Laveraging Pinata API to upload files

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "log"
    "mime/multipart"
    "net/http"
    "os"
    "path/filepath"
    "sync"

    "github.com/joho/godotenv"
)

const (
    maxFileSize = 10 << 20 // 10 MB
)

type PinataResponse struct {
    IpfsHash  string `json:"IpfsHash"`
    PinSize   int    `json:"PinSize"`
    Timestamp string `json:"Timestamp"`
}

type ErrorResponse struct {
    Error string `json:"error"`
}

type Credentials struct {
    Username string `json:"username"`
    Password string `json:"password"`
}

func main() {
    // Load .env file
    err := godotenv.Load(".env")
    if err != nil {
        log.Fatal("Error loading .env file")
    }

    // http.HandleFunc("/upload", handleUpload)
    http.Handle("/upload", corsMiddleware(http.HandlerFunc(handleUpload)))
    fmt.Println("Server is running on http://localhost:9000")
    log.Fatal(http.ListenAndServe(":9000", nil))
}

func corsMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Header().Set("Access-Control-Allow-Origin", "*")
        w.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS")
        w.Header().Set("Access-Control-Allow-Headers", "Content-Type, pinata_api_key, pinata_secret_api_key")

        if r.Method == "OPTIONS" {
            w.WriteHeader(http.StatusNoContent)
            return
        }

        next.ServeHTTP(w, r)
    })
}

func handleUpload(w http.ResponseWriter, r *http.Request) {
    if r.Method != http.MethodPost {
        sendErrorResponse(w, "Method not allowed", http.StatusMethodNotAllowed)
        return
    }

    err := r.ParseMultipartForm(maxFileSize)
    if err != nil {
        sendErrorResponse(w, "Failed to parse multipart form: "+err.Error(), http.StatusBadRequest)
        return
    }

    files := r.MultipartForm.File["files"]
    if len(files) == 0 {
        sendErrorResponse(w, "No files were uploaded", http.StatusBadRequest)
        return
    }

    responses := make([]PinataResponse, 0, len(files))
    errors := make([]string, 0)

    var wg sync.WaitGroup
    var mu sync.Mutex

    for _, fileHeader := range files {
        wg.Add(1)
        go func(fh *multipart.FileHeader) {
            defer wg.Done()

            response, err := uploadFileToPinata(fh)
            mu.Lock()
            defer mu.Unlock()

            if err != nil {
                errors = append(errors, fmt.Sprintf("Error uploading %s: %v", fh.Filename, err))
            } else {
                responses = append(responses, response)
            }
        }(fileHeader)
    }

    wg.Wait()

    result := struct {
        SuccessfulUploads []PinataResponse `json:"successful_uploads"`
        Errors            []string         `json:"errors,omitempty"`
    }{
        SuccessfulUploads: responses,
        Errors:            errors,
    }

    w.Header().Set("Content-Type", "application/json")
    if len(errors) > 0 {
        w.WriteHeader(http.StatusPartialContent)
    } else {
        w.WriteHeader(http.StatusOK)
    }
    json.NewEncoder(w).Encode(result)
}

func uploadFileToPinata(fileHeader *multipart.FileHeader) (PinataResponse, error) {
    file, err := fileHeader.Open()
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to open file: %w", err)
    }
    defer file.Close()

    var requestBody bytes.Buffer
    writer := multipart.NewWriter(&requestBody)

    part, err := writer.CreateFormFile("file", filepath.Base(fileHeader.Filename))
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to create form file: %w", err)
    }

    _, err = io.Copy(part, file)
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to copy file content: %w", err)
    }

    err = writer.Close()
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to close multipart writer: %w", err)
    }

    // Load environment variables
    pinataAPIKey := os.Getenv("PINATA_API_KEY")
    pinataAPISecret := os.Getenv("PINATA_API_SECRET")
    pinataAPIURL := os.Getenv("PINATA_API_URL")

    req, err := http.NewRequest("POST", pinataAPIURL, &requestBody)
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to create request: %w", err)
    }

    req.Header.Set("Content-Type", writer.FormDataContentType())
    req.Header.Set("pinata_api_key", pinataAPIKey)
    req.Header.Set("pinata_secret_api_key", pinataAPISecret)

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to send request: %w", err)
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        return PinataResponse{}, fmt.Errorf("pinata API returned non-OK status: %s", resp.Status)
    }

    var pinataResp PinataResponse
    err = json.NewDecoder(resp.Body).Decode(&pinataResp)
    if err != nil {
        return PinataResponse{}, fmt.Errorf("failed to decode Pinata response: %w", err)
    }

    return pinataResp, nil
}

func sendErrorResponse(w http.ResponseWriter, message string, statusCode int) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(statusCode)
    json.NewEncoder(w).Encode(ErrorResponse{Error: message})
}