fanqie-go/internal/fqapi/manga_fallback.go

package fqapi

import (
	"encoding/json"
	"fmt"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"fanqie/internal/common"
)

// 漫画免签名兜底（对齐书源 20261012 的 wkbrowser 路线）：
// 设备池签名路线全部失败时，直接从 m.wkbrowser.com 取章节图片，
// 无需注册设备/签名/解密，返回原图直链。

var (
	mangaFallbackItemIDRe = regexp.MustCompile(`^\d+$`)
	trailingNumberRe      = regexp.MustCompile(`(\d+)$`)
)

const mangaFallbackOrigin = "https://p6-novel.byteimg.com/origin/"

// fetchMangaFallback 免签名获取漫画章节图片（wkbrowser 原图直链）
func fetchMangaFallback(itemID string, showHTML bool) (interface{}, error) {
	if !mangaFallbackItemIDRe.MatchString(itemID) {
		return nil, fmt.Errorf("无效的 item_id: %s", itemID)
	}

	client := common.NewHTTPClient()
	resp, err := client.Get("https://m.wkbrowser.com/i"+itemID+"/info/v2/", map[string]string{
		"User-Agent": "Mozilla/5.0 (Linux; Android 14) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0 Mobile Safari/537.36",
		"Accept":     "application/json, text/plain, */*",
	})
	if err != nil {
		return nil, fmt.Errorf("wkbrowser 请求失败: %w", err)
	}

	var body map[string]interface{}
	if err := json.Unmarshal(resp.Content, &body); err != nil {
		return nil, fmt.Errorf("wkbrowser 响应解析失败: %w", err)
	}
	data, _ := body["data"].(map[string]interface{})
	if data == nil {
		return nil, fmt.Errorf("wkbrowser 响应缺少 data（code=%v）", body["code"])
	}

	// content 为 JSON 字符串或对象，内含 materials/skeleton 图片清单
	payload := data["content"]
	if s, ok := payload.(string); ok {
		var p map[string]interface{}
		if err := json.Unmarshal([]byte(s), &p); err != nil {
			return nil, fmt.Errorf("wkbrowser 图片内容解析失败: %w", err)
		}
		payload = p
	}

	uris := collectMangaFallbackURIs(payload)
	if len(uris) == 0 {
		return nil, fmt.Errorf("wkbrowser 未找到图片")
	}

	images := make([]ImageResult, len(uris))
	for i, u := range uris {
		images[i] = ImageResult{Data: u, Format: "unknown", Index: i}
	}

	if showHTML {
		var b strings.Builder
		for _, img := range images {
			fmt.Fprintf(&b, "<img src=\"%s\">\n", img.Data)
		}
		return map[string]interface{}{"content": b.String(), "source": "wkbrowser"}, nil
	}
	return map[string]interface{}{"images": images, "source": "wkbrowser"}, nil
}

// collectMangaFallbackURIs 按书源三段策略收集图片链接（保证页序）：
// 1) skeleton.data 顺序引用 materials 的 key
// 2) materials key 按末尾数字排序
// 3) 递归遍历全树兜底（顺序不保证，仅防白屏）
func collectMangaFallbackURIs(payload interface{}) []string {
	p, _ := payload.(map[string]interface{})
	if p == nil {
		return nil
	}

	images := make([]string, 0, 32)
	seen := map[string]bool{}
	push := func(uri string) {
		src := mangaFallbackImageURL(uri)
		if src != "" && !seen[src] {
			seen[src] = true
			images = append(images, src)
		}
	}

	materials, _ := p["materials"].(map[string]interface{})
	skeletonWrapper, _ := p["skeleton"].(map[string]interface{})
	skeleton, _ := skeletonWrapper["data"].([]interface{})

	if materials != nil && skeleton != nil {
		for _, s := range skeleton {
			node, _ := s.(map[string]interface{})
			if node == nil {
				continue
			}
			key := ""
			for _, k := range []string{"elementInfo", "key", "id"} {
				if v, _ := node[k].(string); v != "" {
					key = v
					break
				}
			}
			if m, ok := materials[key].(map[string]interface{}); ok {
				if uri := mangaFallbackNodeURI(m); uri != "" {
					push(uri)
				}
			}
		}
		if len(images) > 0 {
			return images
		}
	}

	if materials != nil {
		keys := make([]string, 0, len(materials))
		for k := range materials {
			keys = append(keys, k)
		}
		sort.Slice(keys, func(i, j int) bool {
			return trailingNumber(keys[i]) < trailingNumber(keys[j])
		})
		for _, k := range keys {
			if m, ok := materials[k].(map[string]interface{}); ok {
				if uri := mangaFallbackNodeURI(m); uri != "" {
					push(uri)
				}
			}
		}
		if len(images) > 0 {
			return images
		}
	}

	var walk func(node interface{})
	walk = func(node interface{}) {
		switch t := node.(type) {
		case []interface{}:
			for _, item := range t {
				walk(item)
			}
		case map[string]interface{}:
			if uri := mangaFallbackNodeURI(t); uri != "" {
				push(uri)
				return
			}
			for _, v := range t {
				switch v.(type) {
				case map[string]interface{}, []interface{}:
					walk(v)
				}
			}
		}
	}
	walk(p)
	return images
}

// mangaFallbackNodeURI 从 materials 节点取图片资源（web_uri 优先，其次 novel-pic/md5）
func mangaFallbackNodeURI(node map[string]interface{}) string {
	if d, ok := node["data"].(map[string]interface{}); ok {
		if u, _ := d["web_uri"].(string); u != "" {
			return u
		}
	}
	if u, _ := node["web_uri"].(string); u != "" {
		return u
	}
	if d, ok := node["data"].(map[string]interface{}); ok {
		if md5, _ := d["md5"].(string); md5 != "" {
			return "novel-pic/" + md5
		}
	}
	return ""
}

// mangaFallbackImageURL web_uri 转可访问的原图直链
func mangaFallbackImageURL(uri string) string {
	u := strings.TrimPrefix(uri, "/")
	if u == "" {
		return ""
	}
	if strings.HasPrefix(u, "http://") {
		return "https://" + strings.TrimPrefix(u, "http://")
	}
	if strings.HasPrefix(u, "https://") {
		return u
	}
	return mangaFallbackOrigin + u
}

// trailingNumber 取字符串末尾数字（materials key 排序用），无数字排最后
func trailingNumber(s string) int {
	m := trailingNumberRe.FindStringSubmatch(s)
	if m == nil {
		return 1 << 30
	}
	n, _ := strconv.Atoi(m[1])
	return n
}