package email

import (
	"bufio"
	"bytes"
	"encoding/base64"
	"encoding/json"
	"net/http"
	"testing"

	"github.com/stretchr/testify/require"
	"go.skia.org/infra/go/httputils"
	"go.skia.org/infra/go/testutils/unittest"
	"google.golang.org/api/gmail/v1"
)

const subject = "An Alert!"

const expectedMessage = `From: Alert Service <alerts@skia.org>
To: test@example.com
Subject: An Alert!
Content-Type: text/html; charset=UTF-8
References: <some-reference-id>
In-Reply-To: <some-reference-id>

<html>
<body>

<div itemscope itemtype="http://schema.org/EmailMessage">
  <div itemprop="potentialAction" itemscope itemtype="http://schema.org/ViewAction">
    <link itemprop="target" href="https://example.com"/>
    <meta itemprop="name" content="Example"/>
  </div>
  <meta itemprop="description" content="Click the link"/>
</div>

<h1>Something happened</h1>
</body>
</html>
`

// Mock out the http.Client by supplying our own http.RoundTripper.
type myTransport struct {
	t *testing.T
}

// RoundTrip implements http.RoundTripper.
func (m *myTransport) RoundTrip(r *http.Request) (*http.Response, error) {
	// Check the URL.
	require.Equal(m.t, "https://gmail.googleapis.com/gmail/v1/users/alerts%40skia.org/messages/send?alt=json&prettyPrint=false", r.URL.String())

	// Confirm the body, which is a JSON encoded gmail.Message, is correct.
	var msg gmail.Message
	err := json.NewDecoder(r.Body).Decode(&msg)
	require.NoError(m.t, err)
	require.Equal(m.t, subject, msg.Snippet)
	require.Equal(m.t, int64(563), msg.SizeEstimate)

	// The actual RFC2822 message is base64 encoded in the .Raw member.
	b, err := base64.URLEncoding.DecodeString(msg.Raw)
	require.NoError(m.t, err)
	require.Equal(m.t, expectedMessage, string(b))

	// Now supply a response that the GMail client library will accept.
	buf := bytes.NewBufferString(`HTTP/1.1 200 OK
Date: Mon, 27 Jul 2020 12:28:53 GMT
Last-Modified: Wed, 22 Jul 2020 19:15:56 GMT
Content-Type: text/html

{
	"id": "some-email-id"
}`)
	return http.ReadResponse(bufio.NewReader(buf), r)
}

var _ http.RoundTripper = (*myTransport)(nil)

func TestGMailSendWithMarkup(t *testing.T) {
	unittest.SmallTest(t)
	c := httputils.DefaultClientConfig().Client()
	// Swap in our mock transport.
	c.Transport = &myTransport{t: t}

	// Construct a new *GMail instance.
	service, err := gmail.New(c)
	require.NoError(t, err)
	gm := &GMail{
		service: service,
		from:    "alerts@skia.org",
	}
	markup, err := GetViewActionMarkup("https://example.com", "Example", "Click the link")
	require.NoError(t, err)
	ref := "<some-reference-id>"

	// Send email, the validation happens in myTransport.
	_, err = gm.SendWithMarkup("Alert Service", []string{"test@example.com"}, subject, "<h1>Something happened</h1>", markup, ref)
	require.NoError(t, err)
}

func TestParseRFC2822Message_HappyPath(t *testing.T) {
	unittest.SmallTest(t)
	from, to, subject, body, err := ParseRFC2822Message([]byte(`From: Alerts <alerts@skia.org>
To:  A Display Name <a@example.com>, B <b@example.org>,,
Subject: My Stuff

Hi!
`))
	require.NoError(t, err)
	require.Equal(t, "Alerts <alerts@skia.org>", from)
	require.Equal(t, []string{"A Display Name <a@example.com>", "B <b@example.org>"}, to)
	require.Equal(t, "My Stuff", subject)
	require.Equal(t, "Hi!\n", body)
}

func TestParseRFC2822Message_EmptyInput_ReturnsError(t *testing.T) {
	unittest.SmallTest(t)
	_, _, _, _, err := ParseRFC2822Message([]byte(``))
	require.Contains(t, err.Error(), "Failed to find a From: line")
}

func TestParseRFC2822Message_EmptyToLine_ReturnsError(t *testing.T) {
	unittest.SmallTest(t)
	_, _, _, _, err := ParseRFC2822Message([]byte(`From: Alerts <alerts@skia.org>
To:  ,,,
Subject: My Stuff

Hi!
`))
	require.Contains(t, err.Error(), "Failed to find any To: addresses")
}

func TestParseRFC2822Message_MissingSubject_DefaultSubjectIsReturned(t *testing.T) {
	unittest.SmallTest(t)
	from, to, subject, body, err := ParseRFC2822Message([]byte(`From: Alerts <alerts@skia.org>
To: someone@example.org

