From 855a0aa1142461c9bf094a9a9127407604231db7 Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika@lmika.org>
Date: Sat, 14 Mar 2026 22:47:56 +1100
Subject: [PATCH] Added go template processor

---
 app.go         | 59 +++++++++++++++++++++++++++++++-------------------
 textfilters.go | 50 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 22 deletions(-)

diff --git a/app.go b/app.go
index a0d3a74..7148f8b 100644
--- a/app.go
+++ b/app.go
@@ -91,6 +91,33 @@ func (a *App) ProcessText(req ProcessTextRequest) {
 		return
 	}
 
+	applyFilter := func(filter TextFilter) {
+		resp, err := moslice.MapWithError(req.Input, func(span TextSpan) (TextSpan, error) {
+			outRes, err := filter(a.ctx, span.Text)
+			if err != nil {
+				return TextSpan{}, err
+			}
+
+			return TextSpan{
+				Text:   outRes.Output,
+				Pos:    span.Pos,
+				Len:    span.Len,
+				Append: outRes.Append,
+			}, nil
+		})
+		if err != nil {
+			runtime.EventsEmit(a.ctx, "set-statusbar-message", SetStatusbarMessage{
+				Message: fmt.Sprintf("Error running filter: %v", err.Error()),
+				Error:   true,
+			})
+			return
+		}
+
+		runtime.EventsEmit(a.ctx, "process-text-response", ProcessTextResponse{
+			Output: resp,
+		})
+	}
+
 	switch {
 	case filter.Analyze != nil:
 		inBfr := strings.Builder{}
@@ -114,30 +141,18 @@ func (a *App) ProcessText(req ProcessTextRequest) {
 			Message: msg,
 		})
 	case filter.Filter != nil:
-		resp, err := moslice.MapWithError(req.Input, func(span TextSpan) (TextSpan, error) {
-			outRes, err := filter.Filter(a.ctx, span.Text)
+		applyFilter(filter.Filter)
+	case filter.FilterWithArg != nil:
+		a.PromptUser(filter.FilterWithArg.Label, func(ans string) {
+			filter, err := filter.FilterWithArg.OnConfirm(a.ctx, ans)
 			if err != nil {
-				return TextSpan{}, err
+				runtime.EventsEmit(a.ctx, "set-statusbar-message", SetStatusbarMessage{
+					Message: fmt.Sprintf("Error running filter: %v", err.Error()),
+					Error:   true,
+				})
+				return
 			}
-
-			return TextSpan{
-				Text:   outRes.Output,
-				Pos:    span.Pos,
-				Len:    span.Len,
-				Append: outRes.Append,
-			}, nil
-		})
-		if err != nil {
-			runtime.EventsEmit(a.ctx, "set-statusbar-message", SetStatusbarMessage{
-				Message: fmt.Sprintf("Error running filter: %v", err.Error()),
-				Error:   true,
-			})
-			return
-
-		}
-
-		runtime.EventsEmit(a.ctx, "process-text-response", ProcessTextResponse{
-			Output: resp,
+			applyFilter(filter)
 		})
 	}
 }
diff --git a/textfilters.go b/textfilters.go
index 57ebdf1..7945a04 100644
--- a/textfilters.go
+++ b/textfilters.go
@@ -10,6 +10,8 @@ import (
 	"strconv"
 	"strings"
 
+	"text/template"
+
 	"gopkg.in/yaml.v3"
 	"ucl.lmika.dev/ucl"
 )
@@ -24,11 +26,20 @@ type TextProcessor struct {
 	// Analyses the supplied text. This is used for extracting information from the text input. The result
 	// will be displayed in the status bar. Multiple selected regions will be returned as a single string separated by line numbers.
 	Analyze TextAnalyzer
+
+	// FilterWithArg requests some input from the user. If the user supplies it, it will return a text filter
+	// to process the input.
+	FilterWithArg *FilterWithArg
 }
 
 type TextFilter func(ctx context.Context, input string) (resp TextFilterResponse, err error)
 type TextAnalyzer func(ctx context.Context, input string) (resp string, err error)
 
+type FilterWithArg struct {
+	Label     string
+	OnConfirm func(ctx context.Context, input string) (filter TextFilter, err error)
+}
+
 type TextFilterResponse struct {
 	Output string
 	Append bool
@@ -165,6 +176,45 @@ var TextFilters = map[string]TextProcessor{
 		},
 	},
 
+	"template-each-line": {
+		Label:       "Lines: Go Template…",
+		Description: "Evaluates the input as a Go template and replaces each line with the result.",
+		FilterWithArg: &FilterWithArg{
+			Label: "Template",
+			OnConfirm: func(ctx context.Context, prompt string) (filter TextFilter, err error) {
+				tmpl, err := template.New("").Parse(prompt)
+				if err != nil {
+					return nil, err
+				}
+
+				return func(ctx context.Context, input string) (resp TextFilterResponse, err error) {
+					var (
+						dst     bytes.Buffer
+						dstLine bytes.Buffer
+					)
+					scnr := bufio.NewScanner(strings.NewReader(input))
+					isFirst := true
+					for scnr.Scan() {
+						if isFirst {
+							isFirst = false
+						} else {
+							dst.WriteString("\n")
+						}
+
+						dstLine.Reset()
+						line := scnr.Text()
+						if err := tmpl.Execute(&dstLine, line); err != nil {
+							return TextFilterResponse{}, err
+						}
+						dst.WriteString(dstLine.String())
+					}
+
+					return TextFilterResponse{Output: dst.String()}, nil
+				}, nil
+			},
+		},
+	},
+
 	"ucl-evaluate": {
 		Label:       "UCL: Evaluate",
 		Description: "Evaluates the input as a UCL expression and displays the result in the status bar.",