5 files changed, 550 insertions, 0 deletions
diff --git a/modules/git/languagestats/language_stats.go b/modules/git/languagestats/language_stats.go
new file mode 100644
index 0000000000..a71284c3e4
--- /dev/null
+++ b/modules/git/languagestats/language_stats.go
@@ -0,0 +1,65 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package languagestats
+
+import (
+	"context"
+	"strings"
+	"unicode"
+
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/git/attribute"
+)
+
+const (
+	fileSizeLimit int64 = 16 * 1024   // 16 KiB
+	bigFileSize   int64 = 1024 * 1024 // 1 MiB
+)
+
+// mergeLanguageStats mergers language names with different cases. The name with most upper case letters is used.
+func mergeLanguageStats(stats map[string]int64) map[string]int64 {
+	names := map[string]struct {
+		uniqueName string
+		upperCount int
+	}{}
+
+	countUpper := func(s string) (count int) {
+		for _, r := range s {
+			if unicode.IsUpper(r) {
+				count++
+			}
+		}
+		return count
+	}
+
+	for name := range stats {
+		cnt := countUpper(name)
+		lower := strings.ToLower(name)
+		if cnt >= names[lower].upperCount {
+			names[lower] = struct {
+				uniqueName string
+				upperCount int
+			}{uniqueName: name, upperCount: cnt}
+		}
+	}
+
+	res := make(map[string]int64, len(names))
+	for name, num := range stats {
+		res[names[strings.ToLower(name)].uniqueName] += num
+	}
+	return res
+}
+
+// GetFileLanguage tries to get the (linguist) language of the file content
+func GetFileLanguage(ctx context.Context, gitRepo *git.Repository, treeish, treePath string) (string, error) {
+	attributesMap, err := attribute.CheckAttributes(ctx, gitRepo, treeish, attribute.CheckAttributeOpts{
+		Attributes: []string{attribute.LinguistLanguage, attribute.GitlabLanguage},
+		Filenames:  []string{treePath},
+	})
+	if err != nil {
+		return "", err
+	}
+
+	return attributesMap[treePath].GetLanguage().Value(), nil
+}
diff --git a/modules/git/languagestats/language_stats_gogit.go b/modules/git/languagestats/language_stats_gogit.go
new file mode 100644
index 0000000000..418c05b157
--- /dev/null
+++ b/modules/git/languagestats/language_stats_gogit.go
@@ -0,0 +1,181 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build gogit
+
+package languagestats
+
+import (
+	"bytes"
+	"io"
+
+	"code.gitea.io/gitea/modules/analyze"
+	git_module "code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/git/attribute"
+	"code.gitea.io/gitea/modules/optional"
+
+	"github.com/go-enry/go-enry/v2"
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/object"
+)
+
+// GetLanguageStats calculates language stats for git repository at specified commit
+func GetLanguageStats(repo *git_module.Repository, commitID string) (map[string]int64, error) {
+	r, err := git.PlainOpen(repo.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	rev, err := r.ResolveRevision(plumbing.Revision(commitID))
+	if err != nil {
+		return nil, err
+	}
+
+	commit, err := r.CommitObject(*rev)
+	if err != nil {
+		return nil, err
+	}
+
+	tree, err := commit.Tree()
+	if err != nil {
+		return nil, err
+	}
+
+	checker, err := attribute.NewBatchChecker(repo, commitID, attribute.LinguistAttributes)
+	if err != nil {
+		return nil, err
+	}
+	defer checker.Close()
+
+	// sizes contains the current calculated size of all files by language
+	sizes := make(map[string]int64)
+	// by default we will only count the sizes of programming languages or markup languages
+	// unless they are explicitly set using linguist-language
+	includedLanguage := map[string]bool{}
+	// or if there's only one language in the repository
+	firstExcludedLanguage := ""
+	firstExcludedLanguageSize := int64(0)
+
+	err = tree.Files().ForEach(func(f *object.File) error {
+		if f.Size == 0 {
+			return nil
+		}
+
+		isVendored := optional.None[bool]()
