//go:build windows

package tools

import (
	"bufio"
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"git.gopher.ink/mirrors2/AutoZero/diag"
)

// windowsBackend：Windows 桌面控制，全部走 PowerShell（系统自带，无 CGO）：
// 键盘用 System.Windows.Forms.SendKeys（Win 键不支持），鼠标与滚轮用
// user32.dll P/Invoke（SetCursorPos + mouse_event），截图用 System.Drawing。
// 使用持久化进程避免每次操作的 200-500ms 启动开销。
type windowsBackend struct {
	mu     sync.Mutex
	cmd    *exec.Cmd
	stdin  *bufio.Writer
	stdout *bufio.Scanner
}

func newGuiBackend() guiBackend { return &windowsBackend{} }

func (b *windowsBackend) Available() error {
	if _, err := exec.LookPath("powershell"); err != nil {
		return fmt.Errorf("powershell is required for computer use on Windows")
	}
	return nil
}

// PreflightPermissions Windows 暂无“首次引导授权”机制，依赖 Available() 的依赖检查。
func (b *windowsBackend) PreflightPermissions() []string { return nil }

// ensureStarted 确保持久化 PowerShell 进程已启动。
func (b *windowsBackend) ensureStarted() error {
	b.mu.Lock()
	defer b.mu.Unlock()
	if b.cmd != nil && b.cmd.Process != nil {
		return nil
	}
	cmd := exec.Command("powershell", "-NoProfile", "-NoLogo", "-NonInteractive")
	cmd.SysProcAttr = nil // 使用默认
	stdin, err := cmd.StdinPipe()
	if err != nil {
		return err
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return err
	}
	cmd.Stderr = diag.Indirect() // 不直连终端：TUI 在 alt-screen 下会被打穿
	if err := cmd.Start(); err != nil {
		return err
	}
	b.cmd = cmd
	b.stdin = bufio.NewWriter(stdin)
	b.stdout = bufio.NewScanner(stdout)
	// 注入 user32 类定义（只需一次）
	if _, err := b.exec(psUser32); err != nil {
		_ = cmd.Process.Kill()
		b.cmd = nil
		return fmt.Errorf("failed to inject user32: %w", err)
	}
	return nil
}

// exec 向持久化 PS 进程发送命令并读取输出。
// 使用唯一分隔符区分输出边界。
const psDelim = "__AG_END_"

func (b *windowsBackend) exec(script string) (string, error) {
	delim := fmt.Sprintf("Write-Output '%s'", psDelim)
	full := script + "; " + delim
	if _, err := b.stdin.WriteString(full + "\n"); err != nil {
		return "", err
	}
	if err := b.stdin.Flush(); err != nil {
		return "", err
	}
	var lines []string
	for b.stdout.Scan() {
		line := b.stdout.Text()
		if strings.Contains(line, psDelim) {
			break
		}
		lines = append(lines, line)
	}
	return strings.Join(lines, "\n"), nil
}

// restart 重启 PowerShell 进程（进程崩溃时恢复）。
func (b *windowsBackend) restart() {
	if b.cmd != nil && b.cmd.Process != nil {
		_ = b.cmd.Process.Kill()
		_, _ = b.cmd.Process.Wait()
	}
	b.cmd = nil
	_ = b.ensureStarted()
}

// runScript 在持久化进程失败时自动重启一次。
func (b *windowsBackend) runScript(script string) (string, error) {
	if err := b.ensureStarted(); err != nil {
		return "", err
	}
	out, err := b.exec(script)
	if err != nil {
		// 进程可能已死，重启后重试一次
		b.restart()
		if err2 := b.ensureStarted(); err2 != nil {
			return "", err
		}
		out, err = b.exec(script)
	}
	return out, err
}

// psUser32 是注入 user32 P/Invoke 的 PowerShell 片段（在 ensureStarted 时注入一次）。
const psUser32 = "Add-Type -TypeDefinition 'using System;using System.Runtime.InteropServices;public class AGUser32{[DllImport(\"user32.dll\")]public static extern bool SetCursorPos(int x,int y);[DllImport(\"user32.dll\")]public static extern void mouse_event(uint f,uint dx,uint dy,uint d,UIntPtr e);}' -ErrorAction SilentlyContinue"

