// SPDX-License-Identifier: Apache-2.0
// Copyright Authors of Cilium

package kvstore

import (
	"context"
	"errors"
	"fmt"
	"sync"

	"github.com/spf13/pflag"

	"github.com/cilium/cilium/pkg/defaults"
	"github.com/cilium/cilium/pkg/hive"
	"github.com/cilium/cilium/pkg/hive/cell"
	"github.com/cilium/cilium/pkg/logging/logfields"
	"github.com/cilium/cilium/pkg/option"
	"github.com/cilium/cilium/pkg/promise"
	"github.com/cilium/cilium/pkg/time"
)

// Cell returns a cell which provides a promise for the global kvstore client.
// The parameter allows to customize the default backend, which can be either
// set to a specific value (e.g., in the case of clustermesh-apiserver) or
// left unset.
var Cell = func(defaultBackend string) cell.Cell {
	return cell.Module(
		"kvstore-client",
		"KVStore Client",

		cell.Config(config{
			KVStore:                    defaultBackend,
			KVStoreConnectivityTimeout: defaults.KVstoreConnectivityTimeout,
			KVStoreLeaseTTL:            defaults.KVstoreLeaseTTL,
			KVStorePeriodicSync:        defaults.KVstorePeriodicSync,
		}),

		cell.Provide(func(lc cell.Lifecycle, shutdowner hive.Shutdowner, cfg config, opts *ExtraOptions) promise.Promise[BackendOperations] {
			resolver, promise := promise.New[BackendOperations]()
			if cfg.KVStore == "" {
				log.Info("Skipping connection to kvstore, as not configured")
				resolver.Reject(errors.New("kvstore not configured"))
				return promise
			}

			// Propagate the options to the global variables for backward compatibility
			option.Config.KVStore = cfg.KVStore
			option.Config.KVStoreOpt = cfg.KVStoreOpt
			option.Config.KVstoreConnectivityTimeout = cfg.KVStoreConnectivityTimeout
			option.Config.KVstoreLeaseTTL = cfg.KVStoreLeaseTTL
			option.Config.KVstorePeriodicSync = cfg.KVStorePeriodicSync

			ctx, cancel := context.WithCancel(context.Background())
			var wg sync.WaitGroup

			lc.Append(cell.Hook{
				OnStart: func(cell.HookContext) error {
					wg.Add(1)
					go func() {
						defer wg.Done()

						log := log.WithField(logfields.BackendName, cfg.KVStore)
						log.Info("Establishing connection to kvstore")
						backend, errCh := NewClient(ctx, cfg.KVStore, cfg.KVStoreOpt, opts)

						if err, isErr := <-errCh; isErr {
							log.WithError(err).Error("Failed to establish connection to kvstore")
							resolver.Reject(fmt.Errorf("failed connecting to kvstore: %w", err))
							shutdowner.Shutdown(hive.ShutdownWithError(err))
							return
						}

						log.Info("Connection to kvstore successfully established")
						resolver.Resolve(backend)
					}()
					return nil
				},
				OnStop: func(cell.HookContext) error {
					cancel()
					wg.Wait()

					// We don't explicitly close the backend here, because that would
					// attempt to revoke the lease, causing all entries associated
					// with that lease to be deleted. This would not be the
					// behavior expected by the consumers of this cell.
					return nil
				},
			})

			return promise
		}),
	)
}

type config struct {
	KVStore                    string
	KVStoreOpt                 map[string]string
	KVStoreConnectivityTimeout time.Duration
	KVStoreLeaseTTL            time.Duration
	KVStorePeriodicSync        time.Duration
}

func (def config) Flags(flags *pflag.FlagSet) {
	flags.String(option.KVStore, def.KVStore, "Key-value store type")

	flags.StringToString(option.KVStoreOpt, def.KVStoreOpt,
		"Key-value store options e.g. etcd.address=127.0.0.1:4001")

	flags.Duration(option.KVstoreConnectivityTimeout, def.KVStoreConnectivityTimeout,
		"Time after which an incomplete kvstore operation is considered failed")

	flags.Duration(option.KVstoreLeaseTTL, def.KVStoreLeaseTTL,
		"Time-to-live for the KVstore lease.")
	flags.MarkHidden(option.KVstoreLeaseTTL)

	flags.Duration(option.KVstorePeriodicSync, def.KVStorePeriodicSync,
		"Periodic KVstore synchronization interval")
}

// GlobalUserMgmtClientPromiseCell provides a promise returning the global kvstore client to perform users
// management operations, once it has been initialized.
var GlobalUserMgmtClientPromiseCell = cell.Module(
	"global-kvstore-users-client",
	"Global KVStore Users Management Client Promise",

	cell.Provide(func(lc cell.Lifecycle, backendPromise promise.Promise[BackendOperations]) promise.Promise[BackendOperationsUserMgmt] {
		resolver, promise := promise.New[BackendOperationsUserMgmt]()
		ctx, cancel := context.WithCancel(context.Background())
		var wg sync.WaitGroup

		lc.Append(cell.Hook{
			OnStart: func(cell.HookContext) error {
				wg.Add(1)
				go func() {
					backend, err := backendPromise.Await(ctx)
					if err != nil {
						resolver.Reject(err)
					} else {
						resolver.Resolve(backend)
					}
					wg.Done()
				}()
				return nil
			},
			OnStop: func(cell.HookContext) error {
				cancel()
				wg.Wait()
				return nil
			},
		})

		return promise
	}),
)