package repokit

import "encoding/xml"
import "errors"
import "fmt"
import "io"
import "io/fs"
import "os"
import "path"
import "path/filepath"
import "sort"
import "strconv"
import "strings"
import "sync"
import "syscall"
import "time"

type RpmLockMode int

const (
	RpmLockUnset RpmLockMode = iota
	RpmLockFail
	RpmLockWait
	RpmLockNone
)

type RpmRepoOptions struct {
	OutputDir string
	FilelistsExt bool
	Workers int
	ChangeLogLimit int
	UniqueMDFilenames bool
	IgnoreLock bool
	CompressionType RpmCompressionType
	LockMode RpmLockMode
	AllowMissingRepomd bool
}

type rpm_pool_task struct {
	id int64
	media_id int64
	full_path string
	filename string
	path string
}

type rpm_user_data struct {
	repo_dir_name_len int
	location_base string
	checksum_type RpmChecksumType
	change_log_limit int
	filelists_ext bool
	mutex_nevra_table sync.Mutex
	nevra_table map[string][]*RpmDuplicateLocation
	all_xml_structs *RpmXmlStructAll
}

type rpm_repo_job struct {
	user_data *rpm_user_data
	pool_task *rpm_pool_task
}


func RpmDefaultRepoOptions() RpmRepoOptions {
	var options RpmRepoOptions

	options.OutputDir = ""
	options.FilelistsExt = false
	options.Workers = RpmDefaultWorkers
	options.ChangeLogLimit = RpmDefaultChangelogLimit
	options.UniqueMDFilenames = false
	options.IgnoreLock = false
	options.CompressionType = RpmDefaultCompressionType
	options.LockMode = RpmLockFail
	options.AllowMissingRepomd = false
	return options
}

func RpmCreateRepo(dir string) error {
	var options RpmRepoOptions
	var err error

	options = RpmDefaultRepoOptions()
	err = RpmCreateRepoWithOptions(dir, options)
	if err != nil {
		return err
	}
	return nil
}

func RpmCreateRepoWithOptions(dir string, options RpmRepoOptions) error {
	var err error

	err = rpm_create_rpm_repo(dir, options)
	if err != nil {
		return err
	}
	return nil
}


func rpm_create_rpm_repo(dir string, options RpmRepoOptions) (ret_err error) {
	var in_dir string
	var in_repo string
	var out_dir string
	var out_repo string
	var tmp_out_dir string
	var out_dir_exist bool
	var err error
	var pool_tasks []*rpm_pool_task
	var total_pkg_num int
	var jobs chan *rpm_repo_job
	var results chan error
	var wg sync.WaitGroup
	var i int
	var task *rpm_pool_task
	var job_item *rpm_repo_job
	var xml_compression_suffix string
	var pri_xml_filename string
	var file_xml_filename string
	var oth_xml_filename string
	var fex_xml_filename string
	var support_filelists_ext bool
	var primary_repomd_record *RpmRepomdRecord
	var file_repomd_record *RpmRepomdRecord
	var other_repomd_record *RpmRepomdRecord
	var fex_repomd_record *RpmRepomdRecord
	var revision string
	var repomd RpmRepomd
	var repomd_path string
	var exist bool
	var old_repo string
	var failed_pkg_num int
	var result error
	var worker_count int
	var data rpm_user_data
	var compression_type RpmCompressionType
	var lock_mode RpmLockMode
	var lock_handle *os.File

	in_dir = rpm_normalize_dir_path(dir)
	in_repo = path.Join(in_dir, "repodata")
	out_dir = options.OutputDir
	out_repo = ""
	tmp_out_dir = ""

	if out_dir != "" {
		out_dir_exist, err = rpm_path_exists(out_dir)
		if err != nil {
			return fmt.Errorf("error to check if outputdir %s exists: %v", out_dir, err)
		}
		if !out_dir_exist {
			return fmt.Errorf("specified outputdir \"%s\" doesn't exist", out_dir)
		}
		out_dir = rpm_normalize_dir_path(out_dir)
		out_repo = path.Join(out_dir, "repodata")
	} else {
		out_dir = in_dir
		out_repo = in_repo
	}

	pool_tasks, err = rpm_find_rpm_files(in_dir)
	if err != nil {
		return fmt.Errorf("error to walk through packages in directory %s", in_dir)
	}
	total_pkg_num = len(pool_tasks)