// mouse_event flags：2=LEFTDOWN 4=LEFTUP 8=RIGHTDOWN 16=RIGHTUP 2048=WHEEL
const (
	meLeftDown  = "2"
	meLeftUp    = "4"
	meRightDown = "8"
	meRightUp   = "16"
	meWheel     = "2048"
	wheelNotch  = "120"
)

func (b *windowsBackend) Click(_ context.Context, x, y int, kind string) error {
	var bld strings.Builder
	fmt.Fprintf(&bld, "[AGUser32]::SetCursorPos(%d,%d); Start-Sleep -Milliseconds 80; ", x, y)
	switch kind {
	case "right":
		fmt.Fprintf(&bld, "[AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero); Start-Sleep -Milliseconds 40; [AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero);", meRightDown, meRightUp)
	case "double":
		fmt.Fprintf(&bld, "[AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero); Start-Sleep -Milliseconds 40; [AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero); Start-Sleep -Milliseconds 120; [AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero); Start-Sleep -Milliseconds 40; [AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero);", meLeftDown, meLeftUp, meLeftDown, meLeftUp)
	default:
		fmt.Fprintf(&bld, "[AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero); Start-Sleep -Milliseconds 40; [AGUser32]::mouse_event(%s,0,0,0,[UIntPtr]::Zero);", meLeftDown, meLeftUp)
	}
	_, err := b.runScript(bld.String())
	return err
}

func (b *windowsBackend) TypeText(_ context.Context, text string) error {
	seq := strings.ReplaceAll(sendKeysEscape(text), "'", "''")
	script := "Add-Type -AssemblyName System.Windows.Forms; " +
		"[System.Windows.Forms.SendKeys]::SendWait('" + seq + "');"
	_, err := b.runScript(script)
	return err
}

func (b *windowsBackend) KeyChord(_ context.Context, chordStr string) error {
	mods, main, err := parseChord(chordStr)
	if err != nil {
		return err
	}
	seq, err := chordToSendKeys(mods, main, chordStr)
	if err != nil {
		return err
	}
	seq = strings.ReplaceAll(seq, "'", "''")
	script := "Add-Type -AssemblyName System.Windows.Forms; " +
		"[System.Windows.Forms.SendKeys]::SendWait('" + seq + "');"
	_, err = b.runScript(script)
	return err
}

func (b *windowsBackend) Scroll(_ context.Context, direction string, amount int) error {
	delta := wheelNotch // 上滚为正
	if direction == "down" {
		delta = "-" + wheelNotch
	}
	var bld strings.Builder
	for i := 0; i < amount; i++ {
		fmt.Fprintf(&bld, "Start-Sleep -Milliseconds 90; [AGUser32]::mouse_event(%s,0,0,%s,[UIntPtr]::Zero); ", meWheel, delta)
	}
	_, err := b.runScript(bld.String())
	return err
}

func (b *windowsBackend) Screenshot(_ context.Context, region string) (string, error) {
	path := filepath.Join(os.TempDir(), fmt.Sprintf("autogo-shot-%d.png", time.Now().UnixNano()))
	psPath := strings.ReplaceAll(path, "'", "''")
	var bld strings.Builder
	bld.WriteString("Add-Type -AssemblyName System.Windows.Forms,System.Drawing; ")
	if region != "" {
		x, y, w, h, err := parseRegion(region)
		if err != nil {
			return "", err
		}
		fmt.Fprintf(&bld, "$bmp=New-Object System.Drawing.Bitmap(%d,%d); $g=[System.Drawing.Graphics]::FromImage($bmp); $g.CopyFromScreen(%d,%d,0,0,$bmp.Size); ", w, h, x, y)
	} else {
		bld.WriteString("$b=[System.Windows.Forms.SystemInformation]::VirtualScreen; $bmp=New-Object System.Drawing.Bitmap($b.Width,$b.Height); $g=[System.Drawing.Graphics]::FromImage($bmp); $g.CopyFromScreen($b.X,$b.Y,0,0,$bmp.Size); ")
	}
	bld.WriteString("$g.Dispose(); $bmp.Save('" + psPath + "',[System.Drawing.Imaging.ImageFormat]::Png); $bmp.Dispose();")
	if out, err := b.runScript(bld.String()); err != nil {
		_ = os.Remove(path)
		return "", fmt.Errorf("screenshot failed: %w: %s", err, out)
	}
	return path, nil
}