// Package filter controls the filtering of files
package filter

import (
	"context"
	"crypto/md5"
	"encoding/binary"
	"errors"
	"fmt"
	"math/rand/v2"
	"path"
	"slices"
	"strconv"
	"strings"
	"time"

	"github.com/rclone/rclone/fs"
	"golang.org/x/sync/errgroup"
	"golang.org/x/text/unicode/norm"
)

// This is the globally active filter
//
// This is accessed through GetConfig and AddConfig
var globalConfig = mustNewFilter(nil)

// OptionsInfo describes the Options in use
var OptionsInfo = fs.Options{{
	Name:    "delete_excluded",
	Default: false,
	Help:    "Delete files on dest excluded from sync",
	Groups:  "Filter",
}, {
	Name:    "exclude_if_present",
	Default: []string{},
	Help:    "Exclude directories if filename is present",
	Groups:  "Filter",
}, {
	Name:    "files_from",
	Default: []string{},
	Help:    "Read list of source-file names from file (use - to read from stdin)",
	Groups:  "Filter",
}, {
	Name:    "files_from_raw",
	Default: []string{},
	Help:    "Read list of source-file names from file without any processing of lines (use - to read from stdin)",
	Groups:  "Filter",
}, {
	Name:    "min_age",
	Default: fs.DurationOff,
	Help:    "Only transfer files older than this in s or suffix ms|s|m|h|d|w|M|y",
	Groups:  "Filter",
}, {
	Name:    "max_age",
	Default: fs.DurationOff,
	Help:    "Only transfer files younger than this in s or suffix ms|s|m|h|d|w|M|y",
	Groups:  "Filter",
}, {
	Name:    "min_size",
	Default: fs.SizeSuffix(-1),
	Help:    "Only transfer files bigger than this in KiB or suffix B|K|M|G|T|P",
	Groups:  "Filter",
}, {
	Name:    "max_size",
	Default: fs.SizeSuffix(-1),
	Help:    "Only transfer files smaller than this in KiB or suffix B|K|M|G|T|P",
	Groups:  "Filter",
}, {
	Name:    "ignore_case",
	Default: false,
	Help:    "Ignore case in filters (case insensitive)",
	Groups:  "Filter",
}, {
	Name:    "hash_filter",
	Default: "",
	Help:    "Partition filenames by hash k/n or randomly @/n",
	Groups:  "Filter",
}, {
	Name:     "filter",
	Default:  []string{},
	ShortOpt: "f",
	Help:     "Add a file filtering rule",
	Groups:   "Filter",
}, {
	Name:    "filter_from",
	Default: []string{},
	Help:    "Read file filtering patterns from a file (use - to read from stdin)",
	Groups:  "Filter",
}, {
	Name:    "exclude",
	Default: []string{},
	Help:    "Exclude files matching pattern",
	Groups:  "Filter",
}, {
	Name:    "exclude_from",
	Default: []string{},
	Help:    "Read file exclude patterns from file (use - to read from stdin)",
	Groups:  "Filter",
}, {
	Name:    "include",
	Default: []string{},
	Help:    "Include files matching pattern",
	Groups:  "Filter",
}, {
	Name:    "include_from",
	Default: []string{},
	Help:    "Read file include patterns from file (use - to read from stdin)",
	Groups:  "Filter",
}, {
	Name:    "metadata_filter",
	Default: []string{},
	Help:    "Add a metadata filtering rule",
	Groups:  "Filter,Metadata",
}, {
	Name:    "metadata_filter_from",
	Default: []string{},
	Help:    "Read metadata filtering patterns from a file (use - to read from stdin)",
	Groups:  "Filter,Metadata",
}, {
	Name:    "metadata_exclude",
	Default: []string{},
	Help:    "Exclude metadatas matching pattern",
	Groups:  "Filter,Metadata",
}, {
	Name:    "metadata_exclude_from",
	Default: []string{},
	Help:    "Read metadata exclude patterns from file (use - to read from stdin)",
	Groups:  "Filter,Metadata",
}, {
	Name:    "metadata_include",
	Default: []string{},
	Help:    "Include metadatas matching pattern",
	Groups:  "Filter,Metadata",
}, {
	Name:    "metadata_include_from",
	Default: []string{},
	Help:    "Read metadata include patterns from file (use - to read from stdin)",
	Groups:  "Filter,Metadata",
}}

