// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Cross-platform ANSI key-sequence decoder. Each termios_<os>.go
// collects bytes from the terminal in raw mode, then hands them here
// for classification. The decoder output (ASCII or 0xE0-0xFC pseudo-
// code) is the same on every OS so debugtui.go can stay platform-
// neutral.

package hbrt

// decodeDebugKey translates a raw byte buffer captured in TTY/console
// raw mode into a single logical key. Returns 0 when nothing was read.
// Pseudo-codes 0xE0-0xE3 cover arrow keys; 0xF5-0xFC cover F5-F12.
func decodeDebugKey(buf []byte, n int) int {
	if n == 0 {
		return 0
	}
	if buf[0] != 0x1B {
		return int(buf[0])
	}
	if n == 1 {
		return 0x1B // bare ESC
	}
	if n >= 3 && buf[1] == '[' {
		// Arrow keys: ESC [ A/B/C/D
		switch buf[2] {
		case 'A':
			return 0xE0 // Up
		case 'B':
			return 0xE1 // Down
		case 'C':
			return 0xE2 // Right
		case 'D':
			return 0xE3 // Left
		}
		// F5-F12: ESC [ 1 5 ~ through ESC [ 2 4 ~
		if n >= 4 && buf[n-1] == '~' {
			switch string(buf[2 : n-1]) {
			case "15":
				return 0xF5
			case "17":
				return 0xF6
			case "18":
				return 0xF7
			case "19":
				return 0xF8
			case "20":
				return 0xF9
			case "21":
				return 0xFA
			case "23":
				return 0xFB
			case "24":
				return 0xFC
			}
		}
	}
	return 0 // ignore unknown ESC sequences — never quit on them
}