src/model: introduce ModelIndex

[nit.git] / src / model / model_index.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# 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.

# Search things from the Model
#
# ModelIndex allows you to index mentities then retrieve them by their `name`
# or `full_name`.
# It offers a set of `find_*` methods that can be used to match queries
# against entities name.
#
# Because each use is different, ModelIndex only provide base raw search services.
# All of them return IndexMatches that can be ordered and filtered by the client.
#
# ## Indexing mentities
#
# Before searching something from the ModelIndex, you have to index it.
# Use the `ModelIndex::index` method to do that:
#
# ~~~nitish
# var index = new ModelIndex
#
# for mentity in model.private_view.mentities do
#       index.index(mentity)
# end
# ~~~
#
# ## Search mentities
#
# You can then run queries on the ModelIndex:
#
# ~~~nitish
# for res in index.find("Array").limit(10) do
#    print res
# end
# ~~~
#
# ## Examples
#
# Here some examples of how you can use the ModelIndex.
#
# ### Smart type prediction
#
# Use ModelIndex to implement a smart prediction system based on the typed prefix:
#
# ~~~nitish
# var index = new ModelIndex
#
# for mentity in model.private_view.mentities do
#       # We don't really care about definitions
#       if mentity isa MClassDef or mentity isa MPropDef then continue
#       index.index(mentity)
# end
#
# var typed_prefix = "Arr"
# for res in index.find_by_name_prefix(typed_prefix).
#       uniq. # keep only the best ranked mentity
#       limit(5). # limit to ten results
#       sort(new VisibilityComparator, new NameComparator) do # order by visibility then name
#    print res
# end
# ~~~
#
# Will output something like:
#
# ~~~raw
# Array (1)
# ArraySet (2)
# ArrayMap (3)
# ArrayCmp (4)
# ArrayMapKeys (5)
# ~~~
#
# ### Method autocompletion
#
# Find methods from a class full_name:
#
# ~~~nitish
# var class_full_name = "core::Array"
# for res in index.find_by_full_name_prefix("{class_full_name}::").
#       uniq. # keep only the best ranked mentity
#       sort(new VisibilityComparator). # put private in the bottom of the list
#       limit(5). # limit to ten results
#       sort(new FullNameComparator) do # order by lexicographic order
#    print res
# end
# ~~~
#
# Will output something like:
#
# ~~~raw
# * (2)
# + (1)
# filled_with (5)
# from (3)
# with_items (4)
# ~~~
#
# ### Name typo detection and suggestion
#
# Detect unknown names and suggest corrections:
#
# ~~~nitish
# var name = "Zrray"
#
# if index.find_by_name_prefix(name).is_empty then
#       printn "`{name}` not found, did you mean: "
#       printn index.find_by_name_similarity(name).sort(new ScoreComparator).limit(2).join(" or ")
#       print "?"
# end
# ~~~
#
# Will output something like:
#
# ~~~raw
# `Zrray` not found, did you mean: Array (1) or array (1)?
# ~~~
module model_index

import model::model_views
import trees::trie

# ModelIndex indexes mentities by their name and full name
#
# It provides methods to find mentities based on a prefix or string similarity.
#
# ~~~nitish
# # Build index
# var index = new ModelIndex
# for mentity in model.private_view.mentities do
#       if mentity isa MClassDef or mentity isa MPropDef then continue
#       index.index(mentity)
# end
#
# for e in index.find("Foo").uniq.sort(new ScoreComparator).limit(10) do
#       print " * {e.score}: {e.mentity.name} ({e.mentity.full_name})"
# end
# ~~~
class ModelIndex

        # List of all indexed mentities.
        #
        # Faster than traversing the tries.
        var mentities = new Array[MEntity]

        # Prefix tree for mentities `name`
        #
        # Because multiple mentities can share the same `name`, we use a Trie of
        # arrays of mentities.
        #
        # As for now, we do not index class and property definitions.
        # TODO add an option.
        var name_prefixes = new Trie[Array[MEntity]]

        # Prefix tree for mentities `full_name`
        #
        # Even if two mentities cannot share the same `full_name`, we use a Trie of
        # arrays of mentities to be consistent with `name_prefixes`.
        var full_name_prefixes = new Trie[Array[MEntity]]

        # Index `mentity` by it's `MEntity::name`
        #
        # See `name_prefixes`.
        private fun index_by_name(mentity: MEntity) do
                var name = mentity.name
                if not name_prefixes.has_key(name) then
                        name_prefixes[name] = new Array[MEntity]
                end
                name_prefixes[name].add mentity
        end

        # Index `mentity` by its `MEntity::full_name`
        private fun index_by_full_name(mentity: MEntity) do
                var name = mentity.full_name
                if not full_name_prefixes.has_key(name) then
                        full_name_prefixes[name] = new Array[MEntity]
                end
                full_name_prefixes[name].add mentity
        end

