// Copyright (c) 2012 The gocql Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gocql

import (
	"errors"
	"sync"
	"time"

	"github.com/gocql/gocql/internal/lru"
)

const defaultMaxPreparedStmts = 1000

//Package global reference to Prepared Statements LRU
var stmtsLRU preparedLRU

//preparedLRU is the prepared statement cache
type preparedLRU struct {
	sync.Mutex
	lru *lru.Cache
}

//Max adjusts the maximum size of the cache and cleans up the oldest records if
//the new max is lower than the previous value. Not concurrency safe.
func (p *preparedLRU) Max(max int) {
	for p.lru.Len() > max {
		p.lru.RemoveOldest()
	}
	p.lru.MaxEntries = max
}

func initStmtsLRU(max int) {
	if stmtsLRU.lru != nil {
		stmtsLRU.Max(max)
	} else {
		stmtsLRU.lru = lru.New(max)
	}
}

// To enable periodic node discovery enable DiscoverHosts in ClusterConfig
type DiscoveryConfig struct {
	// If not empty will filter all discoverred hosts to a single Data Centre (default: "")
	DcFilter string
	// If not empty will filter all discoverred hosts to a single Rack (default: "")
	RackFilter string
	// The interval to check for new hosts (default: 30s)
	Sleep time.Duration
}

// PoolConfig configures the connection pool used by the driver, it defaults to
// using a round robbin host selection policy and a round robbin connection selection
// policy for each host.
type PoolConfig struct {
	// HostSelectionPolicy sets the policy for selecting which host to use for a
	// given query (default: RoundRobinHostPolicy())
	HostSelectionPolicy HostSelectionPolicy

	// ConnSelectionPolicy sets the policy factory for selecting a connection to use for
	// each host for a query (default: RoundRobinConnPolicy())
	ConnSelectionPolicy func() ConnSelectionPolicy
}

func (p PoolConfig) buildPool(session *Session) (*policyConnPool, error) {
	hostSelection := p.HostSelectionPolicy
	if hostSelection == nil {
		hostSelection = RoundRobinHostPolicy()
	}

	connSelection := p.ConnSelectionPolicy
	if connSelection == nil {
		connSelection = RoundRobinConnPolicy()
	}

	return newPolicyConnPool(session, hostSelection, connSelection)
}

// ClusterConfig is a struct to configure the default cluster implementation
// of gocoql. It has a varity of attributes that can be used to modify the
// behavior to fit the most common use cases. Applications that requre a
// different setup must implement their own cluster.
type ClusterConfig struct {
	Hosts             []string          // addresses for the initial connections
	CQLVersion        string            // CQL version (default: 3.0.0)
	ProtoVersion      int               // version of the native protocol (default: 2)
	Timeout           time.Duration     // connection timeout (default: 600ms)
	Port              int               // port (default: 9042)
	Keyspace          string            // initial keyspace (optional)
	NumConns          int               // number of connections per host (default: 2)
	Consistency       Consistency       // default consistency level (default: Quorum)
	Compressor        Compressor        // compression algorithm (default: nil)
	Authenticator     Authenticator     // authenticator (default: nil)
	RetryPolicy       RetryPolicy       // Default retry policy to use for queries (default: 0)
	SocketKeepalive   time.Duration     // The keepalive period to use, enabled if > 0 (default: 0)
	DiscoverHosts     bool              // If set, gocql will attempt to automatically discover other members of the Cassandra cluster (default: false)
	MaxPreparedStmts  int               // Sets the maximum cache size for prepared statements globally for gocql (default: 1000)
	MaxRoutingKeyInfo int               // Sets the maximum cache size for query info about statements for each session (default: 1000)
	PageSize          int               // Default page size to use for created sessions (default: 5000)
	SerialConsistency SerialConsistency // Sets the consistency for the serial part of queries, values can be either SERIAL or LOCAL_SERIAL (default: unset)
	Discovery         DiscoveryConfig
	SslOpts           *SslOptions
	DefaultTimestamp  bool // Sends a client side timestamp for all requests which overrides the timestamp at which it arrives at the server. (default: true, only enabled for protocol 3 and above)
	// PoolConfig configures the underlying connection pool, allowing the
	// configuration of host selection and connection selection policies.
	PoolConfig PoolConfig

	// The maximum amount of time to wait for schema agreement in a cluster after
	// receiving a schema change frame. (deault: 60s)
	MaxWaitSchemaAgreement time.Duration

	// internal config for testing
	disableControlConn bool
}

// NewCluster generates a new config for the default cluster implementation.
func NewCluster(hosts ...string) *ClusterConfig {
	cfg := &ClusterConfig{
		Hosts:                  hosts,
		CQLVersion:             "3.0.0",
		ProtoVersion:           2,
		Timeout:                600 * time.Millisecond,
		Port:                   9042,
		NumConns:               2,
		Consistency:            Quorum,
		DiscoverHosts:          false,
		MaxPreparedStmts:       defaultMaxPreparedStmts,
		MaxRoutingKeyInfo:      1000,
		PageSize:               5000,
		DefaultTimestamp:       true,
		MaxWaitSchemaAgreement: 60 * time.Second,
	}
	return cfg
}

// CreateSession initializes the cluster based on this config and returns a
// session object that can be used to interact with the database.
func (cfg *ClusterConfig) CreateSession() (*Session, error) {
	return NewSession(*cfg)
}

var (
	ErrNoHosts              = errors.New("no hosts provided")
	ErrNoConnectionsStarted = errors.New("no connections were made when creating the session")
	ErrHostQueryFailed      = errors.New("unable to populate Hosts")
)