+		isGenerated := optional.None[bool]()
+		isDocumentation := optional.None[bool]()
+		isDetectable := optional.None[bool]()
+
+		attrs, err := checker.CheckPath(f.Name)
+		if err == nil {
+			isVendored = attrs.GetVendored()
+			if isVendored.ValueOrDefault(false) {
+				return nil
+			}
+
+			isGenerated = attrs.GetGenerated()
+			if isGenerated.ValueOrDefault(false) {
+				return nil
+			}
+
+			isDocumentation = attrs.GetDocumentation()
+			if isDocumentation.ValueOrDefault(false) {
+				return nil
+			}
+
+			isDetectable = attrs.GetDetectable()
+			if !isDetectable.ValueOrDefault(true) {
+				return nil
+			}
+
+			hasLanguage := attrs.GetLanguage()
+			if hasLanguage.Value() != "" {
+				language := hasLanguage.Value()
+
+				// group languages, such as Pug -> HTML; SCSS -> CSS
+				group := enry.GetLanguageGroup(language)
+				if len(group) != 0 {
+					language = group
+				}
+
+				// this language will always be added to the size
+				sizes[language] += f.Size
+				return nil
+			}
+		}
+
+		if (!isVendored.Has() && analyze.IsVendor(f.Name)) ||
+			enry.IsDotFile(f.Name) ||
+			(!isDocumentation.Has() && enry.IsDocumentation(f.Name)) ||
+			enry.IsConfiguration(f.Name) {
+			return nil
+		}
+
+		// If content can not be read or file is too big just do detection by filename
+		var content []byte
+		if f.Size <= bigFileSize {
+			content, _ = readFile(f, fileSizeLimit)
+		}
+		if !isGenerated.Has() && enry.IsGenerated(f.Name, content) {
+			return nil
+		}
+
+		language := analyze.GetCodeLanguage(f.Name, content)
+		if language == enry.OtherLanguage || language == "" {
+			return nil
+		}
+
+		// group languages, such as Pug -> HTML; SCSS -> CSS
+		group := enry.GetLanguageGroup(language)
+		if group != "" {
+			language = group
+		}
+
+		included, checked := includedLanguage[language]
+		if !checked {
+			langtype := enry.GetLanguageType(language)
+			included = langtype == enry.Programming || langtype == enry.Markup
+			includedLanguage[language] = included
+		}
+		if included || isDetectable.ValueOrDefault(false) {
+			sizes[language] += f.Size
+		} else if len(sizes) == 0 && (firstExcludedLanguage == "" || firstExcludedLanguage == language) {
+			firstExcludedLanguage = language
+			firstExcludedLanguageSize += f.Size
+		}
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// If there are no included languages add the first excluded language
+	if len(sizes) == 0 && firstExcludedLanguage != "" {
+		sizes[firstExcludedLanguage] = firstExcludedLanguageSize
+	}
+
+	return mergeLanguageStats(sizes), nil
+}
+
+func readFile(f *object.File, limit int64) ([]byte, error) {
+	r, err := f.Reader()
+	if err != nil {
+		return nil, err
+	}
+	defer r.Close()
+
+	if limit <= 0 {
+		return io.ReadAll(r)
+	}
+
+	size := f.Size
+	if limit > 0 && size > limit {
+		size = limit
+	}
+	buf := bytes.NewBuffer(nil)
+	buf.Grow(int(size))
+	_, err = io.Copy(buf, io.LimitReader(r, limit))
+	return buf.Bytes(), err
+}
diff --git a/modules/git/languagestats/language_stats_nogogit.go b/modules/git/languagestats/language_stats_nogogit.go
new file mode 100644
index 0000000000..94cf9fff8c
--- /dev/null
+++ b/modules/git/languagestats/language_stats_nogogit.go
@@ -0,0 +1,217 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build !gogit
+
+package languagestats
+
+import (
+	"bytes"
+	"io"
+
+	"code.gitea.io/gitea/modules/analyze"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/git/attribute"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
+
+	"github.com/go-enry/go-enry/v2"
+)
+
+// GetLanguageStats calculates language stats for git repository at specified commit
+func GetLanguageStats(repo *git.Repository, commitID string) (map[string]int64, error) {
+	// We will feed the commit IDs in order into cat-file --batch, followed by blobs as necessary.
