Fuseji lookup (eg. マ○ドナ○ド)

[noatdk]

Summary

Adds support for looking up fuseji (伏せ字) (per #2436).

マ◯ド◯ルド    → マクドナルド
打〇込む      → 打ち込む
〇ち込む      → 打ち込む   (leading mask)
打ち込〇      → 打ち込む   (trailing mask)

Screenshots

[fuseji] anchor "マ" (prefix) skip-scan steps expr=323 read=300; 171 survivors -> 171 rows; scan 56.7ms, gets 6.0ms
[fuseji] "マ○ド」 は おそらく 「マッド" via prefix "マ": 171 match(es) in 64.30ms

[fuseji] anchor "マ" (prefix) skip-scan steps expr=337 read=315; 172 survivors -> 172 rows; scan 31.3ms, gets 6.0ms
[fuseji] "マ○ドナ○ドよりモスバーガ○のが" via prefix "マ": 172 match(es) in 37.70ms

[fuseji] anchor "マ" (prefix) skip-scan steps expr=2840 read=2720; 1031 survivors -> 1031 rows; scan 362.9ms, gets 34.0ms
[fuseji] "マ〇〇ド」 は おそらく 「マイ" via prefix "マ": 1031 match(es) in 399.90ms

[fuseji] anchor "お" (prefix) skip-scan steps expr=633 read=272; 256 survivors -> 256 rows; scan 59.1ms, gets 8.6ms
[fuseji] "お◯子" via prefix "お": 256 match(es) in 69.10ms

[fuseji] anchor "ちゃんとお .." (suffix) cursor scanned 0 keys; 0 survivors, scan 8.1ms
[fuseji] anchor "ちゃんとお ." (suffix) cursor scanned 0 keys; 0 survivors, scan 0.5ms
[fuseji] anchor "ちゃんとお " (suffix) cursor scanned 0 keys; 0 survivors, scan 2.5ms
[fuseji] anchor "ちゃんとお" (suffix) cursor scanned 0 keys; 0 survivors, scan 3.3ms
[fuseji] anchor "ちゃんと" (suffix) cursor scanned 7 keys; 0 survivors, scan 5.9ms
[fuseji] anchor "ちゃん" (suffix) cursor scanned 6139 keys; 1092 survivors -> 1092 rows; scan 1068.7ms, gets 60.2ms
[fuseji] "〇〇ちゃんとお ...Read " via suffix "ちゃん": 1092 match(es) in 1153.30ms

[fuseji] anchor "ちゃん•君」と呼" (suffix) cursor scanned 0 keys; 0 survivors, scan 4.4ms
[fuseji] anchor "ちゃん•君」と" (suffix) cursor scanned 0 keys; 0 survivors, scan 2.6ms
[fuseji] anchor "ちゃん•君」" (suffix) cursor scanned 0 keys; 0 survivors, scan 2.7ms
[fuseji] anchor "ちゃん•君" (suffix) cursor scanned 0 keys; 0 survivors, scan 1.3ms
[fuseji] anchor "ちゃん•" (suffix) cursor scanned 0 keys; 0 survivors, scan 0.9ms
[fuseji] anchor "ちゃん" (suffix) cursor scanned 6139 keys; 1092 survivors -> 1092 rows; scan 386.9ms, gets 49.6ms
[fuseji] "〇〇ちゃん•君」と呼ぶのは普通な" via suffix "ちゃん": 1092 match(es) in 451.10ms

Chrome, macOS, only PixivLight installed

How it works

Triggers are single-character wildcards. Since IndexedDB only does prefix scans, the lookup is anchored on the unmasked text:

1. Anchor on the unmasked run before the first trigger (prefix scan), or — if the text starts with a trigger — after the last trigger (suffix scan via the reversed indices).
2. Scan for matches. For a prefix anchor a skip-scan (loose index scan) walks the index driven by the masked pattern: it seeks straight to the required char at literal positions, lets the cursor enumerate only the chars that
   actually occur at mask positions, and skips subtrees that can't match — so cost scales with distinct mask-position characters + matches, not the size of the (low-selectivity) anchor range. Suffix anchors use a plain key cursor.
3. Build only the surviving records into entries, matching each against the pattern to record the matched length (code-point matcher, one wildcard per trigger).

Settings

Two new rows under Advanced translation settings:

• Enable fuseji lookup — translation.enableFusejiLookup (toggle, default false)
• Fuseji trigger characters — translation.fusejiTriggers (text, default ◯○〇●)

Trigger characters act as one-character wildcards during lookup; the default set covers the common circle variants used as masks.

Limitations

• Consecutive masks before a literal (e.g. マ◯◯ド) are slower and noisy: every word that fits the all-masked span counts as a partial match, so each extra adjacent trigger multiplies the number of results (and the time to build them).
• Deflection skipped. When the mask covers the stem (e.g. ◯んでる for 死んでる), the visible tail (んでる) is not a dictionary-form headword and the anchor we look up is the stripped tail, so it can't resolve to 死ぬ. Supporting it would require deinflecting the visible tail and reconstructing the pattern (◯んでる → ◯ぬ/◯む) before lookup.