abzcoding/hget

package main

import (
    "github.com/fatih/color"
    "gopkg.in/cheggaaa/pb.v1"
    "io"
    "os"
    "sort"
)

// JoinFile joins seperate chunks of file and forms the final downloaded artifact
func JoinFile(files []string, out string) error {
    //sort with file name or we will join files with wrong order
    sort.Strings(files)
    var bar *pb.ProgressBar

    if DisplayProgressBar() {
        Printf("Start joining \n")
        bar = pb.StartNew(len(files)).Prefix(color.CyanString("Joining"))
    }

    outf, err := os.OpenFile(out, os.O_CREATE|os.O_WRONLY, 0600)
    defer outf.Close()
    if err != nil {
        return err
    }

    for _, f := range files {
        if err = copy(f, outf); err != nil {
            return err
        }
        if DisplayProgressBar() {
            bar.Increment()
        }
    }

    if DisplayProgressBar() {
        bar.Finish()
    }

    return nil
}

//this function split just to use defer
func copy(from string, to io.Writer) error {
    f, err := os.OpenFile(from, os.O_RDONLY, 0600)
    defer f.Close()
    if err != nil {
        return err
    }
    io.Copy(to, f)
    return nil
}