v2

v2/LICENSE

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+MIT License
+
+Copyright (c) 2024 Steve
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

v2/README.md

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+# Go-Toolkit
+
+A simple example of how to create a reusable Go module with commonly used tools.
+
+Made as apart of [Trevor Sawler's course on Udemy](https://www.udemy.com/course/building-a-module-in-go-golang)
+
+The included tools are:
+
+- [X]  Read JSON
+- [X]  Write JSON
+- [X]  Produce a JSON encoded error response
+- [X]  Upload a file to a specified directory
+- [X]  Download a static file
+- [X]  Get a random string of length n
+- [X]  Post JSON to a remote service
+- [X]  Create a directory, including all parent directories, if it does not already exist
+- [X]  Create a URL safe slug from a string
+
+## Installation
+
+`go get -u github.com/msf42/go-toolkit`

v2/go.mod

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+module github.com/MSF42/go-toolkit/v2
+
+go 1.22.4

v2/tools.go

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+package toolkit
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+const randomStringSource = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_+"
+
+// Tools is the type used to instantiate this module. Any variable of this type
+// will have access to all the methods with the receiver Tools.
+type Tools struct {
+	MaxFileSize        int
+	AllowedFileTypes   []string
+	MaxJSONSize        int
+	AllowUnknownFields bool
+}
+
+// RandomString generates a random string of length n
+func (t *Tools) RandomString(n int) string {
+	s, r := make([]rune, n), []rune(randomStringSource)
+	for i := range s {
+		p, _ := rand.Prime(rand.Reader, len(r))
+		x, y := p.Uint64(), uint64(len(r))
+		s[i] = r[x%y]
+	}
+	return string(s)
+}
+
+// UploadedFile is a struct used to save information about an uploaded file
+type UploadedFile struct {
+	NewFileName      string
+	OriginalFileName string
+	FileSize         int64
+}
+
+// UploadOneFile uploads one file
+func (t *Tools) UploadOneFile(r *http.Request, uploadDir string, rename ...bool) (*UploadedFile, error) {
+	renameFile := true
+	if len(rename) > 0 {
+		renameFile = rename[0]
+	}
+	files, err := t.UploadFiles(r, uploadDir, renameFile)
+	if err != nil {
+		return nil, err
+	}
+
+	return files[0], nil
+}
+
+// UploadFiles uploads multiple files
+func (t *Tools) UploadFiles(r *http.Request, uploadDir string, rename ...bool) ([]*UploadedFile, error) {
+	renameFile := true
+	if len(rename) > 0 {
+		renameFile = rename[0]
+	}
+
+	var uploadedFiles []*UploadedFile
+
+	if t.MaxFileSize == 0 {
+		t.MaxFileSize = 1024 * 1024 * 1024
+	}
+
+	err := t.CreateDirIfNotExist(uploadDir)
+	if err != nil {
+		return nil, err
+	}
+
+	err = r.ParseMultipartForm(int64(t.MaxFileSize))
+	if err != nil {
+		return nil, errors.New("the uploaded file size is too big")
+	}
+
+	for _, fHeaders := range r.MultipartForm.File {
+		for _, hdr := range fHeaders {
+			uploadedFiles, err = func(uploadedFiles []*UploadedFile) ([]*UploadedFile, error) {
+				var uploadedFile UploadedFile
+				infile, err := hdr.Open()
+				if err != nil {
+					return nil, err
+				}
+				defer infile.Close()
+
+				buff := make([]byte, 512)
+				_, err = infile.Read(buff)
+				if err != nil {
+					return nil, err
+				}
+
+				allowed := false
+				fileType := http.DetectContentType(buff)
+
+				if len(t.AllowedFileTypes) > 0 {
+					for _, x := range t.AllowedFileTypes {
+						if strings.EqualFold(fileType, x) {
+							allowed = true
+						}
+					}
+				} else {
+					allowed = true
+				}
+
+				if !allowed {
+					return nil, errors.New("the uploaded file type is not permitted")
+				}
+
+				_, err = infile.Seek(0, 0)
+				if err != nil {
+					return nil, err
+				}
+
+				if renameFile {
+					uploadedFile.NewFileName = fmt.Sprintf("%s%s", t.RandomString(25), filepath.Ext(hdr.Filename))
+				} else {
+					uploadedFile.NewFileName = hdr.Filename
+				}
+				uploadedFile.OriginalFileName = hdr.Filename
+
+				var outfile *os.File
+				defer outfile.Close()
+
+				if outfile, err = os.Create(filepath.Join(uploadDir, uploadedFile.NewFileName)); err != nil {
+					return nil, err
+				} else {
+					fileSize, err := io.Copy(outfile, infile)
+					if err != nil {
+						return nil, err
+					}
+					uploadedFile.FileSize = fileSize
+				}
+				uploadedFiles = append(uploadedFiles, &uploadedFile)
+
+				return uploadedFiles, nil
+
+			}(uploadedFiles)
+
+			if err != nil {
+				return uploadedFiles, err
+			}
+		}
+	}
+	return uploadedFiles, nil
+}
+
+// CreateDirIfNotExist creates a directory and all necessary parents if it does not exist
+func (t *Tools) CreateDirIfNotExist(path string) error {
+	const mode = 0755