// Options configures the filter
type Options struct {
	DeleteExcluded bool          `config:"delete_excluded"`
	RulesOpt                     // embedded so we don't change the JSON API
	ExcludeFile    []string      `config:"exclude_if_present"`
	FilesFrom      []string      `config:"files_from"`
	FilesFromRaw   []string      `config:"files_from_raw"`
	MetaRules      RulesOpt      `config:"metadata"`
	MinAge         fs.Duration   `config:"min_age"`
	MaxAge         fs.Duration   `config:"max_age"`
	MinSize        fs.SizeSuffix `config:"min_size"`
	MaxSize        fs.SizeSuffix `config:"max_size"`
	IgnoreCase     bool          `config:"ignore_case"`
	HashFilter     string        `config:"hash_filter"`
}

func init() {
	fs.RegisterGlobalOptions(fs.OptionsInfo{Name: "filter", Opt: &Opt, Options: OptionsInfo, Reload: Reload})
}

// Opt is the default config for the filter
var Opt = Options{
	MinAge:  fs.DurationOff, // These have to be set here as the options are parsed once before the defaults are set
	MaxAge:  fs.DurationOff,
	MinSize: fs.SizeSuffix(-1),
	MaxSize: fs.SizeSuffix(-1),
}

// FilesMap describes the map of files to transfer
type FilesMap map[string]struct{}

// Filter describes any filtering in operation
type Filter struct {
	Opt         Options
	ModTimeFrom time.Time
	ModTimeTo   time.Time
	fileRules   rules
	dirRules    rules
	metaRules   rules
	files       FilesMap // files if filesFrom
	dirs        FilesMap // dirs from filesFrom
	hashFilterN uint64   // if non 0 do hash filtering
	hashFilterK uint64   // select partition K/N
}

// NewFilter parses the command line options and creates a Filter
// object.  If opt is nil, then DefaultOpt will be used
func NewFilter(opt *Options) (f *Filter, err error) {
	f = &Filter{}

	// Make a copy of the options
	if opt != nil {
		f.Opt = *opt
	} else {
		f.Opt = Opt
	}

	// Filter flags
	if f.Opt.MinAge.IsSet() {
		f.ModTimeTo = time.Now().Add(-time.Duration(f.Opt.MinAge))
	}
	if f.Opt.MaxAge.IsSet() {
		f.ModTimeFrom = time.Now().Add(-time.Duration(f.Opt.MaxAge))
		if !f.ModTimeTo.IsZero() && f.ModTimeTo.Before(f.ModTimeFrom) {
			return nil, fmt.Errorf("filter: --min-age %q can't be larger than --max-age %q", opt.MinAge, opt.MaxAge)
		}
	}
	if f.Opt.HashFilter != "" {
		f.hashFilterK, f.hashFilterN, err = parseHashFilter(f.Opt.HashFilter)
		if err != nil {
			return nil, err
		}
	}

	err = parseRules(&f.Opt.RulesOpt, f.Add, f.Clear)
	if err != nil {
		return nil, err
	}

	err = parseRules(&f.Opt.MetaRules, f.metaRules.Add, f.metaRules.clear)
	if err != nil {
		return nil, err
	}

	inActive := f.InActive()

	for _, rule := range f.Opt.FilesFrom {
		if !inActive {
			return nil, fmt.Errorf("the usage of --files-from overrides all other filters, it should be used alone or with --files-from-raw")
		}
		f.initAddFile() // init to show --files-from set even if no files within
		err := forEachLine(rule, false, func(line string) error {
			return f.AddFile(line)
		})
		if err != nil {
			return nil, err
		}
	}

