From babc4c6f78683295b110a6ef98a656bc3544ea95 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luis=20Eduardo=20Jer=C3=A9z=20Gir=C3=B3n?=
 <eduardo.devop@gmail.com>
Date: Wed, 4 Sep 2024 23:59:55 -0600
Subject: [PATCH] Implement GetSHA256FromFS function to compute SHA256 hash
 from a filesystem. Add tests and sample files for validation

---
 .../util/cryptoutil/get_sha256_from_fs.go     | 44 +++++++++++++++++++
 .../cryptoutil/get_sha256_from_fs_test.go     | 32 ++++++++++++++
 .../get_sha256_from_fs_test_data/file1.txt    |  1 +
 .../get_sha256_from_fs_test_data/file2.txt    |  1 +
 .../subfolder/subfolder/file3.txt             |  1 +
 5 files changed, 79 insertions(+)
 create mode 100644 internal/util/cryptoutil/get_sha256_from_fs.go
 create mode 100644 internal/util/cryptoutil/get_sha256_from_fs_test.go
 create mode 100644 internal/util/cryptoutil/get_sha256_from_fs_test_data/file1.txt
 create mode 100644 internal/util/cryptoutil/get_sha256_from_fs_test_data/file2.txt
 create mode 100644 internal/util/cryptoutil/get_sha256_from_fs_test_data/subfolder/subfolder/file3.txt

diff --git a/internal/util/cryptoutil/get_sha256_from_fs.go b/internal/util/cryptoutil/get_sha256_from_fs.go
new file mode 100644
index 0000000..3836fe6
--- /dev/null
+++ b/internal/util/cryptoutil/get_sha256_from_fs.go
@@ -0,0 +1,44 @@
+package cryptoutil
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"io/fs"
+)
+
+// GetSHA256FromFS takes a fs.FS and returns a SHA256 hash of the combined contents
+// of all files in the filesystem.
+//
+// If there is an error, it returns an empty string.
+func GetSHA256FromFS(fsys fs.FS) string {
+	hash := sha256.New()
+
+	err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if d.IsDir() {
+			return nil
+		}
+
+		file, err := fsys.Open(path)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+
+		if _, err := io.Copy(hash, file); err != nil {
+			return err
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return ""
+	}
+
+	return hex.EncodeToString(hash.Sum(nil))
+}
diff --git a/internal/util/cryptoutil/get_sha256_from_fs_test.go b/internal/util/cryptoutil/get_sha256_from_fs_test.go
new file mode 100644
index 0000000..7179128
--- /dev/null
+++ b/internal/util/cryptoutil/get_sha256_from_fs_test.go
@@ -0,0 +1,32 @@
+package cryptoutil
+
+import (
+	"crypto/sha256"
+	"embed"
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+//go:embed get_sha256_from_fs_test_data/*
+var testFS embed.FS
+
+func TestGetSHA256FromFS_ValidFS(t *testing.T) {
+	hash := GetSHA256FromFS(testFS)
+	assert.NotEmpty(t, hash)
+
+	// To generate the expected hash, you must combine the contents of all the
+	// files in the test_data directory and calculate the SHA256 hash of the
+	// resulting string.
+	expectedHash := "d2c58b6783050a95542286a58250d4dc872877a6cf28610669516dcfacf954af"
+	assert.Equal(t, expectedHash, hash)
+}
+
+func TestGetSHA256FromFS_EmptyFS(t *testing.T) {
+	var emptyFS embed.FS
+	hash := GetSHA256FromFS(emptyFS)
+
+	expectedHash := sha256.New().Sum(nil)
+	assert.Equal(t, hex.EncodeToString(expectedHash), hash)
+}
diff --git a/internal/util/cryptoutil/get_sha256_from_fs_test_data/file1.txt b/internal/util/cryptoutil/get_sha256_from_fs_test_data/file1.txt
new file mode 100644
index 0000000..a732ac0
--- /dev/null
+++ b/internal/util/cryptoutil/get_sha256_from_fs_test_data/file1.txt
@@ -0,0 +1 @@
+file 1 contents
\ No newline at end of file
diff --git a/internal/util/cryptoutil/get_sha256_from_fs_test_data/file2.txt b/internal/util/cryptoutil/get_sha256_from_fs_test_data/file2.txt
new file mode 100644
index 0000000..211e228
--- /dev/null
+++ b/internal/util/cryptoutil/get_sha256_from_fs_test_data/file2.txt
@@ -0,0 +1 @@
+file 2 contents
\ No newline at end of file
diff --git a/internal/util/cryptoutil/get_sha256_from_fs_test_data/subfolder/subfolder/file3.txt b/internal/util/cryptoutil/get_sha256_from_fs_test_data/subfolder/subfolder/file3.txt
new file mode 100644
index 0000000..f0313b0
--- /dev/null
+++ b/internal/util/cryptoutil/get_sha256_from_fs_test_data/subfolder/subfolder/file3.txt
@@ -0,0 +1 @@
+file 3 contents
\ No newline at end of file