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// Copyright 2019 The Hugo Authors. All rights reserved.
//
// 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
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package related holds code to help finding related content.
package related
import (
"errors"
"fmt"
"math"
"sort"
"strings"
"time"
"github.com/gohugoio/hugo/common/maps"
"github.com/gohugoio/hugo/common/types"
"github.com/mitchellh/mapstructure"
)
var (
_ Keyword = (*StringKeyword)(nil)
zeroDate = time.Time{}
// DefaultConfig is the default related config.
DefaultConfig = Config{
Threshold: 80,
Indices: IndexConfigs{
IndexConfig{Name: "keywords", Weight: 100},
IndexConfig{Name: "date", Weight: 10},
},
}
)
/*
Config is the top level configuration element used to configure how to retrieve
related content in Hugo.
An example site config.toml:
[related]
threshold = 1
[[related.indices]]
name = "keywords"
weight = 200
[[related.indices]]
name = "tags"
weight = 100
[[related.indices]]
name = "date"
weight = 1
pattern = "2006"
*/
type Config struct {
// Only include matches >= threshold, a normalized rank between 0 and 100.
Threshold int
// To get stable "See also" sections we, by default, exclude newer related pages.
IncludeNewer bool
// Will lower case all string values and queries to the indices.
// May get better results, but at a slight performance cost.
ToLower bool
Indices IndexConfigs
}
// Add adds a given index.
func (c *Config) Add(index IndexConfig) {
if c.ToLower {
index.ToLower = true
}
c.Indices = append(c.Indices, index)
}
// IndexConfigs holds a set of index configurations.
type IndexConfigs []IndexConfig
// IndexConfig configures an index.
type IndexConfig struct {
// The index name. This directly maps to a field or Param name.
Name string
// Contextual pattern used to convert the Param value into a string.
// Currently only used for dates. Can be used to, say, bump posts in the same
// time frame when searching for related documents.
// For dates it follows Go's time.Format patterns, i.e.
// "2006" for YYYY and "200601" for YYYYMM.
Pattern string
// This field's weight when doing multi-index searches. Higher is "better".
Weight int
// Will lower case all string values in and queries tothis index.
// May get better accurate results, but at a slight performance cost.
ToLower bool
}
// Document is the interface an indexable document in Hugo must fulfill.
type Document interface {
// RelatedKeywords returns a list of keywords for the given index config.
RelatedKeywords(cfg IndexConfig) ([]Keyword, error)
// When this document was or will be published.
PublishDate() time.Time
// Name is used as an tiebreaker if both Weight and PublishDate are
// the same.
Name() string
}
// InvertedIndex holds an inverted index, also sometimes named posting list, which
// lists, for every possible search term, the documents that contain that term.
type InvertedIndex struct {
cfg Config
index map[string]map[Keyword][]Document
minWeight int
maxWeight int
}
func (idx *InvertedIndex) getIndexCfg(name string) (IndexConfig, bool) {
for _, conf := range idx.cfg.Indices {
if conf.Name == name {
return conf, true
}
}
return IndexConfig{}, false
}
// NewInvertedIndex creates a new InvertedIndex.
// Documents to index must be added in Add.
func NewInvertedIndex(cfg Config) *InvertedIndex {
idx := &InvertedIndex{index: make(map[string]map[Keyword][]Document), cfg: cfg}
for _, conf := range cfg.Indices {
idx.index[conf.Name] = make(map[Keyword][]Document)
if conf.Weight < idx.minWeight {
// By default, the weight scale starts at 0, but we allow
// negative weights.
idx.minWeight = conf.Weight
}
if conf.Weight > idx.maxWeight {
idx.maxWeight = conf.Weight
}
}
return idx
}
// Add documents to the inverted index.
// The value must support == and !=.
func (idx *InvertedIndex) Add(docs ...Document) error {
var err error
for _, config := range idx.cfg.Indices {
if config.Weight == 0 {
// Disabled
continue
}
setm := idx.index[config.Name]
for _, doc := range docs {
var words []Keyword
words, err = doc.RelatedKeywords(config)
if err != nil {
continue
}
for _, keyword := range words {
setm[keyword] = append(setm[keyword], doc)
}
}
}
return err
}
// queryElement holds the index name and keywords that can be used to compose a
// search for related content.
type queryElement struct {
Index string
Keywords []Keyword
}
func newQueryElement(index string, keywords ...Keyword) queryElement {
return queryElement{Index: index, Keywords: keywords}
}
type ranks []*rank
type rank struct {
Doc Document
Weight int
Matches int
}
func (r *rank) addWeight(w int) {
r.Weight += w
r.Matches++
}
func newRank(doc Document, weight int) *rank {
return &rank{Doc: doc, Weight: weight, Matches: 1}
}
func (r ranks) Len() int { return len(r) }
func (r ranks) Swap(i, j int) { r[i], r[j] = r[j], r[i] }
func (r ranks) Less(i, j int) bool {
if r[i].Weight == r[j].Weight {
if r[i].Doc.PublishDate() == r[j].Doc.PublishDate() {
return r[i].Doc.Name() < r[j].Doc.Name()
}
return r[i].Doc.PublishDate().After(r[j].Doc.PublishDate())
}
return r[i].Weight > r[j].Weight
}
// SearchDoc finds the documents matching any of the keywords in the given indices
// against the given document.
// The resulting document set will be sorted according to number of matches
// and the index weights, and any matches with a rank below the configured
// threshold (
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