	for _, rule := range f.Opt.FilesFromRaw {
		// --files-from-raw can be used with --files-from, hence we do
		// not need to get the value of f.InActive again
		if !inActive {
			return nil, fmt.Errorf("the usage of --files-from-raw overrides all other filters, it should be used alone or with --files-from")
		}
		f.initAddFile() // init to show --files-from set even if no files within
		err := forEachLine(rule, true, func(line string) error {
			return f.AddFile(line)
		})
		if err != nil {
			return nil, err
		}
	}

	if fs.GetConfig(context.Background()).Dump&fs.DumpFilters != 0 {
		fmt.Println("--- start filters ---")
		fmt.Println(f.DumpFilters())
		fmt.Println("--- end filters ---")
	}
	return f, nil
}

// Parse the --hash-filter arguments into k/n
func parseHashFilter(hashFilter string) (k, n uint64, err error) {
	slash := strings.IndexRune(hashFilter, '/')
	if slash < 0 {
		return 0, 0, fmt.Errorf("filter: --hash-filter: no / found")
	}
	kStr, nStr := hashFilter[:slash], hashFilter[slash+1:]
	n, err = strconv.ParseUint(nStr, 10, 64)
	if err != nil {
		return 0, 0, fmt.Errorf("filter: --hash-filter: can't parse N=%q: %v", nStr, err)
	}
	if n == 0 {
		return 0, 0, fmt.Errorf("filter: --hash-filter: N must be greater than 0")
	}
	if kStr == "@" {
		k = rand.Uint64N(n)
	} else {
		k, err = strconv.ParseUint(kStr, 10, 64)
		if err != nil {
			return 0, 0, fmt.Errorf("filter: --hash-filter: can't parse K=%q: %v", kStr, err)
		}
		k %= n
	}
	return k, n, nil
}

func mustNewFilter(opt *Options) *Filter {
	f, err := NewFilter(opt)
	if err != nil {
		panic(err)
	}
	return f
}

// addDirGlobs adds directory globs from the file glob passed in
func (f *Filter) addDirGlobs(Include bool, glob string) error {
	for _, dirGlob := range globToDirGlobs(glob) {
		// Don't add "/" as we always include the root
		if dirGlob == "/" {
			continue
		}
		dirRe, err := GlobPathToRegexp(dirGlob, f.Opt.IgnoreCase)
		if err != nil {
			return err
		}
		f.dirRules.add(Include, dirRe)
	}
	return nil
}

// Add adds a filter rule with include or exclude status indicated
func (f *Filter) Add(Include bool, glob string) error {
	isDirRule := strings.HasSuffix(glob, "/")
	isFileRule := !isDirRule
	// Make excluding "dir/" equivalent to excluding "dir/**"
	if isDirRule && !Include {
		glob += "**"
	}
	if strings.Contains(glob, "**") {
		isDirRule, isFileRule = true, true
	}
	re, err := GlobPathToRegexp(glob, f.Opt.IgnoreCase)
	if err != nil {
		return err
	}
	if isFileRule {
		f.fileRules.add(Include, re)
		// If include rule work out what directories are needed to scan
		// if exclude rule, we can't rule anything out
		// Unless it is `*` which matches everything
		// NB ** and /** are DirRules
		if Include || glob == "*" {
			err = f.addDirGlobs(Include, glob)
			if err != nil {
				return err
			}
		}
	}
	if isDirRule {
		f.dirRules.add(Include, re)
	}
	return nil
}

// AddRule adds a filter rule with include/exclude indicated by the prefix
//
// These are
//
//   - glob
//   - glob
//     !
//
// '+' includes the glob, '-' excludes it and '!' resets the filter list
//
// Line comments may be introduced with '#' or ';'
func (f *Filter) AddRule(rule string) error {
	return addRule(rule, f.Add, f.Clear)
}

// initAddFile creates f.files and f.dirs
func (f *Filter) initAddFile() {
	if f.files == nil {
		f.files = make(FilesMap)
		f.dirs = make(FilesMap)
	}
}

