package http_test

import (
	"bytes"
	"io"
	"io/ioutil"
	"net/http"
	"strings"
	"testing"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// Demonstration of bug in 
// https://github.com/golang/go/blob/3409ce39bfd7584523b7a8c150a310cea92d879d/src/net/http/request.go
// specifically the http.Request.ParseForm() API
//
func TestProofOfNetHttpBug(t *testing.T) {
	input := `form-data; name="key" value`
	destroyedInput := ""

	// create an http POST request with a Content-Type of application/x-www-form-urlencoded
	req, err := http.NewRequest(
		"POST",
		"https://doesntmatter.com",
		ioutil.NopCloser(bytes.NewBufferString(input)))
	require.Nil(t, err)
	req.Header = map[string][]string {
		"Content-Type": {"application/x-www-form-urlencoded"},
	}

	// We've set a body on the request, we show we the body is as expected
	body, err := snoop(&req.Body)
	assert.Nil(t, err)
	assert.Equal(t, input, body) 

	// For the skeptics, we demonstrate snoop is idempotent, we simply snoop again and show the body is still there
	body, err = snoop(&req.Body)
	assert.Nil(t, err)
	assert.Equal(t, input, body)

	// Now let's call the problem API
	assert.Nil(t, req.ParseForm())

	// Kaboom, the call to parseForm destroyed the body of the request
	body, err = snoop(&req.Body)
	assert.Nil(t, err)
	assert.Equal(t, destroyedInput, body)
}

// This test also shows the proper way to read twice from an io.ReadCloser.
func TestReadCloser(t *testing.T) {
	input := "abcdef"
	destroyedInput := ""

	// What not to do: copying a readcloser
	var reader1 io.ReadCloser = ioutil.NopCloser(strings.NewReader(input))
	var reader2 io.Reader = reader1
	b2, err := ioutil.ReadAll(reader2)
	assert.Nil(t, err)
	assert.Equal(t, input, string(b2))
	b1, err := ioutil.ReadAll(reader1)
	assert.Nil(t, err)
	reader1.Close()
	assert.Equal(t, destroyedInput, string(b1))
	// Kaboom: the input was destroyed

	// What to do instead: restore the reader from the buffer you read with ioutil.ReadAll
	reader1 = ioutil.NopCloser(strings.NewReader(input))
	b1, err = ioutil.ReadAll(reader1)
	assert.Nil(t, err)
	reader1.Close()
	reader1 = ioutil.NopCloser(bytes.NewBuffer(b1))
	b1, err = ioutil.ReadAll(reader1) // Now we prove this works by reading a second time
	assert.Nil(t, err)
	reader1.Close()
	assert.Equal(t, input, string(b1)) 
	// Tada: the input is read a second time, this works!
}


// snoop reads from an io.ReadCloser and restores it so it can be read again
func snoop(body *io.ReadCloser) (string, error) {
	if body != nil && *body != nil {
		result, err := ioutil.ReadAll(*body)
		(*body).Close()

		if err != nil {
			return "", err
		}
		
		*body = ioutil.NopCloser(bytes.NewReader(result))
		return string(result), nil
	}
	return "", nil
}