// Package anime_nsfw 负责"动漫色情图片识别"：本机 Python + WD Tagger v3 (eva02-large) 起一个本地 HTTP 服务，
// Go 侧把图片路径发给它，拿到"是否色情"和最高敏感分。
//
// 大白话理解：WD Tagger v3 是 Danbooru 风格的图片标签模型，能输出 rating 分类：
//   - general：安全
//   - sensitive：轻微敏感
//   - questionable：可疑
//   - explicit：明确色情
//
// 我们只关心 questionable 和 explicit 的分数，任一 >= 阈值就判定为色情。
//
// 机器上没有 python 或没装 onnxruntime/opencv 时，Start 会报错，调用方跳过识别、
// 走默认整理流程——这个功能是纯附加的，不影响其它步骤。
package anime_nsfw

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"time"

	_ "embed"
)

//go:embed server.py
var serverScript []byte

// detectorStartTimeout 等待 python 服务就绪（模型加载）的超时时间。
// WD Tagger v3 模型约 1.26GB，加载需要时间，给足余量。
const detectorStartTimeout = 300 * time.Second

// requestTimeout 单张图片检测的超时时间。
const requestTimeout = 60 * time.Second

// Detector 封装一个本地 python 服务的客户端。
type Detector struct {
	url       string
	threshold float64
	client    *http.Client
	cmd       *exec.Cmd
	scriptDir string
	python    string
	modelDir  string
	mu        sync.Mutex
	stopped   bool
	cancel    context.CancelFunc
	done      chan struct{}
	restartMu sync.Mutex
}

// Start 拉起本地 python 检测服务并等它就绪。
func Start(pythonPath string, threshold float64) (*Detector, error) {
	if threshold <= 0 || threshold >= 1 {
		threshold = 0.5
	}
	py := resolvePython(pythonPath)
	if py == "" {
		return nil, fmt.Errorf("未找到 python，动漫敏感识别不可用")
	}

	tmpDir, err := os.MkdirTemp("", "kmp-anime-nsfw-*")
	if err != nil {
		return nil, fmt.Errorf("创建临时目录失败: %v", err)
	}
	scriptPath := filepath.Join(tmpDir, "server.py")
	if err := os.WriteFile(scriptPath, serverScript, 0644); err != nil {
		_ = os.RemoveAll(tmpDir)
		return nil, fmt.Errorf("写入检测脚本失败: %v", err)
	}

	modelDir := ""
	if wd, err := os.Getwd(); err == nil {
		modelDir = filepath.Join(wd, "lib")
	}

	d := &Detector{
		threshold: threshold,
		client:    &http.Client{Timeout: requestTimeout},
		python:    py,
		modelDir:  modelDir,
		scriptDir: tmpDir,
	}

	if err := d.launch(); err != nil {
		_ = os.RemoveAll(tmpDir)
		return nil, err
	}
	return d, nil
}

func (d *Detector) launch() error {
	d.teardown()

	port, err := freePort()
	if err != nil {
		return fmt.Errorf("找空闲端口失败: %v", err)
	}

	ctx, cancel := context.WithCancel(context.Background())
	cmd := exec.CommandContext(ctx, d.python, filepath.Join(d.scriptDir, "server.py"), fmt.Sprintf("%d", port), d.modelDir)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stdout
	if err := cmd.Start(); err != nil {
		cancel()
		return fmt.Errorf("启动动漫检测服务失败: %v", err)
	}

	done := make(chan struct{})
	d.url = fmt.Sprintf("http://127.0.0.1:%d", port)
	d.cmd = cmd
	d.cancel = cancel
	d.done = done
	go func() {
		_ = cmd.Wait()
		close(done)
	}()

	if err := d.waitReady(); err != nil {
		d.teardown()
		return err
	}
	return nil
}

func (d *Detector) teardown() {
	if d.cancel != nil {
		d.cancel()
		d.cancel = nil
	}
	if d.cmd != nil && d.cmd.Process != nil {
		_ = d.cmd.Process.Kill()
	}
	if d.done != nil {
		select {
		case <-d.done:
		case <-time.After(3 * time.Second):
		}
		d.done = nil
	}
	d.cmd = nil
}

func (d *Detector) waitReady() error {
	deadline := time.Now().Add(detectorStartTimeout)
	for time.Now().Before(deadline) {
		select {
		case <-d.done:
			return fmt.Errorf("动漫检测服务提前退出，请确认已安装 onnxruntime/opencv (pip install onnxruntime opencv-python numpy)")
		default:
		}
		req, err := http.NewRequest(http.MethodGet, d.url+"/health", nil)
		if err != nil {
			return err
		}
		resp, err := d.client.Do(req)
		if err == nil {
			_, _ = io.Copy(io.Discard, resp.Body)
			resp.Body.Close()
			if resp.StatusCode == http.StatusOK {
				return nil
			}
		}
		time.Sleep(500 * time.Millisecond)
	}
	return fmt.Errorf("动漫检测服务在 %v 内未就绪", detectorStartTimeout)
}

