package updater

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	"scout/pkg/scoutpkg"
)

var ErrPlatformInstallRequired = errors.New("当前平台需要宿主应用接入系统安装流程")

// LaunchRequest 描述平台适配器启动已确认版本所需的信息。
type LaunchRequest struct {
	Release ReleasePointer
	Args    []string
	Env     []string
}

// PlatformAdapter 隔离更新器与不同操作系统的启动和安装机制。
// Prepare、Activate 和健康确认仍由 Manager 统一负责，宿主应用只需在需要时注入适配器。
type PlatformAdapter interface {
	Platform() string
	Validate(ReleasePointer) error
	Install(context.Context, ReleasePointer) error
	Launch(context.Context, LaunchRequest) (*exec.Cmd, error)
}

type nativeAdapter struct {
	platform string
}

type androidAdapter struct{}

// NewPlatformAdapter 返回指定平台的默认适配器。
func NewPlatformAdapter(platform string) (PlatformAdapter, error) {
	normalized, err := scoutpkg.NormalizePlatform(platform)
	if err != nil {
		return nil, err
	}
	if normalized == "android" {
		return androidAdapter{}, nil
	}
	return nativeAdapter{platform: normalized}, nil
}

// NewNativeAdapter 创建桌面平台默认适配器，便于宿主应用显式注入。
func NewNativeAdapter(platform string) (PlatformAdapter, error) {
	normalized, err := scoutpkg.NormalizePlatform(platform)
	if err != nil {
		return nil, err
	}
	if normalized == "android" {
		return nil, errors.New("Android 必须使用宿主应用提供的安装适配器")
	}
	return nativeAdapter{platform: normalized}, nil
}

func (adapter nativeAdapter) Platform() string {
	return adapter.platform
}

func (adapter nativeAdapter) Validate(release ReleasePointer) error {
	if release.Platform != "" && release.Platform != adapter.platform && release.Platform != "any" {
		return fmt.Errorf("更新版本平台不匹配: %s", release.Platform)
	}
	executable, err := releaseExecutable(release)
	if err != nil {
		return err
	}
	info, err := os.Stat(executable)
	if err != nil {
		return fmt.Errorf("平台适配器检查程序入口失败: %w", err)
	}
	if info.IsDir() {
		return errors.New("程序入口不能是目录")
	}
	if adapter.platform == "macos" && strings.HasSuffix(strings.ToLower(executable), ".app") {
		return errors.New("macOS 程序入口必须指向应用包内的可执行文件")
	}
	return nil
}

func (adapter nativeAdapter) Install(_ context.Context, release ReleasePointer) error {
	return adapter.Validate(release)
}

func (adapter nativeAdapter) Launch(ctx context.Context, request LaunchRequest) (*exec.Cmd, error) {
	if err := adapter.Validate(request.Release); err != nil {
		return nil, err
	}
	executable, err := releaseExecutable(request.Release)
	if err != nil {
		return nil, err
	}
	command := exec.CommandContext(ctx, executable, request.Args...)
	command.Dir = request.Release.Path
	command.Env = request.Env
	if err := command.Start(); err != nil {
		return nil, fmt.Errorf("启动当前版本失败: %w", err)
	}
	return command, nil
}

func (androidAdapter) Platform() string {
	return "android"
}

func (androidAdapter) Validate(release ReleasePointer) error {
	if strings.TrimSpace(release.Path) == "" {
		return errors.New("Android 更新版本路径不能为空")
	}
	return nil
}

func (adapter androidAdapter) Install(_ context.Context, release ReleasePointer) error {
	if err := adapter.Validate(release); err != nil {
		return err
	}
	return ErrPlatformInstallRequired
}

func (androidAdapter) Launch(_ context.Context, _ LaunchRequest) (*exec.Cmd, error) {
	return nil, errors.New("Android 不能由 Go 更新器直接启动，请由宿主应用通过系统组件启动")
}

func releaseExecutable(release ReleasePointer) (string, error) {
	if strings.TrimSpace(release.Path) == "" {
		return "", errors.New("版本路径不能为空")
	}
	if strings.TrimSpace(release.Entrypoint) == "" {
		return "", errors.New("程序入口不能为空")
	}
	root, err := filepath.Abs(release.Path)
	if err != nil {
		return "", fmt.Errorf("解析版本路径失败: %w", err)
	}
	return safeEntrypoint(root, release.Entrypoint)
}