support UPDATE

Author: Snowflake107

src/jsql/Database.js

@@ -5,6 +5,7 @@ const handlers = {
     select: require('../util/methods/select'),
     insert: require('../util/methods/insert'),
     drop: require('../util/methods/drop'),
+    update: require('../util/methods/update'),
 };
 
 class Database {

src/util/Util.js

@@ -0,0 +1,7 @@
+module.exports = {
+    chunk: (arr, len) => {
+        const nm = [];
+        for (let i = 0; i < arr.length; i += len) nm.push(arr.slice(i, i + len));
+        return nm;
+    }
+};

src/util/methods/select.js

@@ -1,3 +1,5 @@
+const { chunk } = require("../Util");
+
 module.exports = (ast, db) => {
     if (ast.type.toLowerCase() !== 'select') throw new TypeError('invalid query type');
     const table = ast.from[0].table;
@@ -7,16 +9,10 @@ module.exports = (ast, db) => {
     if (!data) throw new Error(`Table \"${table}\" does not exist`);
 
     const fn = chunk(
-        data.data.map((m) => ({ id: m.key, data: m.data ?? null })),
+        data.data.map((m) => ({ key: m.key, data: m.data ?? null })),
         2
     );
 
     if (limit >= 0) return fn.slice(0, limit);
     return fn;
 };
-
-function chunk(arr, len) {
-    const nm = [];
-    for (let i = 0; i < arr.length; i += len) nm.push(arr.slice(i, i + len));
-    return nm;
-}

src/util/methods/update.js

@@ -0,0 +1,41 @@
+const { chunk } = require("../Util");
+
+module.exports = (ast, db) => {
+    if (ast.type.toLowerCase() !== 'update') throw new TypeError('invalid query type');
+    const table = ast.table[0].table;
+    const data = db.db;
+    if (!data[table]) throw new Error(`Table "${table}" does not exist`);
+    
+    const set = { col: ast.set[0].column, val: ast.set[0].value.value };
+    const point = { left: ast.where.left.value, op: ast.where.operator, right: ast.where.right.value, set };
+    if (!data[table].keys.some(x => x.column === set.col)) throw new Error(`Column "${set.col}" does not exists in table "${table}"`);
+    const bin = binOp(data[table], point);
+    if (bin.index < 0) return;
+
+    const dataAt = data[table].data[bin.index + bin.idx];
+    data[table].data.splice(bin.index + bin.idx, 1, {
+        ...dataAt,
+        data: set.val
+    });
+
+    db.write(data);
+}
+
+function binOp(data, clause) {
+    switch(clause.op) {
+        case "=":
+            const child = chunk(data.data, 2);
+            const fnx = m => m.key === clause.left && m.data === clause.right;
+            const fn = x => x.find(fnx);
+
+            try {
+                return {
+                    data: child.find(fn),
+                    index: child.findIndex(fn),
+                    idx: child.find(fn).findIndex(x => x.key === clause.set.col)
+                };
+            } catch {
+                throw new Error(`Could not verify operation "${clause.left} = ${clause.right}"`);
+            }
+    }
+}