package jellyfin

import (
	"fmt"
	"strconv"
	"strings"
)

// Jellyfin identifies every object with an opaque 32-character lowercase hex
// id (a GUID with the dashes removed). Vellum's ids are int64, and both
// libraries and items must appear as Jellyfin ids — including as a ParentId,
// which a client hands back verbatim. Rendering both as plain decimal would
// make ParentId ambiguous between a library and an item, so libraries get a
// leading 'f' marker. A positive int64 rendered as 32 hex digits always starts
// with 0-7, so 'f' can never collide with an item id.
//
// The mapping is stable and deterministic: the same Vellum row always yields
// the same Jellyfin id, which clients rely on for caching and favourites.

// itemID renders an item's Jellyfin id.
func itemID(id int64) string { return fmt.Sprintf("%032x", uint64(id)) }

// libraryID renders a library's Jellyfin id. The leading 'f' namespaces it
// away from item ids.
func libraryID(id int64) string { return fmt.Sprintf("f%031x", uint64(id)) }

// decodeID reverses itemID/libraryID. isLibrary reports which namespace the id
// came from; ok is false for anything that is not one of our 32-char hex ids.
// Input is lowercased first, because clients sometimes normalise case.
func decodeID(s string) (id int64, isLibrary, ok bool) {
	s = strings.ToLower(strings.TrimSpace(s))
	if len(s) != 32 {
		return 0, false, false
	}
	if s[0] == 'f' {
		n, err := strconv.ParseUint(s[1:], 16, 64)
		if err != nil {
			return 0, false, false
		}
		return int64(n), true, true
	}
	n, err := strconv.ParseUint(s, 16, 64)
	if err != nil {
		return 0, false, false
	}
	// Item ids are positive int64; a value with the top bit set is malformed.
	if n > 1<<63-1 {
		return 0, false, false
	}
	return int64(n), false, true
}