This is the implementation i got using AI, definitely need some time to process and learn how each component actually works even though I got the overall gist of it.

fzf-logcat.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"os/exec"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"

	"golang.org/x/term"
)

type LogcatFilter struct {
	filter     string
	filterMu   sync.RWMutex
	logBuffer  []string
	bufferMu   sync.RWMutex
	maxBuffer  int
	termWidth  int
	termHeight int
}

func NewLogcatFilter() *LogcatFilter {
	width, height, err := term.GetSize(int(os.Stdout.Fd()))
	if err != nil || width == 0 || height == 0 {
		width = 80
		height = 24
	}
	
	return &LogcatFilter{
		maxBuffer:  10000,
		logBuffer:  make([]string, 0),
		termWidth:  width,
		termHeight: height,
	}
}

func (lf *LogcatFilter) UpdateTermSize() {
	width, height, err := term.GetSize(int(os.Stdout.Fd()))
	if err == nil && width > 0 && height > 0 {
		lf.termWidth = width
		lf.termHeight = height
	}
}

func (lf *LogcatFilter) SetFilter(filter string) {
	lf.filterMu.Lock()
	defer lf.filterMu.Unlock()
	lf.filter = strings.ToLower(strings.TrimSpace(filter))
}

func (lf *LogcatFilter) GetFilter() string {
	lf.filterMu.RLock()
	defer lf.filterMu.RUnlock()
	return lf.filter
}

func (lf *LogcatFilter) AddLogLine(line string) {
	lf.bufferMu.Lock()
	defer lf.bufferMu.Unlock()
	
	lf.logBuffer = append(lf.logBuffer, line)
	if len(lf.logBuffer) > lf.maxBuffer {
		lf.logBuffer = lf.logBuffer[1:]
	}
}

func (lf *LogcatFilter) MatchesFilter(line string) bool {
	filter := lf.GetFilter()
	if filter == "" {
		return true
	}
	return strings.Contains(strings.ToLower(line), filter)
}

func (lf *LogcatFilter) GetRecentFilteredLogs(count int) []string {
	lf.bufferMu.RLock()
	defer lf.bufferMu.RUnlock()
	
	filter := lf.GetFilter()
	var filtered []string
	
	for i := len(lf.logBuffer) - 1; i >= 0 && len(filtered) < count; i-- {
		line := lf.logBuffer[i]
		if filter == "" || strings.Contains(strings.ToLower(line), filter) {
			filtered = append([]string{line}, filtered...)
		}
	}
	
	return filtered
}

type Display struct {
	filter        *LogcatFilter
	inputBuffer   string
	cursorPos     int
	mu           sync.Mutex
	logRegionEnd  int // Last row of log region
	inputRow      int // Row for input
	separatorRow  int // Row for separator
}

func NewDisplay(filter *LogcatFilter) *Display {
	return &Display{
		filter: filter,
	}
}

func (d *Display) updateLayout() {
	d.filter.UpdateTermSize()
	d.separatorRow = d.filter.termHeight - 1
	d.inputRow = d.filter.termHeight
	d.logRegionEnd = d.filter.termHeight - 2
}

func (d *Display) setupTerminal() {
	// Save current terminal state
	fmt.Print("\033[?1049h") // Alternative screen buffer
	fmt.Print("\033[H\033[2J") // Clear screen
	fmt.Print("\033[?25h") // Show cursor
	
	d.updateLayout()
	d.setupScrollRegion()
	d.drawStaticUI()
}

func (d *Display) setupScrollRegion() {
	// Set scrolling region to exclude the bottom 2 lines (separator + input)
	fmt.Printf("\033[1;%dr", d.logRegionEnd)
}

func (d *Display) restoreTerminal() {
	fmt.Print("\033[?25h") // Show cursor
	fmt.Print("\033[1;%dr", d.filter.termHeight) // Reset scroll region
	fmt.Print("\033[?1049l") // Exit alternative screen buffer
}

func (d *Display) drawStaticUI() {
	d.mu.Lock()
	defer d.mu.Unlock()
	
