package app

import (
	"fmt"
	"strings"

	"github.com/harrybrwn/patterm/internal/vt"
)

func renderScreenSnapshot(text string, cursor vt.CursorState, layout terminalLayout) []byte {
	lines := strings.Split(strings.ReplaceAll(text, "\r\n", "\n"), "\n")
	cols := int(layout.childCols())
	rows := int(layout.childRows())

	var b strings.Builder
	b.WriteString("\x1b[?25l")
	for r := 0; r < rows; r++ {
		line := ""
		if r < len(lines) {
			line = truncateCells(lines[r], cols)
		}
		fmt.Fprintf(&b, "\x1b[%d;%dH%s", int(layout.mainTop)+r, int(layout.mainLeft), padRight(line, cols))
	}

	if cursor.Visible {
		row := int(layout.mainTop) + int(cursor.Row)
		col := int(layout.mainLeft) + int(cursor.Col)
		if row < int(layout.mainTop) {
			row = int(layout.mainTop)
		}
		maxRow := int(layout.mainTop) + rows - 1
		if row > maxRow {
			row = maxRow
		}
		if col < int(layout.mainLeft) {
			col = int(layout.mainLeft)
		}
		maxCol := int(layout.mainLeft) + cols - 1
		if col > maxCol {
			col = maxCol
		}
		fmt.Fprintf(&b, "\x1b[?25h\x1b[%d;%dH", row, col)
	}
	return []byte(b.String())
}

func renderCursor(cursor vt.CursorState, layout terminalLayout) []byte {
	cols := int(layout.childCols())
	rows := int(layout.childRows())
	row := int(layout.mainTop) + int(cursor.Row)
	col := int(layout.mainLeft) + int(cursor.Col)
	if row < int(layout.mainTop) {
		row = int(layout.mainTop)
	}
	maxRow := int(layout.mainTop) + rows - 1
	if row > maxRow {
		row = maxRow
	}
	if col < int(layout.mainLeft) {
		col = int(layout.mainLeft)
	}
	maxCol := int(layout.mainLeft) + cols - 1
	if col > maxCol {
		col = maxCol
	}
	return []byte(fmt.Sprintf("\x1b[?25h\x1b[%d;%dH", row, col))
}

func truncateCells(s string, width int) string {
	if width <= 0 {
		return ""
	}
	if visibleLen(s) <= width {
		return s
	}
	var b strings.Builder
	n := 0
	for _, r := range s {
		if n >= width {
			break
		}
		b.WriteRune(r)
		n++
	}
	return b.String()
}