package main

import (
    "fmt"
    "strings"
    "os"
    "io"
    "net/http"
    "path/filepath"
)

// WriteCounter counts the number of bytes written to it
type WriteCounter struct {
    Filepath string
    Total uint64
}

func (wc *WriteCounter) Write(p []byte) (int, error) {
    n := len(p)
    wc.Total += uint64(n)
    wc.PrintProgress()
    return n, nil
}

func (wc *WriteCounter) PrintProgress() {
    // clear the line by using a character return to go back to the start of the
    // line and remove the remaining characters
    fmt.Printf("\r%s", strings.Repeat(" ", 35))
    fmt.Printf("\r[%s]... %d bytes complete", wc.Filepath, wc.Total)
}

func downloadFile(path string, url string) error {
    // make sure dir exists
    os.MkdirAll(filepath.Dir(path), 0777)

    // create .part file
    output, err := os.Create(path + ".part")
    if err != nil {
        return err
    }
    defer output.Close()

    // get data
    response, err := http.Get(url)
    if err != nil {
        return err
    }
    defer response.Body.Close()

    // create progress reporter
    counter := &WriteCounter{path, 0}
    _, err = io.Copy(output, io.TeeReader(response.Body, counter))
    if err != nil {
        return err
    }

    fmt.Printf("\n")
    //fmt.Printf("\r%s", strings.Repeat(" ", 40))
    os.Rename(path + ".part", path)
    //fmt.Printf("\r[%s] complete\n", path)
    return nil
}