Defined color mappings for Go

Instead of printing out the contents early on (which wouldn't allow it to work
with '-n'), I skip the loop that applies colors based on the regular expressions.

color.go

@@ -26,8 +26,9 @@ var possibleColors map[string]color = map[string]color{
 	"WHITE":   {"WHITE", colorData.New(colorData.FgWhite)},
 	"GRAY":    {"GRAY", colorData.New(colorData.FgWhite, colorData.Faint)},
 	// Last three numbers are RGB. Reference https://en.wikipedia.org/wiki/ANSI_escape_code for what the first two numbers mean.
-	"ORANGE": {"ORANGE", colorData.New(38, 2, 255, 153, 28)},
+	"ORANGE":   {"ORANGE", colorData.New(38, 2, 255, 153, 28)},
-	"NONE":   {"NONE", colorData.New()},
+	"DARKBLUE": {"DARKBLUE", colorData.New(38, 2, 0, 112, 255)},
+	"NONE":     {"NONE", colorData.New()},
 }
 
 // Apply the given color 'clr' to all units in 'units', within the indices
@@ -52,7 +53,7 @@ func newColor(colorString string) (color, error) {
 // newColorMust is similar to newColor, but prints an error and exits if the given color isn't valid.
 func newColorMust(colorString string) color {
 	if clr, err := newColor(colorString); err != nil {
-		printAndExit(err.Error())
+		printErrAndExit(err.Error())
 		panic(err) // NEVER REACHED
 	} else {
 		return clr

config.go

@@ -2,13 +2,76 @@ package main
 
 import (
 	"ccat/stack"
+	"embed"
+	"errors"
+	"io/fs"
 	"os"
+	"os/user"
+	"path/filepath"
 	"regexp"
+	"runtime"
 	"strings"
 
 	"gopkg.in/yaml.v2"
 )
 
+//go:embed config
+var storedConfigs embed.FS // Embed the folder containing config files
+
+func runningOnWindows() bool {
+	return runtime.GOOS == "windows"
+}
+
+// generateDefaultConfigs is used to generate a folder of default config files
+// for common languages. These default config files are embedded into the program, and will
+// be outputted into a directory.
+//
+// If there is an error encountered, the error is returned.
+func generateDefaultConfigs() error {
+
+	var configOutputPath string // Location of config files, depends on OS
+	if runningOnWindows() {
+		configOutputPath = "%APPDATA%\\ccat"
+	} else {
+		currentUser, err := user.Current()
+		if err != nil {
+			panic(err)
+		}
+		configOutputPath = filepath.Join("/home/" + currentUser.Username + "/.config/ccat/")
+	}
+	err := os.MkdirAll(configOutputPath, 0755)
+	if err != nil {
+		if os.IsExist(err) {
+			return errors.New("Directory already exists.")
+		} else {
+			return errors.New("Unable to create directory.")
+		}
+	}
+
+	// Copy each folder from the embedded filesystem, into the destination path
+	err = fs.WalkDir(storedConfigs, "config", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() { // Skip directories
+			return nil
+		}
+		relPath, _ := filepath.Rel("config", path)
+		dstPath := filepath.Join(configOutputPath, relPath) // Destination path
+
+		data, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+
+		if err := os.WriteFile(dstPath, data, 0644); err != nil {
+			return err
+		}
+		return nil
+	})
+	return nil
+}
+
 // loadConfig takes in the filename of a config file. It reads the file,
 // and returns a stack of RegColors, with the item at the bottom being the one that
 // was read first. This ensures that, _when accessing the RegColors in the stack, the last

config/go.conf

@@ -0,0 +1,30 @@
+# Priority decreases going downward ie. If two regexes match the same piece of
+# text, the one defined earlier will take precedence over the one defined later.
+# Comments
+'//.*': GRAY
+'/\*[^*]*\*+(?:[^/*][^*]*\*+)*/': GRAY
+# Numbers and special values
+'\b\-?[0-9]*\b': MAGENTA
+'\b(true|false)\b': MAGENTA
+'\b(nil)\b': MAGENTA
+# Strings in double quotes and backticks
+'"(.*?)"': BLUE
+'`(.*?)`': BLUE
+# Bytes / Runes
+"'(.)'": BLUE
+"'\\\\(.)'": BLUE # The escape backslash needs to be escaped as well
+# Assignments and comparisons
+'(?:\s|\b)(=|==|!=|<=|>=)(\s|\b)' : CYAN
+'(&&)|(\|\|)': CYAN
+# Keywords
+'\b(if|else|for|range|go|func|return|break|continue)\b': CYAN
+'\b(import|var|const|type|struct)\b': CYAN
+# Built-in Functions
+'\b(panic|len)\b': DARKBLUE
+# Functions from packages (package name and function name separated by dot)
+'\b(\w*\.\w*)\b': DARKBLUE
+# Data Types
+'\b(bool|byte|rune|string|interface|map|chan)\b': YELLOW
+'\b(u?int)(8|16|32|64)?\b': YELLOW
+'\b(float)(32|64)\b': YELLOW
+'\b(complex)(64|128)\b': YELLOW

errors.go

@@ -5,7 +5,7 @@ import (
 	"os"
 )
 
-func printAndExit(errorStr string) {
+func printErrAndExit(errorStr string) {
 	fmt.Printf("ERROR: %s\n", errorStr)
 	os.Exit(1)
 }

main.go

@@ -1,9 +1,13 @@
 package main
 
 import (
+	"bytes"
 	"errors"
+	"flag"
 	"fmt"
+	"math"
 	"os"
+	"os/user"
 	"path/filepath"
 )
 
