1 files changed, 131 insertions, 0 deletions
diff --git a/hi.go b/hi.go
new file mode 100644
index 0000000..ec927b3
--- /dev/null
+++ b/hi.go
@@ -0,0 +1,131 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func init() {
+	highlightColor = red
+	flag.Var((*colorFlag)(&highlightColor), "c", fmt.Sprintf("highlight `color` %s", colorsChoices))
+	background = defaultColor
+	flag.Var((*colorFlag)(&background), "bg", fmt.Sprintf("background `color` default|%s", colorsChoices))
+}
+
+var (
+	highlightColor ansiColor
+	background     ansiColor
+)
+
+//go:generate stringer -type=ansiColor -linecomment
+type ansiColor int
+
+const (
+	black ansiColor = iota
+	red
+	green
+	yellow
+	blue
+	magenta
+	cyan
+	white
+	defaultColor ansiColor = 9 // default
+)
+
+var colorsChoices = func() string {
+	nColors := white - black + 1
+	colors := make([]string, nColors)
+	for i := range nColors {
+		colors[i] = (black + i).String()
+	}
+	return strings.Join(colors, "|")
+}()
+
+func (c ansiColor) Foreground() int {
+	return 30 + int(c)
+}
+
+func (c ansiColor) Background() int {
+	return 40 + int(c)
+}
+
+type colorFlag int
+
+func (c *colorFlag) Set(val string) error {
+	var ac ansiColor
+	switch strings.ToLower(val) {
+	case "default":
+		ac = defaultColor
+	case "black":
+		ac = black
+	case "red":
+		ac = red
+	case "green":
+		ac = green
+	case "yellow":
+		ac = yellow
+	case "blue":
+		ac = blue
+	case "magenta":
+		ac = magenta
+	case "cyan":
+		ac = cyan
+	case "white":
+		ac = white
+	default:
+		return fmt.Errorf("unknown color %q (valid choices: %s)", val, colorsChoices)
+	}
+	*c = colorFlag(ac)
+	return nil
+}
+
+func (c *colorFlag) String() string {
+	return ansiColor(*c).String()
+}
+
+func run() error {
+	args := flag.Args()
+	if len(args) == 0 {
+		fmt.Fprintf(os.Stderr, "missing regexp to highlight\n")
+		flag.Usage()
+	}
+	if len(args) > 2 {
+		fmt.Fprintf(os.Stderr, "too many positional arguments\n")
+		flag.Usage()
+	}
+	highlightRE, err := regexp.CompilePOSIX(args[0])
+	if err != nil {
+		return fmt.Errorf("invalid highlight regexp: %s", err)
+	}
+	foregroundColor := highlightColor.Foreground()
+	backgroundColor := background.Background()
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		line := scanner.Text()
+		loc := highlightRE.FindStringIndex(line)
+		if loc == nil {
+			fmt.Printf("%s\n", line)
+			continue
+		}
+		startIdx, endIdx := loc[0], loc[1]
+		fmt.Printf("%s\033[%d;%dm%s\033[39;49m%s\n", line[:startIdx], foregroundColor, backgroundColor, line[startIdx:endIdx], line[endIdx:])
+	}
+	return scanner.Err()
+}
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: hi [OPTIONS] REGEXP\n")
+		flag.PrintDefaults()
+		os.Exit(2)
+	}
+	flag.Parse()
+	if err := run(); err != nil {
+		fmt.Fprintf(os.Stderr, "hi: %s\n", err)
+		os.Exit(1)
+	}
+}