package config

import (
	"fmt"
	"os"
	"path/filepath"
	"sync"

	"douyu_go/internal/constants"
	"douyu_go/internal/types"
)

const maxInstanceSlots = 256

// InstanceLease 代表当前进程持有的实例槽位；必须在程序退出时释放。
type InstanceLease struct {
	paths       types.AppPaths
	name        string
	lock        instanceLock
	releaseOnce sync.Once
}

// AcquireInstancePaths 按顺序占用空闲实例。第一个进程使用默认实例，
// 后续进程分别使用实例 2、实例 3，以隔离账号、配置与运行数据。
func AcquireInstancePaths() (*InstanceLease, error) {
	baseDir := defaultDataDir()
	instanceRoot := filepath.Join(baseDir, "instances")
	lockDir := filepath.Join(instanceRoot, ".locks")
	if err := osMkdirAll(lockDir); err != nil {
		return nil, fmt.Errorf("创建实例锁目录失败: %w", err)
	}

	for slot := 1; slot <= maxInstanceSlots; slot++ {
		lock, acquired, err := tryAcquireInstanceLock(filepath.Join(lockDir, instanceLockFileName(slot)))
		if err != nil {
			return nil, fmt.Errorf("锁定%s失败: %w", instanceName(slot), err)
		}
		if !acquired {
			continue
		}

		dataDir := baseDir
		if slot > 1 {
			dataDir = filepath.Join(instanceRoot, fmt.Sprintf("instance-%d", slot))
		}
		paths := appPathsForDataDir(dataDir, slot == 1)
		if slot > 1 && isWailsDev() && os.Getenv("DOUYU_LOG_DIR") == "" {
			paths.LogDir = resolvePath(filepath.Join(constants.DefaultLogDir, "instances", fmt.Sprintf("instance-%d", slot)))
		}
		return &InstanceLease{
			paths: paths,
			name:  instanceName(slot),
			lock:  lock,
		}, nil
	}
	return nil, fmt.Errorf("最多支持同时运行 %d 个实例", maxInstanceSlots)
}

// Paths 返回当前实例独立的数据路径。
func (l *InstanceLease) Paths() types.AppPaths {
	if l == nil {
		return types.AppPaths{}
	}
	return l.paths
}

// Name 返回面向用户的实例名称。
func (l *InstanceLease) Name() string {
	if l == nil {
		return ""
	}
	return l.name
}

// Release 释放实例锁，允许新启动的程序复用该实例。
func (l *InstanceLease) Release() {
	if l == nil || l.lock == nil {
		return
	}
	l.releaseOnce.Do(func() {
		_ = l.lock.Close()
	})
}

func instanceName(slot int) string {
	if slot <= 1 {
		return "默认实例"
	}
	return fmt.Sprintf("实例 %d", slot)
}

func instanceLockFileName(slot int) string {
	if slot <= 1 {
		return "default.lock"
	}
	return fmt.Sprintf("instance-%d.lock", slot)
}