package com.goldenchart.service;

import com.goldenchart.dto.MobileAppReleaseInfoDto;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.nio.file.*;
import java.time.Instant;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.Comparator;
import java.util.Optional;
import java.util.stream.Stream;

@Service
@Slf4j
public class MobileAppReleaseService {

    private static final String DEFAULT_APK_NAME = "goldenchart-android.apk";
    private static final DateTimeFormatter DT_FMT =
            DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm").withZone(ZoneId.of("Asia/Seoul"));

    @Value("${goldenchart.mobile-app.release-dir:data/mobile-releases}")
    private String releaseDir;

    @Value("${goldenchart.mobile-app.version:}")
    private String configuredVersion;

    @Value("${goldenchart.mobile-app.public-base-url:}")
    private String configuredPublicBaseUrl;

    @Value("${goldenchart.mobile-app.ios-testflight-url:}")
    private String iosTestFlightUrl;

    public MobileAppReleaseInfoDto getInfo(String requestBaseUrl) {
        String publicBaseUrl = resolvePublicBaseUrl(requestBaseUrl);
        boolean iosAvailable = iosTestFlightUrl != null && !iosTestFlightUrl.isBlank();
        Optional<Path> apk = resolveApkPath();
        if (apk.isEmpty()) {
            return MobileAppReleaseInfoDto.builder()
                    .available(false)
                    .installPageUrl(buildInstallPageUrl(publicBaseUrl))
                    .iosAvailable(iosAvailable)
                    .iosTestFlightUrl(iosAvailable ? iosTestFlightUrl.trim() : null)
                    .build();
        }
        Path file = apk.get();
        try {
            long size = Files.size(file);
            Instant updated = Files.getLastModifiedTime(file).toInstant();
            String base = normalizeBase(publicBaseUrl);
            String downloadUrl = base + "/api/mobile-app/download/android";
            String version = resolveApkVersion(file);
            return MobileAppReleaseInfoDto.builder()
                    .available(true)
                    .fileName(file.getFileName().toString())
                    .version(version)
                    .sizeBytes(size)
                    .updatedAt(DT_FMT.format(updated))
                    .downloadUrl(downloadUrl)
                    .installPageUrl(buildInstallPageUrl(publicBaseUrl))
                    .iosAvailable(iosAvailable)
                    .iosTestFlightUrl(iosAvailable ? iosTestFlightUrl.trim() : null)
                    .build();
        } catch (IOException e) {
            log.warn("[mobile-app] stat failed: {}", e.getMessage());
            return MobileAppReleaseInfoDto.builder()
                    .available(false)
                    .installPageUrl(buildInstallPageUrl(publicBaseUrl))
                    .iosAvailable(iosAvailable)
                    .iosTestFlightUrl(iosAvailable ? iosTestFlightUrl.trim() : null)
                    .build();
        }
    }

    public ResponseEntity<Resource> downloadAndroid() {
        Optional<Path> apk = resolveApkPath();
        if (apk.isEmpty()) {
            return ResponseEntity.notFound().build();
        }
        Path file = apk.get();
        FileSystemResource resource = new FileSystemResource(file);
        String filename = file.getFileName().toString();
        return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + filename + "\"")
                .contentType(MediaType.parseMediaType("application/vnd.android.package-archive"))
                .body(resource);
    }

    private Optional<Path> resolveApkPath() {
        Path dir = Paths.get(releaseDir).toAbsolutePath().normalize();
        if (!Files.isDirectory(dir)) {
            log.debug("[mobile-app] release dir missing: {}", dir);
            return Optional.empty();
        }
        Path preferred = dir.resolve(DEFAULT_APK_NAME);
        if (Files.isRegularFile(preferred)) {
            return Optional.of(preferred);
        }
        try (Stream<Path> stream = Files.list(dir)) {
            return stream
                    .filter(p -> Files.isRegularFile(p) && p.getFileName().toString().toLowerCase().endsWith(".apk"))
                    .max(Comparator.comparing(p -> {
                        try {
                            return Files.getLastModifiedTime(p).toMillis();
                        } catch (IOException e) {
                            return 0L;
                        }
                    }));
        } catch (IOException e) {
            log.warn("[mobile-app] list dir failed: {}", e.getMessage());
            return Optional.empty();
        }
    }

    private static String buildInstallPageUrl(String publicBaseUrl) {
        return normalizeBase(publicBaseUrl) + "/install.html";
    }

    private String resolvePublicBaseUrl(String requestBaseUrl) {
        if (configuredPublicBaseUrl != null && !configuredPublicBaseUrl.isBlank()) {
            return configuredPublicBaseUrl.trim();
        }
        if (requestBaseUrl != null && !requestBaseUrl.isBlank()) {
            return requestBaseUrl.trim();
        }
        return "http://exdev.co.kr";
    }

    private static String normalizeBase(String publicBaseUrl) {
        if (publicBaseUrl == null || publicBaseUrl.isBlank()) {
            return "http://exdev.co.kr";
        }
        return publicBaseUrl.replaceAll("/+$", "");
    }

    /** APK와 함께 기록된 .version sidecar → .env configuredVersion → 파일 수정 시각 */
    private String resolveApkVersion(Path apkFile) {
        String apkName = apkFile.getFileName().toString();
        Path sidecar = apkFile.getParent().resolve(
                apkName.replaceAll("(?i)\\.apk$", "") + ".version");
        try {
            if (Files.isRegularFile(sidecar)) {
                String fromFile = Files.readString(sidecar).trim();
                if (!fromFile.isBlank()) {
                    return fromFile;
                }
            }
        } catch (IOException e) {
            log.warn("[mobile-app] read version sidecar failed: {}", e.getMessage());
        }
        if (configuredVersion != null && !configuredVersion.isBlank()) {
            return configuredVersion.trim();
        }
        try {
            return DT_FMT.format(Files.getLastModifiedTime(apkFile).toInstant());
        } catch (IOException e) {
            return "unknown";
        }
    }
}