plumbing: no panic in printStat function. Fixes #177

3 files changed, 152 insertions, 55 deletions

diff --git a/plumbing/object/commit_test.go b/plumbing/object/commit_test.go
index 3e1fe1b..2127e9a 100644
--- a/plumbing/object/commit_test.go
+++ b/plumbing/object/commit_test.go
@@ -455,7 +455,7 @@ func (s *SuiteCommit) TestStat(c *C) {
 	c.Assert(fileStats[1].Name, Equals, "php/crappy.php")
 	c.Assert(fileStats[1].Addition, Equals, 259)
 	c.Assert(fileStats[1].Deletion, Equals, 0)
-	c.Assert(fileStats[1].String(), Equals, " php/crappy.php | 259 ++++++++++++++++++++++++++++++++++++++++++++++++++++\n")
+	c.Assert(fileStats[1].String(), Equals, " php/crappy.php | 259 +++++++++++++++++++++++++++++++++++++++++++++++++++++\n")
 }
 
 func (s *SuiteCommit) TestVerify(c *C) {
diff --git a/plumbing/object/patch.go b/plumbing/object/patch.go
index dd8fef4..3c61f62 100644
--- a/plumbing/object/patch.go
+++ b/plumbing/object/patch.go
@@ -6,7 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"math"
+	"strconv"
 	"strings"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -234,69 +234,56 @@ func (fileStats FileStats) String() string {
 	return printStat(fileStats)
 }
 
+// printStat prints the stats of changes in content of files.
+// Original implementation: https://github.com/git/git/blob/1a87c842ece327d03d08096395969aca5e0a6996/diff.c#L2615
+// Parts of the output:
+// <pad><filename><pad>|<pad><changeNumber><pad><+++/---><newline>
+// example: " main.go | 10 +++++++--- "
 func printStat(fileStats []FileStat) string {
-	padLength := float64(len(" "))
-	newlineLength := float64(len("\n"))
-	separatorLength := float64(len("|"))
-	// Soft line length limit. The text length calculation below excludes
-	// length of the change number. Adding that would take it closer to 80,
-	// but probably not more than 80, until it's a huge number.
-	lineLength := 72.0
-
-	// Get the longest filename and longest total change.
-	var longestLength float64
-	var longestTotalChange float64
-	for _, fs := range fileStats {
-		if int(longestLength) < len(fs.Name) {
-			longestLength = float64(len(fs.Name))
-		}
-		totalChange := fs.Addition + fs.Deletion
-		if int(longestTotalChange) < totalChange {
-			longestTotalChange = float64(totalChange)
-		}
-	}
-
-	// Parts of the output:
-	// <pad><filename><pad>|<pad><changeNumber><pad><+++/---><newline>
-	// example: " main.go | 10 +++++++--- "
-
-	// <pad><filename><pad>
-	leftTextLength := padLength + longestLength + padLength
-
-	// <pad><number><pad><+++++/-----><newline>
-	// Excluding number length here.
-	rightTextLength := padLength + padLength + newlineLength
+	maxGraphWidth := uint(53)
+	maxNameLen := 0
+	maxChangeLen := 0
 
-	totalTextArea := leftTextLength + separatorLength + rightTextLength
-	heightOfHistogram := lineLength - totalTextArea
+	scaleLinear := func(it, width, max uint) uint {
+		if it == 0 || max == 0 {
+			return 0
+		}
 
-	// Scale the histogram.
-	var scaleFactor float64
-	if longestTotalChange > heightOfHistogram {
-		// Scale down to heightOfHistogram.
-		scaleFactor = longestTotalChange / heightOfHistogram
-	} else {
-		scaleFactor = 1.0
+		return 1 + (it * (width - 1) / max)
 	}
 
-	finalOutput := ""
 	for _, fs := range fileStats {
-		addn := float64(fs.Addition)
-		deln := float64(fs.Deletion)
-		addc := int(math.Floor(addn/scaleFactor))
-		delc := int(math.Floor(deln/scaleFactor))
-		if addc < 0 {
-			addc = 0
+		if len(fs.Name) > maxNameLen {
+			maxNameLen = len(fs.Name)
 		}
-		if delc < 0 {
-			delc = 0
+
+		changes := strconv.Itoa(fs.Addition + fs.Deletion)
+		if len(changes) > maxChangeLen {
+			maxChangeLen = len(changes)
 		}
-		adds := strings.Repeat("+", addc)
-		dels := strings.Repeat("-", delc)
-		finalOutput += fmt.Sprintf(" %s | %d %s%s\n", fs.Name, (fs.Addition + fs.Deletion), adds, dels)
 	}
 