	lock_mode = options.LockMode
	if lock_mode == RpmLockUnset {
		if options.IgnoreLock {
			lock_mode = RpmLockNone
		} else {
			lock_mode = RpmLockFail
		}
	}

	lock_handle, tmp_out_dir, err = rpm_lock_repo(out_dir, lock_mode)
	if err != nil {
		return fmt.Errorf("error to lock repo: %v", err)
	}
	defer func() {
		var unlock_err error

		rpm_exit_cleanup(tmp_out_dir)
		unlock_err = rpm_unlock_repo(lock_handle)
		if ret_err == nil && unlock_err != nil {
			// i can't use the return statement because it is
			// set in a deferred function.
			ret_err = fmt.Errorf("unlock repo lock failed: %w", unlock_err)
		}
	}()

	jobs = make(chan *rpm_repo_job, 100)
	results = make(chan error, 100)
	worker_count = options.Workers
	if worker_count <= 0 {
		worker_count = RpmDefaultWorkers
	}
	for i = 0; i < worker_count; i++ {
		wg.Add(1)
		go rpm_worker(jobs, results, &wg)
	}

	data.location_base = ""
	data.filelists_ext = options.FilelistsExt
	data.change_log_limit = options.ChangeLogLimit
	if data.change_log_limit <= 0 {
		data.change_log_limit = RpmDefaultChangelogLimit
	}
	data.repo_dir_name_len = len(in_dir)
	data.nevra_table = make(map[string][]*RpmDuplicateLocation)
	data.all_xml_structs = rpm_init_xml_struct_all()
	data.checksum_type = RpmDefaultChecksum

	for _, task = range pool_tasks {
		job_item = &rpm_repo_job{}
		job_item.pool_task = task
		job_item.user_data = &data
		jobs <- job_item
	}
	close(jobs)

	wg.Wait()
	close(results)

	failed_pkg_num = 0
	for result = range results {
		if result != nil {
			failed_pkg_num++
		}
	}

	compression_type = options.CompressionType
	xml_compression_suffix = CompressionSuffix(compression_type)
	pri_xml_filename = tmp_out_dir + "/primary.xml" + xml_compression_suffix
	file_xml_filename = tmp_out_dir + "/filelists.xml" + xml_compression_suffix
	oth_xml_filename = tmp_out_dir + "/other.xml" + xml_compression_suffix
	fex_xml_filename = ""
	support_filelists_ext = options.FilelistsExt
	if support_filelists_ext {
		fex_xml_filename = tmp_out_dir + "/filelists-ext.xml" + xml_compression_suffix
	}

	data.all_xml_structs.SortPackageByTaskID()
	data.all_xml_structs.SetPackageNum()

	primary_repomd_record, err = rpm_get_repomd_record(pri_xml_filename, RpmRepomdTypePrimary, &data, options.UniqueMDFilenames, compression_type)
	if err != nil {
		return err
	}
	file_repomd_record, err = rpm_get_repomd_record(file_xml_filename, RpmRepomdTypeFilelists, &data, options.UniqueMDFilenames, compression_type)
	if err != nil {
		return err
	}
	other_repomd_record, err = rpm_get_repomd_record(oth_xml_filename, RpmRepomdTypeOther, &data, options.UniqueMDFilenames, compression_type)
	if err != nil {
		return err
	}

	revision = strconv.FormatInt(time.Now().Unix(), 10)
	repomd = RpmRepomd{}
	repomd.Xmlns = RPM_XML_NS_REPOMD
	repomd.XmlnsRpm = RPM_XML_NS_RPM
	repomd.Revision = revision
	repomd.Data = []*RpmRepomdRecord{primary_repomd_record, file_repomd_record, other_repomd_record}

	if support_filelists_ext {
		fex_repomd_record, err = rpm_get_repomd_record(fex_xml_filename, RpmRepomdTypeFilelistsExt, &data, options.UniqueMDFilenames, compression_type)
		if err != nil {
			return err
		}
		repomd.Data = append(repomd.Data, fex_repomd_record)
	}

	sort.Slice(repomd.Data, func(i int, j int) bool {
		var cmp int

		cmp = rpm_repomd_record_cmp(repomd.Data[i], repomd.Data[j])
		return cmp < 0
	})

	repomd_path = filepath.Join(tmp_out_dir, "repomd.xml")
	err = rpm_write_xml(repomd, repomd_path)
	if err != nil {
		return fmt.Errorf("write %s failed: %v", repomd_path, err)
	}