	// Draw separator (fixed position)
	fmt.Printf("\033[%d;1H", d.separatorRow)
	separator := strings.Repeat("─", d.filter.termWidth)
	fmt.Print("\033[2m" + separator + "\033[0m")
	
	// Draw input line (fixed position)
	d.redrawInputLine()
}

func (d *Display) redrawInputLine() {
	fmt.Printf("\033[%d;1H", d.inputRow)
	fmt.Print("\033[K") // Clear line
	
	prompt := "> "
	displayText := d.inputBuffer
	
	// Handle text that's too long for terminal
	maxInputWidth := d.filter.termWidth - len(prompt) - 1
	startPos := 0
	
	if len(displayText) > maxInputWidth {
		if d.cursorPos > maxInputWidth-10 {
			startPos = d.cursorPos - maxInputWidth + 10
			if startPos < 0 {
				startPos = 0
			}
		}
		if startPos+maxInputWidth > len(displayText) {
			startPos = len(displayText) - maxInputWidth
			if startPos < 0 {
				startPos = 0
			}
		}
		displayText = displayText[startPos:startPos+maxInputWidth]
	}
	
	fmt.Printf("%s%s", prompt, displayText)
	
	// Position cursor
	cursorCol := len(prompt) + d.cursorPos - startPos + 1
	if cursorCol > d.filter.termWidth {
		cursorCol = d.filter.termWidth
	}
	if cursorCol < len(prompt)+1 {
		cursorCol = len(prompt) + 1
	}
	
	fmt.Printf("\033[%d;%dH", d.inputRow, cursorCol)
}

func (d *Display) printLogLine(line string) {
	d.mu.Lock()
	defer d.mu.Unlock()
	
	// Save cursor position
	fmt.Print("\033[s")
	
	// Move to log region and print (will scroll naturally within the region)
	fmt.Printf("\033[%d;1H", d.logRegionEnd)
	fmt.Println(line)
	
	// Restore cursor position (back to input area)
	fmt.Print("\033[u")
}

func (d *Display) refreshLogDisplay() {
	d.mu.Lock()
	defer d.mu.Unlock()
	
	// Save cursor position
	fmt.Print("\033[s")
	
	// Clear log region
	for i := 1; i <= d.logRegionEnd; i++ {
		fmt.Printf("\033[%d;1H\033[K", i)
	}
	
	// Display recent filtered logs
	logs := d.filter.GetRecentFilteredLogs(d.logRegionEnd)
	for i, line := range logs {
		fmt.Printf("\033[%d;1H%s", i+1, line)
	}
	
	// Restore cursor position
	fmt.Print("\033[u")
}

func (d *Display) handleResize() {
	d.updateLayout()
	
	// Reset scroll region
	d.setupScrollRegion()
	
	// Redraw everything
	fmt.Print("\033[H\033[2J")
	d.refreshLogDisplay()
	d.drawStaticUI()
}

func (d *Display) addChar(ch byte) {
	if d.cursorPos < len(d.inputBuffer) {
		d.inputBuffer = d.inputBuffer[:d.cursorPos] + string(ch) + d.inputBuffer[d.cursorPos:]
	} else {
		d.inputBuffer += string(ch)
	}
	d.cursorPos++
	
	d.filter.SetFilter(d.inputBuffer)
	d.refreshLogDisplay()
	d.redrawInputLine()
}

func (d *Display) deleteChar() {
	if d.cursorPos > 0 {
		if d.cursorPos < len(d.inputBuffer) {
			d.inputBuffer = d.inputBuffer[:d.cursorPos-1] + d.inputBuffer[d.cursorPos:]
		} else {
			d.inputBuffer = d.inputBuffer[:len(d.inputBuffer)-1]
		}
		d.cursorPos--
		
		d.filter.SetFilter(d.inputBuffer)
		d.refreshLogDisplay()
		d.redrawInputLine()
	}
}

func (d *Display) moveCursorLeft() {
	if d.cursorPos > 0 {
		d.cursorPos--
		d.redrawInputLine()
	}
}

