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

// Display functions: DISPBEGIN, DISPEND, SAVESCREEN, RESTSCREEN, ALERT

package hbrtl

import (
	"five/hbrt"
	"fmt"
	"strings"
)

var dispCount int // nesting count for DISPBEGIN/DISPEND

// DISPBEGIN() — begins display buffering
func DispBegin(t *hbrt.Thread) {
	t.Frame(0, 0)
	defer t.EndProc()
	dispCount++
	// In a real terminal this would hold screen updates;
	// for now just track the count.
	t.RetNil()
}

// DISPEND() — ends display buffering, flushes
func DispEnd(t *hbrt.Thread) {
	t.Frame(0, 0)
	defer t.EndProc()
	if dispCount > 0 {
		dispCount--
	}
	t.RetNil()
}

// DISPCOUNT() → nNesting
func DispCount(t *hbrt.Thread) {
	t.Frame(0, 0)
	defer t.EndProc()
	t.RetInt(int64(dispCount))
}

// SAVESCREEN([nTop, nLeft, nBottom, nRight]) → cBuffer
// Saves screen content as ANSI escape save sequence.
// Full implementation requires terminal screen buffer; this is a simplified version.
func SaveScreen(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()
	// Save cursor position and screen via ANSI
	fmt.Print("\033[?47h") // save screen (alt buffer)
	fmt.Print("\033[s")    // save cursor
	t.RetString("\033[SAVED]")
}

// RESTSCREEN([nTop, nLeft, nBottom, nRight,] cBuffer)
// Restores previously saved screen.
func RestScreen(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()
	fmt.Print("\033[u")    // restore cursor
	fmt.Print("\033[?47l") // restore screen (alt buffer)
	t.RetNil()
}

// ALERT(cMessage [, aOptions [, cColor [, nDelay]]]) → nChoice
// Displays a modal alert dialog in the terminal.
func Alert(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	msg := t.Local(1).AsString()

	// Parse options array
	options := []string{"Ok"}
	if nParams >= 2 && !t.Local(2).IsNil() {
		arr := t.Local(2).AsArray()
		if arr != nil && len(arr.Items) > 0 {
			options = make([]string, len(arr.Items))
			for i, v := range arr.Items {
				options[i] = v.AsString()
			}
		}
	}

	// Calculate box dimensions
	lines := strings.Split(msg, ";")
	maxW := 0
	for _, l := range lines {
		if len(l) > maxW {
			maxW = len(l)
		}
	}
	optLine := strings.Join(options, "  ")
	if len(optLine) > maxW {
		maxW = len(optLine)
	}
	maxW += 4 // padding

	// Draw centered box
	row := 8
	col := (80 - maxW) / 2
	if col < 0 {
		col = 0
	}

	// Top border
	fmt.Printf("\033[%d;%dH\033[7m%s\033[0m", row, col+1, strings.Repeat(" ", maxW))
	row++
	// Message lines
	for _, l := range lines {
		padded := fmt.Sprintf("  %-*s", maxW-2, l)
		if len(padded) > maxW {
			padded = padded[:maxW]
		}
		fmt.Printf("\033[%d;%dH\033[7m%s\033[0m", row, col+1, padded)
		row++
	}
	// Blank line
	fmt.Printf("\033[%d;%dH\033[7m%s\033[0m", row, col+1, strings.Repeat(" ", maxW))
	row++
	// Options line centered
	optPad := (maxW - len(optLine)) / 2
	optDisplay := fmt.Sprintf("%s%s%s", strings.Repeat(" ", optPad), optLine, strings.Repeat(" ", maxW-optPad-len(optLine)))
	fmt.Printf("\033[%d;%dH\033[7m%s\033[0m", row, col+1, optDisplay)
	row++
	// Bottom border
	fmt.Printf("\033[%d;%dH\033[7m%s\033[0m", row, col+1, strings.Repeat(" ", maxW))

	// Wait for selection
	selected := 1
	for {
		nKey := ReadKey()
		SetLastKey(nKey)
		switch nKey {
		case 4, 9: // Right, Tab
			selected++
			if selected > len(options) {
				selected = 1
			}
		case 19: // Left
			selected--
			if selected < 1 {
				selected = len(options)
			}
		case 13: // Enter
			t.RetInt(int64(selected))
			return
		case 27: // ESC
			t.RetInt(0)
			return
		}
	}
}