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1---
2title: "Viewer: index v2.1"
3author: pacien
4date: 2022-10-25 (v3)
5---
6
7# Abstract
8
9This is a short documentation of the viewer's internal index dating from the
10first version of this software and still currently in use in version 2.1.
11
12This index was written without proper specifications or documentation, and has
13evolved a lot since then.
14
15This document is an attempt at describing how this index is currently being
16generated and used, before further work can be done on some proper
17specification to clarify the problematic behaviours.
18
19
20# Document version history
21
221. 2022-10-15 by pacien: call notes
232. 2022-10-22 by pacien: rewritten
243. 2022-10-25 by pacien: include feedbacks from zeroinformatique
25
26
27# Description of the current implementation
28
29## Generating the index(es) from the item tree
30
31The gallery item index (`index.json`) is loaded by the `galleryStore` and made
32available as the `galleryIndex` attribute.
33
34Two indexes are derived from that file through the `indexFactory` service:
35
36- `tagsIndex`:
37 - Maps each tag "part" (component) to items tagged with it.
38 - Maps tags to their immediately preceding disambiguating component as child.
39 - Includes a normalised version of the tag for searching.
40 - Stores the `childPart`, used to generate tag categories indexes.
41 - (Stores the left-most `rootPart` component. This is not used anywhere).
42
43- `tagsCategories`:
44 - Same as `tagsIndex`, but partitioned by tag category prefixes as defined in
45 the viewer configuration.
46
47
48## Search query input auto-completion "suggestions"
49
50The `TagInput` component suggests tags as the user types in that input field.
51
52This is provided by the `indexFactory.searchTags` function in fuzzy
53(non-strict) mode, which only uses the global tag index.
54
55The fuzzy search is implemented as a normalised (lowercase) infix word lookup,
56including the disambiguating tag parts.
57
58The auto-completion suggestions are independent of the current directory.
59Suggestions yielding no result (incompatible with the current search query) are
60not excluded either. The current implementation makes the choice of suggesting
61everything because the current index does not allow finer filtering, and
62because walking the whole item tree may lead to performance issues.
63
64
65## Item search
66
67The search query is stored in the URL query. This allows a search to be shared
68by copying the current URL.
69
70This URL search query is updated by `LayoutLeft.vue` to match modifications
71made through the tag input or related filters "propositions". This component
72also updates the store to match the URL query through `galleryStore.search`.
73
74A search query consists of three sets of tags: an intersection list, a forced
75inclusion (union) list, and a forced exclusion list. The last two are denoted
76with a `+` and `-` modifier prefix before the tag name. The order of the terms
77does not matter.
78
79The result computed in `indexSearch.indexSearch` is given by
80`(⋂(intersection) ∪ ⋃(forced inclusion)) ∖ ⋃(forced exclusion)`.
81
82The string representation of a query is parsed in `indexFactory`. It is
83serialised by taking the `filter.display` property of filters, in
84`LayouLeft.vue` for being displayed in the tag input and in the URL.
85
86
87## Related filters "propositions"
88
89The left pane of the user interface lists related filters "propositions",
90related to the current search results or directory being viewed.
91
92Tags in that pane are grouped according to the `tagCategories` gallery
93configuration key. (This is currently buggy: some tags can appear in the wrong
94category under some circumstances).
95
96The related tags are filtered with respect to the current search query or
97directory: only tags that are present on the listed items are shown.
98
99Each "proposed" tag has an occurrence count of the items having that tag in the
100whole gallery. (This is inconsistent with the locality of the filter).
101
102This is computed using a full gallery search through the `galleryStore` using
103`indexFactory.searchTags` in strict (non-fuzzy) mode.
104
105
106# Identified issues and proposals
107
108## Issues affecting the end users
109
110- Tags categories and disambiguation aren't properly defined:
111 - It is not clear whether intermediate tag components should be treated as
112 tags and suggested at all. (They currently are).
113
114- Tags with indirect disambiguations are not handled correctly:
115 - Example in `a:b:c`:
116 - `b` is a child of `a`, `c` is a child of `b`.
117 - But `c` is not registered as a child of `a` in `tagsIndex`.
118
119- Homonymous disambiguated tags are not handled in separate categories.
120 - Example with `a` and `b:a`:
121 - `a` seems to be shown under category `b`.
122 - This seems to be the cause of tags being displayed in the wrong category in
123 the suggestion pane.
124
125- The tag input's auto-completion suggests impossible intersections:
126 - The fuzzy (non-strict) search does not work the same way as the suggestions
127 panel, which restricts the suggestions.
128 - This might however be problematic for forced inclusions (union) tags
129 which are still meaningful.
130 - They could still be listed but greyed for example.
131
132- The tag occurrence counts in the related tags "propositions" pane is
133 misleading:
134 - This view suggests only the tags for the current search results
135 (descendants of the current directory and matching the current search query
136 if any),
137 - But the occurrence count for each tag is global (on the whole gallery
138 instead of the current search results).
139
140
141## Issues affecting only the developers
142
143- Ambiguous terminology:
144 - For example "index" vs "index.json", or "tag suggestions" vs
145 "tag propositions" vs "tag completion".
146 - This confusion is reflected in the component naming and coupling…
147 - A glossary and would help.
148 - Refactoring and renaming the modules would help.
149
150- Tight coupling of the tag-related and index operations:
151 - It goes all over the place.
152 - Some concerns should and can clearly be separated for example:
153 - For example query parsing, compiling and actual run on the item tree.
154 - The new modules should make use of composition with the rest of the
155 components.
156
157- Lack of unit tests:
158 - Coupling is preventing easy unit testing.
159 - Once the concerns are separated:
160 - We'll have clear expected outputs with respect to some input.
161 - It should be easier to do unit testing:
162 - (perhaps through randomised property testing).
163
164- Minor: relatively verbose and intertwined imperative code:
165 - The query parsing and recursive tree operations would probably be more
166 elegant in PureScript than Javascript/Typescript.
167 - Same with unit and property tests.