package main

import (
	"compress/gzip"
	"fmt"
	"io"
	"math/rand"
	"os"
	"path/filepath"
	"time"

	"github.com/urfave/cli"
)

func main() {
	app := cli.NewApp()
	app.Name = "gogzip"
	app.Description = "golang `compress/gzip` cli, in likeness to GNU gzip"
	app.Version = "0.1"
	app.Flags = []cli.Flag{
		cli.BoolFlag{
			Name:  "a,ascii",
			Usage: "(noop here for compatibility)",
		},
		cli.BoolFlag{
			Name:  "c,stdout,to-stdout",
			Usage: "write output to stdout",
		},
		cli.BoolFlag{
			Name:  "d",
			Usage: "decompress",
		},
		cli.BoolFlag{
			Name:  "f,force",
			Usage: "force",
		},
		cli.BoolFlag{
			Name:  "k,keep",
			Usage: "keep original file when compressing",
		},
		cli.BoolFlag{
			Name:  "l,list",
			Usage: "for each compressed file, list the size tables",
		},
		cli.BoolFlag{
			Name:  "L,license",
			Usage: "license",
		},
		cli.BoolFlag{
			Name:  "N,name",
			Usage: "license",
		},
		cli.BoolFlag{
			Name:  "q,quiet",
			Usage: "suppress warnings",
		},
		cli.BoolFlag{
			Name:  "r,recursive",
			Usage: "if any of the file arguments are directories, recurse them",
		},
		cli.StringFlag{
			Name:  "S,suffix",
			Value: ".gz",
			Usage: "when compressing use suffix value instead of default",
		},
		cli.BoolFlag{
			Name:  "synchronous",
			Usage: "sync",
		},
		cli.BoolFlag{
			Name:  "#,best,fast",
			Usage: "compression level",
		},
		cli.BoolFlag{
			Name:  "rsyncable",
			Usage: "rsyncable",
		},
		cli.VersionFlag,
	}
	app.Action = defaultAction
	app.Run(os.Args)
}

func defaultAction(c *cli.Context) error {
	// TODO check whether stdin or its a pty terminal, if no args

	if c.Bool("decompress") {
		if c.NArg() == 0 {
			grdr, err := gzip.NewReader(os.Stdin)
			if err != nil {
				return cli.NewExitError(err, 2)
			}
			defer grdr.Close()
			if _, err = io.Copy(os.Stdout, grdr); err != nil {
				return cli.NewExitError(err, 2)
			}
			return nil
		}

		for _, arg := range c.Args() {
			err := func() error {
				fh, err := os.OpenFile(arg, os.O_RDONLY, 0600)
				if err != nil {
					return err
				}
				defer fh.Close()

				fi, err := fh.Stat()
				if err != nil {
					return err
				}

				newName := gzBasename(c, arg)
				newFh, err := os.OpenFile(newName, os.O_CREATE|os.O_WRONLY, fi.Mode())
				if err != nil {
					return err
				}
				defer newFh.Close()

				if _, err := io.Copy(newFh, fh); err != nil {
					return err
				}

				return nil
			}()
			if err != nil {
				return cli.NewExitError(err, 2)
			}
		}

		return nil
	}

	return nil
}

func gzBasename(c *cli.Context, s string) string {
	if filepath.Ext(s) == c.String("suffix") {
		return filepath.Base(s)
	}
	return fmt.Sprint("%s.%d", s, rand.New(rand.NewSource(time.Now().UnixNano())).Intn(100))
}