docs: add code documentation

database/migrate.go

@@ -2,6 +2,8 @@ package database
 
 import "github.com/kevinanielsen/go-fast-cdn/models"
 
+// Migrate runs database migrations for all model structs using
+// the global DB instance. This would typically be called on app startup.
 func Migrate() {
 	DB.AutoMigrate(&models.Image{}, &models.Doc{})
 }

initializers/loadEnvVariables.go

@@ -7,6 +7,9 @@ import (
 	"github.com/joho/godotenv"
 )
 
+// LoadEnvVariables loads environment variables from .env file or sets
+// hardcoded values based on prod boolean. In prod it sets PORT and DB_SECRET
+// to hardcoded values. In dev it loads .env file from current directory.
 func LoadEnvVariables(prod bool) {
 	if prod {
 		os.Setenv("PORT", "8080")

router/router.go

@@ -8,6 +8,8 @@ import (
 	"github.com/kevinanielsen/go-fast-cdn/ui"
 )
 
+// Router initializes the router and sets up middleware, routes, etc.
+// It returns a *gin.Engine instance configured with the routes, middleware, etc.
 func Router() {
 	r := gin.Default()
 

ui/embed.go

@@ -14,7 +14,10 @@ import (
 //go:embed build
 var staticFS embed.FS
 
-// AddRoutes serves the static file system for the UI React App.
+// AddRoutes configures the router with middleware to serve the embedded
+// React frontend. It serves the frontend as static files from the
+// embedded build folder. It also configures a fallback filesystem to
+// always serve index.html for unknown routes.
 func AddRoutes(router gin.IRouter) {
 	embeddedBuildFolder := newStaticFileSystem()
 	fallbackFileSystem := newFallbackFileSystem(embeddedBuildFolder)

util/filterFilename.go

@@ -1,10 +1,15 @@
+// Package util contains utility functions used throughout the application.
 package util
 
 import (
 	"errors"
 	"strings"
 )
 
+// countVal counts the number of occurrences of val in str.
+// It splits str into a slice of strings, iterates over the slice
+// checking each string for equality with val, and increments a counter
+// each time a match is found. The final count is returned.
 func countVal(str string, val string) int {
 	var count int
 	arr := strings.Split(str, "")
@@ -17,6 +22,10 @@ func countVal(str string, val string) int {
 	return count
 }
 
+// FilterFilename removes illegal characters from a filename string.
+// It ensures there is at most one period in the filename,
+// replaces any '/' and '\' characters,
+// and returns the filtered string.
 func FilterFilename(filename string) (string, error) {
 	if countVal(filename, ".") > 1 {
 		return filename, errors.New("filename cannot contain more than one period character")

util/getPath.go

@@ -7,6 +7,10 @@ import (
 
 var ExPath string
 
+// LoadExPath loads the executable path and stores it in the ExPath variable.
+// It uses os.Executable to get the path of the current executable.
+// The filepath.Dir function is used to get the directory containing the executable.
+// If there is an error getting the executable path, it will panic.
 func LoadExPath() {
 	ex, err := os.Executable()
 	if err != nil {