// AddFile adds a single file to the files from list
func (f *Filter) AddFile(file string) error {
	f.initAddFile()
	file = strings.Trim(file, "/")
	f.files[file] = struct{}{}
	// Put all the parent directories into f.dirs
	for {
		file = path.Dir(file)
		if file == "." {
			break
		}
		if _, found := f.dirs[file]; found {
			break
		}
		f.dirs[file] = struct{}{}
	}
	return nil
}

// Files returns all the files from the `--files-from` list
//
// It may be nil if the list is empty
func (f *Filter) Files() FilesMap {
	return f.files
}

// Clear clears all the filter rules
func (f *Filter) Clear() {
	f.fileRules.clear()
	f.dirRules.clear()
	f.metaRules.clear()
}

// InActive returns false if any filters are active
func (f *Filter) InActive() bool {
	return (f.files == nil &&
		f.ModTimeFrom.IsZero() &&
		f.ModTimeTo.IsZero() &&
		f.Opt.MinSize < 0 &&
		f.Opt.MaxSize < 0 &&
		f.fileRules.len() == 0 &&
		f.dirRules.len() == 0 &&
		f.metaRules.len() == 0 &&
		len(f.Opt.ExcludeFile) == 0 &&
		f.hashFilterN == 0)
}

// IncludeRemote returns whether this remote passes the filter rules.
func (f *Filter) IncludeRemote(remote string) bool {
	// filesFrom takes precedence
	if f.files != nil {
		_, include := f.files[remote]
		return include
	}
	if f.hashFilterN != 0 {
		// Normalise the remote first in case we are using a
		// case insensitive remote or a remote which needs
		// unicode normalisation. This means all the remotes
		// which could be normalised together will be in the
		// same partition.
		normalized := norm.NFC.String(remote)
		normalized = strings.ToLower(normalized)
		hashBytes := md5.Sum([]byte(normalized))
		hash := binary.LittleEndian.Uint64(hashBytes[:])
		partition := hash % f.hashFilterN
		if partition != f.hashFilterK {
			return false
		}
	}
	return f.fileRules.include(remote)
}

// ListContainsExcludeFile checks if exclude file is present in the list.
func (f *Filter) ListContainsExcludeFile(entries fs.DirEntries) bool {
	if len(f.Opt.ExcludeFile) == 0 {
		return false
	}
	for _, entry := range entries {
		obj, ok := entry.(fs.Object)
		if ok {
			basename := path.Base(obj.Remote())
			if slices.Contains(f.Opt.ExcludeFile, basename) {
				return true
			}
		}
	}
	return false
}

// IncludeDirectory returns a function which checks whether this
// directory should be included in the sync or not.
func (f *Filter) IncludeDirectory(ctx context.Context, fs fs.Fs) func(string) (bool, error) {
	return func(remote string) (bool, error) {
		remote = strings.Trim(remote, "/")
		// first check if we need to remove directory based on
		// the exclude file
		excl, err := f.DirContainsExcludeFile(ctx, fs, remote)
		if err != nil {
			return false, err
		}
		if excl {
			return false, nil
		}

		// filesFrom takes precedence
		if f.files != nil {
			_, include := f.dirs[remote]
			return include, nil
		}
		remote += "/"
		return f.dirRules.include(remote), nil
	}
}

// DirContainsExcludeFile checks if exclude file is present in a
// directory. If fs is nil, it works properly if ExcludeFile is an
// empty string (for testing).
func (f *Filter) DirContainsExcludeFile(ctx context.Context, fremote fs.Fs, remote string) (bool, error) {
	if len(f.Opt.ExcludeFile) > 0 {
		for _, excludeFile := range f.Opt.ExcludeFile {
			exists, err := fs.FileExists(ctx, fremote, path.Join(remote, excludeFile))
			if err != nil {
				return false, err
			}
			if exists {
				return true, nil
			}
		}
	}
	return false, nil
}

