support DELETE

Author: Snowflake107

src/jsql/Database.js

@@ -6,6 +6,7 @@ const handlers = {
     insert: require('../util/methods/insert'),
     drop: require('../util/methods/drop'),
     update: require('../util/methods/update'),
+    delete: require("../util/methods/delete"),
 };
 
 class Database {

src/util/methods/delete.js

@@ -0,0 +1,39 @@
+const { chunk } = require("../Util");
+
+module.exports = (ast, db) => {
+    if (ast.type.toLowerCase() !== 'delete') throw new TypeError('invalid query type');
+    const table = ast.from[0].table;
+    const data = db.db;
+    if (!data[table]) throw new Error(`Table "${table}" does not exist`);
+
+    const point = { left: ast.where.left.value, op: ast.where.operator, right: ast.where.right.value };
+    if (!data[table].keys.some(x => x.column === point.left)) throw new Error(`Column "${set.col}" does not exists in table "${table}"`);
+    const bin = binOp(data[table], point);
+    if (bin.index < 0) return;
+
+    bin.data.forEach(d => {
+        data[table].data.splice(data[table].data.indexOf(d), 1);
+    });
+
+    db.write(data);
+}
+
+function binOp(data, clause) {
+    switch (clause.op) {
+        case "=":
+            const child = chunk(data.data, 2);
+            const fnx = m => m.key === clause.left && m.data === clause.right;
+            const fn = x => x.find(fnx);
+
+            try {
+                const data = child.find(fn);
+                if (!data) throw new Error(`Could not verify operation "${clause.left} = ${clause.right}"`);
+                return {
+                    data: data,
+                    index: child.findIndex(fn)
+                };
+            } catch {
+                throw new Error(`Could not verify operation "${clause.left} = ${clause.right}"`);
+            }
+    }
+}