package main

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

func Min(x, y int64) int64 {
	if x < y {
		return x
	}
	return y
}

func Max(x, y int64) int64 {
	if x > y {
		return x
	}
	return y
}

// WriteCounter counts the number of bytes written to it
type WriteCounter struct {
	ContentLength int64
	BytesWritten  uint64

	Step int64
}

func NewWriteCounter(contentLength int64) *WriteCounter {
	ptr := new(WriteCounter)
	ptr.ContentLength = contentLength
	ptr.Step = Max(contentLength/20, 1)

	return ptr
}

func (wc *WriteCounter) Write(p []byte) (int, error) {
	n := len(p)
	wc.BytesWritten += 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))

	// steps can be at most 20 -> get the minimum of (n_steps) and 20
	steps := int(Min(int64(wc.BytesWritten)/wc.Step, 20))

	fmt.Printf("\r[%s%s] %d/%d bytes complete", strings.Repeat("#", steps), strings.Repeat(" ", 20-steps), wc.BytesWritten, wc.ContentLength)
}

func downloadFile(path string, url string) error {
	// make sure dir exists
	os.MkdirAll(filepath.Dir(path), 0755)

	// 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 := NewWriteCounter(response.ContentLength)
	_, err = io.Copy(output, io.TeeReader(response.Body, counter))
	if err != nil {
		return err
	}

	fmt.Printf("\n")
	output.Close()
	return os.Rename(path+".part", path)
}