package api

import (
	"context"

	"felis.lolicon.best/internal/apis/felis/v1alpha1"
	corev1 "k8s.io/api/core/v1"
)

// ServerInfo is the lifecycle view read from the MinecraftServer CRD + status
// (spec §4). The CRD is the source-of-truth; the API mutates its spec only via
// the app-tier desiredState lever (wake/stop, spec §9.1) and the admin-tier spec
// patch (spec §7 PATCH /servers/{name}) — never the business-layer fields, which
// live in Postgres (spec §22).
type ServerInfo struct {
	Name            string `json:"name"`
	Subdomain       string `json:"subdomain"`
	Phase           string `json:"phase"`
	Ready           bool   `json:"ready"`
	AutostartPolicy string `json:"autostartPolicy,omitempty"`
	DesiredState    string `json:"desiredState,omitempty"`
	EndpointMode    string `json:"endpointMode,omitempty"`
	EndpointAddress string `json:"endpointAddress,omitempty"`
	PlayersOnline   int32  `json:"playersOnline"`
	PlayersMax      int32  `json:"playersMax"`
	DisplayName     string `json:"displayName,omitempty"`
	Image           string `json:"image,omitempty"`
	JavaMemory      string `json:"javaMemory,omitempty"`
	// Memory is the pod memory limit (the §22 ceiling) — what an admin picks as
	// the server's memory. JavaMemory is the heap derived from it.
	Memory      string `json:"memory,omitempty"`
	StorageSize string `json:"storageSize,omitempty"`
	CPU         string `json:"cpu,omitempty"`
	// IdleStopSeconds is how long the server may sit empty before idle
	// auto-stop scales it down; 0 means it never idles out.
	IdleStopSeconds int32 `json:"idleStopSeconds"`
	// PlayerCountUnknown is true while the operator cannot read the player
	// count over RCON; idle auto-stop waits until it can.
	PlayerCountUnknown bool `json:"playerCountUnknown,omitempty"`
	// LegacyForwarding mirrors the CR's forwarding=legacy label: the proxy
	// forwards this server's players in the handshake address (#15).
	LegacyForwarding bool `json:"legacyForwarding,omitempty"`
	// AutoRestarts is how often the operator has recreated the pod of this start
	// after it timed out; StartGaveUp is true once no automatic retry is coming
	// (v1alpha1.StartGaveUp). A Failed server without StartGaveUp is still in its
	// restart backoff and may yet come up on its own.
	AutoRestarts int32 `json:"autoRestarts,omitempty"`
	StartGaveUp  bool  `json:"startGaveUp,omitempty"`
	// Resources is the spec's pod resource block. It stays off the wire; a spec
	// patch reads it so the fields the admin left out keep their values.
	Resources corev1.ResourceRequirements `json:"-"`
}

// CreateServerInput is the validated, structured create-server form (spec §15).
// felis-api has already enforced naming, reservation, image whitelist, quota
// policy, and the §22 memory ceiling before this reaches the cluster: there is
// no free-form YAML path — every field is a typed, validated value. A created
// server starts DesiredState=Stopped and unowned (claimed later, spec §9.3).
type CreateServerInput struct {
	Name            string
	Subdomain       string
	DisplayName     string
	Image           string
	JavaMemory      string
	StorageSize     string
	AutostartPolicy v1alpha1.AutostartPolicy
	// Resources is the fully-resolved pod resource block. Its memory limit is the
	// §22 ceiling — felis-api guarantees it is non-zero (the operator does not
	// derive a cgroup limit from JavaMemory).
	Resources corev1.ResourceRequirements
}

