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vendor/go.mongodb.org/mongo-driver/mongo/readpref/readpref.go

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+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package readpref // import "go.mongodb.org/mongo-driver/mongo/readpref"
+
+import (
+	"errors"
+	"time"
+
+	"go.mongodb.org/mongo-driver/tag"
+)
+
+var (
+	errInvalidReadPreference = errors.New("can not specify tags or max staleness on primary")
+)
+
+var primary = ReadPref{mode: PrimaryMode}
+
+// Primary constructs a read preference with a PrimaryMode.
+func Primary() *ReadPref {
+	return &primary
+}
+
+// PrimaryPreferred constructs a read preference with a PrimaryPreferredMode.
+func PrimaryPreferred(opts ...Option) *ReadPref {
+	// New only returns an error with a mode of Primary
+	rp, _ := New(PrimaryPreferredMode, opts...)
+	return rp
+}
+
+// SecondaryPreferred constructs a read preference with a SecondaryPreferredMode.
+func SecondaryPreferred(opts ...Option) *ReadPref {
+	// New only returns an error with a mode of Primary
+	rp, _ := New(SecondaryPreferredMode, opts...)
+	return rp
+}
+
+// Secondary constructs a read preference with a SecondaryMode.
+func Secondary(opts ...Option) *ReadPref {
+	// New only returns an error with a mode of Primary
+	rp, _ := New(SecondaryMode, opts...)
+	return rp
+}
+
+// Nearest constructs a read preference with a NearestMode.
+func Nearest(opts ...Option) *ReadPref {
+	// New only returns an error with a mode of Primary
+	rp, _ := New(NearestMode, opts...)
+	return rp
+}
+
+// New creates a new ReadPref.
+func New(mode Mode, opts ...Option) (*ReadPref, error) {
+	rp := &ReadPref{
+		mode: mode,
+	}
+
+	if mode == PrimaryMode && len(opts) != 0 {
+		return nil, errInvalidReadPreference
+	}
+
+	for _, opt := range opts {
+		err := opt(rp)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return rp, nil
+}
+
+// ReadPref determines which servers are considered suitable for read operations.
+type ReadPref struct {
+	maxStaleness    time.Duration
+	maxStalenessSet bool
+	mode            Mode
+	tagSets         []tag.Set
+}
+
+// MaxStaleness is the maximum amount of time to allow
+// a server to be considered eligible for selection. The
+// second return value indicates if this value has been set.
+func (r *ReadPref) MaxStaleness() (time.Duration, bool) {
+	return r.maxStaleness, r.maxStalenessSet
+}
+
+// Mode indicates the mode of the read preference.
+func (r *ReadPref) Mode() Mode {
+	return r.mode
+}
+
+// TagSets are multiple tag sets indicating
+// which servers should be considered.
+func (r *ReadPref) TagSets() []tag.Set {
+	return r.tagSets
+}