// Package ipfscluster implements a wrapper for the IPFS deamon which
// allows to orchestrate pinning operations among several IPFS nodes.
//
// IPFS Cluster peers form a separate libp2p swarm. A Cluster peer uses
// multiple Cluster Components which perform different tasks like managing
// the underlying IPFS daemons, or providing APIs for external control.
package ipfscluster

import (
	"context"

	"github.com/ipfs-cluster/ipfs-cluster/api"
	"github.com/ipfs-cluster/ipfs-cluster/state"

	peer "github.com/libp2p/go-libp2p/core/peer"
	rpc "github.com/libp2p/go-libp2p-gorpc"
)

// Component represents a piece of ipfscluster. Cluster components
// usually run their own goroutines (a http server for example). They
// communicate with the main Cluster component and other components
// (both local and remote), using an instance of rpc.Client.
type Component interface {
	SetClient(*rpc.Client)
	Shutdown(context.Context) error
}

// Consensus is a component which keeps a shared state in
// IPFS Cluster and triggers actions on updates to that state.
// Currently, Consensus needs to be able to elect/provide a
// Cluster Leader and the implementation is very tight to
// the Cluster main component.
type Consensus interface {
	Component
	// Returns a channel to signal that the consensus layer is ready
	// allowing the main component to wait for it during start.
	Ready(context.Context) <-chan struct{}
	// Logs a pin operation.
	LogPin(context.Context, api.Pin) error
	// Logs an unpin operation.
	LogUnpin(context.Context, api.Pin) error
	AddPeer(context.Context, peer.ID) error
	RmPeer(context.Context, peer.ID) error
	State(context.Context) (state.ReadOnly, error)
	// Provide a node which is responsible to perform
	// specific tasks which must only run in 1 cluster peer.
	Leader(context.Context) (peer.ID, error)
	// Only returns when the consensus state has all log
	// updates applied to it.
	WaitForSync(context.Context) error
	// Clean removes all consensus data.
	Clean(context.Context) error
	// Peers returns the peerset participating in the Consensus.
	Peers(context.Context) ([]peer.ID, error)
	// IsTrustedPeer returns true if the given peer is "trusted".
	// This will grant access to more rpc endpoints and a
	// non-trusted one. This should be fast as it will be
	// called repeatedly for every remote RPC request.
	IsTrustedPeer(context.Context, peer.ID) bool
	// Trust marks a peer as "trusted".
	Trust(context.Context, peer.ID) error
	// Distrust removes a peer from the "trusted" set.
	Distrust(context.Context, peer.ID) error
}

// API is a component which offers an API for Cluster. This is
// a base component.
type API interface {
	Component
}

// IPFSConnector is a component which allows cluster to interact with
// an IPFS daemon. This is a base component.
type IPFSConnector interface {
	Component
	ID(context.Context) (api.IPFSID, error)
	Pin(context.Context, api.Pin) error
	Unpin(context.Context, api.Cid) error
	PinLsCid(context.Context, api.Pin) (api.IPFSPinStatus, error)
	// PinLs returns pins in the pinset of the given types (recursive, direct...)
	PinLs(ctx context.Context, typeFilters []string, out chan<- api.IPFSPinInfo) error
	// ConnectSwarms make sure this peer's IPFS daemon is connected to
	// other peers IPFS daemons.
	ConnectSwarms(context.Context) error
	// SwarmPeers returns the IPFS daemon's swarm peers.
	SwarmPeers(context.Context) ([]peer.ID, error)
	// ConfigKey returns the value for a configuration key.
	// Subobjects are reached with keypaths as "Parent/Child/GrandChild...".
	ConfigKey(keypath string) (interface{}, error)
	// RepoStat returns the current repository size and max limit as
	// provided by "repo stat".
	RepoStat(context.Context) (api.IPFSRepoStat, error)
	// RepoGC performs garbage collection sweep on the IPFS repo.
	RepoGC(context.Context) (api.RepoGC, error)
	// Resolve returns a cid given a path.
	Resolve(context.Context, string) (api.Cid, error)
	// BlockStream adds a stream of blocks to IPFS.
	BlockStream(context.Context, <-chan api.NodeWithMeta) error
	// BlockGet retrieves the raw data of an IPFS block.
	BlockGet(context.Context, api.Cid) ([]byte, error)
}