+	// so let's create a batch stdin and stdout
+	batchStdinWriter, batchReader, cancel, err := repo.CatFileBatch(repo.Ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer cancel()
+
+	writeID := func(id string) error {
+		_, err := batchStdinWriter.Write([]byte(id + "\n"))
+		return err
+	}
+
+	if err := writeID(commitID); err != nil {
+		return nil, err
+	}
+	shaBytes, typ, size, err := git.ReadBatchLine(batchReader)
+	if typ != "commit" {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, git.ErrNotExist{ID: commitID}
+	}
+
+	sha, err := git.NewIDFromString(string(shaBytes))
+	if err != nil {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, git.ErrNotExist{ID: commitID}
+	}
+
+	commit, err := git.CommitFromReader(repo, sha, io.LimitReader(batchReader, size))
+	if err != nil {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, err
+	}
+	if _, err = batchReader.Discard(1); err != nil {
+		return nil, err
+	}
+
+	tree := commit.Tree
+
+	entries, err := tree.ListEntriesRecursiveWithSize()
+	if err != nil {
+		return nil, err
+	}
+
+	checker, err := attribute.NewBatchChecker(repo, commitID, attribute.LinguistAttributes)
+	if err != nil {
+		return nil, err
+	}
+	defer checker.Close()
+
+	contentBuf := bytes.Buffer{}
+	var content []byte
+
+	// sizes contains the current calculated size of all files by language
+	sizes := make(map[string]int64)
+	// by default we will only count the sizes of programming languages or markup languages
+	// unless they are explicitly set using linguist-language
+	includedLanguage := map[string]bool{}
+	// or if there's only one language in the repository
+	firstExcludedLanguage := ""
+	firstExcludedLanguageSize := int64(0)
+
+	for _, f := range entries {
+		select {
+		case <-repo.Ctx.Done():
+			return sizes, repo.Ctx.Err()
+		default:
+		}
+
+		contentBuf.Reset()
+		content = contentBuf.Bytes()
+
+		if f.Size() == 0 {
+			continue
+		}
+
+		isVendored := optional.None[bool]()
+		isDocumentation := optional.None[bool]()
+		isDetectable := optional.None[bool]()
+
+		attrs, err := checker.CheckPath(f.Name())
+		attrLinguistGenerated := optional.None[bool]()
+		if err == nil {
+			if isVendored = attrs.GetVendored(); isVendored.ValueOrDefault(false) {
+				continue
+			}
+
+			if attrLinguistGenerated = attrs.GetGenerated(); attrLinguistGenerated.ValueOrDefault(false) {
+				continue
+			}
+
+			if isDocumentation = attrs.GetDocumentation(); isDocumentation.ValueOrDefault(false) {
+				continue
+			}
+
+			if isDetectable = attrs.GetDetectable(); !isDetectable.ValueOrDefault(true) {
+				continue
+			}
+
+			if hasLanguage := attrs.GetLanguage(); hasLanguage.Value() != "" {
+				language := hasLanguage.Value()
+
+				// group languages, such as Pug -> HTML; SCSS -> CSS
+				group := enry.GetLanguageGroup(language)
+				if len(group) != 0 {
+					language = group
+				}
+
+				// this language will always be added to the size
+				sizes[language] += f.Size()
+				continue
+			}
+		}
+
+		if (!isVendored.Has() && analyze.IsVendor(f.Name())) ||
+			enry.IsDotFile(f.Name()) ||
+			(!isDocumentation.Has() && enry.IsDocumentation(f.Name())) ||
+			enry.IsConfiguration(f.Name()) {
+			continue
+		}
+
+		// If content can not be read or file is too big just do detection by filename
+
+		if f.Size() <= bigFileSize {
+			if err := writeID(f.ID.String()); err != nil {
+				return nil, err
+			}
+			_, _, size, err := git.ReadBatchLine(batchReader)
+			if err != nil {
+				log.Debug("Error reading blob: %s Err: %v", f.ID.String(), err)
+				return nil, err
+			}
+
+			sizeToRead := size
+			discard := int64(1)
+			if size > fileSizeLimit {
+				sizeToRead = fileSizeLimit
+				discard = size - fileSizeLimit + 1
+			}
+
+			_, err = contentBuf.ReadFrom(io.LimitReader(batchReader, sizeToRead))
+			if err != nil {
+				return nil, err
+			}
+			content = contentBuf.Bytes()
+			if err := git.DiscardFull(batchReader, discard); err != nil {
+				return nil, err
+			}
+		}
+
+		// if "generated" attribute is set, use it, otherwise use enry.IsGenerated to guess
+		var isGenerated bool
+		if attrLinguistGenerated.Has() {
+			isGenerated = attrLinguistGenerated.Value()
+		} else {
+			isGenerated = enry.IsGenerated(f.Name(), content)
+		}
+		if isGenerated {
+			continue
+		}
+
+		// FIXME: Why can't we split this and the IsGenerated tests to avoid reading the blob unless absolutely necessary?