	err = rpm_old_metadata_retention(out_repo, tmp_out_dir, options.AllowMissingRepomd)
	if err != nil {
		return fmt.Errorf("old metadata files retention failed: %v", err)
	}

	exist, err = rpm_path_exists(out_repo)
	if err != nil {
		return err
	}
	if exist {
		old_repo = path.Join(out_dir, rpm_append_pid_and_datetime("repodata.old", ""))
		err = os.Rename(out_repo, old_repo)
		if err != nil {
			return fmt.Errorf("rename %s to %s failed: %v", out_repo, old_repo, err)
		}
		defer rpm_exit_cleanup(old_repo)
	}
	err = os.Rename(tmp_out_dir, out_repo)
	if err != nil {
		return fmt.Errorf("rename %s to %s failed: %v", tmp_out_dir, out_repo, err)
	}

	if failed_pkg_num > 0 {
		return fmt.Errorf("finished with error: %d packages failed, %d packages succeeded", failed_pkg_num, total_pkg_num - failed_pkg_num)
	}
	return nil
}

func rpm_find_rpm_files(dir_path string) ([]*rpm_pool_task, error) {
	var rpm_files []*rpm_pool_task
	var err error
	var i int

	rpm_files = nil
	err = filepath.WalkDir(dir_path, func(walk_path string, d fs.DirEntry, walk_err error) error {
		var task *rpm_pool_task

		if walk_err != nil {
			return walk_err
		}
		if !d.IsDir() && strings.HasSuffix(d.Name(), ".rpm") {
			task = &rpm_pool_task{}
			task.full_path = walk_path
			task.filename = d.Name()
			task.path = filepath.Dir(walk_path)
			rpm_files = append(rpm_files, task)
		}
		return nil
	})

	rpm_sort_pool_tasks(rpm_files)
	for i = 0; i < len(rpm_files); i++ {
		rpm_files[i].id = int64(i)
		rpm_files[i].media_id = 0
	}
	return rpm_files, err
}

func rpm_task_cmp(a *rpm_pool_task, b *rpm_pool_task) int {
	var cmp int

	cmp = strings.Compare(a.filename, b.filename)
	if cmp != 0 {
		return cmp
	}
	return strings.Compare(a.full_path, b.full_path)
}

func rpm_sort_pool_tasks(package_tasks []*rpm_pool_task) {
	sort.Slice(package_tasks, func(i int, j int) bool {
		var cmp int

		cmp = rpm_task_cmp(package_tasks[i], package_tasks[j])
		return cmp < 0
	})
}

func rpm_old_metadata_retention(old_repo string, new_repo string, allow_missing_repomd bool) error {
	var existed bool
	var err error
	var old_repomd_path string
	var xml_file *os.File
	var xml_data []byte
	var repomd_data RpmRepomd
	var excluded_list []string
	var repomd_record *RpmRepomdRecord
	var href string
	var entries []os.DirEntry
	var entry os.DirEntry
	var src_path string
	var dst_path string

	existed, err = rpm_path_exists(old_repo)
	if err != nil {
		return err
	}
	if !existed {
		return nil
	}
	old_repomd_path = path.Join(old_repo, "repomd.xml")
	xml_file, err = os.Open(old_repomd_path)
	if err != nil {
		if allow_missing_repomd && os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("error opening file %s: %v", old_repomd_path, err)
	}
	defer xml_file.Close()

	xml_data, err = io.ReadAll(xml_file)
	if err != nil {
		return fmt.Errorf("error reading file %s: %v", old_repomd_path, err)
	}

	err = xml.Unmarshal(xml_data, &repomd_data)
	if err != nil {
		return fmt.Errorf("error unmarshaling XML to %s: %v", old_repomd_path, err)
	}

	excluded_list = []string{"repomd.xml"}
	for _, repomd_record = range repomd_data.Data {
		href = repomd_record.Location.Href
		if href == "" {
			continue
		}
		if repomd_record.Location.XMLBase != "" {
			continue
		}
		excluded_list = append(excluded_list, filepath.Base(href))
	}