// Include returns whether this object should be included into the
// sync or not and logs the reason for exclusion if not included
func (f *Filter) Include(remote string, size int64, modTime time.Time, metadata fs.Metadata) bool {
	// filesFrom takes precedence
	if f.files != nil {
		_, include := f.files[remote]
		if !include {
			fs.Debugf(remote, "Excluded (FilesFrom Filter)")
		}
		return include
	}
	if !f.ModTimeFrom.IsZero() && modTime.Before(f.ModTimeFrom) {
		fs.Debugf(remote, "Excluded (ModTime Filter)")
		return false
	}
	if !f.ModTimeTo.IsZero() && modTime.After(f.ModTimeTo) {
		fs.Debugf(remote, "Excluded (ModTime Filter)")
		return false
	}
	if f.Opt.MinSize >= 0 && size < int64(f.Opt.MinSize) {
		fs.Debugf(remote, "Excluded (Size Filter)")
		return false
	}
	if f.Opt.MaxSize >= 0 && size > int64(f.Opt.MaxSize) {
		fs.Debugf(remote, "Excluded (Size Filter)")
		return false
	}
	if f.metaRules.len() > 0 {
		metadatas := make([]string, 0, len(metadata)+1)
		for key, value := range metadata {
			metadatas = append(metadatas, fmt.Sprintf("%s=%s", key, value))
		}
		if len(metadata) == 0 {
			// If there is no metadata, add a null one
			// otherwise the default action isn't taken
			metadatas = append(metadatas, "\x00=\x00")
		}
		if !f.metaRules.includeMany(metadatas) {
			fs.Debugf(remote, "Excluded (Metadata Filter)")
			return false
		}
	}
	include := f.IncludeRemote(remote)
	if !include {
		fs.Debugf(remote, "Excluded (Path Filter)")
	}
	return include
}

// IncludeObject returns whether this object should be included into
// the sync or not. This is a convenience function to avoid calling
// o.ModTime(), which is an expensive operation.
func (f *Filter) IncludeObject(ctx context.Context, o fs.Object) bool {
	var modTime time.Time

	if !f.ModTimeFrom.IsZero() || !f.ModTimeTo.IsZero() {
		modTime = o.ModTime(ctx)
	} else {
		modTime = time.Unix(0, 0)
	}
	var metadata fs.Metadata
	if f.metaRules.len() > 0 {
		var err error
		metadata, err = fs.GetMetadata(ctx, o)
		if err != nil {
			fs.Errorf(o, "Failed to read metadata: %v", err)
			metadata = nil
		}

	}
	return f.Include(o.Remote(), o.Size(), modTime, metadata)
}

// DumpFilters dumps the filters in textual form, 1 per line
func (f *Filter) DumpFilters() string {
	rules := []string{}
	if !f.ModTimeFrom.IsZero() {
		rules = append(rules, fmt.Sprintf("Last-modified date must be equal or greater than: %s", f.ModTimeFrom.String()))
	}
	if !f.ModTimeTo.IsZero() {
		rules = append(rules, fmt.Sprintf("Last-modified date must be equal or less than: %s", f.ModTimeTo.String()))
	}
	if f.Opt.MinSize >= 0 {
		rules = append(rules, fmt.Sprintf("Minimum size is: %s", f.Opt.MinSize.ByteUnit()))
	}
	if f.Opt.MaxSize >= 0 {
		rules = append(rules, fmt.Sprintf("Maximum size is: %s", f.Opt.MaxSize.ByteUnit()))
	}
	rules = append(rules, "--- File filter rules ---")
	for _, rule := range f.fileRules.rules {
		rules = append(rules, rule.String())
	}
	rules = append(rules, "--- Directory filter rules ---")
	for _, dirRule := range f.dirRules.rules {
		rules = append(rules, dirRule.String())
	}
	if f.metaRules.len() > 0 {
		rules = append(rules, "--- Metadata filter rules ---")
		for _, metaRule := range f.metaRules.rules {
			rules = append(rules, metaRule.String())
		}
	}
	return strings.Join(rules, "\n")
}

// HaveFilesFrom returns true if --files-from has been supplied
func (f *Filter) HaveFilesFrom() bool {
	return f.files != nil
}

var errFilesFromNotSet = errors.New("--files-from not set so can't use Filter.ListR")