-	return finalOutput
+	result := ""
+	for _, fs := range fileStats {
+		add := uint(fs.Addition)
+		del := uint(fs.Deletion)
+		np := maxNameLen - len(fs.Name)
+		cp := maxChangeLen - len(strconv.Itoa(fs.Addition+fs.Deletion))
+
+		total := add + del
+		if total > maxGraphWidth {
+			add = scaleLinear(add, maxGraphWidth, total)
+			del = scaleLinear(del, maxGraphWidth, total)
+		}
+
+		adds := strings.Repeat("+", int(add))
+		dels := strings.Repeat("-", int(del))
+		namePad := strings.Repeat(" ", np)
+		changePad := strings.Repeat(" ", cp)
+
+		result += fmt.Sprintf(" %s%s | %s%d %s%s\n", fs.Name, namePad, changePad, total, adds, dels)
+	}
+	return result
 }
 
 func getFileStatsFromFilePatches(filePatches []fdiff.FilePatch) FileStats {
diff --git a/plumbing/object/patch_test.go b/plumbing/object/patch_test.go
index 2cff795..e0e63a5 100644
--- a/plumbing/object/patch_test.go
+++ b/plumbing/object/patch_test.go
@@ -45,3 +45,113 @@ func (s *PatchSuite) TestStatsWithSubmodules(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(p, NotNil)
 }
+
+func (s *PatchSuite) TestFileStatsString(c *C) {
+	testCases := []struct {
+		description string
+		input       FileStats
+		expected    string
+	}{
+
+		{
+			description: "no files changed",
+			input:       []FileStat{},
+			expected:    "",
+		},
+		{
+			description: "one file touched - no changes",
+			input: []FileStat{
+				{
+					Name: "file1",
+				},
+			},
+			expected: " file1 | 0 \n",
+		},
+		{
+			description: "one file changed",
+			input: []FileStat{
+				{
+					Name:     "file1",
+					Addition: 1,
+				},
+			},
+			expected: " file1 | 1 +\n",
+		},
+		{
+			description: "one file changed with one addition and one deletion",
+			input: []FileStat{
+				{
+					Name:     ".github/workflows/git.yml",
+					Addition: 1,
+					Deletion: 1,
+				},
+			},
+			expected: " .github/workflows/git.yml | 2 +-\n",
+		},
+		{
+			description: "two files changed",
+			input: []FileStat{
+				{
+					Name:     ".github/workflows/git.yml",
+					Addition: 1,
+					Deletion: 1,
+				},
+				{
+					Name:     "cli/go-git/go.mod",
+					Addition: 4,
+					Deletion: 4,
+				},
+			},
+			expected: " .github/workflows/git.yml | 2 +-\n cli/go-git/go.mod         | 8 ++++----\n",
+		},
+		{
+			description: "three files changed",
+			input: []FileStat{
+				{
+					Name:     ".github/workflows/git.yml",
+					Addition: 3,
+					Deletion: 3,
+				},
+				{
+					Name:     "worktree.go",
+					Addition: 107,
+				},
+				{
+					Name:     "worktree_test.go",
+					Addition: 75,
+				},
+			},
+			expected: " .github/workflows/git.yml |   6 +++---\n" +
+				" worktree.go               | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++\n" +
+				" worktree_test.go          |  75 +++++++++++++++++++++++++++++++++++++++++++++++++++++\n",
+		},
+		{
+			description: "three files changed with deletions and additions",
+			input: []FileStat{
+				{
+					Name:     ".github/workflows/git.yml",
+					Addition: 3,
+					Deletion: 3,
+				},
+				{
+					Name:     "worktree.go",
+					Addition: 107,
+					Deletion: 217,
+				},
+				{
+					Name:     "worktree_test.go",
+					Addition: 75,
+					Deletion: 275,
+				},
+			},
+			expected: " .github/workflows/git.yml |   6 +++---\n" +
+				" worktree.go               | 324 ++++++++++++++++++-----------------------------------\n" +
+				" worktree_test.go          | 350 ++++++++++++-----------------------------------------\n",
+		},
+	}
+
+	for _, tc := range testCases {
+		c.Log("Executing test cases:", tc.description)
+		c.Assert(printStat(tc.input), Equals, tc.expected)
+	}
+}