PawSQLite/src/transaction.mjs

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JavaScript
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2021-03-01 18:47:07 -08:00
import { Result } from "./result.mjs";
import { PawSQLiteError } from "./pawsqlite_error.mjs";
export class Transaction {
constructor(dbName, adapter, enqueue, rollbackOnError=false) {
this.dbName = dbName;
this.adapter = adapter;
this._rollbackOnError = rollbackOnError;
this._enqueue = enqueue;
this._completeCb = null;
this._readyWait = null;
this._ready = false;
this._finalized = false;
}
async sql(sql, ...args) {
if (this._finalized) {
throw new PawSQLiteError("Transaction has already completed");
}
if (!this._ready) {
await this._waitUntilReady();
}
try {
return await this._executeSQL(sql, ...args);
} catch (e) {
if (this._rollbackOnError) {
await this.rollback();
}
throw e;
}
}
// Allow for slightly more complex parameter substitution.
// Instances of "???" will be replaced by the same number of comma-separated
// question marks as items in the corresponding nested parateter array
// eg. buildQuery("SELECT (???) FROM ?", [["col1", "col2"], "table1"])
// would output: ["SELECT (?, ?) FROM ?", ["col1", "col2", "table1"]]
buildQuery(sql, ...args) {
const parts = sql.split("???");
const subParamLengths = args
.filter(Array.isArray)
.map((a) => a.length);
if (parts.length !== subParamLengths.length + 1) {
throw new PawSQLiteError("Unable to build query: sub-" +
"paramters do not match sub-paramters in query");
}
const newQuery = parts.reduce((p1, p2, i) => {
const length = subParamLengths[i - 1];
return p1 + new Array(length).fill("?").join(", ") + p2;
});
const flatParams = args.reduce((acc, v) => {
if (Array.isArray(v)) {
Array.prototype.push.apply(acc, v);
} else {
acc.push(v);
}
return acc;
}, []);
return [newQuery, ...flatParams];
}
commit() {
return this._complete("COMMIT");
}
rollback() {
return this._complete("ROLLBACK");
}
async _waitUntilReady() {
if (!this._readyWait) {
this._readyWait = (async () => {
this._completeCb = await this._enqueue();
await this._begin();
this._ready = true;
})();
}
await this._readyWait;
}
async _executeSQL(sql, ...args) {
const reg = /^\s*(BEGIN|END|COMMIT|ROLLBACK)(?:[^A-Z]|$)/i;
const match = reg.exec(sql);
if (match) {
const statement = match[1].toUpperCase();
throw new PawSQLiteError("Manually managing transactions is " +
"forbidden. Found: \"" + statement + "\" statement.");
}
const result = await this.adapter.sql(this.dbName,
...this.buildQuery(sql, ...args));
return new Result(result);
}
async _begin() {
const result = await this.adapter.sql(this.dbName, "BEGIN");
}
async _complete(sql) {
if (this._finalized) {
throw new PawSQLiteError("Transaction has already completed");
}
this._finalized = true;
if (!this._readyWait) {
// Transaction was unused
return;
} else if (!this._ready) {
await this._waitUntilReady();
}
let result;
let error;
try {
result = await this.adapter.sql(this.dbName, sql);
} catch (e) {
error = e;
}
this._completeCb();
if (error) {
throw error;
}
return new Result(result);
}
}