package main

import (
	"errors"
	"flag"
	"fmt"
	"log"
)

func run() error {
	flag.Parse()
	args := flag.Args()
	if len(args) < 1 {
		return errors.New("no command specified")
	}
	switch args[0] {
	case "setalpha":
		flags := flag.NewFlagSet("setalpha", flag.ContinueOnError)
		var alpha int
		flags.IntVar(&alpha, "alpha", 127, "sets the target alpha")
		flags.Parse(args[1:])
		for _, path := range flags.Args() {
			err := setAlpha(path, alpha)
			if err != nil {
				return fmt.Errorf("couldn't set alpha of '%s'; error: %v", path, err)
			}
		}
	case "gray":
		flags := flag.NewFlagSet("gray", flag.ContinueOnError)
		flags.Parse(args[1:])
		for _, path := range flags.Args() {
			err := convertToGray(path)
			if err != nil {
				return fmt.Errorf("couldn't convert to grayscale of '%s'; error: %v", path, err)
			}
		}
	case "crop":
		flags := flag.NewFlagSet("crop", flag.ContinueOnError)
		var rect string
		var resize string
		var dir string
		flags.StringVar(&rect, "crop", "", "sets the crop rectangle \"x1,y1,y1,y2\"")
		flags.StringVar(&resize, "resize", "", "sets the target size, \"width,height\", if not specified the crop rectangle size is used")
		flags.StringVar(&dir, "dir", "", "crops all images in the specified directory (recursively)")
		flags.Parse(args[1:])

		cropRect, err := parseRect(rect)
		if err != nil {
			return fmt.Errorf("crop rectangle is invalid: error: %v", err)
		}
		var size *point
		if len(resize) != 0 {
			p, err := parsePoint(resize)
			if err != nil {
				return fmt.Errorf("resize parameter is invalid: error: %v", err)
			}
			size = &p
		}

		var files []string
		if len(dir) == 0 {
			files = flags.Args()
		} else {
			files, err = scanDir(dir)
			if err != nil {
				return fmt.Errorf("couldn't find files to crop; error: %v", err)
			}
		}

		for _, path := range files {
			err := crop(path, cropRect, size)
			if err != nil {
				return fmt.Errorf("couldn't crop '%s'; error: %v", path, err)
			}
		}
	}
	return nil
}

func main() {
	if err := run(); err != nil {
		log.Fatal(err)
	}
}