package jellycompat

import (
	"encoding/binary"
	"fmt"
	"strconv"
	"sync"

	"github.com/google/uuid"
)

// EncodedIDType distinguishes packed compat UUIDs.
type EncodedIDType byte

const (
	EncodedIDLibrary     EncodedIDType = 1
	EncodedIDItem        EncodedIDType = 2
	EncodedIDMediaSource EncodedIDType = 3
	EncodedIDSeason      EncodedIDType = 4
	EncodedIDPlaySession EncodedIDType = 5
	EncodedIDGenre       EncodedIDType = 6
	EncodedIDStudio      EncodedIDType = 7
	EncodedIDPerson      EncodedIDType = 8
)

var (
	pseudoUserNamespace = uuid.MustParse("3dfcc388-bf95-5572-bc16-7f1a375992dd")
	stringIDNamespaces  = map[EncodedIDType]uuid.UUID{
		EncodedIDItem:        uuid.MustParse("0b6716ca-1f61-5987-b17b-f592f04fd6b3"),
		EncodedIDSeason:      uuid.MustParse("29831b2b-dad5-5a85-b506-4d1fb2da01ed"),
		EncodedIDPlaySession: uuid.MustParse("75a69ca8-f95f-5e9d-ac0a-d34a37b93eb4"),
		EncodedIDGenre:       uuid.MustParse("c0cbb8ea-8331-52c0-b160-15e7cf899fb0"),
		EncodedIDStudio:      uuid.MustParse("23712982-b769-592d-9360-b4d3f39654db"),
		EncodedIDPerson:      uuid.MustParse("a4e7c1d6-3b8f-5a2e-9c01-7d6f4e8b2a13"),
	}
)

// DecodedID is a packed compat UUID decoded back to its type and value.
type DecodedID struct {
	Type  EncodedIDType
	Value uint64
}

// ResourceIDCodec encodes numeric IDs directly and keeps reversible mappings
// for opaque string content IDs used by media items and seasons.
type ResourceIDCodec struct {
	mu                sync.RWMutex
	reverse           map[string]registeredID
	mediaSourceOwners map[int64]string
}

type registeredID struct {
	kind  EncodedIDType
	value string
}

// PseudoUserID deterministically derives the Jellyfin pseudo-user UUID.
func PseudoUserID(userID int, profileID string) uuid.UUID {
	return uuid.NewSHA1(pseudoUserNamespace, fmt.Appendf(nil, "%d:%s", userID, profileID))
}

// NewResourceIDCodec creates a new route ID codec.
func NewResourceIDCodec() *ResourceIDCodec {
	return &ResourceIDCodec{
		reverse:           make(map[string]registeredID),
		mediaSourceOwners: make(map[int64]string),
	}
}

// EncodeNumericID packs a numeric Silo identifier into a UUID.
func EncodeNumericID(kind EncodedIDType, value uint64) uuid.UUID {
	var raw [16]byte
	raw[0] = byte(kind)
	binary.BigEndian.PutUint64(raw[8:], value)
	return uuid.UUID(raw)
}

// EncodeStringID encodes a Silo identifier into a Jellyfin UUID string.
func (c *ResourceIDCodec) EncodeStringID(kind EncodedIDType, value string) string {
	if numeric, err := strconv.ParseUint(value, 10, 64); err == nil {
		return EncodeNumericID(kind, numeric).String()
	}

	namespace, ok := stringIDNamespaces[kind]
	if !ok {
		namespace = uuid.NameSpaceURL
	}
	encoded := uuid.NewSHA1(namespace, []byte(value))

	c.mu.Lock()
	c.reverse[encoded.String()] = registeredID{kind: kind, value: value}
	c.mu.Unlock()

	return encoded.String()
}

// EncodeIntID encodes a native integer ID into a Jellyfin UUID string.
func (c *ResourceIDCodec) EncodeIntID(kind EncodedIDType, value int64) string {
	return EncodeNumericID(kind, uint64(value)).String()
}

// DecodeStringID decodes a compat UUID back to the original native string ID.
func (c *ResourceIDCodec) DecodeStringID(kind EncodedIDType, raw string) (string, error) {
	if decoded, err := DecodeID(raw); err == nil && decoded.Type == kind {
		return strconv.FormatUint(decoded.Value, 10), nil
	}

	c.mu.RLock()
	registered, ok := c.reverse[raw]
	c.mu.RUnlock()
	if !ok || registered.kind != kind {
		return "", fmt.Errorf("unknown compat id %q", raw)
	}
	return registered.value, nil
}

// DecodeIntID decodes a compat UUID back to a native integer ID.
func (c *ResourceIDCodec) DecodeIntID(kind EncodedIDType, raw string) (int64, error) {
	decoded, err := DecodeID(raw)
	if err != nil {
		return 0, err
	}
	if decoded.Type != kind {
		return 0, fmt.Errorf("unexpected compat id type %d", decoded.Type)
	}
	return int64(decoded.Value), nil
}

// RegisterMediaSourceOwner records which content item owns a media-source/file ID.
func (c *ResourceIDCodec) RegisterMediaSourceOwner(fileID int64, contentID string) {
	c.mu.Lock()
	c.mediaSourceOwners[fileID] = contentID
	c.mu.Unlock()
}

// LookupMediaSourceOwner resolves a media-source/file ID back to its content item.
func (c *ResourceIDCodec) LookupMediaSourceOwner(fileID int64) (string, bool) {
	c.mu.RLock()
	contentID, ok := c.mediaSourceOwners[fileID]
	c.mu.RUnlock()
	return contentID, ok
}

// DecodeID unpacks a compat UUID into its original numeric value.
func DecodeID(raw string) (DecodedID, error) {
	parsed, err := uuid.Parse(raw)
	if err != nil {
		return DecodedID{}, fmt.Errorf("parse uuid: %w", err)
	}

	return DecodedID{
		Type:  EncodedIDType(parsed[0]),
		Value: binary.BigEndian.Uint64(parsed[8:]),
	}, nil
}