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authorpacien2022-10-24 19:39:41 +0200
committerpacien2022-10-24 19:39:41 +0200
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devdoc: describe the viewer's index as of v2.1
The viewer's internal tag indexing wasn't documented. This is a brief "reverse-engineering" of it accompanied with a few notes about its current issues. This constitutes some preliminary work before writing proper specification to clarify the otherwise undefined, dubious or conflicting behaviours.
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1---
2title: "Viewer: index v2.1"
3author: pacien
4date: 2022-10-22 (v2)
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: call notes
232. 2022-10-22: rewritten
24
25
26# Description of the current implementation
27
28## Generating the index(es) from the item tree
29
30The gallery item index (`index.json`) is loaded by the `galleryStore` and made
31available as the `galleryIndex` attribute.
32
33Two indexes are derived from that file through the `indexFactory` service:
34
35- `tagsIndex`:
36 - Maps each tag "part" (component) to items tagged with it.
37 - Maps the left-most disambiguating component to all components on its right.
38 - Includes a normalised version of the tag for searching.
39 - (Stores the left-most `rootPart` component. This is not used anywhere).
40
41- `tagsCategories`:
42 - Same as `tagsIndex`, but partitioned by tag category prefixes as defined in
43 the viewer configuration.
44
45
46## Search query input auto-completion "suggestions"
47
48The `TagInput` component suggests tags as the user types in that input field.
49
50This is provided by the `indexFactory.searchTags` function in fuzzy
51(non-strict) mode, which only uses the global tag index.
52
53The fuzzy search is implemented as a normalised (lowercase) infix word lookup,
54including the disambiguating tag parts.
55
56The auto-completion suggestions are independent of the current directory.
57Suggestions yielding no result (incompatible with the current search query) are
58not excluded either.
59
60
61## Item search
62
63The search query is stored in the URL query. This allows a search to be shared
64by copying the current URL.
65
66This URL search query is updated by `LayoutLeft.vue` to match modifications
67made through the tag input or related filters "propositions". This component
68also updates the store to match the URL query through `galleryStore.search`.
69
70A search query consists of three sets of tags: an intersection list, a forced
71inclusion (union) list, and a forced exclusion list. The last two are denoted
72with a `+` and `-` modifier prefix before the tag name. The order of the terms
73does not matter.
74
75The result computed in `indexSearch.indexSearch` is given by
76`(⋂(intersection) ∪ ⋃(forced inclusion)) ∖ ⋃(forced exclusion)`.
77
78The string representation of a query is parsed in `indexFactory`. It is
79serialised by taking the `filter.display` property of filters, in
80`LayouLeft.vue` for being displayed in the tag input and in the URL.
81
82
83## Related filters "propositions"
84
85The left pane of the user interface lists related filters "propositions",
86related to the current search results or directory being viewed.
87
88Tags in that pane are grouped according to the `tagCategories` gallery
89configuration key. (This is currently buggy: some tags can appear in the wrong
90category under some circumstances).
91
92The related tags are filtered with respect to the current search query or
93directory: only tags that are present on the listed items are shown.
94
95Each "proposed" tag has an occurrence count of the items having that tag in the
96whole gallery. (This is inconsistent with the locality of the filter).
97
98This is computed using a full gallery search through the `galleryStore` using
99`indexFactory.searchTags` in strict (non-fuzzy) mode.
100
101
102# Identified issues and proposals
103
104## Issues affecting the end users
105
106- Tags categories and disambiguation aren't properly defined:
107 - It is not clear whether intermediate tag components should be treated as
108 tags and suggested at all. (They currently are).
109
110- Tags with more than two components do not seem to be handled correctly:
111 - `a:b:c`: `c` is not registered as a child of `a` in `tagsIndex`.
112 - This seems to be the cause of tags being displayed in the wrong category in
113 the suggestion pane.
114
115- The tag input's auto-completion suggests impossible intersections:
116 - The fuzzy (non-strict) search does not work the same way as the suggestions
117 panel, which restricts the suggestions.
118 - This might however be problematic for forced inclusions (union) tags
119 which are still meaningful.
120
121- The tag occurrence counts in the related tags "propositions" pane is
122 misleading:
123 - This view suggests only the tags for the current search results
124 (descendants of the current directory and matching the current search query
125 if any),
126 - But the occurrence count for each tag is global (on the whole gallery
127 instead of the current search results).
128
129
130## Issues affecting only the developers
131
132- Ambiguous terminology:
133 - For example "index" vs "index.json", or "tag suggestions" vs
134 "tag propositions" vs "tag completion".
135 - This confusion is reflected in the component naming and coupling…
136 - A glossary and would help.
137 - Refactoring and renaming the modules would help.
138
139- Tight coupling of the tag-related and index operations:
140 - It goes all over the place.
141 - Some concerns should and can clearly be separated for example:
142 - For example query parsing, compiling and actual run on the item tree.
143 - The new modules should make use of composition with the rest of the
144 components.
145
146- Lack of unit tests:
147 - Coupling is preventing easy unit testing.
148 - Once the concerns are separated:
149 - We'll have clear expected outputs with respect to some input.
150 - It should be easier to do unit testing:
151 - (perhaps through randomised property testing).
152
153- Minor: relatively verbose and intertwined imperative code:
154 - The query parsing and recursive tree operations would probably be more
155 elegant in PureScript than Javascript/Typescript.
156 - Same with unit and property tests.