Hi!
`))
	require.NoError(t, err)
	require.Equal(t, "Alerts <alerts@skia.org>", from)
	require.Equal(t, []string{"someone@example.org"}, to)
	require.Equal(t, "(no subject)", subject)
	require.Equal(t, "Hi!\n", body)
}

func TestFormatAsRFC2822_HappyPath(t *testing.T) {
	unittest.SmallTest(t)
	body := `<h1>Testing</h1>`
	ref := "<some-reference-id>"
	messageID := "<foo-bar-baz@skia.org>"
	markup, err := GetViewActionMarkup("https://example.com", "Example", "Click the link")
	require.NoError(t, err)
	actual, err := FormatAsRFC2822("Alerts", "alerts@skia.org", []string{"someone@example.org"}, "Your Alert", body, markup, ref, messageID)
	require.NoError(t, err)
	expected := `From: Alerts <alerts@skia.org>
To: someone@example.org
Subject: Your Alert
Content-Type: text/html; charset=UTF-8
References: <some-reference-id>
In-Reply-To: <some-reference-id>
Message-ID: <foo-bar-baz@skia.org>

<html>
<body>

<div itemscope itemtype="http://schema.org/EmailMessage">
  <div itemprop="potentialAction" itemscope itemtype="http://schema.org/ViewAction">
    <link itemprop="target" href="https://example.com"/>
    <meta itemprop="name" content="Example"/>
  </div>
  <meta itemprop="description" content="Click the link"/>
</div>

<h1>Testing</h1>
</body>
</html>
`
	require.Equal(t, expected, actual.String())
}

func TestFormatAsRFC2822_NoThreadID_MessageDoesNotContainInReplyToOrReferencesHeaders(t *testing.T) {
	unittest.SmallTest(t)
	body := `<h1>Testing</h1>`
	ref := ""
	messageID := "<foo-bar-baz@skia.org>"
	markup, err := GetViewActionMarkup("https://example.com", "Example", "Click the link")
	require.NoError(t, err)
	actual, err := FormatAsRFC2822("Alerts", "alerts@skia.org", []string{"someone@example.org"}, "Your Alert", body, markup, ref, messageID)
	require.NoError(t, err)
	expected := `From: Alerts <alerts@skia.org>
To: someone@example.org
Subject: Your Alert
Content-Type: text/html; charset=UTF-8
Message-ID: <foo-bar-baz@skia.org>

<html>
<body>

<div itemscope itemtype="http://schema.org/EmailMessage">
  <div itemprop="potentialAction" itemscope itemtype="http://schema.org/ViewAction">
    <link itemprop="target" href="https://example.com"/>
    <meta itemprop="name" content="Example"/>
  </div>
  <meta itemprop="description" content="Click the link"/>
</div>

<h1>Testing</h1>
</body>
</html>
`
	require.Equal(t, expected, actual.String())
}

func TestFormatAsRFC2822_NoThreadIDOrMessageID_MessageDoesNotContainInReplyToOrReferenceOrMessageIDHeaders(t *testing.T) {
	unittest.SmallTest(t)
	body := `<h1>Testing</h1>`
	ref := ""
	messageID := ""
	markup, err := GetViewActionMarkup("https://example.com", "Example", "Click the link")
	require.NoError(t, err)
	actual, err := FormatAsRFC2822("Alerts", "alerts@skia.org", []string{"someone@example.org"}, "Your Alert", body, markup, ref, messageID)
	require.NoError(t, err)
	expected := `From: Alerts <alerts@skia.org>
To: someone@example.org
Subject: Your Alert
Content-Type: text/html; charset=UTF-8

<html>
<body>

<div itemscope itemtype="http://schema.org/EmailMessage">
  <div itemprop="potentialAction" itemscope itemtype="http://schema.org/ViewAction">
    <link itemprop="target" href="https://example.com"/>
    <meta itemprop="name" content="Example"/>
  </div>
  <meta itemprop="description" content="Click the link"/>
</div>

<h1>Testing</h1>
</body>
</html>
`
	require.Equal(t, expected, actual.String())
}

func TestFormatAsRFC2822_NoMessageID_MessageDoesNotContainMessageIDHeader(t *testing.T) {
	unittest.SmallTest(t)
	body := `<h1>Testing</h1>`
	ref := "<some-reference-id>"
	messageID := ""
	markup, err := GetViewActionMarkup("https://example.com", "Example", "Click the link")
	require.NoError(t, err)
	actual, err := FormatAsRFC2822("Alerts", "alerts@skia.org", []string{"someone@example.org"}, "Your Alert", body, markup, ref, messageID)
	require.NoError(t, err)
	expected := `From: Alerts <alerts@skia.org>
To: someone@example.org
Subject: Your Alert
Content-Type: text/html; charset=UTF-8
References: <some-reference-id>
In-Reply-To: <some-reference-id>

<html>
<body>

<div itemscope itemtype="http://schema.org/EmailMessage">
  <div itemprop="potentialAction" itemscope itemtype="http://schema.org/ViewAction">
    <link itemprop="target" href="https://example.com"/>
    <meta itemprop="name" content="Example"/>
  </div>
  <meta itemprop="description" content="Click the link"/>
</div>

<h1>Testing</h1>
</body>
</html>
`
	require.Equal(t, expected, actual.String())
}