package service

import (
	"crypto/sha256"
	"encoding/hex"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"gorm.io/gorm"

	"nl-pms-api/internal/commonservice"
	"nl-pms-api/internal/config"
	"nl-pms-api/internal/model"
)

var versionRe = regexp.MustCompile(`^\d+\.\d+\.\d+([-.][A-Za-z0-9.]+)?$`)

// ReleaseService 客户端发版。
type ReleaseService struct {
	DB  *gorm.DB
	Cfg *config.Config
}

type LatestRelease struct {
	Version   string `json:"version"`
	Channel   string `json:"channel"`
	SHA256    string `json:"sha256"`
	SizeBytes int64  `json:"sizeBytes"`
	Changelog string `json:"changelog"`
	CreatedAt string `json:"createdAt"`
}

// List 发版列表（新→旧）。
func (s *ReleaseService) List(channel string) ([]model.AppRelease, error) {
	channel = normalizeChannel(channel)
	var rows []model.AppRelease
	q := s.DB.Order("id DESC").Limit(50)
	if channel != "" {
		q = q.Where("channel = ?", channel)
	}
	if err := q.Find(&rows).Error; err != nil {
		return nil, commonservice.Internal("QUERY_FAILED")
	}
	if rows == nil {
		rows = []model.AppRelease{}
	}
	return rows, nil
}

// Latest 当前最新版元数据。
func (s *ReleaseService) Latest(channel string) (*LatestRelease, error) {
	channel = normalizeChannel(channel)
	var row model.AppRelease
	err := s.DB.Where("channel = ? AND is_latest = 1", channel).Order("id DESC").First(&row).Error
	if err == gorm.ErrRecordNotFound {
		return nil, commonservice.NotFound("NO_RELEASE")
	}
	if err != nil {
		return nil, commonservice.Internal("QUERY_FAILED")
	}
	return &LatestRelease{
		Version:   row.Version,
		Channel:   row.Channel,
		SHA256:    row.SHA256,
		SizeBytes: row.SizeBytes,
		Changelog: row.Changelog,
		CreatedAt: row.CreatedAt,
	}, nil
}

// Upload 保存安装包并写入元数据（默认不标 latest，需 Publish）。
func (s *ReleaseService) Upload(version, channel, changelog string, r io.Reader, size int64) (*model.AppRelease, error) {
	version = strings.TrimSpace(version)
	channel = normalizeChannel(channel)
	changelog = strings.TrimSpace(changelog)
	if !versionRe.MatchString(version) {
		return nil, commonservice.BadRequest("VERSION_INVALID")
	}
	if size <= 0 {
		return nil, commonservice.BadRequest("EMPTY_FILE")
	}
	if size > s.Cfg.MaxReleaseBytes() {
		return nil, commonservice.BadRequest("FILE_TOO_LARGE")
	}
	var n int64
	s.DB.Model(&model.AppRelease{}).Where("version = ? AND channel = ?", version, channel).Count(&n)
	if n > 0 {
		return nil, commonservice.Conflict("VERSION_EXISTS")
	}

	dir := filepath.Join(s.Cfg.StorageDir, "releases", channel)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	relName := filepath.ToSlash(filepath.Join("releases", channel, version+"-installer.exe"))
	abs := filepath.Join(s.Cfg.StorageDir, filepath.FromSlash(relName))
	f, err := os.Create(abs)
	if err != nil {
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	defer f.Close()

	h := sha256.New()
	written, err := io.Copy(io.MultiWriter(f, h), io.LimitReader(r, s.Cfg.MaxReleaseBytes()+1))
	if err != nil {
		_ = os.Remove(abs)
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	if written > s.Cfg.MaxReleaseBytes() {
		_ = os.Remove(abs)
		return nil, commonservice.BadRequest("FILE_TOO_LARGE")
	}
	sum := hex.EncodeToString(h.Sum(nil))
	row := model.AppRelease{
		Version:   version,
		Channel:   channel,
		Filename:  relName,
		SHA256:    sum,
		SizeBytes: written,
		Changelog: changelog,
		CreatedAt: commonservice.NowRFC(),
		IsLatest:  0,
	}
	if err := s.DB.Create(&row).Error; err != nil {
		_ = os.Remove(abs)
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	return &row, nil
}

// Publish 将指定发版标为该渠道最新。
func (s *ReleaseService) Publish(id int64) (*model.AppRelease, error) {
	var row model.AppRelease
	if err := s.DB.First(&row, id).Error; err != nil {
		return nil, commonservice.NotFound("NOT_FOUND")
	}
	tx := s.DB.Begin()
	if err := tx.Model(&model.AppRelease{}).Where("channel = ?", row.Channel).Update("is_latest", 0).Error; err != nil {
		tx.Rollback()
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	if err := tx.Model(&row).Update("is_latest", 1).Error; err != nil {
		tx.Rollback()
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	if err := tx.Commit().Error; err != nil {
		return nil, commonservice.Internal("SAVE_FAILED")
	}
	row.IsLatest = 1
	return &row, nil
}

// OpenFile 打开发版文件供下载。
func (s *ReleaseService) OpenFile(version, channel string) (*model.AppRelease, *os.File, error) {
	version = strings.TrimSpace(version)
	channel = normalizeChannel(channel)
	var row model.AppRelease
	if err := s.DB.Where("version = ? AND channel = ?", version, channel).First(&row).Error; err != nil {
		return nil, nil, commonservice.NotFound("NOT_FOUND")
	}
	abs := filepath.Join(s.Cfg.StorageDir, filepath.FromSlash(row.Filename))
	f, err := os.Open(abs)
	if err != nil {
		return nil, nil, commonservice.NotFound("NOT_FOUND")
	}
	return &row, f, nil
}

func normalizeChannel(ch string) string {
	ch = strings.TrimSpace(strings.ToLower(ch))
	if ch == "" {
		return "stable"
	}
	return ch
}