	entries, err = os.ReadDir(old_repo)
	if err != nil {
		return err
	}
	for _, entry = range entries {
		if rpm_contains(excluded_list, entry.Name()) {
			continue
		}
		src_path = path.Join(old_repo, entry.Name())
		dst_path = path.Join(new_repo, entry.Name())
		if entry.IsDir() {
			err = rpm_copy_dir(src_path, dst_path)
			if err != nil {
				return err
			}
		} else {
			err = rpm_copy_file(src_path, dst_path)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func rpm_get_repomd_record(xml_compressed_file_path string, repomd_type RpmRepomdType, data *rpm_user_data, unique_md_filenames bool, compression_type RpmCompressionType) (*RpmRepomdRecord, error) {
	var xml_bytes []byte
	var err error
	var xml_data_checksum string
	var compressed_file_checksum string
	var compressed_filename string
	var base_dir string
	var old_xml_compressed_file_path string
	var stat_mod_time int64
	var stat_size int64
	var repomd_rec *RpmRepomdRecord

	if repomd_type == RpmRepomdTypePrimary {
		xml_bytes, err = rpm_dump_xml(data.all_xml_structs.RpmPrimaryXMLData)
	} else if repomd_type == RpmRepomdTypeFilelists {
		xml_bytes, err = rpm_dump_xml(data.all_xml_structs.RpmFilelistsXMLData)
	} else if repomd_type == RpmRepomdTypeOther {
		xml_bytes, err = rpm_dump_xml(data.all_xml_structs.RpmOtherXMLData)
	} else if repomd_type == RpmRepomdTypeFilelistsExt {
		xml_bytes, err = rpm_dump_xml(data.all_xml_structs.RpmFilelistsExtXMLData)
	} else {
		return nil, fmt.Errorf("invalid repomd type %s", repomd_type)
	}
	if err != nil {
		return nil, err
	}

	xml_data_checksum, err = rpm_checksum_bytes(xml_bytes, RpmDefaultRepomdChecksum)
	if err != nil {
		return nil, err
	}
	err = rpm_compress_xml(xml_bytes, xml_compressed_file_path, compression_type)
	if err != nil {
		return nil, err
	}
	compressed_file_checksum, err = rpm_checksum_file(xml_compressed_file_path, RpmDefaultRepomdChecksum)
	if err != nil {
		return nil, err
	}

	compressed_filename = filepath.Base(xml_compressed_file_path)
	if unique_md_filenames {
		base_dir = filepath.Dir(xml_compressed_file_path)
		compressed_filename = fmt.Sprintf("%s-%s", compressed_file_checksum, compressed_filename)
		old_xml_compressed_file_path = xml_compressed_file_path
		xml_compressed_file_path = path.Join(base_dir, compressed_filename)
		err = os.Rename(old_xml_compressed_file_path, xml_compressed_file_path)
		if err != nil {
			return nil, fmt.Errorf("rename %s to %s failed: %v", old_xml_compressed_file_path, xml_compressed_file_path, err)
		}
	}

	stat_mod_time, stat_size, err = rpm_stat_file(xml_compressed_file_path)
	if err != nil {
		return nil, err
	}

	repomd_rec = &RpmRepomdRecord{}
	repomd_rec.Type = string(repomd_type)
	repomd_rec.OpenChecksum = RpmChecksum{Type: RpmChecksumName(RpmDefaultRepomdChecksum), Value: xml_data_checksum}
	repomd_rec.OpenSize = int64(len(xml_bytes))
	repomd_rec.Checksum = RpmChecksum{Type: RpmChecksumName(RpmDefaultRepomdChecksum), Value: compressed_file_checksum}
	repomd_rec.Size = stat_size
	repomd_rec.Location = RpmLocation{Href: RpmLocationHrefPrefix + compressed_filename}
	repomd_rec.Timestamp = stat_mod_time

	return repomd_rec, nil
}

func rpm_exit_cleanup(lock_dir string) {
	_ = os.RemoveAll(lock_dir)
}

func rpm_lock_repo(repo_dir string, lock_mode RpmLockMode) (*os.File, string, error) {
	var lock_handle *os.File
	var tmp_repodata_dir string
	var err error
	var flock_flags int

	if lock_mode != RpmLockNone {
		lock_handle, err = os.Open(repo_dir)
		if err != nil {
			return nil, "", fmt.Errorf("cannot open repo dir %s for locking: %w", repo_dir, err)
		}

		flock_flags = syscall.LOCK_EX
		if lock_mode == RpmLockFail {
			flock_flags = flock_flags | syscall.LOCK_NB
		} else if lock_mode != RpmLockWait {
			lock_handle.Close()
			return nil, "", fmt.Errorf("unknown lock mode")
		}