// MakeListR makes function to return all the files set using --files-from
func (f *Filter) MakeListR(ctx context.Context, NewObject func(ctx context.Context, remote string) (fs.Object, error)) fs.ListRFn {
	return func(ctx context.Context, dir string, callback fs.ListRCallback) error {
		ci := fs.GetConfig(ctx)
		if !f.HaveFilesFrom() {
			return errFilesFromNotSet
		}
		var (
			checkers = ci.Checkers
			remotes  = make(chan string, checkers)
			g, gCtx  = errgroup.WithContext(ctx)
		)
		for range checkers {
			g.Go(func() (err error) {
				var entries = make(fs.DirEntries, 1)
				for remote := range remotes {
					entries[0], err = NewObject(gCtx, remote)
					if err == fs.ErrorObjectNotFound {
						// Skip files that are not found
					} else if err != nil {
						return err
					} else {
						err = callback(entries)
						if err != nil {
							return err
						}
					}
				}
				return nil
			})
		}
	outer:
		for remote := range f.files {
			select {
			case remotes <- remote:
			case <-gCtx.Done():
				break outer
			}
		}
		close(remotes)
		return g.Wait()
	}
}

// UsesDirectoryFilters returns true if the filter uses directory
// filters and false if it doesn't.
//
// This is used in deciding whether to walk directories or use ListR
func (f *Filter) UsesDirectoryFilters() bool {
	if len(f.dirRules.rules) == 0 {
		return false
	}
	rule := f.dirRules.rules[0]
	re := rule.Regexp.String()
	if rule.Include && re == "^.*$" {
		return false
	}
	return true
}

// Context key for config
type configContextKeyType struct{}

var configContextKey = configContextKeyType{}

// GetConfig returns the global or context sensitive config
func GetConfig(ctx context.Context) *Filter {
	if ctx == nil {
		return globalConfig
	}
	c := ctx.Value(configContextKey)
	if c == nil {
		return globalConfig
	}
	return c.(*Filter)
}

// CopyConfig copies the global config (if any) from srcCtx into
// dstCtx returning the new context.
func CopyConfig(dstCtx, srcCtx context.Context) context.Context {
	if srcCtx == nil {
		return dstCtx
	}
	c := srcCtx.Value(configContextKey)
	if c == nil {
		return dstCtx
	}
	return context.WithValue(dstCtx, configContextKey, c)
}

// AddConfig returns a mutable config structure based on a shallow
// copy of that found in ctx and returns a new context with that added
// to it.
func AddConfig(ctx context.Context) (context.Context, *Filter) {
	c := GetConfig(ctx)
	cCopy := new(Filter)
	*cCopy = *c
	newCtx := context.WithValue(ctx, configContextKey, cCopy)
	return newCtx, cCopy
}

// ReplaceConfig replaces the filter config in the ctx with the one
// passed in and returns a new context with that added to it.
func ReplaceConfig(ctx context.Context, f *Filter) context.Context {
	newCtx := context.WithValue(ctx, configContextKey, f)
	return newCtx
}

// Context key for the "use filter" flag
type useFlagContextKeyType struct{}

var useFlagContextKey = useFlagContextKeyType{}

// GetUseFilter obtains the "use filter" flag from context
// The flag tells filter-aware backends (Drive) to constrain List using filter
func GetUseFilter(ctx context.Context) bool {
	if ctx != nil {
		if pVal := ctx.Value(useFlagContextKey); pVal != nil {
			return *(pVal.(*bool))
		}
	}
	return false
}

// SetUseFilter returns a context having (re)set the "use filter" flag
func SetUseFilter(ctx context.Context, useFilter bool) context.Context {
	if useFilter == GetUseFilter(ctx) {
		return ctx // Minimize depth of nested contexts
	}
	pVal := new(bool)
	*pVal = useFilter
	return context.WithValue(ctx, useFlagContextKey, pVal)
}

// Reload the filters from the flags
func Reload(ctx context.Context) (err error) {
	fi := GetConfig(ctx)
	newFilter, err := NewFilter(&Opt)
	if err != nil {
		return err
	}
	*fi = *newFilter
	return nil
}
