migrate/util.go

package migrate

import (
	"bufio"
	"fmt"
	"io"
	nurl "net/url"
	"strings"
	"time"
)

// MultiError holds multiple errors.
type MultiError struct {
	Errs []error
}

// NewMultiError returns an error type holding multiple errors.
func NewMultiError(errs ...error) MultiError {
	compactErrs := make([]error, 0)
	for _, e := range errs {
		if e != nil {
			compactErrs = append(compactErrs, e)
		}
	}
	return MultiError{compactErrs}
}

// Error implements error. Mulitple errors are concatenated with 'and's.
func (m MultiError) Error() string {
	var strs = make([]string, 0)
	for _, e := range m.Errs {
		if len(e.Error()) > 0 {
			strs = append(strs, e.Error())
		}
	}
	return strings.Join(strs, " and ")
}

// suint safely converts int to uint
// see https://goo.gl/wEcqof
// see https://goo.gl/pai7Dr
func suint(n int) uint {
	if n < 0 {
		panic(fmt.Sprintf("suint(%v) expects input >= 0", n))
	}
	return uint(n)
}

// newSlowReader turns an io.ReadCloser into a slow io.ReadCloser.
// Use this to simulate a slow internet connection.
func newSlowReader(r io.ReadCloser) io.ReadCloser {
	return &slowReader{
		rx:     r,
		reader: bufio.NewReader(r),
	}
}

type slowReader struct {
	rx     io.ReadCloser
	reader *bufio.Reader
}

func (b *slowReader) Read(p []byte) (n int, err error) {
	time.Sleep(10 * time.Millisecond)
	c, err := b.reader.ReadByte()
	if err != nil {
		return 0, err
	} else {
		copy(p, []byte{c})
		return 1, nil
	}
}

func (b *slowReader) Close() error {
	return b.rx.Close()
}

var errNoScheme = fmt.Errorf("no scheme")

// schemeFromUrl returns the scheme from a URL string
func schemeFromUrl(url string) (string, error) {
	u, err := nurl.Parse(url)
	if err != nil {
		return "", err
	}

	if len(u.Scheme) == 0 {
		return "", errNoScheme
	}

	return u.Scheme, nil
}