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		err := os.MkdirAll(path, mode)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Slugify is a very simple slug generator
+func (t *Tools) Slugify(s string) (string, error) {
+	if s == "" {
+		return "", errors.New("empty string not permitted")
+	}
+
+	var re = regexp.MustCompile(`[^a-z\d]+`)
+	slug := strings.Trim(re.ReplaceAllString(strings.ToLower(s), "-"), "-")
+	if len(slug) == 0 {
+		return "", errors.New("after removing characters, slug is zero length")
+	}
+	return slug, nil
+}
+
+// DownloadStaticFile downloads a file without displaying it in the browser
+func (t *Tools) DownloadStaticFile(w http.ResponseWriter, r *http.Request, pathName, displayName string) {
+	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", displayName))
+
+	http.ServeFile(w, r, pathName)
+}
+
+// JSONResponse is the type used for sending JSON around
+type JSONResponse struct {
+	Error   bool        `json:"error"`
+	Message string      `json:"message"`
+	Data    interface{} `json:"data,omitempty"`
+}
+
+// ReadJSON tries to read the body of a request and converts from json into a go data variable
+func (t *Tools) ReadJSON(w http.ResponseWriter, r *http.Request, data interface{}) error {
+	maxBytes := 1024 * 1024
+	if t.MaxJSONSize != 0 {
+		maxBytes = t.MaxJSONSize
+	}
+
+	r.Body = http.MaxBytesReader(w, r.Body, int64(maxBytes))
+
+	dec := json.NewDecoder(r.Body)
+
+	if !t.AllowUnknownFields {
+		dec.DisallowUnknownFields()
+	}
+
+	err := dec.Decode(data)
+	if err != nil {
+		var syntaxError *json.SyntaxError
+		var unmarshalTypeError *json.UnmarshalTypeError
+		var invalidUnmarshalError *json.InvalidUnmarshalError
+
+		switch {
+		case errors.As(err, &syntaxError):
+			return fmt.Errorf("body contains badly-formed JSON (at character %d)", syntaxError.Offset)
+
+		case errors.Is(err, io.ErrUnexpectedEOF):
+			return errors.New("body contains badly-formed JSON")
+
+		case errors.As(err, &unmarshalTypeError):
+			if unmarshalTypeError.Field != "" {
+				return fmt.Errorf("body contains incorrect JSON type for field %q", unmarshalTypeError.Field)
+			}
+			return fmt.Errorf("body contains incorrect JSON type (at character %d)", unmarshalTypeError.Offset)
+
+		case errors.Is(err, io.EOF):
+			return errors.New("body must not be empty")
+
+		case strings.HasPrefix(err.Error(), "json: unknown field"):
+			fieldName := strings.TrimPrefix(err.Error(), "json: unknown field")
+			return fmt.Errorf("body contains unknown key %s", fieldName)
+
+		case err.Error() == "http: request body too large":
+			return fmt.Errorf("body must not be larger than %d bytes", maxBytes)
+
+		case errors.As(err, &invalidUnmarshalError):
+			return fmt.Errorf("error unmarshalling JSON: %s", err.Error())
+
+		default:
+			return err
+		}
+	}
+
+	err = dec.Decode(&struct{}{})
+	if err != io.EOF {
+		return errors.New("body must contain only one JSON value")
+	}
+
+	return nil
+}
+
+// WriteJSON takes a response status code and arbitrary data and writes json to the client
+func (t *Tools) WriteJSON(w http.ResponseWriter, status int, data interface{}, headers ...http.Header) error {
+	out, err := json.Marshal(data)
+	if err != nil {
+		return err
+	}
+
+	if len(headers) > 0 {
+		for key, value := range headers[0] {
+			w.Header()[key] = value
+		}
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_, err = w.Write(out)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// ErrorJSON takes an error, & optionally a status code, and generates and sends a JSON error message
+func (t *Tools) ErrorJSON(w http.ResponseWriter, err error, status ...int) error {
+	statusCode := http.StatusBadRequest
+
+	if len(status) > 0 {
+		statusCode = status[0]
+	}
+
+	var payload JSONResponse
+	payload.Error = true
+	payload.Message = err.Error()
+
+	return t.WriteJSON(w, statusCode, payload)
+}
+
+// PushJSONToRemote posts arbitrary data to some URL as JSON, and returns the response, status code, and error, if any.
+// The final parameter, client, is optional. If none is specified, we use the standard http.Client.
+func (t *Tools) PushJSONToRemote(uri string, data interface{}, client ...*http.Client) (*http.Response, int, error) {
+	// create json
+	jsonData, err := json.Marshal(data)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// check for custom http client
+	httpClient := &http.Client{}
+	if len(client) > 0 {
+		httpClient = client[0]
+	}
+
+	// build the request and set the header
+	request, err := http.NewRequest("POST", uri, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return nil, 0, err
+	}
+	request.Header.Set("Content-Type", "application/json")
+
+	// call the remote uri
+	response, err := httpClient.Do(request)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer response.Body.Close()
+
+	// send response back
+	return response, response.StatusCode, nil
+}