package sync

import (
	"bytes"
	"fmt"
	"time"
	"unicode"
	"unicode/utf8"

	"github.com/bluesky-social/indigo/atproto/syntax"
	"github.com/fxamacker/cbor/v2"
)

type ExistingRecord struct {
	URI   string
	CID   string
	Value *PlayRecord
}

func normalizeToBytes(s string) []byte {
	b := make([]byte, 0, len(s))

	for _, r := range s {
		r = unicode.ToLower(r)

		if r >= 128 || unicode.IsLetter(r) || unicode.IsNumber(r) {
			b = utf8.AppendRune(b, r)
		}
	}

	return b
}

type PlayRecord struct {
	Type                   string             `json:"$type"`
	TrackName              string             `json:"trackName"`
	Artists                []PlayRecordArtist `json:"artists"`
	PlayedTime             Timestamp          `json:"playedTime"`
	SubmissionClientAgent  string             `json:"submissionClientAgent"`
	MusicServiceBaseDomain string             `json:"musicServiceBaseDomain"`
	ReleaseName            string             `json:"releaseName,omitempty"`
	ReleaseMbId            string             `json:"releaseMbId,omitempty"`
	RecordingMbId          string             `json:"recordingMbId,omitempty"`
	OriginUrl              string             `json:"originUrl"`
	MsPlayed               int                `json:"msPlayed,omitempty"`

	normalizedTrack  []byte `json:"-"`
	normalizedArtist []byte `json:"-"`
}

func (r *PlayRecord) ArtistName() string {
	if len(r.Artists) > 0 {
		return r.Artists[0].ArtistName
	}
	return "Unknown Artist"
}

func (r *PlayRecord) normalizeArtist() []byte {
	if len(r.normalizedArtist) > 0 {
		return r.normalizedArtist
	}

	r.normalizedArtist = normalizeToBytes(r.ArtistName())

	return r.normalizedArtist
}

func (r *PlayRecord) normalizeTrack() []byte {
	if len(r.normalizedTrack) != 0 {
		return r.normalizedTrack
	}

	r.normalizedTrack = normalizeToBytes(r.TrackName)

	return r.normalizedTrack
}

func (r *PlayRecord) hasMBID() bool {
	for _, a := range r.Artists {
		if a.ArtistMbId != "" {
			return true
		}
	}

	return r.RecordingMbId != ""
}

func (r *PlayRecord) isLastFM() bool {
	return r.MusicServiceBaseDomain == MusicServiceLastFM
}

func (r *PlayRecord) betterThan(other *PlayRecord) bool {
	return (r.hasMBID() && !other.hasMBID()) || (r.isLastFM() && !other.isLastFM())
}

func (r *PlayRecord) IsDuplicate(other *PlayRecord, tolerance time.Duration) (bool, bool) {
	return r.sameAs(other, tolerance), r.betterThan(other)
}

func (r *PlayRecord) sameAs(other *PlayRecord, tolerance time.Duration) bool {
	if !bytes.Equal(r.normalizeTrack(), other.normalizeTrack()) {
		return false
	}
	if !bytes.Equal(r.normalizeArtist(), other.normalizeArtist()) {
		return false
	}

	diff := r.PlayedTime.Sub(other.PlayedTime.Time)
	return max(diff, -diff) <= tolerance
}

func (r *PlayRecord) Time() time.Time {
	return r.PlayedTime.Time
}

type PlayRecordArtist struct {
	ArtistName string `json:"artistName"`
	ArtistMbId string `json:"artistMbId,omitempty"`
}

const (
	MusicServiceLastFM  = "last.fm"
	MusicServiceSpotify = "spotify.com"

	TimeBucketSize    = 30 * time.Second
	MinListenDuration = 30 * time.Second

	DefaultClientAgent = "lazuli/dev"
)

func CreateRecordKey(record *PlayRecord) string {
	return string(syntax.NewTIDFromTime(record.PlayedTime.Time, 0))
}

func CreateRecordKeys(records []*PlayRecord) []string {
	keys := make([]string, len(records))
	usedTIDs := make(map[string]int)

	for i, rec := range records {
		t := rec.PlayedTime.Time
		tid := syntax.NewTIDFromTime(t, 0)
		for usedTIDs[string(tid)] > 0 {
			usedTIDs[string(tid)]++
			tid = syntax.NewTIDFromTime(t, uint(usedTIDs[string(tid)]-1))
		}
		usedTIDs[string(tid)]++
		keys[i] = string(tid)
	}
	return keys
}

func FilterNew(records []*PlayRecord, existing []ExistingRecord, processed map[string]bool, tolerance time.Duration) []*PlayRecord {
	existingSet := make(map[*PlayRecord]bool)
	for _, rec := range existing {
		existingSet[rec.Value] = true
	}

	var newRecords []*PlayRecord
	for _, record := range records {
		if processed != nil && processed[CreateRecordKey(record)] {
			continue
		}

		if len(existingSet) > 0 {
			isDup := false
			for existingRec := range existingSet {
				if record.sameAs(existingRec, tolerance) {
					isDup = true
					break
				}
			}
			if isDup {
				continue
			}
		}
		newRecords = append(newRecords, record)
	}
	return newRecords
}

func FindDuplicates(records []ExistingRecord) map[string][]ExistingRecord {
	groups := make(map[string][]ExistingRecord)
	for _, rec := range records {
		key := CreateRecordKey(rec.Value)
		if key == "|||" {
			continue
		}
		groups[key] = append(groups[key], rec)
	}

	duplicates := make(map[string][]ExistingRecord)
	for key, group := range groups {
		if len(group) >= 2 {
			duplicates[key] = group
		}
	}
	return duplicates
}

type Timestamp struct {
	time.Time
}

func (t Timestamp) MarshalJSON() ([]byte, error) {
	return []byte(`"` + t.Format(time.RFC3339Nano) + `"`), nil
}

func (t *Timestamp) UnmarshalCBOR(data []byte) error {
	var s string

	err := cbor.Unmarshal(data, &s)
	if err != nil {
		return fmt.Errorf("failed to decode timestamp cbor value: %w", err)
	}

	return t.parse(s)
}

func (t *Timestamp) UnmarshalJSON(data []byte) error {
	if string(data) == "null" {
		*t = Timestamp{}
		return nil
	}

	return t.parse(string(data[1 : len(data)-1]))
}

func (t *Timestamp) parse(s string) error {
	tm, err := time.Parse(time.RFC3339Nano, s)
	if err != nil {
		tm, err = time.Parse(time.RFC3339, s)
		if err != nil {
			return fmt.Errorf("failed to parse timestamp %q: %w", s, err)
		}
	}

	*t = Timestamp{Time: tm}
	return nil
}