// Peered represents a component which needs to be aware of the peers
// in the Cluster and of any changes to the peer set.
type Peered interface {
	AddPeer(ctx context.Context, p peer.ID)
	RmPeer(ctx context.Context, p peer.ID)
	//SetPeers(peers []peer.ID)
}

// PinTracker represents a component which tracks the status of
// the pins in this cluster and ensures they are in sync with the
// IPFS daemon. This component should be thread safe.
type PinTracker interface {
	Component
	// Track tells the tracker that a Cid is now under its supervision
	// The tracker may decide to perform an IPFS pin.
	Track(context.Context, api.Pin) error
	// Untrack tells the tracker that a Cid is to be forgotten. The tracker
	// may perform an IPFS unpin operation.
	Untrack(context.Context, api.Cid) error
	// StatusAll returns the list of pins with their local status. Takes a
	// filter to specify which statuses to report.
	StatusAll(context.Context, api.TrackerStatus, chan<- api.PinInfo) error
	// Status returns the local status of a given Cid.
	Status(context.Context, api.Cid) api.PinInfo
	// RecoverAll calls Recover() for all pins tracked.
	RecoverAll(context.Context, chan<- api.PinInfo) error
	// Recover retriggers a Pin/Unpin operation in a Cids with error status.
	Recover(context.Context, api.Cid) (api.PinInfo, error)
	// PinQueueSize returns the current size of the pinning queue.
	PinQueueSize(context.Context) (int64, error)
}

// Informer provides Metric information from a peer. The metrics produced by
// informers are then passed to a PinAllocator which will use them to
// determine where to pin content. The metric is agnostic to the rest of
// Cluster.
type Informer interface {
	Component
	Name() string
	// GetMetrics returns the metrics obtained by this Informer.  It must
	// always return at least one metric.
	GetMetrics(context.Context) []api.Metric
}

// PinAllocator decides where to pin certain content. In order to make such
// decision, it receives the pin arguments, the peers which are currently
// allocated to the content and metrics available for all peers which could
// allocate the content.
type PinAllocator interface {
	Component
	// Allocate returns the list of peers that should be assigned to
	// Pin content in order of preference (from the most preferred to the
	// least). The "current" map contains valid metrics for peers
	// which are currently pinning the content. The candidates map
	// contains the metrics for all peers which are eligible for pinning
	// the content.
	Allocate(ctx context.Context, c api.Cid, current, candidates, priority api.MetricsSet) ([]peer.ID, error)
	// Metrics returns the list of metrics that the allocator needs.
	Metrics() []string
}

// PeerMonitor is a component in charge of publishing a peer's metrics and
// reading metrics from other peers in the cluster. The PinAllocator will
// use the metrics provided by the monitor as candidates for Pin allocations.
//
// The PeerMonitor component also provides an Alert channel which is signaled
// when a metric is no longer received and the monitor identifies it
// as a problem.
type PeerMonitor interface {
	Component
	// LogMetric stores a metric. It can be used to manually inject
	// a metric to a monitor.
	LogMetric(context.Context, api.Metric) error
	// PublishMetric sends a metric to the rest of the peers.
	// How to send it, and to who, is to be decided by the implementation.
	PublishMetric(context.Context, api.Metric) error
	// LatestMetrics returns a map with the latest valid metrics of matching
	// name for the current cluster peers. The result should only contain
	// one metric per peer at most.
	LatestMetrics(ctx context.Context, name string) []api.Metric
	// Returns the latest metric received from a peer. It may be expired.
	LatestForPeer(ctx context.Context, name string, pid peer.ID) api.Metric
	// MetricNames returns a list of metric names.
	MetricNames(ctx context.Context) []string
	// Alerts delivers alerts generated when this peer monitor detects
	// a problem (i.e. metrics not arriving as expected). Alerts can be used
	// to trigger self-healing measures or re-pinnings of content.
	Alerts() <-chan api.Alert
}

// Tracer implements Component as a way
// to shutdown and flush and remaining traces.
type Tracer interface {
	Component
}