1 files changed, 50 insertions, 3 deletions

diff --git a/api/word.ts b/api/word.ts
index 4dad4a3..4c09cff 100644
--- a/api/word.ts
+++ b/api/word.ts
@@ -3,9 +3,48 @@ import APIBase from "./base.ts";
 import Japanese, { JapaneseFormatter } from "./japanese.ts";
 
 import "../util/string.ts";
-import { TagGroup } from "../search/tags.ts";
+import { Tag, TagGroup, TokenTags } from "../search/tags.ts";
 import { SearchWord } from "../search/types.ts";
 
+// irregular stems taken from <https://en.wikipedia.org/wiki/Japanese_irregular_verbs#suru_and_kuru>
+function irregularSuruStem(tags: TokenTags): string {
+	if (tags.anyOf([
+		Tag.Inflection.Polite.Masu,
+		Tag.Inflection.Suffix.Te,
+		Tag.Inflection.Tense.Past,
+		Tag.Inflection.Desirable.Itai, // part of Wikipedia's -ta form
+		Tag.Inflection.Negative,
+		Tag.Inflection.Desirable.Volitional,
+		Tag.Inflection.Command,
+	])) return "し";
+	if (tags.anyOf([
+		Tag.Inflection.Passive,
+		Tag.Inflection.Causative,
+	])) return "さ";
+	if (tags.anyOf([
+		Tag.Inflection.Potential,
+	])) return "でき";
+	return "す";
+}
+
+function irregularKuruStem(tags: TokenTags): string {
+	if (tags.anyOf([
+		Tag.Inflection.Polite.Masu,
+		Tag.Inflection.Suffix.Te,
+		Tag.Inflection.Tense.Past,
+		Tag.Inflection.Desirable.Itai, // part of Wikipedia's -ta form
+	])) return "き";
+	if (tags.anyOf([
+		Tag.Inflection.Negative,
+		Tag.Inflection.Desirable.Volitional,
+		Tag.Inflection.Passive,
+		Tag.Inflection.Causative,
+		Tag.Inflection.Potential,
+		Tag.Inflection.Command,
+	])) return "こ";
+	return "く";
+}
+
 export default class Word extends APIBase {
 	/** @prop dictionary form of verb if this word is a verb */
 	protected base: Japanese;
@@ -29,13 +68,21 @@ export default class Word extends APIBase {
 			input = input as SearchWord;
 			this.base = new Japanese(input.writing, input.reading);
 			if (input.tags.anyOf(TagGroup.Conjugable as string[])) {
+				// transfer conjugation from input.source to both dictionary reading and writing for furigana
 				var writingCommon = input.writing.cmpLen(input.source);
 				var readingCommon = input.reading.cmpLen(input.source);
 				var stemLength = Math.max(writingCommon, readingCommon);
 				var base = input[writingCommon > readingCommon ? "writing" : "reading"].substring(stemLength);
 				var conjugation = input.source.substring(stemLength);
-				this.text = new Japanese(input.writing.replaceLast(base, conjugation),
-																 input.reading.replaceLast(base, conjugation));
+	
+				// special reading for irregular verbs
+				var reading = input.reading;
+				if (input.writing == '来る') reading = irregularKuruStem(input.tags) + conjugation;
+				else if (input.writing == '為る') reading = irregularSuruStem(input.tags) + conjugation;
+				else reading = reading.replaceLast(base, conjugation);
+
+				// generate conjugated version of verb with kanji
+				this.text = new Japanese(input.writing.replaceLast(base, conjugation), reading);
 			} else {
 				this.text = this.base;
 			}