+		// - eg. do the all the detection tests using filename first before reading content.
+		language := analyze.GetCodeLanguage(f.Name(), content)
+		if language == "" {
+			continue
+		}
+
+		// group languages, such as Pug -> HTML; SCSS -> CSS
+		group := enry.GetLanguageGroup(language)
+		if group != "" {
+			language = group
+		}
+
+		included, checked := includedLanguage[language]
+		if !checked {
+			langType := enry.GetLanguageType(language)
+			included = langType == enry.Programming || langType == enry.Markup
+			includedLanguage[language] = included
+		}
+		if included || isDetectable.ValueOrDefault(false) {
+			sizes[language] += f.Size()
+		} else if len(sizes) == 0 && (firstExcludedLanguage == "" || firstExcludedLanguage == language) {
+			firstExcludedLanguage = language
+			firstExcludedLanguageSize += f.Size()
+		}
+	}
+
+	// If there are no included languages add the first excluded language
+	if len(sizes) == 0 && firstExcludedLanguage != "" {
+		sizes[firstExcludedLanguage] = firstExcludedLanguageSize
+	}
+
+	return mergeLanguageStats(sizes), nil
+}
diff --git a/modules/git/languagestats/language_stats_test.go b/modules/git/languagestats/language_stats_test.go
new file mode 100644
index 0000000000..b908ae6413
--- /dev/null
+++ b/modules/git/languagestats/language_stats_test.go
@@ -0,0 +1,46 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build !gogit
+
+package languagestats
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRepository_GetLanguageStats(t *testing.T) {
+	setting.AppDataPath = t.TempDir()
+	repoPath := "../tests/repos/language_stats_repo"
+	gitRepo, err := git.OpenRepository(t.Context(), repoPath)
+	require.NoError(t, err)
+	defer gitRepo.Close()
+
+	stats, err := GetLanguageStats(gitRepo, "8fee858da5796dfb37704761701bb8e800ad9ef3")
+	require.NoError(t, err)
+
+	assert.Equal(t, map[string]int64{
+		"Python": 134,
+		"Java":   112,
+	}, stats)
+}
+
+func TestMergeLanguageStats(t *testing.T) {
+	assert.Equal(t, map[string]int64{
+		"PHP":    1,
+		"python": 10,
+		"JAVA":   700,
+	}, mergeLanguageStats(map[string]int64{
+		"PHP":    1,
+		"python": 10,
+		"Java":   100,
+		"java":   200,
+		"JAVA":   400,
+	}))
+}
diff --git a/modules/git/languagestats/main_test.go b/modules/git/languagestats/main_test.go
new file mode 100644
index 0000000000..707d268c81
--- /dev/null
+++ b/modules/git/languagestats/main_test.go
@@ -0,0 +1,41 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package languagestats
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+)
+
+func testRun(m *testing.M) error {
+	gitHomePath, err := os.MkdirTemp(os.TempDir(), "git-home")
+	if err != nil {
+		return fmt.Errorf("unable to create temp dir: %w", err)
+	}
+	defer util.RemoveAll(gitHomePath)
+	setting.Git.HomePath = gitHomePath
+
+	if err = git.InitFull(context.Background()); err != nil {
+		return fmt.Errorf("failed to call Init: %w", err)
+	}
+
+	exitCode := m.Run()
+	if exitCode != 0 {
+		return fmt.Errorf("run test failed, ExitCode=%d", exitCode)
+	}
+	return nil
+}
+
+func TestMain(m *testing.M) {
+	if err := testRun(m); err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "Test failed: %v", err)
+		os.Exit(1)
+	}
+}