@@ -15,7 +19,7 @@ func fileExists(filename string) bool {
 	} else if errors.Is(err, os.ErrNotExist) {
 		return false
 	} else {
-		printAndExit(err.Error())
+		printErrAndExit(err.Error())
 		return false // NEVER REACHED
 	}
 }
@@ -24,7 +28,7 @@ func fileExists(filename string) bool {
 // the file doesn't exist.
 func mustExist(filename string) {
 	if fileExists(filename) != true {
-		printAndExit(os.ErrNotExist.Error())
+		printErrAndExit(os.ErrNotExist.Error())
 	}
 }
 
@@ -32,12 +36,12 @@ func mustExist(filename string) {
 // It returns two values: the first is true if the config file exists.
 // If it does, the second value is the config filename.
 // If it doesn't, the second value is blank and can be ignored.
-func getConfig(extension string) (bool, string) {
+func getConfig(configPath, extension string) (bool, string) {
 	if extension == "" {
 		return false, ""
 	}
 	// Assuming the file has an extension
-	fileName := "config/" + extension[1:] + ".conf"
+	fileName := filepath.Join(configPath, extension[1:]+".conf")
 	if exists := fileExists(fileName); exists == false {
 		return false, ""
 	} else {
@@ -52,41 +56,87 @@ func printFile(fileName string) {
 	mustExist(fileName)
 	data, err := os.ReadFile(fileName)
 	if err != nil {
-		printAndExit(err.Error())
+		printErrAndExit(err.Error())
 	}
 	fmt.Print(string(data))
 	return
 }
 
+// computeLineNumDigits computes the number of digits in the number of lines
+// in the given byte array.
+func computeLineNumDigits(data []byte) int {
+	numLines := bytes.Count(data, []byte{'\n'}) + 1
+	return int(math.Round(math.Log10(float64(numLines))))
+}
+
 func main() {
+	disableColorFlag := flag.Bool("d", false, "Disable color")
+	lineNumberFlag := flag.Bool("n", false, "Print line numbers")
+	// Used only if lineNumberFlag is true
+	var lineNumDigits int
+	var lineNum int
+	flag.Parse()
+
+	// Check if config exists. If it doesn't, generate the config files.
+	var configPath string // Location of config files, depends on OS
+	if runningOnWindows() {
+		configPath = "%APPDATA%\\ccat"
+	} else {
+		currentUser, err := user.Current()
+		if err != nil {
+			panic(err)
+		}
+		configPath = filepath.Join("/home/" + currentUser.Username + "/.config/ccat/")
+	}
+	if _, err := os.Stat(configPath); os.IsNotExist(err) {
+		generateDefaultConfigs()
+	}
 
 	// Check if user has provided a file name
-	if len(os.Args) != 2 {
+	if len(flag.Args()) < 1 {
-		printAndExit("Invalid number of arguments")
+		printErrAndExit("No File specified")
 	}
-	fileName := os.Args[1]
+	fileName := flag.Args()[0]
+
+	// Check if file exists.
 	mustExist(fileName)
 
 	extension := filepath.Ext(fileName)
-	configExists, configFilename := getConfig(extension)
+	configExists, configFilename := getConfig(configPath, extension)
-	// If the given file has no corresponding config, print it out
+	// If the given file has no corresponding config, print the file out and exit.
-	// and exit.
 	if configExists == false {
 		printFile(fileName)
 		return
 	}
+
+	// To save computing time, determine here if the file is empty. If it is, exit
+	// the program.
+	finfo, err := os.Stat(fileName)
+	if err != nil {
+		panic(err)
+	}
+	if finfo.Size() == 0 {
+		os.Exit(0)
+	}
+
+	// Assuming the file is not empty...
 	// If the given file has a config, load the config into a stack of regColors.
 	regColorStack, err := loadConfig(configFilename)
 	if err != nil {
-		printAndExit(err.Error())
+		printErrAndExit(err.Error())
 	}
 
 	// Load the input file into a colorunit slice (units) and a byte slice (data)
 	units, data, err := loadInputFile(fileName)
 	if err != nil {
-		printAndExit(err.Error())
+		printErrAndExit(err.Error())
 	}
 
+	// If the '-n' flag is set, compute the number of digits in the number of lines
+	// in the file, to determine the padding for the line numbers.
+	if *lineNumberFlag {
+		lineNumDigits = computeLineNumDigits(data)
+	}
 	// For each regular expression in the stack, apply it to the byte slice. Find
 	// the first and last index of all matches of the regex. Then apply the corresponding color
 	// to every character within these indices.
@@ -94,7 +144,9 @@ func main() {
 	// The infinite for loop exists, because I couldn't figure out a way to pop an element from
 	// the stack inside the 'for' statement. The loop exits when the 'pop' call returns 'false',
 	// indicating that the stack is empty.
-	for {
+	//
+	// The loop is also only run if the 'disable color' flag is not set.
+	for *disableColorFlag == false {
 		regclr, ok := regColorStack.Pop()
 		// regColorStack.Pop() returns false when there are no more elements to pop
 		if ok != true {
@@ -115,7 +167,21 @@ func main() {
 	}
 
 	// After all possible regexes have been matched, print out the contents of 'units'.
-	for _, unit := range units {
+
+	// If the line number flag is set, initialize the lineNum variable and print the first line number
+	// with the appropriate padding.
+	if *lineNumberFlag {
+		lineNum = 1
+		fmt.Printf("   %*d  ", lineNumDigits, lineNum)
+		lineNum++
+	}
+	for idx, unit := range units {
 		unit.print()
+		// If the flag is set and we encounter a newline (and the newline isn't a trailing newline),
+		// then print the next line number.
+		if *lineNumberFlag && unit.ch == '\n' && idx != len(units)-1 {
+			fmt.Printf("   %*d  ", lineNumDigits, lineNum)
+			lineNum++
+		}
 	}
 }