From cbf2c76a29975d77677ff162c0f7db27e280f4da Mon Sep 17 00:00:00 2001
From: Sameer Rahmani <lxsameer@gnu.org>
Date: Wed, 23 Nov 2022 21:09:40 +0000
Subject: [PATCH] Make a simple draft of filter

It reads the input and render it via /dev/tty and let the user
select the lines that are important and finaly write them back
to stdout.
---
 filter.go | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 utils.go  |  53 ++++++++++++++++++
 2 files changed, 215 insertions(+)
 create mode 100644 filter.go
 create mode 100644 utils.go

diff --git a/filter.go b/filter.go
new file mode 100644
index 0000000..f017576
--- /dev/null
+++ b/filter.go
@@ -0,0 +1,162 @@
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/gdamore/tcell/v2"
+)
+
+var xmax int
+var ymax int
+
+var highlight tcell.Style
+
+func drawText(s tcell.Screen, x1, y1, x2, y2 int, style tcell.Style, text string) {
+	row := y1
+	col := x1
+	for _, r := range []rune(text) {
+		s.SetContent(col, row, r, nil, style)
+		col++
+		if col >= x2 {
+			row++
+			col = x1
+		}
+		if row > y2 {
+			break
+		}
+	}
+}
+
+func Render(s tcell.Screen, inputs Items, lowerBound int, upperBound int, current int) {
+	y := 1
+	status := fmt.Sprintf("Current: %d | lower: %d | upper: %d | max: %d", current, lowerBound, upperBound, ymax)
+	drawText(s, 0, 0, xmax-1, 1, tcell.StyleDefault, status)
+	for i, item := range (*inputs)[lowerBound:upperBound] {
+		style := tcell.StyleDefault
+		var txt string
+
+		if current == lowerBound+i {
+			style = highlight
+		}
+
+		if item.Selected {
+			txt = fmt.Sprintf("XXXX | %s", item.Text)
+		} else {
+			txt = fmt.Sprintf("%04d | %s", lowerBound+i, item.Text)
+		}
+
+		drawText(s, 0, y, xmax-1, y+1, style, txt)
+		y += 1
+	}
+}
+
+func main() {
+	input, err := ReadFromStdin()
+	if err != nil {
+		log.Fatalf("%+v", err)
+	}
+
+	defStyle := tcell.StyleDefault.Background(tcell.ColorDefault).Foreground(tcell.ColorDefault)
+	highlight = tcell.StyleDefault.Background(tcell.ColorDarkGray).Foreground(tcell.ColorWhite)
+	currentLine := 0
+
+	// Initialize screen
+	tty, err := tcell.NewDevTty()
+	if err != nil {
+		log.Fatalf("%+v", err)
+	}
+
+	s, err := tcell.NewTerminfoScreenFromTty(tty)
+	if err != nil {
+		log.Fatalf("%+v", err)
+	}
+	if err := s.Init(); err != nil {
+		log.Fatalf("%+v", err)
+	}
+	s.SetStyle(defStyle)
+	s.Clear()
+	xmax, ymax = s.Size()
+
+	quit := func() {
+		// You have to catch panics in a defer, clean up, and
+		// re-raise them - otherwise your application can
+		// die without leaving any diagnostic trace.
+		maybePanic := recover()
+		s.Fini()
+		if maybePanic != nil {
+			panic(maybePanic)
+		}
+	}
+	defer quit()
+
+	// Here's an example of how to inject a keystroke where it will
+	// be picked up by the next PollEvent call.  Note that the
+	// queue is LIFO, it has a limited length, and PostEvent() can
+	// return an error.
+	// s.PostEvent(tcell.NewEventKey(tcell.KeyRune, rune('a'), 0))
+
+	done := false
+	lowerBound := 0
+	upperBound := min(ymax-3, len(*input))
+	// Event loop
+	for {
+		if done {
+			break
+		}
+		s.Clear()
+		//window := (*input)[lowerBound:upperBound]
+		Render(s, input, lowerBound, upperBound, currentLine)
+
+		// Update screen
+		s.Show()
+
+		// Poll event
+		ev := s.PollEvent()
+
+		// Process event
+		switch ev := ev.(type) {
+		case *tcell.EventResize:
+			s.Sync()
+		case *tcell.EventKey:
+			if ev.Key() == tcell.KeyEscape || ev.Key() == tcell.KeyCtrlC || ev.Rune() == 'q' {
+				return
+			} else if ev.Key() == tcell.KeyEnter {
+				done = true
+				break
+			} else if ev.Key() == tcell.KeyCtrlL {
+				s.Sync()
+			} else if ev.Rune() == 'C' || ev.Rune() == 'c' {
+				s.Clear()
+			} else if ev.Rune() == ' ' {
+				item := (*input)[currentLine]
+				item.Selected = !item.Selected
+			} else if ev.Key() == tcell.KeyUp || ev.Rune() == 'r' {
+				if currentLine > 0 {
+					currentLine -= 1
+				}
+				if currentLine <= lowerBound && currentLine != 0 {
+					lowerBound -= 1
+					upperBound -= 1
+				}
+
+			} else if ev.Key() == tcell.KeyDown || ev.Rune() == 'n' {
+				if currentLine < len(*input)-1 {
+					currentLine += 1
+				}
+
+				if currentLine >= upperBound && currentLine != len(*input)-1 {
+					lowerBound += 1
+					upperBound += 1
+				}
+			}
+		}
+	}
+	s.Fini()
+	for _, item := range *input {
+		if item.Selected {
+			fmt.Println(item.Text)
+		}
+	}
+
+}
diff --git a/utils.go b/utils.go
new file mode 100644
index 0000000..5c6418f
--- /dev/null
+++ b/utils.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+)
+
+type Item struct {
+	Text     string
+	Selected bool
+}
+
+type Items = *[]*Item
+
+func NewItem(text string) *Item {
+	return &Item{
+		Text:     text,
+		Selected: false,
+	}
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func ReadFromStdin() (Items, error) {
+	info, err := os.Stdin.Stat()
+	if err != nil {
+		panic(err)
+	}
+
+	if info.Mode()&os.ModeCharDevice != 0 {
+		return nil, fmt.Errorf("The command is intended to work with pipes. For example `git log | filter | xarg | ...`")
+	}
+
+	reader := bufio.NewReader(os.Stdin)
+	var output []*Item
+
+	for {
+		input, _, err := reader.ReadLine()
+		if err != nil && err == io.EOF {
+			break
+		}
+		item := NewItem(string(input))
+		output = append(output, item)
+	}
+	return &output, nil
+}