		err = syscall.Flock(int(lock_handle.Fd()), flock_flags)
		if err != nil {
			lock_handle.Close()
			if errors.Is(err, syscall.EWOULDBLOCK) || errors.Is(err, syscall.EAGAIN) {
				return nil, "", fmt.Errorf("repo dir lock exists: %s", repo_dir)
			}
			return nil, "", fmt.Errorf("cannot lock repo dir %s: %w", repo_dir, err)
		}
	}

	tmp_repodata_dir = filepath.Join(repo_dir, rpm_append_pid_and_datetime(".repodata", ""))
	err = os.Mkdir(tmp_repodata_dir, os.ModePerm)
	if err != nil {
		rpm_unlock_repo(lock_handle)
		return nil, "", fmt.Errorf("cannot create %s: %w", tmp_repodata_dir, err)
	}

	return lock_handle, tmp_repodata_dir, nil
}

func rpm_unlock_repo(lock_handle *os.File) error {
	var err error

	if lock_handle == nil {
		// in case rpm_lock_repo() didn't really lock a repo or did fail.
		return nil
	}

	err = syscall.Flock(int(lock_handle.Fd()), syscall.LOCK_UN)
	if err != nil {
		lock_handle.Close()
		return err
	}

	return lock_handle.Close()
}

func rpm_append_pid_and_datetime(prefix string, suffix string) string {
	var pid int
	var current_time time.Time
	var timestamp string
	var microseconds int
	var result string

	pid = os.Getpid()
	current_time = time.Now()
	timestamp = current_time.Format("20060102150405")
	microseconds = current_time.Nanosecond() / 1000

	result = fmt.Sprintf("%s.%d.%s.%d", prefix, pid, timestamp, microseconds)
	if suffix != "" {
		result = fmt.Sprintf("%s.%s", result, suffix)
	}
	return result
}

func rpm_worker(jobs <-chan *rpm_repo_job, results chan<- error, wg *sync.WaitGroup) {
	var job_item *rpm_repo_job
	var udata *rpm_user_data
	var task *rpm_pool_task
	var location_href string
	var location_base string
	var pkg *RpmPackage
	var err error

	defer wg.Done()
	for job_item = range jobs {
		udata = job_item.user_data
		task = job_item.pool_task
		location_href = task.full_path[udata.repo_dir_name_len:]
		location_base = udata.location_base
		pkg, err = rpm_load_rpm(task.full_path, udata.checksum_type, location_href, location_base, udata.change_log_limit)
		if err != nil {
			results <- err
			return
		}

		err = rpm_xml_dump(udata, task, pkg, udata.filelists_ext)
		if err != nil {
			results <- err
			return
		}
	}
}

func rpm_xml_dump(udata *rpm_user_data, task *rpm_pool_task, pkg *RpmPackage, is_filelists_ext bool) error {
	var task_id int64

	if rpm_package_contains_forbidden_control_chars(pkg) {
		return fmt.Errorf("forbidden control chars found (ASCII values <32 except 9, 10 and 13)")
	}
	task_id = task.id
	udata.all_xml_structs.MutexPrimary.Lock()
	udata.all_xml_structs.RpmPrimaryXMLData.PackageList = append(udata.all_xml_structs.RpmPrimaryXMLData.PackageList, rpm_get_primary_package(pkg, task_id))
	udata.all_xml_structs.MutexPrimary.Unlock()
	udata.all_xml_structs.MutexFilelists.Lock()
	udata.all_xml_structs.RpmFilelistsXMLData.PackageList = append(udata.all_xml_structs.RpmFilelistsXMLData.PackageList, rpm_get_filelists_package(pkg, false, task_id))
	udata.all_xml_structs.MutexFilelists.Unlock()
	udata.all_xml_structs.MutexOtherData.Lock()
	udata.all_xml_structs.RpmOtherXMLData.PackageList = append(udata.all_xml_structs.RpmOtherXMLData.PackageList, rpm_get_other_package(pkg, task_id))
	udata.all_xml_structs.MutexOtherData.Unlock()
	if is_filelists_ext {
		udata.all_xml_structs.MutexFilelistsExt.Lock()
		udata.all_xml_structs.RpmFilelistsExtXMLData.PackageList = append(udata.all_xml_structs.RpmFilelistsExtXMLData.PackageList, rpm_get_filelists_package(pkg, true, task_id))
		udata.all_xml_structs.MutexFilelistsExt.Unlock()
	}
	return nil
}