Merge pull request #203 from mackerelio/improve-mkr-wrap-message-trun…

…cation

[wrap] Improve message truncation algorithm

wrap/result.go

@@ -113,11 +113,25 @@ func (re *result) buildMsg(detail bool) string {
 	}
 	buf := &bytes.Buffer{}
 	template.Must(msgTpl.Clone()).Execute(buf, s)
-	msg := buf.String()
-	const messageLengthLimit = 1024
-	runes := []rune(msg)
-	if len(runes) > messageLengthLimit {
-		msg = string(runes[0:messageLengthLimit])
+	const messageLengthLimit = 1024 // https://mackerel.io/api-docs/entry/check-monitoring#post
+	return truncate(buf.String(), messageLengthLimit, "\n...\n")
+}
+
+func truncate(src string, limit int, sep string) string {
+	rs := []rune(src)
+	if len(rs) <= limit {
+		return src
+	}
+	seprs := []rune(sep)
+	var i int
+	rest := limit - len(seprs)
+	if 0 < rest {
+		i += rest / 2
+		rest -= rest / 2
+	}
+	i += copy(rs[i:], seprs)
+	if 0 < rest {
+		copy(rs[i:], rs[len(rs)-rest:])
 	}
-	return msg
+	return string(rs[:limit])
 }

wrap/testdata/long.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	for i := 0; i < 100; i++ {
+		fmt.Println("Hello world!")
+	}
+	os.Exit(1)
+}

wrap/wrap_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"reflect"
+	"strings"
 	"testing"
 
 	mackerel "github.com/mackerelio/mackerel-client-go"
@@ -73,6 +74,30 @@ Note: This is note
 % go run testdata/stub.go
 Hello.
 exit status 1
+`,
+				NotificationInterval: 0,
+			},
+			ExitCode: 1,
+		},
+		{
+			Name: "long output",
+			Args: []string{
+				"-name=test-check",
+				"-detail",
+				"-note", "This is note",
+				"--",
+				"go", "run", "testdata/long.go",
+			},
+			Result: testResult{
+				Name:   "test-check",
+				Status: mackerel.CheckStatusCritical,
+				Message: `command exited with code: 1
+Note: This is note
+% go run testdata/long.go
+` + strings.Repeat("Hello world!\n", 33) + `Hello w
+...
+!
+` + strings.Repeat("Hello world!\n", 38) + `exit status 1
 `,
 				NotificationInterval: 0,
 			},
@@ -183,3 +208,84 @@ func TestCommand_Action_withoutConf(t *testing.T) {
 			err, expect)
 	}
 }
+
+func Test_truncate(t *testing.T) {
+	testCases := []struct {
+		src      string
+		limit    int
+		sep      string
+		expected string
+	}{
+		{
+			src:      "",
+			limit:    0,
+			sep:      "",
+			expected: "",
+		},
+		{
+			src:      "",
+			limit:    10,
+			sep:      " ... ",
+			expected: "",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    100,
+			sep:      " ... ",
+			expected: "Hello, world!",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    0,
+			sep:      " ... ",
+			expected: "",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    3,
+			sep:      " ... ",
+			expected: " ..",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    5,
+			sep:      " ... ",
+			expected: " ... ",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    10,
+			sep:      " ... ",
+			expected: "He ... ld!",
+		},
+		{
+			src:      "Hello, world!",
+			limit:    15,
+			sep:      " ... ",
+			expected: "Hello, world!",
+		},
+		{
+			src:      "こんにちは、世界",
+			limit:    6,
+			sep:      "..",
+			expected: "こん..世界",
+		},
+		{
+			src:      strings.Repeat("abcde", 10),
+			limit:    30,
+			sep:      " ... ",
+			expected: "abcdeabcdeab ... cdeabcdeabcde",
+		},
+	}
+	for _, tc := range testCases {
+		got := truncate(tc.src, tc.limit, tc.sep)
+		if got != tc.expected {
+			t.Errorf("truncate(%q, %d, %q) should be %q but got: %q",
+				tc.src, tc.limit, tc.sep, tc.expected, got)
+		}
+		if len([]rune(got)) > tc.limit {
+			t.Errorf("length of truncate(%q, %d, %q) should not exceed %d but got: %d",
+				tc.src, tc.limit, tc.sep, tc.limit, len([]rune(got)))
+		}
+	}
+}