searcher.go

// Copyright 2023 Google LLC
//
// 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 main

import (
	"context"
	"sort"
	"strings"

	"github.com/ServiceWeaver/weaver"
	"golang.org/x/exp/slices"
)

// Searcher is an emoji search engine component.
type Searcher interface {
	// Search returns the set of emojis that match the provided query.
	Search(context.Context, string) ([]string, error)
}

// searcher is the implementation of the Searcher component.
type searcher struct {
	weaver.Implements[Searcher]
}

func (s *searcher) Search(ctx context.Context, query string) ([]string, error) {
	s.Logger(ctx).Debug("Search", "query", query)

	// Perform the search. First, we lowercase the query and split it into
	// words. For example, the query "Black cat" is tokenized to the words
	// "black" and "cat". Then, we say an emoji matches a query if every word
	// in the query is one of the emoji's labels.
	//
	// For example, the cat emoji has labels ["animal", "cat"]. It does NOT
	// match the "Black cat" query because "black" is not a label. The black
	// cat emoji, on the other hand, has labels ["animal", "black", "cat"] and
	// therefore does match the query "Black cat".
	//
	// We iterate over all emojis and return the ones that match the query.
	words := strings.Fields(strings.ToLower(query))
	results := []string{}
	for emoji, labels := range emojis {
		if matches(labels, words) {
			results = append(results, emoji)
		}
	}
	sort.Strings(results)
	return results, nil
}

// matches returns whether words is a subset of labels.
func matches(labels, words []string) bool {
	for _, word := range words {
		if !slices.Contains(labels, word) {
			return false
		}
	}
	return true
}