Adding JavaScript sqlite apiserver example

apiserver_with_sqlite.js

@@ -0,0 +1,154 @@
+const express = require('express')
+const bodyParser = require('body-parser')
+const app = express()
+const sqlite3 = require('sqlite3').verbose()
+const port = 5000
+const db = new sqlite3.Database('counters.db')
+
+const make_table = "CREATE TABLE IF NOT EXISTS counters \
+                    (counter_name TEXT PRIMARY KEY, counter_value INTEGER)"
+
+const add_counter = "INSERT INTO counters VALUES (?, ?)"
+
+const get_all_counters = "SELECT * FROM counters"
+
+const increment_counter = "UPDATE counters \
+                            SET counter_value = (SELECT counter_value FROM counters WHERE counter_name = ?) + 1 \
+                            WHERE counter_name = ?"
+
+const decrement_counter = "UPDATE counters \
+                            SET counter_value = (SELECT counter_value FROM counters WHERE counter_name = ?) - 1\
+                            WHERE counter_name = ?"
+
+db.run(make_table)
+
+app.use(bodyParser.json())
+
+function rows_to_dict(rows) {
+    dictionary = {}
+
+    rows.forEach((row) => {
+        dictionary[row["counter_name"]] = row["counter_value"]
+    })
+
+    return dictionary
+}
+
+app.get("/counters", (req, res) => {
+    db.all(get_all_counters, (err, rows) => {
+        res.status(200).send({
+            'all_counters': rows_to_dict(rows)
+        })
+    })
+})
+
+app.post("/counters", (req, res) => {
+    if (req.headers['content-type'] == 'application/json') {
+        body = req.body;
+
+        if (!"new_counter_name" in Object.keys(body) || !"new_counter_starting_value" in Object.keys(body)) {
+            error_response = {
+                "status": "ERROR",
+                "reason": "Body for posting to /counters endpoint must contain both new_counter_name and new_counter_starting_value",
+                "input_body": body
+            }
+
+            res.status(400).send(error_response)
+            return
+        }
+
+        db.run(add_counter, body["new_counter_name"], body["new_counter_starting_value"])
+        res.status(200).send({'status': 'OK'})
+    } else {
+        error_response = {
+            "status": "ERROR",
+            "reason": "Content Type for endpoint /counters must be application/json"
+        }
+
+        res.status(400).send(error_response)
+    }
+})
+
+app.get("/counters/:counterName", (req, res) => {
+    db.all(get_all_counters, (err, rows) => {
+        counters = rows_to_dict(rows)
+
+        if (!req.params.counterName in Object.keys(counters)) {
+            error_response = {
+                "status": "ERROR",
+                "reason": `Counter name ${req.params.counterName} does not exist`
+            }
+    
+            res.status(404).send(error_response)
+            return
+        }
+    
+        data_response = {
+            'counter_name': req.params.counterName,
+            'counter_value': counters[req.params.counterName]
+        }
+    
+        res.status(200).send(data_response)
+    })
+    
+})
+
+app.post("/counters/:counterName/increment", (req, res) => {
+    db.all(get_all_counters, (err, rows) => {
+        counters = rows_to_dict(rows)
+
+        if (!req.params.counterName in Object.keys(counters)) {
+            error_response = {
+                "status": "ERROR",
+                "reason": `Counter name ${req.params.counterName} does not exist`
+            }
+    
+            res.status(404).send(error_response)
+            return
+        }
+    
+        data_response = {
+            'counter_name': req.params.counterName,
+            'old_value': counters[req.params.counterName],
+            'new_value': counters[req.params.counterName] + 1
+        }
+    
+        db.run(increment_counter, req.params.counterName, req.params.counterName)
+    
+        res.status(200).send(data_response)
+    })  
+})
+
+app.post("/counters/:counterName/decrement", (req, res) => {
+    db.all(get_all_counters, (err, rows) => {
+        counters = rows_to_dict(rows)
+
+        if (!req.params.counterName in Object.keys(counters)) {
+            error_response = {
+                "status": "ERROR",
+                "reason": `Counter name ${req.params.counterName} does not exist`
+            }
+    
+            res.status(404).send(error_response)
+            return
+        }
+    
+        data_response = {
+            'counter_name': req.params.counterName,
+            'old_value': counters[req.params.counterName],
+            'new_value': counters[req.params.counterName] - 1
+        }
+    
+        db.run(decrement_counter, req.params.counterName, req.params.counterName)
+    
+        res.status(200).send(data_response)
+    })  
+})
+
+app.listen(port, () => {
+    console.log(`Server is running on port ${port}`)
+})
+
+app.on("exit", () => {
+    db.close()
+})

package.json

@@ -14,6 +14,7 @@
   "description": "",
   "dependencies": {
     "body-parser": "^2.2.0",
-    "express": "^4.21.2"
+    "express": "^4.21.2",
+    "sqlite3": "^5.1.7"
   }
 }