package state

import (
	"fmt"
	"reflect"
	"strings"

	"github.com/hashicorp/go-memdb"

	"github.com/hashicorp/consul/agent/structs"
)

const (
	tableNodes           = "nodes"
	tableServices        = "services"
	tableChecks          = "checks"
	tableGatewayServices = "gateway-services"
	tableMeshTopology    = "mesh-topology"

	indexID          = "id"
	indexService     = "service"
	indexConnect     = "connect"
	indexKind        = "kind"
	indexStatus      = "status"
	indexNodeService = "node_service"
	indexNode        = "node"
	indexUpstream    = "upstream"
	indexDownstream  = "downstream"
	indexGateway     = "gateway"
)

// nodesTableSchema returns a new table schema used for storing struct.Node.
func nodesTableSchema() *memdb.TableSchema {
	return &memdb.TableSchema{
		Name: tableNodes,
		Indexes: map[string]*memdb.IndexSchema{
			indexID: {
				Name:         indexID,
				AllowMissing: false,
				Unique:       true,
				Indexer: indexerSingle{
					readIndex:  readIndex(indexFromNodeQuery),
					writeIndex: writeIndex(indexFromNode),
				},
			},
			"uuid": {
				Name:         "uuid",
				AllowMissing: true,
				Unique:       true,
				Indexer:      &memdb.UUIDFieldIndex{Field: "ID"},
			},
			"meta": {
				Name:         "meta",
				AllowMissing: true,
				Unique:       false,
				Indexer: &memdb.StringMapFieldIndex{
					Field:     "Meta",
					Lowercase: false,
				},
			},
		},
	}
}

// servicesTableSchema returns a new table schema used to store information
// about services.
func servicesTableSchema() *memdb.TableSchema {
	return &memdb.TableSchema{
		Name: tableServices,
		Indexes: map[string]*memdb.IndexSchema{
			indexID: {
				Name:         indexID,
				AllowMissing: false,
				Unique:       true,
				Indexer: indexerSingleWithPrefix{
					readIndex:   readIndex(indexFromNodeServiceQuery),
					writeIndex:  writeIndex(indexFromServiceNode),
					prefixIndex: prefixIndex(prefixIndexFromQuery),
				},
			},
			indexNode: {
				Name:         indexNode,
				AllowMissing: false,
				Unique:       false,
				Indexer: indexerSingle{
					readIndex:  readIndex(indexFromNodeQuery),
					writeIndex: writeIndex(indexFromNodeIdentity),
				},
			},
			indexService: {
				Name:         indexService,
				AllowMissing: true,
				Unique:       false,
				Indexer: &memdb.StringFieldIndex{
					Field:     "ServiceName",
					Lowercase: true,
				},
			},
			indexConnect: {
				Name:         indexConnect,
				AllowMissing: true,
				Unique:       false,
				Indexer:      &IndexConnectService{},
			},
			indexKind: {
				Name:         indexKind,
				AllowMissing: false,
				Unique:       false,
				Indexer:      &IndexServiceKind{},
			},
		},
	}
}

// checksTableSchema returns a new table schema used for storing and indexing
// health check information. Health checks have a number of different attributes
// we want to filter by, so this table is a bit more complex.
func checksTableSchema() *memdb.TableSchema {
	return &memdb.TableSchema{
		Name: tableChecks,
		Indexes: map[string]*memdb.IndexSchema{
			indexID: {
				Name:         indexID,
				AllowMissing: false,
				Unique:       true,
				Indexer: indexerSingleWithPrefix{
					readIndex:   readIndex(indexFromNodeCheckID),
					prefixIndex: prefixIndex(prefixIndexFromQuery),
					writeIndex:  writeIndex(indexFromHealthCheck),
				},
			},
			indexStatus: {
				Name:         indexStatus,
				AllowMissing: false,
				Unique:       false,
				Indexer: &memdb.StringFieldIndex{
					Field:     "Status",
					Lowercase: false,
				},
			},
			indexService: {
				Name:         indexService,
				AllowMissing: true,
				Unique:       false,
				Indexer: &memdb.StringFieldIndex{
					Field:     "ServiceName",
					Lowercase: true,
				},
			},
			indexNode: {
				Name:         indexNode,
				AllowMissing: true,
				Unique:       false,
				Indexer: indexerSingle{
					readIndex:  readIndex(indexFromNodeQuery),
					writeIndex: writeIndex(indexFromNodeIdentity),
				},
			},
			indexNodeService: {
				Name:         indexNodeService,
				AllowMissing: true,
				Unique:       false,
				Indexer: indexerSingle{
					readIndex:  readIndex(indexFromNodeServiceQuery),
					writeIndex: writeIndex(indexNodeServiceFromHealthCheck),
				},
			},
		},
	}
}

