add -F filter by column flag (closes #13)

lib/filter.go

@@ -0,0 +1,82 @@
+/*
+Copyright © 2022-2024 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 (
+	"strings"
+
+	"github.com/lithammer/fuzzysearch/fuzzy"
+	"github.com/tlinden/tablizer/cfg"
+)
+
+/*
+ * [!]Match a  line, use fuzzy  search for normal pattern  strings and
+ * regexp otherwise.
+ */
+func matchPattern(c cfg.Config, line string) bool {
+	if c.UseFuzzySearch {
+		return fuzzy.MatchFold(c.Pattern, line)
+	}
+
+	return c.PatternR.MatchString(line)
+}
+
+/*
+ * Filter parsed data by fields. The  filter is positive, so if one or
+ * more filters match on a row, it  will be kept, otherwise it will be
+ * excluded.
+ */
+func FilterByFields(conf cfg.Config, data Tabdata) (Tabdata, bool, error) {
+	if len(conf.Filters) == 0 {
+		// no filters, no checking
+		return Tabdata{}, false, nil
+	}
+
+	newdata := data.CloneEmpty()
+
+	for _, row := range data.entries {
+		keep := true
+
+		for idx, header := range data.headers {
+			if !Exists(conf.Filters, strings.ToLower(header)) {
+				// do not filter by unspecified field
+				continue
+			}
+
+			if !conf.Filters[strings.ToLower(header)].MatchString(row[idx]) {
+				// there IS a filter, but it doesn't match
+				keep = false
+				break
+			}
+		}
+
+		if keep == !conf.InvertMatch {
+			// also apply -v
+			newdata.entries = append(newdata.entries, row)
+		}
+	}
+
+	return newdata, true, nil
+}
+
+func Exists[K comparable, V any](m map[K]V, v K) bool {
+	if _, ok := m[v]; ok {
+		return true
+	}
+	return false
+}