1 files changed, 96 insertions, 0 deletions
diff --git a/ext/js/language/deinflector.js b/ext/js/language/deinflector.js
new file mode 100644
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+++ b/ext/js/language/deinflector.js
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+/*
+ * Copyright (C) 2016-2021  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+class Deinflector {
+    constructor(reasons) {
+        this.reasons = Deinflector.normalizeReasons(reasons);
+    }
+
+    deinflect(source, rawSource) {
+        const results = [{
+            source,
+            rawSource,
+            term: source,
+            rules: 0,
+            reasons: [],
+            databaseDefinitions: []
+        }];
+        for (let i = 0; i < results.length; ++i) {
+            const {rules, term, reasons} = results[i];
+            for (const [reason, variants] of this.reasons) {
+                for (const [kanaIn, kanaOut, rulesIn, rulesOut] of variants) {
+                    if (
+                        (rules !== 0 && (rules & rulesIn) === 0) ||
+                        !term.endsWith(kanaIn) ||
+                        (term.length - kanaIn.length + kanaOut.length) <= 0
+                    ) {
+                        continue;
+                    }
+
+                    results.push({
+                        source,
+                        rawSource,
+                        term: term.substring(0, term.length - kanaIn.length) + kanaOut,
+                        rules: rulesOut,
+                        reasons: [reason, ...reasons],
+                        databaseDefinitions: []
+                    });
+                }
+            }
+        }
+        return results;
+    }
+
+    static normalizeReasons(reasons) {
+        const normalizedReasons = [];
+        for (const [reason, reasonInfo] of Object.entries(reasons)) {
+            const variants = [];
+            for (const {kanaIn, kanaOut, rulesIn, rulesOut} of reasonInfo) {
+                variants.push([
+                    kanaIn,
+                    kanaOut,
+                    Deinflector.rulesToRuleFlags(rulesIn),
+                    Deinflector.rulesToRuleFlags(rulesOut)
+                ]);
+            }
+            normalizedReasons.push([reason, variants]);
+        }
+        return normalizedReasons;
+    }
+
+    static rulesToRuleFlags(rules) {
+        const ruleTypes = Deinflector.ruleTypes;
+        let value = 0;
+        for (const rule of rules) {
+            const ruleBits = ruleTypes.get(rule);
+            if (typeof ruleBits === 'undefined') { continue; }
+            value |= ruleBits;
+        }
+        return value;
+    }
+}
+
+Deinflector.ruleTypes = new Map([
+    ['v1',    0b00000001], // Verb ichidan
+    ['v5',    0b00000010], // Verb godan
+    ['vs',    0b00000100], // Verb suru
+    ['vk',    0b00001000], // Verb kuru
+    ['vz',    0b00010000], // Verb zuru
+    ['adj-i', 0b00100000], // Adjective i
+    ['iru',   0b01000000] // Intermediate -iru endings for progressive or perfect tense
+]);