add

pos-frontend/app/database.ts

@@ -1,4 +1,5 @@
-import pl from 'nodejs-polars'
+import pl, { DataFrame } from 'nodejs-polars'
+import fs from 'fs'
 
 export function test_x(params: any) {
   const fooSeries = pl.Series("foo", [1, 2, 3])
@@ -9,3 +10,57 @@ export function test_x(params: any) {
 
   let df = pl.readCSV("data/iris.csv")
 }
+
+class CSVDatabase {
+  private df: DataFrame | null = null
+  private filePath: string
+
+  constructor(filePath: string) {
+    this.filePath = filePath
+    this.loadCSV()
+  }
+
+  private loadCSV() {
+    fs.existsSync(this.filePath) ? this.df = pl.readCSV(this.filePath) : this.df = DataFrame([])
+  }
+
+  private saveCSV() {
+    if (this.df) {
+      fs.writeFileSync(this.filePath, this.df.writeCSV())
+    }
+  }
+
+  create(row: Record<string, any>) {
+    if (this.df) {
+      this.df = this.df.vstack(DataFrame([row]))
+      this.saveCSV()
+    }
+  }
+
+  read(filter: Record<string, any>) {
+    if (this.df) {
+      return this.df.filter(filter)
+    }
+    return null
+  }
+
+  update(filter: Record<string, any>, values: Record<string, any>) {
+    if (this.df) {
+      // this.df = this.df.withColumn(
+      //   Object.keys(values)[0],
+      //   this.df
+      //     .filter(filter)
+      //     .withColumn(Object.keys(values)[0], pl.lit(values[Object.keys(values)[0]]))
+      // )
+      this.saveCSV()
+    }
+  }
+
+  delete(filter: Record<string, any>) {
+    if (this.df) {
+      // should be filter Not
+      this.df = this.df.filter(filter)
+      this.saveCSV()
+    }
+  }
+}