析失败: " + e.getMessage());

                    if (retry < maxRetries - 1) {
                        try {
                            int delay = baseRetryDelay * (int) Math.pow(2, retry);
                            view.showMessage("等待 " + delay + "ms 后重试...");
                            Thread.sleep(delay);
                        } catch (InterruptedException ie) {
                            Thread.currentThread().interrupt();
                            logger.warn("爬取过程被中断");
                            throw new CrawlerException("爬取被中断", ie);
                        }
                    }
                } catch (IOException e) {
                    consecutiveFailures++;
                    statistics.increment("network_failures");
                    logger.error("【网络异常】第 {} 页网络请求失败 (尝试 {}/{}): {}",
                            page, retry + 1, maxRetries, e.getMessage());
                    view.showError("【网络异常】" + e.getMessage());

                    String exceptionType = getNetworkExceptionType(e);
                    if (exceptionType != null) {
                        logger.error("【断网检测】检测到网络中断类型: {}", exceptionType);
                        view.showError("【断网检测】" + exceptionType);
                    }

                    if (consecutiveFailures >= 2) {
                        logger.error("【断网检测】连续失败2次，判定为网络异常，立即停止爬取");
                        view.showError("【断网检测】连续失败2次，判定为网络异常，停止爬取");
                        throw new NetworkException("【断网异常】网络请求连续失败，请检查网络连接状态: " + e.getMessage(), e);
                    }

                    if (retry < maxRetries - 1) {
                        try {
                            int delay = baseRetryDelay * (int) Math.pow(2, retry);
                            view.showMessage("等待 " + delay + "ms 后重试...");
                            Thread.sleep(delay);
                        } catch (InterruptedException ie) {
                            Thread.currentThread().interrupt();
                            logger.warn("爬取过程被中断");
                            throw new NetworkException("爬取被中断", ie);
                        }
                    } else {
                        throw new NetworkException("【网络连接失败】网络请求失败，请检查网络连接: " + e.getMessage(), e);
                    }
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    logger.warn("爬取过程被中断");
                    throw new CrawlerException("爬取被中断", e);
                }
            }

            if (pageSuccess && pageResults != null) {
                allResults.addAll(pageResults);
                view.showSuccess("Page " + page + ": " + pageResults.size() + " items");
                statistics.increment("total_items", pageResults.size());
            }

            if (page < endPage && pageSuccess) {
                try {
                    logger.debug("翻页间隔等待 {}ms", pageDelay);
                    Thread.sleep(pageDelay);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    logger.warn("翻页等待被中断");
                    break;
                }
            }

            if (allResults.size() >= 200) {
                logger.info("已达到最大数据量 200 条，停止爬取");
                view.showWarning("已达到最大数据量 200 条，停止爬取");
                break;
            }
        }

        view.showLine();
        view.showMessage("爬取完成，共获取 " + allResults.size() + " 条数据");
        statistics.record("total_items", allResults.size());
        logger.info("爬取完成: {} 共获取 {} 条数据", strategy.getSiteName(), allResults.size());

        if (allResults.isEmpty()) {
            view.showError("警告: 未能获取到任何数据！");
            logger.error("未能获取到任何数据");
        }

        return allResults;
    }

    @Override
    public String getName() {
        return "CrawlCommand[" + strategy.getSiteName() + "]";
    }

    public String getOutputFile() {
        return outputFile;
    }

    public CrawlStrategy getStrategy() {
        return strategy;
    }

    public Statistics<String> getStatistics() {
        return statistics;
    }

    private String getNetworkExceptionType(IOException e) {
        Throwable cause = e.getCause();
        if (cause instanceof java.net.ConnectException) {
            return "【网络连接失败】无法连接到服务器，请检查网络连接";
        } else if (cause instanceof java.net.UnknownHostException) {
            return "【DNS解析失败】无法解析域名，请检查网络或DNS设置";
        } else if (cause instanceof java.net.NoRouteToHostException) {
            return "【路由不可达】无法到达目标主机，请检查网络连接";
        } else if (cause instanceof java.net.SocketException) {
            return "【Socket异常】网络连接异常，请检查网络状态";
        } else if (cause instanceof java.net.SocketTimeoutException) {
            return "【连接超时】网络请求超时，请检查网络稳定性";
        }
        
        String message = e.getMessage();
        if (message != null) {
            if (message.contains("Connection refused")) {
                return "【连接被拒绝】服务器拒绝连接，请检查网络或稍后重试";
            } else if (message.contains("UnknownHost")) {
                return "【域名解析失败】无法解析域名，请检查网络连接";
            } else if (message.contains("timeout")) {
                return "【请求超时】网络请求超时，请检查网络稳定性";
            } else if (message.contains("Network is unreachable")) {
                return "【网络不可达】网络连接不可用，请检查网络状态";
            } else if (message.contains("Connection reset")) {
                return "【连接重置】连接被服务器重置，请检查网络";
            }
        }
        
        return null;
    }
}