halkyon/halkyon_learn_curator/README.md

# halkyon_learn_curator

Turns dictionary downloads into the dictionary files a Halkyon Learn server
loads. It reads each source with an adapter of its own and writes one format
for all of them, so a new source or language needs a new adapter, never a
change to the server or the app. It doesn't depend on Serverpod or the server.
It also makes the stroke files the app writes characters with (below).

## Making a dictionary file

JMdict in English, with the JLPT levels and example sentences on top:

1. Download `jmdict-examples-eng-<version>.json.tgz` from
   [jmdict-simplified's releases](https://github.com/scriptin/jmdict-simplified/releases)
   and unpack it: JMdict with Tatoeba's sentences (CC BY 2.0 FR) on the
   meanings they show. `jmdict-eng-<version>.json` works too, without them.
2. Download `original_data/n1.csv` … `n5.csv` from
   [yomitan-jlpt-vocab](https://github.com/stephenmk/yomitan-jlpt-vocab) into a
   folder.
3. Convert, in this package:

   ```sh
   dart run halkyon_learn_curator:curate jmdict \
     --input jmdict-examples-eng-3.6.2.json --jlpt jlpt/ \
     --output jmdict-en.jsonl.gz
   ```

   The whole of JMdict (about 219,000 entries) takes some 20 seconds and
   300 MB of memory: entries are read one at a time.

KANJIDIC2 in English, with the JLPT levels of its kanji, and the kana:

1. Download `kanjidic2.xml.gz` from
   [the EDRDG](https://www.edrdg.org/wiki/index.php/KANJIDIC_Project).
2. Download `kanji.json` from
   [kanji-data](https://github.com/davidluzgouveia/kanji-data): Jonathan
   Waller's JLPT levels by kanji (`jlpt_new`; nothing else is read).
3. Convert, in this package:

   ```sh
   dart run halkyon_learn_curator:curate kanjidic \
     --input kanjidic2.xml.gz --jlpt kanji.json \
     --output kanjidic-en.jsonl.gz
   ```

   About 12,800 characters, in some 5 seconds.

Put the files into the server's `dictionaries` folder. The server loads each on
its next start, and again whenever it changes (see the server's README).

## The format (`halkyon-dictionary`, version 1)

[JSON Lines](https://jsonlines.org/), gzipped when the name ends in `.gz`.

The **first line** says what the file holds:

| Field | |
|---|---|
| `format`, `formatVersion` | `"halkyon-dictionary"`, `1` |
| `kind` | `words` (a dictionary of words, JMdict) or `characters` (of the characters words are written in, KANJIDIC2). The app shows them apart. |
| `source`, `sourceVersion` | The source's name (`jmdict`) and version (`3.6.2 (2026-10-05)`). An instance holds one version of a source for each meaning language. |
| `language`, `glossLanguage` | BCP 47 tags: the words' language (`ja`) and the meanings' (`en`). |
| `license` | The data's licence, an SPDX identifier (`CC-BY-SA-4.0`). |
| `credits` | Everything it is drawn from: `name`, `by`, `license`, `url`. The app lists them where it credits its data sources. |

**Every further line** is an entry:

| Field | |
|---|---|
| `id` | Its id in the source; with the source and meaning language, it names the entry for good. |
| `headword`, `reading` | How the word is shown, and how it is read; no `reading` when the headword is its own (a word written in kana). |
| `labels` | What it can be picked by: `common`, `jlpt:n5` … `jlpt:n1` (later e.g. `hsk:3`, `topik:1`); for characters also the school grade (`grade:1` … `grade:6`, `grade:secondary` for the rest of the Jōyō kanji) and the script (`hiragana`, `katakana`). |
| `rank` | Its order among the source's entries, lower first; JMdict: N5 to N1 in their lists' order, then other common words, then the rest; KANJIDIC2: hiragana and katakana in the kana table's order, then kanji by JLPT level, then by school grade, then the rest, each by frequency. |
| `keys` | What a search matches, lower case: written forms, readings in their own script and romanised, meanings. Everything specific to a language happens here, so the server's search knows no language. |
| `looseKeys` | What a search matches after every `keys` match: spellings people type that aren't quite right (romaji with long vowels typed once, `sushi` for すうし). Left out when empty. |
| `entry` | The entry itself, as cards take it: `forms` and `readings` (`text`, `common`, the source's `tags`; for a reading the `forms` it belongs to), `senses` (`glosses`; the source's codes in `pos`, `misc`, `field`, `dialect`; `info`; the `forms` and `readings` a sense is limited to; `examples`, sentences using the word in that sense: `text`, the form it takes there, `ja`, the sentence, `en`, its translation, and the source's id, e.g. `tatoeba`). Lists are left out when empty. A character's: `meanings`; `on` and `kun`, its readings as KANJIDIC2 writes them (a kun reading's okurigana after a `.`, a dash where it attaches to others); `grade`, `strokes`, `frequency` (its place among the 2,500 most used in newspapers) and `jlpt` where it has them. A kana's: `romaji` and `script`. |

## The app's stroke files

How every kanji and kana is written comes from
[KanjiVG](https://kanjivg.tagaini.net) and is bundled with the app, so writing
works without a server. To update it, download `kanjivg-<date>.xml.gz` from
[KanjiVG's releases](https://github.com/KanjiVG/kanjivg/releases) and, in this
package:

```sh
dart run halkyon_learn_curator:curate kanjivg \
  --input kanjivg-20260714.xml.gz \
  --output ../halkyon_learn_flutter/assets/kanjivg
```

It writes one gzipped JSON file for every 256 code points that have any,
named by the code point's upper bits in hexadecimal (食, U+98DF, is in
`098.json.gz`; 94 files, 2.7 MB), so the app reads only the part it needs.
Each maps a character to its strokes (`s`, SVG paths in KanjiVG's 109 × 109
box, in the order they're written) and the components KanjiVG first splits it
into (`c`, when it has any). Then update the release named in the folder's
`ATTRIBUTION.md`.

## Adding a source

Write an adapter in `lib/src/sources/` that turns the source into the lines
above, with its credits and a sample of real data in `test/fixtures/` (and
where that comes from in `test/fixtures/README.md`); give it a command in
`bin/curate.dart`. Check the source's licence first, and that the instance may
pass its data on to the people using it.