render.go

package main

import (
	"bytes"
	"fmt"
)

// ANSI escape sequences
const (
	esc = "\x1b["

	// Alternate screen buffer
	AltScreenOn  = "\x1b[?1049h"
	AltScreenOff = "\x1b[?1049l"

	// Cursor visibility
	HideCursor = esc + "?25l"
	ShowCursor = esc + "?25h"

	// Reset attributes
	Reset = esc + "0m"
)

// MoveCursor writes the escape sequence to move cursor to row, col (1-based).
func MoveCursor(buf *bytes.Buffer, row, col int) {
	fmt.Fprintf(buf, "%s%d;%dH", esc, row, col)
}

// BrightnessStyle returns the ANSI style string for a given brightness level (0–5).
func BrightnessStyle(brightness int) string {
	switch brightness {
	case 5: // head — bold bright white
		return esc + "1;97m"
	case 4: // bold bright green
		return esc + "1;92m"
	case 3: // normal green
		return esc + "0;32m"
	case 2: // dim green
		return esc + "2;32m"
	case 1: // dim gray
		return esc + "2;90m"
	default: // 0 — empty
		return ""
	}
}

// RenderFrame writes the full screen contents into buf using ANSI escape codes.
// It tracks the previous style to avoid redundant style changes.
func RenderFrame(buf *bytes.Buffer, screen *Screen) {
	var lastStyle string

	for r := 0; r < screen.Rows; r++ {
		MoveCursor(buf, r+1, 1)
		for c := 0; c < screen.Cols; c++ {
			cell := &screen.Grid[r][c]
			if cell.Brightness == 0 {
				if lastStyle != "" {
					buf.WriteString(Reset)
					lastStyle = ""
				}
				buf.WriteByte(' ')
				continue
			}
			style := BrightnessStyle(cell.Brightness)
			if style != lastStyle {
				buf.WriteString(style)
				lastStyle = style
			}
			buf.WriteRune(cell.Char)
		}
	}
	if lastStyle != "" {
		buf.WriteString(Reset)
	}
}