add the visitor API endpoint

api/database/database.go

@@ -17,6 +17,18 @@ func (db *Type) Load() (err error) {
 		return fmt.Errorf("cannot access the database: %s", err.Error())
 	}
 
+	// see database/visitor.go
+	_, err = db.sql.Exec(`
+    CREATE TABLE IF NOT EXISTS visitor_count(
+      id    TEXT NOT NULL UNIQUE,
+      count INTEGER NOT NULL
+    );
+  `)
+
+	if err != nil {
+		return fmt.Errorf("failed to create the visitor_count table: %s", err.Error())
+	}
+
 	// see database/service.go
 	_, err = db.sql.Exec(`
     CREATE TABLE IF NOT EXISTS services(

api/database/visitor.go

@@ -0,0 +1,48 @@
+package database
+
+import (
+	"database/sql"
+)
+
+func (db *Type) VisitorGet() (uint64, error) {
+	var (
+		row   *sql.Row
+		count uint64
+		err   error
+	)
+
+	if row = db.sql.QueryRow("SELECT count FROM visitor_count WHERE id = 0"); row == nil {
+		return 0, nil
+	}
+
+	if err = row.Scan(&count); err != nil && err != sql.ErrNoRows {
+		return 0, err
+	}
+
+	if err == sql.ErrNoRows {
+		return 0, nil
+	}
+
+	return count, nil
+}
+
+func (db *Type) VisitorIncrement() (err error) {
+	if _, err = db.sql.Exec("UPDATE visitor_count SET count = count + 1 WHERE id = 0"); err != nil && err != sql.ErrNoRows {
+		return err
+	}
+
+	// TODO: err is always nil even if there is no rows for some reason, check sql.Result instead
+
+	if err == sql.ErrNoRows {
+		_, err = db.sql.Exec(
+			`INSERT INTO visitor_count(
+			  id, count
+		  ) values(?, ?)`,
+			0, 0,
+		)
+
+		return err
+	}
+
+	return nil
+}

api/main.go

@@ -89,6 +89,7 @@ func main() {
 
 	// v1 user routes
 	v1.Get("/services", routes.GET_Services)
+	v1.Get("/visitor", routes.GET_Visitor)
 	v1.Get("/news/:lang", routes.GET_News)
 
 	// v1 admin routes

api/routes/visitor.go

@@ -0,0 +1,50 @@
+package routes
+
+import (
+	"github.com/gofiber/fiber/v2"
+	"github.com/ngn13/website/api/database"
+	"github.com/ngn13/website/api/util"
+)
+
+const LAST_ADDRS_MAX = 30
+
+var last_addrs []string
+
+func GET_Visitor(c *fiber.Ctx) error {
+	var (
+		err   error
+		count uint64
+	)
+
+	db := c.Locals("database").(*database.Type)
+	new_addr := util.GetSHA1(util.IP(c))
+
+	for _, addr := range last_addrs {
+		if new_addr == addr {
+			if count, err = db.VisitorGet(); err != nil {
+				return util.ErrInternal(c, err)
+			}
+
+			return util.JSON(c, 200, fiber.Map{
+				"result": count,
+			})
+		}
+	}
+
+	if err = db.VisitorIncrement(); err != nil {
+		return util.ErrInternal(c, err)
+	}
+
+	if count, err = db.VisitorGet(); err != nil {
+		return util.ErrInternal(c, err)
+	}
+
+	if len(last_addrs) > LAST_ADDRS_MAX {
+		last_addrs = append(last_addrs[:0], last_addrs[1:]...)
+		last_addrs = append(last_addrs, new_addr)
+	}
+
+	return util.JSON(c, 200, fiber.Map{
+		"result": count,
+	})
+}