tablizer/lib/io.go

/*
Copyright © 2022 Thomas von Dein

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

package lib

import (
	"errors"
	"fmt"
	"io"
	"os"

	"github.com/tlinden/tablizer/cfg"
)

const RWRR = 0755

func ProcessFiles(conf *cfg.Config, args []string) error {
	fds, pattern, err := determineIO(conf, args)

	if err != nil {
		return err
	}

	if err := conf.PreparePattern(pattern); err != nil {
		return err
	}

	for _, fd := range fds {
		data, err := Parse(*conf, fd)
		if err != nil {
			return err
		}

		err = PrepareColumns(conf, &data)
		if err != nil {
			return err
		}

		printData(os.Stdout, *conf, &data)
	}

	return nil
}

func determineIO(conf *cfg.Config, args []string) ([]io.Reader, string, error) {
	var filehandles []io.Reader

	var pattern string

	var haveio bool

	stat, _ := os.Stdin.Stat()
	if (stat.Mode() & os.ModeCharDevice) == 0 {
		// we're reading from STDIN, which takes precedence over file args
		filehandles = append(filehandles, os.Stdin)

		if len(args) > 0 {
			// ignore any args > 1
			pattern = args[0]
			conf.Pattern = args[0] // used for colorization by printData()
		}

		haveio = true
	} else if len(args) > 0 {
		// threre were args left, take a look
		if args[0] == "-" {
			// in traditional unix programs a dash denotes STDIN (forced)
			filehandles = append(filehandles, os.Stdin)
			haveio = true
		} else {
			if _, err := os.Stat(args[0]); err != nil {
				// first  one is  not a  file, consider  it as  regexp and
				// shift arg list
				pattern = args[0]
				conf.Pattern = args[0] // used for colorization by printData()
				args = args[1:]
			}

			if len(args) > 0 {
				// consider any other args as files
				for _, file := range args {
					filehandle, err := os.OpenFile(file, os.O_RDONLY, RWRR)

					if err != nil {
						return nil, "", fmt.Errorf("failed to read input file %s: %w", file, err)
					}

					filehandles = append(filehandles, filehandle)
					haveio = true
				}
			}
		}
	}

	if !haveio {
		return nil, "", errors.New("no file specified and nothing to read on stdin")
	}

	return filehandles, pattern, nil
}