//  gatewayServicesTableSchema returns a new table schema used to store information
// about services associated with terminating gateways.
func gatewayServicesTableSchema() *memdb.TableSchema {
	return &memdb.TableSchema{
		Name: tableGatewayServices,
		Indexes: map[string]*memdb.IndexSchema{
			indexID: {
				Name:         indexID,
				AllowMissing: false,
				Unique:       true,
				Indexer: &memdb.CompoundIndex{
					Indexes: []memdb.Indexer{
						&ServiceNameIndex{
							Field: "Gateway",
						},
						&ServiceNameIndex{
							Field: "Service",
						},
						&memdb.IntFieldIndex{
							Field: "Port",
						},
					},
				},
			},
			indexGateway: {
				Name:         indexGateway,
				AllowMissing: false,
				Unique:       false,
				Indexer: &ServiceNameIndex{
					Field: "Gateway",
				},
			},
			indexService: {
				Name:         indexService,
				AllowMissing: true,
				Unique:       false,
				Indexer: &ServiceNameIndex{
					Field: "Service",
				},
			},
		},
	}
}

// meshTopologyTableSchema returns a new table schema used to store information
// relating upstream and downstream services
func meshTopologyTableSchema() *memdb.TableSchema {
	return &memdb.TableSchema{
		Name: tableMeshTopology,
		Indexes: map[string]*memdb.IndexSchema{
			indexID: {
				Name:         indexID,
				AllowMissing: false,
				Unique:       true,
				Indexer: &memdb.CompoundIndex{
					Indexes: []memdb.Indexer{
						&ServiceNameIndex{
							Field: "Upstream",
						},
						&ServiceNameIndex{
							Field: "Downstream",
						},
					},
				},
			},
			indexUpstream: {
				Name:         indexUpstream,
				AllowMissing: true,
				Unique:       false,
				Indexer: &ServiceNameIndex{
					Field: "Upstream",
				},
			},
			indexDownstream: {
				Name:         indexDownstream,
				AllowMissing: false,
				Unique:       false,
				Indexer: &ServiceNameIndex{
					Field: "Downstream",
				},
			},
		},
	}
}

type ServiceNameIndex struct {
	Field string
}

func (index *ServiceNameIndex) FromObject(obj interface{}) (bool, []byte, error) {
	v := reflect.ValueOf(obj)
	v = reflect.Indirect(v) // Dereference the pointer if any

	fv := v.FieldByName(index.Field)
	isPtr := fv.Kind() == reflect.Ptr
	fv = reflect.Indirect(fv)
	if !isPtr && !fv.IsValid() || !fv.CanInterface() {
		return false, nil,
			fmt.Errorf("field '%s' for %#v is invalid %v ", index.Field, obj, isPtr)
	}

	name, ok := fv.Interface().(structs.ServiceName)
	if !ok {
		return false, nil, fmt.Errorf("Field 'ServiceName' is not of type structs.ServiceName")
	}

	// Enforce lowercase and add null character as terminator
	id := strings.ToLower(name.String()) + "\x00"

	return true, []byte(id), nil
}

func (index *ServiceNameIndex) FromArgs(args ...interface{}) ([]byte, error) {
	if len(args) != 1 {
		return nil, fmt.Errorf("must provide only a single argument")
	}
	name, ok := args[0].(structs.ServiceName)
	if !ok {
		return nil, fmt.Errorf("argument must be of type structs.ServiceName: %#v", args[0])
	}

	// Enforce lowercase and add null character as terminator
	id := strings.ToLower(name.String()) + "\x00"

	return []byte(strings.ToLower(id)), nil
}

func (index *ServiceNameIndex) PrefixFromArgs(args ...interface{}) ([]byte, error) {
	val, err := index.FromArgs(args...)
	if err != nil {
		return nil, err
	}

	// Strip the null terminator, the rest is a prefix
	n := len(val)
	if n > 0 {
		return val[:n-1], nil
	}
	return val, nil
}

// upstreamDownstream pairs come from individual proxy registrations, which can be updated independently.
type upstreamDownstream struct {
	Upstream   structs.ServiceName
	Downstream structs.ServiceName

	// Refs stores the registrations that contain this pairing.
	// When there are no remaining Refs, the upstreamDownstream can be deleted.
	//
	// Note: This map must be treated as immutable when accessed in MemDB.
	//       The entire upstreamDownstream structure must be deep copied on updates.
	Refs map[string]struct{}

	structs.RaftIndex
}

// NodeCheckQuery is used to query the ID index of the checks table.
type NodeCheckQuery struct {
	Node    string
	CheckID string
	structs.EnterpriseMeta
}