package xiaozhi.modules.parent.catalog;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import lombok.extern.slf4j.Slf4j;

/**
 * 课文 MP3 数量以 xiaozhi-server 磁盘目录为准。索引接口失败时返回 null，调用方再用清单兜底。
 */
@Slf4j
public final class LessonClipIndex {
    private static final ObjectMapper MAPPER = new ObjectMapper();
    private static final Pattern LESSON = Pattern.compile("^(l[1-6])\\.(\\d{3})$", Pattern.CASE_INSENSITIVE);
    private static final HttpClient CLIENT = HttpClient.newBuilder()
            .connectTimeout(Duration.ofSeconds(2))
            .build();

    private LessonClipIndex() {
    }

    public static List<String> fetch(String baseUrl, String scene, String lessonId, String language) {
        String base = baseUrl == null ? "" : baseUrl.replaceAll("/+$", "");
        Matcher lesson = LESSON.matcher(lessonId == null ? "" : lessonId.trim());
        if (base.isEmpty() || !lesson.matches()) {
            return null;
        }
        String level = lesson.group(1).toLowerCase();
        String story = lesson.group(2);
        try {
            if ("shadowing".equals(scene)) {
                String lang = "cn".equalsIgnoreCase(language) ? "cn" : "en";
                return oneFolder(base, "shadowing", level, story, lang);
            }
            if ("extensive".equals(scene)) {
                List<String> cn = oneFolder(base, "repeater", level, story, "cn");
                List<String> en = oneFolder(base, "repeater", level, story, "en");
                if (cn == null || en == null) {
                    return null;
                }
                List<String> both = new ArrayList<>(cn.size() + en.size());
                both.addAll(cn);
                both.addAll(en);
                return both;
            }
        } catch (Exception ex) {
            log.warn("lesson clip index failed: {}", ex.toString());
            return null;
        }
        return null;
    }

    private static List<String> oneFolder(String base, String kind, String level, String story, String lang)
            throws Exception {
        String url = base + "/index/" + kind + "/" + level + "/" + story + "/" + lang;
        HttpRequest request = HttpRequest.newBuilder(URI.create(url))
                .timeout(Duration.ofSeconds(3))
                .GET()
                .build();
        HttpResponse<String> response = CLIENT.send(request, HttpResponse.BodyHandlers.ofString());
        if (response.statusCode() != 200) {
            return null;
        }
        JsonNode root = MAPPER.readTree(response.body());
        if (root == null || !root.path("present").asBoolean(false)) {
            return null;
        }
        List<String> files = new ArrayList<>();
        JsonNode raw = root.get("files");
        if (raw != null && raw.isArray()) {
            for (JsonNode item : raw) {
                if (item.isTextual()) {
                    files.add(item.asText());
                }
            }
        }
        return files;
    }
}