package internal

import (
	"crypto/rand"
	"encoding/base64"
	"math/big"
	"runtime"
	"strings"
	"unicode/utf16"
	"unicode/utf8"
)

// 平台信息（启动时确定）
var (
	isWindows  = runtime.GOOS == "windows"
	platformKey = runtime.GOOS + "-" + runtime.GOARCH
)

// toWinPath 将路径中的 / 替换为 \
func toWinPath(s string) string {
	return strings.ReplaceAll(s, "/", "\\")
}

// --- 字符串宽度 ---

func stringWidth(s string) int {
	w := 0
	for _, r := range s {
		w += runeWidth(r)
	}
	return w
}

func runeWidth(r rune) int {
	if r >= 0x1100 &&
		(r <= 0x115F || r == 0x2329 || r == 0x232A ||
			(r >= 0x2E80 && r <= 0xA4CF && r != 0x303F) ||
			(r >= 0xAC00 && r <= 0xD7A3) ||
			(r >= 0xF900 && r <= 0xFAFF) ||
			(r >= 0xFE10 && r <= 0xFE19) ||
			(r >= 0xFE30 && r <= 0xFE6F) ||
			(r >= 0xFF01 && r <= 0xFF60) ||
			(r >= 0xFFE0 && r <= 0xFFE6) ||
			(r >= 0x20000 && r <= 0x2FFFD) ||
			(r >= 0x30000 && r <= 0x3FFFD)) {
		return 2
	}
	return 1
}

func padRightByWidth(s string, targetW int) string {
	w := stringWidth(s)
	if w >= targetW {
		return s
	}
	return s + strings.Repeat(" ", targetW-w)
}

func truncateByWidth(s string, maxW int) string {
	w := 0
	for i := 0; i < len(s); {
		r, size := utf8.DecodeRuneInString(s[i:])
		rw := runeWidth(r)
		if w+rw > maxW {
			return s[:i]
		}
		w += rw
		i += size
	}
	return s
}

func wrapByWidth(s string, maxW int) []string {
	if maxW <= 0 || s == "" {
		return []string{s}
	}
	var lines []string
	for s != "" {
		cut := truncateByWidth(s, maxW)
		lines = append(lines, cut)
		s = s[len(cut):]
	}
	return lines
}

func fitWidth(s string, w int) string {
	return padRightByWidth(truncateByWidth(s, w), w)
}

// --- 视口 ---

func viewport(cursor, total, height int) (int, int) {
	if total <= height {
		return 0, total
	}
	half := height / 2
	start := cursor - half
	if start < 0 {
		start = 0
	}
	end := start + height
	if end > total {
		end = total
		start = end - height
		if start < 0 {
			start = 0
		}
	}
	return start, end
}

func padLinesTo(lines []string, w, target int) string {
	for len(lines) < target {
		lines = append(lines, strings.Repeat(" ", w))
	}
	return strings.Join(lines, "\n")
}

// --- Windows Terminal ---

func encodePSCommand(script string) string {
	u16 := utf16.Encode([]rune(script))
	b := make([]byte, len(u16)*2)
	for i, r := range u16 {
		b[i*2] = byte(r)
		b[i*2+1] = byte(r >> 8)
	}
	return base64.StdEncoding.EncodeToString(b)
}

func randRange(min, max int) int {
	n, _ := rand.Int(rand.Reader, big.NewInt(int64(max-min)))
	return min + int(n.Int64())
}