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joplin/ReactNativeClient/lib/services/KvStore.js

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const BaseService = require('lib/services/BaseService.js');
const Mutex = require('async-mutex').Mutex;
class KvStore extends BaseService {
static instance() {
if (this.instance_) return this.instance_;
this.instance_ = new KvStore();
return this.instance_;
}
constructor() {
super();
this.incMutex_ = new Mutex();
}
setDb(v) {
this.db_ = v;
}
db() {
if (!this.db_) throw new Error('Accessing DB before it has been set!');
return this.db_;
}
typeFromValue_(value) {
if (typeof value === 'string') return KvStore.TYPE_TEXT;
if (typeof value === 'number') return KvStore.TYPE_INT;
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throw new Error(`Unsupported value type: ${typeof value}`);
}
formatValues_(kvs) {
const output = [];
for (const kv of kvs) {
kv.value = this.formatValue_(kv.value, kv.type);
output.push(kv);
}
return output;
}
formatValue_(value, type) {
if (type === KvStore.TYPE_INT) return Number(value);
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if (type === KvStore.TYPE_TEXT) return `${value}`;
throw new Error(`Unknown type: ${type}`);
}
async value(key) {
const r = await this.db().selectOne('SELECT `value`, `type` FROM key_values WHERE `key` = ?', [key]);
if (!r) return null;
return this.formatValue_(r.value, r.type);
}
async setValue(key, value) {
const t = Date.now();
await this.db().exec('INSERT OR REPLACE INTO key_values (`key`, `value`, `type`, `updated_time`) VALUES (?, ?, ?, ?)', [key, value, this.typeFromValue_(value), t]);
}
async deleteValue(key) {
await this.db().exec('DELETE FROM key_values WHERE `key` = ?', [key]);
}
async clear() {
await this.db().exec('DELETE FROM key_values');
}
async all() {
return this.formatValues_(await this.db().selectAll('SELECT * FROM key_values'));
}
// Note: atomicity is done at application level so two difference instances
// accessing the db at the same time could mess up the increment.
async incValue(key, inc = 1) {
const release = await this.incMutex_.acquire();
try {
const result = await this.db().selectOne('SELECT `value`, `type` FROM key_values WHERE `key` = ?', [key]);
const newValue = result ? this.formatValue_(result.value, result.type) + inc : inc;
await this.setValue(key, newValue);
release();
return newValue;
} catch (error) {
release();
throw error;
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}
}
async searchByPrefix(prefix) {
const results = await this.db().selectAll('SELECT `key`, `value`, `type` FROM key_values WHERE `key` LIKE ?', [`${prefix}%`]);
return this.formatValues_(results);
}
async countKeys() {
const r = await this.db().selectOne('SELECT count(*) as total FROM key_values');
return r.total ? r.total : 0;
}
}
KvStore.TYPE_INT = 1;
KvStore.TYPE_TEXT = 2;
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module.exports = KvStore;