func (d *Display) moveCursorRight() {
	if d.cursorPos < len(d.inputBuffer) {
		d.cursorPos++
		d.redrawInputLine()
	}
}

func (d *Display) clearInput() {
	d.inputBuffer = ""
	d.cursorPos = 0
	d.filter.SetFilter("")
	d.refreshLogDisplay()
	d.redrawInputLine()
}

func (d *Display) moveToBeginning() {
	d.cursorPos = 0
	d.redrawInputLine()
}

func (d *Display) moveToEnd() {
	d.cursorPos = len(d.inputBuffer)
	d.redrawInputLine()
}

func main() {
	if _, err := exec.LookPath("adb"); err != nil {
		fmt.Fprintf(os.Stderr, "Error: adb command not found. Please install Android SDK platform tools.\n")
		os.Exit(1)
	}

	filter := NewLogcatFilter()
	display := NewDisplay(filter)

	oldState, err := term.MakeRaw(int(os.Stdin.Fd()))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error setting up terminal: %v\n", err)
		os.Exit(1)
	}

	display.setupTerminal()

	cleanup := func() {
		term.Restore(int(os.Stdin.Fd()), oldState)
		display.restoreTerminal()
	}
	defer cleanup()

	// Handle signals
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM, syscall.SIGWINCH)

	// Start logcat
	cmd := exec.Command("adb", "logcat", "-v", "brief")
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		cleanup()
		fmt.Fprintf(os.Stderr, "Error creating stdout pipe: %v\n", err)
		os.Exit(1)
	}

	if err := cmd.Start(); err != nil {
		cleanup()
		fmt.Fprintf(os.Stderr, "Error starting adb logcat: %v\n", err)
		os.Exit(1)
	}

	logChan := make(chan string, 100)
	inputChan := make(chan []byte, 10)

	// Read logcat output
	go func() {
		scanner := bufio.NewScanner(stdout)
		headerSkipped := false
		for scanner.Scan() {
			line := strings.TrimSpace(scanner.Text())
			if line == "" {
				continue
			}
			
			if !headerSkipped {
				if strings.Contains(line, "beginning of") || 
				   strings.Contains(line, "-----") ||
				   len(line) < 10 {
					continue
				}
				headerSkipped = true
			}
			
			logChan <- line
		}
	}()

	// Read user input
	go func() {
		buffer := make([]byte, 3)
		for {
			n, err := os.Stdin.Read(buffer)
			if err != nil || n == 0 {
				time.Sleep(1 * time.Millisecond)
				continue
			}
			inputChan <- buffer[:n]
		}
	}()

	// Main loop
	for {
		select {
		case sig := <-sigChan:
			switch sig {
			case syscall.SIGWINCH:
				display.handleResize()
			default:
				cmd.Process.Kill()
				cleanup()
				fmt.Println("Exiting...")
				os.Exit(0)
			}

		case logLine := <-logChan:
			filter.AddLogLine(logLine)
			if filter.MatchesFilter(logLine) {
				display.printLogLine(logLine)
			}

		case input := <-inputChan:
			if len(input) == 1 {
				switch input[0] {
				case 3: // Ctrl+C
					cmd.Process.Kill()
					cleanup()
					fmt.Println("Exiting...")
					os.Exit(0)
				case 127, 8: // Backspace
					display.deleteChar()
				case 21: // Ctrl+U
					display.clearInput()
				case 1: // Ctrl+A
					display.moveToBeginning()
				case 5: // Ctrl+E
					display.moveToEnd()
				default:
					if input[0] >= 32 && input[0] <= 126 {
						display.addChar(input[0])
					}
				}
			} else if len(input) == 3 && input[0] == 27 && input[1] == 91 {
				switch input[2] {
				case 68: // Left arrow
					display.moveCursorLeft()
				case 67: // Right arrow
					display.moveCursorRight()
				}
			}

		default:
			time.Sleep(1 * time.Millisecond)
		}
	}
}