// migrate-base64-images 将 chapters 表中 content 内的 base64 图片提取为文件并替换为 URL
// 用法：cd soul-api && go run ./cmd/migrate-base64-images [--dry-run]
// 测试环境：APP_ENV=development 时加载 .env.development，请先在测试库验证
package main

import (
	"encoding/base64"
	"flag"
	"fmt"
	"log"
	"math/rand"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	"soul-api/internal/config"
	"soul-api/internal/database"
	"soul-api/internal/model"
)

// data:image/png;base64,iVBORw0KG... 或 data:image/jpeg;base64,/9j/4AAQ...
var base64ImgRe = regexp.MustCompile(`(?i)src=["'](data:image/([^;"']+);base64,([A-Za-z0-9+/=]+))["']`)

func main() {
	dryRun := flag.Bool("dry-run", false, "仅统计和预览，不写入文件与数据库")
	flag.Parse()

	cfg, err := config.Load()
	if err != nil {
		log.Fatal("load config: ", err)
	}
	config.SetCurrent(cfg)
	if err := database.Init(cfg.DBDSN); err != nil {
		log.Fatal("database: ", err)
	}

	uploadDir := cfg.UploadDir
	if uploadDir == "" {
		uploadDir = "uploads"
	}
	bookImagesDir := filepath.Join(uploadDir, "book-images")
	if !*dryRun {
		if err := os.MkdirAll(bookImagesDir, 0755); err != nil {
			log.Fatal("mkdir book-images: ", err)
		}
	}

	db := database.DB()
	var chapters []model.Chapter
	if err := db.Select("id", "mid", "section_title", "content").Where("content LIKE ?", "%data:image%").Find(&chapters).Error; err != nil {
		log.Fatal("query chapters: ", err)
	}

	log.Printf("找到 %d 篇含 base64 图片的章节", len(chapters))
	if len(chapters) == 0 {
		return
	}

	rand.Seed(time.Now().UnixNano())
	const letters = "abcdefghijklmnopqrstuvwxyz0123456789"
	randomStr := func(n int) string {
		b := make([]byte, n)
		for i := range b {
			b[i] = letters[rand.Intn(len(letters))]
		}
		return string(b)
	}

	mimeToExt := map[string]string{
		"png":  ".png",
		"jpeg": ".jpg",
		"jpg":  ".jpg",
		"gif":  ".gif",
		"webp": ".webp",
	}

	totalReplaced := 0
	totalFiles := 0
	for _, ch := range chapters {
		matches := base64ImgRe.FindAllStringSubmatch(ch.Content, -1)
		if len(matches) == 0 {
			continue
		}
		newContent := ch.Content
		for _, m := range matches {
			fullDataURL := m[1]
			mime := strings.ToLower(strings.TrimSpace(m[2]))
			b64 := m[3]
			ext := mimeToExt[mime]
			if ext == "" {
				ext = ".png"
			}

			decoded, err := base64.StdEncoding.DecodeString(b64)
			if err != nil {
				log.Printf("  [%s] base64 解码失败: %v", ch.ID, err)
				continue
			}

			name := fmt.Sprintf("%d_%s%s", time.Now().UnixNano(), randomStr(6), ext)
			dst := filepath.Join(bookImagesDir, name)
			url := "/uploads/" + filepath.ToSlash(filepath.Join("book-images", name))

			if !*dryRun {
				if err := os.WriteFile(dst, decoded, 0644); err != nil {
					log.Printf("  [%s] 写入文件失败 %s: %v", ch.ID, name, err)
					continue
				}
			}

			oldSrc := `src="` + fullDataURL + `"`
			newSrc := `src="` + url + `"`
			if strings.Contains(newContent, oldSrc) {
				newContent = strings.Replace(newContent, oldSrc, newSrc, 1)
			} else {
				oldSrc2 := `src='` + fullDataURL + `'`
				newSrc2 := `src="` + url + `"`
				newContent = strings.Replace(newContent, oldSrc2, newSrc2, 1)
			}
			totalFiles++
			log.Printf("  [%s] %s -> %s (%d bytes)", ch.ID, mime, name, len(decoded))
		}

		if newContent != ch.Content {
			totalReplaced++
			oldLen := len(ch.Content)
			newLen := len(newContent)
			if !*dryRun {
				if err := db.Model(&model.Chapter{}).Where("id = ?", ch.ID).Update("content", newContent).Error; err != nil {
					log.Printf("  [%s] 更新数据库失败: %v", ch.ID, err)
					continue
				}
			}
			log.Printf("  [%s] 已更新，content 长度 %d -> %d (减少 %d)", ch.ID, oldLen, newLen, oldLen-newLen)
		}
	}

	if *dryRun {
		log.Printf("[dry-run] 将处理 %d 篇章节，共 %d 张 base64 图片", totalReplaced, totalFiles)
		log.Printf("[dry-run] 去掉 --dry-run 后执行以实际写入")
	} else {
		log.Printf("完成：更新 %d 篇章节，提取 %d 张图片到 uploads/book-images/", totalReplaced, totalFiles)
	}
}