package proxmox

import (
	"hash/fnv"
	"strconv"
	"strings"

	"gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/provider"
)

const idPrefix = "vms"

// formatProviderID gives vms/<vmid>/<name>: location-free, because VMs can
// migrate between nodes (spec entry 1).
func formatProviderID(vmid int, name string) string {
	return idPrefix + "/" + strconv.Itoa(vmid) + "/" + name
}

// parseProviderID is strict: exactly three segments, the literal "vms", a
// decimal VMID without leading zeros in Proxmox's range, and a non-empty
// name. Anything else is ErrPermanent.
func parseProviderID(id string) (int, string, error) {
	parts := strings.Split(id, "/")
	if len(parts) != 3 || parts[0] != idPrefix || parts[2] == "" {
		return 0, "", permanentf("malformed providerID %q, want vms/<vmid>/<name>", id)
	}
	vmid, err := strconv.Atoi(parts[1])
	if err != nil || strconv.Itoa(vmid) != parts[1] || vmid < provider.ProxmoxMinVMID || vmid > provider.ProxmoxMaxVMID {
		return 0, "", permanentf("malformed providerID %q: %q is not a VMID", id, parts[1])
	}
	return vmid, parts[2], nil
}

// vmidFor is the attempt-th VMID candidate for a Proxy UID: a stable hash of
// the UID placed in [min, max], moving forward and wrapping as attempt grows,
// so a retry of the same Create lands on the same VMID (spec entry 2).
func vmidFor(uid string, min, max, attempt int) int {
	h := fnv.New64a()
	_, _ = h.Write([]byte(uid))
	span := uint64(max - min + 1)
	return min + int((h.Sum64()%span+uint64(attempt)%span)%span)
}