        # Index `mentity` so it can be retrieved by a find query
        #
        # MEntities are indexed by both name and full_name.
        fun index(mentity: MEntity) do
                mentities.add mentity
                index_by_name mentity
                index_by_full_name mentity
        end

        # Translate Trie results to `SearchResult`
        #
        # This method is used internally to translate each mentity returned by a prefix
        # match in a Trie into a SearchResult that can be ranked by score.
        #
        # Results from the Trie are returned in a breadth first manner so we get the
        # matches ordered by prefix.
        # We preserve that order by giving an incremental score to the `array` items.
        private fun score_results_incremental(array: Array[Array[MEntity]]): IndexMatches do
                var results = new IndexMatches
                var score = 1
                for mentities in array do
                        for mentity in mentities do
                                results.add new IndexMatch(mentity, score)
                        end
                        score += 1
                end
                return results
        end

        # Find all mentities where `MEntity::name` matches the `prefix`
        fun find_by_name_prefix(prefix: String): IndexMatches do
                return score_results_incremental(name_prefixes.find_by_prefix(prefix))
        end

        # Find all mentities where `MEntity::full_name` matches the `prefix`
        fun find_by_full_name_prefix(prefix: String): IndexMatches do
                return score_results_incremental(full_name_prefixes.find_by_prefix(prefix))
        end

        # Rank all mentities by the distance between `MEntity::name` and `name`
        #
        # Use the Levenshtein algorithm on all the indexed mentities `name`.
        # Warning: may not scale to large indexes.
        fun find_by_name_similarity(name: String): IndexMatches do
                var results = new IndexMatches
                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.name))
                end
                return results
        end

        # Rank all mentities by the distance between `MEntity::full_name` and `full_name`
        #
        # Use the Levenshtein algorithm on all the indexed mentities `full_name`.
        # Warning: may not scale to large indexes.
        fun find_by_full_name_similarity(name: String): IndexMatches do
                var results = new IndexMatches
                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.full_name))
                end
                return results
        end

        # Rank all mentities by the distance between `name` and both the mentity name and full name
        fun find_by_similarity(name: String): IndexMatches do
                var results = new IndexMatches
                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.name))
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.full_name))
                end
                return results
        end

        # Find mentities by name trying first by prefix then by similarity
        fun find_by_name(name: String): IndexMatches do
                var results = find_by_name_prefix(name)
                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.name))
                end
                return results
        end

        # Find mentities by full name trying firt by prefix then by similarity
        fun find_by_full_name(name: String): IndexMatches do
                var results = find_by_full_name_prefix(name)
                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.full_name))
                end
                return results
        end

        # Find all mentities that matches `name`
        #
        # 1. try by name prefix
        # 2. add full name prefix matches
        # 3. try similarity by name
        # 4. try similarity by full_name
        fun find(name: String): IndexMatches do
                var results = find_by_name_prefix(name)

                for result in find_by_full_name_prefix(name) do
                        results.add result
                end

                for mentity in mentities do
                        if mentity isa MClassDef or mentity isa MPropDef then continue
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.name))
                        results.add new IndexMatch(mentity, name.levenshtein_distance(mentity.full_name))
                end
                return results
        end
end

# An array of IndexMatch instances returned by the ModelIndex
#
# Index matches can be sorted, filtered and truncated.
#
# Thanks to the fluent interface, the index matches can be manipulated in chain
# from a model index query:
#
# ~~~nitish
# var res = index.find("Foo").
#   uniq.
#       sort(new ScoreComparator, new MEntityComparator).
#       limit(10).
#       sort(new VisibilityComparator)
# ~~~
class IndexMatches
        super Array[IndexMatch]

        # Create a new ModelMatches from an array of matches
        #
        # Elements are copied.
        init from_matches(matches: Array[IndexMatch]) do self.add_all matches

        # Sort the matches with `comparator` (or a list of comparators)
        #
        # Return a new IndexMatches instance with the sorted results.
        #
        # When more than one comparator is given, the comparators are applied in a
        # pipeline where the `n`th comparator is applied only if the `n-1`th comparator
        # returned 0.
        fun sort(comparator: ScoreComparator...): IndexMatches do
                var res = to_a
                if comparator.length == 1 then
                        comparator.first.sort res
                else
                        var comparators = new MatchComparators(comparator)
                        comparators.sort res
                end
                return new IndexMatches.from_matches(res)
        end

        # Limit the matches with `limit`
        #
        # Return a new IndexMatches instance with only the `limit` first matches.
        fun limit(limit: Int): IndexMatches do
                var res = new Array[IndexMatch]
                for match in self do
                        if res.length >= limit then break
                        res.add match
                end
                return new IndexMatches.from_matches(res)
        end

