From cb9c05a57b761919985193b5d53c9712f430ceac Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika@lmika.org>
Date: Fri, 7 Aug 2026 05:10:16 +0000
Subject: [PATCH] Added CSV to ASCII table

---
 textfilters.go      | 60 +++++++++++++++++++++++++++++
 textfilters_test.go | 92 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 152 insertions(+)
 create mode 100644 textfilters_test.go

diff --git a/textfilters.go b/textfilters.go
index e3ef6d7..ed8af7b 100644
--- a/textfilters.go
+++ b/textfilters.go
@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/base64"
+	"encoding/csv"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -12,6 +13,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"unicode/utf8"
 
 	"text/template"
 
@@ -184,6 +186,64 @@ var TextFilters = map[string]TextProcessor{
 			return TextFilterResponse{Output: dst.String()}, nil
 		},
 	},
+	"csv-to-ascii-table": {
+		Label: "Convert: CSV to ASCII Table",
+		Filter: func(ctx context.Context, input string) (resp TextFilterResponse, err error) {
+			endNL := ""
+			if strings.HasSuffix(input, "\n") {
+				endNL = "\n"
+			}
+
+			reader := csv.NewReader(strings.NewReader(input))
+			reader.FieldsPerRecord = -1
+			records, err := reader.ReadAll()
+			if err != nil {
+				return TextFilterResponse{}, err
+			}
+			if len(records) == 0 {
+				return TextFilterResponse{Output: input}, nil
+			}
+
+			var colWidths []int
+			for _, record := range records {
+				for i, cell := range record {
+					if i >= len(colWidths) {
+						colWidths = append(colWidths, 0)
+					}
+					colWidths[i] = max(colWidths[i], utf8.RuneCountInString(cell))
+				}
+			}
+
+			writeRow := func(dst *strings.Builder, cells []string) {
+				line := make([]string, len(colWidths))
+				for i, width := range colWidths {
+					cell := ""
+					if i < len(cells) {
+						cell = cells[i]
+					}
+					line[i] = cell + strings.Repeat(" ", width-utf8.RuneCountInString(cell))
+				}
+				dst.WriteString(strings.TrimRight(strings.Join(line, " "), " "))
+				dst.WriteString("\n")
+			}
+
+			dashes := make([]string, len(colWidths))
+			for i, width := range colWidths {
+				dashes[i] = strings.Repeat("-", width)
+			}
+			dashLine := strings.Join(dashes, " ") + "\n"
+
+			var dst strings.Builder
+			writeRow(&dst, records[0])
+			dst.WriteString(dashLine)
+			for _, record := range records[1:] {
+				writeRow(&dst, record)
+			}
+			dst.WriteString(dashLine)
+
+			return TextFilterResponse{Output: strings.TrimSuffix(dst.String(), "\n") + endNL}, nil
+		},
+	},
 	"convert-yaml-to-json": {
 		Label: "Convert: YAML to JSON",
 		Filter: func(ctx context.Context, input string) (resp TextFilterResponse, err error) {
diff --git a/textfilters_test.go b/textfilters_test.go
new file mode 100644
index 0000000..fde1603
--- /dev/null
+++ b/textfilters_test.go
@@ -0,0 +1,92 @@
+package main
+
+import (
+	"context"
+	"testing"
+)
+
+func TestCSVToASCIITable(t *testing.T) {
+	filter := TextFilters["csv-to-ascii-table"].Filter
+
+	tests := []struct {
+		name    string
+		input   string
+		want    string
+		wantErr bool
+	}{
+		{
+			name: "basic table with quoted value",
+			input: "alpha,bravo\n" +
+				"1,b\n" +
+				"\"long value\",something\n",
+			want: "alpha      bravo\n" +
+				"---------- ---------\n" +
+				"1          b\n" +
+				"long value something\n" +
+				"---------- ---------\n",
+		},
+		{
+			name:  "no trailing newline",
+			input: "a,b\n1,2",
+			want: "a b\n" +
+				"- -\n" +
+				"1 2\n" +
+				"- -",
+		},
+		{
+			name:  "quoted field containing comma",
+			input: "name,desc\n\"x, y\",z\n",
+			want: "name desc\n" +
+				"---- ----\n" +
+				"x, y z\n" +
+				"---- ----\n",
+		},
+		{
+			name:  "ragged rows padded with empty cells",
+			input: "a,b,c\n1\n2,3\n",
+			want: "a b c\n" +
+				"- - -\n" +
+				"1\n" +
+				"2 3\n" +
+				"- - -\n",
+		},
+		{
+			name:  "header only",
+			input: "one,two\n",
+			want: "one two\n" +
+				"--- ---\n" +
+				"--- ---\n",
+		},
+		{
+			name:  "empty input unchanged",
+			input: "",
+			want:  "",
+		},
+		{
+			name:    "invalid CSV returns error",
+			input:   "a,\"b\nc",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			resp, err := filter(context.Background(), tt.input)
+			if tt.wantErr {
+				if err == nil {
+					t.Fatalf("expected error, got output %q", resp.Output)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if resp.Output != tt.want {
+				t.Errorf("output mismatch\ngot:\n%s\nwant:\n%s", resp.Output, tt.want)
+			}
+			if resp.Append {
+				t.Errorf("Append should be false")
+			}
+		})
+	}
+}