// AnimeRatings WD Tagger 的四个 rating 评分。
type AnimeRatings struct {
	General      float64 `json:"general"`
	Sensitive    float64 `json:"sensitive"`
	Questionable float64 `json:"questionable"`
	Explicit     float64 `json:"explicit"`
}

// Detect 检测一张动漫图片是否色情。返回：
//   - score：max(explicit, questionable) 的 sigmoid 分数（若 G 最高则为 0）
//   - nsfw：是否判定为色情（分数 >= 阈值）
//   - ratings：四个 rating 的原始分数
//   - err：检测失败
func (d *Detector) Detect(path string) (score float64, nsfw bool, ratings AnimeRatings, err error) {
	score, nsfw, ratings, err = d.detectOnce(path)
	if err == nil {
		return score, nsfw, ratings, nil
	}
	var ce *connError
	if !errors.As(err, &ce) {
		return score, nsfw, ratings, err
	}

	d.restartMu.Lock()
	defer d.restartMu.Unlock()

	if d.isStopped() {
		return 0, false, ratings, err
	}
	if d.healthy() {
		return d.detectOnce(path)
	}
	fmt.Printf("=== 动漫检测服务失联(%v), 正在重启…\n", ce.err)
	if rerr := d.launch(); rerr != nil {
		return 0, false, ratings, fmt.Errorf("动漫检测服务重启失败: %v", rerr)
	}
	fmt.Println("=== 动漫检测服务已重启，继续识别")
	return d.detectOnce(path)
}

func (d *Detector) healthy() bool {
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, d.url+"/health", nil)
	if err != nil {
		return false
	}
	resp, err := d.client.Do(req)
	if err != nil {
		return false
	}
	defer resp.Body.Close()
	return resp.StatusCode == http.StatusOK
}

func (d *Detector) isStopped() bool {
	d.mu.Lock()
	defer d.mu.Unlock()
	return d.stopped
}

func (d *Detector) detectOnce(path string) (score float64, nsfw bool, ratings AnimeRatings, err error) {
	body, _ := json.Marshal(map[string]interface{}{
		"path":      path,
		"threshold": d.threshold,
	})
	resp, err := d.client.Post(d.url+"/detect", "application/json", bytes.NewReader(body))
	if err != nil {
		return 0, false, ratings, &connError{err}
	}
	defer resp.Body.Close()
	data, err := io.ReadAll(resp.Body)
	if err != nil {
		return 0, false, ratings, err
	}
	var out struct {
		Ok      bool    `json:"ok"`
		Error   string  `json:"error"`
		Nsfw    bool    `json:"nsfw"`
		Score   float64 `json:"score"`
		Ratings struct {
			General       float64 `json:"general"`
			Sensitive     float64 `json:"sensitive"`
			Questionable  float64 `json:"questionable"`
			Explicit      float64 `json:"explicit"`
		} `json:"ratings"`
		TopTags []map[string]interface{} `json:"top_tags"`
	}
	if err := json.Unmarshal(data, &out); err != nil {
		return 0, false, ratings, fmt.Errorf("解析检测结果失败: %v", err)
	}
	if !out.Ok {
		return 0, false, ratings, fmt.Errorf("检测服务返回错误: %s", out.Error)
	}
	ratings = AnimeRatings{
		General:      out.Ratings.General,
		Sensitive:    out.Ratings.Sensitive,
		Questionable: out.Ratings.Questionable,
		Explicit:     out.Ratings.Explicit,
	}
	// 打印 rating 详情（调试用）
	fmt.Printf("=== AnimeNSFW 检测详情 %s: [G=%.3f S=%.3f Q=%.3f E=%.3f]\n",
		path, ratings.General, ratings.Sensitive, ratings.Questionable, ratings.Explicit)
	return out.Score, out.Nsfw, ratings, nil
}

type connError struct{ err error }

func (e *connError) Error() string { return e.err.Error() }
func (e *connError) Unwrap() error { return e.err }

func (d *Detector) Stop() {
	d.mu.Lock()
	defer d.mu.Unlock()
	if d.stopped {
		return
	}
	d.stopped = true
	d.teardown()
	if d.scriptDir != "" {
		_ = os.RemoveAll(d.scriptDir)
	}
}

func (d *Detector) Threshold() float64 {
	return d.threshold
}

func resolvePython(configured string) string {
	candidates := []string{}
	if strings.TrimSpace(configured) != "" {
		candidates = append(candidates, strings.TrimSpace(configured))
	}
	if v := os.Getenv("KM_NSFW_PYTHON"); v != "" {
		candidates = append(candidates, v)
	}
	candidates = append(candidates, "python", "python3", "py")
	for _, c := range candidates {
		if p, err := exec.LookPath(c); err == nil {
			return p
		}
		if strings.ContainsAny(c, `\/`) {
			if _, err := os.Stat(c); err == nil {
				return c
			}
		}
	}
	return ""
}

func freePort() (int, error) {
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return 0, err
	}
	defer ln.Close()
	return ln.Addr().(*net.TCPAddr).Port, nil
}