        # Remove doublons from the matches
        #
        # Preverse the lowest score of all the matches for a MEntity.
        fun uniq: IndexMatches do
                var scores = new HashMap[MEntity, IndexMatch]
                var res = new Array[IndexMatch]
                for match in self do
                        var mentity = match.mentity
                        if scores.has_key(mentity) then
                                var older = scores[mentity]
                                if match.score < older.score then older.score = match.score
                        else
                                scores[mentity] = match
                                res.add match
                        end
                end
                return new IndexMatches.from_matches(res)
        end

        # Reset score of each matches to follow `self` order
        #
        # Usefull when you need to apply one sorter over another.
        fun rerank: IndexMatches do
                var res = new IndexMatches
                for match in self do
                        res.add match
                        match.score = res.length
                end
                return res
        end

        # Aggregate the mentities for all the matches
        #
        # Preserve the match order.
        fun mentities: Array[MEntity] do
                var res = new Array[MEntity]
                for match in self do res.add match.mentity
                return res
        end
end

# An MEntity matched from a ModelIndex
#
# Each match has a `score`. The score should be seen as the distance of
# the match from the query. In other words, the lowest is the score, the more
# relevant is the match.
class IndexMatch
        super Comparable

        redef type OTHER: IndexMatch

        # MEntity matches
        var mentity: MEntity

        # Score allocated by the search method
        #
        # A lowest score means a more relevant match.
        #
        # Scores values are arbitrary, the meaning of `10` vs `2000` really depends
        # on the search method producing the match and the comparators used to sort
        # the matches.
        # The only universal rule is: low score = relevance.
        var score: Int is writable

        # By default matches are compared only on their score
        redef fun <=>(o) do return score <=> o.score

        redef fun to_s do return "{mentity} ({score})"
end

# Compare two matches by their score
#
# Since the score can be seen as a distance, we want the lowest score first.
class ScoreComparator
        super Comparator

        redef type COMPARED: IndexMatch

        redef fun compare(o1, o2) do return o1.score <=> o2.score
end

# A pipeline of comparators executed in inclusion order
#
# This class is used internally to agregate the behaviors of multiple comparators.
# Use `IndexMatches::sort(comparator...)` instead.
private class MatchComparators
        super ScoreComparator

        # Comparator to use in the array order
        var comparators: Array[ScoreComparator]

        # Compare with each comparator
        #
        # Return the compare value of the first one to return anything else than 0.
        redef fun compare(o1, o2) do
                for comparator in comparators do
                        var c = comparator.compare(o1, o2)
                        if c != 0 then return c
                end
                return 0
        end
end

# Compare two matches by their MEntity kind
#
# Usefull to order the mentities by kind in this order:
# packages, groups, modules and classes, properties.
class MEntityComparator
        super ScoreComparator

        # See `MEntity::compare_mentity`
        redef fun compare(o1, o2) do
                return o1.mentity.mentity_kind_rank <=> o2.mentity.mentity_kind_rank
        end
end

# Compare two matches by their MEntity visibility
#
# We reverse the original order so private is at the end of the list.
class VisibilityComparator
        super ScoreComparator

        redef fun compare(o1, o2) do return o2.mentity.visibility <=> o1.mentity.visibility
end

# Compare two matches by their name in lexicographic order
#
# Generally, for a same score, we want to put A before Z.
class NameComparator
        super ScoreComparator

        redef fun compare(o1, o2) do return o1.mentity.name <=> o2.mentity.name
end

# Compare two matches by their name length
class NameLengthComparator
        super ScoreComparator

        redef fun compare(o1, o2) do return o1.mentity.name.length <=> o2.mentity.name.length
end

# Compare two matches by their full_name in lexicographic order
#
# Generally, for a same score, we want to put A before Z.
class FullNameComparator
        super ScoreComparator

        redef fun compare(o1, o2) do return o1.mentity.full_name <=> o2.mentity.full_name
end

# Compare two matches by their full name length
class FullNameLengthComparator
        super ScoreComparator

        redef fun compare(o1, o2) do return o1.mentity.full_name.length <=> o2.mentity.full_name.length
end

redef class MEntity

        # Compare MEntity class kind
        #
        # Unknown kind have a virtually high score.
        private fun mentity_kind_rank: Int do return 10
end

redef class MPackage
        redef fun mentity_kind_rank do return 1
end

redef class MGroup
        redef fun mentity_kind_rank do return 2
end

redef class MModule
        redef fun mentity_kind_rank do return 3
end

redef class MClass
        redef fun mentity_kind_rank do return 4
end

redef class MClassDef
        redef fun mentity_kind_rank do return 5
end

redef class MProperty
        redef fun mentity_kind_rank do return 6
end

redef class MPropDef
        redef fun mentity_kind_rank do return 7
end