// ServerSpecPatch is the resolved, validated set of admin-tier mutations applied
// to one MinecraftServer spec (spec §7 PATCH /servers/{name}). felis-api has
// already validated naming, admitted any new image against the whitelist, parsed
// the policy, and derived the §22 memory ceiling before this reaches the cluster:
// there is no free-form YAML path. Every field is a pointer — nil means "leave
// unchanged", so the patch touches only the fields the admin explicitly set. It
// deliberately omits the dual-write routing identity (subdomain, the object name)
// and the world PVC size, which felis-api rejects before constructing this so the
// CRD and Postgres never desync (spec §22).
type ServerSpecPatch struct {
	DisplayName     *string
	AutostartPolicy *v1alpha1.AutostartPolicy
	Image           *string
	// Resources is the whole pod block after the patch — the current spec with the
	// admin's changes laid over it — whose memory limit is the non-zero §22
	// ceiling. JavaMemory is the heap re-derived from that ceiling; it is set only
	// when the memory moved, so a CPU-only patch leaves the heap alone.
	JavaMemory *string
	Resources  *corev1.ResourceRequirements
	// IdleStopSeconds sets idle auto-stop: 0 turns it off, anything else is the
	// empty duration before the stop (already range-checked).
	IdleStopSeconds *int32
}

// Cluster is the lifecycle-layer access the API depends on: reads of the
// MinecraftServer CRD, the app-tier desiredState lever (spec §9.1), the admin-tier
// create (spec §15), and the admin-tier spec patch (spec §7). It is an interface
// so handlers are tested against a fake; the controller-runtime implementation
// (k8sCluster) is integration-tested only — it requires a live cluster.
type Cluster interface {
	// Ping verifies the K8s API is reachable and the MinecraftServer cache has
	// synced — used by /readyz (spec §7), so a replica serves the fleet reads only
	// once it holds the whole fleet.
	Ping(ctx context.Context) error

	// GetServer reads one MinecraftServer's lifecycle view, or ErrNotFound.
	GetServer(ctx context.Context, name string) (*ServerInfo, error)
	// WorldVolumeExists reports whether the server's world PVC exists in the
	// server namespace. A server that never started — or whose world the
	// retention reaper already archived and deleted — has no claim, and a
	// backup/restore Job would hang Pending on the missing volume with nothing
	// ever recorded, so both handlers refuse those up front.
	WorldVolumeExists(ctx context.Context, name string) (bool, error)
	// GetBySubdomain finds the MinecraftServer whose spec.subdomain matches, or
	// ErrNotFound.
	GetBySubdomain(ctx context.Context, subdomain string) (*ServerInfo, error)
	// ListServers returns the lifecycle view of every MinecraftServer, for the
	// velocity registration pull (spec §7 GET /servers).
	ListServers(ctx context.Context) ([]ServerInfo, error)
	// SetDesiredState flips spec.desiredState — the only write the API performs
	// against the CRD (spec §9.1). It is idempotent. Flipping to Running returns a
	// *MaintenanceBusyError (errors.Is ErrMaintenanceInProgress) while a restore,
	// backup or file write holds the world volume.
	SetDesiredState(ctx context.Context, name string, state v1alpha1.DesiredState) error
	// RetryStart is SetDesiredState(Running) for a server whose start Failed: it
	// also asks the operator to start it over with a fresh auto-restart budget
	// (v1alpha1.AnnotationStartRetry). Maintenance refuses it the same way.
	RetryStart(ctx context.Context, name string) error
	// AcquireMaintenance admits one world-volume operation (internal/maintenance
	// kind): ErrNotStopped unless the server is fully stopped, a
	// *MaintenanceBusyError while another operation holds the volume. The check
	// and the lock are one atomic write against a concurrent wake.
	AcquireMaintenance(ctx context.Context, name, kind string) error
	// ReleaseMaintenance drops the admission lock once the operation's Job exists
	// (or could not be created). It is idempotent.
	ReleaseMaintenance(ctx context.Context, name string) error
	// CreateServer creates a MinecraftServer CRD from the validated form (spec
	// §15). It returns ErrConflict if a server of that name already exists.
	CreateServer(ctx context.Context, in CreateServerInput) error
	// PatchServerSpec applies an admin-tier spec mutation (spec §7 PATCH
	// /servers/{name}): only the non-nil fields of the patch are written, via a
	// merge patch so a concurrent operator status write is never clobbered. It
	// returns ErrNotFound if no server of that name exists.
	PatchServerSpec(ctx context.Context, name string, patch ServerSpecPatch) error
}