tablizer/lib/parser.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 (
	"bufio"
	"errors"
	"fmt"
	"github.com/alecthomas/repr"
	"io"
	"regexp"
	"strings"
)

// contains a whole parsed table
type Tabdata struct {
	maxwidthHeader int   // longest header
	maxwidthPerCol []int // max width per column
	columns        int
	headerIndices  []map[string]int // [ {beg=>0, end=>17}, ... ]
	headers        []string         // [ "ID", "NAME", ...]
	entries        [][]string
}

/*
   Parse tabular input. We split the  header (first line) by 2 or more
   spaces, remember the positions of  the header fields. We then split
   the data (everything after the first line) by those positions. That
   way we can turn "tabular data" (with fields containing whitespaces)
   into real tabular data. We re-tabulate our input if you will.
*/
func parseFile(input io.Reader, pattern string) (Tabdata, error) {
	data := Tabdata{}

	var scanner *bufio.Scanner
	var spaces = `\s\s+|$`

	if len(Separator) > 0 {
		spaces = Separator
	}

	hadFirst := false
	spacefinder := regexp.MustCompile(spaces)
	beg := 0

	scanner = bufio.NewScanner(input)

	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		values := []string{}

		patternR, err := regexp.Compile(pattern)
		if err != nil {
			return data, errors.Unwrap(fmt.Errorf("Regexp pattern %s is invalid: %w", pattern, err))
		}

		if !hadFirst {
			// header processing
			parts := spacefinder.FindAllStringIndex(line, -1)
			data.columns = len(parts)
			// if Debug {
			// 	fmt.Println(parts)
			// }

			// process all header fields
			for _, part := range parts {
				// if Debug {
				// 	fmt.Printf("Part: <%s>\n", string(line[beg:part[0]]))
				//}

				// current field
				head := string(line[beg:part[0]])

				// register begin and end of field within line
				indices := make(map[string]int)
				indices["beg"] = beg
				if part[0] == part[1] {
					indices["end"] = 0
				} else {
					indices["end"] = part[1] - 1
				}

				// register widest header field
				headerlen := len(head)
				if headerlen > data.maxwidthHeader {
					data.maxwidthHeader = headerlen
				}

				// register fields data
				data.headerIndices = append(data.headerIndices, indices)
				data.headers = append(data.headers, head)

				// end of current field == begin of next one
				beg = part[1]

				// done
				hadFirst = true
			}
		} else {
			// data processing
			if len(pattern) > 0 {
				if !patternR.MatchString(line) {
					continue
				}
			}

			idx := 0 // we cannot use the header index, because we could exclude columns
			for _, index := range data.headerIndices {
				value := ""

				if index["end"] == 0 {
					value = string(line[index["beg"]:])
				} else {
					value = string(line[index["beg"]:index["end"]])
				}

				width := len(strings.TrimSpace(value))

				if len(data.maxwidthPerCol)-1 < idx {
					data.maxwidthPerCol = append(data.maxwidthPerCol, width)
				} else {
					if width > data.maxwidthPerCol[idx] {
						data.maxwidthPerCol[idx] = width
					}
				}

				// if Debug {
				// 	fmt.Printf("<%s> ", value)
				// }
				values = append(values, strings.TrimSpace(value))

				idx++
			}
			data.entries = append(data.entries, values)
		}
	}

	if scanner.Err() != nil {
		return data, errors.Unwrap(fmt.Errorf("Regexp pattern %s is invalid: %w", pattern, scanner.Err()))
	}

	if Debug {
		repr.Print(data)
	}

	return data, nil
}