feat(processor): add chroma dep, lexer resolution and drop rules

internal/processor/engine.go

@@ -0,0 +1,63 @@
+package processor
+
+import (
+	"path/filepath"
+	"strings"
+
+	"github.com/alecthomas/chroma/v2"
+	"github.com/alecthomas/chroma/v2/lexers"
+)
+
+type Options struct {
+	Inline        bool
+	Block         bool
+	PreserveLines bool
+	InRange       func(line int) bool
+}
+
+type LineChange struct {
+	Num      int
+	Original string
+	Result   string
+	Action   string
+}
+
+func resolveLexer(filename string) chroma.Lexer {
+	ext := strings.TrimPrefix(strings.ToLower(filepath.Ext(filename)), ".")
+	var l chroma.Lexer
+	if ext == "less" {
+		l = lexers.Get("SCSS")
+	} else {
+		l = lexers.Match("f." + ext)
+	}
+	if l == nil {
+		return nil
+	}
+	return chroma.Coalesce(l)
+}
+
+func shouldDrop(tt chroma.TokenType, opts Options) bool {
+	if tt == chroma.CommentPreproc || tt == chroma.CommentPreprocFile {
+		return false
+	}
+	if opts.Inline {
+		return tt == chroma.CommentSingle || tt == chroma.CommentHashbang || tt == chroma.CommentSpecial
+	}
+	if opts.Block {
+		return tt == chroma.CommentMultiline
+	}
+	return tt.Category() == chroma.Comment
+}
+
+func isCommentType(tt chroma.TokenType) bool {
+	return tt.Category() == chroma.Comment && tt != chroma.CommentPreproc && tt != chroma.CommentPreprocFile
+}
+
+func leadingWhitespace(s string) string {
+	for i, r := range s {
+		if r != ' ' && r != '\t' {
+			return s[:i]
+		}
+	}
+	return s
+}

internal/processor/engine_test.go

@@ -0,0 +1,58 @@
+package processor
+
+import (
+	"testing"
+
+	"github.com/alecthomas/chroma/v2"
+)
+
+func TestResolveLexer(t *testing.T) {
+	cases := []struct {
+		file string
+		want string
+	}{
+		{"a.c", "C"},
+		{"a.go", "Go"},
+		{"a.js", "JavaScript"},
+		{"a.rs", "Rust"},
+		{"a.html", "HTML"},
+		{"a.less", "SCSS"},
+		{"a.conf", ""},
+	}
+	for _, c := range cases {
+		l := resolveLexer(c.file)
+		got := ""
+		if l != nil {
+			got = l.Config().Name
+		}
+		if got != c.want {
+			t.Errorf("resolveLexer(%q) = %q, want %q", c.file, got, c.want)
+		}
+	}
+}
+
+func TestShouldDrop(t *testing.T) {
+	def := Options{}
+	inline := Options{Inline: true}
+	block := Options{Block: true}
+	cases := []struct {
+		tt   chroma.TokenType
+		opts Options
+		want bool
+	}{
+		{chroma.CommentSingle, def, true},
+		{chroma.CommentMultiline, def, true},
+		{chroma.CommentPreproc, def, false},
+		{chroma.CommentPreprocFile, def, false},
+		{chroma.CommentSingle, inline, true},
+		{chroma.CommentMultiline, inline, false},
+		{chroma.CommentSingle, block, false},
+		{chroma.CommentMultiline, block, true},
+		{chroma.KeywordType, def, false},
+	}
+	for _, c := range cases {
+		if got := shouldDrop(c.tt, c.opts); got != c.want {
+			t.Errorf("shouldDrop(%v, %+v) = %v, want %v", c.tt, c.opts, got, c.want)
+		}
+	}
+}